PROCESS AND EQUIPMENT FOR MANUFACTURING IN-SITU CONCRETE MONOLITHIC PILES WITH NON-UNIFORM SECTION

Abstract: In the course of the process a pipe equipped with advancing means is driven into the soil and when pulling it upwards, an after setting material is filled in through the pipe into the cavity remaining on the place of the pipe at a pressure at least partly exceeding the atmospheric pressure, while the advancing means being releasably connected to the lower end of the pipe is left to remain in the soil, which process comprises driving a cavity forming means (9) into the soil for forming a cavity at the planned upper end portion of the pile (1) to be manufactured, and for preventing the so formed cavity from rushing together, when pulling up the said cavity forming means (9) forming a cavity (17) in the soil, having a larger diameter than the diameter (d) of the pile (1) and being coaxial to the longitudinal geometrical axis of the pile (1), simultaneously with pulling up the cavity forming means (9) or immediately thereafter, filling the cavity with after-setting material, contacting this latter with the material of the other part of the pile (1) before both of them are hardened, and by letting the masses harden and thereby fix together to form a pile (1) having an upper part of larger diameter (D) than the diameter (d) of its lower portion (2). The equipment for carrying out the above process is characterized by comprising at the upper end of the pouring pipe (6), on the place of the planned end portion of the pile (1) to be manufactured, a cavity forming means (9) surrounding the pouring pipe (6) and having a larger diameter (D) than that of the pouring pipe (6), or comprising a cavity forming means (9) formed by a flaring part of the pouring pipe (6), the lower portion (10b) of which is provided with an inclined surface narrowing downwards and extending to the mantle of the pouring pipe (6).

Description: PROCESS W EQUIPMENT POR MANUFACTURING IN-SITU CONCRETE MONOLITHIC PILES WITH NON-UNIPORM SECTION r OMPI The invention relates to a process and an equipment for manufacturing in-situ concrete monolithic piles especially so- called micro-piles having a diameter of 50 to 150 mm, with non-uniform section. In structural engineering techniques there is well known to use micro-piles. The Hungarian patent specificatio No, 174 534 describes, among others, a foundation method using micro-piles wherein six to eight micro-piles are manufactured at intervals, which then are combined to a pile group functioning as a bearing construction, by preparing a monolithic concrete block linking up the upper ends of the micro-piles. The individual micro-piles are manufactured by driving a pipe equipped with an advancing means into the soil and, when pulling it back, filling the cavity remaining in the soil on the place of the pipe, with an after-setting material, in general with a fine-graine concrete fed through the pipe. The advancing means which is releasably joined to the lower end of the pipe, remains in the soil. Concreting is performed at a pressure of 3 to 8 att, A technological drawback of this pile foundation method consists in that, on the one hand, the upper portion of the micro-pile will be diminished, i.e. have a smaller cross-section in a length of 0.5 to 1,5 m, than the other part of the piles, and, on the other hand, in this portion also the density and. strength of the hardened concrete is lower because the over¬ pressure applied when forcing the concrete into the pipe, de¬ creases to a minimum when proceeding towards the upper portion and at the uppermost part there is practically no overpressure. The fact that, according to what is said above, the piles have the less strength at their upper end portion, involves a grave drawback. The force /loading/ admission to the piles takes place namely at the upper part - at the pile heads - thus involving undesirable side-effects /excentricity, moment/. Por this reason, the piles are usually more stressed in their upper end portion than in their other parts. Presumably, the piles are most susceptible also to column collapse in their upper portion in a length of 0,5 to 1.5 m, all the more because the soil strata near to the surface are in general more loose than those lying deeper, thus, also the sidewise supporting effect of the soil is lower near to the surface. The problems as detailed above may be eliminated by piles having at least identical or even higher loadability and bearing capacity at their upper portion than in the other parts of the piles, A possible means to increase the loadability consists in thickening the uppermost portion of the piles i.e. increasing their cross section as