A construction structure and construction method for cast-in-place piles in karst cave geology

Abstract

The present invention mainly relates to the field of civil engineering, and specifically to a construction structure and construction method for cast-in-place piles under karst geological conditions. The present invention discloses a construction method for cast-in-place piles under karst geological conditions. During the construction of cast-in-place piles in karst geological conditions, a double-wall casing with relatively high structural strength is used to maintain the stability of the soil layer, reduce the risk of pile hole collapse, and ensure the safety of the project. A rotary drilling device is used to rotary drill a positioning pit at the bottom of the underground karst cave, and a placeholder component is placed in the positioning pit. The placeholder component has a fixed occupancy, which is used to replace part of the filling material in the underground karst cave, and can reduce the material consumption of the filling material during the backfilling process. That is, during the construction process of each cast-in-place pile in the entire project, the filling material usage equal to the volume of the placeholder component is reduced. The present invention can reduce the construction cost of cast-in-place piles, reduce the generation of construction waste, improve the material utilization rate, is convenient for construction, and has a good pile foundation forming effect.

Description

Technical Field

[0001] The present invention mainly relates to the field of civil engineering, and specifically relates to a cast-in-place pile construction structure and construction method under karst geology. Background Art

[0002] Underground karst is a geological process of cast-in-place pile construction under karst geology, which refers to the process in which carbon dioxide or other acidic substances in groundwater act on underground rocks, dissolve the rocks or some of the minerals therein, thereby creating caves, underground channels and other underground cavities.

[0003] During the construction process, in the face of geology with more developed underground karst and intercalated fault fracture zones, traditional technologies mostly adopt the repeated hole-forming construction process or the super-placing of plain concrete process. However, the repeated hole-forming construction process is likely to damage the geological structure near the cast-in-place pile and is prone to pile hole collapse accidents; while the super-placing of plain concrete process will lead to a large increase in the demand for concrete, and thus cause a substantial increase in the building material cost. Summary of the Invention

[0004] To solve the above problems, the present invention adopts the following technical solutions.

[0005] A cast-in-place pile construction structure under karst geology includes a rotary drilling rig and a double-wall casing. The double-wall casing includes an inner-wall casing and an outer-wall casing. The inner-wall casing and the outer-wall casing are connected to the robotic arm of the rotary drilling rig through a casing driving connector, and the casing driving connector is detachably connected to the inner-wall casing and the outer-wall casing through bolts.

[0006] Further, the inner diameter of the double-wall casing is 0.1 - 0.3 m larger than the designed diameter of the cast-in-place pile.

[0007] Further, the bottom of the outer-wall casing is provided with a shoe, and the outer surface of the shoe is provided with circumferentially arranged positioning protrusions.

[0008] The present invention also provides a cast-in-place pile construction method using the above cast-in-place pile construction structure under karst geology, and the steps are as follows:

[0009] S1 Determine the position of the cast-in-place pile and level the construction site;

[0010] S2 Install a hole mouth casing at the cast-in-place pile construction site;

[0011] S3 Install the double-wall casing on the casing driving connector of the rotary drilling rig, measure the verticality of the double-wall casing using a level, and at the same time, the rotary drilling rig adjusts the verticality of the double-wall casing to reach the preset range;

[0012] The rotary drilling equipment described in S4 performs rotary drilling operations. The casing driving connector drives the double-wall casing to be pressed into the pile hole, and the feeding speed of the double-wall casing is kept consistent with the feeding speed of the rotary drilling bit.

[0013] When the bottom of the double-wall casing described in S5 reaches the top surface of the underground karst cave, the casing driving connector stops driving the double-wall casing, and the rotary drilling bit of the rotary drilling equipment continues to rotary drill until a positioning pit is dug out on the bottom surface of the underground karst cave.

[0014] Withdraw the rotary drilling bit, use a hoisting device to place a placeholder member with a sling connected to the top surface in the positioning pit, and then put fillers into the underground karst cave.

[0015] Use a compaction device to compact the fillers.

[0016] The casing driving connector drives the double-wall casing to press down until the distance between the bottom of the double-wall casing and the bottom surface of the underground karst cave is ≤ 0.2 m, and the upper part of the side wall of the placeholder member is located in the bottom inner cavity of the double-wall casing.

