Patent Publication Number: US-5295337-A

Title: Isolation element and the use thereof at an isolation arrangement

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention concerns an isolation element for the isolation of vibrations and/or heat, which are propagated in a medium such as soil, as well as the application of such isolation elements in connection with vibration isolation measures. 
     2. Description of the State of the Art 
     Vibrations, which are generated in a medium such as soil or water, and which are propagated through this medium, can cause damage to structures, which are located on or in this medium. Vibrations can be generated by a variety of sources, for example by vehicles, machines, blasting or earthquakes. Many attempts have been made to eliminate the propagation of vibrations, in order to protect structures, machines or installations. As a result of such measures, as a secondary effect, it is also possible to isolate the propagation of heat. 
     Open trenches in the soil are effective measures to protect buildings and other structures in the ground against oscillations and vibrations. Another common method of vibration isolation is to arrange concrete or steel barriers in the ground. Their vibration efficiency, however, is significantly lower than that of open trenches. Swedish Patent Document No. SE, B, 430,620 shows a method for vibration isolation with the aid of one or several membranes, which are installed in the ground, and an arrangement for the implementation of this method. This method is characterized by a membrane or connected membranes. which contain a medium such as air, water or similar agents, and which are made of plastic or similar material, and which are installed in the ground vertically or inclined for instance by means of pressing, vibrating, driving, jetting or a combination of these methods, with the aim of absorbing the vibration energy and to reduce the oscillation energy. The membrane is provided at the upper end with a valve body, through which the pressure in the membrane can be varied before, during or after installation. The membrane can at the lower end be provided with a beam-like arrangement, which during the installation phase creates an opening in the soil of required width. The membrane or membranes can, for example, be installed using a fork-like tool. The described method is expensive and there exists a risk that one or several receptacles are damaged by a sharp article located in the ground. 
     Swedish Patent Document No. SE, B. 460.062 shows an arrangement for vibration isolation and/or heat isolation. The arrangement comprises membranes which can be installed in a medium such as soil or water. The membranes consist of a flexible, external, relatively stiff covering membrane, which is impermeable with respect to the mentioned medium, and at least one additional flexible inner membrane element consisting of a diffusion-tight material. The inner membrane surrounds a closed space consisting of p double-folded foil, which is welded together to form a receptacle and cells or channels filled with air, gas, liquid or foam or a combination thereof on the side surfaces of the receptacle. The cells or channels of one side of the foil are separated from the cells and channels of the other side of the foil, whereby one (or several) chambers are created between them which can either be filled with air, gas, liquid or foam. A valve can be arranged at the inner membrane in order to make it possible to fill the space with an appropriate material and with desired pressure. The risk of puncturing of the multi-layered membrane is thereby reduced. Damage to one or several chambers do not affect the vibration isolation effectiveness of the membrane. The covering envelope is so stiff that it can distribute variations of the earth pressure. However, the above mentioned disadvantage of high installation cost remains. 
     In built-up areas, it is common to first excavate a trench in the ground, which is filled with a suitable stabilizing liquid in order to assure the stability of the trench during installation. For the installation of the above mentioned vibration isolation arrangement in a liquid-filled trench, the isolation elements must be provided with special anchors at the bottom of the excavated trench, as the buoyancy of the gas-filled cushions can be considerable. The anchoring can be provided by heavy concrete blocks which are attached in advance to the lower end of the cushions. Alternatively, the cushions can be connected to ground anchors which are installed at the bottom of the trench. The installation of concrete blocks requires the lifting of heavy loads. In addition, the trench must be excavated to greater depth in order to provide space for the anchoring weights. The isolation elements must be installed accurately in the trench in order to achieve a continuous isolation barrier. In practice, it can be difficult to place the flexible cushions with sufficient precision, in order to assure vertical and laterial continuity of the isolation barrier. 
     SUMMARY OF THE INVENTION 
     The present invention combines the vibration isolation effect of an open trench with that of a stiff wall, and offers in addition a solution to the above described installation problems. The invention comprises an isolation element in the shape of a generally rectangular, plate-shaped block with one or several cushion-shaped bodies attached to one of its two largest surfaces, i.e. the side surfaces. The block is made of a material with high density and high stiffness such as concrete, iron or steel. The cushion-shaped bodies can either be hollow or consist of plastic sheet material or other material with low density and low stiffness, such as styrofoam or plastic material. This material combination produces a high isolation effect, because it achieves a sharp change of the dynamic stiffness (impedance). The invention further comprises the use of isolation elements in an isolation arrangement for the isolation of vibrations and/or heat, preferably in soil or water. The isolation arrangement comprises a trench in the ground, and at the bottom of the trench, preferably vertically anchored guide rods which are placed in a row. The trench is filled with a stabilizing liquid and the isolation elements are inserted, one on top of the other and/or next to each other, on the guiding rods, from the bottom of the trench upwards and preferably in its whole longitudinal length. The elements are erected on the edge sides and can be connected with each other vertically and laterally with the aid of coupling arrangements similar to those of sheet pile locks or wedge locks. 