compared with the other part thereof. The said Hungarian patent specification No, 174 534 is containing a proposal to solve this problem, too. According to this, an intermediate, locally flaring part is formed on the pouring pipe at a distance from the upper end thereof, which consists in a cylindrical, barrel-shaped body and is prepared by welding an appropriately shaped steel plate to the outside of the pouring pipe. When pulling back the pouring pipe upwards, a cavity is supposed to remain behind the flaring part, which should have a larger diameter than that of the pouring pipe. In fact, OMPI however, such cavity of larger diameter can not be realized because the concrete would enter this cavity portion intended to have a larger diameter only with a delay and, until the lower end of the pouring pipe reaches the flaring area, the boundary walls of soil limiting the larger diameter cavity portion do in most cases rush together. Thus, a thicker portion at the upper end of the pile can in fact not be realized. The invention aims at developing a solution for manu¬ facturing in-situ concrete monolithic piles, especially micro- -piles having a larger diameter in their upper end portion, which solution is rational and results in an excellent quality end product. The invention is based upon the recognition that when the cavity corresponding to the pile portion of larger diameter, when being prepared and until it is filled with concrete, is protected from rushing together i.e. the boundary walls of the cavity of larger diameter do not remain without support, an excellent quality upper end portion of larger diameter can be manufactured with higher safety. The invention is further based upon the recognition that the larger diameter cavity can most expediently be formed by means of a widened upper portion of the pouring pipe either so that the pouring pipe itself is formed of a single part having altering cross-sections, or so that e.g. an additional widening sleeve is rigidly or releasably connected to the upper end of the pouring pipe. On the basis of the above recognitions, the aim as set is realized by a process according to the invention CMPI in the course of which a pipe equipped with advancing means is driven into the soil and when pulling it upwards, an after-setting material is filled in through the pipe into the cavity remaining on the place of the pipe at a pressure at least partly exceeding the athmospheric pressure, while the advancing means being re- leasably connected to the lower end of the pipe is left to remain in the soil, which process comprises driving a cavity forming means into the soil for forming a cavity at the planned upper end portion of the pile to be manufactured and for preventing the so formed cavity from rushing together when pulling up the said cavity forming means forming a cavity in the soil, having a lager diameter than the diameter of the lower part of the pile and being coaxial to the longitudinal geometrical axis of the pile, simultaneously with pulling up the cavity forming means or immediately thereafter filling the cavity with after-setting material, contacting this latter with the material of the other part of the pile before both of them are hardened, and by letting the masses harden and thereby fix together to form a pile having an upper part of larger diameter than the diameter of its lower portion. According to a preferred mode of realization of the process, the cavity forming means as a part of the pouring pipe or as a part connected thereto, is driven into the soil and pulled back together with the pouring pipe, while the after-setting material expediently concrete is pressed simultaneously into the cavity formed beneath the pouring pipe and beneath the cavity forming means, respectively. According to a further feature of the invention the after-setting material e.g. concrete is fed into the cavity formed in the soil directly from the pouring pipe O PI by means of the cavity forming means. The equipment for carrying out the process is characterized by comprising at the upper end of the pouring pipe, on the planned end portion of the pile to be manufactured, a cavity forming means surrounding the pouring pipe and having a larger diameter than that of the pouring pipe, or comprising a cavity forming means formed by a flaring part of the pouring pipe, the lower portion of which is provided with an inclined surface . narrowing downwards and extending to the mantle of the pouring pipe. According to a preferred embodiment of the equipment the cavity forming means is formed by a pipe-like element being displaceable over the pouring pipe and surrounding it at a distance, the lower portion of which is formed as