[0017] Use a hoisting device to take out the placeholder member and the inner casing of the double-wall casing from the pile hole.

[0018] The rotary drilling equipment drives the rotary drilling bit to continue the rotary drilling operation.

[0019] When the outer casing reaches the preset depth, the casing driving connector stops driving the outer casing.

[0020] The rotary drilling equipment drives the rotary drilling bit until the rotary drilling bit reaches the preset depth, and then withdraws the rotary drilling bit.

[0021] Install a steel mesh in the pile hole and pour concrete.

[0022] After the concrete has hardened for 3 to 5 hours, withdraw the outer casing and the hole mouth casing.

[0023] Furthermore, both the top and bottom of the placeholder member are conical, and the middle part is cylindrical.

[0024] Furthermore, the pressure head of the compaction device has a groove, and the groove is adapted to the conical top surface of the placeholder member.

[0025] Furthermore, the conical bottom surface of the placeholder member is adapted to the taper of the top cutting end of the rotary drilling bit.

[0026] The beneficial effects of the present invention are as follows:

[0027] The double-wall casing has high structural strength, which can help maintain the stability of the soil layer, reduce the risk of pile hole collapse, and ensure the safety of the project.

[0028] The occupying member has a fixed occupation ratio and is used to replace part of the filling in the underground karst cave, which can reduce the material consumption of the filling during the backfilling process. That is, during the construction process of the entire project, the filling amount equal to the volume of the occupying member is reduced for each cast-in-place pile. The present invention can reduce the construction cost, reduce the generation of construction waste, improve the material utilization rate, is convenient for construction, and has a good forming effect of the cast-in-place pile. Description of the Drawings

[0029] Figure 1 It is a schematic overall sectional view of the rotary drilling of the pile hole;

[0030] Figure 2 It is a construction schematic diagram of the orifice guard plate;

[0031] Figure 3 It is a schematic diagram of the rotary drilling of the positioning pit;

[0032] Figure 4 It is a schematic diagram of the position of the positioning pit;

[0033] Figure 5 It is a construction schematic diagram of the occupying member;

[0034] Figure 6 It is a schematic diagram of the compaction of the filling;

[0035] Figure 7 It is a schematic diagram of the recovery of the filling;

[0036] Figure 8 It is a schematic diagram of the filling of the underground karst cave;

[0037] Figure 9 It is a schematic diagram of the rotary drilling of the rotary drilling bit;

[0038] Figure 10 It is a schematic diagram of the double-wall casing structure;

[0039] Figure 11 It is a schematic diagram of the installation structure of the double-wall casing and the rotary drilling bit.

[0040] Description of the Reference Numerals:

[0041] 01 Positioning pit, 1 Orifice casing, 2 Rotary drilling equipment, 21 Rotary drilling bit, 211 Bit driver, 22 Casing drive connector, 23 Manipulator, 3 Double-wall casing, 30 Bottom, 31 Inner wall casing, 311 Hoisting hole, 312 First installation hole, 32 Outer wall casing, 321 Second installation hole, 4 Occupying member, 5 Filling, 6 Compaction equipment, 7 Underground karst cave. Detailed Embodiments

[0042] The following further elaborates on the content of the present invention in conjunction with the accompanying drawings.

[0043] Referring to Figure 1 , this embodiment provides a construction process for cast-in-place piles in karst geology, and the steps are as follows:

[0044] S1 Based on the construction drawings provided by the design unit, measure and determine the position of the cast-in-place pile, and level the construction site near the cast-in-place pile;

[0045] S2 Referring to Figure 2 , install the hole mouth casing 1 by means of embedding or mechanical heavy pressing; for example, use a rotary drilling rig 2 to perform a pre-rotary drilling operation with a depth of 1 ± 0.4 meters, place the hole mouth casing 1 in the pre-rotary drilled pile hole, and then backfill and compact the inside of the pre-rotary drilled pile hole outside the hole mouth casing 1; or directly press the hole mouth casing 1 into the ground at the position of the pile hole by a hydraulic press; among them, the rotary drilling rig 2 is preferably a hydraulic rotary drilling rig.

