Pile foundation karst cave construction device and method

Abstract

The invention belongs to the technical field of pile foundation construction, and particularly relates to a pile foundation karst cave construction device and method.The pile foundation karst cave construction device comprises a roadbed plate, an outer steel protection cylinder and an inner steel protection cylinder, a rotating steel cylinder is rotationally installed on the roadbed plate, and a plurality of abutting assemblies used for abutting against the inner steel protection cylinder are arranged in the circumferential direction of the rotating steel cylinder; the abutting assembly comprises an abutting screw rod, an internal thread transverse cylinder and a driving motor I used for driving the abutting screw rod to move in the radial direction of the rotating steel cylinder, a ball end head is arranged at the end, located in the rotating steel cylinder, of the abutting screw rod, and a plurality of concave parts matched with the ball end head are arranged on the peripheral wall of the inner steel protection cylinder; and at least three groups of positioning assemblies are arranged in the circumferential direction of the outer steel casing. According to the device, the positioning assembly can not only ensure the coaxiality of the outer steel casing and the inner steel casing, but also assist the abutting assembly to stably fix the inner steel casing. According to the pile foundation karst cave construction method, the construction device is adopted, the coaxiality of the outer steel casing and the inner steel casing can be ensured, the inner steel casing is rapidly fixed and released, and the pile foundation quality is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of pile foundation construction, and particularly relates to a pile foundation karst cave construction device and method. Background Technique

[0002] During bridge construction, various geological conditions will be encountered. When there are underground karst caves at the pile foundation construction site, the karst caves need to be treated. Moreover, usually, when there are underground karst caves, the sizes of the karst caves vary, the buried depths are quite different, and some are developed in a beaded shape. The geological conditions are very complex, belonging to the areas with relatively high geological disaster risks.

[0003] During the construction process of bridge pile foundations, phenomena such as slurry leakage and hammer deviation are likely to occur at the positions of karst caves. After the karst cave roof is penetrated, under the action of the water head difference between the upper pore water and the lower karst water, the groundwater level near the bored pile will change sharply. The upper sand layer is very likely to be lost into the karst cavity in a very short time, and a soil cave will be formed in the upper overburden layer, triggering the collapse of the ground surface near the pile hole. When the groundwater level near the pile hole changes greatly, due to the development of underground karst and soil caves in some sections, when the connectivity between karst caves is good, the ground surface within the influence radius of the groundwater drawdown funnel is extremely likely to trigger collapse, endangering the safety of surface buildings. Therefore, during pile foundation construction under karst geological conditions, the treatment measure of backfilling the karst cave is usually preferred, and the casing following technology is adopted during the construction process. For example, the Chinese invention patent application with the publication number CN108978642A discloses a construction method for treating karst caves in bridge piers with double steel casings and backfilling clay and crushed stones. After the outer steel casing sinks in place, bagged cement and wire mesh fragments are backfilled, and a small-stroke impact hammer is used to stir. After observing for 24 hours, a small drill hole penetrates the karst cave roof, the karst cave is filled with water, and after observing that everything is normal, the impact hammer makes a small stroke and gently and slowly penetrates the karst cave roof or drills through the karst cave roof, the inner steel casing is hoisted and placed, the karst cave is backfilled, and finally, the punching is filled by blowing and squeezing and impacts into the karst cave floor by 1 m, and the inner steel casing sinks to 1 m below the karst cave floor. However, the above construction method is applicable to the case of a single karst cave. If multiple karst caves are encountered during the pile hole drilling process, using the above construction method will result in a high risk of collapse of the lower karst cave.

[0004] In addition, during the follow-up construction of the casing, when the inner steel casing passes through the cave and contacts the rock surface, the bottom end of the inner steel casing cannot completely contact the rock surface. In addition, the rock surface is generally inclined. Therefore, there is often a large gap between the inner steel casing and the rock surface. If it is not consolidated, the above gap will become a passage between the pile hole and the outside of the pile during the rock rushing process, which is very likely to cause a deviated hole or an inclined hole when drilling and passing the inner steel casing foot, leaving quality risks. At present, the way to consolidate the blade foot of the inner steel casing is to use the characteristic of squeezing the hole wall during impact drilling, throw and fill stones and clay within the range of the blade foot of the inner steel casing, and use a 2-4m stroke for punching to make it dense and build a wall. Repeat this many times until the bottom of the hole is flat before continuing to rush in. This consolidation treatment method can certainly prevent buried drilling and avoid biased or inclined holes when passing through the foot of the inner steel casing. However, during the process of punching and compacting the wall, the stone and clay are squeezed out through the gap between the inner steel casing and the rock surface. The inner steel casing is subject to the squeezing force exerted on it by the stone and clay, and is prone to tilting, which places high demands on the stability of the fixing structure of the inner steel casing. Moreover, the inner steel casing needs to follow up the drilling, and the fixing and release of the inner steel casing are relatively frequent. The operation of releasing the inner steel casing with the ordinary fixing structure is relatively troublesome. In addition, the existing inner steel casing fixing structure cannot ensure that the inner steel casing is coaxial with the outer steel casing. Therefore, it is necessary to improve the existing casing structure and casing fixing structure. Summary of the invention

[0005] The present invention is intended to provide a pile foundation karst cave construction device, so as to realize the rapid fixing and releasing of an inner steel casing and ensure that the inner steel casing is coaxial with an outer steel casing.

