Rock-soil body interface torsional shear characteristic and toughness parameter unit body test method and device

Abstract

The invention particularly discloses a rock-soil body interface torsional shear characteristic and toughness parameter unit body test device which comprises a unit body sample blank manufacturing device, a centering device, a special drilling tool, a rib body and a torque load.The rock-soil body interface torsional shear characteristic and toughness parameter unit body test device has the beneficial effects that traditional direct shear / drawing shear is replaced with torsional shear loading; the problem that the interface contact area is reduced in the shearing process is thoroughly solved, it is ensured that the interface contact area of an anchor / pile and a rock-soil body is constant, a pressure water bag is arranged at the top of a test box unit body, the original overlying and confining pressure environment of a stratum is accurately simulated, a test anchor hole / pile hole is directly manufactured through a drilling technology, and the natural roughness characteristic of the hole wall is reserved to the maximum extent; the smooth wall surface limitation of traditional mold pore forming is broken through, the basic toughness concept of the anchor / pile-rock-soil body interface is defined for the first time, the nature of the basic toughness can be quantitatively represented by the robustness of the shear resistance of the interface, a matched toughness testing technology and evaluation method are developed, and a theoretical model and a calculation tool are provided for the toughness design of anchoring engineering and pile foundation engineering.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering, specifically to a unit cell test method and apparatus for the torsional shear characteristics and toughness parameters of a soil-rock interface. Background Technology

[0002] In civil engineering fields such as building construction, highways, railways, water conservancy, hydropower, municipal engineering, port and waterway engineering, and coastal engineering, anchors and piles are widely used as reinforcement components and foundation forms. Among them, the stress-deformation characteristics of the interface between the anchor or pile and the soil are important design calculation parameters for anchoring engineering and pile foundation engineering. How to accurately measure them has always been a key problem of concern in the engineering community.

[0003] As my country incorporates resilient town development into its 2035 long-term planning goals, resilience-based design concepts are gradually entering the field of structural engineering design. The rational evaluation and determination of the resilience parameters (or indices) of structures and their components are fundamental to the resilience design of engineering structures. Therefore, testing and evaluation methods for the resilience parameters (or indices) of structures and components are receiving increasing attention from the industry.

[0004] The concept of resilience first appeared in the field of ecology to evaluate the ability of an ecosystem to resist changes caused by external forces. It has since been extended to various disciplines. In the 1980s, its application expanded to urban planning, leading to basic concepts such as "resilient cities" and "urban resilience." In 2003, the Multidisciplinary Research Center for Earthquake Engineering (MCEER) at the University at Buffalo proposed a conceptual framework for earthquake resilience, defining a resilient system as possessing high reliability, low disaster consequences, and rapid recovery. It uses four indicators to measure system resilience: robustness in responding to disasters, speed of post-disaster repair, availability of resources, and redundancy. my country's "Standard for Evaluation of Seismic Toughness of Buildings GB / T38591-2020" defines seismic toughness as the ability of a building to maintain and restore its original functions after a set-level earthquake. Therefore, system resilience includes two aspects: first, the system's ability to maintain its original functions when responding to disasters, which can be considered as the system's basic resilience (also known as intrinsic resilience or original resilience), and can be measured by the robustness of the original system, that is, by using the system's robustness parameters or indicators to measure the system's basic resilience; second, the system's ability to restore its original functions after a disaster, which can be considered as the system's recovery resilience, and can be evaluated by the speed, availability, and redundancy of the system's post-disaster repair.

[0005] The basic toughness of the interface between anchors or piles and soil and rock mass can be considered as the ability of the interface to maintain its original bearing capacity after shear slippage under the action of catastrophic external factors. Accurately evaluating and measuring the basic toughness parameters or indices (or robustness parameters or indices) of the interface between anchors or piles and soil and rock mass is the core of carrying out the disaster resistance toughness design of anchors or piles. However, at present, the testing technology and evaluation methods for the basic toughness parameters (or indices) of the interface between anchors or piles and soil and rock mass are still lacking at home and abroad.

[0006] Therefore, proposing an indoor unit cell testing technique or evaluation method for the basic toughness parameters or indices of the interface between anchors or piles and soil and rock is of great theoretical and practical significance for promoting the application of toughness design theory in soil and rock anchoring engineering and pile foundation engineering. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a unit cell test method and apparatus for the torsional shear characteristics and toughness parameters of soil-rock interfaces. This invention is achieved through the following technical solutions.