[0046] S3 Referring to Figure 11 , install the double-wall casing 3 on the casing drive connector 22 of the rotary drilling rig 2 to make the double-wall casing 3 and the rotary drill bit 21 of the rotary drilling rig 2 coaxial; then use a level to immediately measure the verticality of the double-wall casing 3, and at the same time, the rotary drilling rig 2 indirectly adjusts the verticality of the casing drive connector 22 and the double-wall casing 3 to reach the preset range by adjusting the robotic arm 23; the double-wall casing 3 includes an inner wall casing 31 and an outer wall casing 32. Among them, the level is preferably a bubble level.

[0047] S4 Use the rotary drilling rig 2 to perform rotary drilling operations; detachably connect the robotic arm 23 where the rotary drill bit 21 of the rotary drilling rig 2 is located to the casing drive connector 22. When the rotary drill bit 21 feeds downward, the thrust is transmitted to the casing drive connector 22 through the robotic arm 23, further pushing the double-wall casing 3 into the pile hole; make the feeding speed of the double-wall casing 3 consistent with the feeding speed of the rotary drill bit 21;

[0048] S5 Referring to Figure 3 , when the bottom 30 of the double-wall casing 3 reaches the top surface of the underground karst cave 7, remove the bolts to stop driving the double-wall casing 3 by the casing drive connector 22, and the rotary drill bit 21 of the rotary drilling rig 2 continues to rotary drill to dig out a positioning pit 01 on the bottom surface of the underground karst cave 7; among them, before the rotary drilling construction, methods such as high-density electrical method, transient electromagnetic method, ground penetrating radar method or seismic imaging method are used to detect the positions of the top surface and the bottom surface of the underground karst cave 7 in advance. That is, the detection techniques for the rotary drilling depth are all existing technologies and will not be elaborated here.

[0049] S6 Referring to Figures 4 - 5, the rotary drilling equipment 2 drives the robotic arm 23 to extract the rotary drilling bit 21, and uses a lifting device (such as a crane) to place the placeholder member 4 with a sling connected to its top surface into the positioning pit 01. The lifting device lowers the hook until the sling connected to the placeholder member 4 is in a slack state; then, fillers 5 (such as backfill soil, superfluid concrete, etc.) are put into the underground karst cave 7 until the fillers 5 can fill the underground karst cave 7 and the height of the fillers 5 in the double-wall casing 3 is not less than 1.5 meters;

[0050] Refer to S7 Figure 6 , a compaction device 6 (such as a rammer) is used to compact the fillers 5, and the gap between the outer diameter of the pressure head of the compaction device 6 and the inner diameter of the double-wall casing 3 is not less than 0.1 meter to accommodate the sling; the bottom 30 of the sling is stacked at the top surface position of the placeholder member 4 and placed horizontally, and the middle and upper parts of the sling are located in the gap between the pressure head and the casing and placed longitudinally to prevent the sling from being cut by the pressure head and the double-wall casing 3; during the compaction process, fillers 5 are continuously put into the inner cavity of the double-wall casing 3 until the height of the compacted fillers 5 in the double-wall casing 3 is not less than 0.5 meter;

[0051] Refer to S8 Figure 7 , the casing drive connector 22 drives the double-wall casing 3 to press down until the bottom 30 of the double-wall casing 3 is ≤ 0.2 meter away from the bottom surface of the underground karst cave 7, so that the fillers 5 within the orthographic projection range of the double-wall casing 3 are completely cut or basically cut (the uncut part of the fillers 5 ≤ 20% of the height of the underground karst cave 7), and the upper part of the side wall of the placeholder member 4 is located within the inner cavity of the bottom 30 of the double-wall casing 3;

[0052] Refer to S9 Figure 7 、 10 , the casing drive connector 22 is removed, and the hook of the lifting device is used to hook the lifting hole 311 at the top end of the inner casing 31 of the double-wall casing 3. The lifting device is used to pull up the inner casing 31 of the double-wall casing 3 and the sling, so as to synchronously remove the placeholder member 4, the inner casing 31 and the fillers 5 within the inner casing 31 (the compacted fillers 5 and the inner casing 31 have a large frictional force and are difficult to separate); after the removed placeholder member 4 is cleaned of the adhered fillers, it can be reused; the outer casing 32 remains in the pile hole due to the large frictional force between it and the pile hole;

