Pile foundation construction method suitable for karst area

Abstract

The invention belongs to the technical field of pile foundation construction, and particularly relates to a pile foundation construction method suitable for a karst area, which comprises the following steps: (1) leveling the ground, measuring and setting out: after determining a pile position, displaying a pile foundation central point by adopting a pile foundation positioning tool; (2) exploration of rock stratum properties; (3) lowering an outer pile casing; (4) drilling; (5) lowering the inner pile casing; (6) hole cleaning; (7) pouring concrete; (8) pulling out the pile casing; (9) detecting the quality of a pile foundation and a formed pile; wherein in the lowering process of the outer pile casing and the inner pile casing and in the drilling process, centering is achieved through the pile foundation positioning tool. The pile foundation positioning tool is adopted to display the center point of the pile foundation, whether the outer pile casing, the inner pile casing and the drill bit of the rotary drilling rig are centered with the center of the pile foundation or not is rapidly judged, the construction efficiency is improved, and the phenomena of hole deviation and deviation are avoided; meanwhile, the outer pile casing can support the hole opening, the inner pile casing can support the hole wall of the pile hole, and hole collapse is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of pile foundation construction, and in particular relates to a pile foundation construction method suitable for karst areas. Background Art

[0002] Karst mainly refers to the geological effects of chemical dissolution and mechanical destruction of soluble rocks by groundwater and surface water. Surface water and groundwater usually have a dissolving effect on soluble rocks, causing a series of karst landforms of different shapes and sizes, including underground rivers, karst fissures, sinkholes, funnels, karst depressions, beaded caves and other landforms. Therefore, in karst areas, pile foundation construction will be affected by geology and have problems such as skewed holes and collapsed holes, thus affecting the quality of pile foundations. Specifically, during the construction of pile foundation drilling, the vibration caused by the drill bit encountering different types of underground soil and rock layers during the construction process, and the weight of the construction machinery itself causing the soil layer around the pile hole to fall off, etc., resulting in deviations in the layout positioning, resulting in inaccurate verification of the drill bit center, resulting in skewed holes and offset positions. In addition, due to the uneven texture of the soil layer in the karst area, the loose soil layer around the hole wall is disturbed during the drilling process, the stability of the hole wall is poor, and the hole collapse phenomenon is prone to occur, which may cause the thickness of the pile bottom sediment to be too high. In serious cases, it may cause waste holes, broken piles, waste piles and other accidents, resulting in secondary construction and increased construction costs. Therefore, how to effectively reduce the karst hazards and ensure the smooth progress of pile foundation projects in karst areas has become a key technical problem that needs to be solved urgently. Summary of the invention

[0003] The invention aims to provide a pile foundation construction method suitable for karst areas, so as to solve the problem that pile foundation deviation and deviation easily occur in pile foundation construction in karst areas.

[0004] In order to achieve the above object, the scheme of the present invention is: a pile foundation construction method suitable for karst areas, comprising the following steps:

[0005] S1. Level the ground and measure and lay out: After leveling the ground, calculate the coordinates of the center point of the pile foundation according to the coordinates provided in the design drawings. According to the coordinates of the control piles at the construction site, use a total station to accurately lay out the pile position, and use a pile foundation positioning tool to display the center point of the pile foundation; the pile foundation positioning tool includes a positioning cylinder, a positioning ear plate is provided on the circumference of the positioning cylinder, and the positioning ear plate is connected to a plurality of support frames for supporting the positioning cylinder. A horizontal sensor is fixedly installed on the positioning ear plate. Two laser emitters and four distance sensors I are provided on the inner circumferential wall of the positioning cylinder. The laser lines emitted by the two laser emitters intersect vertically, and the four distance sensors are evenly distributed along the circumferential direction of the positioning cylinder;

[0006] S2. Exploration of rock formation properties: Use advance drilling combined with geophysical methods to determine the bedrock properties at the pile end, including whether there are caves, the location of the caves, and the thickness of the roof;

[0007] S3. Lowering the outer casing: Lay a steel plate near the pile foundation, position the rotary drilling rig on the steel plate, and connect the pipe swing device of the rotary drilling rig to drive the flower tube to lower the outer casing. During the lowering process, the center of the outer casing is aligned with the center of the pile foundation through the pile foundation positioning tooling;

[0008] S4. Drilling: Use a rotary drilling rig to drill holes. During the drilling process, the drill bit center of the rotary drilling rig is aligned with the pile foundation center through the pile foundation positioning tooling;

[0009] S5. Lowering the inner casing: lower the inner casing into the pile hole. During the lowering process, the center of the inner casing is aligned with the center of the pile foundation by using the pile foundation positioning tooling;

[0010] S6. Hole cleaning: remove the sediment at the bottom of the pile and detect the thickness of the sediment at the bottom of the pile;

[0011] S7, pouring concrete: making a steel cage on site and lowering it, and then pouring concrete;

[0012] S8, casing extraction: after the pile is formed, first extract the inner casing, then the outer casing;

[0013] S9. Inspection of pile foundation and pile quality.