[0006] In order to achieve the above-mentioned purpose, the scheme of the present invention is as follows: a pile foundation cave construction device comprises a roadbed, an outer steel casing and an inner steel casing, the roadbed is provided with a channel for the outer steel casing to pass through, a rotating steel cylinder is rotatably mounted on the roadbed, a plurality of tightening components for tightening the inner steel casing are arranged on the circumference of the rotating steel cylinder, the tightening components comprise a tightening screw, an internally threaded horizontal cylinder and a driving motor I, the tightening screw is threadedly connected with the internally threaded horizontal cylinder, a ball end is arranged at one end of the tightening screw located in the rotating steel cylinder, and the outer peripheral wall of the inner steel casing A plurality of recessed portions matching the ball end are provided on the outer sleeve, and a roller is axially slidably connected to one end of the tightening screw outside the rotating steel cylinder, and a driven gear is coaxially fixedly connected to the roller, and a driving gear I is coaxially fixedly connected to the output end of the driving motor I, and the driving gear I is meshed with the driven gear; at least three groups of positioning assemblies are provided on the circumference of the outer steel casing, and each group of positioning assemblies includes a positioning screw and an internally threaded positioning cylinder, and the positioning screw is threadedly connected to the internally threaded positioning cylinder, and a conical guide plate is provided at one end of the positioning screw located inside the outer steel casing.

[0007] The present invention also provides a pile foundation karst cave construction method, comprising the following steps:

[0008] S1. Bury the outer steel casing: Level the site, conduct survey and lofting to determine the center position of the pile foundation, and bury the outer steel casing. The bottom end of the outer steel casing is embedded in the bedrock surface. The outer steel casing is at least 50 cm above the ground, and the part of the outer steel casing above the ground is provided with the positioning assembly as described in Claim 1;

[0009] S2. Place the roadbed plate: Pass the roadbed plate as described in Claim 1 through the outer steel casing and place it on the ground. The channel of the roadbed plate is concentric with the outer steel casing. The rotating steel cylinder rotatably installed on the roadbed plate is located outside the outer steel casing, and the pressing assembly on the rotating steel cylinder is located above the outer steel casing;

[0010] S3. Drill a hole: Drill a hole within the range of the outer steel casing and drill to 1 m away from the top surface of the karst cave to form a hole;

[0011] S4. Lower the inner steel casing: Adjust the axial length d of the positioning screw rod on the outer steel casing located inside the outer steel casing so that the axial length d is equal to the difference between the inner radius of the outer steel casing and the outer radius of the inner steel casing. During the process of hoisting and lowering the inner steel casing, use the positioning assembly to ensure that the inner steel casing is coaxial with the outer steel casing, and then lower the inner steel casing until the bottom end of the inner steel casing contacts the bottom wall of the hole;

[0012] S5. Break through or drill through the roof of the karst cave: Use a chisel hammer with a small stroke, light hammer, and slowly break through or drill through the roof of the karst cave. The hole is connected to the karst cave, and continue to lower the inner steel casing until the bottom end of the inner steel casing contacts the bottom plate of the karst cave;

[0013] S6. Consolidate the cutting edge of the inner steel casing: Rotate the rotating steel cylinder so that the ball end of the pressing screw rod corresponds to the recessed part on the outer peripheral wall of the inner steel casing. Use the driving motor I to drive the roller to rotate forward, and then drive the pressing screw rod to rotate. The pressing screw rod moves radially inward along the rotating steel cylinder, and the ball end is embedded in the recessed part to fix the inner steel casing; Subsequently, throw crushed stones and clay into the inner steel casing, and repeatedly stamp to completely block the gap between the inner steel casing and the bottom plate of the karst cave;

[0014] S7. Chisel hammer drilling: Use the driving motor I to drive the roller to rotate in the reverse direction, and then drive the pressing screw rod to rotate. The pressing screw rod moves radially outward along the rotating steel cylinder to release the inner steel casing; Subsequently, conduct chisel hammer drilling, and the inner steel casing follows until it is 1 m away from the top surface of the karst cave;

[0015] S8. Filling the karst cave: Use a chipping hammer with a small stroke and light blows, slowly break through the roof of the karst cave or drill through it. Lower the inner steel casing to the top surface of the karst cave, fix the inner steel casing using the clamping assembly, throw crushed stones, clay, and cement into the inner steel casing, and repeatedly ram to compact the filling material. Inject mud into the inner steel casing, and the mud naturally seeps into the gaps between the crushed stones. Then, use the drill bit to impact through the karst cave with a small stroke and high frequency, squeezing the cement, clay, and crushed stones into the hole wall to form an artificial wall. If there is slurry leakage in the mudstone retaining wall in the karst cave, it should be backfilled again, repeatedly backfilled and repeatedly impacted until there is no more slurry leakage.

[0016] S9. Drilling to the bottom elevation of the pile: Release the inner steel casing by the clamping assembly, drill to the bottom elevation of the pile, and the inner steel casing follows up to the bottom elevation of the pile.

[0017] S10. Lower the steel reinforcement cage after hole cleaning.

[0018] S11. Pour concrete and pull out the inner steel casing upward: Pour the concrete in sections. That is, after pouring the concrete for a certain distance, pull out the inner steel casing upward for a certain distance, and then continue to pour the concrete until the inner steel casing is completely pulled out. When encountering a karst cave during the concrete pouring, the karst cave can be filled with concrete or the operation of filling the karst cave with crushed stones, clay, and cement in step S8 can be repeated.

