Abstract:
A testing method and apparatus for ground liquefaction and dynamic characteristics in the original position utilizing a boring hole, wherein the dynamic strength and deformation characteristics of a soil layer against a dynamic repetitive load, in an optional position in the ground can be obtained by a simple method. A measuring cell based on a three-chamber construction is used, and upper and lower soil layers (J 1 , J 3 ) with an intermediate soil layer (J 2 ) therebetween are alternately subjected to a dynamic repetitive load, and what influence there is on the intermediate soil layer (J 2 ) is investigated from the relation between pressure and displacement.

Description:
FIELD OF THE INVENTION 
   This invention relates to the testing method and apparatus, which are intended to evaluate in-situ the liquefaction and dynamic (strength and deformation) properties of soils using boreholes. Herein, the liquefaction and dynamic properties of soils correspond to those under dynamic cyclic loading such as earthquake loading, traffic loading and machinery vibrations. 
   BACKGROUND OF THE INVENTION 
   In the conventional in-situ testing method, a small-diameter bore-hole was produced down to a certain depth from the ground surface, and a cylindrically shaped zonde (inflatable membrane) was lowered down into the bore-hole. The zonde was then inflated and applied the lateral pressure to the surrounding circular wall of the soil deposit, based on the measurements of lateral pressure and radial displacement, the static strength and deformation properties of the soil deposit were inferred. 
   However, the conventional testing method was intended only to infer the static properties of the soil deposit, and the evaluation of the dynamic properties of the soil deposit, such as those under earthquake loading, traffic loading and machinery vibrations, was out of scope for its use. In the event of earthquakes, however, the strains gradually accumulate locally within the soil deposit leading in some cases to failures, due to the external forces associated with earthquakes, which might be even lower than the collapse loads. It is extremely important therefore to explore the in-situ dynamic properties of soils. The seismic excitations involve complex characteristics and it has not reached a point where the evaluation of the dynamic properties of soils under such complex seismic excitations is properly established. 
   Among the conventional assessments of liquefaction occurrence, the overall characteristics of the entire ground against liquefaction were examined in some cases. In other cases, the empiricism was used based on past case studies of whether the soil deposit at a particular condition was subjected to liquefaction during past earthquakes or not. In any case, the conventional assessment of liquefaction occurrence was not based on the dynamic properties of the soil deposit itself concerned. 
   In the current method of evaluating the dynamic properties of a soil deposit under dynamic cyclic loading, undisturbed sampling from a bore-hole and laboratory triaxial tests on undisturbed samples are required. However, it is extremely difficult to perform soil sampling in an undisturbed manner while preserving soil structures in natural deposits during sampling. It is also noteworthy that soil sampling accompanies the stress relief against the overburden stress, since the soil samples are retrieved from the deep soil deposit to the ground surface. It is therefore difficult to precisely evaluate the in-situ properties of the soil deposit in laboratory tests. 
   In addition, the undisturbed sampling methods for loose sand deposits, gravel-containing soil deposits, soil deposits involving large-sized grains such as sandy gravels, weathered rocks and soft rocks are not well established, and hence it is not practically possible to perform laboratory tests on such soil deposits. 
   In the current state of practice, it is therefore found that the range of soils that can be supplied to laboratory tests is extremely limited. 
   SUMMARY OF THE INVENTION 
   Considering the importance of evaluating in-situ the dynamic properties of the soil deposits, the present invention is intended to offer the comprehensive in-situ testing method and apparatus, which are aimed at exploring the liquefaction and dynamic (strength and deformation) properties of soils using bore-holes, however without difficult undisturbed soil sampling and associated laboratory tests. 
   In order to achieve the above objectives, the present in-situ testing method is characterized by dynamically excited cyclic loading on the bore-hole wall and monitoring of the lateral pressure and displacement of the bore-hole wall, from which the liquefaction dynamic properties of soils are inferred. 
   Herein, the dynamically excited cyclic loading constitutes the whole cycles of periodically fluctuating loading, including the wide range of relatively high-frequency loading to low-frequency loading which can be manually operated. 
   The dynamic properties of soils correspond to those that can be inferred from the relation between the amplitude of the pressure and its associated displacement during dynamically excited cyclic loading, including the yield strength, failure strength, stiffness or shear modulus, and deformation-related properties derived from the pressure amplitude, number of cycles and displacement. The overall dynamic properties of the soil deposit can be evaluated based on those individual dynamic properties of soils. 
   It is especially effective and found useful to excite laterally the cylindrical wall of a bore-hole in a manner so that the cycles of compressive loading is alternately applied onto the bore-hole wall at multiple locations with depth. By applying the pressures in this manner, it enables us to produce a central region surrounded by the two pressurized regions in a soil deposit, at which the cyclic shear stress parallel to the bore-hole axis acts. 
   It is at this central region that the soil deposit most approaches a collapse state, and the degree of approaching a collapse state can be estimated based on the static monotonic loading tests on this central region. 
   More importantly the dynamic properties of soil can be estimated based on the relations among the amplitude of the cyclic pressure, number of cycles and associated displacements during cyclic loading implemented at one or multiple locations with depth. 
   The cyclic loading is herein represented by the combination of one or more types of loading chosen from compressive loading acting towards the radial direction, torsional loading acting around the bore-hole axis and shear loading acting towards the bore-hole axis. 
   The in-situ testing apparatus in the present invention is composed of the inflatable membrane zonde which are lowered down into a bore-hole and apply the pressures onto a bore-hole wall via a liquid medium in the zonde, a control unit which can pressurize the liquid medium in the zonde and fluctuate periodically the amplitudes of the pressures in the zonde, and a device which implements the measurement of the displacements of the bore-hole wall. 
   The zonde is composed of multiple cells located at different positions along the depth, and each cell can be cyclically excited in a manner independent to each other by the control unit. By orchestrating the cycles of the pressures in the multiple cells, it is possible to excite cyclically the bore-hole wall alternately at different positions along the depth. 
   The control unit applies the cyclic pressures at the top and bottom cells, and applies the constant pressure at the central cell. 
   The zonde is equipped with a device which generates the torsional cyclic loading around the bore-hole axis while the cells are kept in contact with the bore-hole wall, and also a device which monitors the rotational displacement of the bore-hole wall during torsional cyclic loading. 
   The zonde is equipped with a device which generates the cyclic shear loading parallel to the bore-hole axis while the cells are kept in contact with the bore-hole wall, and also a device which monitors the shear displacement of the bore-hole wall during cyclic shear loading. 
   The zonde is composed of multiple cells. The top and bottom cells are those which alternately excite the bore-hole wall cyclically, and the central cell applies the static pressure onto the bore-hole wall. In addition to these three cells, there are two guard cells located above the top cell and beneath the bottom cell, which apply the static pressures. 
   The zonde is equipped with a device which monitors the pore water pressure at the central cell. 
   The device for monitoring the pore water pressure possesses a sensor unit on the surface of the inflatable membrane of the central cell. 
   The zonde is composed of multiple cells, which can be assembled in a manner exchangeable to one another. 
   Each cell in the zonde is preferably composed of a cell body itself cylindrical inflatable membrane attached to the outer circumference of the cell and a pressure room located between the cell body and the membrane into which a liquid medium is filled. 
   Seal plates are preferably inserted in between the cells in the zonde, so that the membranes of the adjacent cells can be intimately connected with each other to maintain water-tightness. 
   The control unit for pressuring the liquid medium in each cell in the zonde is composed of a cylinder which pressurizes the liquid medium and a device which monitors the amplitude (stroke) of the movement of the rod of the cylinder, from which the lateral displacement of the bore-hole wall is obtained. 
   As described above, the testing method and apparatus in the present invention enable us to perform in-situ testing on natural soil deposits without sampling of soils deep in the deposits, and to evaluate therefore the dynamic properties of natural soil deposits. 
   This testing method and apparatus can be used to a wide range of soil types, including loose sand deposits and gravel-containing soil deposits which are difficult to perform soil sampling, and also soil deposits involving large-sized grains such as sandy gravels, weathered rocks and soft rocks. 
   This testing method is also time and cost-saving in comparison to the conventional soil sampling. 
   This testing apparatus can perform a variety of tests by applying the cyclic pressures alternately to multiple locations along the depth of a bore-hole wall. These kinds of tests are supposed to produce soil elements in the deposit which are either suspected to cyclic compressional stress or subjected to cyclic shear stress at the periphery of the cells. Since soil liquefaction during earthquakes is effectively induced by the action of cyclic shear stress on the soil deposit, this testing method and apparatus are considered useful in the assessment of liquefaction occurrence. When the soil element located at the periphery of the cells is subjected to collapse due to liquefaction, the liquefaction propagates into the region of the soil deposit subjected to compressional stress leading to a rapid change in the displacements of the bore-hole wall. 
