Pile-soil interaction simulation test system and method

Abstract

The invention relates to the technical field of pile foundation tests, in particular to a pile-soil interaction simulation test system and method.The pile-soil interaction simulation test system comprises a vibration table and a test piece placed on the vibration table, and a plurality of pile-soil interaction loading mechanisms are arranged on the vibration table; the pile-soil interaction loading mechanisms are sequentially mounted on the vibration table in the extension direction of a test piece pile shaft, and each pile-soil interaction loading mechanism comprises an arc-shaped component, a spring, a component force plate and a lower sealing plate; the bottom surface of the pile foundation in the test piece abuts against the steel plate; a force sensor is mounted between the steel plate and the pile bottom; a pile end anchoring part is arranged at the end part of the pile foundation in the test piece; a pile axial force loading mechanism is arranged between the steel plate and the bearing platform; the device is simple in structure, ingenious in construction, small in size and easy to install and operate, and the vibration table test of the large-size pile foundation test piece can be completed. And the economic benefit is high.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation testing, in particular to a pile-soil interaction simulation testing system and method. Background Art

[0002] At present, the problem of pile foundation design is that only attention is paid to the calculation of vertical force and the horizontal seismic force is mostly ignored. The normal seismic design of pile foundation should include the consideration of vertical force and horizontal force, as well as the consideration of the coordinated work of foundation and superstructure; because the aspect ratio of pile foundation is generally large, its vertical bearing capacity is high, while the horizontal bearing capacity is relatively poor. The lateral strength of pile is the difficulty of pile seismic design, because people have not studied the stress and strain caused by the relative action of pile and soil under earthquake response deeply enough.

[0003] Pile-soil coupling interaction is a complex problem. Currently, there are two main types of test methods used in the study of pile-soil interaction seismic response, namely field test and indoor test. Field test can provide site conditions consistent with the prototype structure and full-scale model structure, but the cost of field test is expensive and it is impossible to carry out a large number of comparative experiments. In addition, the application of experimental load is often applied to the pile head through the excitation vibrator, which is far from the actual conditions of pile-soil-structure interaction under seismic load. Indoor model test has high economic benefits and is under controlled indoor conditions. It has good repeatability and can carry out a large number of comparative tests in a short time. In indoor model test, the boundary effect is mainly simulated by using shear box. However, due to the small size of the model box and the table, only small-scale model tests can be carried out, and the installation of measurement equipment is increased. In summary, there are still many areas that need to be improved in the current shaking table test of pile-soil coupling. Summary of the invention

[0004] The purpose of the present application is to provide a pile-soil interaction simulation test system and method, aiming to solve the problems in the prior art.

[0005] The embodiment of the present application provides a pile-soil interaction simulation test system, including a vibration table and a pile-cap test piece placed on the table; the vibration table is provided with a plurality of pile-soil interaction loading mechanisms; the pile-soil interaction loading mechanisms are sequentially installed on the vibration table along the extension direction of the specimen pile axis, and the pile-soil interaction loading mechanisms include an arc-shaped member, a spring, a force distribution plate and a lower sealing plate; the arc-shaped member is composed of two connected 1 / 4 circular ring segments; the lower sealing plate is composed of two connected mounting plates; the inner surface of the mounting plate is a circular arc steel segment; the segment radius of the inner surface of the mounting plate is The same as the arc-shaped member; the bottom of the arc-shaped member is connected to the lower sealing plate; the force distribution plate is a plurality of steel arc-shaped segments; the force distribution plate is laid and installed on the outer surface of the test pile; one end of the spring is welded to the outer side of the force distribution plate, and the other end of the spring is connected to the arc-shaped member and the lower sealing plate through a long straight bolt; the spring is used to simulate the earth pressure effect of the soil layer around the pile; the bottom surface of the pile base in the specimen is abutted against the steel plate; a force sensor is installed between the steel plate and the pile bottom; a pile end anchor is provided at the end of the pile foundation in the specimen; a pile axial force loading mechanism is provided between the steel plate and the pedestal; a slide rail mechanism is provided at the bottom of the pedestal in the specimen.

