A load box for self-balancing static load test and test method

Abstract

The present invention relates to a load box for self-balancing static load test and a test method, belonging to the technical field of building construction. The present invention includes a top plate, a hydraulic cylinder and a bottom plate connected in sequence from top to bottom, and also includes a distance measuring mechanism and a displacement detector, wherein the distance measuring mechanism is vertically installed between the top plate and the bottom plate and is used to detect the distance change between the top plate and the bottom plate, and the displacement detector is installed on a ground reference frame and is used to detect the distance change between the bottom plate and the reference frame; the present invention detects the displacement of the top plate and the bottom plate in the load box by arranging a distance measuring mechanism in the load box, and then subtracts the displacement of the bottom plate to obtain the displacement of the top plate, thereby completing the static load test, solving the problem of low efficiency and large measurement error when building a displacement observation system in the existing self-balancing static load test process.

Description

Technical Field

[0001] The invention belongs to the technical field of building construction, and in particular relates to a load box for self-balancing static load test and a test method. Background Art

[0002] Self-balancing means using the deadweight and friction of the pile to provide the pile-pressing force, so there is no need for additional loading. Therefore, the buried position (buried depth) of the load box is based on a principle: when the load box is working, the force on the upper part (soil friction, deadweight, etc.) can meet the maximum load on the lower part. The self-balancing method is different from the traditional loading method and anchor pile method. During the construction process, the load box that is shaped and manufactured according to the pile bearing capacity parameter requirements is placed at the bottom of the pile body, and the pressure oil pipe and displacement measurement device are connected to the top of the pile. After the concrete is cured to the standard age, the top high-pressure oil pump is used to pressurize the bottom load box to obtain the pile end bearing capacity and the total friction resistance of the pile side.

[0003] The existing self-balancing static load test load box displacement observation method is usually a method of pre-embedded displacement tube or displacement wire. For super-long foundation piles, the depth of the load box is large, and the pre-embedded displacement tube can reach tens of meters in length. In this way, the stiffness of the entire displacement tube is very low, so the displacement tube cannot stand upright in the vertical pile body protection tube, but is bent and attached to the inner wall of the protection tube. In this way, when the displacement rod is connected to one end of the load box and displaces, the displacement rod itself will produce length deformation, and the displacement of the other end extending to the ground is very small or even zero. Therefore, the specification of "Self-balancing Method for Static Load Test of Foundation Pile" (JT / T 738-2009) requires that when the pile length is greater than 40m, the displacement wire should be used instead of the displacement tube. However, when the displacement wire is pre-embedded in super-long piles, it is very difficult to implement, because the displacement wire is pre-embedded along the main reinforcement of the pile foundation, and the steel cage is placed in the drilled hole section by section from bottom to top, and the steel cage of the super-long pile has several to more than ten sections. It is very troublesome to put a displacement wire of dozens of meters in length into multiple protection tubes and put it into the borehole together with the steel cage. When the steel cage is lowered for the test pile, it will take a long time because of the pre-embedded displacement wire, which will seriously affect the quality of the pile drilling and further affect the quality of the pile concrete. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a load box and a test method for a self-balancing static load test, which solves the problems of low efficiency and large measurement error when building a displacement observation system during the existing self-balancing static load test.

[0005] The object of the present invention can be achieved by the following technical scheme: a load box for self-balancing static load test, comprising a top plate, a hydraulic cylinder and a bottom plate connected in sequence from top to bottom, and also comprising a distance measuring mechanism and a displacement detector, wherein the distance measuring mechanism is vertically installed between the top plate and the bottom plate and is used to detect the distance change between the top plate and the bottom plate, and the displacement detector is installed on a ground reference frame and is used to detect the distance change between the bottom plate and the reference frame;

[0006] The displacement detector includes an optical fiber, a laser transmitter, a receiver, a fixing seat and a catheter. The catheter is vertically installed on the bottom surface of the reference frame. The fixing seat is located in the catheter and slidably fits with the catheter. The receiver is installed on the top surface of the base plate. One end of the optical fiber is fixedly connected to the fixing seat, and the other end is fixedly connected to the receiver.