   Another testing method is to perform cyclic loading tests by using only one of the cells in the zonde. From this kind of tests, it is also possible to examine a variety of properties of the soil deposits. In such cases, the cyclic loading can be conducted by the combination of one or more types of loading chosen from compressive loading acting towards the radial direction, torsional loading acting around the bore-hole axis and shear loading acting towards the bore-hole axis. 
   Since there are two guard cells located above the top cell and beneath the bottom cell, the pressure-displacement relations can also be monitored at these two guard cells. By analyzing these data monitored at the two guard cells in comparison to the data obtained at the central cell, the soil properties can also be examined. In addition, the two guard cells assist in producing a stable condition to perform cyclic loading at the top and bottom cells. 
   In this testing apparatus which installs the device for pore water pressure measurement at the central cell, it is possible to monitor the change in the pore water pressure at the central cell, which is affected by the cyclic loading imposed on the top and bottom cells adjacent to the central cell. 
   It is possible to monitor the change in the pore water pressure at the central cell in a direct manner, by installing a sensor unit on the surface of the inflatable membrane of the central cell. 
   Since the zonde is composed of multiple cells which can be assembled in a manner exchangeable to one another, it is possible to implement maintenance of the zonde such as replacement of parts, on a cell-unit basis. 
   Since each cell in the zonde is composed of a cell body itself cylindrical inflatable membrane attached to the outer circumference of the cell and a pressure room located between the cell body and the membrane into which a liquid medium is filled, it is possible to implement maintenance of the membrane without difficulty. 
   This testing apparatus can improve the water-tightness between the membranes of the adjacent cells by inserting the seal plates inserted in between the cells in the zonde. The control unit for pressuring the liquid medium in each cell in the zonde is composed of a cylinder which pressurizes the liquid medium and a device which monitors the amplitude (stroke) of the movement of the rod of the cylinder, from which the lateral displacement of the bore-hole wall is obtained. The water level gauge can be used together to monitor the lateral displacement of the bore-hole wall. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  (A) shows the general layout of the in-situ testing apparatus for liquefaction and dynamic properties of soils using bore-holes, associated with the working example 1. 
       FIG. 1  (B) shows the general layout of the controlling unit. 
       FIG. 2  (A) shows an example of output from the pressure valve shown in  FIG. 1 . 
       FIG. 2  (B) shows an example of typical diagrams illustrating the pressure-displacement relation obtained from the test results using the testing apparatus shown in  FIG. 1 . 
       FIG. 3  shows other associated diagrams of the test results using the testing apparatus shown in  FIG. 1 . 
       FIGS. 4  (A) to (E) show the testing method using the in-situ testing apparatus for liquefaction and dynamic properties of soils using bore-holes, associated with the working example 2. 
       FIG. 5  shows the functions of the membrane zonde shown in  FIG. 4 . 
       FIG. 6  shows the general layout of the membrane zonde shown in  FIG. 5 . 
       FIG. 7  shows the general layout of the in-situ testing apparatus for liquefaction and dynamic properties of soils using bore-holes, associated with the working example 2. 
       FIGS. 8  (A) to (F) show examples of diagrams illustrating the static test results conducted on the central soil layer. 
       FIG. 9  shows the functions of the monitoring cell of the testing apparatus for liquefaction and dynamic properties of soils using bore-holes, associated with the working example 3. 
       FIG. 10  shows the structural components of the monitoring cell shown in  FIG. 9 . The cross section and plan view of the entire cell are shown in  FIGS. 10  (A) and  10  (B), and the cross section enlarged for the connection parts is shown in  FIG. 10  (C). 
       FIG. 11  (A) shows the elevation view of the monitoring cell shown in  FIG. 10 . 
       FIG. 11  (B) shows the cross section at the water tube of the top guard cell. 
       FIG. 11  (C) shows the cross section at the water tube of the top cell. 
       FIG. 11  (D) shows the cross section showing the layout of the pore water pressure gauge. 
       FIG. 12  shows the conceptual illustration of the testing apparatus of the present invention. 
       FIG. 13  shows the general layout of the pumping units and associated connections of the testing apparatus shown in  FIG. 12 . 
       FIG. 14  shows the schematic illustration of loading against a bore-hole wall during the tests. 
       FIG. 15  shows the diagram of the test results. 
       FIG. 16  shows the extended version of the layout shown in  FIG. 13 . 
       FIG. 17  shows the conceptual illustration of the testing apparatus for the extended version of the working example 3 of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The mode of the present invention is described in detail below, using schematic examples. 
   Working Example 1 
     FIG. 1  (A) shows the schematic illustration of the testing apparatus materializing the working example 1. 
   This testing apparatus is composed of an inflatable membrane zonde  201 , which is lowered down into a bore-hole  100 , and apply the pressures onto a bore-hole wall via a liquid medium such as water  203  in the zonde  201 , a control unit which can pressurize the liquid medium such as water  203  in the zonde  201 , and fluctuate periodically the amplitudes of the pressures in the zonde  201  via a pressure regulator  205 , and a device  208  which implements the measurement of the displacements of the bore-hole wall. 
   In the working example, the water  203  is reserved in the tank  2  on the ground surface. The pressurized air is supplied to a top portion of the water tank  202  from the pressure supplying unit  204 . This pressurized air is supplied via the pressure regulator  205  to the water  203  stored in the water tank  202 . Instead of regulating the air pressure, the water pressure can be alternatively directly controlled. 
   The water tank  202  is connected to the inflatable membrane zonde  201  through the connection pipe  206 . The displacement sensor  208  monitors the water level in the water tank  202 , from which the radial displacement of the bore-hole wall is calculated. 
   Alternatively, the water level can either be read off directly from the scale attached to the tank  202 , or be monitored by the pressure sensor  265  installed at the bottom of the water tank  202 . 
   The inflatable membrane zonde  201  is fixed against the vertical direction, and can be inflated and deflated towards the radial direction. The zonde is composed of hollow cylindrical parts such as a membrane tube which is intimately attached the wall of the bore-hole  100 . 
   The pressure-supplying unit  204  is composed of a gas cylinder of pressurized nitrogen gas and a regulator maintaining the gas pressure supplied from the gas cylinder constant. Air compressors can be alternatively used instead of a gas cylinder. 
   A servo valve is used as the pressure regulator  205 . The pressure supplied through this regulator can be controlled via a voltage signal, as shown in  FIG. 1  (B). The voltage signal can be transmitted from the personal computer  207  to the valve-driving unit  51  of the regulator  205  in order to produce cyclically alternating pressures at a given frequency. The amplitude of the pressure is monitored by the sensor  252 , and is transmitted back as a feedback to the servo amplifier  253  and the signal is adjusted to make precise control of the pressure change in the system. 
   The testing procedure for this testing apparatus is described below. 
   Several base pressure levels are first set up based on the expected levels of yield strength or failure strength (Pl). At each base pressure level beginning from the lowest base level, the cyclically changing pressure is additionally applied and the displacement of the surrounding soil is monitored. The same procedure is repeated at each base pressure level, and the base pressure level is gradually increased until the collapse limit stress is achieved. The dynamic properties of soils are inferred from the pressure-displacement relations at several base pressure levels. In the working example, the sinusoidal cycles of pressures are adopted. However, any form of cycles can be applied, and it is possible to apply impact loading. 
   The frequency of the cyclic pressure and its number of cycles can be determined based on the characteristics of earthquakes concerned. However, it is preferable to set it at around 0.1 to 1 Hz. 
   In the working example, the yield strength Py, failure strength Pl and deformation modulus are inferred as representative dynamic properties of soils. 
   The testing procedure is described in detail from the practical point of view below. 
   i) Setting Up Test Series 
   The inflatable membrane zonde  201  is lowered down to a given soil layer in a bore-hole  100 . The zonde  201  is then inflated until the membrane is intimately attached to the bore-hole wall, at which point the change in the displacement stabilizes, and the level of the pressure at such point is determined as the initial stress level Po. 
   The expected level of the failure strength or limiting stress is first determined. A series of tests are supposed to be conducted at different base pressure levels. The number of tests N is decided, and the level of the base pressure at each test is determined based on the equal increment of the base pressure level, ΔP=(Pl−Po)/N. The cyclic loading is applied for n cycles or for the time period of Tn at each base pressure level. 
   The expected level of the failure strength or limiting stress can be set up arbitrarily based on the objectives of the tests. For instance, the level of the limiting stress can be set up at a high value so that the number of tests can be increased. The limiting stress corresponds to the level of the pressure below which the occurrence of soil liquefaction is less likely and can be determine based primarily on the conditions of the soil layer concerned. 
