Multi-angle Shear Test Device for the Rough Interface between Soil Mass and Structure and Its Operation Method

Abstract

The present invention discloses a multi-angle shear test device for a rough interface between soil and structure and its operation method. The test device includes an upper shear box, a lower shear box, a loading system and a data acquisition instrument. A load transfer plate, a permeable stone, filter paper and a shear specimen are arranged in the upper shear box. A serrated shear surface module, a corner control component and a limit torque measurement component are arranged in the lower shear box. The serrated shear surface module is provided with serrated lines and guiding ribs. The corner control component is provided with a deflection angle guiding groove, a floating round table and a torque blocking fan ring. The limit torque measurement component includes a round table limit groove, a fan ring limit groove, a tapered roller bearing, a micro pressure sensor and a spiral preloading structure. The loading system includes a horizontal loading system and a vertical loading system. The present invention can simulate diverse inclination angles of rough interface lines, keep the direction of the serrated lines constant during shear and accurately measure the interface shear torque, providing reliable support for the comprehensive evaluation of the pile-soil interaction performance in the reinforcement projects of rotary drilled piles and screw piles.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical tests, and particularly relates to a multi-angle shear test device for a soil-structure rough interface and an operation method thereof. Background Art

[0002] In the pile-reinforced foundation engineering, the premise of carrying out foundation reinforcement design and performance evaluation is to clarify the pile-soil interaction characteristics. However, the pile-soil interaction characteristics and their interface parameters often need to be tested through soil-structure shear tests. In fact, affected by factors such as geological conditions, site environment, and construction methods, whether it is a steel pipe pile, a reinforced concrete pile or other types of pile bodies, the surface of the pile body is not absolutely smooth and will show a certain degree of roughness. The roughness of the pile-soil interface significantly affects the pile-soil interface interaction characteristics, and then affects the driving operation of precast pile bodies, the bearing capacity of pile foundations, and the foundation reinforcement effect. Therefore, when testing the shear performance of the pile-soil interface, the fact of the roughness of the pile-soil interface must be considered. For typical cast-in-place pile construction, after the hole is formed by a rotary drilling rig, since the cutting blades of the rotary drilling rig rotate and lift or lower at the same time, this causes inclined threads to be formed on the inner wall of the borehole. The inclined thread pattern forms an angle (also called an included angle) with the borehole axis. The size of this included angle is related to factors such as the blade rotation speed of the rotary drilling rig, the lifting / lowering speed of the drill pipe, and the formation soil quality. The inclined threads on the inner wall of the borehole cause corresponding inclined depressions / protrusions to be formed on the wall of the cast-in-place pile, so a rough interface with an included angle is formed between the pile body and the soil. In addition, since the outer wall of the thread is more conducive to improving the vertical bearing capacity and reinforcement effect of the pile foundation, more and more pile foundation projects use threaded piles, and the interface between this pile body and the soil is also a typical rough interface with an included angle. The inventor found that when the pile-soil interface is a rough interface with an included angle, the pile body not only generates axial stress under the action of the upper vertical load, but also torsional stress will appear. The strength of this torsional action is related to factors such as soil layer characteristics, thread protrusion height, thread included angle, and its spacing. How to measure and calculate the torsional stress of the pile body with a rough interface with an included angle and accurately check the anti-torsion bearing capacity is of great significance for the reasonable design of the pile foundation structure.

[0003] Currently, the prior art mainly realizes a simple simulation of the rough interface. However, in the process of implementing the present invention, the inventor found that the prior art still has the following problems:

[0004] (1) The shear surface module is a component used to simulate the rough outer surface of the structure in the interface shear test. The roughness simulation design of its surface directly affects the test results. Furthermore, if the diversified interface performance of the soil-structure is to be studied, a series of shear surface modules with different roughness and a changing shear direction must be selected. The replacement of the shear surface modules thus caused the test operation steps to be complicated and costly. For example, the invention patent application with publication number CN115266405A discloses a shear test device with adjustable interface roughness. It achieves the purpose of different rough interfaces by replacing steel plates with different roughness. A large number of steel plates with different roughness need to be processed, which costs high test and labor costs.

[0005] (2) In the absence of restrictions on the rotation of the shear surface module, the soil will exert a torsional force on the shear surface module during the shearing process, causing the serrations of the shear surface module to move toward the shear direction under the torsion. That is, the inclination angle (angle) between the interface serrations and the shear direction gradually decreases during the shearing process, which will cause the test results of the rough interface shear test with an inclination to be smaller and distorted. At the same time, the current rough interface shear test device has not yet paid attention to the torsional effect generated during the interface shearing process, and has not attempted to measure the torque during the shearing process. Summary of the invention

[0006] The purpose of the present invention is to provide a soil-structure rough interface multi-angle shear test device with the functions of simulating diversified interface roughness, simply adjusting the shear angle, limiting the rotation of the sawtooth shear surface module and monitoring the torsion effect, so as to solve the problems raised in the background technology.

