A construction method and structure of a thin-walled cave combined pipe pile

Abstract

The present invention discloses a construction method and structure of a thin-walled cave combined pipe pile. The present invention adopts prestressed pipe piles to protect the top of the cave; then a micro steel pipe pile is vertically penetrated through the cave until it is driven into the slightly weathered limestone layer at the bottom of the cave; then cement slurry is injected into the prestressed pipe pile and the micro steel pipe pile to fill and reinforce the pile body; and the outer cylindrical surface of the micro steel pipe pile is protected against corrosion by the overflowing cement slurry; the cement slurry overflowing from the grouting hole of the micro steel pipe pile also serves to harden and reinforce the slightly weathered limestone layer around the micro steel pipe pile, thereby improving the safety of the pile body. The present invention effectively utilizes the characteristics of prestressed pipe piles and micro steel pipe piles. The prestressed pipe piles are easy to transport and have a fast construction speed, which greatly reduces the construction period. The micro steel pipe construction process is simple, which effectively reduces the waste of grouting. Since the bottom end of the micro steel pipe pile penetrates into the slightly weathered rock layer by no less than 0.8m, the safety and reliability are relatively high.

Description

Technical Field

[0001] The invention relates to a construction method and structure of a thin-wall karst cave combined pipe pile, belonging to the technical field of building foundation construction. Background Art

[0002] With the long-term geological effects and groundwater erosion, caves of different sizes have developed in the bearing layer and surrounding areas of the pile foundation, and there are even many connected caves. Therefore, the geological environment is relatively fragile and the upper bearing capacity is insufficient. Once the geological environment is disturbed or damaged during drilling or pile foundation construction, the cave will collapse, resulting in displacement of pipe piles and insufficient bearing capacity, affecting the structural safety of the building. If the existing technology is used for cast-in-place pile construction, the cost is high, the cycle is long, and the construction coverage area is large, so parallel operations cannot be carried out. Due to the large size of the cave and the unclear direction of the cave, the traditional grouting loss is serious, and the cost impact is relatively large. Therefore, the existing technology still has shortcomings and needs to be further improved. Summary of the invention

[0003] The purpose of the present invention is to provide a construction method and structure of a thin-walled cave composite pipe pile to solve the technical problems of using the existing technology for cast-in-place pile construction, such as high cost, long cycle, large construction coverage area and inability to carry out parallel operations, thereby overcoming the shortcomings of the existing technology.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] The invention discloses a construction method for a thin-walled cave combined pipe pile. The method comprises the following steps: using a prestressed pipe pile with a pile tip at the lower end to drive from the ground to a position above the cave top where the top wall of the cave has not been penetrated, and then stopping the driving; using the prestressed pipe pile to block the soil at the top of the cave and around the prestressed pipe pile; then using a micro-steel pipe pile with grouting holes evenly distributed around the pipe wall to penetrate the cave top wall from the middle of the prestressed pipe pile, and vertically penetrate the cave until the slightly weathered limestone layer at the bottom of the cave is driven in, with the top of the micro-steel pipe pile located in the prestressed pipe pile; then using a grouting device to inject cement slurry from the top of the prestressed pipe pile into the prestressed pipe pile and the micro-steel pipe pile; reinforcing the slightly weathered limestone layer at the bottom of the micro-steel pipe pile by the cement slurry, and at the same time using the cement slurry overflowing from the grouting holes around the micro-steel pipe pile to wrap the outer circumferential surface of the micro-steel pipe pile located in the cave to prevent corrosion of the micro-steel pipe pile; after the grouting is completed, the height of the grouting surface is higher than the top of the micro-steel pipe pile by a certain distance.

[0006] In the aforementioned construction method of thin-walled cave composite pipe piles, the cement slurry adopts 52.5R pure cement slurry.

[0007] In the aforementioned construction method of thin-walled cave combined pipe piles, when injecting cement slurry into the prestressed pipe piles and micro steel pipe piles, the grouting pressure of the grouting equipment should be adjusted within the range of 1.5 to 2.5 MPa according to the specific situation to prevent the cement slurry from jetting out of the grouting hole in the cave.

[0008] In the aforementioned construction method of thin-walled karst cave combined pipe piles, when injecting cement slurry, the uniformity of grouting should be ensured.

[0009] In the aforementioned construction method of thin-walled cave combined pipe piles, the depth to which the micro steel pipe piles are driven into the slightly weathered limestone layer is not less than 0.8 meters.

[0010] In the aforementioned construction method of thin-walled cave combined pipe piles, the hole spacing of the three rows of grouting holes in the lower section of the micro steel pipe piles is 0.5 meters, and the remaining hole spacings are 1 meter.