   The number of cycles and time duration of cyclic loading can be set up arbitrarily and for instance can be determined by considering the characteristics of earthquakes concerned. In the working example, 10 levels of the base pressures are set up, and the cyclic loading are applied for 20 cycles or 120 seconds at each base pressure level. Herein, the duration of 120 seconds is considered as appropriate, since the duration of earthquakes is in most cases less than 120 seconds, and it becomes time consuming if the duration becomes longer. 
   ii) 1st Base Pressure Level 
   The cyclic loading with amplitudes varying between Po and Po+α is applied for 20 cycles or 120 seconds, and the displacement is monitored during the cyclic loading. The Parameter α should take a value that does not exceed ΔP or is preferably equal to ΔP. 
   iii) kst Base Pressure Level 
   The same procedure is repeated at each base pressure level. 
   For instance, at the kst base pressure level, the level of the base pressure Pk is increased up to Po+(k−1)ΔP. The cyclic loading with amplitudes varying between Pk and Pk+α is applied for 20 cycles or 120 seconds, and the displacement is monitored during the cyclic loading. 
   The data thus obtained from the tests are translated in to a diagram as shown in  FIG. 2  (B). In this diagram, the final level of the displacement at each base pressure level is indicated as r 1 , r 2 , r 3  and so forth. 
   In the working example, the voltage outputs acquired from the pressure sensors are converted into digital data and saved in the personal computer. The data thus obtained are automatically calibrated to infer the yield strength Py, failure strength Pl and deformation modulus. The deformation modulus herein corresponds to the gradient of the initial linear portion of the pressure-displacement relation. 
   By systematically analyzing the data of the displacements increasing with the number of cycles, the strength and deformation characteristics of soil deposits can be examined. 
   In other words, it becomes possible to evaluate the possibility of liquefaction occurrence based on the comparisons with other geotechnical test results. 
   In the case of sandy soil deposits, the state of failure is expected to occur rapidly and the relation of the pressure-displacement is also expected to reach the state of failure rapidly. By examining the degree of such a rapid change leading to a failure state, it is possible to examine the level of damages induced by liquefaction. 
   In the case of clayey soil deposits, the state of failure is expected to occur rather slowly. By examining the degree of such as low change, it is possible to examine the dynamic characteristics of soils. 
   Overall, by examining the process of development of displacements leading to a failure state during cyclic loading, the degree of strength reduction can be estimated regardless of soil types. 
   iv) Important Items During Monitoring 
   Proper attention should be given to the process of development of displacements, and the point of time at which the displacements begin to rapidly increase needs to be recorded. The data acquisition might be terminated at such a point of time by interpreting it as being equivalent to a state of yielding. Otherwise, the data acquisition can be extended until the state of failure is clearly seen. 
   The pressure in the membrane zonde  201  is reduced down below Po, and the zonde is then pulled up to the ground surface proper attention is given to the resistance of soil during the lift-up of the zonde. When the lift-up of the zonde is found to be difficult, the bore-hole wall is most probably collapsed due to liquefaction induced during testing. 
   In the working example, the relation between the pressure and displacement is translated in a diagram. However, as shown in  FIGS. 3  (A) to (D), the relation between the displacement and number of cycles at each base pressure level can be translated into a diagram, and it is possible to examine the dynamic properties of soil with regard to the number of cycles. In these diagrams, the peak value of the displacement at each cycle is plotted against the number of cycles. This plot is produced at each base pressure level. It is certain that the displacements gradually accumulate during cyclic loading. It is seen that in the 1st, 2nd and 3rd cycles shown in  FIGS. 3  (A) to (C), the gradients of the displacement accumulation are the same, and the gradient becomes larger at the state of yielding, ( FIG. 3  (D)), and eventually the gradient becomes extremely large at the state of failure as shown in  FIG. 3  (E). By obtaining this kind of data, it is possible to examine the dynamic strength and deformation characteristics of soils against cyclic loading. 
   Alternatively it is possible to plot the displacements against the period of time of cyclic loading, and it is recommended to examine various types of soil properties. 
   In the working example 1, the cyclic loading acting towards the radial direction is adopted. 
   However, it is also possible to adopt other types of cyclic loading such as torsional loading acting around the bore-hole axis, and shear loading acting parallel to the bore-hole axis. 
   For instance, in the case of torsional cyclic loading, the following units need to be installed, i.e. the monitoring zonde  201  which would be intimately attached to a bore-hole wall during its operation, the driving unit  209  for torsional loading generated around the bore-hole axis, and the monitoring unit  210  for the rotational displacements of the bore-hole wall during torsional loading. 
   In the case of cyclic shear loading, the following units need to be installed, i.e. the monitoring zonde  201  which would be intimately attached to a bore-hole wall during its operation, the driving unit  211  for shear loading generated parallel to the bore-hole axis, and the monitoring unit  212  for the shear (axial) displacements of the bore-hole wall during shear loading. 
   The driving unit  209  for torsional loading and the driving unit  211  for shear loading can be made up of various types of devices. However, it is preferable to use hydraulic driving units employing the oil pressure or air pressure, and the combinations of hydraulic actuators and relevant regulators such as a servo-valve can be used. 
   Working Example 2 
   The working example 2 is described below. 
     FIG. 7  shows the general layout of the in-situ testing apparatus in the present invention, which is aimed at exploring the dynamic properties of soils using bore-holes. 
   In the working example 1 described above, the cyclic loading is employed only on one location with a single cell of the zonde. However, in the working example 2, the cyclic loading is alternatively imposed on the top and bottom parts of the soil layer, J 1  and J 3 , in such a manner that the soil element at the central part, J 2 , is subjected to cyclic shear stress. 
   Herein, the membrane zonde  110 , which is lowered down into a bore-hole  100 , is composed of three independent cells, 1st cell  111 , 2nd cell  112  and 3rd cell  113 , which are filled with a liquid medium. The 1st cell  111  and 3rd cell  113  are alternatively cyclically excited by the 1st controlling device  121  and the 3rd controlling device  123 , while the 2nd cell is statically pressurized by the 2nd controlling device  122 . 
   The membrane zonde  110  is composed of a cylindrical cell body  114  itself and a cylindrical membrane  115  which is attached to the outer circumference of the cell body as shown in  FIGS. 5 and 6 . The cylindrical membrane  115  covers all of the three cells, i.e. the 1st cell  111  and 2nd cell  112 , and 3rd cell  113 . The seal plates can be attached between the 1st cell  111  and 2nd cell  112 , and also between the 2nd cell  112  and 3rd cell  113 , or these seal plates can be attached to each cell. Various types of cell structures are possible. In what follows, the membranes for the 1st cell  111 , 2nd cell  112  and 3rd cell are called  115 A,  115 B and  115 C. The zonde is therefore composed of the 1st cell  111 , 2nd cell  112  and 3rd cell  113  and the corresponding membranes  115 A,  115 B and  115 C. 
   It is preferable to make the length of the central (2nd) cell (or membrane  115 B), L 2 , equal to about the diameter of the zonde  110 . This is because of the fact that the failure of soils adjacent the central (2nd) cell would commence earlier in the tests if the length of the 2nd cell (membrane  115 B), L 2 , is small, while the failure of soils adjacent to the central (2nd) cell would not occur if the length, L 2 , is large. 
   The length of the 1st cell  111  and 3rd cell  113  (membranes  115 A and  115 C) is better taken as 1.5 to 2.5 times the diameter of the zonde, D, and is preferably 2 times the diameter of the zonde, D. Herein, the diameter of the zonde, D, is preferably taken as 5 cm to 20 cm. However, it is not intended to limit any use of other sizes of equipments. These recommended sizes would enable the membranes  115 A and  115 C, which are attached to the 1st cell  111  and 3rd cell  113 , to inflate in a spherical manner, and also would enable the soil element J 2  located adjacent to the central cell to be subjected to cyclically alternating shear stress. 
   As shown in  FIG. 7 , the 1st and 3rd pressure controlling devices,  121  and  123 , are composed of a gas cylinder  120 A, which supplies high pressures to the system, a gas tank  120 B, which reserves an amount of gas supplied from the gas cylinder  120 A, and hydraulically operated cylinders,  121 C and  123 C, which are activated by the hydraulic pressures supplied from the gas tank  120 B. Installed between the gas tank  120 B and the cylinders of  121 C and  123 C are the valves of  121 E and  123 E, which would release the pressures, and also the valves of  121 D and  123 D, which would supply the pressures. By adjusting these valves of  121 D,  121 E,  123 D and  123 E, the 1st cell  111  and 3rd cell  113  in the zonde  110  can be cyclically excited. 
   For instance, the valves of  121 D and  123 D can be used as pressure regulators, while the valves of  121 E and  123 E are closed. By adjusting the gas pressures supplied into the cylinders of  121 C and  123 C by means of the valves of  121 D and  123 D, the 1st cell  111  and 3rd cell  113  can be activated. The valves of  121 D and  123 D are indicated in  FIG. 6  with a symbol of manual valves, however, they can be replaced by other types of valves such as electrically operated regulators. After the testing, the gas pressures in the cylinders of  121 C and  123 C should be released by opening up the valves of  121 E and  123 E. In this example, water is used as a liquid medium in the system, and the membranes  115 A and  15 C are inflated and deflated by the water pressure. 