[0014] The working principle and beneficial effects of this solution are:

[0015] (1) In this solution, the intersection of the laser lines emitted by the two laser transmitters in the pile foundation positioning tool is located directly above the center point of the pile foundation, thereby displaying the center point of the pile foundation so that construction personnel can quickly determine the center of the pile foundation, thereby quickly determining the centering reference in the subsequent casing lowering, drilling, and steel cage lowering processes, thereby improving construction efficiency.

[0016] (2) In this scheme, when the outer casing, the drill bit of the rotary drilling rig, and the inner casing pass through the positioning tube of the pile foundation positioning tooling, the four distance sensors I on the positioning tube detect the distances between four points on the outer wall of the object in the positioning tube and the corresponding distance sensors I, which are recorded as D1, D2, D3, and D4 respectively. By comparing the sizes of D1, D2, D3, and D4, it is possible to quickly determine whether the center of the object in the positioning tube is aligned with the center of the positioning tube, thereby quickly determining whether the center of the object in the positioning tube is aligned with the center of the pile foundation, and timely adjust the position of the object in the positioning tube to achieve alignment.

[0017] (3) The support frame of the pile foundation positioning tooling is equivalent to the guard pile, and the support frame is connected to the positioning ear plate, which is equivalent to connecting the scattered guard piles. In this way, during the positioning process, the forces acting on the support frame can be transmitted to each other, and the pile foundation positioning tooling has good integrity. Compared with the scattered guard pile design, this solution effectively reduces the impact of mechanical equipment operating load, large vibration of drilling operations, and foundation settlement on pile foundation positioning, thereby improving the accuracy of pile foundation positioning.

[0018] (4) In this solution, a horizontal sensor is used to detect the horizontality of the positioning tooling in real time. Once the support frame shifts and the support becomes unstable, the positioning ear plate tilts, which can be discovered in time by the horizontal sensor, so that the position of the pile foundation positioning tooling can be adjusted in time to ensure that the intersection of the two laser lines is located directly above the center point of the pile foundation, thereby ensuring the accuracy of pile foundation positioning and effectively avoiding the occurrence of offset holes and offset positions.

[0019] (5) In this scheme, the outer casing can support the hole mouth and prevent the hole mouth from collapsing, while the inner casing can prevent the pile hole wall from being affected by the process of lowering the steel cage and detecting the sediment at the bottom of the pile, thereby avoiding the collapse phenomenon.

[0020] Optionally, in step S6, a sediment detection tool is used to detect the thickness of the pile bottom sediment, and the sediment detection tool includes a detection rod, the detection rod is axially slidably connected with a casing, the bottom end of the casing is provided with a detection cake, and the bottom end of the detection rod is provided with an anti-slip part for preventing the casing from slipping out of the bottom end of the detection rod; a detection cavity is provided on the inner circumferential wall of the casing, a distance sensor II is provided in the detection cavity, and a detection part opposite to the distance sensor II is provided on the detection rod.

[0021] In this solution, the anti-dropout piece at the bottom of the probe rod is inserted into the pile bottom sediment and contacts the bottom wall of the pile hole. The horizontal area of ​​the probe cake is large and is trapped on the surface of the pile bottom sediment. In this way, the probe rod and the casing move relative to each other axially, and the detection piece on the probe rod moves accordingly. During this process, the distance sensor II detects the axial movement distance of the probe rod in real time and feeds back to the ground. The sum of the axial movement distance of the probe rod and the axial length of the anti-dropout piece is the thickness of the pile bottom sediment. In this solution, there is no need to read the measuring rope data, thereby reducing human errors and improving the accuracy of the test results; moreover, in this solution, only one sediment detection tooling needs to be lowered, which is simpler to operate and easier for testers to use.

[0022] Optionally, in step S4, if a cave is encountered during the drilling process, the cave is filled.

[0023] In this scheme, a mixture of stone flakes and clay is used as a filler to fill the cave, and the filler is impacted to make the filler fully dense, thereby completing the treatment of the cave.

[0024] Optionally, in step S5, the outer diameter of the inner casing is equal to the diameter of the pile hole.

[0025] In this solution, the outer diameter of the inner casing is equal to the diameter of the pile hole, so that the outer peripheral wall of the inner casing fits with the wall of the pile hole, thereby protecting the wall of the pile hole.

[0026] Optionally, in step S1, a controller and an alarm are fixedly installed on the positioning ear plate of the pile foundation positioning tooling, the alarm and the level sensor are electrically connected to the controller, the level sensor transmits the detected signal to the controller, and the controller controls the alarm to work according to the received signal.