[0006] Furthermore, the lower sealing plate is connected to the arc-shaped member by bolts; and the bottom of the lower sealing plate is arranged on the surface of the vibration table by bolts.

[0007] Furthermore, the pile end anchor comprises an upper hoop plate, a rubber pad and a lower hoop plate; the upper hoop plate is a semicircular pipe segment; the upper part of the lower hoop plate is a semicircular pipe segment, and the bottom of the lower hoop plate is bolted to the vibration table; the pipe segment radius of the lower hoop plate is the same as that of the upper hoop plate; the rubber pad is sleeved on the end of the pile foundation; the upper hoop plate and the lower hoop plate are connected by bolts to form a circular ring, which is clamped on the outer surface of the rubber pad.

[0008] Furthermore, the pile axial force loading mechanism includes a prestressed steel cable and an anchor; one end of the prestressed steel cable passes through the base, and the other end passes through the steel plate; the end of the prestressed steel cable is fixed by an anchor.

[0009] Furthermore, the slide rail mechanism includes an upper slide rail and a lower slide rail, and the upper slide rail and the lower slide rail each include at least two slide rails; the upper slide rail is installed perpendicular to the pile axis and is slidably connected to the base to simulate horizontal shear force; the upper slide rail and the lower slide rail are arranged orthogonally to each other.

[0010] Furthermore, the lower slide rail is installed along the pile axis direction and is slidably connected to the vibration table; a connecting steel plate is provided between the upper slide rail and the lower slide rail; and guide rails and sliding blocks are provided on the upper and lower surfaces of the connecting steel plate respectively.

[0011] A test method based on a pile-soil interaction simulation test system comprises the following steps:

[0012] Step S1: Processing the pile and cap test piece, and pasting the strain gauge, displacement sensor, and acceleration sensor at the designated position;

[0013] Step S2: Fix the bottom of the slide rail mechanism to the installation position on the vibration table surface;

[0014] Step S3: fixing the lower sealing plate in the pile-soil action loading mechanism to the table installation position;

[0015] Step S4: hoisting the pile and cap test piece, fixing the cap on the slide rail mechanism with bolts, and placing the pile body on the force component plate of the lower sealing plate in the pile-soil action loading mechanism;

[0016] Step S5: Pass one end of the pre-selected prestressed steel cable through the reserved hole of the cap, and the other end through the thick steel plate on the pile end, set a force sensor between the pile end and the thick steel plate, tension the prestressed steel cable at both ends, load step by step according to the design standard value, and observe the axial force of the pile body through the force sensor. When the load reaches 100% of the design standard value, the residence time is 5 minutes, and the two ends of the prestressed steel cable are anchored with anchors to keep the axial force of the pile body unchanged;

[0017] Step S6: fastening the arc-shaped components in the pile-soil loading mechanism to the lower sealing plates in pairs by bolts;

[0018] Step S7: Connect the data cables of each test instrument to the computer to test the normal use of the data acquisition system;

[0019] Step S8: Start the vibration table test and collect test data.

[0020] The beneficial effects of the present invention are as follows: the test device has a simple structure, an ingenious construction, a small size, and is easy to install and operate, and can realize the shaking table test of large-sized pile foundation specimens. The economic benefits are high, and under controlled indoor conditions, the main structural materials can be reused, meeting the environmental protection requirements, and a large number of comparative tests can be carried out in a short time. The problem of using a shear box to simulate boundary effects, which requires a large test table, is difficult to simulate pile-soil interaction, and generally can only carry out small-scale model tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the top structure of the present invention.

[0022] Figure 2 It is a side view structural schematic diagram of the present invention.

[0023] Figure 3 Front cross-sectional view of the pile-soil interaction loading mechanism.

[0024] Figure 4Side cross-sectional view of the pile-soil interaction loading mechanism.

[0025] Figure 5 Schematic diagram of the pile end anchor structure.

[0026] Figure 6 It is a schematic diagram of the slide rail mechanism structure.