[0007] As a preferred technical solution of the present invention, the optical fiber is composed of an outer layer and a reflective layer, the outer layer wraps the reflective layer, and both the outer layer and the reflective layer are elastic layers.

[0008] As a preferred technical solution of the present invention, a guide hole is opened on the top plate, a guide tube is arranged in the guide hole, and the bottom end of the guide tube is located on the top surface of the bottom plate and is sleeved on the outside of the receiver.

[0009] As a preferred technical solution of the present invention, a clamp is provided on the top surface of the guide hole, and the clamp is used to clamp the optical fiber and keep the optical fiber vertical between the top and the bottom.

[0010] As a preferred technical solution of the present invention, the laser emitter emits femtosecond laser pulses.

[0011] As a preferred technical solution of the present invention, the displacement detector further comprises a spring, one end of which is fixedly connected to the inner top surface of the conduit, and the other end of which is fixedly connected to the fixing seat.

[0012] As a preferred technical solution of the present invention, the distance measuring mechanism includes a support tube, a sliding tube, a detection plate and a distance meter. The support tube is installed on the top surface of the bottom plate, the sliding tube is installed on the bottom surface of the top plate and is on the same axis as the support tube, the bottom end of the sliding tube is located inside the support tube and is slidably connected to the support tube, the detection plate is installed on the bottom surface of the sliding tube, the distance meter is installed on the bottom surface of the support tube, and the distance meter is used to measure the distance change of the detection plate.

[0013] As a preferred technical solution of the present invention, the rangefinder is a laser rangefinder or an ultrasonic rangefinder.

[0014] Based on the above-mentioned self-balancing static load test load box, the present invention also proposes an efficient self-balancing static load test method, comprising the following steps:

[0015] S1: Fix and weld the top plate and the steel cage of the upper pile, and weld the reinforcing steel bars between the top plate and the upper steel cage; fix and weld the bottom plate and the steel cage of the lower pile, and weld the reinforcing steel bars between the bottom plate and the lower steel cage;

[0016] S2: Place the top of the optical fiber above the top of the upper pile, and fix the bottom end to the receiver and keep the optical fiber vertical between the bottom plate and the top plate;

[0017] S3: lower the entire steel cage to the designated location;

[0018] S4: lowering the pouring pipe, passing through the center hole between the top plate and the bottom plate, down to the lower part of the steel cage, and pouring concrete to form a pile;

[0019] S5: Building a reference frame, and installing other components of the displacement detector on the reference frame;

[0020] S6: Fix the optical fiber to the fixing seat and keep the optical fiber in a straight state;

[0021] S7: Pressurize the hydraulic cylinder to move the top plate upward, drive the upper pile to move upward, and move the bottom plate downward, drive the lower pile section to move downward;

[0022] S8: the distance measuring mechanism detects the relative displacement between the top plate and the bottom plate, and the displacement detector measures the relative displacement of the bottom plate;

[0023] S9: The displacement of the bottom plate is measured by the displacement detector, and the displacement of the top plate is obtained by subtracting the measurement result of the displacement detector from the value detected by the distance measuring mechanism;

[0024] S10: After loading is completed, grouting is performed into the gap between the top plate and the bottom plate through two grouting pipes;

[0025] S11: Cement slurry that meets the design strength requirements and has good fluidity is injected into the space between the top plate and the bottom plate from the grouting pipe to play the role of filling, sealing and tightening the connection.