[0019] During the above process, if the number of karst cave layers n is greater than 2, repeat steps S5 to S7 after step S7 until after drilling the last karst cave, perform steps S8 to S11.

[0020] The working principle and beneficial effects of this solution are as follows: In the pile foundation karst cave construction device in this solution, the clamping assembly on the rotating steel cylinder is used to quickly fix and release the inner steel casing. At the same time, the positioning assembly on the outer steel casing is used to make the outer and inner steel casings coaxial, ensuring the coaxiality of the outer and inner steel casings. Moreover, the positioning assembly can assist the clamping assembly to fix the inner steel casing, so that the inner steel casing has two limiting layers axially, thereby improving the stability of fixing the inner steel casing. Not only that, there are several recesses on the outer peripheral wall of the inner steel casing in this solution, and the spherical ends of the clamping screws in the clamping assembly can be embedded in the recesses, so that the clamping assembly can stably clamp the inner steel casing, and when the inner steel casing needs to be rotated, the inner steel casing can be rotated by rotating the rotating steel cylinder.

[0021] In addition, in the pile foundation karst cave construction method of this solution, the above-mentioned pile foundation karst cave construction device is adopted. During the construction process, the inner steel casing is limited on two levels in the axial direction by the pressing component and the positioning component, and the pressing component is used to quickly fix and release the inner steel casing, and the positioning component is used to ensure the coaxiality of the outer and inner steel casings, reduce or even avoid the inclination of the inner steel casing, so as to ensure the quality of the pile foundation. Moreover, in this solution, after the inner steel casing passes through all the karst caves on the designed pile foundation path, each karst cave is filled from bottom to top, avoiding the problem of increased risk of collapse of the lower karst cave caused by filling the upper karst cave first.

[0022] Optionally, a plurality of axial reinforcing ribs are provided on the inner peripheral wall of the rotating steel cylinder. In this solution, the axial reinforcing ribs are used to enhance the strength of the rotating steel cylinder.

[0023] Optionally, an inclination sensor is fixedly installed on the outer peripheral wall of the outer steel casing. In this solution, the inclination sensor is used to monitor the verticality of the outer steel casing to ensure that the inclination of the outer steel casing during the construction process does not exceed 1%.

[0024] Optionally, a driving motor II for driving the rotation of the rotating steel cylinder is fixedly installed on the roadbed slab. The output end of the driving motor II is coaxially and fixedly connected with a driving gear II, and an external gear ring meshing with the driving gear II is fixedly connected to the outer peripheral wall of the rotating steel cylinder. In this solution, the driving motor II is used to realize the rotation of the rotating steel cylinder.

[0025] Optionally, in step S8, the ratio of crushed stones, clay and cement is 1m 3 :1m 3 :0.5t, the diameter of the crushed stones is not less than 30 cm and not more than 50 cm, and the strength is not less than 30 MPa.

[0026] Optionally, the designed pile diameter is recorded as D m, the inner diameter of the outer steel casing is (D + 0.2) m, and the inner diameter of the inner steel casing is (D + 0.07) m; when 1 ≤ D ≤ 1.25 and the axial length L of the inner steel casing ≤ 10 m, the wall thickness of the outer and inner steel casings is 8 mm; when 1 ≤ D ≤ 1.25 and 10 m < the axial length L of the inner steel casing ≤ 25 m, or when 1.5 ≤ D ≤ 2 and the axial length L of the inner steel casing ≤ 10 m, the wall thickness of the outer and inner steel casings is 10 mm; when 1 ≤ D ≤ 1.25 and 25 m < the axial length L of the inner steel casing ≤ 40 m, or when 1.5 ≤ D ≤ 2 and 10 m < the axial length L of the inner steel casing ≤ 25 m, or when 2.2 ≤ D ≤ 2.5 and the axial length L of the inner steel casing ≤ 10 m, the wall thickness of the outer and inner steel casings is 12 mm; when 1 ≤ D ≤ 1.25 and 40 m < the axial length L of the inner steel casing ≤ 60 m, or when 1.5 ≤ D ≤ 2 and 25 m < the axial length L of the inner steel casing ≤ 40 m, or when 2.2 ≤ D ≤ 2.5 and 10 m < the axial length L of the inner steel casing ≤ 25 m, or when 2.8 ≤ D ≤ 3 and the axial length L of the inner steel casing ≤ 10 m, the wall thickness of the outer and inner steel casings is 14 mm; when 1.5 ≤ D ≤ 2 and 40 m < the axial length L of the inner steel casing ≤ 60 m, or when 2.2 ≤ D ≤ 2.5 and 25 m < the axial length L of the inner steel casing ≤ 40 m, or when 2.8 ≤ D ≤ 3 and 10 m < the axial length L of the inner steel casing ≤ 25 m, the wall thickness of the outer and inner steel casings is 16 mm; when 2.2 ≤ D ≤ 2.5 and 40 m < the axial length L of the inner steel casing ≤ 60 m, or when 2.8 ≤ D ≤ 3 and 25 m < the axial length L of the inner steel casing ≤ 40 m, the wall thickness of the outer and inner steel casings is 18 mm; when 2.8 ≤ D ≤ 3 and 40 m < the axial length L of the inner steel casing ≤ 60 m, the wall thickness of the outer and inner steel casings is 20 mm. In this solution, the appropriate wall thicknesses of the outer and inner steel casings are selected according to the designed pile diameter and the penetration depth of the inner steel casing. Description of the Drawings