[0008] A unit cell test method and apparatus for the torsional shear characteristics and toughness parameters of a soil-rock interface, and an indoor testing apparatus for the torsional shear characteristics and toughness parameters of a soil-rock interface, comprising a unit cell sample preparation device, a centering device, a special drilling tool, a reinforcing rib, and a torque loader. The unit cell sample preparation device includes a test box, a top plate, a pressure cap, a silicone membrane, and a water bladder. The centering device includes a centering bracket and a centering guide tube. The special drilling tool includes a power head, a drill rod, and a drill bit. The reinforcing rib includes a rib head and a rib body. The output end of the torque loader is fixedly connected to a clamp. The torque loader is equipped with torque and torsional angle sensors.

[0009] As a further embodiment of the present invention, the upper end of the test box has an open structure, the top plate is connected to the upper end of the test box by bolts, through holes are provided on both the left and right sides of the test box, and gaskets are provided inside the through holes. The pressure caps are respectively provided on the outside of the corresponding through holes and are connected to the test box by bolts. The water bladder is located inside the test box at the lower end of the top plate, and a water pipe is fixedly connected to the water bladder. The inner wall of the test box is provided with a silicone membrane.

[0010] As a further embodiment of the present invention, the pressure caps on both sides are replaced with a bottom cover and a protective sleeve, respectively. The bottom cover and the protective sleeve are bolted to the test box. The centering bracket is bolted to one side of the test box. The centering guide tube is fixedly connected to the centering bracket. The drill bit is threaded to the drill rod. The drill rod is inserted into the centering guide tube. The power head is used to drive the drill rod to rotate. The rib head is a hollow square column, and the rib body is a hollow cylinder. Four longitudinal ribs are evenly distributed around the rib body, and the bottom of the longitudinal ribs is 1cm-2cm higher than the rib body.

[0011] The indoor testing device for the torsional shear characteristics and toughness parameters of the soil-rock interface includes the following methods:

[0012] S1. Use a unit sample preparation device to prepare soil or rock simulation materials, and compact them in layers to make unit sample blanks;

[0013] S2. Use a centering device and a special drilling tool to drill inside the unit blank to form anchor holes or pile holes;

[0014] S3. Grout is injected into the anchor holes or pile holes inside the unit sample blank through reinforcement, bottom cover and casing and cured to harden into anchor body or pile body, and finally form unit sample for rock-soil interface torsional shear test.

[0015] S4. Use a torque loader to perform a torsion shear test on the anchor body or pile body in the unit sample.

[0016] S5. Based on the results of the torsion-shear test, plot the torque-torsion angle and shear stress-shear displacement curves of the interface to obtain the peak value, residual shear strength value and residual peak ratio of the interface.

[0017] S6. Based on the full-process curve obtained above, calculate the basic toughness parameters of the shear resistance of the anchor body or pile body at the interface with the soil and rock mass.

[0018] As a further aspect of the present invention, the specific steps of step S1 are as follows:

[0019] S11. Determine the unit blank size according to the test requirements: the thickness of the unit blank t = 10cm-20cm, the height h = 20cm-50cm, and the width b = 20cm-50cm. Customize the unit blank manufacturing device according to the unit blank size, and then assemble the unit blank manufacturing device.

[0020] S12. The soil used in the test or the rock simulation material prepared according to the physical and mechanical properties of the original rock is filled into the test box through the opening at the top of the box in layers, and the layers are evenly compacted to form a unit sample blank. The thickness of each layer of filling material is 5cm-10cm.

[0021] S13. Apply ground pressure to the top of the unit sample blank. The magnitude of the ground pressure is determined by calculation based on the actual burial depth of the soil and rock mass. The ground pressure is applied and maintained by an external pressure pump pumped to the water bag through a water pipe.

[0022] As a further aspect of the present invention, the specific steps of step S2 are as follows:

[0023] S21. Remove the pressure caps on both sides of the test box, prepare the centering device and special drilling tool, ensure that the equipment is complete and check its condition;

[0024] S22. Securely connect the bottom of the centering bracket to the through hole on one side of the sample box with bolts, and confirm that the connection is secure;

[0025] S23. Assemble special drilling tools: Select the drill bit according to the required anchor hole or pile hole diameter d. The value of the anchor hole or pile hole diameter d generally needs to meet h / d=5-10 and b / d=5-10. Connect the drill bit to the drill rod with threads and ensure that the axes of the drill bit and the drill rod are consistent.

[0026] S24. Pass the drill rod through the centering guide tube, check the overall verticality and stability of the special drilling tool, start the power head to drive the special drilling tool to rotate, control the special drilling tool to drill into the unit sample blank, guide the drill rod and drill bit along the centering guide tube, and ensure that it remains vertical throughout the drilling process until the anchor hole or pile hole is formed.

[0027] As a further aspect of the present invention, the specific steps of step S3 are as follows:

[0028] S31. Use bolts to install the bottom cover and protective sleeve onto the through holes on both sides of the sample box, and place a rubber sealing gasket in the middle.