[0007] To achieve the above object, the present invention provides a multi-angle shear test device for the rough interface between soil and structure, including a shear box, a loading system and a data acquisition instrument; the shear box includes an upper shear box and a lower shear box. In the inner cavity of the upper shear box, a load transfer plate, a permeable stone, a filter paper and a shear specimen are sequentially arranged from top to bottom. In the inner cavity of the lower shear box, a serrated shear surface module, a corner control component and a limit torque measurement component are sequentially arranged from top to bottom. The upper surface of the serrated shear surface module is provided with serrations for closely contacting the lower surface of the shear specimen, and the lower surface of the serrated shear surface module is provided with guiding ribs. The corner control component includes a round cake structure, a suspended frustum and two anti-torsion fan rings. On the upper surface of the round cake structure, a plurality of deflection angle guiding grooves passing through its geometric center are opened. The suspended frustum and the anti-torsion fan rings are arranged at the bottom of the round cake structure. The center of the suspended frustum coincides with the center of the lower surface of the corner control component, and the two anti-torsion fan rings are symmetrically arranged on both sides of the suspended frustum. The limit torque measurement component includes a frustum limit groove, a fan ring limit groove, a tapered roller bearing, a micro pressure sensor and a spiral preloading structure. The frustum limit groove and the fan ring limit groove are recessed downward from the upper surface of the base of the lower shear box. The center of the frustum limit groove coincides with the center of the base of the lower shear box, and the tapered roller bearing is arranged in the frustum limit groove. There are two fan ring limit grooves, which are symmetrically arranged on both sides of the frustum limit groove. Each end of each fan ring limit groove is provided with a torque measurement recess, and a horizontal threaded channel penetrating the side wall of the lower shear box is arranged on the side wall inside the torque measurement recess. A micro pressure sensor is correspondingly arranged in each torque measurement recess. A spiral preloading structure is arranged in each horizontal threaded channel. The spiral preloading structure includes a hollow screw top and a return spring. The suspended frustum is placed in the cavity in the middle of the tapered roller bearing and is in close contact with the tapered roller bearing. The loading system includes a horizontal loading system and a vertical loading system. The horizontal loading system includes a shear pushing motor, a horizontal load sensor and a horizontal displacement sensor. The top of the horizontal push rod of the shear pushing motor contacts the lower shear box. The horizontal load sensor is arranged on the front side in the advancing direction of the upper shear box. The vertical loading system includes an electric control loading frame, a vertical load sensor and a vertical displacement sensor. The data acquisition instrument is connected to the loading system to transmit the data monitored by each sensor to a computer terminal.

[0008] Further, the cross-sections of the inner cavities of the upper shear box and the lower shear box are both circular, and the upper shear box and the lower shear box are fixedly connected by fixing pins; a directional wheel rail is arranged at the bottom of the lower shear box.

[0009] Further, the vertices of the serrations of the serrated shear surface module are flush with the interface height between the upper shear box and the lower shear box.

[0010] Further, the torsion-resistant sector ring and the floating frustum are respectively embedded in the sector-ring limiting groove and the frustum limiting groove, and the tapered roller bearing is located between the floating frustum and the frustum limiting groove; there is a gap between the bottom surface of the tapered roller bearing and the bottom surface of the floating frustum and the bottom surface of the frustum limiting groove; there is also a gap between the bottom surface of the disc structure and the top surface of the base of the lower shear box.

[0011] Further, the serrated shear surface module is a series of test pieces, and the serrated patterns between the series of serrated shear surface modules are set as undulating patterns with different combinations of tooth depth, tooth pitch, tooth width, and chamfer; different interface roughnesses are simulated by selecting serrated shear surface modules with different undulating patterns; there is one guiding rib, and the length direction of the guiding rib is consistent with the trend of the serrated pattern.

[0012] Further, the guiding rib is engaged with different deflection-angle guiding grooves to achieve multiple angle settings between the trend of the serrated pattern on the serrated shear surface module and the shear direction; the symmetry axis passing through the torsion-resistant sector ring and the floating frustum is perpendicular to the shear direction.

[0013] Further, there is no contact between the circumferences of the serrated shear surface module and the corner control assembly and the inner cavity side wall of the lower shear box, and the corner control assembly is in contact with the micro pressure sensor and the tapered roller bearing respectively through the torsion-resistant sector ring and the floating frustum; lubricant is applied to the inner cavity side walls of the upper shear box and the lower shear box and at the interface between the two.

[0014] Further, each micro pressure sensor is correspondingly placed at the top of the corresponding spiral preloading structure and is connected by the corresponding return spring; the wire of each micro pressure sensor is led out through the hollow inner core channel of the hollow screw cap and is connected to the corresponding channel on the data acquisition instrument; by screwing in or out the hollow screw cap and adjusting the return spring, the micro pressure sensor protrudes slightly from the end side wall of the sector-ring limiting groove and is in pressure contact with the top end of the hollow screw cap and the end of the torsion-resistant sector ring; the initial reading of the micro pressure sensor should be set to 5 kPa to 10 kPa.

[0015] Further, during the shear test, the pressure values of the four micro pressure sensors are read, and the formed torque T can be calculated by the following formula:

[0016]

[0017] In the formula, the pressure values P1 and P2 are the readings of two micro pressure sensors at both ends of one of the sector ring limit grooves, and the pressure values P3 and P4 are the readings of the micro pressure sensors at both ends of the other sector ring limit groove; R is the horizontal distance from the central axis of the sector ring limit groove to the center of the frustum limit groove.