[0027] In the figure:

[0028] 1. Test pile; 2. Arc-shaped member; 3. Spring; 4. Force distribution plate; 5. Lower sealing plate; 6. Capping platform; 7. Prestressed steel cable; 8. Force sensor; 9. Steel plate; 10. Anchor; 11. Slide rail mechanism; 12. Vibration table; 13. Upper hoop plate; 14. Rubber pad; 15. Lower hoop plate; 16. First connecting steel plate; 17. Upper slide rail; 18. Connecting steel plate; 19. Lower slide rail; 20. Second connecting steel plate. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] like Figures 1 to 6A pile-soil interaction simulation test system shown in the figure comprises a vibration table 12 and a specimen placed on the table, wherein the specimen is a pile-capped platform specimen; a plurality of pile-soil interaction loading mechanisms are arranged on the vibration table 12; the pile-soil interaction loading mechanisms are sequentially installed on the vibration table 12 along the extension direction of the specimen pile axis, and can be installed at the same intervals, and the pile-soil interaction loading mechanisms comprise an arc-shaped member 2, a spring 3, a force distribution plate 4 and a lower sealing plate 5; the arc-shaped member 2 is composed of two connected 1 / 4 circular ring segments; a circular steel plate is welded in the outer normal direction of the segment, and bolt holes are left on the steel plate circular ring, which is bolted to another segment and the lower sealing plate 5 by bolts; the lower sealing plate 5 is composed of two connected mounting plates; the inner surface of the mounting plate is a circular arc steel segment; the mounting plate The segment radius of the inner surface of the mounting plate is the same as that of the arc-shaped member 2; the bottom of the arc-shaped member 2 is connected to the lower sealing plate 5; the force distribution plate 4 is a plurality of steel arc-shaped segments; the force distribution plate 4 is regularly arranged and laid and installed on the outer surface of the test pile 1; one end of the spring 3 is welded to the outer side of the force distribution plate 4, and the other end of the spring 3 is connected to the arc-shaped member 2 and the lower sealing plate 5 through a long straight bolt, and the bolt is bolted to the segment of the arc-shaped member 2 to fix the spring 3, and the characteristic parameters of the spring 3 are designed according to the soil spring stiffness requirements; the bottom surface of the pile base in the specimen is abutted against the steel plate 9; a force sensor 8 is installed between the steel plate 9 and the pile bottom; a pile end anchor is provided at the end of the pile foundation in the specimen; a pile axial force loading mechanism is provided between the steel plate 9 and the base 6; a slide rail mechanism is provided at the bottom of the base in the specimen. The arc-shaped member 2 and the lower sealing plate 5 are bolted together to form a circular ring. Several springs 3 are evenly bolted to the inner surface of the circular ring. The springs are compressed and the force plate 4 fixed to the end of the spring is pressed against the outer surface of the test pile 1 to complete the laboratory simulation of pile-soil interaction.

[0031] The lower sealing plate 5 is connected to the arc-shaped member 2 by bolts; the bottom of the lower sealing plate 5 is set on the surface of the vibration table 12 by bolts; the number of springs 3 is symmetrically arranged according to demand, and the elastic stiffness of the spring 3 is designed according to the soil spring stiffness requirement. The spring is located and installed between the arc-shaped member 2 and the pile body of the test pile 1, and is in a compressed state to simulate the soil pressure effect of the soil layer around the pile.

[0032] The pile end anchor comprises an upper hoop plate 13, a rubber pad 14 and a lower hoop plate 15. When the pile end is embedded in a hard soil layer, the constraint effect of the soil layer on the pile end can be ignored, and the pile end can be regarded as a free end, and no additional constraint is required for simulation. However, when the pile end is embedded in a rock layer, the constraint effect of the soil layer on the pile end cannot be ignored, and the pile end anchor is used to simulate the constraint effect of the rock layer on the pile end.

[0033] The upper hoop plate 13 is a semicircular segment; the upper part of the lower hoop plate 15 is a semicircular segment, and the bottom of the lower hoop plate 15 is bolted to the vibration table 12; the segment radius of the lower hoop plate 15 is the same as that of the upper hoop plate 13; the rubber pad 14 is connected to the end of the pile foundation; the upper hoop plate 13 and the lower hoop plate 15 are connected by bolts to form a circular ring, which is clamped on the outer surface of the rubber pad 14 to play a buffering role and avoid damage caused by hard contact at the pile end.

