CN101525880A - Plastic sleeve concrete pile and method thereof for reinforcing soft soil foundation - Google Patents

Abstract

A concrete pile with plastic casing and its construction method, which is composed of cover plate, plastic casing, pile point, concrete and casing joints, the top of the plastic casing is connected with the cover plate, the lower part is connected with the pile point, each section The plastic casings are connected by casing joints, and the concrete is poured into the plastic casings. The construction method is to connect the prefabricated pile tips with the plastic casings, and then lift the plastic casings together with the pile tips with the immersed tube to a certain height. Pull into the sinking tube, turn on the plastic casing concrete pile driver, drive the plastic casing with the pile tip into the design depth of the pile length, pour water into the plastic casing to 1/2-2/3 of the pile length, and then lift The plastic casing and the pile point are left in the foundation, and then the water injection in the plastic casing is pumped out, and the concrete pile body and cover are poured into the plastic casing to make a plastic casing concrete pile. The effect of soil is small, the pile is not easy to break, the construction is flexible and fast, the quality of the pile body is easy to control, the pouring is not affected by the outside, the bearing capacity of the single pile is high, and the cost performance is good.

Description

Concrete pile with plastic casing and method for strengthening and treating soft soil foundation

technical field

The invention relates to a pile type of foundation engineering, in particular to a method for reinforcing and treating soft ground with a plastic casing concrete pile.

Background technique

At present, piled embankments have become a common foundation treatment method in expressway, high-speed railway, municipal, airport and other projects. Before the invention of the present invention, embankment piles were based on flexible piles such as cement-soil mixing piles and rigid piles such as vibration sinking pipe piles, prestressed pipe piles, and bored piles. Cement-soil mixing piles (including slurry-sprayed piles and powder-sprayed piles) are flexible piles with low pile body strength and low cost, but the construction quality is not easy to control. The effect is not as ideal as that of prefabricated piles. In the high fill section, the bearing capacity is required to be high and a large number of piles is required, which makes the cost very high. The cost of vibratory sinking tube cast-in-place concrete piles is lower than that of prefabricated piles. However, due to the great impact on the surrounding piles during the vibration construction process, vibrating tube sinking concrete piles are prone to broken piles, difficult quality control and detection, and many quality accidents. Factors such as too large coefficient and great influence on surrounding buildings are not used much in actual embankment engineering at present. Because the quality of prestressed reinforced concrete piles is easy to control and detect, the reinforcement effect is good, and there will be no quality problems such as broken piles, it is currently widely used in deep soft foundation treatment projects. However, the method of using this prefabricated pile is often quite expensive. At the same time, when the high-strength pile is used as an embankment pile, there is a lot of waste in the strength of the pile body, and the strength of the pile body cannot be fully obtained in the engineering use stage after the pile is formed. play and use. Slurry-solid powder material piles have no problems such as mud skin and sediment, but the construction cost is high. In addition to the problems of environmental pollution caused by mud treatment, there are also gravels that are not easy to clean, waste of materials in the foundation of sand and gravel interlayers, and poor grouting. Uniform and other shortcomings.

Before the invention of the present invention, a kind of double-walled plastic casing concrete pile was used abroad, and what it used was a double-layer plastic casing whose outer wall was screw thread and smooth inner wall. There is a closed space between the two walls of the double-wall bellows, and the poured concrete cannot be in contact with the outer wall, and the friction marks of the pile and soil will easily damage the threads of the outer wall, thereby affecting the friction between the pile and the soil; the inner wall of the double-wall bellows is smooth, and the poured concrete will Because of the shrinkage, the concrete and the plastic casing cannot be in close contact. These defects greatly reduce the contribution of the plastic casing to the bearing capacity of the pile, and the frictional engagement between the thread and the soil cannot be brought into play. The casing basically does not work when the pile is working, causing a lot of waste. In addition, when foreign countries use ordinary PVC pipes as double-walled plastic casing materials, because PVC pipes are hard and inflexible, the drilling machine must first immerse the pipes to the design depth during construction, and then lift the casings from the upper part of the immersed pipes. The opening is placed in the immersed tube, and the immersed tube can be pulled out after pouring concrete into the plastic sleeve immediately, and the construction of a pile is completed. In this method, casing drilling and concrete pouring are carried out continuously, and special attention needs to be paid to the construction of mutual cooperation, the process is complicated, and the construction speed is slow. When the plastic casing adopts a double-walled HDPE pipe, it is characterized in that it can be properly bent, and the casing connected to the prefabricated pile tip can be inserted from the bottom of the vertical immersed pipe of the driving machine in advance and driven into the foundation. This method separates concrete construction from casing drilling, which improves construction efficiency, but the price of HDPE material is quite expensive, and the project cost increases significantly. In addition, currently foreign concrete piles with plastic sleeves have a single type, and the pile tips used are flat-bottomed steel plates, which are difficult to pass through when encountering hard soil layers.