   The hydraulically operated cylinder is not installed for the 2nd pressure controlling device. 
   Instead, the water  3  is reserved in a water tank  122 C, and the empty top portion of the water tank  122 C is pressurized by supplying the gas pressure from the gas cylinder  122 A. This gas pressure is controlled by the regulator  122 D. It is possible to use the same cylinder as those of the 1st and 3rd pressure controlling devices,  121  and  123 . 
   The cylinder  121 C and the 1st cell  111  in the zonde  110  are connected by the 1st line  131 , and the water tank  120 C and the 2nd cell are connected by the 2nd line  132 , and the cylinder  123 C and the 3rd cell  113  are connected by the 3rd line  133 . These three lines of  131 ,  132  and  133  are installed along the boring rod  140  to which the zonde is fixed. 
   The displacement sensors,  151  and  152 , are installed at the cylinders of  121 C and  123 D. 
   These displacement sensors are used for monitoring the radial displacements of the top soil layer J 1  and the bottom soil layer J 3 , which are cyclically loaded by the 1st cell  111  and 3rd cell  113 . 
   The displacements of the pistons of the cylinders thus monitored are calibrated into the radial displacements of the membranes of  115 A and  115 C in the zonde  110 , which are equivalent to the radial displacements of the bore-hole wall. 
   The displacement sensor  153  is installed to monitor the water level in the water tank  122 C, from which the radial displacement of the bore-hole wall at the soil layer J 2  adjacent to the central (2nd) cell  112  in the zonde  110  is calibrated. From the water level thus monitored, the radial displacements of the membrane  115 B attached to the 2nd cell  112 , and therefore of the bore-hole wall are obtained. Instead of using the displacement sensor  153 , the radial displacement of the bore-hole wall can either be obtained by the scale attached to the tank  122 C, or be monitored by the pressure sensor  165  installed at the bottom of the water tank  122 C. In addition, at the bottom of the membrane zonde  110  installed is the pore pressure transducer  150  for examining the occurrence of liquefaction. This pore pressure transducer  150  can be installed either at the center or at the bottom of the side wall of the membrane  115 B of the 2nd cell  112 , as shown in  FIG. 6  (A). Since there is a possibility that the pore pressure cannot be measured due to clogging at the bore-hole wall, the pore pressure transducer can be installed at the bottom surface  110 C as shown in  FIG. 6  (B). However, when the zonde  110  is lowered down into a bore-hole  100 , the remnants of soils scraped by the zonde  110  may be adhered to the bottom surface  110 C. Therefore, it is preferable to install the transducer deep in the concave part of the bottom surface  110 D. 
   The testing procedure for the working example 2 is described below, with reference to  FIG. 4 . 
   In the tests, the cyclic loading is applied to the top and bottom soil layers J 1  and J 3 , alternatively and the associated displacements are monitored on a real-time basis. The static loading is then applied to the central soil layer J 2  to derive the static strength of soils. 
   The manner in which the cyclic loading is applied to the top and bottom soil layers, J 1  and J 3 , is the same as that adopted in the working example 1. By dividing the expected level of the yield strength or limiting stress (Pl) by the number of tests N, the level of the base pressure at each test is determined. The cyclic loading whose amplitude is set at α is applied for n cycles or for the time period of Tn at each base pressure level. By monitoring the displacements r, the static strength of the central soil layer J 2  is derived at each level of the base pressure. 
   The testing procedure is described in detail from the practical point of view below. 
   The bore-hole  100  is produced down to a depth of testing, and the membrane zoned lowered down into the bore-hole  100  with a help of the boring rod  140 . The tests commence following the procedure as described below. 
   i) Setting Up Test Series 
   By supplying the pressure to the 2nd cell  112  in the zonde  110 , the static loading is applied to the central soil layer J 2  and the initial strength of the central soil layer J 2  is derived. In other words, the relation between the pressure P and the displacement r under static loading is obtained. 
   At this point of time, the initial pressure Po is obtained, which corresponds to the state at which the membrane zonde is intimately adhered to the bore-hole wall and the displacement is stabilized. 
   The expected level of the failure strength or limiting stress (Pl) is first determined. The number of tests N is decided, and the level of the base pressure at each test is determined based on the equal increment of the base pressure level, 
   ΔP=(Pl−Po)/N. The cyclic loading is applied alternatively to the 1st cell  111  and 3rd cell  113  for n cycles or for the time period of Tn at each base pressure level. Prior to the cyclic loading, the initial pressure Po is applied to the 1st cell  111  and 3rd cell  113 . 
   ii) 1st Base Pressure Level 
   The cyclic loading with amplitudes varying between P 0  and Po+α is applied alternatively to the 1st cell  111  and 3rd cell  113  for n cycles, and the displacements of the top and bottom soil layers J 1  and J 3  corresponding to the 1st cell  111  and 3rd cell  113  are monitored. The relations between the pressures and displacements are monitored on a real-time basis in a manner similar to the working example 1 and the acquired data are stored in the personal computer and are translated into a diagram. In this case, the number of tests may be taken at about N=10, and the cyclic loading may be applied for about 20 cycles or for 120 seconds. In this case, the rapidly growing impact loading is applied as shown in  FIG. 4  (E). The soil layer is steadily compressionally loaded, while the level of the loading is kept for a time period until after the impact loading stops rapid growing. The level of loading then steadily reduces. The loading is applied alternatively to the 1st cell  111  and 3rd cell  113 , in a manner that one of the cells is loaded while the other one is unloaded. The time history of loading is designed in such a manner that the level of loading begins to reduce in one of the cells, after which point of time the level of loading begins to increase in the other cell. However, these two characteristic points of time may be designed to coincide with one another, as shown in dashed lines. 
   The upper portions and lower portions of the top soil layer J 1  and the bottom soil layer J 3  are subjected to compressional as well as shear loading. Especially at the central soil layer J 2 , the cyclically alternating shear loading is applied in a manner similar to the action during earthquakes, since the cyclic loading alternatively applied on the top and bottom soil layers, J 1  and J 3 , as shown with the symbols of X in  FIGS. 4  (A) to (C). The length of the 2nd cell  112 , L 2 , is designed to be almost equal to the diameter of the membrane zonde  110 , and the phenomena leading to failure are observed adequately. 
   Since the lengths of the 1st cell and 3rd cell, L 1  and L 3 , are about twice the diameter D, the membranes  115 A and  115 C are supposed to inflate in a spherical shape, and consequently the compressional loading thus generated is distributed around the central soil layer J 2 . Therefore, the size of the equipment is designed to make effective use of effects of loading on the soil layer. 
   iii) After Cyclic Loading 
   The pressure is again supplied to the 2nd cell  112 , and the static loading is applied to the central soil layer J 2 . The strength of the soil at the central layer J 2  is thus measured, and the strength reduction is evaluated relative to the initial strength. 
   The above procedure is taken as one cycle, and the cyclic loading is repeated with the pressure increment of DB until the failure of the soil layer is observed. 
     FIG. 8  shows the example of the results of the static loading tests conducted at the central soil layer J 2 . 
   The static pressure P at the central soil layer J 2  is plotted against time in  FIG. 8  (A), and the corresponding displacement r at the central soil layer J 2  is plotted against time in  FIG. 8  (B). In  FIGS. 8  (C) to  8  (F), the relation between the pressure and the displacement at the central soil layer J 2  at each base pressure level is plotted based on the data shown in  FIGS. 8  (A) and (B). 
   As shown in  FIGS. 8  (A) and  8  (B), the initial strength of the central soil layer is measured prior to the cyclic loading. 
   The displacement steadily increases without the increase in the pressure, until the membrane  115 B of the 2nd cell  112  in the zonde  110  is intimately adhered to the bore-hole wall  100 . Once the membrane is adhered to the bore-hole wall, the pressure rapidly begins to increase with little change in the displacement, and the pressure eventually reaches the initial pressure Po with the change in the displacement stabilized. After that, the displacement is monitored during the increase in the pressure up to Po+δ, and the relation between the pressure and the displacement of the central soil layer at the initial base pressure level is produced, as shown in  FIG. 8  (C). The gradient of this pressure-displacement relation is defined as the deformation modulus. The pressure is then reduced down to Po (0). Although the pressure is reduced down to the original level of Po, the residual displacement remains at the central soil layer, and therefore the displacement would not recover completely. The pressure increment δ is determined as a half, one-third, or one-fourth of the amplitude of the cyclic loading imposed on the top and bottom soil layers, J 1  and J 3 . Herein, the least necessary is the pressure-displacement relation which can be comprehensively analyzed without difficulty. 