[0027] Figure 1 It is a partial axial sectional view of the pile foundation karst cave construction device in the first embodiment of the present invention;

[0028] Figure 2 It is a top view of the pile foundation karst cave construction device in the first embodiment of the present invention;

[0029] Figure 3 It is a partial circumferential sectional view when the inner steel casing is fixed by the clamping assembly in the first embodiment of the present invention;

[0030] Figure 4 It is a structural schematic diagram when the inner steel casing reaches the bottom wall of the hole in step S4 of the first embodiment of the present invention;

[0031] Figure 5Structural schematic diagram of fixedly connecting the blade foot of the inner steel casing in step S6 of Embodiment 1 of the present invention;

[0032] Figure 6 Structural schematic diagram after piercing or drilling through the karst cave roof in step S8 of Embodiment 1 of the present invention;

[0033] Figure 7 Structural schematic diagram after filling the bottom karst cave in step S8 of Embodiment 1 of the present invention;

[0034] Figure 8 Structural schematic diagram after the first concrete pouring in step S11 of Embodiment 1 of the present invention;

[0035] Figure 9 Structural schematic diagram after the second concrete pouring in step S11 of Embodiment 1 of the present invention;

[0036] Figure 10 Structural schematic diagram after filling the upper karst cave after the concrete is poured to the bottom surface of the upper karst cave in step S11 of Embodiment 1 of the present invention;

[0037] Figure 11 Structural schematic diagram after the inner steel casing is lowered after filling the upper karst cave in step S11 of Embodiment 1 of the present invention;

[0038] Figure 12 Structural schematic diagram after the concrete pouring is completed in step S11 of Embodiment 1 of the present invention;

[0039] Figure 13 Structural schematic diagram after the concrete pouring is completed in step S11 of Embodiment 2 of the present invention;

[0040] Figure 14 Top view of the pile foundation karst cave construction device in Embodiment 3 of the present invention. Detailed implementation manner

[0041] The following is further detailed through specific implementation manners:

[0042] The marks in the specification drawings include: roadbed slab 1, outer steel casing 2, inner steel casing 3, recessed part 301, rotating steel cylinder 4, pressing component 5, pressing screw 501, internal thread cross cylinder 502, driving motor I 503, spherical end 504, rotating roller 505, cross groove 5051, cross block 506, driven gear 507, driving gear I 508, mounting bracket 509, driving motor II 6, driving gear II 7, external gear ring 8, positioning component 9, positioning screw 901, internal thread positioning cylinder 902, conical guide plate 903, inclination sensor 10.

[0043] Embodiment 1

[0044] This embodiment is basically as follows Figure 1 , Figure 2 and Figure 3 shown: The pile foundation karst cave construction device includes a roadbed slab 1, an outer steel casing 2 and an inner steel casing 3. The roadbed slab 1 is provided with a passage for the outer steel casing 2 to pass through; a rotating steel cylinder 4 is rotatably installed on the roadbed slab 1 through a bearing. A plurality of tightening components 5 for pressing against the inner steel casing 3 are arranged on the circumference of the rotating steel cylinder 4. In this embodiment, the number of the tightening components 5 is four groups, and the four groups of tightening components 5 are evenly distributed along the circumference of the rotating steel cylinder 4. Each group of tightening components 5 includes a tightening screw 501, an internally threaded cross cylinder 502 and a driving motor I 503. The internally threaded cross cylinder 502 penetrates through the rotating steel cylinder 4 along the radial direction of the rotating steel cylinder 4 and is welded to the rotating steel cylinder 4. The tightening screw 501 is threadedly connected to the internally threaded cross cylinder 502. A spherical end 504 is integrally formed at one end of the tightening screw 501 located inside the rotating steel cylinder 4; a plurality of recessed portions 301 that fit with the spherical end 504 are arranged on the outer peripheral wall of the inner steel casing 3. In this embodiment, the plurality of recessed portions 301 on the outer peripheral wall of the inner steel casing 3 are divided into four columns and distributed along the axial direction of the inner steel casing 3, so that the spherical ends 504 on the tightening screws 501 in the four groups of tightening components 5 can all be embedded into the corresponding recessed portions 301, thereby realizing the fixation of the inner steel casing 3. One end of the tightening screw 501 located outside the rotating steel cylinder 4 is axially slidably connected to a rotating roller 505. Specifically, a cross block 506 is integrally formed at one end of the tightening screw 501 located outside the rotating steel cylinder 4. A cross groove 5051 for the cross block 506 to slide is provided on the rotating roller 505; the rotating roller 505 is coaxially and fixedly connected to a driven gear 507, and the output end of the driving motor I 503 is coaxially and fixedly connected to a driving gear I 508. The driving gear I 508 meshes with the driven gear 507. The rotating roller 505 is rotatably installed on a mounting frame 509, and both the mounting frame 509 and the driving motor I 503 are fixedly installed on the outer peripheral wall of the rotating steel cylinder 4.

[0045] A driving motor II 6 for driving the rotating steel cylinder 4 to rotate is fixedly installed on the roadbed slab 1. The output end of the driving motor II 6 is coaxially and fixedly connected to a driving gear II 7, and an external gear ring 8 that meshes with the driving gear II 7 is fixedly connected to the outer peripheral wall of the rotating steel cylinder 4. A plurality of axial reinforcing ribs are welded on the inner peripheral wall of the rotating steel cylinder 4 to enhance the strength of the rotating steel cylinder 4.

