A method for treating soft interlayer at pile end

Abstract

The present invention discloses a method for processing the soft interlayer at the end of a pile, wherein a variable diameter high-pressure water reaming drill bit is used to perform controllable high-pressure water cutting on the soft rock layer at the end of the pile; the fine-grained rock and soil debris cut is flushed out of the hole with high-pressure water, and the coarse-grained rock debris is deposited at the bottom of the hole. After the cutting diameter of the soft interlayer at the end of the pile is slightly larger than the diameter of the pile body, the cut cavity is then grouting to replace the soft interlayer with concrete, thereby effectively increasing the bearing capacity of the pile and controlling settlement deformation. The present invention can replace and reinforce the soft interlayer at the end of the pile, effectively reduce waste piles, and speed up the construction period of the pile foundation, and is low in cost and easy to use.

Description

Technical Field

[0001] The invention relates to a pile foundation project in the field of construction engineering, and in particular to a method for processing a soft interlayer at a pile end. Background Art

[0002] During the inspection of pile foundations, it is often found that there are relatively weak rock interlayers in a certain range at the pile end, which has a great impact on the bearing capacity and settlement of the pile foundation, and often cannot meet the design requirements and need to be treated. At present, most projects use grouting reinforcement or directly abandon the piles and re-pour them. Directly treating the abandoned piles will cause great waste and increase costs significantly. Grouting reinforcement often uses high-pressure grouting or high-pressure rotary jet grouting. Among them, high-pressure grouting has a better reinforcement effect on weak rocks with developed cracks, but the treatment effect on soft mudstone, carbonaceous rock and other rock masses with poor permeability is extremely poor and cannot meet the design requirements. The commonly used high-pressure rotary jet method is to first use high-pressure water to clean the soft rock, flush out the soft interlayer, and then perform grouting. Although this method can theoretically flush the soft interlayer at the pile end and then perform grouting to form a replacement body, the following problems were found during implementation: 1) The spatial range of the soft interlayer flushed by high-pressure rotary jetting is uncontrollable, and it is difficult to determine whether the cutting cavity meets the design requirements; 2) It is difficult to determine the termination standard for flushing. During the construction process, the return of clean water is often used as the standard. In this way, repeated flushing for several days often fails to meet the standard. However, as the flushing time increases, a large range of soft interlayers outside the pile end are flushed away, forming an overly large cavity. During the later grouting, the sediment at the bottom of the hole often cannot be completely handled, leaving engineering hidden dangers; 3) The inhomogeneity of the grouting body is more obvious. After the grouting is completed, core extraction is performed, and it is often found that there is no slurry in some parts. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for treating the soft interlayer at the pile end, so as to solve the problems of poor treatment effect, extended construction period and increased construction cost in the prior art.

[0004] The technical solution provided by the present invention is a method for treating a soft interlayer at a pile end, comprising the following steps:

[0005] (1) Drill a hole in the center of the pile according to the soft interlayer conditions, with the hole depth passing through the weak interlayer;

[0006] (2) Determine the length of the upper and lower link bars of the variable-diameter high-pressure water reaming drill bit according to the pile diameter, so that the drill bit is slightly larger than the pile diameter when fully opened;

[0007] (3) Connect the variable diameter high pressure water reaming drill bit to the drill pipe and lower it to the top of the hole to be reamed through the drill hole;

[0008] (4) Use high-pressure water for rotary cutting and gradually apply pressure until the drill bit is fully opened and the hole diameter required by the design is reached. Apply pressure from top to bottom to cut until the designed depth is reached;

[0009] (5) Lift the drill up and down to flush the cutter to flush the fine-grained rock cuttings out of the hole and deposit the coarse particles at the bottom of the hole;

[0010] (6) Use a drill pipe connected to a variable-diameter high-pressure water reaming drill bit to perform high-pressure rotary jet grouting on the chip cavity. The high-pressure slurry is transported to the variable-diameter high-pressure water reaming drill bit through the drill pipe, and the grout is sprayed through the nozzle on the drill bit. At the same time, the rotation of the drill pipe drives the drill bit to rotate, so that the coarse-grained rock cuttings deposited at the bottom of the pile are fully mixed with the cement slurry to form a replacement body material;

[0011] (7) After the grouting is completed, the drill rod is lifted up, the diameter of the drill bit is reduced, and it is removed from the borehole, completing the entire construction.

[0012] Furthermore, the diameter of the drilling hole in step (1) is 90-110 mm.

[0013] Furthermore, in step (4), the water pressure is controlled at 15-20 MPa.