a bottom ring with increased thickness provided with an inner inclined - expediently conical - bearing surface, and the pouring pipe has on its outer surface a collar having an outer diameter identical with the inner diameter of the cavity forming means and having on its lower end a lower inclined - expediently conical - surface which when driving the pipe into the soil is bearing against the inclined surface of the bottom ring of the cavity forming means. According to a further feature of the invention, on the top of the cavity forming means there is fixed a lug or the like for pulling the cavity forming means out of the soil. Expediently, the cavity forming means is fixed to the pouring pipe e.g. by welding and on the lower part of the cavity forming means there may be provided a hole for discharging the after-setting material, which can be opened and closed, respectively, and finally, the - upper portion of the cavity forming means may have a cylindrical form and its lower portion may have the form of a circular cone. The invention will be described below in details on the basis of the enclosed drawings illustrating the technological phases of the process and the advantageous embodiments of the equipments according to the invention. In the drawings Pigs. 1 to 4 show the sequence of operations while per¬ forming the process according to the inventio in the form of schematic sections; Pig. 5 is showing an embodiment of the cavity forming means together with the pouring pipe, in a schematic vertical section; Pig. 6 shows the vertical section of another embodiment of the cavity forming means connected to the pouring pipe; and Pig. 7 is an enlarged view of the same cavity formin means as shown in Pig. 6, without the pouring pipe. By performing the technological steps illustrated in Pigs. 1 to 3» there is manufactured a micro-pile with non-uniform section as shown in Pig. 4, having as a whole the reference numeral 1. At its lower end, the pile 1 has a head 5, then a lower cylindrical portion 2, an intermediate conical section 3 and an upper cylindrical portion 4. The diameter D of this latter is larger than the diameter d_ of the lower portion 2. The diameter d_ may be 50 to 130 mm while D may have a value between 70 and 200 mm; these are, however, exemplified values which can by no means delimit the scope of the invention. The conical head 5 is functioning as an advancing means for driving down the pouring pipe 6 shown in Pigs. 1 to 3. To a neck portion 7 of the head 5 there is fixed expediently by welding a steel insertion 8 serving as reinforcement for the micro-pile 1. It should be noted that throughout the present specification "concrete" has to be inter¬ preted as any kind of after-setting material, and "pouring pipe" has to be interpreted as a pipe for intrusion of any suitable kind of after-setting material. The portion 2 of the pile 1 shown in Pig. 4 has a diameter <1 and a length h, making a predominant part of the full length H of the pile. The length h, of the portion 4 having a diameter D may, in general, be 50 to 150 cm; the value of h_, must expediently be selected so that the widening of the pouring pipe 6 should start at a level where, due to the risk of the concrete to spring out when being pressed in, a significant overpressure can not be applied any more. The dimension h p of the intermediate conical section 3 has to be determined first of all in consideration of the ramming resistance. The constructional dimensions H, h,-h_, D and d. illustrated in Pig. 1 are of course identical with those illustrated in Pig. 4. Manufacturing of a pile 1 with non-unifomn section according to the invention, as shown in Pig. 4, is performed as follows /see Pigs. 1 to 3/: the pipe 6 together with the conical advancing head 5 and with the steel insertion 8 welded thereto is driven into the soil by means of some kind of ram engine known per se e.g. air hammer, as well as a ramming stand and auxiliary equipments not shown. In the case of the present embodiment, the pouring pipe 6 is widened at its upper end and, this widened portion of a diameter forms the cavity forming means 9 having an upper cylindrical portion 10a connected to the longer lower portion of the pouring pipe 6, having a diameter d_, through an intermediate conical part 10b. In other words, in this case the cavity forming means 9 is forming part of the pouring pipe 6. Evidently, the cavity forming means 9 is suitable to prevent the ground cavity formed from rushing together, as it supports the boundary walls of the cavity i.e. it protects the cavity from rushing together. The upper edge of the cylindrical portion 10a alines with the planned upper end of the pile 1, in the present