[0018] The present invention also provides an operation method for the soil-structure rough interface multi-angle shear test device as described above, including the following steps:

[0019] S1. First, place the lower shear box on the directional wheel track and fasten it, clean the debris in the limit torque measurement assembly, apply lubricant to the frustum limit groove and the sector ring limit groove, and place the tapered roller bearing in the frustum limit groove; then, counterclockwise screw out the hollow screw jack so that each micro pressure sensor retracts into the torque measurement recess at the end side wall of the sector ring limit groove where it is located, and respectively and correctly embed the floating frustum and the torque blocking sector ring of the rotation angle control assembly into the cavity in the middle of the tapered roller bearing and the sector ring limit groove; secondly, according to the included angle between the sawtooth pattern direction on the sawtooth shear plane module preset for the interface shear test and the shear direction, engage the guiding rib of the sawtooth shear plane module on a certain deflection angle guiding groove; finally, symmetrically and clockwise screw in the hollow screw jack so that each micro pressure sensor slightly protrudes from the end side wall of the sector ring limit groove where it is located and makes pressure contact with the top end of the hollow screw jack and the end of the torque blocking sector ring until the initial readings of all micro pressure sensors are the same;

[0020] S2. Apply lubricant to the upper surface of the lower shear box, align and place the upper shear box on the lower shear box, insert the fixing pin, apply lubricant evenly to the inner walls of the upper shear box and the lower shear box, and sleeved with a casing having the same inner cavity size as the upper shear box on the upper shear box to ensure that the inner cavity of the casing is aligned with the inner cavity of the upper shear box; weigh a specified mass of soil, pour it into the inner cavity of the shear box, and use a T-shaped soil compactor matching the casing to compact the soil to a specified height to form a shear specimen, then remove the T-shaped soil compactor and the casing in sequence, and place a filter paper, a permeable stone and a load transfer plate on the upper surface of the shear specimen in sequence;

[0021] S3. Adjust the horizontal loading system so that the rear side in the advancing direction of the lower shear box just contacts the horizontal push rod of the shear advancing motor, and set the readings of the horizontal displacement sensor and the horizontal load sensor to zero; align the force transfer rod of the electric control loading frame with the central groove on the load transfer plate, install the vertical displacement sensor and the vertical load sensor, and set the readings of the vertical displacement sensor and the vertical load sensor to zero;

[0022] S4. Control the vertical load sensor on the electric control loading frame through the computer terminal to apply a preset vertical pressure or the vertical pressure required by relevant specification standards;

[0023] S5, after applying vertical pressure, remove the fixing pin and start shearing again, and collect data from each sensor in real time;

[0024] S5. After the shearing is completed, adjust the vertical load sensor reading to zero, remove the vertical pressure, ensure that the force transmission rod of the electronically controlled loading frame is separated from the pressure transmission plate, remove the pressure transmission plate, the permeable stone and the upper shear box in turn, and check the shear morphology of the interface between the shear specimen and the serrated shear surface module; unscrew the hollow top screw counterclockwise to reduce the reading of each micro pressure sensor to zero; then disassemble the lower shear box and the serrated shear surface module, the angle control component and the limit torque measurement component in its inner cavity in turn, clean and dry the components of the test device, organize and analyze the test data, and obtain the change curves of the shear stress, normal displacement and torque of the soil-structure interface with the shear displacement;

[0025] S6. Repeat steps S1 to S5 to carry out the next set of tests.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Diversified angles of interface roughness

[0028] The present invention considers the phenomenon that there is an angle between the direction of the rough texture of the interface and the shear direction, and splits the traditional interface roughness simulation structure into two structures, namely, a sawtooth shear surface module and an angle control component. Compared with the traditional interface roughness simulation structure, the sawtooth shear surface module in the present invention is thinner and lighter, and only one angle control component is required, so the material consumption is significantly reduced, saving the test cost; in addition, a plurality of deflection angle guide grooves are arranged on the upper surface of the angle control component, and the initial angle between the direction of the sawtooth texture on the sawtooth shear surface module and the shear direction is changed from 0 to 90° by selecting different deflection angle guide grooves to engage the guide ribs, thereby more realistically simulating the actual situation that the concave and convex textures on the surface of the structure are inclined to the shear direction of the structure-soil interface, solving the problem that the angle of the direction of the rough texture of the interface cannot be considered in the traditional test device or the problem that as many interface roughness simulation structures as the angles considered must be made.

[0029] (2) Keep the serrations constant during shearing

[0030] The present invention innovatively arranges a torsion-resistant fan ring on the lower surface of the angle control component, and arranges a fan ring limiting groove in the base of the lower shear box. The engagement of the torsion-resistant fan ring with the fan ring limiting groove can avoid rotation of the angle control component and the serrated shear surface module during shearing, thereby solving the problem of small and distorted shear stress test values ​​and ensuring that the shear stress test results are reliable.

[0031] (3) Accurate measurement and control of interface shear torque

[0032] When considering that the conventional interface shear test ignores the torsional effect generated during the shear process, the present invention not only avoids the shear stress measurement error caused by the torsional effect through the above-mentioned rotation angle control component, but also pays attention to the torque formed by the torsional effect. By setting a torque measurement recess at the end of the fan-shaped ring groove and installing a micro pressure sensor inside to innovatively measure the pressure generated by torsion, and then calculate the torque. In addition, in terms of the structure for reducing torque error, a tapered roller bearing is placed in the circular table limiting groove of the limit torque measurement component, greatly reducing the frictional resistance between the suspended circular table and the circular table limiting groove, and making the rotation angle control component suspended without contacting the lower shear box, and the torque blocking fan-shaped ring only contacts the micro pressure sensor; in addition, lubricant is applied between the inner walls of the upper and lower shear boxes and the component interface surfaces to avoid the frictional resistance caused by the contact of the soil body or components. Through the above structural design of the present invention, an accurate torque value can be obtained.