[0014] Furthermore, the variable diameter high-pressure water reaming drill bit includes a drill bit joint connected to the drill pipe, the drill bit joint is a hollow structure, a telescopic rod is provided in the middle of the drill bit joint, a sealing tube is connected to the upper part of the drill bit joint through a thread, a high-pressure water passage is provided between the inner wall of the drill pipe and the outer wall of the sealing tube, an upper and lower connecting strips are provided at the lower part of the drill bit joint, reserved holes are respectively opened on both sides of the bottom of the drill bit joint, the reserved holes are connected to the high-pressure water pipe, a plurality of high-pressure water cutting heads are arranged on the high-pressure water pipe, and are fixed on the upper and lower connecting strips, the upper and lower connecting strips are connected by hinged screws, and the bottom of the upper and lower connecting strips are connected to the telescopic rod.

[0015] Furthermore, in step (6), the pressure of the variable diameter high-pressure water reaming drill bit for pressure grouting the chip cavity is controlled according to the hydrostatic pressure of the groundwater.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention adopts a new type of variable diameter high pressure water reaming drill bit to carry out variable diameter high pressure water reaming cutting and reaming of the soft interlayer in the borehole, with fast cutting speed and controllable range of cutting cavity; after the cavity that meets the requirements is cut out, the borehole is flushed to flush the fine rock debris out of the hole and the coarse particles are deposited at the bottom of the hole; then the drill bit is used to perform pressure grouting on the cavity and sediment, which can fully stir the debris deposited at the pile end, so that the grouting effect is reliable, thereby replacing the weak interlayer below the pile end. After the grouting is completed, the drill rod is lifted up, the cutting drill bit will shrink, and then it is withdrawn from the hole and can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of a pile foundation during treatment by the present invention;

[0019] Figure 2 It is a schematic structural diagram of a variable diameter high pressure water jet cutting reaming drill bit of the present invention;

[0020] Figure 3 is a schematic diagram of the pile foundation after treatment;

[0021] In the figure: 1-drill bit joint; 2-sealing tube; 3-telescopic rod; 4-high-pressure water cutting head; 5-high-pressure water pipe, 6-drill rod; 7-upper and lower connecting bars; 8-drill hole; 9-weak rock mass; 10-cutting cavity; 11-grouting replacement body. DETAILED DESCRIPTION

[0022] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1-3 As shown, a method for processing soft interlayer at pile end mainly includes drilling, expanding and cutting soft rock formations, flushing the borehole, and pressure grouting to form a pile end replacement body.

[0024] Drilling: Arrange a drill hole in the center of the pile, mainly by geological drilling rig, with a hole diameter of 90~110mm;

[0025] Cutting and reaming of soft rock formations: Connect the variable-diameter high-pressure water reaming drill bit to the drill pipe, lower it through the hole to the top of the hole to be reamed, and then use high-pressure water for rotary cutting. The water pressure is controlled at about 20MPa, and pressure is gradually applied to the drill bit. As the cutting increases, the drill bit gradually opens until it is fully opened to reach the designed reaming diameter. At this time, the lower part of the high-pressure water cutting head faces downward and the upper part faces upward, so that the soft rock at the bottom can be cut, and the cut debris can be further crushed and flushed out of the hole. Cut from top to bottom until the designed depth is reached.

[0026] Flushing drilling: When the cutting body range reaches the design requirements, the cavity sediment is flushed to flush the cut fine-grained rock chips out of the hole.

[0027] Grouting to form a pile end replacement body: a drill rod is used to connect a variable diameter high-pressure water reaming drill bit to perform high-pressure rotary jet grouting on the chip cavity. During grouting, the variable diameter high-pressure water reaming drill bit is placed at the bottom, and the high-pressure slurry is transported to the variable diameter high-pressure water reaming drill bit through the connected drill rod. Grouting is sprayed through the nozzle on the drill bit. At the same time, the rotation of the drill rod drives the drill bit to rotate so that the coarse-grained rock cuttings deposited at the bottom of the pile are fully mixed with the cement slurry to form a replacement body material. The pressure is controlled by hydrostatic pressure. Due to the sufficient stirring of the drill bit, the coarse-grained rock cuttings deposited at the bottom of the pile can be fully mixed with the cement to form a reliable replacement body.

[0028] The variable diameter high pressure water hole reaming drill bit comprises a drill bit joint 1 connected to the drill rod 6, the drill bit joint 1 is a hollow structure, the middle hole is the upper and lower sliding track of the telescopic rod 3; the upper part of the middle hole is connected to the sealing tube 2 by threading to prevent the high pressure water from leaking from the middle sliding track; the outside is connected to the drill rod 6 by threading; the inner wall of the drill rod 6 and the outer wall of the sealing tube 2 are the high pressure water passages; two holes are left at the bottom of the drill bit joint 1, the water inlet of the high pressure water pipe 5 is fixed in the hole by bolts, a plurality of high pressure water cutting heads 4 are arranged on the high pressure water pipe 5, and are fixed on the upper and lower link bars 7, which can be unfolded with the upper and lower link bars 7, the upper link bars and the lower link bars are connected by hinge screws, and the bottoms of the upper and lower link bars 7 are connected to the telescopic rod 3. The length of the upper and lower link bars can be determined according to the pile diameter, so that the maximum variable diameter is the pile diameter.