case with the ground level -t. The neck portion 7 of the head 5 is surrounded with a rubber ring 11 which, by bearing against the inner surface of the pipe 6 prevents the underground water from penetrating into the inner space of the pipe 6, The head 5, the pipe 6 and the steel insertion 8 are driven into the soil as a whole unit. Driving takes place until, the head 5 of the pile 1 reaches the planned foundation level /depth H , This phase is shown in Pig. 1. In Pig. 2 there is shown that technological step of manufacturing the pile 1 wherein concrete 15 under overpressure is pressed in through a flexible tube 14 connected to the cavity forming means 9 at the upper end of the pouring pipe 6, by means of a quick-acting pipe-connection 12 and a cover 13 - the flexible tube 14 being connected to a concreting tube /not shown/ - and simultaneously the pouring pipe 6 together with the cavity forming means 9 forming part thereof is pulled upwards. Beneath the lower end of the pouring pipe 6 there remains in the soil a cavity 16 having a diameter el and beneath the cavity forming means 9 there remains a cavity 17 of a diameter D. The cavitiejs 16, 17 are coaxial to the vertical geometrical axis of the pile 1. The cavity 26 is of course immediately filled with the concrete leaving the pipe 6 under overpressure x the concrete outflow is illustrated by arrows £. According to the invention, also the cavity 17 beneath the cavity forming means 9 is filled in immediately i.e. while pulling the cavity forming means 9 up¬ wards, at a rate corresponding to the pulling rate; the concrete outflow is shown here by arrows G /see upper part of Pig. 2/. There are several possibilities to feed concrete 15 into the cavity 17: either an opening is provided e.g. in the wall of the intermediate part 10b which is closed when driving the pouring pipe 6 downwards and has to be opened when pulling the pipe upwards, thereby enabling the concrete 15 to flow out, or the concrete has to be fed in any other way into the cavity 17 is the soil. A number of possibilities to solve this problem will be described later. Thus, the pressurized concrete 15 perfectly supports the boundary walls of the cavity 17 so that it may not rush together. During the technological phase illustrated in Pig. 3 the pile 1 is almost fully prepared. During the period between the phases illustrated in Pig. 2 and in Pig. 3 the pouring pipe 6 is continuously pulled upwards while the concrete 15 is filling first the cavity 16 then the cavity 17 in the soil. The pouring pipe 6 is sliding through the concrete already pressed in the cavity 17 during concreting i.e. it may not be contaminated with soil and, when the pouring pipe 6 left point P where the lower conical part of the cavity 17 starts above the cavity 16, the concrete 15 previously fed in the outer part of - li ¬ the cavity 17, not yet hardened, comes to contact the concrete 15 leaving the lower end of the pouring pipe 6 according to the arrows g, along a surface marked with dotted lines k. The contacting or fusing surfaces k of both concrete masses are fully clean, perfectly free from contamination with soil. Both concrete masses are then of course unified to a single homogenous body which forms the upper part 4 of larger dia¬ meter D of the pile 1 /see also Pig. 4/. In Pig. 5 there is shown an embodiment of the cavity forming means 9 of the equipment, which is surrounding the upper end of the pouring pipe 6, fixed to the outer mantle of the pouring pipe 6 by e.g. welding. Also in this case, the cavity forming means 9 is formed by an upper cylindrical portion 10a and a lower conical intermediate portion 10b. With this solution, the concrete does not simply flow out of the space between the cavity forming means 9 and the outer mantle of the pouring pipe 6 into the cavity 17 shown in Pigs. 2 and 3 but it is conducted via a separate injecting ■ pipe 18 which discharges through a hole 19 from the cavity forming means 9, The hole 19 can be covered by a covering means 20 for the period when the pouring pipe 6 together with the cavity forming means 9 is driven into the soil as described above; the cover¬ ing means 20 prevents soil or ground water from penetrating into the injecting pipe 18. When, at the beginning of the concreting procedure the pouring pipe 6 and the cavity forming means 9 is started to be pulled upwards, the covering means 20 opens or is opened and thereby the concrete has a free way to flow towards the cavity 17 in the soil in the direction " of the arrow /see Pigs. 2 and 3/. Concrete is fed through the pouring pipe 6 according to the arrows £ as already described with reference to Pigs. 2 and 3. A further preferred embodiment of the