[0027] In this solution, when the horizontal sensor detects that the positioning ear plate is tilted to a certain degree, the controller controls the alarm to sound an alarm (the alarm is a beep and / or light), alerting the construction personnel to deal with the problem of tooling tilt in a timely manner, avoiding the construction personnel from always paying attention to the horizontal information detected by the horizontal sensor (the horizontal information detected by the horizontal sensor is displayed through the display screen), and better ensuring that the construction personnel take timely measures.

[0028] Optionally, more than three groups of limit assemblies are provided in the circumferential direction of the positioning cylinder, each group of limit assemblies includes a radial threaded tube and an adjusting screw, the radial threaded tube penetrates the circumferential wall of the positioning cylinder, and the radial threaded tube is arranged along the radial direction of the positioning cylinder, and the adjusting screw is threadedly connected to the radial threaded tube.

[0029] In this solution, the positioning tube is located outside the outer casing, and the adjusting screw is rotated so that one end of each adjusting screw located in the positioning tube abuts against the outer peripheral wall of the outer casing, thereby using the outer casing to limit the positioning tube to prevent the positioning tube from moving radially during the positioning process.

[0030] Optionally, the detection member is an annular plate.

[0031] In this solution, the sleeve may rotate circumferentially relative to the detection rod. In this way, when the detection member is an annular plate, it can be ensured that the distance sensor II detects the axial movement distance of the detection rod.

[0032] Optionally, the anti-dropping member is a pointed cone, with the tip of the pointed cone facing the side away from the sleeve.

[0033] In this solution, the anti-dropping member has a pointed head, which makes it easier to insert into the sediment at the bottom of the pile.

[0034] Optionally, a locking assembly is provided in the detection cavity, and the locking assembly includes an electromagnet, a magnet arranged opposite to the electromagnet, a connecting rod fixedly connected to the magnet, and a clamping plate fixedly connected to the connecting rod. The electromagnet is fixedly installed in the detection cavity, a waterproof cover is provided outside the electromagnet, and the magnet is horizontally slidably connected in the detection cavity. When the electromagnet is energized, a magnetic repulsion force is applied to the magnet, and the clamping plate clamps the detection rod.

[0035] In this solution, after the anti-slipping piece is inserted into the pile bottom sediment and contacts the bottom wall of the pile hole, the electromagnet is energized to apply magnetic repulsion to the magnet, and the magnet drives the connecting rod and the clamping piece to apply radial clamping force to the detection rod, thereby locking the casing on the detection rod. In this way, after removing the sediment detection tooling upward, the distance between the detection cake and the bottom end of the anti-slipping piece can be manually measured to obtain the thickness of the pile bottom sediment. In this way, it can be mutually verified with the pile bottom sediment thickness previously measured by the distance sensor II, and the pile bottom sediment thickness can be measured when the distance sensor II is damaged, which is practical.

[0036] Optionally, the detection rod includes a plurality of segments, and two adjacent segments are connected by threads.

[0037] In this solution, the detection rod is spliced ​​together in several stages, so that the axial length of the detection rod is greater than the depth of the pile hole, which allows the detection personnel to apply force to the detection rod, thereby ensuring that the anti-slip component is inserted into the pile bottom sediment and contacts the bottom wall of the pile hole, thereby ensuring the accuracy of the pile bottom sediment detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic flow diagram of a pile foundation construction method suitable for karst areas in Example 1 of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of the pile foundation positioning tool in Example 1 of the present invention;

[0040] Figure 3 A top view of the pile foundation positioning tool in Example 1 of the present invention;

[0041] Figure 4 It is a radial cross-sectional view of the positioning cylinder in Example 1 of the present invention;

[0042] Figure 5 This is a structural schematic diagram of the use of sediment detection tooling to detect the thickness of sediment at the bottom of a pile in Example 1 of the present invention;

[0043] Figure 6 It is a longitudinal cross-sectional view of the sediment detection tooling in Example 1 of the present invention;

[0044] Figure 7 This is a schematic diagram of the structure of the anti-dropping member when inserted into the pile bottom sediment in Example 1 of the present invention;

[0045] Figure 8 A top view of the inner casing when the pile foundation positioning tool is used to center the inner casing in Example 1 of the present invention;

[0046] Fig. 9 This is a schematic diagram of the structure of the limit assembly in Example 2 of the present invention;

[0047] Fig.10It is a longitudinal cross-sectional view of the sediment detection tooling in Example 3 of the present invention;

[0048] Fig.11 for Fig.10 Sectional view in the AA direction;

[0049] Fig.12 Schematic diagram of the structure of the detection rod in Example 4 of the present invention;

[0050] Fig.13 It is a schematic diagram of the structure when the primary segment and the secondary segment are separated in Example 4 of the present invention. DETAILED DESCRIPTION

[0051] The following is further described in detail through specific implementation methods:

[0052] The marks in the drawings of the specification include: positioning tube 1, upper extension 110, positioning ear plate 2, support frame 3, lateral support rod 310, outer sleeve 301, inner slide rod 302, longitudinal support rod 320, mounting plate II4, mounting plate I5, level sensor 6, controller 7, alarm 8, laser transmitter 9, distance sensor I10, detection rod 11, first section 1110, secondary section 1120, external threaded section 1130, sleeve 12, detection cake 13, anti-slip part 14, detection cavity 15, distance sensor II 16, detection part 17, display 18, lifting rope 19, limit assembly 20, radial threaded tube 2001, adjusting screw 2002, electromagnet 21, magnet 22, connecting rod 23, tightening plate 24, waterproof cover 25, rubber sheet 26, outer casing 27, inner casing 28

[0053] Example 1

[0054] This embodiment provides a pile foundation construction method suitable for karst areas, and its process is as follows: Figure 1 As shown, the specific steps include:

[0055] S1. Level the ground and measure and lay out: After leveling the ground, calculate the coordinates of the center point of the pile foundation according to the coordinates provided in the design drawings. According to the coordinates of the control piles at the construction site, use a total station to accurately lay out the pile position, and use the pile foundation positioning tooling to display the center point of the pile foundation.

[0056] Among them, the structure of the pile foundation positioning tooling is as follows Figure 2 and Figure 3As shown, it includes a positioning cylinder 1, and a positioning ear plate 2 is integrally formed on the outer peripheral wall of the positioning cylinder 1. The positioning ear plate 2 is detachably connected to a plurality of support frames 3 for supporting the positioning cylinder 1. Specifically, the support frame 3 includes a transverse support rod 310 and a longitudinal support rod 320. The transverse support rod 310 is a telescopic rod, including an outer sleeve 301 and an inner slide rod 302. The inner slide rod 302 is axially slidably connected in the outer sleeve 301. To prevent the inner slide rod 302 from circumferentially rotating relative to the outer sleeve 301, in this embodiment, the radial cross-sections of the outer sleeve 301 and the inner slide rod 302 are rectangular; a mounting plate Ⅱ4 is welded to one end of the outer sleeve 301 away from the inner slide rod 302, and the end of the inner slide rod 302 away from the outer sleeve 301 is welded to the top of the longitudinal support rod 320, and the bottom end of the longitudinal support rod 320 has a pointed head. A mounting plate Ⅰ5 is welded on the positioning ear plate 2, and both the mounting plate Ⅰ5 and the mounting plate Ⅱ4 are provided with mounting holes for bolts to pass through; in this way, the bolts pass through the mounting holes on the mounting plate Ⅰ5 and the mounting plate Ⅱ4 and cooperate with the screws to achieve a detachable connection between the support frame 3 and the positioning ear plate 2. In this embodiment, the number of support frames 3 is three, and the angle between the support frame 3 and the adjacent support frame 3 is 90°. A horizontal sensor 6, a controller 7 and an alarm 8 are fixedly installed on the positioning ear plate 2. The horizontal sensor 6 and the alarm 8 are electrically connected to the controller 7. The horizontal sensor 6 transmits the detected signal to the controller 7, and the controller 7 controls the alarm 8 to work according to the received signal. In this embodiment, the controller 7 is a PLC, the alarm 8 is an audible and visual alarm, and the horizontal sensor 6 is a conventional dual-axis inclination sensor. Two upper extensions 110 are integrally formed at the top of the positioning cylinder 1, and laser emitters 9 are fixedly installed on the upper extensions 110. The laser lines emitted by the two laser emitters 9 intersect vertically; combined with Figure 4 As shown, four distance sensors Ⅰ10 are fixedly mounted on the inner circumferential wall of the positioning cylinder 1 , and the four distance sensors Ⅰ10 are evenly distributed along the circumferential direction of the positioning cylinder 1 .

[0057] The installation process of the pile foundation positioning tool is as follows: after the pile position is accurately laid out using the total station, a round rod (such as a steel bar) is vertically inserted at the center point of the pile foundation. Then, the positioning cylinder 1 is placed outside the round rod, and the position of the positioning cylinder 1 is adjusted so that the round rod is located at the intersection of two laser lines (the laser lines are emitted by the laser emitter 9), and the intersection of the two laser lines is located directly above the center point of the pile foundation. Then, downward pressure is applied to the three support frames 3 at the same time, so that the bottom end of the longitudinal support rod 320 is inserted into the ground (the tip of the longitudinal support rod 320 is conducive to breaking the soil layer) to complete the installation of the positioning tool. During the insertion of the longitudinal support rod 320 into the ground, the horizontal sensor 6 detects the horizontality of the positioning ear plate 2 in real time. When the horizontal sensor 6 detects that the positioning ear plate 2 is tilted, the controller 7 controls the alarm to emit sound and light to prompt the construction personnel to adjust the pressure applied to the support frame 3 in time, thereby ensuring that the positioning ear plate 2 remains horizontal during the downward movement, and then ensuring that the intersection of the two laser lines is located directly above the center point of the pile foundation.