[0029] S32. Insert reinforcement bars into anchor holes or pile holes;

[0030] S33. Use a long-nozzle funnel to inject grout into the anchor hole or pile hole through the cavity in the middle of the reinforcement. The grout used is self-compacting concrete grout.

[0031] S34. After grouting, the sample is generally cured indoors at normal temperature and pressure for 14 or 28 days to allow the grout injected into the anchor hole or pile hole to harden to a sufficient strength to form the anchor body or pile body.

[0032] As a further aspect of the present invention, the specific steps of step S4 are as follows:

[0033] S41. Fix the protruding part of the anchor body or pile body into the clamp of the torque loader;

[0034] S42. A torque loader is used to apply torque to the anchor body or pile body via a clamp to conduct a torsion-shear test. The loading method adopts the torsion-shear angle control method. The torque and torsion angle sensors of the torque loader are used to record the torsion-shear angle and its corresponding torque in real time. The loading speed of the torsion-shear test is generally controlled between 0.5° / min and 5° / min.

[0035] As a further aspect of the present invention, the specific steps of step S5 are as follows:

[0036] S51. Based on the results of the torsion shear test, plot the torque M-torsion angle θ curve of the entire process at the interface between the anchor body or pile body and the soil and rock.

[0037] S52. From the torque M-torsion angle θ full-process curve, plot the shear stress τ-shear displacement s full-process curve at the interface between the anchor body or pile and the soil / rock mass, and convert it according to the following formula:

[0038]

[0039] In the formula, M and θ are the torque and corresponding torsional angle acting on the anchor body or pile, respectively; τ and s are the shear stress and corresponding shear displacement acting on the interface between the anchor body or pile and the soil and rock, respectively; d is the diameter of the anchor body or pile; and t is the bonding length between the anchor body or pile and the rock mass of the unit sample blank, i.e. the thickness of the unit sample blank.

[0040] S53. Based on the shear stress τ-shear displacement s curve of the interface between the anchor body or pile and the soil obtained by the above conversion, the peak shear strength value τ of the interface can be determined. u and its corresponding shear displacement value s u and the residual shear strength value τ r and its corresponding shear displacement value s r Therefore, the residual peak ratio R can be calculated using the following formula. τ value:

[0041]

[0042] Alternatively, the peak torsional shear strength M at the interface between the anchor body or pile and the soil / rock mass can be determined based on the torque M-rotation angle θ curve obtained above. u and its corresponding shear displacement value θ u and residual shear strength value M r and its corresponding shear displacement value θ r Therefore, the residual peak ratio R can be calculated using the following formula. M value:

[0043]

[0044] As a further aspect of the present invention, step S6 specifically comprises the following steps:

[0045] S61. Determine the basic toughness parameters of the shear resistance of the anchor body or pile body at the interface with the soil and rock mass.

[0046] S62. Based on the shear stress τ-shear displacement s curve of the interface between the anchor body or pile and the soil obtained by the above conversion, the basic toughness parameter RI of the shear resistance of the interface between the anchor body or pile and the soil is calculated by the following formula. τ :

[0047]

[0048] In the formula, RI τTo evaluate the basic toughness parameters of the tensile shear properties of the anchor body or pile body at the interface with the soil and rock mass, RI τ The value is between 0 and 1, RI τ The higher the value, the better the toughness. ABDE S ABCE Let be the area enclosed by the interval from the peak shear strength displacement point A to the residual shear strength displacement point E on the s-axis, the entire τ-s curve, and the horizontal line representing the peak shear strength, respectively. Q(s) is the post-peak shear strength performance function of the anchor body or pile body at the interface with the soil and rock mass. τ u s u These are the peak shear strength values ​​at the interface between the anchor body or pile and the soil / rock mass, and their corresponding shear displacements; s r The residual shear strength value of the anchor body or pile body at the interface with the soil and rock mass and its corresponding shear displacement are taken as s. r =λπd, where d is the diameter of the pile or anchor body, λ is the residual shear displacement coefficient at the interface, and λ = 0.2-0.5.

[0049] Alternatively, based on the torque M-rotation angle θ curve of the anchor body or pile body at the interface with the soil and rock obtained from the experiment, the basic toughness parameter RI of the torsional shear performance of the anchor body or pile body at the interface with the soil and rock can be calculated using the following formula. M :

[0050]

[0051] In the formula, RI M To evaluate the basic toughness parameters of the torsional shear resistance of the anchor body or pile body at the interface with the soil and rock mass, RI M The value is between 0 and 1, RI M The higher the value, the better the toughness. ABDE S ABCE Let M be the area enclosed by the interval from the peak torsional shear strength corner point A to the residual torsional shear strength corner point E on the θ coordinate axis, the entire process curve of M-angle θ, and the horizontal line of peak torsional shear strength; u θ u These are the peak torsional shear strength values ​​at the interface between the anchor body or pile and the soil / rock mass, and their corresponding rotation angles, θ. r The residual torsional shear strength at the interface between the anchor body or pile and the soil / rock mass, and its corresponding rotation angle, are taken as θ. r =λπ, where λ is the residual torsional shear angle coefficient at the interface, λ = 0.2-0.5.