[0011] In the aforementioned construction method of thin-walled cave combined pipe piles, the diameter of the grouting holes is 10 mm.

[0012] In the aforementioned construction method of thin-walled cave combined pipe piles, after the grouting is completed, the prestressed pipe piles and micro steel pipe piles are left underground, and the micro steel pipe piles are used as reinforcement support for crossing the cave.

[0013] The structure of a thin-walled cave combined pipe pile of the present invention constructed according to the above method includes a prestressed pipe pile with a pile tip at the lower end, the prestressed pipe pile is inserted into the soil at the top of the cave, and the position of the bottom end of the pile tip of the prestressed pipe pile is higher than or equal to the position of the top wall of the cave above the top of the cave; a micro steel pipe pile is arranged in the prestressed pipe pile, and a grouting hole is arranged on the pipe wall of the micro steel pipe pile, the micro steel pipe pile passes through the top wall of the cave and vertically penetrates the cave and is inserted into the slightly weathered limestone layer at the bottom of the cave, the top of the micro steel pipe pile is located in the prestressed pipe pile and is lower than the upper end of the prestressed pipe pile; cement slurry is poured into the prestressed pipe pile and the micro steel pipe pile, and the cement slurry flows through the grouting hole of the micro steel pipe pile to the outer pipe wall of the micro steel pipe pile and gradually solidifies on the outer pipe wall of the micro steel pipe pile, the micro steel pipe pile is connected to the prestressed pipe pile and the slightly weathered limestone layer as a whole through the solidified cement slurry to form the structure of the thin-walled cave combined pipe pile.

[0014] In the structure of the aforementioned thin-wall karst cave combined pipe pile, saw teeth are provided at the bottom end of the pile tip of the prestressed pipe pile.

[0015] Due to the adoption of the above technical scheme, compared with the prior art, the present invention effectively utilizes the characteristics of prestressed pipe piles and micro steel pipe piles. Prestressed pipe piles are easy to transport and have a fast construction speed, which greatly reduces the construction period. The micro steel pipe construction process is simple, which effectively reduces the waste of grouting. Since the bottom end of the micro steel pipe pile penetrates into the slightly weathered rock layer by no less than 0.8m, the safety and reliability are relatively high. Field tests have proved that the present invention is particularly suitable for reinforcing thin-walled caves. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the present invention;

[0017] Figure 2 It is a structural schematic diagram of the prestressed pipe pile of the present invention;

[0018] Figure 3 It is a structural schematic diagram of the micro steel pipe pile of the present invention.

[0019] The markings in the figure are as follows: 1-pile tip, 2-prestressed pipe pile, 3-cavern, 4-cavern top wall, 5-soil, 6-grouting hole, 7-micro steel pipe pile, 8-slightly weathered limestone layer, 9-cement slurry, 10-grouting surface, 11-serration. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0021] A construction method of a thin-wall cave combined pipe pile of the present invention, as Figure 1 As shown, the method is to use a prestressed pipe pile 2 with a pile tip 1 at the lower end to drive from the ground to a position above the top of the cave 3 without penetrating the cave top wall 4 and stop driving; the prestressed pipe pile 2 is used to block the soil 5 on the top of the cave 3 and around the prestressed pipe pile 2; then, a micro steel pipe pile 7 with grouting holes 6 evenly distributed around the pipe wall is used to penetrate the cave top wall 4 from the middle of the prestressed pipe pile 2, and vertically penetrate the cave 3 until it is driven into the slightly weathered limestone layer 8 at the bottom of the cave 3, and the top of the micro steel pipe pile 7 is located in the prestressed pipe pile 2; then, cement slurry 9 is injected into the prestressed pipe pile 2 and the micro steel pipe pile 7 from the top of the prestressed pipe pile 2 through the grouting equipment; the cement slurry 9 uses 52.5R pure cement slurry. The slightly weathered limestone layer 8 at the bottom of the micro steel pipe pile 7 is reinforced by cement slurry 9. At the same time, the cement slurry 9 overflowing from the grouting holes 6 around the micro steel pipe pile 7 wraps the outer circumference of the micro steel pipe pile 7 in the cave 3 to protect the micro steel pipe pile 7 from corrosion. After the grouting is completed, the height of the grouting surface 10 is higher than the top of the micro steel pipe pile 7 by a certain distance. When injecting cement slurry 9 into the prestressed pipe pile 2 and the micro steel pipe pile 7, the grouting pressure of the grouting equipment should be adjusted within the range of 1.5 to 2.5 MPa according to the specific situation to prevent the cement slurry 9 from jetting out of the grouting hole 6 in the cave 3. When injecting cement slurry 9, the uniformity of grouting should be ensured. The depth of the micro steel pipe pile 7 driven into the slightly weathered limestone layer 8 is not less than 0.8 meters. Figure 3 As shown, the distance between the three rows of grouting holes 6 in the lower section of the micro steel pipe pile 7 is 0.5 meters, and the distance between the remaining holes is 1 meter. The diameter of the grouting holes 6 is 10 mm. Figure 2 As shown; after the grouting is completed, the prestressed pipe piles 2 and the micro steel pipe piles 7 are left underground, and the micro steel pipe piles 7 are used as reinforcement supports for passing through the cave 3.