[0058] In addition, before the longitudinal support rod 320 is inserted into the ground, the construction personnel can select the insertion location of the longitudinal support rod 320 according to the actual situation of the construction site to prevent the problem that the longitudinal support rod 320 cannot be inserted into the ground due to the solid stratum. Specifically, the insertion location of the longitudinal support rod 320 can be changed by pulling out the inner sliding rod 302 horizontally.

[0059] Since the three support frames 3 are all connected to the positioning ear plate 2, the forces on the support frames 3 can be transmitted to each other, and the integrity and stability of the positioning tool are good. In this way, when the local soil layer is loose, the force of the support frame 3 corresponding to the loose soil layer changes, while the force of the support frame 3 outside the range of the loose soil layer is stable. The interaction between the three support frames 3 can effectively prevent the displacement of the positioning tool, thereby ensuring that the intersection of the two laser lines is located directly above the center point of the pile foundation, thereby ensuring the accuracy of the pile foundation positioning. When the soil layers near the three support frames 3 are all loose, the force conditions of the three support frames 3 are all changed, and the positioning tool is tilted and no longer horizontal. At this time, after the horizontal sensor 6 detects that the positioning tool is tilted to a certain angle, the controller 7 controls the alarm 8 to emit sound and light, warning the construction personnel to correct the positioning tool in time (push the support frame 3 to the correct position and then compact the soil layer), so that the intersection of the two laser lines is located directly above the center point of the pile foundation again, thereby ensuring the accuracy of the pile foundation center positioning, avoiding biased holes and offsets, and ensuring the quality of the hole.

[0060] S2. Exploration of rock formation properties: Use advance drilling combined with geophysical methods to determine the bedrock properties at the pile end, including whether there are caves, the location of the caves, and the thickness of the top plate. Geophysical methods include sonic detection, geological radar detection, etc.

[0061] S3. Lowering the outer casing: lay a steel plate near the pile foundation, position the rotary drilling rig on the steel plate, and use the rotary drilling rig's pipe swing device to drive the flower tube to lower the outer casing. During the lowering process, the center of the outer casing is aligned with the center of the pile foundation through the pile foundation positioning tooling.

[0062] S4. Drilling: A rotary drilling rig is used to drill holes. During the drilling process, the drill bit center of the rotary drilling rig is aligned with the center of the pile foundation through the pile foundation positioning tooling. In addition, if a cave is encountered, a mixture of stone flakes and clay is used as a filler to fill the cave, and the filler is impacted to make it fully dense, and then the hole is drilled to the preset depth.

[0063] S5. Lowering the inner casing: Lower the inner casing in the pile hole. During the lowering process, the center of the inner casing is aligned with the center of the pile foundation through the pile foundation positioning tool; the outer diameter of the inner casing is equal to the diameter of the pile hole. In addition, the lowering of the inner casing can be carried out by a pipe rolling machine or a vibrating hammer.

[0064] S6. Hole cleaning: remove the sediment at the bottom of the pile and detect the thickness of the sediment at the bottom of the pile. The thickness of the sediment at the bottom of the pile is detected by using sediment detection tooling, such as Figure 5 and Figure 6 As shown, the sediment detection tooling includes a detection rod 11, including a detection rod 11, the detection rod 11 is axially slidably connected with a sleeve 12, the bottom end of the sleeve 12 is integrally formed with a detection cake 13, and the bottom end of the detection rod 11 is welded with an anti-slip member 14 for preventing the sleeve 12 from sliding out of the bottom end of the detection rod 11, and the anti-slip member 14 is a pointed cone, and the tip of the pointed cone faces downward. A detection cavity 15 is provided on the inner peripheral wall of the sleeve 12, and a distance sensor II 16 is provided in the detection cavity 15. A detection member 17 opposite to the distance sensor II 16 is welded on the detection rod 11, and the detection member 17 is a ring plate. In this embodiment, the distance sensor II 16 is an underwater distance measuring sensor, and the model can be selected as an M33 patch type. The distance sensor II 16 is electrically connected to a display 18 for displaying the distance value detected by the distance sensor II 16 through a wire, and the display 18 is located on the ground for the detection personnel to read the displayed data.

