RU2139975C1 - Method for building cast-in-place piles and fortifying their bases - Google Patents

Abstract

FIELD: construction engineering. SUBSTANCE: method can be used in building of crushed-stone and sand-filled cast-in-place piles and in fortifying their bases. According to method, building of cast-in-place piles and fortifying their bases includes drilling of bore-holes, filling of bore-hole with crushed-stone and/or sand, vibrating compaction of material. Portion of material is poured to bottom of bore-hole. Lowered into bore-hole is vibrating compactor. Compaction of crushed-stone and/or sand is effected over entire height and area of material at operation of low frequency equal to 6-15 Hz and high amplitude equal to 3-20 mm. Vibrating compactor is removed from bore-hole at high frequency equal to 20-45 Hz and low amplitude equal to 0.3-1.5 mm. In operation with unstable ground, before filling bore-hole with loose material, casing pipe is sunk into bore-hole, and after filling bore-hole with loose material, casing pipe is partly lifted with subsequent compaction of material into ground below base of casing pipe. After that, casing pipe is again sunk. Upon that, vibrating compactor is removed from bore-hole at high vibration frequency equal to 20-45 Hz and low amplitude of 0.3-1.5 mm. Framework is now lowered into bore-hole and concreting is carried out. Aforesaid method allows for doing away with using non-mobile and operationally expensive pile-driving plants, diesel-hammers, and compactors. Load-bearing capacity of cast-in-place piles is also increased. EFFECT: higher efficiency. 2 cl, 10 dwg

Description

 The invention relates to the field of construction and can be used in the construction of crushed stone and sand piles of permanent and temporary foundation structures and artificial foundations; in the construction of drill posts of any diameter for bridge building and civil engineering, in the construction of foundations using the "wall in soil" method, as well as in the construction of berth walls and underwater hydraulic structures.

 There is a method of constructing rammed piles, including sinking with the help of a punch of deviated wells, followed by compaction with inert material and concreting of the wellheads, while inert material is poured into the well in portions equal to 1 / 3-1 / 2 of the length of the punch, followed by compaction (RU, 2026926, CL E 02 D 27/08, 01/20/95).

 Without detracting from the advantages of the known technical solution, one can note its inherent disadvantages. So the method is unacceptable in the case of water-saturated sandy soil, when it is not possible to form a well with a punch, since when removing the punch, the filtration flow to the center of the well will destroy the compacted zone, and the well will float. In the case of applying this method in weak cohesive soils and soils with a small degree of lithification, a similar effect will be manifested due to thixotropic dilution of the soil.

 The closest technical solution is the method of constructing printed piles and strengthening their foundations, including the formation of a well, filling the well with hard bulk material, vibration compaction and vibration removal of the vibro-stamp (RU, 2060321, 05.20.96).

 Without detracting from the advantages of the known method, it can be noted that it is not effective enough in strengthening the foundations during the construction of crushed stone and sand piles.

 The objective of the invention is to increase the bearing capacity of bored piles on the ground while at the same time reducing their length, diameter or quantity in a pile field, as well as ensuring environmental friendliness of work both in open areas and in settlements. The problem is solved due to the fact that "in the method of constructing printed piles and strengthening their foundations, including forming a well, filling a well with a rigid bulk material, vibration compaction and vibration removal of a vibratory stamp, according to the invention, crushed stone and / or sand, a portion of which is used as a rigid granular material fall asleep at the bottom of the well, lower the vibro-stamp into the well, rigidly connected through the rod to the vibrator and in the mode of low frequency of oscillations of 6 - 15 Hz and high amplitude of 3 - 20 mm, ramming rubble and / and whether sand and its compaction over the entire height and area, and vibration damping is carried out at a high vibration frequency of 20 - 45 Hz and a small amplitude of 0.3 - 1.5 mm.

 At the same time, when working on unstable soils, before filling the well with bulk material, the casing is immersed into it and the well is cleaned up, and after filling the well with bulk material, the casing is partially deepened by the amount of contact of the filled gravel and / or sand with the walls of the well and rammed it into the ground below the bottom of the casing pipe, then again deepen the casing pipe to the design level and, at a high oscillation frequency of 20 - 45 Hz and a small amplitude of 0.3 - 1.5 mm, a broshtamp, after which they again clean the well to the bottomhole level of the casing, lower the frame into it and make concreting.

 The technical result provided by the invention is that the method provides volumetric liquefaction of the soil with its subsequent compaction and ramming hard material into it to a predetermined depth, which increases the bearing capacity of the soil base by 3 to 4 times or more, depending on the fraction of crushed stone and the exposure time of the installation on the ground, while due to a sharp decrease in internal friction and weakening of adhesion, hard material is immersed in a liquefied soil due to gravity and component detecting vibration exposure. After the formation of the shaft of the crushed stone pile is completed, the vibrations are transferred to the low-frequency impact mode, which ensures the maximum bearing capacity of the soil base possible for the given soil conditions and the size of the crushed stone pile.

 The invention is illustrated by drawings, where in FIG. 1 shows an installation for implementing the method of construction of crushed stone and sand rammed piles and strengthening their bases, FIG. 2 - stamping feathers of a vibratory stamp, side view, in FIG. 3 is the same plan view, in FIG. 4 to 6 depict the stages of the sequence of construction of rammed piles; FIG. 7 - 10 - stages of the technological scheme of the method of strengthening pile foundations and the construction of printed piles using casing and reinforcing cages.