[0046] At least three groups of positioning components 9 are provided on the circumference of the outer steel casing 2. In this embodiment, the number of the positioning components 9 is three groups, and the three groups of positioning components 9 are evenly distributed along the axial direction of the outer steel casing 2. Each group of positioning components 9 includes a positioning screw 901 and an internally threaded positioning cylinder 902. The internally threaded positioning cylinder 902 penetrates the outer steel casing 2 along the radial direction of the outer steel casing 2 and is welded to the outer steel casing 2. The positioning screw 901 is in threaded connection with the internally threaded positioning cylinder 902. A conical guide plate 903 is welded to one end of the positioning screw 901 located inside the outer steel casing 2. The conical guide plate 903 is used to guide the inner steel casing 3.

[0047] This embodiment also provides a construction method for a pile foundation karst cave. This construction method uses the above-mentioned construction device. Specifically, this construction method includes the following steps:

[0048] S1. Bury the outer steel casing: Level the site, measure and set out the lines, determine the center position of the pile foundation, and bury the outer steel casing 2. The bottom end of the outer steel casing 2 is embedded in the bedrock surface, and the outer steel casing 2 is at least 50 cm above the ground. The positioning components 9 in the above-mentioned construction device are provided on the part of the outer steel casing 2 above the ground.

[0049] S2. Place the roadbed slab: Pass the roadbed slab 1 through the outer steel casing 2 and place it on the ground. The channel of the roadbed slab 1 is concentric with the outer steel casing 2. The rotating steel cylinder 4 rotatably installed on the roadbed slab 1 is located outside the outer steel casing 2, and the pressing component 5 on the rotating steel cylinder 4 is located above the outer steel casing 2.

[0050] S3. Drill a hole: Drill a hole within the range of the outer steel casing 2 and drill to a distance of 1 m from the top surface of the karst cave to form a hole.

[0051] S4. Lower the inner steel casing: Adjust the axial length of the positioning screw 901 located inside the outer steel casing 2 in the positioning component 9 (this operation can also be performed when burying the outer steel casing 2). Specifically, rotate the positioning screw 901 so that the axial length d of the positioning screw 901 located inside the outer steel casing 2 is equal to the difference between the inner radius of the outer steel casing 2 and the outer radius of the inner steel casing 3. At the same time, adjust the axial length of the pressing screw 501 located inside the rotating steel cylinder 4 in the pressing component 5. Specifically, start the driving motor I 503, drive the roller 505 to rotate through the driving gear I 508 and the driven gear 507, and then drive the pressing screw 501 to rotate, so that the pressing screw 501 moves along the radial direction of the rotating steel cylinder 4, so that the axial length of the pressing screw 501 located inside the rotating steel cylinder 4 is equal to the difference between the inner radius of the rotating steel cylinder 4 and the outer radius of the inner steel casing 3, that is, the spherical end 504 on the pressing screw 501 just contacts the outer peripheral wall of the inner steel casing 3. Then lower the inner steel casing 3 until the bottom end of the inner steel casing 3 contacts the bottom wall of the hole, as Figure 4As shown in the figure. In this way, during the hoisting and lowering process of the inner steel casing 3, under the guiding action of the conical guiding plate 903, the inner steel casing 3 quickly becomes coaxial with the outer steel casing 2. Moreover, the inner steel casing 3 is limited axially by the positioning screw 901 and the tightening screw 501, and no deviation will occur during the lowering process, and the lowering is smooth.

[0052] S5. Penetrate or drill through the karst cave roof: Use a small stroke and light hammer of the impact hammer to slowly penetrate or drill through the karst cave roof. The hole is connected to the karst cave, and continue to lower the inner steel casing 3 until the bottom end of the inner steel casing 3 contacts the bottom plate of the karst cave.

[0053] S6. Consolidate the blade foot of the inner steel casing 3: Start the driving motor II 6, and drive the rotation of the rotating cylinder 4 through the driving gear II 7 and the external gear ring 8, thereby driving the rotation of the tightening assembly 5. Wait until the spherical end 504 of the tightening screw 501 corresponds to the recessed part 301 on the outer peripheral wall of the inner steel casing 3, and then stop the driving motor II 6; Start the driving motor I 503, and drive the forward rotation of the roller 505 through the driving gear I 508 and the driven gear 507, thereby driving the rotation of the tightening screw 501. The tightening screw 501 moves radially inward along the rotating cylinder 4 until the spherical end 504 is embedded in the corresponding recessed part 301, and then stop the driving motor I 503 to fix the inner steel casing 3 (before starting the driving motor I 503, finely adjust the axial position of the inner steel casing 3 so that the spherical end 504 is aligned with the corresponding recessed part 301); Subsequently, fill the inner steel casing 3 with crushed stones and clay, and repeatedly stamp until the crushed stones and clay completely block the gap between the inner steel casing 3 and the bottom plate of the karst cave, as Figure 5 shown.

[0054] S7. Impact hammer drilling: Start the driving motor I 503 again, and drive the reverse rotation of the roller 505 through the driving gear I 508 and the driven gear 507, so that the tightening screw 501 moves radially outward along the rotating cylinder 4 to reset, and the spherical end 504 is separated from the recessed part 301, releasing the inner steel casing 3; Subsequently, carry out impact hammer drilling, and the inner steel casing 3 follows up until it is 1 m away from the top surface of the karst cave.