[0052] The beneficial effects of this invention are as follows:

[0053] 1. The torsional shear loading method is adopted instead of the traditional direct shear or pull-out shear method, which solves the problem of the interface contact area becoming smaller during the traditional direct shear or pull-out test. This ensures that the interface contact area between the anchor or pile and the soil remains unchanged during shear loading. At the same time, the torsional shear angle control method (also known as the shear displacement control method) is used to implement the loading, and the measured shear stress τ-shear displacement s curve of the pile-soil interface is more accurate and reliable, especially the post-peak part of the curve is more stable.

[0054] 2. A pressure water bladder is placed on top of the unit sample in the test box to simulate the overburden or surrounding pressure of the strata. This ensures that the unit sample is always in the original stress state in the actual project during the construction of the anchor hole or pile hole and during the test.

[0055] 3. Using drilling to create anchor holes or pile holes can simulate the roughness of the actual anchor holes or pile holes to the greatest extent.

[0056] 4. The concept of basic toughness of the interface between anchor or pile and soil / rock mass is defined for the first time, and it is pointed out that it can be measured by the robustness of the interface shear performance. At the same time, the test technology and evaluation method of basic toughness of the interface between anchor or pile and soil / rock mass are proposed, which can provide a theoretical basis and calculation method for the toughness design of anchoring engineering and pile foundation engineering. Attached Figure Description

[0057] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of the process described in this invention;

[0059] Figure 2 This is a schematic diagram of the layered compaction process used to fabricate the unit sample blank according to the present invention;

[0060] Figure 3 This is a schematic diagram illustrating the use of a centering device to drill anchor holes or pile holes using a special drilling tool, as described in this invention.

[0061] Figure 4 This is a schematic diagram of the grouting and curing process described in this invention;

[0062] Figure 5 This is a schematic diagram of the torsion-shear testing device described in this invention;

[0063] Figure 6 This is a schematic diagram of the torque M-rotation angle θ curve at the pile-soil interface described in this invention.

[0064] Figure 7 This is a schematic diagram of the shear stress τ-shear displacement s curve at the interface between the pile and the soil as described in this invention.

[0065] Figure 8 This is a schematic diagram of the torque M-rotation angle θ curve at the interface between the anchor body and the rock mass as described in this invention.

[0066] Figure 9 This is a schematic diagram of the entire process curve of shear stress τ-shear displacement s at the interface between the anchor body and the rock mass as described in this invention.

[0067] The attached figures are labeled as follows:

[0068] 1. Test box; 2. Top plate 2; 3. Water bladder; 4. Pressure cap; 5. Washer; 6. Silicone membrane; 7. Centering bracket; 8. Centering guide tube; 9. Drill rod; 10. Power head; 11. Drill bit; 12. Bottom cover; 13. Casing; 14. Rib; 15. Rib head; 16. Rib body; 17. Longitudinal rib; 18. Torque loader; 19. Fixture. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] like Figure 1-9 As shown, the present invention has the following two specific embodiments.

[0071] Example 1

[0072] This embodiment aims to provide a simple, practical, engineering-appropriate, efficient, and reliable indoor unit cell testing method and apparatus for the stress-deformation characteristics and basic toughness parameters of the pile-soil interface.

[0073] To achieve the above objectives, this embodiment discloses an indoor testing device for the torsional shear characteristics and toughness parameters of soil interfaces, including a unit sample preparation device, a centering device, a special drilling tool, a reinforcement 14, and a torque loader 18. The unit sample preparation device includes a test box 1, a top plate 2, a pressure cap 4, a silicone membrane 6, and a water bladder 3. The centering device includes a centering bracket 7 and a centering guide tube 8. The special drilling tool includes a power head 10, a drill rod 9, and a drill bit 11. The reinforcement 14 includes a reinforcement head 15 and a reinforcement body. The output end of the torque loader 18 is fixedly connected to a clamp 19, and the torque loader 18 is equipped with torque and torsional angle sensors.

[0074] The upper part of the test box 1 is an open structure. The top plate 2 is connected to the upper part of the test box 1 by bolts. The test box 1 has through holes on both the left and right sides. Gaskets 5 are installed inside the through holes. The pressure caps 4 are respectively installed on the outside of the corresponding through holes and are connected to the test box 1 by bolts. The water bladder 3 is installed inside the test box 1 at the lower end of the top plate 2. A water pipe is fixedly connected to the water bladder 3. The inner wall of the test box 1 is provided with a silicone membrane 6.