equipment according to the invention is shown in Pigs. 6 and 7. With this solution, the cavity forming means 9 is releasably connected to the pouring pipe 6, however, it has the same function as the one described above: it forms a cavity of larger diameter in the soil at the upper end of the pile to be manufactured, and protects the freshly formed cavity against rushing together. As a result of filling the cavity with concrete, a pile with non-uniform section is formed: it has a wider portion at its upper end. In the embodiment according to Pigs. 6 and 7 the cavity forming means 9 having the form of a pipe, has an inwardly inclined thick-walled intermediate portion 10b ending in an edge 22 at its lower end, being provided in this case as a bottom ring and having an inner conical bearing surface 23 and a conical outer surface 24. Both surfaces 23 and 24 are inward¬ ly inclined. On the outer surface of the pouring pipe 6 at the planned end of the flaring part of the pile 1 /Pig. 4/ there is welded a collar 25, or connected thereto in any other way, having a maximum diameter almost identical with /or somewhat larger to/ the inner diameter D_ of the upper cylindrical portion 10a of the cavity forming means 9. The collar 25 has a conical bearing surface 26 narrowing down¬ wards, Which is lying against the inner conical bearing sur- face 23 of the bottom ring 10b. There is no other connection between the pouring pipe 6 and the cavity forming means 9. In Pig. 6 there is shown the ramming head 27, known per se, marked as a whole with the reference numeral 27. ID Pig. 7 there is shown a lug 28 enabling the cavity forming means 9 to be pulled up. Manufacturing of a pile with non-uniform section takes place by means of the equipment shown in Pigs. 6 and 7 as follows: The cavity forming means 9 is pulled over the pouring pipe 6- efore driving this latter into the soil, and they are jointly driven into the soil. During driving the pipe 6 down¬ wards, the conical bearing surface 26 of the collar 25 is bearing against the inner conical bearing surface 23 of the bottom ring 10b of the cavity forming means 9, thus, the pouring pipe 6 pulls the cavity forming means 9 downwards and, when driving is ended, the cavity 17 is formed in the soil as shown in Pigs. 2 and 3. When carrying out concreting as described above, the cavity forming means 9 remains stationary while the pipe 6 is pulled upwards and the pouring pipe 6 is lifted until the lower end of the pouring pipe 6 alines with the lower end of the bottom ring 10b. Prom now on, the cavity forming means 9 is pulled further upwards together with the pouring pipe 6 by carrying it at the lug 28, at a uniform ' speed, so that the cavity 17 in the soil is filled with concrete /see Pigs. 2 and 3/ and there is formed the pile 1 having an upper portion 4 of larger diameter, as shown in Pig. 4. When e.g. only a samll heigth /length/ of the wider W VYiirie<_. upper portion 4 is needed, the cavity forming means 9 may eventually remain in the soil. The advantages of the invention may be summarized as followsi The piles with non-uniform section as manufactured by the aid of the process and equipment according to the invention require only a minimum excess material and yet have a higher load bearing capacity than piles with uniform section of the same length, namely the concrete i.e. material of the first said piles is optimally utilized. At the part of the piles being most sensitive to horizontal load - where due to an only weak support by the soil there is a minimum fixing /clamping/ effect - the load bearing capacity against shearing forces is significantly increased. Also the sinking characteristics of the piles are better. Namely, the pile has a maximum and homogenous cross-section due to the process according to the invention at that part where maximum stresses arise. Due to the manufacturing techniques according to the invention, the concrete quality is high also at the upper end of the pile, the raw concrete parts are excellently unified after hardening. The increased sinking characteristics are due to the fact that as a result of the form of the cavity forming means, the pile has an additional conical ring-like bearing surface even there where sinking movement has its maximum, i.e. at deeper lying parts of the pile, the effects of resisting force at the peak- point and friction on the mantle become effective. The invention is of course not limited to the preferred embodiments described above but can be realized in many-other ways within the scope of the claims. It is understood that not only the so-called "micro-piles" but any other type of in-situ monolithic concrete piles can be manufactured by means of the process and equipment according to the invention. Although the definition "cavity forming means" is used through¬ out the specification, under cavity forming means there is ment a means which also prevents the cavity formed by the same means from rushing together. OMPΓ_