[0055] S8. Fill the karst cave: Use a small stroke and light hammer of the impact hammer to slowly penetrate or drill through the karst cave roof. Lower the inner steel casing 3 to the top surface of the karst cave, and use the tightening assembly 5 to fix the inner steel casing 3, as Figure 6 shown. Fill the inner steel casing 3 with crushed stones, clay and cement, and repeatedly stamp to densify the filler; Inject mud into the inner steel casing 3, and the mud naturally soaks into the gaps between the crushed stones. Then, use a drill bit to impact through the karst cave with a small stroke and high frequency, and squeeze the cement, clay and crushed stones into the hole wall to realize artificial wall building, as Figure 7 shown; If slurry leakage occurs in the mudstone retaining wall in the karst cave, it should be backfilled again, repeatedly backfilled and repeatedly impacted until there is no more slurry leakage. Among them, the ratio of crushed stones, clay and cement is 1 m3 : 1 m 3 : 0.5 t, the diameter of the riprap is not less than 30 cm and not more than 50 cm, and the strength is not less than 30 MPa.

[0056] S9. Drilling to the bottom elevation of the pile: Release the inner steel casing 3 of the pressing assembly 5, drill to the bottom elevation of the pile, and the inner steel casing 3 follows up to the bottom elevation of the pile.

[0057] S10. Lower the steel reinforcement cage after hole cleaning.

[0058] S11. Pour concrete and pull out the inner steel casing upward: The concrete is poured in sections. That is, after the concrete is poured for a certain distance, the inner steel casing 3 is pulled out upward for a certain distance, and then the concrete is continuously poured. As Figures 8 - 9 shown, until the inner steel casing 3 is completely pulled out; when a karst cave is encountered during the concrete pouring, the karst cave can be filled with concrete or the operation of filling the karst cave with riprap, clay and cement in step S8 can be repeated. In this embodiment, the operation of filling the karst cave with riprap, clay and cement in step S8 is used to fill the karst cave. As Figures 10 - 11 shown, after the filling is completed, the concrete is continuously poured until the concrete pouring is completed, as Figure 12 shown.

[0059] During the above process, when the number of karst cave layers n > 2, steps S5 to S7 are repeated after step S7 until step S8 to S11 are carried out when drilling to the last karst cave.

[0060] For example, when n = 3, a pile foundation karst cave construction method provided in this embodiment includes the following steps: Step S1 → Step S2 → Step S3 → Step S4 → Step S5 → Step S6 → Step S7 → Step S5 → Step S6 → Step S7 → Step S8 → Step S9 → Step S10 → Step S11.

[0061] In addition, during the above process, the selection of the inner diameters and wall thicknesses of the outer steel casing 2 and the inner steel casing 3 follows the following rules: The designed pile diameter is recorded as D m. The inner diameter of the outer steel casing 2 is (D + 0.2) m, and the inner diameter of the inner steel casing 3 is (D + 0.07) m. When 1 ≤ D ≤ 1.25 and the axial length L of the inner steel casing 3 (the axial length L refers to the following-in depth of the inner steel casing 3) ≤ 10 m, the wall thicknesses of the outer and inner steel casings are 8 mm. When 1 ≤ D ≤ 1.25 and 10 m < the axial length L of the inner steel casing 3 ≤ 25 m, or when 1.5 ≤ D ≤ 2 and the axial length L of the inner steel casing 3 ≤ 10 m, the wall thicknesses of the outer and inner steel casings are 10 mm. When 1 ≤ D ≤ 1.25 and 25 m < the axial length L of the inner steel casing 3 ≤ 40 m, or when 1.5 ≤ D ≤ 2 and 10 m < the axial length L of the inner steel casing 3 ≤ 25 m, or when 2.2 ≤ D ≤ 2.5 and the axial length L of the inner steel casing 3 ≤ 10 m, the wall thicknesses of the outer and inner steel casings are 12 mm. When 1 ≤ D ≤ 1.25 and 40 m < the axial length L of the inner steel casing 3 ≤ 60 m, or when 1.5 ≤ D ≤ 2 and 25 m < the axial length L of the inner steel casing 3 ≤ 40 m, or when 2.2 ≤ D ≤ 2.5 and 10 m < the axial length L of the inner steel casing 3 ≤ 25 m, or when 2.8 ≤ D ≤ 3 and the axial length L of the inner steel casing 3 ≤ 10 m, the wall thicknesses of the outer and inner steel casings are 14 mm. When 1.5 ≤ D ≤ 2 and 40 m < the axial length L of the inner steel casing 3 ≤ 60 m, or when 2.2 ≤ D ≤ 2.5 and 25 m < the axial length L of the inner steel casing 3 ≤ 40 m, or when 2.8 ≤ D ≤ 3 and 10 m < the axial length L of the inner steel casing 3 ≤ 25 m, the wall thicknesses of the outer and inner steel casings are 16 mm. When 2.2 ≤ D ≤ 2.5 and 40 m < the axial length L of the inner steel casing 3 ≤ 60 m, or when 2.8 ≤ D ≤ 3 and 25 m < the axial length L of the inner steel casing 3 ≤ 40 m, the wall thicknesses of the outer and inner steel casings are 18 mm. When 2.8 ≤ D ≤ 3 and 40 m < the axial length L of the inner steel casing 3 ≤ 60 m, the wall thicknesses of the outer and inner steel casings are 20 mm.