[0026] The beneficial effects of the present invention are as follows: when a static load test is performed, the displacement of the bottom plate is detected by a displacement detector, and the displacement of the top plate and the bottom plate in the load box is detected by arranging a distance measuring mechanism in the load box, and then the displacement of the bottom plate is subtracted to obtain the displacement of the top plate, so as to complete the static load test. In addition, the distance measuring mechanism arranged in the load box reduces the detection difficulty when performing the static load test, and at the same time improves the detection accuracy, thereby solving the problem of low efficiency and large measurement error when building a displacement observation system in the existing self-balancing static load test process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0028] Figure 1 It is a structural schematic diagram of the present invention;

[0029] Figure 2 It is a schematic diagram of the load box structure of the present invention;

[0030] Figure 3 This is a schematic diagram of the distance measuring mechanism structure of the present invention;

[0031] Figure 4 It is a schematic diagram of the structure of the displacement detector of the present invention;

[0032] Figure 5 This is a flow chart of the high-efficiency self-balancing static load test method of the present invention;

[0033] Main component symbols

[0034] In the figure: 11, top plate; 12, bottom plate; 13, hydraulic cylinder; 14, guide tube; 15, clamp; 2, distance measuring mechanism; 21, support tube; 22, sliding tube; 23, detection plate; 24, distance meter; 3, displacement detector; 31, optical fiber; 32, laser transmitter; 33, catheter; 34, fixing seat. DETAILED DESCRIPTION

[0035] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0036] When conducting a static load test, after the load box is installed, two grouting pipes need to be set up in the load box for grouting or pumping, which can also be called water injection pipes and water pumping pipes. During the test, broken concrete will remain in the load box. When the test is completed, it is necessary to inject water into the load box through the water injection pipe, and then use the water pumping pipe to pump out the water in the load box to extract the broken concrete, so as to avoid insufficient strength of the foundation piles during re-pouring. Therefore, in order to improve the accuracy of displacement detection and reduce construction difficulty in static load tests.

[0037] See also Figure 1-5The present embodiment provides a self-balancing load box for static load test, including a top plate 11, a hydraulic cylinder 13 and a bottom plate 12 connected in sequence from top to bottom, and also including a distance measuring mechanism 2 and a displacement detector 3. The distance measuring mechanism 2 is vertically installed between the top plate 11 and the bottom plate 12 and is used to detect the distance change between the top plate 11 and the bottom plate 12. In this way, when performing a static load test, the displacement change between the top plate 11 and the bottom plate 12 is detected by the distance measuring mechanism 2, and then the displacement detector 3 is installed on the ground reference frame and is used to detect the distance change between the bottom plate 12 and the reference frame when performing a static load test. In this way, the displacement change of the bottom plate 12 can be detected when performing a static load test, and then the displacement detected by the distance measuring mechanism 2 is subtracted from the detection value of the displacement detector 3 to obtain the displacement of the top plate 11 to complete the test detection;

[0038] In order to better detect the displacement of the bottom plate 12, the displacement detector 3 includes an optical fiber 31, a laser transmitter 32, a receiver, a fixing seat 34 and a guide tube 33. The guide tube 33 is vertically installed on the bottom surface of the reference frame, the fixing seat 34 is located in the guide tube 33 and slides with the guide tube 33, and the receiver is installed on the top surface of the bottom plate 12. One end of the optical fiber 31 is fixedly connected to the fixing seat 34, and the other end is fixedly connected to the receiver. When performing a static load test, the top of the optical fiber 31 is placed in a water injection pipe or a water extraction pipe to prevent the optical fiber 31 from being solidified by the solidified concrete during pouring, causing the bottom plate 12 to sink during the process. During the test, the displacement of the bottom plate 12 cannot be detected. When the bottom plate 12 is detected, the laser emitter 32 is used to generate laser to detect the distance between the bottom plate 12 and the bottom end of the optical fiber 31 during the test. The optical fiber 31 is protected by the conduit 33. When the bottom plate 12 sinks, the optical fiber 31 can be pulled to move the top plate 11 away from the laser emitter 32, thereby extending the detection distance and completing the displacement detection of the bottom plate 12. The conduit 33 is used to keep the optical fiber 31 from being affected by the external environment, and the detection accuracy is guaranteed when the detection is completed.