[0075] The pressure caps 4 on both sides are replaced with bottom caps 12 and protective sleeves 13 respectively. Bottom caps 12 and protective sleeves 13 are bolted to test box 1. Centering bracket 7 is bolted to one side of test box 1. Centering guide tube 8 is fixedly connected to centering bracket 7. Drill bit 11 is threaded to drill rod 9. Drill rod 9 is inserted into centering guide tube 8. Power head 10 is used to drive drill rod 9 to rotate. Rib head 15 is a hollow square column. Rib body is a hollow cylinder. Four longitudinal ribs are evenly distributed around the rib body. The bottom of the longitudinal ribs is 1cm-2cm higher than the rib body.

[0076] Based on the above apparatus, the following testing methods are included:

[0077] Step 1: Prepare soil simulation materials, and compact them in layers to create unit sample blanks (see attached). Figure 2 The unit blanks used for the test samples are fabricated using a unit blank fabrication device. The unit blank fabrication steps include:

[0078] 1. Determine the dimensions of the unit sample blank according to the test requirements. Generally, the thickness of the unit sample blank is t = 10cm~20cm, the height is h = 20cm~50cm, and the width is b = 20cm~50cm. In this example, the thickness t is taken as 12cm, the height is taken as 40cm, and the width is taken as 40cm. The unit sample blank manufacturing device is customized according to the dimensions of the unit sample blank.

[0079] 2. First, fill the soil material used in the test into test box 1 in layers, and compact the layers evenly to form a unit sample blank. Generally, the thickness of each layer of filling material is 5cm to 10cm. In this example, the thickness of each layer of filling material is 8cm.

[0080] 3. Apply lateral pressure to the top of the unit sample. The magnitude of this pressure is determined based on the actual soil depth. In this example, the soil depth around the pile segment unit tested is H = 10m, and the unit weight of the soil is γ = 18.5kN / m³. 3 The formula for calculating the lateral pressure p of the formation is p = k0γ·H, where k0 is the lateral pressure coefficient. Taking k0 = 0.5, the lateral pressure p around the pile segment unit can be calculated as p = 0.5 × 18.5 × 10 = 92.5 kPa. The lateral pressure is applied and maintained by an external pressure pump pumped to the water bag 3 through a water pipe.

[0081] In this test chamber 1, a pressure water bladder 3 is set on the top of the unit sample. By applying and maintaining the ground pressure to the water bladder 3, it is possible to ensure that the soil in the unit sample is uniformly consolidated under the original stress, and also to avoid the unloading effect that occurs when sampling in the traditional way.

[0082] The second step involves using a centering device and a specially designed drilling tool to drill a pile hole (see attached). Figure 3 The pile holes in the unit sample blank are formed by drilling with a special drilling tool that passes through the centering device;

[0083] 1. Prepare the centering device and special drilling tools, ensure that the equipment is complete and check its condition;

[0084] 2. Securely connect the bottom of the centering bracket 7 to the sample box using bolts, and confirm that the connection is stable;

[0085] 3. Assemble the special drilling tool: Select drill bit 11 according to the required pile hole diameter d. The pile hole diameter d generally needs to meet h / d = 5~10 and b / d = 5~10. In this example, the pile hole diameter d is 8cm, so h / d = 5 and b / d = 5, which meets the requirements. Connect drill bit 11 to drill rod 9 with threads, and ensure that the axes of drill bit 11 and drill rod 9 are aligned.

[0086] 4. Pass the drill rod 9 through the centering guide tube 8, check the overall verticality and stability of the drilling tool, start the power head 10, control the special drilling tool to drill into the unit sample blank, guide the drill rod 9 and drill bit 11 along the centering guide tube 8, and ensure that the drill remains vertical throughout the drilling process until the pile hole is formed.

[0087] In test box 1, a pressure water bladder 3 is set on the top of the unit sample blank to simulate the formation pressure, which can ensure that the sample is always in a real stress state during the pile hole making process. The pile hole is made by drilling, which can simulate the roughness of the actual pile hole wall to the maximum extent.

[0088] The third step involves injecting grout and curing it to harden the pile body. (See attached...) Figure 4 Before constructing the pile body, the pile hole should be inspected, and loose soil on the hole wall should be removed to ensure that the hole wall is intact and undamaged. The pile body construction steps include:

[0089] 1. Use bolts to install the bottom cover 12 and the protective sleeve 13 onto the sample box, and place a rubber sealing gasket in the middle;

[0090] 2. Insert a steel reinforcement 14 into the pile hole. The reinforcement 14 includes a reinforcement head 15, a reinforcement body and longitudinal ribs. The reinforcement head 15 is a hollow square column, the reinforcement body is a hollow round column, and four longitudinal ribs are evenly distributed around the reinforcement body. The bottom of the longitudinal ribs is 2cm higher than the reinforcement body.