The single-wall threaded plastic casing cast-in-situ concrete pile construction method currently used in domestic projects: use a fully hydraulic auxiliary vibration intubation machine for construction, use its frame and steel pipes to tilt, and firstly connect it to the prefabricated pile tip conveniently The good plastic casing is inserted into the inclined steel pipe, and then the frame and steel pipe are mechanically placed to drive the plastic casing into the foundation. This method has made many innovations and improvements on the basis of foreign countries. The single-wall threaded pipe is used, so that the poured concrete and the casing can be tightly combined, and the outer pipe wall is not easily damaged, and the friction between the casing and the soil can be fully utilized to improve carrying capacity. Using the method of tilting the frame, the hard casing made of cheap PVC material can also meet the construction method of pouring concrete after all the casing is laid first, which improves the construction efficiency. In addition, it can also be used to lay a variety of Angled stakes. By changing the form of pile tips, developing concrete and steel plate concrete pile tips, combined with hydraulic auxiliary vibration machinery, the penetration ability in piling engineering is improved and the application range is expanded. However, it also has obvious defects: the effect of pile-forming soil squeezing makes the plastic casing easy to deform or even be damaged; due to the limitation of its own weight and power system, it is difficult for the crawler-type hydraulic drilling machine to pass through when encountering hard soil layers. Difficult, and the depth of driving is shallow; the expansion of the pile will greatly disturb the soil around the pile, and the frictional resistance of the pile body will be weakened; the insertion of the plastic sleeve into the immersed tube requires the immersed tube or mechanical tilting, righting, vertical, and centering. This process takes a long time, which greatly affects the construction speed and increases the construction cost.

Therefore, it is very important to seek a kind of embankment pile type that has both good quality of prefabricated piles and low cost of cast-in-place concrete piles, convenient construction, good reinforcement effect, and little impact on the surrounding environment, which is suitable for domestic promotion and use.

Contents of the invention

The object of the present invention is to provide a plastic casing concrete pile and a method for reinforcing and treating soft ground.

The purpose of the present invention is achieved by the following technical solutions:

A plastic casing concrete pile is characterized in that it is composed of a cover plate 1, a casing 2, a pile point 3, concrete 4 and a casing joint 5, wherein the top of the casing 2 is fixedly connected to the cover 1, and the casing The lower part of the pipe 2 is connected with the pile point 3, and the casing joint 5 is fixedly connected between each section of the casing 2, and the concrete 4 is poured into the casing 2.

The upper part of the cover plate 1 is provided with 2-6 main ribs 6 horizontally, 4-6 ribs 7 vertically, and two protruding ribs 8 are strung out of the top surface of the cover plate longitudinally, and the ribs 7 are fixed with the main ribs 6 The joints are then placed in "cap nail" type moulds, cast in concrete or prefabricated in reinforced concrete.

The outer wall of the casing 2 is threaded or partly smooth, and the casing joints 5 of each section of the casing 2 are glued and connected with the casing joint 5, and the casing 2 is made of PVC material.

The pile point 3 is a reinforced concrete structure, conical, and the upper center is provided with a casing plug 9 made of PVC material. A concave ring 11 or a step-shaped platform 12 are provided on the periphery.