[0033] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The following will refer to the accompanying drawings and make a further detailed description of the present invention. Brief Description of the Drawings

[0034] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification, and are used together with the following specific embodiments to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the accompanying drawings:

[0035] Figure 1 It is a schematic three-dimensional structure diagram of the test device of an embodiment of the present invention, where Figure 1 (a) is a three-dimensional view from the obliquely front, Figure 1 and (b) is a three-dimensional view from the obliquely rear;

[0036] Figure 2 It is a schematic cross-sectional structure diagram of the shear box of an embodiment of the present invention;

[0037] Figure 3 It is a schematic diagram of the serrated shear surface module of an embodiment of the present invention, where Figure 3 (a) is a three-dimensional view, Figure 3 and (b) is a cross-sectional view;

[0038] Figure 4 It is a schematic diagram of the rotation angle control component of an embodiment of the present invention, where Figure 4 (a) is a three-dimensional view, Figure 4 and (b) is a top view, Figure 4 and (c) is a bottom view;

[0039] Figure 5 It is a schematic diagram of the limit torque measurement component in the lower shear box of an embodiment of the present invention, where Figure 5 (a) is a three-dimensional view,Figure 5 (b) is a top view;

[0040] Figure 6 Schematic diagram of a spiral preloading structure and a micro pressure sensor according to an embodiment of the present invention, where Figure 6 (a) is a three-dimensional view, Figure 6 (b) is a sectional view;

[0041] Figure 7 Schematic diagram of the detailed connection of channels on a data collector according to an embodiment of the present invention;

[0042] Wherein, 1 - shear box; 1.1 - upper shear box; 1.2 - lower shear box; 2 - loading system; 2.1 - horizontal loading system; 2.2 - vertical loading system; 3 - data collector; 4 - load transfer plate; 4.1 - central groove; 5 - permeable stone; 6 - filter paper; 7 - shear specimen; 8 - fixing pin; 9 - serrated shear surface module; 10 - corner control component; 11 - limit torque measurement component; 12 - directional wheel rail; 13 - serrated pattern; 14 - guiding rib; 15 - round cake structure; 16 - deflection angle guiding groove; 17 - suspended frustum; 18 - torque blocking fan ring; 19 - frustum limit groove; 20 - fan ring limit groove; 21.1, 21.2, 21.3, 21.4 - micro pressure sensors; 22.1, 22.2, 22.3, 22.4 - spiral preloading structures; 23 - tapered roller bearing; 24 - torque measurement concave part; 25 - horizontal threaded channel; 26 - hollow screw bolt with rotating top; 27 - return spring; 28 - shear pushing motor; 29 - horizontal load sensor; 30 - horizontal displacement sensor; 31 - electronically controlled loading frame; 32 - vertical load sensor; 33 - vertical displacement sensor; 34 - computer terminal. Detailed implementation manners

[0043] The present invention will be described in detail below in conjunction with the various embodiments shown in the drawings. It should be noted, however, that these embodiments are not intended to limit the present invention. Any equivalent transformation or substitution in terms of function, method, or structure made by those of ordinary skill in the art based on these embodiments shall fall within the protection scope of the present invention.

[0044] Please refer to Figures 1 to 7 , this embodiment provides a multi-angle shear test device for the rough interface between soil and structure, including a shear box 1, a loading system 2, and a data collector 3; the specific structure is as follows:

[0045] The shear box 1 includes an upper shear box 1.1 and a lower shear box 1.2; the inner cavity of the upper shear box 1.1 is provided with a pressure transmission plate 4, a permeable stone 5, a filter paper 6 and a shear specimen 7 arranged in sequence from top to bottom for transmitting the load of the electric control loading frame 31. The inner cavity of the lower shear box 1.2 is provided with a serrated shear surface module 9, an angle control component 10 and a limit torque measurement component 11 arranged in sequence from top to bottom. The serrated shear surface module 9, the angle control component 10 and the limit torque measurement component 11 are made of corrosion-resistant materials, preferably stainless steel. The upper surface of the serrated shear surface module 9 is provided with a serrated pattern 13 representing the interface roughness, and the lower surface of the serrated shear surface module 9 is provided with a guide rib 14. The upper surface of the serrated shear surface module 9 is in close contact with the lower surface of the shear specimen 7. The rotation angle control component 10 includes a circular cake structure 15, a suspended truncated cone 17 and a torsion-blocking fan ring 18. The upper surface of the circular cake structure 15 is provided with a plurality of deflection angle guide grooves 16 passing through its geometric center. The suspended truncated cone 17 and the torsion-blocking fan ring 18 are arranged at the bottom of the circular cake structure 15. The center of the suspended truncated cone 17 coincides with the center of the lower surface of the rotation angle control component 10. There are two torsion-blocking fan rings 18, which are symmetrically arranged on both sides of the suspended truncated cone 17. Two torsion-blocking fan rings 18 are arranged in this structural setting, which can prevent the eccentricity and tilting of the shearing sample 7 during the shearing process, and ensure the accuracy of the torque test. The limit torque measurement component 11 is arranged in the base of the lower shear box 1.2, including a truncated cone limiting groove 19, a fan ring limiting groove 20, four micro pressure sensors 21.1, 21.2, 21.3, 21.4, four spiral preloading structures 22.1, 22.2, 22.3, 22.4 and a tapered roller bearing 23. The truncated cone limiting groove 19 and the fan ring limiting groove 20 are recessed downward from the upper surface of the base of the lower shear box 1.2, and the center of the truncated cone limiting groove 19 coincides with the center of the base of the lower shear box 1.2. The tapered roller bearing 23 is arranged in the truncated cone limiting groove 19. There are two fan ring limiting grooves 20, which are symmetrically arranged on both sides of the truncated cone limiting groove 19. The two ends (end faces at both ends in the length direction) of each fan ring limiting groove 20 are provided with a torsion measuring recess 24. A horizontal threaded channel 25 penetrating the side wall of the lower shear box 1.2 is vertically arranged on the side wall of the torsion measuring recess 24; four micro pressure sensors 21.1, 21.2, 21.3, and 21.4 are respectively placed in the corresponding torsion measuring recess 24; four spiral preloading structures 22.1, 22.2, 22.3, and 22.4 are respectively arranged in the corresponding horizontal threaded channels 25, and each spiral preloading structure is composed of a hollow top screw 26 and a reset spring 27. The top of the hollow top screw 27 is provided with a receiving groove, one end of the reset spring 27 is arranged in the receiving groove, and the other end is used to connect with the micro pressure sensor. The suspended truncated cone 17 is built into the cavity in the middle of the tapered roller bearing 23 and is in close contact.The loading system 2 includes a horizontal loading system 2.1 and a vertical loading system 2.2. The horizontal loading system 2.1 includes a shear pushing motor 28, a horizontal load sensor 29, and a horizontal displacement sensor 30. The top end of the horizontal push rod of the shear pushing motor 28 contacts the lower shear box 1.2 and is used to push the lower shear box 1.2 to move horizontally for shearing. The horizontal load sensor 29 is arranged on the front side in the advancing direction of the upper shear box 1.1 and is used to test the shear stress during the shearing process. The horizontal displacement sensor 30 is used to measure the shear displacement of the lower shear box 1.2. The vertical loading system 2.2 includes an electronically controlled loading frame 31, a vertical load sensor 32, and a vertical displacement sensor 33. The electronically controlled loading frame 31 applies a vertical pressure to the load transfer plate 4 through its force transfer rod, and uses the vertical load sensor 32 to control the value of the vertical pressure. The vertical displacement sensor 33 is used to measure the normal displacement of the load transfer plate 4 during the application of the vertical pressure and the shearing process. The data acquisition instrument 3 is connected to the loading system 2 and transmits the data monitored by each sensor to the computer terminal 34.