[0062] In this embodiment, the inner steel casing 3 is limited and fixed by using the clamping assembly 5 on the rotating steel cylinder 4 and the positioning assembly 9 on the outer steel casing 2, so as to realize the rapid fixation of the inner steel casing 3 and improve the stability of the fixation of the inner steel casing 3. Moreover, the clamping assembly 5 can be used to quickly fix and release the inner steel casing 3, and the operation is simple, only need to start the driving motor I 503; the positioning assembly 9 can ensure the coaxiality of the outer and inner steel casings, so as to avoid the inclination of the inner steel casing 3 relative to the outer steel casing 2 and ensure the quality of the pile foundation. Not only that, in this embodiment, the rotating steel cylinder 4 can rotate driven by the driving motor II 6. Thus, when the clamping assembly 5 fixes the inner steel casing 3 (the spherical end 504 is embedded in the corresponding recess 301), the rotating steel cylinder 4 can drive the inner steel casing 3 to rotate, so as to realize the rotational extraction of the inner steel casing 3 (first rotate and then extract), which is more conducive to the extraction work of the inner steel casing 3. Thus, the pile foundation karst cave construction in this embodiment is safer and faster, and the karst caves are filled one by one from bottom to top, avoiding the problem of high risk of collapse of the lower karst cave caused by the filling of the upper karst cave first.

[0063] Embodiment 2

[0064] The difference between this embodiment and Embodiment 1 is that: as Figure 13 shown, in step S11 of this embodiment, the karst caves encountered are filled with concrete during the concrete pouring.

[0065] Embodiment 3

[0066] The difference between this embodiment and Embodiment 1 is that: as Figure 14 shown, in this embodiment, an inclination sensor 10 is fixedly installed on the outer peripheral wall of the outer steel casing 2. In this embodiment, the inclination sensor 10 is used to monitor the verticality of the outer steel casing 2 to ensure that the inclination of the outer steel casing 2 does not exceed 1% during the construction process, and further ensure that the inclination of the inner steel casing 3 does not exceed 1%.

[0067] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this embodiment. Common knowledge such as specific structures and characteristics known in the art is not described in detail here. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention belongs before the filing date or the priority date, can know all the existing technologies in this field, and have the ability to apply the conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, combine their own abilities to improve and implement this solution. Some typical well-known structures or well-known methods should not become obstacles for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can also be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the present invention. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A pile foundation cave construction device, comprising a roadbed, an outer steel casing and an inner steel casing, characterized in that: The roadbed plate is provided with a channel for the outer steel casing to pass through, and a rotating steel cylinder is rotatably installed on the roadbed plate. A plurality of tightening components for tightening the inner steel casing are provided on the circumference of the rotating steel cylinder. The tightening components include a tightening screw, an internally threaded cross cylinder and a driving motor I. The tightening screw is threadedly connected to the internally threaded cross cylinder, and a ball end is provided at one end of the tightening screw located in the rotating steel cylinder. A plurality of recessed portions that fit with the ball end are provided on the outer peripheral wall of the inner steel casing. A roller is axially slidably connected to one end of the tightening screw located outside the rotating steel cylinder, and the roller is coaxially fixedly connected to a driven gear. The output end of the driving motor I is coaxially fixedly connected to a driving gear I, and the driving gear I is meshed with the driven gear; at least three groups of positioning components are provided on the circumference of the outer steel casing, and each group of positioning components includes a positioning screw and an internally threaded positioning cylinder. The positioning screw is threadedly connected to the internally threaded positioning cylinder, and a conical guide plate is provided at one end of the positioning screw located in the outer steel casing.

2. The pile foundation cave construction device according to claim 1, characterized in that: A plurality of axial reinforcing ribs are arranged on the inner peripheral wall of the rotating steel cylinder.

3. The pile foundation cave construction device according to claim 1, characterized in that: An inclination sensor is fixedly mounted on the outer peripheral wall of the outer steel casing.

4. The pile foundation cave construction device according to claim 1, characterized in that: A driving motor II for driving the rotating steel cylinder is fixedly installed on the road base plate, the output end of the driving motor II is coaxially fixedly connected with a driving gear II, and an outer gear ring meshing with the driving gear II is fixedly connected to the outer peripheral wall of the rotating steel cylinder.