The periphery of described sleeve pipe 2 can also be fixedly connected with 2-4 root grouting pipes 13 in addition, and this pipe is made of PVC material or steel pipe.

The method for reinforcing the soft soil foundation with plastic casing concrete piles has the following steps:

(1) Prefabricate the concrete pile tip 3 with a special mold: set the steel bar for the pile tip configuration in the steel mold, vibrate the concrete pouring, set a concave ring 11 or a step-shaped platform 12 before the concrete solidifies, and place a plastic casing plug 9 , take off the steel mold after the concrete reaches the dry strength;

(2) Connect each section of single-wall threaded plastic casing 2 through the casing joint 5, and glue it with PVC adhesive, or use strong glue or anchor to fix the connection, so that the length of the casing is equal to the length of the designed pile or Slightly longer than the designed pile length;

(3) Connect the lower end of the single-wall threaded plastic casing 2 with the casing plug 9 on the prefabricated concrete pile point 3, and glue it with PVC adhesive, or fix the connection with superglue or anchors to form the upper end of the casing 2 open semi-enclosed space;

(4) Lift the single-wall threaded plastic casing 2 and the pile tip 3 to a height of 1.0-2.5 meters from the ground with a plastic casing concrete pile setting machine, and use the sling 14 to lift the plastic casing 2 connected to the pile tip 3 from the immersed pipe 15. The bottom is pulled into the immersed tube, and the bottom of the immersed tube 15 is inserted into the concave ring 11 on the pile point or rested on the stepped platform 12;

(5) Turn on the plastic casing concrete pile setting machine, find out the pile position, and drive the immersed tube 15 together with the plastic casing 2 with the pile head inside into the foundation design pile depth;

(6) After driving the single-wall threaded plastic casing 2 to the designed pile depth, use the water injection pipe 16 to inject water into the single-wall threaded plastic casing 2, and start lifting the immersed pipe after injecting water to 1/2-2/3 of the pile length 15, while the plastic casing 2 and the pile point 3 are left in the foundation, and the water injection is continued while pulling out, so as to protect the plastic casing 2;

(7) After the sub-section plastic casing is finished, use a small water pump to pump out the water in the plastic casing 2, and then uniformly pour the concrete pile body and cover plate 1, and vibrate and compact to form a plastic casing in the sub-section concrete pile group;

(8) When further improving the pile side frictional resistance, use the small grouting pipe 13 to grout the plastic casing 2 pile sides in addition to improve the soil properties around the pile;

(9) After the concrete of the pile body and the cover plate 1 reaches the design strength, lay reinforcement materials on the top of the cover plate 1 and connect with the cover plate 1 to form a whole, or lay a sandstone cushion on the top of the cover plate 1 first, and add The rib material is set in the sand and gravel cushion, not connected with the cover plate 1;

(10) Lay the sand and gravel cushion to form the composite foundation of plastic casing concrete piles.

The pile body casing 2 of the present invention adopts a single-wall PVC pipe that is threaded both inside and outside, and other plastic casings can also be used. Using single-wall threaded plastic casing, the poured concrete can fully contact with the plastic casing 2, and will not be isolated or disengaged due to concrete shrinkage, so that the outer pipe wall is not easily damaged, and the contact friction between the pile and the soil is increased , improve the bearing capacity of the pile, and give full play to the role of the casing thread. Simultaneously, the single-wall threaded plastic casing of the present invention can be made of cheap PVC material, can be bent properly, and combined with the lifting of the immersed pipe of the plastic casing concrete pile driver, there can be enough space to conveniently and quickly use the pull rope device to pull the plastic After the casing is inserted into the immersed tube, it is punched. In this way, the plastic casing made of cheap PVC material can also meet the construction method of laying all the outer plastic casings before starting the concrete pouring, that is, the two processes of pouring concrete and setting the plastic casing are separated. , The independent construction of the two does not affect each other, thus greatly improving the construction efficiency. In the past, only expensive HDPE and other PE soft material pipes or immersed pipes can be used to achieve this construction process, which increases a lot of construction costs.