   The static loading is then conducted at the central soil layer J 2 , after the first cyclic loading on the top and bottom soil layers, J 1  and J 3 . 
   The displacement steadily increases without the increase in the pressure, until the membrane  115 B is inflated to the level of the residual displacement at the first base pressure level. Once the level of residual displacement is reached, the pressure rapidly begins to increase with little change in the displacement, and the pressure eventually reaches the previously experienced pressure Po (1). After that, the displacement is monitored during the increase in the pressure up to Po (1)+δ, and the relation between the pressure and the displacement of the central soil layer at the second base pressure level is produced, as shown in  FIG. 8  (D). The gradient of this pressure-displacement relation is again defined as the deformation modulus. The pressure is then reduced down to Po (1). Although the pressure is reduced down to the level of Po (1), the residual displacement remains at the central soil layer J 2 , and therefore the displacement would not recover completely. 
   In a manner similar to the above, the static loading is conducted at the central soil layer J 2 , after the cyclic loading on the top and bottom soil layers, J 1  and J 3 . As long as the recoverable elastic zone is concerned, the deformation modulus obtained from the pressure-displacement relations remains almost the same. 
   After a few tests of cyclic loading (kth), the central soil layer J 2  experiences the state of yielding. In such a case, it takes time to increase the level of the pressure from Po (k) to Po (k)+δ, and at the same time the displacement steadily increases with little change in the pressure. The relations between the pressures and the displacements in such cases become steeper, as shown in  FIG. 8  (E). 
   Eventually, the central soil layer J 2  experiences the state of failure, (at the mth test corresponding to the next test after the state of yielding is reached). The pressure is then reduced after achieving the peak Pl and becomes stable when the pressure reduces down to a certain level of pressures such as a hydro-static pore water pressure. The displacement begins to increase rapidly at around the state of failure as shown in  FIG. 8  (B), and the pressure-displacement relation shows a curve in which the displacement increases while the pressure even decreases. 
   By examining the data of the displacements at the top and bottom soil layers, J 1  and J 3 , during cyclic loading, and the data of the displacement at the central soil layer J 2  during static loading, the dynamic deformation characteristics of soils can be examined, and the yield strength and the failure strength are derived. 
   Liquefaction is supposed to occur at the central soil layer J 2 , where the cyclic shear stress acts from both of the top and bottom layers Once the liquefaction is induced, the displacement in the data shown in  FIG. 8  begins to increase rapidly and the occurrence of liquefaction can be confirmed. The occurrence of liquefaction can also be confirmed by observing whether the pore water pressure becomes stably constant. 
   As described above in the working example 2, the simple, reliable, time-saving, cost-effective and accurate dynamic testing can be performed by cyclically exciting the top and bottom soil layers alternatively leading to the central soil layer subjected to cyclic shear stress, without resorting to the torsional loading and shear loading parallel to the bore-hole axis as adopted in the working example 1. 
   In the working example 2, the zone where only the static loading act was provided along the zonde. However, it is also possible to make the zonde formed only by the zones (cells) where the cyclic loading acts, without providing the zone (cell) where the static loading acts, and to pay attention only to the displacements at the top and bottom soil layers. By doing so, the shear loading acts at the boundaries between the top and bottom soil layers, and the effects induced by liquefaction are supposed to propagate to the top and bottom soil layers. 
   In the working examples described so far, the cyclic loading is applied at the two cells to the top and bottom soil layers. However, it is also possible to provide more than 3 cells at which the cyclic loading is applied. In such cases, the zone of static loading can be provided at the center of the adjacent two zones of cyclic loading. 
   As far as the manner in which the cyclic loading is applied is concerned, it can be applied either as compressional loading acting towards the radial direction against the bore-hole axis, or as torsional loading acting around the bore-hole axis, or as shear loading acting parallel to the bore-hole axis. It can be applied as combinations of the types of loading described above. 
   In the working examples 1 and 2, the bore-hole  100  was produced orthogonal to the ground surface. However, it can be produced in the directions parallel to the ground surface, or in the directions oblique to the ground surface. 
   Instead of using the membrane zondes  110  and  111  as monitoring cells, hydraulically operated metal plates such as piston jacks can also be used. The types of loading devices can be chosen based on the types of soil layers tested. 
   Working Example 3 
   The working example 3 for the test apparatus aimed at exploring in-situ the liquefaction and dynamic characteristics of soils using bore-hole is described. 
   In the above working example 2 the zonde which is inserted into a bore-hole is made up of separate multiple cells, which can apply the pressures independently to the corresponding soil layers via liquid media filled in the cells. The pressure and displacement at the bore-hole wall at each cell are monitored. The zonde is made up of three cells, i.e. a central cell at which the static loading is applied, and top and bottom cells at which the cyclic loading is applied alternatively with one another. By applying the cyclic loading alternatively to the top and bottom cells, the pressure and displacement at the central cell is monitored and examined, which are supposed to undergo some effects of cyclic loading on the top and bottom cells. 
   However, the effects of cyclic loading imposed by the top and bottom cells are seen eminent to the soil layers located above the top cell and also located beneath the bottom cell. In some cases, there is a possibility that the data which accurately reflect the soil behavior cannot be obtained due to the collapse of the soils located close to the top and bottom cells. 
   The maintenance of devices in the fields also poses great concern, for instance since the membranes on the zonde need replacement and supplies from time to time. 
   In the working example 3, it is aimed at offering a testing apparatus, which can monitor the effects of cyclic loading imposed on the soil layers located above the top cell and also located beneath the bottom cell, and which can prevent any irrelevant collapse of soils around the zonde. 
   It is also intended to offer a testing apparatus which is good for maintenance. 
     FIG. 9  shows the schematic illustration of a testing apparatus aimed at exploring in-situ the liquefaction and dynamic properties of soils using bore-holes, with reference to the working example 3 in the present invention. 
   The monitoring zonde  1 , which is lowered down into a bore-hole  100 , is composed of a central cell  11  which applies the static loading, top and bottom cells,  12  and  13 , which apply the cyclic loading. Herein, the top and bottom cells,  12  and  13 , are located above and beneath the central cell  11 . The guard cells,  14  and  15 , are installed above the top cell  12  and beneath the bottom cell  14 , respectively. 
   The cells of  11 ,  12 ,  13 ,  14  and  15  described above are equipped with the independent pressure rooms,  11   a ,  12   a ,  13   a ,  14   a  and  15   a . The hydraulic pressures supplied from the pressure rooms,  11   a ,  12   a ,  13   a ,  14   a  and  15   a , filled with water are supposed to act independently on the soil layers J 1 , J 2 , J 3 , J 4  and J 5 , during which the pressures and displacements at the bore-hole wall are monitored. 
   The cells of  11 ,  12 ,  13 ,  14  and  15  have the same structural components, but with different lengths, as shown in  FIG. 10  (A). Each cell has a cylindrically shaped cell body  31 , a cylindrical membrane  32  attached to the outer circumference of the cell body and a pressure room of  11   a ,  12   a ,  13   a ,  14   a  and  15   a  filled with a liquid media located between the cell body  31  and the membrane  32 . The membrane  32  is cylindrically shaped, and is equipped with the circular projections  32   a  sticking inwards, which are put at the top and bottom ends and connected to the cell body regarding the length of each cell, the total length of the zonde adopted here is 90 cm can be divided into the cells, such as 10 cm each for the central cell, top and bottom guard cells, and 30 cm each for the top and bottom loading cells. The central cell and the top and bottom loading cells can be 15 cm, and the top and bottom guard cells can be as large as 22.5 cm long. 
   The lengths of the cells can be chosen based on the conditions of loading and types of soils. 
   The cells of  11 ,  12 ,  13 ,  14  and  15  are designed to be exchangeable with one another. In this working example, the small hole  31   a  is provided at the center of the cell body  31 , and the shaft rod  16  is penetrated through the hole  31   a . The upper end of the cells is fixed by the stopper  17  of the shaft rod  16 , and the lower end is tightly fixed by the nut  18 . The top end of the shaft rod  16  constitutes a connection  16   a  to fix with a boring rod. 
   The thin annular ring  33  is provided between the two adjacent cell bodies  31  and other  31 . 
   The circular projection  32   a  sticking inwards, which is located at the end of the membrane  32  is tightly fixed between the seal plate  33  and the cell body  31 , as shown in  FIG. 10  (C). The small hole  33   a  is provided at the center of the circular seal plate  33 , through which the shaft rod  16  is penetrated. 
   At the top and bottom of the sidewall of the circular projection  32   a  of the membrane  32 , the projections,  32   b  and  32   c , are provided, which are connected each with the annular groove  31   b  located at the end of the cell body  31 , and with the circular projection  33   c  located at the seal plate  33 . 