[0034] The pile axial force loading mechanism includes a prestressed steel cable 7 and an anchor 10 ; one end of the prestressed steel cable 7 passes through a reserved hole on the base 6 , and the other end passes through a steel plate 9 ; the prestressed steel cable end 7 is fixed by the anchor 10 .

[0035] The slide rail mechanism includes an upper slide rail 17 and a lower slide rail 19, and the upper slide rail 17 and the lower slide rail 19 each include at least two slide rails; the upper slide rail 17 and the lower slide rail 19 are arranged orthogonally to each other; the upper slide rail 19 is installed perpendicular to the pile axis direction of the test pile 1 and is slidably connected to the cap 6; the lower slide rail 19 is installed along the pile axis direction and is slidably connected to the vibration table 12; the upper slide rail 17 here is to ensure that the cap 6 located above the slide rail can slide horizontally along the loading direction of the vibration table 13, generate shear force, and act on the pile head to simulate the horizontal inertial force of the upper structure acting on the pile head under the action of horizontal earthquake in actual construction. The lower slide rail 19 is to ensure that the cap 6 located above the slide rail can slide along the pile axis direction. The upper slide rail 17 and the lower slide rail 19 described here are not limited to the combination of guide rails and sliders, but can also be a combination of other forms such as balls, slide rods, bearings, etc. that can produce linear sliding.

[0036] A connecting steel plate 18 is provided between the upper slide rail 17 and the lower slide rail 19; guide rails and sliders are provided on the upper and lower surfaces of the connecting steel plate 18, respectively, the guide rail is the guide rail of the upper slide rail 17, and the slider is a slider slidably connected to the lower slide rail 19; in actual use, the first connecting steel plate 16 can be fixedly set at the bottom of the base by bolting or binding to evenly transfer the upper load to the track; a second connecting steel plate 20 is set on the surface of the vibration table 12, and the lower slide rail 19 is fixed on the second connecting steel plate 20 to transfer the acceleration load transmitted from the surface of the vibration table 12.

[0037] A test method based on a pile-soil interaction simulation test system comprises the following steps:

[0038] Step S1: Processing the pile and cap test piece, and pasting the strain gauge, displacement sensor, and acceleration sensor at the designated position;

[0039] Step S2: Fix the bottom of the slide rail mechanism to the mounting position on the vibration table 12;

[0040] Step S3: fixing the lower sealing plate 5 in the pile-soil action loading mechanism to the table installation position;

[0041] Step S4: hoisting the pile and cap test piece, the cap is fixed on the slide rail mechanism with bolts, and the pile body is placed on the force plate 4 of the lower sealing plate 5 in the pile-soil action loading mechanism;

[0042] Step S5: Pass one end of the pre-selected prestressed steel cable 7 through the reserved hole of the cap 6, and the other end through the steel plate 9 on the top of the pile end, set a force sensor between the pile end and the thick steel plate, tension the prestressed steel cable at both ends, load step by step according to the design standard value, and observe the axial force of the pile body through the force sensor. When the load reaches 100% of the design standard value, the residence time is 5 minutes, and the two ends of the prestressed steel cable are anchored with anchors to keep the axial force of the pile body unchanged;

[0043] Step S6: The arc-shaped members 2 in the pile-soil loading mechanism are fixedly connected to the lower sealing plates 5 by bolts;

[0044] Step S7: Connect the data cables of each test instrument to the computer to test the normal use of the data acquisition system;

[0045] Step S8: Start the vibration table test and collect test data.