[0091] 3. Use a long-nozzle funnel to inject grout into the pile hole through the middle cavity of the reinforcement 14. The grout can be prepared according to the actual anchor grout of the project, or self-compacting concrete grout can be used. In this example, self-compacting concrete grout is selected to grout the pile hole.

[0092] 4. After grouting, the sample is cured indoors at normal temperature and pressure for 14 days to allow the grout injected into the pile hole to harden to a sufficient strength to form a pile.

[0093] Step 4: Torsion-shear test (with appendix) Figure 5 The torsional shear test of the pile is conducted using a torque loader 18, and the test procedure includes:

[0094] 1. Fix the protruding part of the pile body into the clamp 19 in the torque loader 18;

[0095] 2. A torsion-shear test is conducted by applying torque to the pile body using a torque loader 18 via a clamp 19. The loading method adopts the torsion-shear angle control method (also known as the shear displacement control method). The torque and torsion angle sensors in the torque loader 18 are used to record the torsion-shear angle and its corresponding torque in real time. The loading speed of the torque loader 18 is generally controlled between 0.5° / min and 5° / min. In this example, a loading speed of 1.43° / min is selected.

[0096] Among them, the torsional shear loading method is used instead of the traditional direct shear or pull-out shear method, which solves the problem of the interface contact area becoming smaller during the traditional direct shear or pull-out test. This ensures that the interface contact area between the pile and the soil remains unchanged during the shear loading process. At the same time, the torsional shear angle control method (also known as the shear displacement control method) is used to implement the loading, and the measured interface shear stress-shear displacement curve is more accurate and reliable, especially the part after the peak of the curve is more stable.

[0097] Step 5: Plot the torque M-torsion angle θ and shear stress τ-shear displacement curves of the interface throughout the entire process to obtain the peak value, residual shear strength, and residual-peak ratio of the interface. Specific steps include:

[0098] 1. Based on the results of the torsional shear test, plot the torque M-torsion angle θ curve of the pile-soil interface throughout the entire process (see attached diagram). Figure 6 );

[0099] 2. Using the torque M-torsion angle θ curve for the entire process, calculate and plot the shear stress τ-shear displacement s curve at the pile-soil interface using the following formula (see attached). Figure 7 ):

[0100]

[0101] In the formula, M and θ are the torque (N·mm) and the corresponding torsional angle (°) acting on the pile body, respectively; τ and s are the shear stress (MPa) and the corresponding shear displacement (mm) acting on the interface between the pile body and the soil body, respectively; d is the diameter of the pile body (mm); t is the bonding length between the pile body and the soil of the unit sample blank (mm), that is, the thickness of the unit sample blank;

[0102] 3. Based on the shear stress τ-shear displacement s curve of the pile-soil interface obtained from the above conversion, the peak shear strength τ of the interface can be determined. u =75.6 kPa and its corresponding shear displacement value s u =2.40mm, and residual shear strength value τ r =60.1 kPa and its corresponding shear displacement value s r =50.2mm, therefore the residual peak ratio R can be calculated using the following formula. τ value:

[0103]

[0104] Alternatively, the peak torsional shear strength M at the pile-soil interface can be determined based on the torque M-rotation angle θ curve obtained above. u = 91.2 kN·m and its corresponding shear displacement θ u =3.43°, and the residual shear strength value M r = 72.5 kN·m and its corresponding shear displacement θ r =72°, so the residual peak ratio R can be calculated using the following formula. M value:

[0105]

[0106] Step 6: Determine the basic toughness parameters of the shear resistance at the pile-soil interface (see appendix). Figure 7 Based on the shear stress τ-shear displacement s curve of the pile-soil interface obtained by the above conversion, the basic toughness parameter RI of the pile-soil interface shear resistance is calculated by the following formula. τ :

[0107]

[0108] In the formula, RI τ To evaluate the basic toughness parameters of the shear resistance at the pile-soil interface, RI τ The value is between 0 and 1, RI τ The higher the value, the better the toughness; S ABDE S ABCELet τ be the area enclosed by the interval from the peak shear strength displacement point A to the residual shear strength displacement point E on the s-axis, the entire τ-s curve, and the horizontal line representing the peak shear strength, respectively. u s u These represent the peak shear strength at the pile-soil interface and its corresponding shear displacement; s r Let s be the residual shear strength value at the pile-soil interface and its corresponding shear displacement. r =λπd, where d is the diameter of the pile, λ is the residual shear displacement coefficient at the interface, λ = 0.2 to 0.5, and in this example, λ is taken as 0.2, s r =0.2πd,τ i s i These are the i-th interface shear stress and its corresponding displacement data collected between the peak shear strength displacement point and the residual shear strength displacement point, respectively.