[0022] The structure of a thin-walled cave combined pipe pile of the present invention formed according to the above method is as follows: Figure 1 to Figure 3 As shown, the structure includes a prestressed pipe pile 2 with a pile tip 1 at the lower end, the prestressed pipe pile 2 is inserted into the soil 5 at the top of the cave 3, and the position of the bottom end of the pile tip 1 of the prestressed pipe pile 2 is higher than or equal to the position of the cave top wall 4 above the top of the cave 3; a micro steel pipe pile 7 is arranged in the prestressed pipe pile 2, and a grouting hole 6 is arranged on the pipe wall of the micro steel pipe pile 7, the micro steel pipe pile 7 passes through the cave top wall 4 and vertically penetrates the cave 3 and is inserted into the slightly weathered limestone layer 8 at the bottom of the cave 3, and the top of the micro steel pipe pile 7 is located in the prestressed pipe pile 2 and is lower than the upper end of the prestressed pipe pile 2 ; Cement slurry 9 is poured into the prestressed pipe pile 2 and the micro steel pipe pile 7, and the cement slurry 9 flows through the grouting hole 6 of the micro steel pipe pile 7 to the outer wall of the micro steel pipe pile 7 and gradually solidifies on the outer wall of the micro steel pipe pile 7. The micro steel pipe pile 7 is connected with the prestressed pipe pile 2 and the slightly weathered limestone layer 8 through the solidified cement slurry 9 to form a thin-walled cave combined pipe pile structure; in order to save labor and facilitate construction, a sawtooth 11 can be made at the bottom end of the pile tip 1 of the prestressed pipe pile 2, and the bottom end of the pile tip 1 of the prestressed pipe pile 2 can be made into a conical annular tube structure with a sawtooth 11. Example

[0023] In the specific implementation, first use the prestressed pipe pile 2 with an open pile tip 1 welded at the bottom to drill a hole to the top of the cave 3, but do not drill through the cave top wall 4. Then use the micro steel pipe pile 7 to continuously drill holes from the prestressed pipe pile 2 and pass through the cave top wall 4 of the cave 3 to the slightly weathered limestone layer 8 at the bottom of the cave 3. Then inject cement slurry 9 from the prestressed pipe pile 2 into the prestressed pipe pile 2 and the micro steel pipe pile 7. During grouting, the grouting pressure is controlled at about 2 MPa, so that the cement slurry 9 can flow out from the grouting hole 6 and wrap around the outer cylindrical surface of the micro steel pipe pile 7; at the same time, it is also necessary to avoid that part of the cement slurry 9 of the micro steel pipe pile 7 in the cave 3 is sprayed outward in a jet shape. During the grouting process, the grouting pipe connected to the grouting equipment can be repeatedly plugged in and out to ensure the uniformity and density of the cement slurry 9. The grouting operation is completed until the grouting surface 10 of the cement slurry 9 is higher than the top of the micro steel pipe pile 4 by a certain distance. When drilling into the micro steel pipe pile 7, the bottom end of the micro steel pipe pile 7 should be drilled into the slightly weathered limestone layer 8 by no less than 0.8m. The section of the micro steel pipe pile 7 located in the cave 3 is wrapped with the outer cylindrical surface by the cement slurry 9 overflowing from the micro steel pipe pile 7, which plays a good anti-corrosion role. The three rows of grouting holes 6 evenly distributed around the micro steel pipe pile 7 are denser, with a hole spacing of about 500mm, and the hole spacing of the remaining grouting holes 6 is about 1000mm. Grouting uses 52.5R pure cement slurry. Grouting can be layered from bottom to top. Grouting starts when the end of the grouting pipe connected to the ground grouting equipment is about 100mm away from the bottom of the hole. As the slurry surface rises, the grouting pipe is gradually lifted until the grouting surface 10 required by the design is reached. The grouting pressure is controlled at about 2mpa (can be adjusted according to specific circumstances). During the grouting process, the grouting pipe can be repeatedly plugged in and out to ensure the uniformity and density of the grouting.