[0046] In a specific embodiment, the inner cavity cross-sections of the upper shear box 1.1 and the lower shear box 1.2 are both circular. The upper shear box 1.1 and the lower shear box 1.2 can be fixed by fixing pins 8 to ensure the alignment of their inner cavities. A directional wheel track 12 is provided at the bottom of the lower shear box 1.2 to ensure that the lower shear box 1.2 is stuck on the directional wheel track 12 and always moves along the shearing direction. The vertices of the serrated patterns 13 of the serrated shear surface module 9 are flush with the interface between the upper shear box 1.1 and the lower shear box 1.2 to ensure that the shear surface occurs at the vertices of the serrated patterns 13.

[0047] In a specific embodiment, the torsion-resistant fan ring 18 and the floating frustum 17 are respectively embedded in the fan ring limiting groove 20 and the frustum limiting groove 19 to ensure that the center of the rotation angle control assembly 10 always coincides with the center of the inner cavity of the lower shear box 1.2. The tapered roller bearing 23 is arranged between the floating frustum 17 and the frustum limiting groove 19. The inner rollers of the tapered roller bearing 23 can convert the sliding friction between the floating frustum 17 and the frustum limiting groove 19 into rolling friction, reducing the influence on the torsion during the shearing process. Preferably, the gaps between the bottom surfaces of the tapered roller bearing 23 and the floating frustum 17 and the bottom surface of the frustum limiting groove 19 are both not less than 0.3 mm; the gap between the bottom surface of the round cake structure 15 of the rotation angle control assembly 10 and the top surface of the base of the lower shear box 1.2 is not less than 0.5 mm to eliminate the torque loss caused by the contact friction between the rotation angle control assembly 10 and the bottom of the lower shear box 1.2.

[0048] In a specific embodiment, the serrated shear surface module 9 is a series of test pieces, and the specific serrated shear surface module 9 can be selected according to the requirements of the shear test. The serration patterns 13 between a series of serrated shear surface modules 9 are set as undulating patterns with different combinations of tooth depths, pitches, widths, and chamfers. During the test, different interface roughnesses can be simulated by selecting serrated shear surface modules 9 with different undulating patterns. Among them, there is one guiding rib 14 below the serrated shear surface module 13, and the length direction of the guiding rib 14 is consistent with the trend of the serration pattern 13. The guiding rib 14 is engaged with different deflection angle guiding grooves 16 to achieve various angle settings between the trend of the serration pattern 13 on the serrated shear surface module 9 and the shear direction, so as to simulate the inclination angles of various interface rough patterns existing in actual engineering. The symmetry axes of the through-torsion-blocking fan ring 18 and the floating round platform 17 are perpendicular to the shear direction. By fitting the torsion-blocking fan ring 18 with the fan ring limit groove 20, the rotation of the rotation angle control component 10 is restricted, and then the rotation of the serrated shear surface module 9 during the shear process is restricted, ensuring that the trend of the serration pattern 13 remains unchanged during the shear process. Specifically, the guiding rib 14 in this structural setting has the following functions: (1) Controlling the angle function: Different angle settings are achieved by engaging with the deflection angle guiding groove 16 on the rotation angle control module 10; (2) Playing a limiting role: Ensuring that the serrated shear module 9 does not rotate during the shear process, and then the angle remains unchanged, and the test results are not distorted; (3) Transmitting the torsion function: Transmitting the torsion generated by the shear to the rotation angle control module 10, and then transmitting it to and measuring the pressure change through the micro pressure sensor of the limit torque measuring component 11 and calculating the torque.