In addition, in order to reduce the adverse effect of negative friction on the upper part of the pile, the casing 2 can be connected by a threaded casing on the lower part and a casing with smooth inner and outer walls on the upper part, which can effectively reduce the negative friction on the upper pile body.

The plastic casing can also adopt different ring stiffnesses along the pile body according to the soft soil parameters, driving depth and pile spacing. For casings with different ring stiffnesses, joints can be added with sealing rings, and glue and screws can be used as auxiliary methods when necessary. Connection, which can not only ensure the quality of the casing, but also save materials and reduce costs.

The prefabricated pile tips used in the present invention can adopt steel sheet pile tips, concrete pile tips or steel plate concrete pile tips according to different soil properties in various places, and can adopt various forms such as conical and X-shaped, which expands the scope of application. At present, conical prefabricated concrete pile tips are mostly used, and the joints that can be tightly connected with plastic casings are preset on the prefabricated pile points.

In the present invention, the pile top cover plate can be prefabricated, or the cover plate and the pile body concrete can be poured in an integrated way, and the shape can be round or square. When the prefabricated cover plate is used, after the concrete pouring of the pile body reaches a certain strength, the cover plate is placed on the top of the pile, and the cover plate is guaranteed to be flat, so that the construction is flexible and convenient; while the cast-in-place cover plate is used, the integrity is better, and the plastic casing After the drilling is completed, pump out the water injected into the casing, excavate a groove of a suitable size along the top of the casing according to the design size of the cover plate, put the cover plate mold into the groove, and then pour concrete. The top inserting bar can be bound and connected with the two layers of steel bars inside the cover plate before pouring concrete; or the steel bar can be set to protrude from the top part of the cover plate, and the reinforcement material can be directly laid on the cover plate and bound and connected with the protruding steel bars of the cover plate to form a whole. It can exert the load-bearing performance of the plastic casing concrete pile, or lay a sand and gravel cushion on the top of the cover plate, and the reinforcement material is arranged in the sand and gravel cushion, and is not connected with the cover plate.

The invention has a small soil squeezing effect, will not break the pile due to vibration squeezing soil, and has little impact on the surrounding environment, flexible and fast construction, low requirements on the site, easy inspection and control of the pile body quality, controllable concrete dosage, and pouring is not affected by the outside world. The single pile has a high bearing capacity, good cost performance, and strong applicability.

Description of drawings

Figure 1—Schematic diagram of the plastic casing concrete pile

(a) The inner and outer walls of the casing are threaded (b) The upper part is a smooth casing, and the lower part is a threaded casing

Figure 2 - Schematic diagram of the cover plate structure

Figure 3 - Schematic diagram of a precast concrete pile tip

(a) There is a concave ring on the upper part of the pile tip (b) The upper part of the pile tip is a stepped platform

Figure 4 Schematic Diagram of Inserting Plastic Sleeve into Immersed Tube

Figure 5 Grouting on the side wall after the plastic casing is driven into the foundation

Reference signs: 1-cover plate, 2-sleeve, 3-pile tip, 4-concrete, 5-sleeve connection joint, 6-transverse main reinforcement, 7-longitudinal main reinforcement, 8-longitudinal protruding reinforcement, 9-prefabricated pile Point middle casing plug, 10-horizontal reinforcement material, 11-concave ring, 12-step platform, 13-grouting pipe, 14-immersed pipe (steel pipe), 15-hanging rope, 16-water injection pipe.

Detailed ways

Example 1:

The pile tip 3 with a concave ring is prefabricated with a specially developed special plastic casing concrete pile tip mold; the casing 2 of PVC material is reasonably selected according to the soil quality parameters, the driving depth, and the pile spacing; the length of each casing is 10 meters, 25 centimeters in diameter, the pile body is connected by fully threaded casing, Figure 1-(a); each section of plastic casing is connected to the designed pile with joint 5 and PVC adhesive, and the length of the pile is 20 meters; The lower end of the plastic casing 2 is connected with the casing plug 9 on the prefabricated concave ring pile tip 3, and is glued with PVC adhesive to form a semi-enclosed space with an opening at the upper end of the casing; Put into the immersed tube, use the plastic sleeve concrete pile setting machine to lift the immersed tube 14 to 2 meters in height, pull the plastic sleeve 2 connected to the pile tip 3 into the immersed tube 14 from the bottom of the immersed tube 14 with a sling 15, and then Turn on the plastic sleeve concrete pile driving machine and align the pile position to drive to the design depth of 20 meters; after the plastic sleeve 2 is driven to the design depth of 20 meters, use the water injection pipe 16 to inject water into the pipe to a length of 2\3 piles Start to lift the immersed tube 14 after the water volume, while the casing 2 and the pile tip 3 stay in the foundation, and continue to inject water while pulling out to protect the casing 2; 2. Inject water into the interior and pump it out. According to the design size of the cover plate 1, put it into the cover plate mold according to the design size of the cover plate 1 along the groove on the top of the casing. The cover plate 1 is vibrated and compacted to realize integrated construction and form a concrete pile group with plastic sleeves. When the concrete 4 reaches a certain strength, horizontal reinforcement material 10 is laid on the top of the cover plate 1 and is connected with the protruding steel bars set on the top of the cover plate. 11 Binding and connecting to form a whole, and finally laying a sand and gravel cushion to form a composite foundation of plastic casing concrete piles.

Example 2:

The pile tip 3 with a stepped platform is prefabricated with the specially developed special plastic casing concrete pile tip mold; the casing 2 of PVC material is reasonably selected according to the soil quality parameters, the driving depth, and the pile spacing; The lower part of the casing 2 with smooth outer walls adopts the full-threaded casing connection method shown in Figure 1-(b); the plastic casing 2 of each section is connected to the design pile with a joint 5 and PVC adhesive. The length of the pile is 20 meters. Four grouting pipes 13 are fixed on the periphery of the sleeve 2 with iron wires, and the lower end of the plastic sleeve 2 is connected to the prefabricated sleeve plug 9 with a stepped platform pile point 3, and glued with PVC adhesive to form a sleeve. A semi-enclosed space with an opening at the upper end of the pipe; for the convenience of putting the casing into the immersed pipe, use a plastic casing concrete pile driver to lift the immersed pipe to a height of 14 to 2 meters, and use a sling to connect the plastic casing 2 connected to the pile tip 3 15 Pull into the immersed tube 14 from the bottom of the immersed tube 14, and then open the immersed tube pile machine to align the pile position and drive to the design depth of 20 meters; after the plastic casing 2 is driven to the design depth of 20 meters, use the water injection pipe 16 to pair the pipes. Carry out water injection, and start to lift the immersed pipe 14 after injecting 2\3 pile lengths of water, while the casing 2 and the pile tip 3 are left in the foundation, and continue to inject water while pulling out, to protect the casing 2; After all the pipes are drilled, the water in the casing 2 is pumped out, and the cover plate 1 is slotted along the top of the casing according to the design size of the cover plate 1 and put into the cover plate mold. Or after welding, the concrete pile body and the cover plate 1 are uniformly poured, vibrated and compacted, and the integrated construction is realized to form a plastic casing concrete pile group. Casing 2 piles are grouted to improve the soil properties around the piles. When the concrete 4 reaches the dry strength, first lay a sand and gravel cushion on the top of the cover plate 1, then lay horizontal reinforcement materials 10, and finally lay the rest of the sand and gravel cushion A plastic-sleeved concrete pile composite foundation is formed.

Claims (6)

1, a kind of plastic sleeve concrete pile, it is characterized in that it is made up of cover plate (1), sleeve pipe (2), stake point (3), concrete (4) and casing joint (5), fixedly connected with cover plate (1) in the top of its middle sleeve (2), the bottom of sleeve pipe (2) is connected with stake point (3), fixedly connected between every joint sleeve pipe (2) with casing joint (5), concrete perfusion (4) in the sleeve pipe (2).

2, plastic sleeve concrete pile according to claim 1, the upper lateral that it is characterized in that described cover plate (1) is provided with 2-6 root master muscle (6), vertically be provided with 4-6 root reinforcement (7), vertically there are two outstanding muscle (8) to go here and there out the cover plate end face in addition, reinforcement (7) is fixedlyed connected with main muscle (6), be placed on then in the mould of " snap-fastener " type, make or adopt reinforced concrete prefabricated forming with concreting.