[0065] When the sediment detection tool is used, the top of the detection rod 11 is bound by a lifting rope 19, and the detection personnel put the detection rod 11 into the pile hole, and lower the detection tool by lowering the lifting rope 19. When the detection tool contacts the sediment at the bottom of the pile, since the bottom end of the anti-dropping member 14 has a pointed head and the horizontal area of ​​the detection cake 13 is large, the anti-dropping member 14 is inserted into the sediment at the bottom of the pile under the action of gravity, and the detection cake 13 is blocked by the sediment at the bottom of the pile and is trapped on the surface of the sediment at the bottom of the pile, such as Figure 7 As shown. In this process, the detection rod 11 and the casing 12 move relative to each other in the axial direction, the casing 12 is stationary, and the detection rod 11 moves downward, and the detection member 17 on the detection rod 11 moves downward accordingly, and the distance sensor II 16 detects the distance between it and the detection member 17 in real time, and transmits the distance information to the display 18 on the ground. After the bottom end of the anti-slip member 14 contacts the bottom wall of the pile hole, the distance data on the display 18 no longer changes. The difference between the distance data and the initial distance data (when the bottom end of the casing 12 and the anti-slip member 14 are against each other, the distance measured by the distance sensor II 16 is the initial distance) is the axial movement distance of the detection rod 11, which is recorded as d1; the axial length (height) of the anti-slip member 14 is d2, and the sum of d1 and d2 is the thickness of the pile bottom sediment. In this way, the method for determining the thickness of the pile bottom sediment in this embodiment is simple and efficient, only needs to be lowered once, and there is no need for the detection personnel to read the measurement rope data, which reduces human errors and improves the accuracy of the detection results.

[0066] S7. Pouring concrete: Make the steel cage on site and lower it, then pour the concrete.

[0067] S8, casing extraction: after the cast-in-place pile is formed, first extract the inner casing 28 and then the outer casing 27.

[0068] S9. Inspection of pile foundation and pile quality.

[0069] In step S3, step S4 and step S5, the process of realizing centering by the pile foundation positioning tool is as follows: when the outer casing 27 / drill bit / inner casing 28 passes through the positioning tube 1, four distance sensors Ⅰ10 detect the distances between four points on the outer peripheral wall of the outer casing 27 / drill bit / inner casing 28 and the corresponding distance sensors Ⅰ10, which are respectively recorded as D1, D2, D3, and D4. Figure 8 As shown, by comparing the sizes of D1, D2, D3, and D4, it is possible to quickly determine whether the center of the outer casing 27 / drill bit / inner casing 28 is aligned with the center of the positioning tube 1, thereby quickly determining whether the center of the outer casing 27 / drill bit / inner casing 28 is aligned with the center of the pile foundation, and timely adjust the position of the outer casing 27 / drill bit / inner casing 28 to achieve alignment. Specifically, if D1=D2=D3=D4, it means that the center of the outer casing 27 / drill bit / inner casing 28 is aligned with the center of the pile foundation; if D1, D2, D3, and D4 are all within (R 差 Within ±7)mm (R 差 is the difference between the inner radius of the positioning tube 1 and the outer radius of the outer casing 27 / drill bit / inner casing 28), it means that although the center of the outer casing 27 / drill bit / inner casing 28 is not aligned with the center of the pile foundation, it is within the allowable error range; if any of D1, D2, D3, and D4 does not fall within (R 差 ±7)mm, it means that the center of the outer casing 27 / drill bit / inner casing 28 is not aligned with the center of the pile foundation, and the position of the outer casing 27 / drill bit / inner casing 28 needs to be adjusted until D1, D2, D3, and D4 are all within (R 差 Within ±7)mm.

[0070] In addition, in step S6 and step S7, since the inner casing 28 protects the pile hole wall, the steel cage and the sediment detection tooling will not hit the pile hole wall during the lowering process, thereby avoiding hole collapse.

[0071] Example 2

[0072] The difference between this embodiment and the first embodiment is that: Fig. 9 As shown, more than three groups of limit assemblies 20 are provided in the circumferential direction of the positioning cylinder 1. The limit assemblies 20 are located below the positioning ear plate 2. Each group of limit assemblies 20 includes a radial threaded tube 2001 and an adjusting screw 2002. The radial threaded tube 2001 penetrates the circumferential wall of the positioning cylinder 1, and the radial threaded tube 2001 is arranged along the radial direction of the positioning cylinder 1. The adjusting screw 2002 is threadedly connected to the radial threaded tube 2001.

[0073] In this embodiment, the lowering depth of the outer casing 27 is relatively deep and is not easy to move. In this way, the positioning tube 1 is located outside the outer casing 27, and the construction personnel rotate the adjusting screw 2002 so that the end of each adjusting screw 2002 located in the positioning tube 1 abuts against the outer peripheral wall of the outer casing 27, thereby using the outer casing 27 to limit the positioning tube 1, preventing the positioning tube 1 from moving radially during the positioning process, further improving the positioning accuracy of the positioning tool, and reducing the construction personnel's correction work on the positioning tool.