   The top guard cell  14  is connected with the stopper  16   a  via the top plate  34 , and the bottom guard cell  15  is connected with the nut  17  via the bottom plate  35 . On the plates,  34  and  35 , the annular groove is provided, which is connected with the projection  33   c  located at the circular projection  32   a  of the membrane  32 . 
   Around the cell body  31 , the water tubes of  11   b ,  12   b ,  13   b ,  14   b  and  15   b  are provided, which are used for filling the pressure rooms of the cells  11 ,  12 ,  13 ,  14  and  15  with water. The pressure tubes of  41   a ,  42   a ,  43   a ,  44   a  and  45   a  are provided, which are used for transmitting the pressures generated in the pressure rooms of  11   a ,  12   a ,  13   a ,  14   a  and  15   a  into the pressure gauges of  41 ,  42 ,  43 ,  44  and  45 . At the top plate  34 , the connection ports for the five pressure gauges of  41 ,  42 ,  43 ,  44  and  45 , and also for the five water tubes of  11   b ,  12   b ,  13   b ,  14   b  and  15   b .  FIG. 10  (A) shows the cross sections, which include the water tube to each cell and the pressure tube to each pressure gauge, and therefore the positions of the cross sections are different at each cell. Each connection port is connected with the pipe to provide a connection with a pump unit. Each pressure gauge is wired electrically. These pressure gauges of  41 ,  42 ,  43 ,  44  and  45  are preferably assembled into one unit. 
   The water tubes and pressure tubes for the cells located at the lower positions pass through inside the cell bodies located at the upper positions. At the cell body  32  of the guard cell  14  located on top of all the cells, the five water tubes of  11   b ,  12   b ,  13   b ,  14   b  and  15   b , and also the five pressure tubes of  41   a ,  42   a ,  43   a ,  44   a  and  45   a  are provided. At the cell body located beneath the guard cell  14 , there are 4 water tubes and 4 pressure tubes connected with it. In the same manner, as the cell becomes positioned lower, the number of tubes becomes less one by one, and eventually at the guard cell  15  of the cell body  32  located at the bottom of all the cells, there is only one water tube and one pressure tube connected with it. 
   In the case of the water tubes and pressure tubes passing through both the upper cell and lower cell, as shown in  FIG. 10  (C), the water pipe  13   b  and the pressure pipe are provided between the upper cell  32  and the lower cell  32 , via the connection port  33   d  located at the seal plate  33 . The seal  33   e  such as an O-ring is provided around the connection port  33   d  to fill the gap between the seal plate  33  and the upper and lower cells  32 . To fix the upper cell and lower cell properly the needle pin  33   f  is provided at the surface of one of the cells, while the corresponding hole  33   g  is provided at the surface of the other cell. 
   In order to examine the occurrence of liquefaction at the central soil layer J 1 , to which the central cell  11  applies the loading, as shown in  FIGS. 11  (A) and (D), the pressure gauge  20  is provided to monitor the pore water pressure at the soil layer corresponding to the central cell  11 . 
   In the working example, the pore water pressure gauge  20  is located at the top plate  34 , and the inlet opening  21  is provided at the surface of the membrane  31  of the central cell  11 . The inlet opening  21  and the pore pressure gauge  20  are connected by the pressure tube  22 . At the inlet opening  21 , the piece of porous stone is embedded to prevent any intrusion of obstacles into the pressure tube. The pore pressure gauge  20  is also preferably assembled together with the pressure gauges of  41  to  45  into one unit. 
   Regarding the structure of the pore pressure gauge  20 , the surface of the sensor itself can be placed at the central cell  11 , and the electrical wires can either pass through inside the monitoring cell or it may be monitored by wireless means, or any other means can be adopted. 
     FIG. 12  shows one example of the controlling unit for the above monitoring cell. 
   The controlling unit is composed of several functions. The first one is a series of pumping units of  51 ,  52 ,  53 ,  54  and  55 , which are used for transmitting water into the pressure rooms of  11   a ,  12   a ,  13   a ,  14   a  and  15   a  of the cells,  11 ,  12 ,  13 ,  14  and  15 . The second one is the pressure supplier  60 , such as gas cylinders and air compressors, which activate the pumping units of  51 ,  52 ,  53 ,  54  and  55 . The third one is the regulator  57 , which controls the air pressure coming from the pressure supplier  60 . The fourth one is the controlling box  58 , which operates the pumping units and the regulator  57 . The fifth one is the water tank  59  for the pumping units of  51 ,  52 ,  53 ,  54  and  55 . The sixth one is the personal computer  50  with the software for data analyses and graphics, which is wired to the controlling box  58 . A series of the pumping units are assembled into one frame with five units on top and the other five units placed in series at the bottom. There can be only one water tank. 
     FIG. 13  shows an example of pumping units. All the pumping units of  51 ,  52 ,  53 ,  54  and  55  have the same structural components, and therefore the structure of the pumping unit  51  is described below. 
   The pumping unit  51  is composed of a couple of cylinders, 1st cylinder  71  and 2nd cylinder  72 , which are inter-connected via the cylinder rod  73 , as shown in  FIG. 13  (A). There are two rooms in one cylinder, among which the room filled with water is located on the opposite side with respect to the cylinder rod  73 . Herein, the water-filled rooms are called  71   a  and  72   a  for the cylinders of  71  and  72 , respectively. The room  71   a  of the 1st cylinder  71  is connected to the water tube for the monitoring cell via the 1st water tube  81 . Along the 1st water tube  81 , the 1st valve  91  is provided. The room  71   a  is also connected to the water tank  59  via the 2nd water tube  82 , which are branched off from the 1st water tube  81 . The 2nd water tube is also equipped with the 2nd valve  92 . 
   The room  72   a  of the 2nd cylinder  72  is connected to the water tube corresponding to the monitoring cell  1  via the 3rd water tube  83 . Along the 3rd water tube  83 , the 3rd valve  93  is provided. The room  72   a  is connected to the water tank  59  via the 4th water tube which is branched off from the 3rd water tube  83 . Along the 4th water tube  84 , the 4th valve  94  is provided. 
   The 1st water tube  81  and the 3rd water tube  83  are designed to join together at the downstream of the 1st valve  91  and the 3rd valve  93 , and are then connected to the monitoring cell via the united line of the 1st and 3rd water tubes  85 . The 2nd water tube  82  and the 4th water tube  84  are designed to join together at the downstream of the 2nd valve  92  and the 4th valve  94 , and are then connected to the water tank  59  via the united line of the 2nd and 4th water tubes  86 . 
   The 1st valve  91  and the 3rd valve  93  are activated by the air pressure supplied from the air pressure supplier  60 . The air pressure is controlled by the electromagnetic valve  96  used for the control of the 1st valve, as shown  FIG. 13  (B). The 2nd valve  92  and the 4th valve  94  are activated by the air pressure, which are controlled by the electromagnetic valve  97  used for the control of the 2nd valve, as shown in  FIG. 13  (C). 
   Located at the sides of the rods in the 1st cylinder  71  and 2nd cylinder  72  are the air pressure rooms of  71   b  and  72   b . The air pressures are selectively introduced into the air pressure rooms of  71   b  and  72   b  via the electromagnetic valve  74  used for activating cylinders, 1st air tube  76  and 2nd air tube  77 . This electromagnetic valve is the control valve with 5 ports and 3 positioning controls. The 3 positioning controls correspond to the pressure-supplying position for the 1st cylinder, the neutral position, and the pressure-supplying position for the 2nd cylinder. 
   The pressure-supplying position for the 1st cylinder is designed to supply the air pressure into the air room  71   b  of the 1st cylinder  71 , and to release the air pressure in the air room  72   b  of the 2nd cylinder  72 . The pressure-supplying position for the 2nd cylinder is designed to supply the air pressure into the air room  72   b  of the 2nd cylinder, and to release the air pressure in the air room  71   b  of the 1st cylinder  71 . 
   In the case of increasing the pressure in the pressure room of the monitoring cell  1 , the electromagnetic valve  74  for activating cylinders is switched into the pressure-supplying position for the 1st cylinder. In addition, the electromagnetic valve  96  used for the control of the 1st valve is switched on, while the electromagnetic valve  96  used for the control of the 2nd valve is switched off. Moreover, the 1st valve  91  and the 4th valve  94  are opened, while the 2nd valve  92  and the 3rd valve  93  are closed. From the pressure supplying unit such as an air compressor, the air pressure is supplied into the air room  71   b  of the 1st cylinder  71  via the 1st airtube  76 , and the water-filled room  71   a  of the 1st cylinder  71  is compressed. The 2nd and 3rd valves of  92  and  93  are closed, and therefore, the liquid medium of water in the water-filled room  71   a  of the 1st cylinder  71  is introduced into the pressure room of the monitoring cell  1  via the united line of the 1st and 3rd water tubes R 5 , and supplies the pressure. Consequently, the other water-filled room  72   a  of the 2nd cylinder  72  is subjected to volume expansion and there are, the liquid medium of water in the water tank  59  is allowed to flow into the room  72   a  via the united line of the 2nd and 4th water tubes  86  and also the 4th water tube  84 . 