3, plastic sleeve concrete pile according to claim 1, it is characterized in that described sleeve pipe (2) for inside and outside all are single wall pvc pipes of screw thread or for being the pvc pipe of smooth shape inside and outside the top employing, screw thread single wall pvc pipe is adopted in the bottom, is connected or with super glue or fixedly connected with holdfast with the PVC cementing agent is gluing with casing joint (5) between every joint sleeve pipe (2).

4, plastic sleeve concrete pile according to claim 1, it is characterized in that described stake point (3) is reinforced concrete structure, be conical, center upper portion is provided with the sleeve pipe plug (9) of using the PVC material or making of metal material, insert in the sleeve pipe plug (9) sleeve pipe (2) bottom, with the gluing connection of PVC cementing agent or with super glue or fixedly connected with holdfast, the periphery of sleeve pipe plug (9) is provided with a spill annulus (11) or is provided with the platform (12) of a step.

5, plastic sleeve concrete pile according to claim 1 is characterized in that the periphery of sleeve pipe (2) can also add the fixing 2-4 root Grouting Pipe (13) that connects in addition, and this effective PVC material or steel pipe are made.

6, a kind of job practices with the plastic sleeve concrete pile reinforcing soft soil foundation, its construction sequence is as follows:

(1) with particular manufacturing craft precast concrete pile point 3: the reinforcing bar that the configuration of stake point is set in the steel mould, concreting is shaken close, the platform 12 of spill annulus 11 or step was set before concrete setting, lays plastic bushing plug 9, treat to take off punching block after concrete reaches dried tenacity;

(2) every joint single wall screw plastic casing 2 is connected by casing joint 5 respectively, and gluing with the PVC cementing agent, or with super glue or fixedly connected with holdfast, casing length is equated with designing pile length or omit to surpass designing pile length;

(3) single wall screw plastic casing 2 lower ends are connected with sleeve pipe plug 9 on the precast concrete pile point 3, and gluing or with super glue or fixedly connected with the PVC cementing agent with holdfast, form the hemi-closure space of sleeve pipe 2 upper end open;

(4) promote immersed tube 15 with the plastic sleeve concrete pile machine that sets, apart from ground 1.0-2.5 rice height, plastic bushing 2 usefulness lifting ropes 14 that connect stake point 3 were drawn in the immersed tube from 15 ends of immersed tube, the bottom of immersed tube 15 is inserted in the spill annulus 11 of stake sharp 3 or be shelved on the step platform 12;

(5) open plastic sleeve concrete pile and set machine, find the stake position accurately, immersed tube 15 is squeezed into the ground design stake degree of depth in the lump together with the single wall screw plastic casing 2 of the inside band stake point;

(6) to the degree of depth of designing pile length, utilize water injection pipe 16 in plastics single wall screw sleeve pipe 2, to carry out water filling 2 dozens of single wall screw plastic casings, annotate to the long water yield of 1/2-2/3 stake and begin to promote immersed tube 15, and single wall screw plastic casing 2 and stake point 3 are stayed in the ground, continue water filling while pulling out, single wall screw plastic casing 2 is protected;

(7) treat that branch section plastic bushing sets and finish, water in the plastic bushing 2 are pumped that unified again fluid concrete pile body and cover plate 1, and vibration compacting form the plastic sleeve concrete pile group in minute section with small pump;

(8) in the time will further improving pile side friction, other to 2 side slip castings of plastic bushing, improves all soil nature matter of stake with small-sized Grouting Pipe 13;

(9) after pile body, cover plate 1 concrete reach design strength, lay reinforcement material on cover plate 1 top, and be connected with cover plate 1, form an integral body, or lay sand-gravel cushion earlier on cover plate 1 top, reinforcement material is arranged in the sand-gravel cushion, is not connected with cover plate 1;

(10) lay sand-gravel cushion, form the plastic sleeve concrete pile composite foundation.

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