     The rectangular, plate-shaped isolation elements are manufactured in blocks consisting of a material with high density, preferably concrete, which makes it possible to place the elements simply and with great accuracy, without requiring any special anchoring weights at the lower end of the elements. The guide rods make it possible to construct large isolation barriers in a simple manner and with high precision. It is thus not necessary to excavate the trench deeper. 
     With the aid of the guide rods, it is possible to assemble the isolation elements in such a way that a stiff wall is created. If required, the guide rods can be pre-stressed, whereby a high strength is achieved in order to resist earth pressures or dynamic forces. The vertical wall can also be used to support horizontal isolation elements which are fixed to its upper end. Their function is to protect the isolation elements from e.g. traffic loads, infiltration of polluted substances or against temperature variations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of an isolation element according to the invention. 
     FIG. 2 is a perspective view of a part of an isolation element according to the invention. 
     FIG. 3 is a perspective view at an alternative arrangement for the attachment of the cushion-shaped bodies to each other. 
     FIGS. 4a and 4b are perspective views of isolation elements according to the invention with horizontal and vertical pre-stressing strips, respectively. 
     FIG. 5 is a perspective view of a part of an isolation arrangement, composed of isolation elements according to FIG. 3. 
     FIG. 6 is a perspective view of a block, which forms part of the isolation element according to the invention, broken away to reveal internal structure 
     FIG. 7 is a perspective view of an isolation arrangement in the ground according to the invention. 
     FIG. 8a is a cross-section view of an isolation arrangement according to the invention. 
     FIG. 8b is a top plan view of the isolation arrangement of FIG. 8a. 
     FIG. 9 is a cross-sectional view of the cover of the isolation wall in the surface of the ground according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The implementation of the isolation element is shown in FIG. 1. The isolation element comprises an essentially rectangular, plate-shaped block 1. On one of the two sides of the block 1, two layers of cushion-shaped bodies 2 are attached. As can be seen from the figure, the two layers of the cushion-shaped bodies 2 are placed in a displaced relationship to each other, i.e. overlapping each other, with the aim to avoid vibration or heat bridges which are created by the edges of the cushion-shaped bodies 2. The cushion-shaped bodies 2 can be of any size within the lateral surface boundaries of the plate-shaped block 1 but the cushion-shaped bodies 2 are preferably rectangular with a length corresponding approximately to the length of the block 1, i.e. the lengths the side surfaces of the block 1. If several blocks are placed side by side it may be appropriate to give the cushion-shaped bodies 2 such length that they can bridge joints between the block elements. The cushion-shaped bodies 2 are attached to the block 1 with straps 3 made of plastic or equivalent and extending around the block 1 and the cushion-shaped bodies 2. The cushions can also be attached with the aid of a sheet 4 of plastic or equivalent as is shown in FIG. 2, which in turn is attached to the lower edge of the block 1 with the aid of an attachment bar 5. In this way, the buoyancy forces acting at the cushion-shaped bodies during the installation phase are also counter-acted without the need of straps 3. The sheet 4 can also be attached to the upper edge of the block 1 in a similar way. 
     As shown in FIG. 3, it is also possible to arrange the cushion-shaped bodies 2 in two layers on both sides of a sheet. The cushion-shaped bodies 2 are also in this case preferably arranged with displacement (in the perpendicular direction of the block 1) in such a way that joints between cushion-shaped bodies 2 in one layer preferably are located between the joints of the cushion-shaped bodies 2 in the other layer. 
     Whether the individual cushion-shaped bodies 2 are attached to the block 1 edge to edge or they are connected in one or several layers with some kind of sheet 2, they can also be fixed to the block 1 with pre-stressing straps 7 running in the lateral direction of the block as shown in FIG. 4a, or with straps 8 running in the vertical direction of the block 1, as shown in FIG. 4b. The pre-stressing straps 7, 8 make it possible to increase, by tightening their tension, the pressure in the cushion-shaped bodies 2 a desirable point of the installation phase. 
     Turning now to FIG. 5, the rectangular, plate-shaped block is provided with guiding arrangements on the side surface without cushion. They are preferably archwise loop-like or hook-like attachment elements 9, extending from the block 1 which are interacting with the rods 10, as will be discussed below. Each block 1 suitably contains four or more such attachments elements 9 which are placed in a rectangular pattern with the openings facing the edges of the long sides of the block 1. The attachments elements 9 are preferably placed at such a distance from each other that the side length of the rectangular pattern corresponds to half the side length of the isolation elements. The rectangular plate-shaped block has a coupling arrangements 11 at the end of the edge surfaces of its long side to allow for coupling to an adjoining block. 
