AN IMPROVED PILING METHOD

Abstract: To manufacture a pile (9, 14) which is intended to take compressive as well as tensile loads or to serve as a reinforcement member in soils, a strip (4) is wound off a roll (3) of strip material and is carried through a rotating-roller shaping unit (6) wherein the strip (4)is shaped by rollers and, if desired, in such a mannet that it forms a bend in its direction of advancement. A pile (9, 14) thus shaped is driven from the roller shaping unit (6) by means of pressure in arbitrary directions into the mass of an earth layer (10, 13, 16, 19). Upon attainment of the desired depth of penetration and/or pile length the pile (9, 14) is severed at or close by the surface of the earth layer (10, 13, 16, 19).

Description: The subject invention concerns a method of manufacturing piles in situ immediately prior to the use thereof for foundation, ground reinforcement or soil stabilization purposes. In conventional piling operations piles made from concrete, wood or steel are used as a rule. Whichever type of pile that is used, the length of the manufactured pile is generally restricted, although the pile lengths may vary from some meters up to several tens of meters. It is quite difficult to handle and manipulate very long piles and to drive them down into the ground requires machinery equipped with a high tower, Shorter piles must be formed with interconnecting means allowing the piles to be joined together, and such interconnecting means often increase the pile manufacturing costs considerably, in addition to which the operations of joining the pile sections together during the piling work is quite time-consuming. In conventional piling operations the piles are usually driven down into the ground with the aid of some kind of percussion equipment. Such equipment generates heavy vibrations and noise when in use, which could constitute an environmental disturbance. The subject invention provides a method allowing various types of piling operations to be performed in a considerably more simple and therefore less expensive manner while at the same time vibrations and noise are reduced to a minimum. The method in accordance with the invention is characterized therein that a strip, preferably made from steel, is wound off a roll and is carried through a rotating-roller shaping unit of a kind known per se, in which unit the strip is subjected to plastic deformation in its lengthwise extension, whereby the strip is imparted a desired predetermined cross-sectional profile configuration, and in that the pile thus shaped, when leaving the roller shaping unit, is driven downwards or laterally into an earth layer by means of pressure on said pile and in that upon attainment of the desired penetration depth and/or the desired pile length the pile is severed level with or close to the ground surface. Various embodiments of the pile in accordance with the invention and the method of driving the pile into the ground will be described in closer detail in the following with reference to the accompanying drawings, wherein Fig. 1 is a lateral view of a utility vehicle fitted with the piling equipment in accordance with the invention. Fig. 2 is a cross-sectional view through a road embankment stabilized by piling, Fig. 3 is a sectional view through a slope stabilized in a similar manner, Figs. 4a through 4e show, by way of example, end views of various piles in accordance with the invention, Fig. 5 is a schematical plan view of an arrangement including four installation shafts with an intermediate "pile wall", and Fig. 6 is a lateral view of a modified embodiment of the utility vehicle illustrated in Fig. 1. Fig. 1 illustrates a vehicle 1 serving as a utility vehicle when performing the piling operations. The vehicle is equipped at its upper portion with a roller stand 2 which supports a roll 3 of a strip material 4. The strip 4 is carried over a deflector rail 5 and fed into a rotating-roller shaping unit 6. The basic structure of this unit is of a prior-art nature and includes pairs of rollers 7 which are designed to shape the initially flat strip blank during the successive advancement of the strip 4 into the desired predetermined cross-sectional profile configuration. A pair of driving wheels 8 formed integrally with the shaping unit 6 are positioned one on either side of the shaped strip. The purpose of the driving wheels 8 is to drive the pile 9 thus shaped by pressing it down to the desired penetration depth in the underlying earth layers 10. Below the driving wheels 8 a severing means 11 is located by means of which the pile 9, when having been driven down into the desired position, may be cut off at ground level. The severing means may be e.g. hydraulically operated scissors. The utility vehicle 1, which may be of moderate size, could then be moved to the next place of piling. The shaping procedure is a rapid one. The strip 4 may be advanced at the speed of some ten meters per minute or even more. The pile 9 thus formed successively, may be installed in any desired direction. Fig. 2 shows a situation according to which the earth layer 13 underlying a road embankment 12 need to be reinforced/stabilized. With the use of the shaping unit 6 it becomes possible, in accordance with the teachings of the invention, to form piles 14 from the strip 4. While being driven down into the ground on one side of the road embankment 12 the pile 14 follows a curve in the vertical plane and thus it reappears from the ground on the opposite side of the road embankment 12. To anchor the ends of the piles 14 a shaft 15 may be excavated laterally of the embankment 12. In this case, the primary purpose of the piles 14 is to absorb tensile stress and in this manner they act as soil stability reinforcement means. The installment of such curved profiled piles 14 in accordance with the invention reduces the need of e.g. load-supporting embankments. Owing to the considerable rigidity of the piles 14 they will attribute considerably to the resulting increased stability of the earth layer 13. The result is that e.g. the effects of the dynamic load caused by moving vehicles, such as trains, lorries and similar vehicles, which load is transferred to the earth layer 13, may be reduced to a considerable degree. Similar soil stability improving measures may be taken also in layers of loose and unconsolidated soils in order to reduce the effects of detrimental vibrations due to earthquakes. Fig. 3 shows one exemplary application of the novel piling technique used for stabilization of a slope 16. The dash-and-dot line 17 marks the estimated potential sliding curve of sliding masses of earth in the slope 16. Conventional piling using percussion techniques often cannot be recommended in situations similar to the one illustrated because of the vibrations which are generated under such circumstances and which cause displacement of considerable masses of earth during the piling operation. The stability of the slope could possibly be improved by providing some kind of ground anchors inside the mass of the slope 16. However, the installment of such anchors is very costly. In accordance with the teachings of the invention a couple of piles 9 could instead be forced down into the mass of the slope as illustrated in Fig. 3 without generation of vibrations or displacement of large masses of earth. As an alternative to or in addition to these piles 9 one or several curved piles 14 may be driven into the slope 16 in the manner indicated in Fig. 3, either from the front or from above. The method and equipment in accordance with the invention thus allow improvement of slope stabilitity in a manner which is both less expensive and safer than the conventional technique used hitherto. Figs. 4a through 4e show examples of various pile profile configurations. From a geotechnical viewpoint it is essential that the pile possesses maximum rigidity and maximum surface area. Fig. 4d illustrates an embodiment the profile configuration of which is intended to be obtained from a strip which, already when wound into the roll 3, forms a closed shape. As an alternative to driving a thus shaped pile into the ground it is possible to force it laterally into an earth layer in which case the shaping unit is positioned in a shaft. As soon as the profiled strip is in position in the ground in such a manner that after severing of the strip it extends for instance between two shafts, it becomes possible to apply an excess pressure in the interior of the strip, whereby the strip expands into a tubular shape. The leading end of the profile strip should be closed in a suitable manner, Fig. 4e shows an embodiment according to which the strip 4 is given a profile configuration allowing one section, when positioned in the ground in order to serve as a pile, to be hooked onto the adjoining section in the manner of a sheet pile, and with the aid of such pile sections it becomes possible successively to form a sheet pile wall. Fig. 5 represents schematically an arrangement consisting of four shafts 18 which are excavated in a circular array and which are spaced a predetermined distance apart. From the excavated shafts 18 piles 14 are driven laterally into the earth in the manner taught by the invention, the shaping unit 6 then being set in a manner causing the piles to extend along a predetermined curved line in the horizontal plane from one well or shaft to the next. In this manner it becomes possible to form "rib cage" pile walls which facilitate excavation operations in the entire ground area 19 interiorly of the shafts 18. Such "rib cage" structures could also be erected with vertically directed piles 14. Fig. 6 shows a somewhat modified utility vehicle 1a. The roll 3 of strip material is enclosed inside a cartridge 20 mounted on the roller shaping unit 6, the latter being articulated to an extension arm 21 on the vehicle 1a. The roller shaping unit 6 and the cartridge 20 are mounted for joint pivotal movement by means of a hydraulic piston-and-cylinder unit 22, allowing them to assume various angular positions, either inwards towards the utility vehicle 1a or outwards, as illustrated in the drawing figure. This arrangement facilitates the insertion or forcing downwards of the pile 9, 14 into the ground under the conditions outlined above. The pile 9, 14, in its various applications, is primarily intended to be used in loose soils, such as normally-consolidated clay. However, it could also be used in more compact types of soil. The method in accordance with the invention, when applied in clay soils, makes use of the principle that the force required when the pile 9, 14 is driven into the ground is considerably smaller than the load-absorbing capacity of the pile. This is due to the "breaking up" of the soil with consequential reduction of the strength which occurs as a result of the installation of the pile. The force required to drive the pile downwards or inwards thus is reduced, which means that the equipment could be made accordingly smaller and more compact. By means of reversing pulses the resistance of the pile against the driving-down into the clay is further reduced because of the increased "breaking up" of the clay. However, in time the clay settles and resumes its original strength. By measuring the resistance of the pile against being driven down it becomes possible to determine the load-bearing capacity of the pile. A further application of the pile in accordance with the invention is as an anchoring member to resist lateral pulling forces, e.g. as sheet pile anchoring member. Hitherto, anchorage of this kind has consisted primarily of stays (wires) which are secured in rock by means of drilling or in other types of anchoring bodies (injection zone). Forcing a pile 14 laterally into the soil in the manner in accordance with the invention provides a more simple and less expensive solution to this problem. The invention is not limited to the embodiments described in the aforegoing and illustrated in the drawings but could be modified in a reduce the weight of the strip 4 and in order to increase the efficiency in certain types of soil the strip 4 could be perforated prior to or in connection with the profile-shaping process. During the shaping process it is also possible to form the strip 4 with bumps or projections. The strip 4 could be pre-treated prior to the shaping process. It could, for instance, be covered with a coat of paint or it could be electroplated. Other materials than steel could be used, such as aluminium.