[0109] In this example, the basic toughness parameter RI of the pile-soil interface shear resistance is... τ for:

[0110]

[0111] In addition, the basic toughness parameter RI of the shear performance of the pile-soil interface can also be calculated using the following formula based on the torque M-rotation angle θ curve of the pile-soil interface obtained above. M :

[0112]

[0113] In the formula, RI M To evaluate the basic toughness parameters of the shear resistance at the pile-soil interface, RI M The value is between 0 and 1, RI M The higher the value, the better the toughness; S ABDE S ABCE Let M be the area enclosed by the interval from the peak torsional strength turning point A to the residual torsional strength turning point E on the s-axis, the entire M-θ curve, and the horizontal line representing the peak torsional strength; u θ u These are the peak torsional strength at the pile-soil interface and the corresponding rotation angle in degrees, respectively; θ r Let θ be the residual torsional shear strength at the pile-soil interface and its corresponding rotation angle. r =λπ, where λ is the residual torsional shear angle coefficient at the interface, λ = 0.2 to 0.5, and in this example, λ is taken as 0.2, θ r =0.2π; M i θ i These are the i-th interface torque and its corresponding angle data value collected between the peak torsional strength corner point and the residual torsional strength corner point, respectively.

[0114] In this example, the basic toughness parameter RI for the torsional resistance of the pile-soil interface is... M for:

[0115]

[0116] Example 2

[0117] This embodiment aims to provide a simple, practical, engineering-compliant, efficient, and reliable indoor unit test method and device for the stress-deformation characteristics and basic toughness parameters of the anchor body-rock interface.

[0118] To achieve the above objectives, this embodiment discloses an indoor testing device for rock mass interface torsional shear characteristics and toughness parameters, including a unit sample preparation device, a centering device, a special drilling tool, a reinforcement 14, and a torque loader 18. The unit sample preparation device includes a test box 1, a top plate 2, a pressure cap 4, a silicone membrane 6, and a water bladder 3. The centering device includes a centering bracket 7 and a centering guide tube 8. The special drilling tool includes a power head 10, a drill rod 9, and a drill bit 11. The reinforcement 14 includes a reinforcement head 15 and a reinforcement body. The output end of the torque loader 18 is fixedly connected to a clamp 19, and the torque loader 18 is equipped with torque and torsional angle sensors.

[0119] The upper part of the test box 1 is an open structure. The top plate 2 is connected to the upper part of the test box 1 by bolts. The test box 1 has through holes on both the left and right sides. Gaskets 5 are installed inside the through holes. The pressure caps 4 are respectively installed on the outside of the corresponding through holes and are connected to the test box 1 by bolts. The water bladder 3 is installed inside the test box 1 at the lower end of the top plate 2. A water pipe is fixedly connected to the water bladder 3. The inner wall of the test box 1 is provided with a silicone membrane 6.

[0120] The pressure caps 4 on both sides are replaced with bottom caps 12 and protective sleeves 13 respectively. Bottom caps 12 and protective sleeves 13 are bolted to test box 1. Centering bracket 7 is bolted to one side of test box 1. Centering guide tube 8 is fixedly connected to centering bracket 7. Drill bit 11 is threaded to drill rod 9. Drill rod 9 is inserted into centering guide tube 8. Power head 10 is used to drive drill rod 9 to rotate. Rib head 15 is a hollow square column. Rib body is a hollow cylinder. Four longitudinal ribs are evenly distributed around the rib body. The bottom of the longitudinal ribs is 1cm-2cm higher than the rib body.

[0121] Based on the above apparatus, the following testing methods are included:

[0122] Step 1: Prepare rock simulation materials according to the physical and mechanical properties of the original rock, and then compact them in layers to create unit sample blanks (see attached). Figure 2 The unit blanks used for the test samples are fabricated using a unit blank fabrication device. The unit blank fabrication steps include:

[0123] 1. Determine the dimensions of the unit blank according to the test requirements. Generally, the thickness of the unit blank is t = 10cm~20cm, the height is h = 20cm~50cm, and the width is b = 20cm~50cm. In this example, the thickness t is taken as 10cm, the height is taken as 30cm, and the width is taken as 30cm. The unit blank manufacturing device is customized according to the dimensions of the unit blank.

[0124] 2. First, fill the test box 1 with the rock simulation material used in the test in layers, and compact the layers evenly to form a unit sample blank. Generally, the thickness of each layer of filler is 5cm to 10cm. In this example, the thickness of each layer of filler is 5cm.