     The guiding arrangements can, as is shown in FIG. 6, also have the form of circular channels 12, passing through the block 1 into which the guiding rods 10 can be introduced. Each block 1 suitably contains at least two channels 12 which are arranged perpendicular to the longitudinal direction of the blocks 1. The embodiment with continuous channels 12 makes it possible to use both side surfaces of the block 1 for the attachment of cushion-shaped bodies 2. In order to achieve the channels 12 in a simple way, it is possible to use prefabricated concrete elements with the channels 12 therein. 
     The plate-shaped block 1 is, as described above, suitably manufactured from a material with high density such as concrete, iron or steel. The cushion-shaped bodies 2 can be void and manufactured of a sheet material, preferably of plastic. The hollow cushion-shaped bodies can be filled with gas, such as air, liquid or foam. Alternatively, the cushion-shaped bodies 2 can be made of a material with low density, such as styrofoam, cellular plastic, etc. 
     The invention also concerns the use of isolation elements according to the above in an isolation arrangement for the isolation of vibrations and/or heat preferably in the ground. The basic composition of the isolation arrangement is shown in FIGS. 7 and 8. The isolation arrangement comprises an excavated trench 13 in the ground. In the trench are placed preferably vertical guide rods 10 of iron or similar. The guide rods 10 are arranged in a row and anchored into a steel or concrete beam 14, located at the bottom of the trench 13. The whole isolation installation arrangement is composed of a number of blocks 1 comprising guiding channels 12 according to FIG. 6, whereby the blocks 1 are threaded on to the guide rods 10 and stacked from the bottom of the trench 13 to the orifice and preferably continuously in the longitudinal direction of the trench 13 one on top of the other and/or next to each other placed on their sides. As the blocks consist partially of very stiff material, they can take high static or dynamic forces, e.g. high earth pressures from adjacent buildings, railway lines, heavy machines, etc. The isolation arrangement also comprises a suitable stabilizing material, which is poured into the trench 13 before the placement of the isolation cushion-shaped bodies 2. The isolation elements which are placed one on top of the other can be tied together with the aid of prestressing tool 16, see FIG. 8a. 
     Referring to FIG. 9, when the isolation arrangement is to be located in a road bed, the isolation wall can be provided with a lid-like arrangement. This can consist of a plater or a beam 17 resting at the top element and covering the width of the trench at the level of the road surface. 
     In connection with the installation of an isolation arrangement as described above, the installation can be facilitated if the distance between adjacent guide rods 10 approximately corresponds to about half the length of the isolation elements, provided that also the respective guide arrangements 9 or channels 12 are placed at this distance with respect to each other. In this way, a constant distance is achieved between all adjacent guide rods, which facilitates the completion of the construction work. The isolation arrangement can also include joining elements 11, as discussed above, between the isolation elements at the top. Below the beam 17, an isolation block 18 can be placed in order to achieve insulation against for example frost action. 
     The stabilizing liquid can consist of water, a suspension of water and bentonite, polymers, water and cement/bentonite or other tixotropic materials as well as suitable chemical additives. 
     The conception of the isolation elements and the construction of the isolation arrangement results in significant advantages compared to previously known arrangements. The isolation elements can be manufactured relatively cheaply. They can easily be made effective as a result of the cushion-shaped bodies which can be placed in several layers one on top of the other with displacement. No sophisticated manufacturing methods are required. The cushion-shaped bodies can be manufactured for example by pressure extrusion, a method which is widely used for example for the manufacturing of plastic bags for coffee packaging, etc. The cushion-shaped bodies can, when they are manufactured of plastic sheet material be attached to one another or to an eventual plastic sheet material holding the layer together by simple welding of the plastic material. The sheet material can in turn be attached to the block in a variety of well-known ways. 
     The amount of plastic material used is relatively low. The installation of the isolation elements in connection with the implementation of the isolation arrangement offers significant simplifications compared to previously known methods and thus reduces the cost. Because the blocks are heavy and balance the buoyancy forces resulting from the insertion of the gas-filled cushion-shaped bodies into the slurry-filled trench, no stabilizing weight is required at the bottom of the trench. Therefore, the trench does not have to be excavated as deeply as before and the installation of the isolation elements in the trench is facilitated significantly. The precision is also very high because of the interaction between the guiding rods and the guiding arrangement. This results in a high quality of execution of the finished isolation arrangement. The vibration-damping effect is also very high because of the intimate combination of heavy stiff plate and flexible cushions. The abrupt change of impedance results from the fact that the vibrations must pass through a layer plate/cushion with an unusually high drop of density. 
     Isolation elements can to advantage be used in the case of vibration problems in water, because the elements can be made negatively buoyant. Specially in the case of deep trenches it may be preferable to replace the guiding arrangement 9, which have the form of loops attached to the side of the block, by continuous tubes, thus creating rim guiding channels. 
     The invention is not limited to the embodiments shown above but can be varied within the framework of the following patent claims.