[0039] In order to ensure the detection accuracy of the optical fiber 31 on the bottom plate 12, in the present embodiment, the optical fiber 31 is composed of an outer layer and a reflective layer, the outer layer wraps the reflective layer, and the outer layer and the reflective layer are both inelastic layers. When performing detection, since the bottom of the optical fiber 31 is fixed, the laser emitted by the laser emitter 32 can be emitted through the emission layer to complete the detection. At the same time, when performing detection, both layers of the optical fiber 31 are inelastic layers. In this way, when performing the test, the overall distance of the optical fiber 31 will not change, thereby maintaining the detection accuracy of the optical fiber 31.

[0040] In order to further ensure the detection accuracy, in one embodiment, a guide hole is opened on the top plate 11, and a guide tube 14 is arranged in the guide hole. The bottom end of the guide tube 14 is located on the top surface of the bottom plate 12 and is sleeved on the outside of the receiver. When conducting the test, broken concrete will be generated in the load box, which will affect the detection accuracy of the bottom of the optical fiber 31. Through the provision of the guide tube 14, the optical fiber 31 is protected from being blocked by the broken concrete during distance detection, thereby ensuring the detection accuracy.

[0041] When the optical fiber 31 is installed in the load box, in order to ensure that the optical fiber 31 can be perpendicular to the bottom plate 12 and improve the detection accuracy, in one embodiment, a clamp 15 is provided on the top surface of the guide hole, and the clamp 15 is used to clamp the optical fiber 31 and keep the optical fiber 31 vertical between the top and the bottom. The optical fiber 31 is supported by the clamp 15 and kept perpendicular to the bottom plate 12, thereby ensuring that the displacement of the bottom plate 12 can be accurately detected when the bottom plate 12 is displaced during detection, thereby ensuring detection accuracy.

[0042] Since the length of the foundation pile is relatively long, in order to better complete the detection of the base plate 12, in one embodiment, the laser emitter 32 emits femtosecond laser pulses. Since the frequency of the femtosecond laser pulse emission is high, the distance to the base plate 12 can be detected multiple times during the detection, thereby ensuring that the detection of the base plate 12 can be better completed, thereby improving the detection accuracy, and the femtosecond laser pulse has a very small thermal effect on the material and the surrounding environment, which can reduce or eliminate thermal damage, thereby ensuring the service life of the optical fiber 31 during the detection.

[0043] During the test, the base plate 12 will sink, thereby pulling the optical fiber 31 to move, and after the test is completed, in order to keep the optical fiber 31 in a vertical state during the entire process, in one embodiment, the displacement detector 3 also includes a spring, one end of the spring is fixedly connected to the top surface of the conduit 33, and the other end is fixedly connected to the fixing seat 34. The bottom plate 12 can pull the optical fiber 31 when displaced through the stretching of the spring, thereby pulling the spring to keep the optical fiber 31 vertical, thereby ensuring the detection accuracy.

[0044] In order to better detect the displacement between the top plate 11 and the bottom plate 12, in one embodiment, the distance measuring mechanism 2 includes a support tube 21, a sliding tube 22, a detection plate 23 and a distance meter 24. The support tube 21 is installed on the top surface of the bottom plate 12, the sliding tube 22 is installed on the bottom surface of the top plate 11 and is on the same axis with the support tube 21, the bottom end of the sliding tube 22 is located in the support tube 21 and is slidably connected to the support tube 21, the detection plate 23 is installed on the bottom surface of the sliding tube 22, the distance meter 24 is installed on the inner bottom surface of the support tube 21, and the distance meter 24 is used to measure the distance change of the detection plate 23. The sliding tube 22 is installed on the bottom surface of the top plate and is on the same axis as the support tube 21: the sliding tube 22 is a tubular structure that can slide in the support tube 21. It shares the same axis with the support tube 21, so that it can be smoothly displaced in the axial direction. The bottom end of the sliding tube 22 is located inside the supporting tube 21 and is slidably connected to the supporting tube 21. The bottom end of the sliding tube 22 is connected to the inner side of the supporting tube 21, so that the sliding tube 22 can slide freely inside the relatively stationary supporting tube 21. The detection plate 23 is a planar structure fixed to the bottom surface of the sliding tube 22 through a connecting structure. When the distance between the top plate 11 and the bottom plate 12 changes, the distance between the detection plates 23 can be detected by the rangefinder 24 to obtain the distance between the top plate 11 and the bottom plate 12, thereby completing the detection of the displacement of the top plate 11.