[0053] Refer to S10 Figure 8 , the rotary drilling equipment 2 drives the rotary drilling bit 21 to insert into the pile hole and continue the rotary drilling operation downward;

[0054] Refer to S11 Figure 9 , when the outer casing 32 reaches the preset depth, the casing drive connector 22 stops driving the outer casing 32;

[0055] S12 When the rotary drilling equipment 2 drives the rotary drilling bit 21 to reach the preset depth, the rotary drilling bit 21 is extracted;

[0056] S13 Install a steel mesh in the pile hole and pour concrete;

[0057] S14 After the concrete has hardened for 3 to 5 hours, the robotic arm 23 of the rotary drilling rig 2 withdraws the outer wall casing 32, and then uses a lifting device (such as a crane) to withdraw the hole mouth casing 1; the reinforced concrete cast-in-place pile remains in the pile hole and continues to harden and form.

[0058] Refer to Figure 10 , the bottom 30 of the outer wall casing 32 is provided with a shoe, and the outer surface of the shoe is provided with positioning protrusions arranged in a ring; the positioning protrusions can penetrate into the soil layer to improve the position stability of the outer wall casing 32.

[0059] Refer to Figure 11 , the casing drive connector 22 and the double-wall casing 3 are detachably connected by bolts. By removing the bolts, the double-wall casing 3 can be removed from the casing drive connector 22.

[0060] The inner diameter of the double-wall casing 3, that is, the inner diameter of the inner wall casing 31, is the designed pile diameter plus 0.2 m.

[0061] Before each time the rotary bit of the rotary drilling rig 2 is pressed into the double-wall casing 3, use a level to measure the verticality of the double-wall casing 3, and the rotary drilling rig 2 adjusts the vertical inclination of the casing to within 1.5%.

[0062] Refer to Figure 6 , the top and bottom of the occupying member 4 are both conical, and the middle part is cylindrical. The pressure head of the compaction device 6 has a groove, and the groove is adapted to the conical top surface of the occupying member 4; the conical bottom surface of the occupying member 4 is adapted to the taper of the top cutting end of the rotary bit 21; that is, the taper of the top cutting end of the rotary bit 21, the taper of the bottom surface of the positioning pit 01, and the taper of the bottom surface of the occupying member 4 are equal, so as to prevent the filler 5 from flowing into the gap between the occupying member 4 and the bottom surface of the positioning pit 01 and causing adhesion.

[0063] The outer side surface of the pressure head of the compaction device 6 is provided with rollers, and the rollers are used to reduce the friction between the pressure head and the inner wall of the double-wall casing 3.

[0064] Refer to Figure 10 , 11, the double-wall casing 3 is in the shape of two straight cylinders sleeved with each other, and the top end of the inner-wall casing 31 is higher than that of the outer-wall casing 32; a lifting hole 311 is opened at the top end of the inner-wall casing 31, and the height of the lifting hole 311 is higher than the top end of the outer-wall casing 32; at the same height in the upper parts of the inner-wall casing 31 and the outer-wall casing 32, a first mounting hole 312 and a second mounting hole 321 with the same axis and the same diameter are respectively opened; the double-wall casing 3 is connected to the bottom surface of the casing driving connector 22 through a positioning hole and a bolt in the positioning hole; the upper part of the rotary drilling bit 21 is connected to the bit driver 211, and the bit driver 211 is connected with a transmission gear set for driving the rotary drilling bit 21 to rotate, and the bit driver 211 is arranged at the front end of the robotic arm 23 of the rotary drilling equipment 2; the casing driving connector 22 and the bit driver 211 are connected through a hydraulic rod.

[0065] Referring to Figure 11 , the double-wall casing 3 is arranged outside the rotary drilling bit 21, and the diameter of the double-wall casing 3 is slightly larger than that of the rotary drilling bit 21; during the rotary drilling process, the spiral rotary drilling bit 21 generates a pulling force towards the deep part of the pile hole on itself, and this pulling force is transmitted to the double-wall casing 3 through the bit driver 211 and the hydraulic rod, so as to push the feeding speeds of the double-wall casing 3 and the rotary drilling bit 21 to be consistent.