   Then, the electromagnetic valve  74  for activating cylinders is switched into the 2 pressure supplying position for the 2nd cylinder. In addition, the electromagnetic valve  96  used for the control of the 1st valve is switched off, while the electromagnetic valve  96  used for the control of the 2nd valve is switched on. Moreover, the 1st valve  91  and the 4th valve  94  are closed, while the 2nd valve  92  and the 3rd valve  93  are opened. From the pressure supplying unit  60  such as an air compressor, the air pressure is supplied into the air room  72   b  of the 2nd cylinder  72  via the 2nd air tube  77 , and the water-filled room  72   a  of the 2nd cylinder  72  is compressed. The 1st and 4th valves of  91  and  94  are closed, and therefore, the liquid medium of water in the water-filled room  72   a  of the 2nd cylinder  72  is introduced into the pressure room of the monitoring cell  1  via the 3rd water tube and also the united line of the 1st and 3rd water tubes  85 , and supplies the pressure while the other water-filled room  71   a  of the 1st cylinder  71  is subjected to volume expansion, and therefore, the liquid medium of water in the water tank  59  is then allowed into the room  71   a  via the united line of the 2nd and 4th water tubes  86  and also the 2nd water tube  82 . 
   By repeating the same operations, the pressure in the monitoring cell is gradually increased. 
   In the case of reducing the pressure in the pressure room of the monitoring cell  1 , the electromagnetic valve  74  for activating cylinders is switched into the pressure-supplying position for the 2nd cylinder  72 . The cylinder rod  73  is then moved to the right direction in the diagram. 
   The liquid medium of water in the monitoring cell  1  is then forced to move into the water-filled room of the 1st cylinder  71 , and the liquid medium of water in the water-filled room of the 2nd cylinder  72  returns back to the water tank  59 . 
   In the case of reducing the pressure in the pressure room of the monitoring cell  1 , the electromagnetic valve  74  for activating cylinders is switched into the pressure-supplying position for the 2nd cylinder. In addition, the electromagnetic valve  96  used for the control of the 1st valve is switched on, while the electromagnetic valve  96  used for the control of the 2nd valve is switched off. Moreover, the 1st valve  91  and the 4th valve  94  are opened, while the 2nd valve  92  and the 3rd valve  93  are closed. From the pressure supplying unit  60  such as an air compressor, the air pressure is supplied into the air room  72   b  of the 2nd cylinder  72  via the 2nd air tube  77 , and the water-filled room  72   a  of the 2nd cylinder  72  is compressed. The 2nd and 3rd valves of  92  and  93  are closed, and therefore, the liquid medium of water in the water filled room  72   a  of the 2nd cylinder  72  returns back into the water tank  59  via the 4th water tube and also the united line of the 2nd and 4th water tubes  86 . 
   Consequently the other water-filled room  71   a  of the 1st cylinder  71  is subjected to volume expansion, and therefore, the liquid medium of water in the pressure room of the monitoring cell  1  is allowed to flow into the room  71   a  via the united line of the 1st and 3rd water tubes  85  and also the 1st water tube  81 . 
   The electromagnetic valve  74  for activating cylinders is then switched into the pressure-supplying position for the 1st cylinder. In addition, the electromagnetic valve  96  used for the control of the 1st valve is switched off, while the electromagnetic valve  96  used for the control of the 2nd valve is switched on. Moreover, the 1st valve  91  and the 4th valve  94  are closed, while the 2nd valve  92  and the 3rd valve  93  are opened. From the pressure supplying unit  60  such as an air compressor, the air pressure is supplied into the air room  71   b  of the 1st cylinder  71  via the 1st air tube  76 , and the air room  71   a  of the 1st cylinder  71  is compressed. The 1st and 4th valves of  91  and  94  are closed, and therefore, the liquid medium of water in the water-filled room  71   a  of the 1st cylinder  71  is let flow back into the water tank  59  via the 2nd water tube and also the united line of the 2nd and 4th water tubes  86 . Consequently, the other water-filled room  72   a  of the 2nd cylinder  72  is subjected to volume expansion, and therefore, the liquid medium of water in the pressure room of the monitoring cell  1  is now allowed into the room  72   a  via the united line of the 1st and 3rd water tubes  85  and also the 3rd water tube  83 . 
   By repeating the same operations, the pressure in the monitoring cell is gradually reduced. 
   Each pumping unit is equally equipped with the displacement sensor  75  to monitor the amplitude (stroke) of the movement of the rod of the cylinder. From the outputs of this displacement sensor  75 , the volume of the water flowing in and out of the monitoring cell  1  is calculated. During the process of increasing the pressure, the volume of the water flowing in and out of the monitoring cell is calculated by adding the amplitudes of the movements of the 1st cylinder  71  and 2nd cylinder  72 . During the process of reducing the pressure, it is calculated by subtracting the amplitude of the movement of the 1st cylinder  71  from that of the 2nd cylinder  72 . The radial displacements of the bore-hole wall are then calculated from the change in the volume of the water thus obtained. 
   The control of the pressure increase and decrease in the pumping unit is carried out in the following manner. The expected time history of the pressure change is produced as reference data. The outputs from the pressure gauge are monitored and transmitted back as a feedback to the electromagnetic valves of  74 ,  96  and  97 , and the open/close operations of these valves are controlled to follow accurately the expected time history of the pressure change. 
   The pressure change is designed to fluctuate periodically up and down with respect to the reference pressure level set up at each base pressure level, while the reference pressure level is increased as the cycles of the pressure change proceed. The waveform can be taken in the form of a sinusoidal shape, or in the form of a rectangular shape, or in the forms of any other shapes, depending on the conditions of the tests. The monitored data of the pressure gauges are transmitted to the personal computer as feedback. Upon receiving such feedback, the personal computer serves as the transmitter of the digital signals for the open/close operations of the electromagnetic valves of  74 ,  96  and  97 . The pressure changes are controlled to accurately follow the pre-determined time history. The operation of control particularly depends on whether it is in the process of increasing the pressure or reducing the pressure. 
   The feedback can be conducted not only with respect to the amplitude of the pressure, but also with respect to the displacement (stroke) of the movement of the cylinder rod. 
   The air bubbles due to cavitation might be generated and the response of the pressure control might be worsened when the pressure is reduced rapidly. Therefore, in order to control the speed (flow rate), as shown in  FIG. 16 , the flow-rate control valve  62  equipped with the function of back-flow prevention  61  can be installed along the united line of the 1st and 3rd water tubes  85  and the united line of the 2nd and 4th water tubes  86 . The valve for the back-flow prevention  61  and the flow-rate control valve  62  are installed in parallel. 
   The valve for the back-flow prevention  61 , installed along the united line of the 1st and 3rd water tubes  85  connected with the monitoring cell  1 , allows the inflow towards the monitoring cell, but prevents the outflow from the monitoring cell. Therefore, the flow rate is controlled during the outflow from the cell, while the flow smoothly takes place during the inflow towards the cell, with a help of the valve for the back-flow prevention, which serves as a bypass line on behalf of the flow-rate control valve. 
   The flow rate control valve  62  equipped with the function of back-flow prevention  61  can be installed along the 1st air tube  76  and 2nd air tube  77 , which are located between the electromagnetic valve  74  for activating cylinders and the 1st cylinder  71  and 2nd cylinder  72 . The valve for the back-flow prevention  61  might be installed in such a manner that allows the inflow towards the air rooms of  71   b  and  72   b , but prevents the outflow from these rooms. 
   In this working example, the 1st cylinder  71  and 2nd cylinder  72  are activated to produce a given pressure change during cyclic loading. However, as shown in  FIG. 16 , the alternative method is also possible by connecting the cylinder for cyclic loading  63  with the united line of the 1st and 3rd water tubes  85 . After increasing the pressure up to a given point using the 1st cylinder  71  and 2nd cylinder  72 , the cyclic loading can be conducted by making the cylinder  63  for cyclic loading move back and forth periodically. It is also possible to organize the system, in which the back and forth movement of this cylinder  63  can be applied mechanically instead of hydraulically. 
   The testing procedure is described in detail below. 
   The bore-hole  100  is produced down to a given depth of testing. The monitoring cell  1  is lowered down to a given depth into the bore-hole  100  using the boring rod  100 . First, the pressures are supplied into the pressure rooms of  11   a ,  12   a ,  13   a ,  14   a  and  15   a , which are belonging to the central cell  11 , top and bottom cells of  12  and  13 , and the top and bottom guard cells of  14  and  15 , until the membranes of all the cell are intimately attached to the bore-hole wall. 