[0029] The specific construction steps of the method for treating the soft interlayer at the pile end described in the present invention are as follows:

[0030] 1. Determine the drilling position of the pile center and start drilling with a hole diameter of 90~110mm.

[0031] 2. Determine the length of the upper and lower link bars according to the pile diameter, which should be slightly larger than the pile diameter after the drill bit is fully opened; connect the variable diameter high-pressure water reaming drill bit to the drill rod, lower it to the top of the position to be reamed through the drilling hole, and then use high-pressure water for rotary cutting, and gradually apply pressure to the drill bit. As the cutting increases, the drill bit gradually opens until it is fully opened to reach the designed reaming diameter; at this time, the lower part of the high-pressure water cutting head faces downward and the upper part faces upward, which can cut the soft rock at the lower part, and can also further crush the cut debris and flush it out of the hole; cut from top to bottom until the designed depth is reached; then lift the drill up and down to flush, flush the fine-grained rock cuttings out of the hole, and deposit the coarse particles at the bottom of the hole.

[0032] 3. After the expansion range meets the design requirements, flush the cavity to flush the fine-grained rock cuttings out of the hole.

[0033] Fourth, a new type of high-pressure water expansion drill bit is used for pressure grouting of the cavity body. The grouting pressure is the hydrostatic pressure. With sufficient stirring of the drill bit, the coarse-grained rock cuttings deposited at the bottom of the pile can be fully mixed with the cement to form a reliable replacement body.

[0034] 5. After grouting is completed, lift the drill rod, the cutting drill bit will shrink, and then be retracted from the hole and can be reused.

[0035] The above description is only used to illustrate the preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for treating a soft interlayer at a pile end, characterized in that: The steps include: (1) Drill a hole in the center of the pile according to the soft interlayer conditions, with the hole depth passing through the soft interlayer; (2) Determine the length of the upper and lower link bars of the variable-diameter high-pressure water reaming drill bit according to the pile diameter, so that the drill bit is slightly larger than the pile diameter when fully opened; (3) Connect the variable diameter high pressure water reaming drill bit to the drill pipe and lower it to the top of the hole to be reamed through the drill hole; (4) Use high-pressure water for rotary cutting and gradually apply pressure until the drill bit is fully opened and the hole diameter required by the design is reached. Apply pressure from top to bottom to cut until the designed depth is reached; (5) Lift the drill up and down to flush the fine-grained cuttings out of the hole and deposit the coarse-grained cuttings at the bottom of the hole; (6) Use a drill pipe connected to a variable-diameter high-pressure water reaming drill bit to perform high-pressure rotary jet grouting on the chip cavity. The high-pressure slurry is transported to the variable-diameter high-pressure water reaming drill bit through the drill pipe, and the grout is sprayed through the nozzle on the drill bit. At the same time, the rotation of the drill pipe drives the drill bit to rotate, so that the coarse-grained rock cuttings deposited at the bottom of the pile are fully mixed with the cement slurry to form a replacement body material; (7) After the grouting is completed, the drill rod is lifted up, the diameter of the drill bit is reduced, and it is removed from the borehole to complete the entire construction; The variable diameter high-pressure water hole expansion drill comprises a drill head joint (1) connected to a drill rod (6); the drill head joint (1) is a hollow structure; a telescopic rod (3) is arranged in the middle of the drill head joint (1); a middle hole is a track for the telescopic rod (3) to slide up and down; a sealing tube (2) is connected to the upper part of the middle hole of the drill head joint (1) by a thread; a high-pressure water passage is formed between the inner wall of the drill rod (6) and the outer wall of the sealing tube (2); an upper link bar and a lower link bar are arranged at the lower part of the drill head joint (1); reserved holes are respectively opened on both sides of the bottom of the drill head joint (1); the reserved holes are communicated with a high-pressure water pipe (5); a plurality of high-pressure water cutting heads (4) are arranged on the high-pressure water pipe (5); the high-pressure water pipe (5) is fixed to the upper link bar and the lower link bar; the upper link bar and the lower link bar are connected by hinge screws; and the bottom of the lower link bar is connected to the telescopic rod (3).

2. The method for treating the soft interlayer at the pile end according to claim 1, characterized in that: The diameter of the hole drilled in step (1) is 90-110 mm.

3. The method for treating the soft interlayer at the pile end according to claim 1, characterized in that: In step (4), the water pressure is controlled at 15-20 MPa.

4. The method for treating the soft interlayer at the pile end according to claim 1, characterized in that: In step (6), the pressure of the variable diameter high-pressure water reaming drill bit in performing high-pressure rotary jet grouting on the chip cavity is controlled according to the hydrostatic pressure of the groundwater.

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