RU2318960C2 - Method for cast-in-place pile erection - Google Patents

Abstract

FIELD: construction, particularly to erect piles in foundations in the case of insufficient borehole wall stability, particularly to construct foundations of buildings under construction and reconstruction.

SUBSTANCE: method involves drilling borehole; supplying hardening material in the borehole; compacting thereof by electric charge application along with upward exciting zone movement. Borehole is drilled by auger drilling assembly having electric discharge device connected to one end thereof so that it may move forwards. Hardening material is injected in well along auger drilling assembly ribs. As auger drilling assembly reaches borehole bottom the drilling assembly is lifted without rotation thereof in well for height equal to 0.8-1.5 well diameters. After created volume filling with continuously supplied material, discharge device is moved forwards and electric discharge is applied to material. After that auger drilling assembly lifting and electric charge supply operations are repeated up to borehole filling for the full borehole depth. As auger drilling assembly is lifted drilling assembly may be rotated in direction opposite to that of borehole drilling to fill space created after auger drilling assembly lifting with hardening material. Filling completion moment corresponds to time when borehole intake is stopped.

EFFECT: increased pile quality, load-bearing capacity and pile body material strength, simplified pile production.

2 cl, 1 dwg, 2 ex

Description

The invention relates to construction, and in particular to technology for the construction of piles in soils where the stability of the walls of boreholes is not provided, can be used for pile foundations of new buildings and structures under construction, reconstructed old buildings, as well as structures for various purposes.

A known method of erecting a stuffed pile (certificate of authorship 1441847, M.cl. E02D 5/44, 1987), including the installation of reinforcement and the supply of hardening material to a hole previously passed by a pneumatic punch, with a diameter smaller than the diameter of the created pile, and subsequent compaction of the hardening material. Moreover, at the same time as the installation of reinforcement, the well is expanded over its entire height. The supply of hardening material is carried out together with the formation of camouflage broadening by a series of high-voltage electric discharges, the amount of which is determined from the required radius of the camouflage broadening per one discharge, the rate of accumulation of irreversible deformations, soil, and the hardening material is compacted along the height of the well with high-voltage electric discharges.

This method has significant drawbacks: complexity, and sometimes it is impossible to apply when building piles in structurally unstable soils, as these soils are being restructured.

A known method of construction of a printed pile (application PCT RU No. 91/009941, M.cl. E02D 5/44). This method includes drilling a well, installing an inventory electric spark gap, supplying a hardening electrically conductive material to the well, exciting high voltage electric discharges therein using a spark gap with moving the excitation zone from the bottom up and then removing the spark gap.

However, this method has the same significant disadvantages as the previous invention.

Closest to the claimed invention is a method of erecting a printed pile, including drilling a well, installing an electric spark gap, supplying a hardening electrically conductive material to the well, exciting high voltage electric discharges therein using a spark gap with moving the excitation zone from bottom to top. Moreover, after removing the drilling projectile from the well, a casing with a lost plug is installed in the well. An electric spark gap and a pipe for supplying hardening material are installed in the casing cavity along the axis of the well. Then, the casing is immersed until the bottom of the well, after which the cavity of the casing is filled with electrically conductive hardening material and the casing is moved upward while the hardening material is fed into the well and displaced into the annulus, and the discharger is moved upward together with the casing or independently of her.

However, this method is also not reliable enough, since when it is used in soft soils during the extraction of a drill, the soil will inevitably spill and sludge will form at the bottom of the well, in addition, the use of a casing with a lost plug installed at the end of the casing leads to the complexity of the method.

The objective of the invention is to create a new method of construction of a printed pile, which would allow to obtain high-quality piles, to provide high bearing capacity and strength of the material of the trunk, as well as to simplify the production process.

This problem is solved by the fact that during the construction of a stuffed pile, which includes drilling a well, supplying a hardening material to it, compacting it using electric discharges with moving the excitation zone from bottom to top, drilling is carried out with a screw projectile, at the end of which an electric spark gap is placed with the possibility of extension, moreover, the supply of hardening material into the well is carried out according to the flanges of the screw shell, after the shell reaches the bottom of the well, it is raised without rotation in the well to a height of 0.8-1.5 diameters wells, and after filling the formed volume with continuously supplied hardening material, the spark gap is extended and electric discharge is carried out, then the operations of raising the projectile and electric discharges are repeated until the well is filled to the full depth.

Moreover, after each elevation of the auger projectile, the apparatus can rotate in the opposite direction of drilling until it is filled with hardening material, the void formed after the lift is filled, and the filling moment is determined when the absorption of the hardened material is stopped.

Such a new set of essential features of a technical solution makes it possible to produce a packed pile in soils where the stability of the walls of boreholes is not ensured, as well as in structurally unstable soils (silts, peat, water-saturated peat soils, etc.).

On figa shows the drilling of a well 1 with a screw shell 2 with a spark gap 3 located at its lower end; on figb shows a straight-line (without rotation) the rise of the screw projectile 2 to a height of (0.8-1.5) d - well diameter; on figv shows the supply of hardening material 4 on the flanges of the screw projectile 2, which can be carried out by gravity, under pressure or by rotating the tool 2 in the opposite direction relative to the rotation during drilling, until the volume under the projectile is filled to a height (0.8-1.5) d; and operation of the arrester; 2g shows the next projectile rise to a height of (0.8-1.5) d from the surface of the hardening material 4; on fig.2d shows the resulting printed pile.