Installation for the construction of crushed stone and sand piles and pile foundations contains a vehicle 1 with a lifting mechanism 2, a rod 3, a hydraulic vibrator 4, equipped with a hydraulic headgear 5, and shock absorbers 6 with gripping eyebolts 7, a feathery spatial vibro-stamp 8 with stamping feathers 9, hydraulic hoses 10, a pump station 11 with a control panel 12 and slings 13. In order to create the maximum stamping effect when the vibro-stamp 8 moves down and the minimum resistance to its lifting up, stamp the shaft feathers 9 of the vibro-stamp 8 (Fig. 2 - 3) are located in the radial direction around the entire perimeter, in their lower part they have a flat face 14, sharpened at an angle of 45 - 90 ^o , and sharpened at an acute angle to it, the upper face 15.

 The operation of the installation for the construction of crushed stone and sand piles and pile foundations is as follows.

 The vehicle 1 is located in the immediate vicinity of the pile to be constructed in such a way that its lifting mechanism 2 provides lifting operations in the work area. A pump station 11 with a control panel 12 is installed on the working platform. A vibro-stamp 8 is connected to a rod 3, on top of which a hydraulic vibrator 4 is fixed using a headgear 5, previously connected to the pump station 11 through hydraulic hoses 10. An assembled technological projectile consisting of a vibro-stamp, rods and the vibrator is hung with a lifting mechanism using slings 13 and eyebolts 7. During the construction of piles and ramming crushed stone into the ground, the operator of the lifting mechanism lowers and lifts m of technological projectile, and the operator of the pumping station from the control panel 12 controls the speed and amplitude of the vibrations of the vibrator unbalances.

 The sequence of operations of the method of construction of crushed stone and sand piles is as follows.

 A vibratory stamp with a low oscillation frequency of 6 - 15 Hz and a large amplitude of 3 - 20 mm is immersed in soil 16 at the design mark so that the lower end of the vibratory stamp reaches the layer of bearing soil 17 (Fig. 4). Having given the vibration damper a high oscillation frequency of 20–45 Hz with a small amplitude of 0.3–1.5, it is removed from the soil and crushed stone 19 is poured into the mouth of the formed well 18 (Fig. 5). The vibro-stamp is again immersed in the mode of low oscillation frequency of 6–15 Hz and high amplitude of 3–20 mm in the soil, ramming crushed stone to a depth and compacting the volume of the resulting pile 20 (Fig. 6). The diameter of the resulting crushed stone (sand) piles d and the diameter of the zone of compacted near-pile soil D are determined by the diameter of the working body (vibro-stamp), which is selected based on a specific engineering and technical task, taking into account the geological conditions of the strengthened array and the power of the vibrator.

 The sequence of operations of the method of construction of pile foundations on unstable soils is as follows.

 The borehole 21 is pre-drilled to a predetermined depth L and, in case of instability of the borehole walls, the casing pipe 22 is lowered into it, a portion of crushed stone 23 is poured onto the bottom of the borehole. pipe by a certain value A, thereby ensuring contact of the crushed stone with the walls of the drilled well (Fig. 7). In the mode of low frequency and high amplitude, ramming is performed by vibration stamping of crushed stone to depth B and compaction of the soil base of pile 24 (Fig. 8). Once again, the casing is deepened to the design level and the vibro-stamp is removed from the rubble at a high vibration frequency. The well is cleaned to the bottom hole level of the casing 25 (Fig. 9). The reinforcing cage 26 is lowered into the well (Fig. 10) and concreted.

 The invention makes it possible at relatively small additional costs to obtain positive results, including abandoning mobile and expensive to operate pile machines, diesel hammers and rammers and replace them with mobile and low-noise vibrating machines that ensure environmental performance of work both in open areas and in settlements during the construction of temporary and permanent foundations of crushed stone (sand) piles, as well as to increase the bearing capacity of bored piles on the ground in a number of times with the possibility to reduce their length, diameter or number of the field in the pile.

Claims (2)

 1. A method of constructing printed piles and strengthening their foundations, including forming a well, filling the well with a rigid bulk material, vibro-compaction and vibration removal of a vibro-stamp, characterized in that crushed stone and / or sand is used as hard loose material, a portion of which is poured to the bottom of the well, and lowered a vibro-stamp is rigidly connected through the rod to the vibrator in the well, and in the mode of low oscillation frequency of 6-15 Hz and high amplitude of 3-20 mm, stamping of crushed stone and / or sand and compacting it over the entire height and those areas, and vibroizvlechenie vibroshtampa performed at a high oscillation frequency of 20-45 Hz and a small amplitude of 0.3-1.5 mm.  2. The method according to claim 1, characterized in that when working on unstable soils, before filling the well with bulk material, the casing is immersed in it and the well is cleaned up, and after filling the well with bulk material, the casing is partially deepened by the amount of contact of the filling rubble and / or sand with the walls of the well and ramming it into the soil below the base of the casing, then re-deepen the casing to the design elevation and at a high oscillation frequency of 20-45 Hz and a small amplitude tude vibroshtamp 0.3-1.5 mm is recovered, cleaned and then again to the level of the well bottom of the casing is lowered into its skeleton and produce concreting.

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