[0074] Example 3

[0075] The difference between this embodiment and the first embodiment is that: Fig.10 and Fig.11 As shown, a locking assembly is provided in the detection chamber 15, and the number of the locking assembly is two groups, and the two groups of locking assemblies are symmetrically distributed on both sides of the detection rod 11; the locking assembly includes an electromagnet 21, a magnet 22 arranged opposite to the electromagnet 21, a connecting rod 23 fixedly connected to the magnet 22, and a fastening piece 24 fixedly connected to the connecting rod 23, the electromagnet 21 is fixedly installed in the detection chamber 15, a waterproof cover 25 is provided outside the electromagnet 21, and the magnet 22 is horizontally slidably connected in the detection chamber 15. After the electromagnet 21 is energized, a magnetic repulsive force is applied to the magnet 22, so that the fastening piece 24 is pressed against the detection rod 11. In addition, the switch for controlling the on and off of the electromagnet 21 and the power supply for the electromagnet 21 are located on the ground, so that the detection personnel can control the on and off of the electromagnet 21. The fastening piece 24 is arc-shaped, and the fastening piece 24 can fit with the outer peripheral wall of the detection rod 11, and a rubber piece 26 is bonded to the side of the fastening piece 24 facing the detection rod 11. The detection rod 11 is provided with scale lines, and the zero mark of the scale lines coincides with the bottom end of the anti-dropping member 14 .

[0076] In this scheme, the inspector lowers the detection tooling into the pile hole through the hanging rope 19, and obtains d1 according to the detection process recorded in Example 1. The sum of d1 and d2 is the thickness of the pile bottom sediment. When the bottom end of the anti-slip member 14 contacts the bottom wall of the pile hole, the inspector closes the switch that controls the on and off of the electromagnet 21, and the electromagnet 21 is energized. The electromagnet 21 exerts a magnetic repulsive force on the magnet 22, and the magnet 22 slides toward the detection rod 11, and drives the tightening plate 24 to move toward the detection rod 11 through the connecting rod 23. The tightening plate 24 and the detection rod 11 are pressed tightly, so that the two tightening plates 24 clamp the detection rod 11 and lock the sleeve 12 on the detection rod 11. Therefore, in the process of the inspector lifting and recovering the detection tooling through the hanging rope 19, the sleeve 12 and the detection rod 11 are relatively stationary; after the detection tooling is recovered, the inspector can read the scale line value on the detection rod 11 corresponding to the bottom surface of the detection cake 13, which is the thickness of the pile bottom sediment.

[0077] In this way, the pile bottom sediment thickness read by the scale lines on the detection rod 11 and the pile bottom sediment thickness measured by the distance sensor II 16 can be mutually verified, thereby further improving the accuracy of the detection result. Moreover, in this embodiment, when the distance sensor II 16 fails, the pile bottom sediment thickness can be obtained through the scale lines.

[0078] In this embodiment, after the electromagnet 21 is powered off, the magnetic repulsion force of the electromagnet 21 on the magnet 22 disappears, and the magnet 22 has a magnetic attraction force on the electromagnet 21, so that the magnet 22 drives the connecting rod 23 and the locking plate 24 to move and reset, thereby releasing the lock of the sleeve 12 without affecting the axial sliding between the sleeve 12 and the detection rod 11.

[0079] Example 4

[0080] The difference between this embodiment and embodiment 1, embodiment 2 or embodiment 3 is that: Fig.12 and Fig.13 As shown, the detection rod 11 includes a plurality of segments, and two adjacent segments are connected by threads. Specifically, for the convenience of description, the segment with the anti-dropping member 14 is called the first segment 1110, and the remaining segments are called the secondary segments 1120. The first segment 1110 is a solid round steel pipe, and the secondary segment 1120 is a hollow round steel pipe. The top of the first segment 1110 and the top of the secondary segment 1120 are both provided with an external thread segment 1130, and the bottom of the secondary segment 1120 is provided with an internal thread segment threadedly matched with the external thread segment 1130.

[0081] In this embodiment, according to the depth of the pile hole, a suitable number of sub-segments 1120 are selected for splicing, so that the axial length of the spliced ​​detection rod 11 is greater than the depth of the pile hole. During the splicing, the top of the primary segment 1120 is bound by a suspension rope 19 and suspended by a crane; then, the detection personnel thread the second sub-segment 1120 onto the suspended sub-segment 1120, and so on, until all the selected sub-segments 1120 are spliced, and the suspension height is adjusted by the crane during the process to complete the splicing of the sub-segments 1120; then, the first segment 1110 is threaded onto the corresponding sub-segment 1120, thereby completing the splicing of the detection rod 11; finally, the detection rod 11 is lowered into the pile hole as a whole by a crane to detect the thickness of the pile bottom sediment. Since the axial length of the detection rod 11 is greater than the depth of the pile hole, when the anti-slip component 14 is inserted into the sediment at the bottom of the pile, the inspection personnel can apply downward pressure to the detection rod 11 to ensure that the bottom end of the anti-slip component 14 contacts the bottom wall of the pile hole, thereby preventing the gravel in the sediment at the bottom of the pile from hindering the anti-slip component 14 from penetrating into the sediment at the bottom of the pile; moreover, the inspection personnel can also rotate the detection rod 11 so that the bottom end of the anti-slip component 14 contacts the bottom wall of the pile hole after being screwed in.

[0082] After the detection is completed, the detection rod 11 is lifted up by a crane, and the detection personnel separate the first segment 1110 from the secondary segment 1120, and then separate the adjacent secondary segments 1120, and the detection rod 11 can be disassembled and stored.