[0024] The present invention effectively utilizes the characteristics of prestressed pipe piles and micro steel pipe piles. Prestressed pipe piles are easy to transport and have a fast construction speed, which greatly reduces the construction period. The micro steel pipe construction process is simple, which effectively reduces the waste of grouting. Since the bottom end of the micro steel pipe pile penetrates into the slightly weathered rock layer by no less than 0.8m, the safety and reliability are relatively high.

Claims

1. A construction method for a thin-walled cave composite pipe pile, characterized in that: The method is to drive a prestressed pipe pile with a pile tip at the lower end from the ground to a position above the top of the cave where the top wall of the cave has not been penetrated, and then stop driving; the soil at the top of the cave and around the prestressed pipe pile is blocked by the prestressed pipe pile; then the top wall of the cave is penetrated from the middle of the prestressed pipe pile by a micro-steel pipe pile with grouting holes evenly distributed around the pipe wall, and vertically penetrate the cave until it is driven into the slightly weathered limestone layer at the bottom of the cave, and the top of the micro-steel pipe pile is located in the prestressed pipe pile; then cement slurry is injected into the prestressed pipe pile and the micro-steel pipe pile from the top of the prestressed pipe pile through a grouting device; the slightly weathered limestone layer at the bottom of the micro-steel pipe pile is reinforced by the cement slurry, and at the same time, the outer circumferential surface of the micro-steel pipe pile located in the cave is wrapped by the cement slurry overflowing from the grouting holes around the micro-steel pipe pile to prevent corrosion of the micro-steel pipe pile; after the grouting is completed, the height of the grouting surface is higher than the top of the micro-steel pipe pile by a certain distance; The invention comprises a prestressed pipe pile (2) having a pile tip (1) at the lower end, characterized in that: the prestressed pipe pile (2) is inserted into the soil (5) at the top of the karst cave (3), and the position of the bottom end of the pile tip (1) of the prestressed pipe pile (2) is higher than or equal to the position of the karst cave top wall (4) above the top of the karst cave (3); a micro steel pipe pile (7) is arranged in the prestressed pipe pile (2), a grouting hole (6) is arranged on the pipe wall of the micro steel pipe pile (7), and the micro steel pipe pile (7) passes through the karst cave top wall (4) and vertically penetrates the karst cave (3) and is inserted into the slightly weathered limestone layer (5) at the bottom of the karst cave (3). 8), the top of the micro steel pipe pile (7) is located in the prestressed pipe pile (2) and is lower than the upper end of the prestressed pipe pile (2); cement slurry (9) is poured into the prestressed pipe pile (2) and the micro steel pipe pile (7), and the cement slurry (9) flows through the grouting hole (6) of the micro steel pipe pile (7) to the outer pipe wall of the micro steel pipe pile (7) and gradually solidifies on the outer pipe wall of the micro steel pipe pile (7); the micro steel pipe pile (7) is connected to the prestressed pipe pile (2) and the slightly weathered limestone layer (8) through the solidified cement slurry (9) to form a thin-wall karst cave combined pipe pile structure.

2. The construction method of the thin-walled cave combined pipe pile according to claim 1 is characterized by: The cement slurry adopts 52.5R pure cement slurry.

3. The construction method of the thin-walled cave combined pipe pile according to claim 1 is characterized by: When injecting cement slurry into the prestressed pipe piles and micro steel pipe piles, the grouting pressure of the grouting equipment should be adjusted within the range of 1.5 to 2.5 MPa according to the specific situation to prevent the cement slurry from jetting out of the grouting hole in the cave.

4. The construction method of the thin-walled cave combined pipe pile according to claim 1 is characterized by: When injecting cement slurry, the uniformity of grouting should be ensured.

5. The construction method of the thin-walled cave combined pipe pile according to claim 1 is characterized by: The depth of the micro steel pipe piles driven into the slightly weathered limestone layer is not less than 0.8 meters.

6. The construction method of the thin-walled cave combined pipe pile according to claim 1 is characterized by: The hole spacing of the three rows of grouting holes in the lower section of the micro steel pipe pile is 0.5 meters, and the remaining hole spacings are 1 meter.

7. The construction method of the thin-wall karst cave composite pipe pile according to claim 1 is characterized by: The diameter of the grouting hole is 10 mm.

8. The construction method of the thin-wall karst cave composite pipe pile according to claim 1 is characterized by: After the grouting is completed, the prestressed pipe piles and the micro steel pipe piles are left underground, and the micro steel pipe piles are used as reinforcement supports for crossing the cave.

9. The construction method of the thin-wall karst cave composite pipe pile according to claim 1 is characterized by: Saw teeth (11) are provided at the bottom end of the pile tip (1) of the prestressed pipe pile (2).

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