   The pressures are equally increased in the central cell  11 , and the top and bottom guard cells of  14  and  15 . 
   The cyclic changes of the pressures are applied to the liquid media of water in the pressure rooms of  12   a  and  13   a  belonging to the top cell  12  and bottom cell  13 . The outputs from the pressure gauges of  41 ,  42 ,  43 ,  44  and  45 , and also from the now-rate sensors  75  of all the pumping units are read off and stored into the personal computer  50 . The pressures in the pressure rooms and the radial displacements at the bore-hole wall are all displayed on the PC monitor. The output from the pore water pressure gauge  20  installed at the central cell  11  is also read off and stored into the personal computer  50 . 
   From the cyclic pressure-displacement relations obtained by applying the cyclic pressures to the top and bottom cells of  12  and  13  with a frequency of 0.1 to 1 Hz, the dynamic deformation and strength characteristics of soils can be examined. 
   By applying the cyclic pressures to the top and bottom cells of  12  and  13 , as shown in  FIG. 14 , three levels of the pressures, P 11 , P 12  and P 13 , are applied at the side wall of the central cell  11 . When the levels of the pressures P 12  and P 13  become larger than P 11 , the state of yield and ultimately the state of failure begins to prevail within the soil layer J 1 , and the phenomenon of the central cell  11  being pushed back inwards by the collapsing soils is observed. Depending on the conditions of soils, the level of the pressure P 11  becomes less than P 12  and P 13 , and the phenomenon of the central cell being pulled off outwards is observed as indicated by a dashed line. Therefore, it is possible to examine the dynamic characteristics of the soil layer J 1 , by monitoring the displacements of the central cell  11  and distinguishing whether the central cell is pushed inwards or pulled outwards. In case of sandy soils, these phenomena associated with the behavior of the central cell can be identified as the collapse of the soils and ultimately soil liquefaction. In the testing apparatus adopted in the present invention, the behavior of the pore water pressures at the soil layer J 1  can be monitored directly using the pore water pressure gauge  20 . Therefore, it is possible to offer the useful data associated with soil liquefaction. For instance, the correlation between the pore water pressure behavior and the pressure-displacement relations can be examined, especially at the collapsing state where the displacement rapidly increases. 
     FIG. 15  shows the real data obtained by this testing apparatus. It is seen that the negative displacement occurs at around 240 seconds, and it is considered that the collapse begins at this stage. 
   By conducting the static loading tests after the cyclic loading, the strength reduction due to fatigue can be estimated in case of clayey soils, while the residual strength during liquefaction can be estimated in case of sandy soils. 
   The behavior of the displacements at the top and bottom guard cells of  14  and  15  can also be monitored and recorded. By comparing such data with the data of the central cell  11 , the verification, analysis and interpretation of the data becomes more rational. 
     FIG. 17  shows an extended version of the working example 3. 
   The basic structural components are the same as in the working example 3. So, the components that are different from the working example 3 are described below. The identical components are coded with the same symbols. 
   In this example, the circular water tank  359  is equipped with the scale along its side. So, the volume of the water flowing in and out of the monitoring cell  1  can be measured by the manual reading of the scale as well as by the displacement (stroke) sensor  75 . By monitoring the water level of the water tank, the operator can have some direct information regarding the displacements of the bore-hole wall. The reliability of data can also be improved by installing the monitoring sensor  365  for the water level, and storing the data in the personal computer, and then comparing the data of the volume of the water which are calibrated by the water level against those calibrated by the displacement (stroke) sensor  75 . In this example, the monitoring sensor  356  of the water level is a pressure transducer, and is installed at the bottom of the water tank  359 . The hydrostatic pressure gained from the pressure transducer is calibrated to a depth of water, from which the change in the water level is calculated. It is also possible to adopt any other means for the water level measurement, such as a floating buoy and other available sensors. 
   The pressure gauge equipped with a scale  360  can be installed along the tube between the pumping unit and the monitoring cell. By locating the pressure gauge above the water tank  359 , the change of the pressure supplied from the pumping unit and the water level in the water tank  59  can be manually monitored. By this means, it is possible to acquire some direct information with respect to the pressure supplied and the displacements at the bore-hole wall (radial deformation of the membrane of the monitoring cell  1 ). The pressure gauge  360  can be an analogue-type or a digital-type. 
   The data of the pressure thus obtained from the pressure gauge  360  are transmitted into the personal computer  50 . By comparing such data with the pressures measured at the pressure rooms in the cells, the influence of the flexibility of the tubes can be examined, and thus the reliability of data can be improved. 
   It is also possible to install the pressure gauge equipped with a scale for the pressure rooms of the monitoring cell  1  in the following manner. The tube  361  is extended up to the ground surface from each of the pressure rooms of the monitoring cell located in the bore-hole. The pressure gauge  362  can be installed along this extension tube  361 , and put above the water tank  359  along side the pressure gauge  360  measuring the pressure supplied from the pumping unit. By this means, it can be monitored directly with a scale, together with the pressure supplied from the pumping unit and the water level of the tank  359 . The data of the pressures monitored by the pressure gauge  362  is also transmitted to the personal computer  50 , and, therefore, the reliability of data can also be improved by comparing it with the data of the pressure originally supplied from the pumping unit. 
   Using the testing apparatus shown in this working example 3, it is also possible to conduct conventional monotonic pressure meter tests by applying the static loading via the top and bottom cells of  12  and  13 . In this case, the soil layer around the central cell  11  is subjected to the static compression from both of the top and bottom cells,  12  and  13 . So, the useful information can be deducted from the pressure-displacement behavior at the central cell during such tests. In this working example 3, the control of cyclic loading is conducted using pumping units. However, it is also possible to control the cyclic loading using servo-valves. 
   Instead of the monitoring cells equipped with multiple pressure rooms adopted in the invention, it is also possible to connect a conventional type of pressuremeters equipped with only one pressure room with the driving and controlling unit adopted in the present invention. By this means, it becomes possible to conduct conventional monotonic pressuremeter tests in a more controlled manner, as it is used to be conducted manually. Full automatic pressuremeter test equipment is available, but the replacement of the whole system is not cost-effective. Instead, by adopting the testing apparatus in the present invention, the conventional pressuremeter test equipment can also be recycled, and the full automatic conventional tests can be conducted. 
   INDUSTRIAL APPLICABILITY 
   The present invention allows in-situ examination of dynamic strength and deformation characteristics of soils during cyclic loading without any soil sampling. In addition, it is possible to conduct tests on loose sand deposits, gravel-containing soil deposits, soil deposits involving large-sized grains such as sandy gravels, weathered rocks and soft rocks, which are difficult to soil sample, and therefore its utility extends to such soil deposits. It is also time and cost-effective, compared with the conventional sampling and laboratory tests. 
   It is especially noteworthy that by applying the cyclic loading alternatively to the multiple locations along the bore-hole axis, the cyclic shear stress is induced at the boundaries of the loaded areas. So, the characteristics of soils against cyclic shear loading as well as against cyclic compressional loading can be examined. Soil liquefaction is associated with shear loading, so the assessment of liquefaction occurrence can also be examined. When the collapse of soils occurs, the liquefaction might propagate into the compressionally loaded areas, and the displacement might change greatly. 
   EXPLANATIONS OF LETTERS OR NUMERALS 
   
       
         201 : Membrane zonde (monitoring cell) 
         202 : Water tank 
         203 : Water (liquid medium) 
         204 : Pressure supplier 
         205 : Pressure valve 
         206 : Connection tube 
         207 : Personal computer 
         209 : Torque generation unit 
         210 : Monitoring unit for displacement 
         211 : Device for generating shear loading 
         212 : Monitoring unit for displacement 
         100 : Boring hole 
         111 ,  112 ,  113 : 1st, 2nd, 3rd cells 
         121 ,  122 ,  123 : 1st, 2nd, 3rd pressure controlling device 
         114 : Cell body 
         115 : Membrane 
         116 : Connection parts 
         120 A: Gas cylinder 
         120 B: Gas tank 
         121 C,  123 C: Hydraulic cylinders 
         121 D,  123 D: Valves 
         121 E,  123 E: Valves 
         122 C: Water tank 
         122 D: Pressure valve 
       J 1 : Top soil layer 
       J 2 : Central soil layer 
       J 3 : Bottom soil layer 
         150 : Pore water pressure gauge 
         100 : Bore-hole 
         1 : Monitoring cell 
         11 : Central cell 
         12 : Top cell 
         13 : Bottom cell 
         14 : Top guard cell 
         15 : Bottom guard cell 
         11   a ,  12   a ,  13   a ,  14   a ,  15   a : Pressure rooms 
       J 1 , J 2 , J 3 , J 4 , J 5 : Soil layers 
         31 : Cell body 
         32 : Membrane 
         33 : Seal plate 
         34 : Top plate