Claims: CLAIMS : 1. A process for manufacturing in-situ concrete monolithic piles with non-uniform section in the course of which a pipe equipped with advancing means is driven into the soil and, when pulling it upwards, an after-setting material is filled in through the pipe into the cavity remaining on the place of the pipe at a pressure at least partly exceeding the athmospheric pressure, while the advancing means being releasably connected to the lower end of the pipe is left to remain in the soil, which process comprises driving a cavity forming means /9/ into the soil for forming a cavity at the planned upper end portion of the pile /I/ to be manufactured, and for prevent¬ ing the so formed cavity from rushing together, when pulling up the said cavity forming means /9/ forming a cavity /17/ in the soil, having a larger diameter than the diameter /d/ of the lower part of the pile /l/ and being coaxial to the longi¬ tudinal geometrical axis of the pile /l/, simultaneously with pulling up the cavity forming means /9/ or immediately there¬ after, filling the cavity with after-setting material, contacting this latter with the material of the other part of the pile /I/ before both of them are hardened, and by letting the masses harden and thereby fix together to form a pile /I/ having an upper part of larger diameter /D/ than the diameter /d/ of its lower portion /2/. /Pigs. 1 to 4/ 2. A process as claimed in claim 1 wherein the cavity forming means /9/ as a part of the pouring pipe /6/ or as a part connected thereto, is driven into the soil and pulled back together with the pouring pipe /6/, while the after-setting material expediently concrete /15/ is pressed simultaneously into the cavity /16, 17/ formed beneath the pouring pipe /6/ and beneath the cavity forming means /9/ » respectively. 3. A process as claimed in claim 1 or in claim 2 where¬ in the after-setting material e.g. concrete /15/ is fed into the cavity /17/ formed in the soil directly from the pouring pipe /6/ by means of the cavity forming means /9/. 4. Equipment for carrying out the process claimed in any of claims 1 to 3 comprising, at the upper end of the pouring pipe /6/, on the place of the planned end portion of the pile /l/ to be manufactured, a cavity forming means /9/ surrounding the pouring pipe /6/ and having a larger diameter /D/ than that of the pouring pipe /6/, or comprising a cavity forming means /9/ formed by a flaring part of the pouring pipe /6/, - the lower portion /10b/ of which is provided with an inclined surface narrowing downwards and extending to the mantle of the pouring pipe /6/. 5» Equipment as claimed in claim 4 wherein the cavity forming means /9/ is formed by a pipe-like element being displaceable over the pouring pipe and surrounding it at a distance, the lower portion /10b/ of which is formed as a bottom ring with increased thickness provided with an inner inclined - expediently conical - bearing surface /23/ » and the pouring pipe /6/ has on its outer surface a collar /25/ having an outer diameter identical with the inner diameter /D/ of the cavity forming means /9/ and having on its lower end a lower inclined - expediently conical - surface /26/ which, when driving the pipe /6/ into the soil, is bearing against O ?l " the inclined surface /23/ of the bottom ring /10b/ of the cavity forming means /9/. /Pigs. 6 and 7/ 6. Equipment as claimed in claim 5 wherein on the top of the cavity forming means /9/ there is fixed a lug /28/ or the like for pulling the cavity forming means /9/ out of the soil. /Pig. 7/ 7. Equipment as claimed in claim 4 wherein the cavity forming means /9/ is fixed to the pouring pipe /6/ e.g. by - welding. /Pig. 5/ 8. Equipment as claimed in any of claims 4 to 7 where¬ in on the lower part of the cavity forming means /9/ there is provided a hole /19/ or discharging the after-setting material /15/, which can be opened and closed, respectively. /Pigs. 2 and 5/ 9. Equipment as claimed in any of claims 4 to 8 wherein the upper portion /10a/ of the cavity forming means /9/ has a cylindrical form and its lower portion /10b/ has the form of a circular cone.

Inventors: BABOS LASZLO, DOERNER HENRIK, FUEZESI PAL, KANYO MIKLOS, KERTESZ GABOR, BABOS, LASZLO, DOERNER, HENRIK, FUEZESI, PAL, KANYO, MIKLOS, KERTESZ, GABOR
Applicants: DUNA TISZA KOEZI ALLAMI EPITOE, DUNA-TISZA KOEZI ALLAMI EPITOEIPARI VALLALAT
Application year: 1984
Main classification: E02D5
IPC codes: E02D5