The method is as follows. Excavate a cylindrical well 1 with a screw drill 2. At the same time as drilling, excavation takes place. After the drill has passed to the required depth, it is lifted to a height (0.8-1.5) of the diameter of the obtained well 1. A height equal to (0.8-1.5) of the diameter of the obtained well is determined empirically, based on the condition of soil disintegration in the resulting wells, when lifting the projectile. Its lower limit is taken for soils that are weak with respect to crumbling, for example, dusty sand, nutrients, and the like. The highest limit is defined for cohesive soils. Simultaneously with the lifting of the drill, the hardening material 4 begins to flow, which can be fed by gravity due to gravitational forces, pressure applied to the hardening material, and after the shell reaches the desired height, the drill can be rotated in the direction opposite to the drilling direction to accelerate the filling of raising the volume under the projectile 2 and creating some pressure to better fill the above volume. Then an electric discharge is produced in this volume, which is explosive in nature with great electrodynamic forces acting in all directions. At the same time, part of the hardening material 4 is introduced into the bottom and side walls of the well, strengthening them, and the level of hardening material occupies a position below the original. A drill auger is raised to a height (0.8-1.5) of the diameter of the well from the level of the hardening material formed after the first discharge. Then, the above operations (lifting and discharge) are repeated until the well is filled to the full depth.

Example 1. Piles were erected 10 m long with a screw auger, at the end of which a spark gap was mounted with the possibility of extension, connected by a low-inductance cable to an electric-discharge station (capacitive energy storage) 20 kJ, the outer diameter of which was 230 mm. As a supporting layer, dusty sand of medium density, not water-saturated, was used. After passing the projectile to a depth of 10 m, it was lifted to a height of 184 mm, which is 0.8 of the diameter of 230 mm, since it is precisely this diameter that the well has, which is formed by a drill, and at the same time feed hardening material. After the drill stopped, it was rotated in the opposite direction to the drilling. Hardening material was supplied until the absorption of the material ceased, which indicated the complete filling of the cavity under the drill. After that, a discharge was made. Then the drill was lifted again to a height of 184 mm, at the same time filling the vacated volume, and all operations were repeated until the well was fully filled 10 meters. At the same time, the pile has a diameter significantly exceeding the initial one obtained during drilling.

After the set of strengths, static tests of the manufactured piles were carried out, which showed the bearing capacity of piles of 45 tons.The expected bearing capacity of piles, calculated according to existing methods, is 35 tons. This indicates that the proposed method of construction of piles allowed to increase the bearing capacity of piles up to 30%.

It is recommended that these operations be continued until the entire soil layer has passed, after which they again change the direction of displacement of the lower end of the casing and the spark gap relative to each other in the well and repeat the previously described method operations until the pile shaft is completely manufactured. As a result, a stuffed pile is produced with increased bearing capacity and in less time than other known methods.

Example 2. Carried out the construction of piles 12 m long with a screw auger, at the end of which a spark gap is mounted with the possibility of extension, connected by a low-inductance cable to an electric-discharge station (capacitive energy storage) 25 kJ, the external diameter of the projectile is 250 mm. As a bearing layer, sandy clay soil was used. After passing the projectile to a depth of 12 m, it was lifted to a height of 375 mm, which is 1.5 from a diameter of 250 mm (since this is the diameter of the well that is formed by the drill), and at the same time the hardening material is supplied. After the drill stopped, it was rotated in the opposite direction to the drilling. Hardening material was supplied until the absorption of the material ceased, which indicated the complete filling of the cavity under the drill. After that, a discharge was made. Then the drill was raised again to a height of 375 mm while filling the vacated volume, and all operations were repeated until the well was completely filled 12 meters. At the same time, the pile, as in the first example, has a diameter significantly exceeding the initial one obtained during drilling.

After the set of strengths, static tests of manufactured piles were carried out, which showed the bearing capacity of piles of 65 tons.The expected bearing capacity of piles in the manufacture according to existing methods of 45 tons.This indicates that the proposed method of construction of piles allowed to increase the bearing capacity of piles up to 30%.

It is recommended that these operations be continued until the entire soil layer has passed, after which they again change the direction of displacement of the lower end of the casing and the spark gap relative to each other in the well and repeat the previously described method operations until the pile shaft is completely manufactured. As a result, a stuffed pile is produced with increased bearing capacity and in less time than other known methods.

Claims (2)

1. A method of erecting a stuffed pile, including performing a well by drilling, supplying a hardening material to it, compacting it using electric discharges with moving the excitation zone from bottom to top, characterized in that the drilling is carried out by a screw projectile, at the end of which an electric spark gap is placed with the possibility of extension, moreover, the supply of hardening material into the well is carried out according to the flanges of the screw projectile, when the projectile reaches the bottom of the well, it is raised without rotation in the well to a height of 0.8-1.5 diameter of the well ins, and then fill the volume continuously pushing material fed hardening arrester and electrical discharge is performed and then repeated lifting operation of the projectile and the electrical discharge to fill the entire depth of the well. 2. The method of erecting a stuffed pile according to claim 1, characterized in that after each lifting of the auger projectile, the projectile can rotate in the opposite direction of drilling until it is filled with hardened material, the void formed after lifting is filled, and the moment of filling is determined when the absorption of the hardened material is stopped.

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