[0083] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the present invention. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. A pile foundation construction method suitable for karst areas, characterized in that: The following steps are involved: S1. Level the ground and measure and lay out: After leveling the ground, calculate the coordinates of the center point of the pile foundation according to the coordinates provided in the design drawings. According to the coordinates of the control piles at the construction site, use a total station to accurately lay out the pile position, and use a pile foundation positioning tool to display the center point of the pile foundation; the pile foundation positioning tool includes a positioning cylinder, a positioning ear plate is provided on the circumference of the positioning cylinder, and the positioning ear plate is connected to a plurality of support frames for supporting the positioning cylinder. A horizontal sensor is fixedly installed on the positioning ear plate. Two laser emitters and four distance sensors I are provided on the inner circumferential wall of the positioning cylinder. The laser lines emitted by the two laser emitters intersect vertically, and the four distance sensors are evenly distributed along the circumferential direction of the positioning cylinder; S2. Exploration of rock formation properties: Use advance drilling combined with geophysical methods to determine the bedrock properties at the pile end, including whether there are caves, the location of the caves, and the thickness of the roof; S3. Lowering the outer casing: Lay a steel plate near the pile foundation, position the rotary drilling rig on the steel plate, and connect the pipe swing device of the rotary drilling rig to drive the flower tube to lower the outer casing. During the lowering process, the center of the outer casing is aligned with the center of the pile foundation through the pile foundation positioning tooling; S4. Drilling: Use a rotary drilling rig to drill holes. During the drilling process, the drill bit center of the rotary drilling rig is aligned with the pile foundation center through the pile foundation positioning tooling; S5. Lowering the inner casing: lower the inner casing into the pile hole. During the lowering process, the center of the inner casing is aligned with the center of the pile foundation by using the pile foundation positioning tooling; S6. Hole cleaning: remove the sediment at the bottom of the pile and detect the thickness of the sediment at the bottom of the pile; S7, pouring concrete: making a steel cage on site and lowering it, and then pouring concrete; S8, casing extraction: after the pile is formed, first extract the inner casing, then the outer casing; S9. Inspection of pile foundation and pile quality.

2. The pile foundation construction method suitable for karst areas according to claim 1, characterized in that: In step S6, a sediment detection tool is used to detect the thickness of the pile bottom sediment, and the sediment detection tool includes a detection rod, and the detection rod is axially slidably connected with a sleeve, the bottom end of the sleeve is provided with a detection cake, and the bottom end of the detection rod is provided with an anti-slip part for preventing the sleeve from sliding out of the bottom end of the detection rod; a detection cavity is provided on the inner circumferential wall of the sleeve, and a distance sensor II is provided in the detection cavity, and a detection part opposite to the distance sensor II is provided on the detection rod.

3. The pile foundation construction method suitable for karst areas according to claim 1, characterized in that: In step S4, if a cave is encountered during the drilling process, the cave is filled.

4. The pile foundation construction method suitable for karst areas according to claim 1, characterized in that: In step S5, the outer diameter of the inner casing is equal to the diameter of the pile hole.

5. The pile foundation construction method suitable for karst areas according to claim 1, characterized in that: In step S1, a controller and an alarm are fixedly installed on the positioning ear plate of the pile foundation positioning tooling, and the alarm and the level sensor are electrically connected to the controller. The level sensor transmits the detected signal to the controller, and the controller controls the alarm to work according to the received signal.

6. The pile foundation construction method suitable for karst areas according to claim 5, characterized in that: The positioning cylinder is provided with more than three groups of limiting components in the circumferential direction, each group of limiting components includes a radial threaded tube and an adjusting screw, the radial threaded tube penetrates the circumferential wall of the positioning cylinder, and the radial threaded tube is arranged along the radial direction of the positioning cylinder, and the adjusting screw is threadedly connected with the radial threaded tube.

7. The pile foundation construction method suitable for karst areas according to claim 2, characterized in that: The detection member is an annular plate.

8. The pile foundation construction method suitable for karst areas according to claim 7, characterized in that: The anti-dropping piece is a pointed cone, and the tip of the pointed cone faces the side away from the sleeve.

9. The pile foundation construction method suitable for karst areas according to claim 8, characterized in that: A locking assembly is provided in the detection cavity, which includes an electromagnet, a magnet arranged opposite to the electromagnet, a connecting rod fixedly connected to the magnet, and a clamping plate fixedly connected to the connecting rod. The electromagnet is fixedly installed in the detection cavity, a waterproof cover is provided outside the electromagnet, the magnet is horizontally slidably connected to the detection cavity, and when the electromagnet is energized, a magnetic repulsive force is applied to the magnet, and the clamping plate clamps the detection rod.

10. The pile foundation construction method suitable for karst areas according to claim 8 or 9, characterized in that: The detection rod comprises a plurality of segments, and two adjacent segments are connected by threads.

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