[0045] In order to better detect the changing distance between the top plate 11 and the bottom plate 12, in one embodiment, the rangefinder 24 is a laser rangefinder 24 or an ultrasonic rangefinder 24. The laser rangefinder 24 refers to a device that uses a laser beam to measure distance. It uses a laser beam transmitter to emit a laser beam, which is received by a receiver after reflection. By measuring parameters such as the transmission time or phase shift of the laser beam, the distance between the object being measured and the laser rangefinder 24 can be calculated, thereby realizing the distance measurement function. Ultrasonic waves are a kind of sound waves with the characteristics of high frequency and high speed propagation, and can be used to measure parameters such as the distance and speed of an object. In the ultrasonic rangefinder 24, the distance is calculated by emitting ultrasonic waves and based on the time it takes for the ultrasonic waves to be reflected by the object.

[0046] Based on the above-mentioned self-balancing static load test load box, the present invention also proposes an efficient self-balancing static load test method, comprising the following steps:

[0047] S1: Fix and weld the top plate 11 and the steel cage of the upper pile, and weld the reinforcing steel bars between the top plate 11 and the upper steel cage; fix and weld the bottom plate 12 and the steel cage of the lower pile, and weld the reinforcing steel bars between the bottom plate 12 and the lower steel cage;

[0048] S2: Place the top end of the optical fiber 31 above the top of the upper pile, and fix the bottom end to the receiver and keep the optical fiber 31 in a vertical state between the bottom plate 12 and the top plate 11;

[0049] S3: lower the entire steel cage to the designated location;

[0050] S4: lowering the pouring pipe, passing through the center hole between the top plate 11 and the bottom plate 12, down to the lower part of the steel cage, and pouring concrete to form a pile;

[0051] S5: Building a reference frame, and installing other components of the displacement detector 3 on the reference frame;

[0052] S6: The optical fiber 31 is fixedly connected to the fixing seat 34 and the optical fiber 31 is kept in a straight state;

[0053] S7: Pressurizing the hydraulic cylinder 13 so that the top plate 11 moves upward, driving the upper pile to move upward, and the bottom plate 12 moves downward, driving the lower pile section to move downward;

[0054] S8: the distance measuring mechanism 2 detects the relative displacement between the top plate 11 and the bottom plate 12, and the displacement detector 3 measures the relative displacement of the bottom plate 12;

[0055] S9: The displacement of the bottom plate 12 is measured by the displacement detector 3, and the displacement of the top plate 11 is the value detected by the distance measuring mechanism 2 minus the measurement result of the displacement detector 3;

[0056] S10: After loading is completed, grouting is performed into the gap between the top plate 11 and the bottom plate 12 through two grouting pipes;

[0057] S11: Cement slurry that meets the design strength requirements and has good fluidity is injected into the space between the top plate 11 and the bottom plate 12 from the grouting pipe to play the role of filling, sealing and fastening the connection.

[0058] In order to better protect the optical fiber 31 from being affected by the pouring concrete and the environment during the test, in one embodiment, in step S2, the optical fiber 31 is vertically placed in the guide tube 14, and the guide tube 14 and the pumping pipe are used to protect the optical fiber 31 from being affected during the test, thereby ensuring the stability of the detection.