[0049] In a specific embodiment, after the serrated shear surface module 9 and the rotation angle control component 10 are assembled, they do not contact the inner cavity side wall of the lower shear box 1.2 to avoid torque loss caused by contact friction. The rotation angle control component 10 only contacts the four micro pressure sensors 21.1, 21.2, 21.3, 21.4 and the tapered roller bearing 23 through the torsion-blocking fan ring 18 and the floating round platform 17 respectively, so that the torsion force generated during the shear process is all measured by the four micro pressure sensors 21.1, 21.2, 21.3, 21.4 through the torsion-blocking fan ring 18. Lubricants are applied to the inner cavity side walls and the interface of the upper shear box 1.1 and the lower shear box 1.2, which will further reduce the influence of contact friction on the shear stress and torque.

[0050] In a specific embodiment, four micro pressure sensors 21.1, 21.2, 21.3, and 21.4 are respectively placed at the tops of four spiral preloading structures 22.1, 22.2, 22.3, and 22.4, and are connected by a return spring 27. The wires of the micro pressure sensors 21.1, 21.2, 21.3, and 21.4 are led out through the hollow inner core channel of the hollow screw 26 and connected to the corresponding channels on the data acquisition instrument 3; by screwing in or out the hollow screw 26 and adjusting the pushing of the return spring 27 against the micro pressure sensors 21.1, 21.2, 21.3, and 21.4, they are made to protrude slightly from the end side wall of the fan-shaped ring limit groove 20 and be in pressure contact with the top end of the hollow screw 26 and the end of the torsion-resistant fan ring 18. The four micro pressure sensors 21.1, 21.2, 21.3, and 21.4 have the same initial reading, and the initial reading is preferably adjusted to 5 kPa to 10 kPa.

[0051] As Figure 7 shown, nine corresponding channels on the data acquisition instrument 3 are respectively connected to the micro pressure sensors 21.1, 21.2, 21.3, 21.4, the vertical displacement sensor 33, the horizontal displacement sensor 30, the vertical load sensor 32, the horizontal load sensor 29, and the computer terminal 34, so that the test data measured by each sensor is transmitted to the computer terminal 34 through the data acquisition instrument 3.

[0052] When there is an angle between the serrated pattern 13 on the upper surface of the serrated shear module 9 and the shear direction, during the shear process, the shear specimen 7 will generate a torsional effect on the serrated shear module 9. This torsional effect is transmitted to the corner control assembly 10 through the engagement of the guide rib 14 and the deflection angle guide groove 16, and then to the torsion-resistant fan ring 18, and then contact pressure is generated on the four micro pressure sensors. By reading the pressure values of the four micro pressure sensors 21.1, 21.2, 21.3, and 21.4, the torque T can be calculated by the following formula

[0053]

[0054] In the formula, the pressure values P1 and P2 are the readings of the micro pressure sensors 21.1 and 21.2 arranged at both ends of one of the fan-shaped ring limit grooves 20, and the pressure values P3 and P4 are the readings of the micro pressure sensors 21.3 and 21.4 arranged at both ends of the other fan-shaped ring limit groove 20; R is the horizontal distance from the central axis of the fan-shaped ring limit groove 20 to the center of the frustum limit groove 19. When processing the torque data, it is advisable to use a chart with the same horizontal axis as the shear displacement to obtain the torque value and the maximum torque value when the shear stress reaches the maximum value.

[0055] The present invention also provides an operation method for a multi-angle shear test device for the rough interface between soil and structure, including the following steps:

[0056] S1. First, place the lower shear box on the directional wheel rail 12 and fasten it. Remove the debris in the limit torque measurement assembly 11, apply lubricant to the circular truncated cone limit groove 19 and the sector ring limit groove 20, and place the tapered roller bearing 23 in the circular truncated cone limit groove 19. Then, counterclockwise rotate out the hollow screw 26 to stretch the return spring 27, and then pull the micro pressure sensors 21.1, 21.2, 21.3, and 21.4, so that the micro pressure sensors 21.1, 21.2, 21.3, and 21.4 are respectively retracted into the torque measurement concave part 24 on the end side wall of the sector ring limit groove 20 where they are located. Align and embed the floating circular truncated cone 17 and the torque blocking sector ring 18 of the rotation angle control assembly 10 into the cavity in the middle of the tapered roller bearing 23 and the sector ring limit groove 20 respectively. Secondly, according to the included angle between the tooth profile 13 on the sawtooth shear surface module 9 preset for the interface shear test and the shear direction, engage the guiding rib 14 of the sawtooth shear surface module 9 on a certain deflection angle guiding groove 16. Finally, symmetrically rotate the hollow screw 26 clockwise to compress the return spring 27, and then push the micro pressure sensors 21.1, 21.2, 21.3, and 21.4, so that the micro pressure sensors 21.1, 21.2, 21.3, and 21.4 respectively protrude slightly from the end side wall of the sector ring limit groove 20 where they are located, and press against the top end of the hollow screw 26 and the end of the torque blocking sector ring 18 until the four micro pressure sensors 21.1, 21.2, 21.3, and 21.4 have the same initial reading, and the initial reading should preferably be in the range of 5 kPa to 10 kPa.

[0057] S2. Apply lubricant to the upper surface of the lower shear box 1.2, align and place the upper shear box 1.1 on the lower shear box 1.2, insert the fixing pin 8, apply lubricant evenly to the inner walls of the upper and lower shear boxes, and place the casing sleeve with the same inner cavity size as the upper shear box 1.1 on the upper shear box 1.1 to ensure that the inner cavity of the casing is aligned with the inner cavity of the upper shear box 1.1. Weigh the specified mass of soil and pour it into the shear box 1 cavity, and use the T-shaped sample presser matching the casing to compact the soil to the specified height to form the shear sample 7. Then, remove the T-shaped sample presser and the casing in sequence, and place the filter paper 6, the permeable stone 5, and the load transfer plate 4 on the surface of the shear sample 7 in sequence;

[0058] S3. By adjusting the horizontal loading system 2.1, ensure that the rear side in the advancing direction of the lower shear box 1.1 just touches the horizontal push rod of the shear advancing motor 28, and set the readings of the horizontal displacement sensor 30 and the horizontal load sensor 29 to zero. Align the force transfer rod of the electric control loading frame 31 with the central groove 4.1 on the load transfer plate 4, install the vertical displacement sensor 33 and the vertical load sensor 32, and set the readings of the vertical displacement sensor 33 and the vertical load sensor 32 to zero.