5. The pile foundation cave construction method is characterized by: The following steps are involved: S1. Burying the outer steel casing: leveling the site, measuring and setting out, determining the center position of the pile foundation, burying the outer steel casing, the bottom end of the outer steel casing is embedded in the bedrock surface, the outer steel casing is at least 50 cm above the ground, and the portion of the outer steel casing above the ground is provided with a positioning assembly as described in claim 1; S2. Placing the roadbed plate: placing the roadbed plate as claimed in claim 1 on the ground after passing through the outer steel casing, the channel of the roadbed plate is concentric with the outer steel casing, the rotating steel cylinder rotatably mounted on the roadbed plate is located outside the outer steel casing, and the tightening assembly on the rotating steel cylinder is located above the outer steel casing; S3, drilling: drilling within the outer steel casing and drilling to 1m from the top of the cave to form a hole; S4. Lowering the inner steel casing: adjust the axial length d of the positioning screw on the outer steel casing inside the outer steel casing so that the axial length d is equal to the difference between the inner radius of the outer steel casing and the outer radius of the inner steel casing. During the process of hoisting and lowering the inner steel casing, use the positioning assembly to ensure that the inner steel casing is coaxial with the outer steel casing, and then lower the inner steel casing until the bottom end of the inner steel casing contacts the bottom wall of the hole; S5. Punch or drill through the cave roof: The hammer uses a small stroke and a light hammer to slowly punch through or drill through the cave roof, so that the hole is connected to the cave, and the inner steel casing is continuously lowered until the bottom end of the inner steel casing contacts the cave floor; S6. Inner steel casing blade foot consolidation: Rotate the rotating steel cylinder so that the ball end of the tightening screw corresponds to the concave portion on the outer peripheral wall of the inner steel casing, and use the driving motor I to drive the roller to rotate in the positive direction, thereby driving the tightening screw to rotate, and the tightening screw moves inward along the radial direction of the rotating steel cylinder, and the ball end is embedded in the concave portion to fix the inner steel casing; then, throw and fill stones and clay into the inner steel casing, and repeatedly punch so that the stones and clay completely block the gap between the inner steel casing and the cave floor; S7, hammer drilling: drive motor I is used to drive the roller to rotate in the opposite direction, thereby driving the tightening screw to rotate, and the tightening screw moves outward along the radial direction of the rotating steel cylinder to release the inner steel casing; then, the hammer drills, and the inner steel casing follows, until it is 1m away from the top of the cave; S8. Filling the cave: Use a hammer with a small stroke to lightly hammer and slowly strike to break through the cave roof or drill through the cave roof, lower the inner steel casing to the top of the cave, fix the inner steel casing with a tightening assembly, throw and fill stone flakes, clay and cement into the inner steel casing, and repeatedly punch to compact the filling; inject mud into the inner steel casing, and the mud naturally penetrates into the gaps between the stone flakes. Then, use a drill bit with a small stroke and high frequency to impact through the cave, squeeze cement, clay and stone flakes into the hole wall, and realize artificial wall building; if there is leakage of mud and stone wall in the cave, it should be backfilled again, and the backfilling and impact are repeated until there is no leakage; S9, drilling to the pile bottom elevation: the tightening assembly releases the inner steel casing, drilling to the pile bottom elevation, and the inner steel casing follows to the pile bottom elevation; S10, lower the steel cage after cleaning the hole; S11, pouring concrete and pulling out the inner steel casing upwards: concrete is poured in sections, that is, after pouring concrete for a certain distance, the inner steel casing is pulled out upwards for a certain distance, and then the concrete is poured again until the inner steel casing is completely pulled out; if a cave is encountered during the concrete pouring, the cave can be filled with concrete or the operation of filling the cave with stone flakes, clay and cement in step S8 can be repeated; In the above process, if the number of cave layers n is greater than 2, steps S5 to S7 are repeated after step S7 until the last cave is drilled and steps S8 to S11 are performed.

6. The pile foundation karst cave construction method according to claim 5, characterized in that: In step S8, the ratio of stone, clay and cement is 1m 3 :1m 3 :0.5t, the diameter of the stone is not less than 30cm and not more than 50cm, and the strength is not less than 30MPa.

7. The pile foundation cave construction method according to claim 5, characterized in that: The design pile diameter is recorded as D m, the inner diameter of the outer steel casing is (D+0.2) m, and the inner diameter of the inner steel casing is (D+0.07) m; when 1≤D≤1.25 and the axial length of the inner steel casing L≤10 m, the wall thickness of the outer and inner steel casings is 8 mm; when 1≤D≤1.25 and 10 m < the axial length of the inner steel casing L≤25 m, or when 1.5≤D≤2 and the axial length of the inner steel casing L≤10 m, the wall thickness of the outer and inner steel casings is 10 mm; when 1≤D ≤1.25 and 25m<the axial length of the inner steel casing L≤40m, or when 1.5≤D≤2 and 10m<the axial length of the inner steel casing L≤25m, or when 2.2≤D≤2.5 and the axial length of the inner steel casing L≤10m, the wall thickness of the outer and inner steel casings is 12mm; when 1≤D≤1.25 and 40m<the axial length of the inner steel casing L≤60m, or when 1.5≤D≤2 and 25m<the axial length of the inner steel casing L ≤40m, or when 2.2≤D≤2.5 and 10m<the axial length L of the inner steel casing≤25m, or when 2.8≤D≤3 and the axial length L of the inner steel casing≤10m, the wall thickness of the outer and inner steel casings is 14mm; when 1.5≤D≤2 and 40m<the axial length L of the inner steel casing≤60m, or when 2.2≤D≤2.5 and 25m<the axial length L of the inner steel casing≤40m, or when 2.8≤D≤3 and 10 When m is less than the axial length L of the inner steel casing and is less than 25m, the wall thickness of the outer and inner steel casings is 16mm; when 2.2≤D≤2.5 and 40m is less than the axial length L of the inner steel casing and is less than 60m, or when 2.8≤D≤3 and 25m is less than the axial length L of the inner steel casing and is less than 40m, the wall thickness of the outer and inner steel casings is 18mm; when 2.8≤D≤3 and 40m is less than the axial length L of the inner steel casing and is less than 60m, the wall thickness of the outer and inner steel casings is 20mm.

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