[0059] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A load box for self-balancing static load test, comprising a top plate, a hydraulic cylinder and a bottom plate connected in sequence from top to bottom, characterized in that: It also includes a distance measuring mechanism and a displacement detector, wherein the distance measuring mechanism is vertically installed between the top plate and the bottom plate and is used to detect the distance change between the top plate and the bottom plate, and the displacement detector is installed on the ground reference frame and is used to detect the distance change between the bottom plate and the reference frame; The displacement detector comprises an optical fiber, a laser transmitter, a receiver, a fixing seat and a catheter. The catheter is vertically mounted on the bottom surface of the reference frame. The fixing seat is located in the catheter and slides with the catheter. The receiver is mounted on the top surface of the bottom plate. One end of the optical fiber is fixedly connected to the fixing seat to keep the optical fiber in a straight state, and the other end is fixedly connected to the receiver. The displacement detector also includes a spring, one end of which is fixedly connected to the inner top surface of the conduit, and the other end of which is fixedly connected to the fixing seat.

2. A self-balancing static load test load box according to claim 1, characterized in that: The optical fiber consists of an outer layer and a reflective layer, the outer layer wraps the reflective layer, and both the outer layer and the reflective layer are inelastic layers.

3. A self-balancing static load test load box according to claim 2, characterized in that: A guide hole is provided on the top plate, a guide tube is provided in the guide hole, and the bottom end of the guide tube is located on the top surface of the bottom plate and sleeved on the outside of the receiver.

4. A self-balancing static load test load box according to claim 3, characterized in that: A clamp is provided on the top surface of the guide hole, and the clamp is used to clamp the optical fiber and keep the optical fiber vertical between the top and the bottom.

5. A self-balancing static load test load box according to claim 1, characterized in that: The laser emitter emits femtosecond laser pulses.

6. A self-balancing static load test load box according to claim 1, characterized in that: The distance measuring mechanism includes a support tube, a sliding tube, a detection plate and a distance meter. The support tube is installed on the top surface of the bottom plate, the sliding tube is installed on the bottom surface of the top plate and is on the same axis as the support tube, the bottom end of the sliding tube is located in the support tube and is slidably connected to the support tube, the detection plate is installed on the bottom surface of the sliding tube, and the distance meter is installed on the bottom surface of the support tube. The distance meter is used to measure the distance change of the detection plate.

7. A self-balancing static load test load box according to claim 6, characterized in that: The rangefinder is a laser rangefinder or an ultrasonic rangefinder.

8. A self-balancing static load test method, used for a self-balancing static load test load box as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Fix and weld the top plate and the steel cage of the upper pile, and weld the reinforcing steel bars between the top plate and the upper steel cage; fix and weld the bottom plate and the steel cage of the lower pile, and weld the reinforcing steel bars between the bottom plate and the lower steel cage; S2: Place the top of the optical fiber above the top of the upper pile, and fix the bottom end to the receiver and keep the optical fiber vertical between the bottom plate and the top plate; S3: lower the entire steel cage to the designated location; S4: lowering the pouring pipe, passing through the center hole between the top plate and the bottom plate, down to the lower part of the steel cage, and pouring concrete to form a pile; S5: Building a reference frame, and installing other components of the displacement detector on the reference frame; S6: Fix the optical fiber to the fixing seat and keep the optical fiber in a straight state; S7: Pressurize the hydraulic cylinder to move the top plate upward, drive the upper pile to move upward, and move the bottom plate downward, drive the lower pile section to move downward; S8: the distance measuring mechanism detects the relative displacement between the top plate and the bottom plate, and the displacement detector measures the relative displacement of the bottom plate; S9: The displacement of the bottom plate is measured by the displacement detector, and the displacement of the top plate is obtained by subtracting the measurement result of the displacement detector from the value detected by the distance measuring mechanism; S10: After loading is completed, grouting is performed into the gap between the top plate and the bottom plate through two grouting pipes; S11: Cement slurry that meets the design strength requirements and has good fluidity is injected into the space between the top plate and the bottom plate from the grouting pipe to play the role of filling, sealing and tightening the connection.

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