[0059] S4. Control the vertical load sensor 32 on the electric control loading frame 31 through the computer terminal 32 to apply the preset vertical pressure or the vertical pressure required by relevant specification standards.

[0060] S5. After applying the vertical pressure, remove the fixing pin 8 and then start shearing, and collect the data of each sensor in real time. Among them, when the reading of the shear stress reaches stability or significantly decreases, it indicates that the shear specimen 7 has been sheared; when the reading of the shear stress continues to increase, the shear displacement should be not less than 6 mm, and record the data of all sensors during the shearing process in real time.

[0061] S5. After the shearing is completed, adjust the reading of the vertical load sensor 32 to zero, remove the vertical pressure, ensure that the force transfer rod of the electric control loading frame 31 is separated from the force transfer plate 4, and sequentially remove the force transfer plate 4, the permeable stone 5 and the upper shear box 1.1, and check the shear morphology of the interface between the shear specimen 7 and the serrated shear surface module 9; counterclockwise rotate the hollow screw jack 26 to make the readings of the micro pressure sensors 21.1, 21.2, 21.3, 21.4 drop to zero; then sequentially disassemble the lower shear box 1.2 and the serrated shear surface module 9, the corner control assembly 10 and the limit torque measurement assembly 11 in its inner cavity, clean and dry each component of the test device, sort out and analyze the test data, and obtain the change curves of the shear stress, normal displacement and torque of the soil-structure interface with the shear displacement.

[0062] S6. Repeat the steps of S1 - S5 to conduct the next group of tests.

[0063] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A soil-structure rough interface multi-angle shear test device, characterized in that: It includes a shear box, a loading system and a data acquisition instrument; the shear box includes an upper shear box and a lower shear box, the inner cavity of the upper shear box is provided with a pressure transmission plate, a permeable stone, filter paper and a shear sample in sequence from top to bottom, the inner cavity of the lower shear box is provided with a serrated shear surface module, an angle control component and a limit torque measurement component in sequence from top to bottom, the upper surface of the serrated shear surface module is provided with serrated patterns for close contact with the lower surface of the shear sample, the lower surface of the serrated shear surface module is provided with guide ribs, the angle control component includes a circular cake structure, a suspended truncated cone and two torsion-resistant fan rings, and a plurality of deflection points passing through its geometric center are provided on the upper surface of the circular cake structure Angle guide groove, the suspended frustum and the anti-torsion fan ring are arranged at the bottom of the circular pancake structure, the center of the suspended frustum coincides with the center of the lower surface of the angle control component, and the two anti-torsion fan rings are symmetrically arranged on both sides of the suspended frustum; the guide ribs are selected to engage with different deflection angle guide grooves to achieve a variety of angle settings between the sawtooth pattern direction and the shear direction on the sawtooth shear surface module; the limit torque measurement component includes a frustum limit groove, a fan ring limit groove, a tapered roller bearing, a micro pressure sensor and a spiral preload structure, the frustum limit groove and the fan ring limit groove are recessed downward from the upper surface of the lower shear box base, and the center of the frustum limit groove is aligned with the The centers of the lower shear box base coincide with each other, and the tapered roller bearing is arranged in the truncated cone limiting groove; there are two fan ring limiting grooves, which are symmetrically arranged on both sides of the truncated cone limiting groove, and each of the two ends of the fan ring limiting groove is respectively provided with a torsion measuring recess, and a horizontal threaded channel that passes through the side wall of the lower shear box is arranged on the side wall of the torsion measuring recess; a micro pressure sensor is correspondingly arranged in each torsion measuring recess; a spiral preloading structure is arranged in each horizontal threaded channel, and the spiral preloading structure includes a hollow screw top screw and a reset spring; each of the micro pressure sensors is correspondingly placed at the top of the corresponding spiral preloading structure, and is connected through the corresponding reset spring The suspended truncated table is built into the cavity in the middle of the tapered roller bearing and is in close contact with the tapered roller bearing; the loading system includes a horizontal loading system and a vertical loading system, the horizontal loading system includes a shear push motor, a horizontal load sensor and a horizontal displacement sensor, the top end of the horizontal push rod of the shear push motor is in contact with the lower shear box; the horizontal load sensor is arranged in front of the propulsion direction of the upper shear box; the vertical loading system includes an electrically controlled loading frame, a vertical load sensor and a vertical displacement sensor; the data acquisition instrument is connected to the loading system to transmit the data obtained by monitoring each sensor to a computer terminal.

2. The shear test device according to claim 1, characterized in that: The inner cavity cross-sections of the upper shear box and the lower shear box are both circular, and the upper shear box and the lower shear box are fixedly connected by a fixing pin; a directional wheel rail is arranged at the bottom of the lower shear box.

3. The shear test device according to claim 1, characterized in that: The apex of the sawtooth pattern of the sawtooth shear surface module is flush with the height of the interface between the upper shear box and the lower shear box.