[0066] In the traditional backfilling technology, it is necessary to fill the underground karst cave 7 with the filler 5, then press the casing down to the bottom surface of the underground karst cave 7, take out the filler 5 (such as incompletely hardened concrete) in the casing, or directly drill through the filler 5 (such as soil and stone) with the rotary drilling bit 21 while discharging the broken filler 5 residues. The backfilling and re-taking out of the filler 5 cause waste of construction materials, especially when using the expensive concrete backfilling technology, the waste is more serious. The present invention adopts the occupying member 4, and the occupying member 4 has a fixed occupancy and is used to replace a part of the filler 5 in the underground karst cave 7 and under the projection range of the double-wall casing 3, which can reduce the material consumption of the filler 5 and reduce the construction cost; that is, during the construction process, the filler consumption equal to the volume of the occupying member 4 is reduced for each cast-in-place pile.

[0067] Through the above specific embodiments, those skilled in the art of the present invention can easily implement the present invention. However, it should be understood that the present invention is not limited to the above specific embodiments. Based on the disclosed embodiments, those skilled in the art can arbitrarily combine different technical features to implement different technical solutions.

Claims

1. A method for constructing cast-in-place piles in karst geology, characterized in that: The steps are as follows, S1 Determine the location of the cast-in-place piles and level the construction site; S2 installs a hole casing (1) at the cast-in-place pile construction site; S3: installing the double-wall casing (3) on the casing drive connector (22) of the rotary drilling device (2), measuring the verticality of the double-wall casing (3) using a level, and adjusting the verticality of the double-wall casing (3) by the rotary drilling device (2) until it reaches a preset range; S4: the rotary drilling device (2) performs a rotary drilling operation, the casing drive connector (22) drives the double-wall casing (3) to be pressed into the pile hole, and the feed speed of the double-wall casing (3) is kept consistent with the feed speed of the rotary drilling drill bit (21); S5: when the bottom (30) of the double-wall casing (3) reaches the top surface of the underground cave (7), the casing drive connector (22) stops driving the double-wall casing (3), and the rotary drilling bit (21) of the rotary drilling device (2) continues to rotary drill until a positioning pit (01) is dug out on the bottom surface of the underground cave (7); S6: extracting the rotary drilling bit (21), placing a placeholder component (4) with a sling connected to the top surface in the positioning pit (01) using a lifting device, and then placing a filler (5) into the underground cave (7); S7: compacting the filler (5) using a compacting device (6); S8: the casing drive connector (22) drives the double-wall casing (3) to be pressed downward until the bottom (30) of the double-wall casing (3) is ≤0.2 m from the bottom surface of the underground cave (7), and the upper part of the side wall of the placeholder component (4) is located in the inner cavity of the bottom (30) of the double-wall casing (3); S9: Using a lifting device to remove the space-occupying member (4) and the inner wall casing (31) of the double-wall casing (3) from the pile hole; S10: the rotary drilling device (2) drives the rotary drilling drill bit (21) to continue the rotary drilling operation; S11: when the outer wall casing (32) reaches a preset depth, the casing drive connector (22) stops driving the outer wall casing (32); S12: the rotary drilling device (2) drives the rotary drilling bit (21) until the rotary drilling bit (21) reaches a preset depth, and then the rotary drilling bit (21) is pulled out; S13 installs a steel mesh in the pile hole and pours concrete; S14 After the concrete has hardened for 3 to 5 hours, the outer wall casing (32) and the hole casing (1) are removed.

2. The method for constructing cast-in-place piles in cave geology according to claim 1, characterized in that: Each time before the rotary drill bit of the rotary drilling device (2) is pressed into the double-wall casing (3), a level is used to measure the verticality of the double-wall casing (3), and the verticality of the casing is adjusted to reach a preset range.

3. The method for constructing cast-in-place piles in cave geology according to claim 1, characterized in that: The top and bottom of the place-occupying member (4) are both conical, and the middle part is cylindrical.

4. The method for constructing cast-in-place piles in cave geology according to claim 3, characterized in that: The pressure head of the compacting device (6) has a groove, which is adapted to the conical top surface of the spacer component (4).

5. The method for constructing cast-in-place piles in cave geology according to claim 3, characterized in that: The conical bottom surface of the space-occupying member (4) is adapted to the taper of the top cutting end of the rotary drilling drill bit (21).

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