[0046] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A pile-soil interaction simulation test system, comprising a vibration table and a pile-cap specimen placed on the table, characterized in that: The vibration table is provided with a plurality of pile-soil interaction loading mechanisms; the pile-soil interaction loading mechanisms are sequentially installed on the vibration table along the extension direction of the pile axis of the specimen, and the pile-soil interaction loading mechanisms include an arc-shaped member, a spring, a force distribution plate and a lower sealing plate; the arc-shaped member is composed of two connected 1 / 4 circular ring segments; the lower sealing plate is composed of two connected mounting plates; the inner surface of the mounting plate is an arc steel segment; the segment radius of the inner surface of the mounting plate is the same as that of the arc-shaped member; the bottom of the arc-shaped member is connected to the lower sealing plate The force distribution plate is a plurality of steel arc-shaped segments; the force distribution plate is laid and installed on the outer surface of the test pile; one end of the spring is welded to the outer side of the force distribution plate, and the other end of the spring is connected to the arc-shaped member and the lower sealing plate through a long straight bolt; the spring is used to simulate the earth pressure effect of the soil layer around the pile; the bottom surface of the pile base in the specimen is in contact with the steel plate; a force sensor is installed between the steel plate and the pile bottom; a pile end anchor is provided at the end of the pile foundation in the specimen; a pile axial force loading mechanism is provided between the steel plate and the pedestal; a slide rail mechanism is provided at the bottom of the pedestal in the specimen.

2. The pile-soil interaction simulation test system according to claim 1, characterized in that: The lower sealing plate is connected to the arc-shaped member by bolts; and the bottom of the lower sealing plate is arranged on the surface of the vibration table by bolts.

3. The pile-soil interaction simulation test system according to claim 1, characterized in that: The pile end anchor comprises an upper hoop plate, a rubber pad and a lower hoop plate; the upper hoop plate is a semicircular pipe segment; the upper portion of the lower hoop plate is a semicircular pipe segment, and the bottom of the lower hoop plate is bolted to the vibration table; the pipe segment radius of the lower hoop plate is the same as that of the upper hoop plate; the rubber pad is sleeved on the end of the pile foundation; the upper hoop plate and the lower hoop plate are connected by bolts to form a circular ring, which is clamped on the outer surface of the rubber pad.

4. The pile-soil interaction simulation test system and method according to claim 1, characterized in that: The pile axial force loading mechanism comprises a prestressed steel cable and an anchor; one end of the prestressed steel cable passes through the cap, and the other end passes through the steel plate; the end of the prestressed steel cable is fixed by the anchor.

5. The pile-soil interaction simulation test system and method according to claim 1, characterized in that: The slide rail mechanism includes an upper slide rail and a lower slide rail, and the upper slide rail and the lower slide rail each include at least two slide rails; the upper slide rail is installed perpendicular to the pile axis and is slidably connected to the base, and is used to simulate horizontal shear force; the upper slide rail and the lower slide rail are arranged orthogonally to each other.

6. The pile-soil interaction simulation test system and method according to claim 5, characterized in that: The lower slide rail is installed along the pile axis direction and is slidably connected to the vibration table; a connecting steel plate is provided between the upper slide rail and the lower slide rail; and guide rails and sliding blocks are provided on the upper and lower surfaces of the connecting steel plate respectively.

7. A test method based on the pile-soil interaction simulation test system as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1: Processing the pile and cap test piece, and pasting the strain gauge, displacement sensor, and acceleration sensor at the designated position; Step S2: Fix the bottom of the slide rail mechanism to the installation position on the vibration table surface; Step S3: fixing the lower sealing plate in the pile-soil action loading mechanism to the table installation position; Step S4: hoisting the pile and cap test piece, fixing the cap on the slide rail mechanism with bolts, and placing the pile body on the force component plate of the lower sealing plate in the pile-soil action loading mechanism; Step S5: Pass one end of the pre-selected prestressed steel cable through the reserved hole of the cap, and the other end through the thick steel plate on the pile end, set a force sensor between the pile end and the thick steel plate, tension the prestressed steel cable at both ends, load step by step according to the design standard value, and observe the axial force of the pile body through the force sensor. When the load reaches 100% of the design standard value, the residence time is 5 minutes, and the two ends of the prestressed steel cable are anchored with anchors to keep the axial force of the pile body unchanged; Step S6: fastening the arc-shaped components in the pile-soil loading mechanism to the lower sealing plates in pairs by bolts; Step S7: Connect the data cables of each test instrument to the computer to test the normal use of the data acquisition system; Step S8: Start the vibration table test and collect test data.

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