Claims: 1. A method of manufacturing piles (9, 14) in situ immediately prior to the use thereof for foundation, ground reinforcement or soil stabilization purposes, characterized therein that a strip (4), preferably made from steel, is wound off a roll (3) and is carried through a rotating-roller shaping unit (6) in which the strip (4) is subjected to plastic deformation in its lengthwise extension, whereby the strip is imparted a desired predetermined cross-sectional profile configuration, and in that the pile (9, 14) thus shaped, when leaving the rotating-roller shaping unit (6), is driven downwards or laterally into an earth layer (10, 13, 16, 19) by means of pressure on said pile and in that upon attainment of the desired depth of penetration and/or the desired pile length the pile is severed level with or close by the ground surface. 2. A method as claimed in claim 1, characterized therein that the rotating-roller shaping unit (6) is set so as to cause the pile (14) to extend in a bend in its direction of advancement. 3. A method as claimed in claim 1, characterized therein that the pile (14) is driven into the earth layer (13, 16) in any desired direction, such as into a slope (16) or into a wall of a shaft excavated in the ground. 4. A method as claimed in claim 1, characterized therein that the strip (4) is perforated during the rotating-roller shaping process. 5. A method as claimed in claim 1, characterized therein that the strip (4) is formed with bumps or projections during the rotating-roller shaping process.

Inventors: ANDREASSON, BO
Applicants: ANDREASSON, BO
Application year: 1988
Main classification: E02D7
IPC codes: E21B19, E04H17, E02D3, E02D5, E02D7