4. The shear test device according to claim 1, characterized in that: The anti-torsion fan ring and the suspended truncated cone are respectively embedded in the fan ring limiting groove and the truncated cone limiting groove, and the tapered roller bearing is located between the suspended truncated cone and the truncated cone limiting groove; a gap is provided between the bottom surface of the tapered roller bearing, the bottom surface of the suspended truncated cone and the bottom surface of the truncated cone limiting groove; a gap is also provided between the bottom surface of the pancake structure and the top surface of the base of the lower shear box.

5. The shear test device according to claim 1, characterized in that: The sawtooth shear surface module is a series of test pieces, and the sawtooth patterns between a series of sawtooth shear surface modules are arranged as undulating patterns with different tooth depths, tooth pitches, tooth widths, and chamfers combined with each other; by selecting sawtooth shear surface modules with different undulating patterns, simulation of different interface roughnesses can be achieved; there is one guide rib, and the length direction of the guide rib is consistent with the direction of the sawtooth pattern.

6. The shear test device according to claim 1, characterized in that: The symmetry axis passing through the anti-torsion fan ring and the suspended truncated cone is perpendicular to the shear direction.

7. The shear test device according to claim 1, characterized in that: The circumferential sides of the serrated shear surface module and the angle control component are not in contact with the inner cavity side walls of the lower shear box, and the angle control component is in contact with the micro pressure sensor and the tapered roller bearing respectively through the torsion-resistant fan ring and the suspended frustum; lubricant is applied on the inner cavity side walls of the upper shear box and the lower shear box and on the interface between the two.

8. The shear test device according to claim 1, characterized in that: The wire of each micro pressure sensor is led out through the hollow inner core channel of the hollow screw and connected to the corresponding channel on the data acquisition instrument; through the screwing in or out of the hollow screw and the adjustment of the reset spring, the micro pressure sensor is slightly protruded from the end side wall of the fan ring limiting groove, and is in pressure contact with the top of the hollow screw and the end of the torsion-resistant fan ring. The initial reading of the micro pressure sensor is preferably set to 5kPa~10kPa.

9. The shear test device according to claim 1, characterized in that: During the shear test, the pressure values ​​of the four micro pressure sensors are read, and the torque T formed can be calculated by the following formula: In the formula, the pressure values ​​P1 and P2 are the readings of two micro pressure sensors at both ends of one of the fan ring limiting grooves, and the pressure values ​​P3 and P4 are the readings of the micro pressure sensors at both ends of the other fan ring limiting groove; R is the horizontal distance from the central axis of the fan ring limiting groove to the center of the truncated cone limiting groove.

10. A method for operating a shear test device according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. First, place the lower shear box on the directional wheel rail, remove the debris in the limit torque measurement assembly, apply lubricant in the truncated cone limit groove and the fan ring limit groove, and place the tapered roller bearing in the truncated cone limit groove; then, rotate the hollow top screw counterclockwise to retract each micro pressure sensor into the torque measuring recess on the end side wall of the fan ring limit groove where it is located, and embed the suspended truncated cone and the anti-torsion fan ring of the angle control assembly into the cavity in the middle of the tapered roller bearing and the fan ring limit groove respectively; again, according to the angle between the serration trend and the shear direction on the serrated shear surface module preset in the interface shear test, engage the guide rib of the serrated shear surface module on a certain deflection angle guide groove; finally, symmetrically rotate the hollow top screw clockwise to make each micro pressure sensor slightly protrude from the end side wall of the fan ring limit groove where it is located, and make pressure contact with the top of the hollow top screw and the end of the anti-torsion fan ring until the initial readings of all micro pressure sensors are the same; S2. Apply lubricant on the upper surface of the lower shear box, align the upper shear box with the lower shear box, insert the fixing pin, evenly apply lubricant on the inner walls of the upper and lower shear boxes, clamp the casing with the same inner cavity size as the upper shear box on the upper shear box, and ensure that the inner cavity of the casing is aligned with the inner cavity of the upper shear box; weigh the soil of the specified mass, pour it into the inner cavity of the shear box, use the T-type sample press matched with the casing to compact the soil to the specified height to form a shear sample, then remove the T-type sample press and the casing in turn, and place filter paper, permeable stone and pressure transfer plate in turn on the upper surface of the shear sample; S3, adjust the horizontal loading system so that the rear side of the lower shear box in the advancing direction just contacts the horizontal push rod of the shear advancing motor, and set the readings of the horizontal displacement sensor and the horizontal load sensor to zero; Align the force transmission rod of the electric control loading frame with the central groove of the contact pressure transmission plate, install the vertical displacement sensor and the vertical load sensor, and set the readings of the vertical displacement sensor and the vertical load sensor to zero; S4. Control the vertical load sensor on the electronically controlled loading frame through a computer terminal to apply a preset vertical pressure or a vertical pressure required by relevant specifications and standards; S5, after applying vertical pressure, remove the fixing pin and start shearing again, and collect data from each sensor in real time; S5. After the shearing is completed, adjust the vertical load sensor reading to zero, remove the vertical pressure, ensure that the force transmission rod of the electronically controlled loading frame is separated from the pressure transmission plate, remove the pressure transmission plate, the permeable stone and the upper shear box in turn, and check the shear morphology of the interface between the shear specimen and the serrated shear surface module; unscrew the hollow top screw counterclockwise to reduce the reading of each micro pressure sensor to zero; then disassemble the lower shear box and the serrated shear surface module, the angle control component and the limit torque measurement component in its inner cavity in turn, clean and dry the components of the test device, organize and analyze the test data, and obtain the change curves of the shear stress, normal displacement and torque of the soil-structure interface with the shear displacement; S6. Repeat steps S1 to S5 to carry out the next set of tests.

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