[0125] 3. Apply ground pressure to the top of the unit sample. The magnitude of the pressure is determined based on the actual burial depth of the rock mass. In this example, the burial depth of the rock strata surrounding the anchoring section unit sample is H = 5m, and the unit weight of the rock is γ = 23kN / m³. 3 The formula for calculating the overburden pressure p is p = γ·H. Then, the ground pressure around the anchoring unit can be calculated as p = 23 × 5 = 115 kPa. The ground pressure is applied and maintained by an external pressure pump pumped to the water bladder 3 through a water pipe.

[0126] The second step involves using a centering device and a specially designed drilling tool to drill an anchor hole (see attached). Figure 3 The anchor holes in the unit sample blank are formed by drilling through a special drilling tool that passes through the centering device;

[0127] 1. Prepare the centering device and special drilling tools, ensure that the equipment is complete and check its condition;

[0128] 2. Securely connect the bottom of the centering bracket 7 to the sample box using bolts, and confirm that the connection is stable;

[0129] 3. Assemble the special drilling tool: Select drill bit 11 according to the required anchor hole diameter d. The anchor hole diameter d generally needs to meet h / d = 5~10 and b / d = 5~10. In this example, the anchor hole diameter d is 6cm, so h / d = 5 and b / d = 5, which meets the requirements. Connect drill bit 11 to drill rod 9 with threads, and ensure that the axes of drill bit 11 and drill rod 9 are aligned.

[0130] 4. Pass the drill rod 9 through the centering guide tube 8, check the overall verticality and stability of the drill bit, start the power head 10, control the special drill bit to drill into the unit blank, guide the drill rod 9 and drill bit 11 along the centering guide tube 8, and ensure that the drill bit remains vertical throughout the drilling process until the anchor hole is formed.

[0131] The third step is to inject grout and cure it to harden it into an anchor solid (see attached). Figure 4 Before fabricating the anchor body, the anchor hole should be inspected, and any debris on the hole wall should be removed to ensure that the hole wall is intact and undamaged. The anchor body fabrication steps include:

[0132] 1. Use bolts to install the bottom cover 12 and the protective sleeve 13 onto the sample box, and place a rubber sealing gasket in the middle;

[0133] 2. Insert a steel rib 14 into the anchor hole. The rib 14 includes a rib head 15, a rib body, and longitudinal ribs. The rib head 15 is a hollow square column, the rib body is a hollow cylindrical column, and four longitudinal ribs are evenly distributed around the rib body. The bottom of the longitudinal ribs is 2cm higher than the rib body.

[0134] 3. Use a long-nozzle funnel to inject grout into the anchor hole through the middle cavity of the reinforcement 14. The grout can be prepared according to the actual anchor grout of the project, or self-compacting concrete grout can be used. In this example, self-compacting concrete grout is selected to grout the anchor hole.

[0135] 4. After grouting, the sample is generally cured indoors at normal temperature and pressure for 28 days to allow the grout injected into the anchor hole to harden to a sufficient strength to form an anchor body.

[0136] Step 4: Torsion-shear test (with appendix) Figure 5 The anchor's torsion-shear test is conducted using torque loader 18, and the test procedure is as follows:

[0137] 1. Fix the protruding part of the anchor body into the clamp 19 in the torque loader 18;

[0138] 2. A torsion-shear test is conducted by applying torque to the anchor body through the clamp 19 using the torque loader 18. The loading method adopts the torsion-shear angle control method (also known as the shear displacement control method). The torque and torsion angle sensors in the torque loader 18 are used to record the torsion-shear angle and its corresponding torque in real time. The loading speed of the torque loader 18 is generally controlled between 0.5° / min and 5° / min. In this example, the loading speed is 1.91° / min.

[0139] Step 5: Plot the full-process curves of torque M-torsion angle θ and shear stress τ-shear displacement s at the interface to obtain the peak value, residual shear strength, and residual-peak ratio of the interface.

[0140] 1. Based on the results of the torsion-shear test, plot the torque M-torsion angle θ curve of the entire process at the interface between the anchor body and the rock mass (see attached). Figure 8 );

[0141] 2. Using the torque M-torsion angle θ curve for the entire process, the shear stress τ-shear displacement s curve for the interface between the anchor body and the rock mass is calculated and plotted using the following formula (see attached). Figure 9 ):

[0142]

[0143] In the formula, M and θ are the torque (N·mm) and the corresponding torsional angle (°) acting on the anchor body, respectively; τ and s are the shear stress (MPa) and the corresponding shear displacement (mm) acting on the interface between the anchor body and the rock mass, respectively; d is the diameter of the anchor body (mm); t is the bonding length between the anchor body and the rock mass of the unit sample blank, that is, the thickness of the unit sample blank (mm).

[0144] 3. Based on the shear stress τ-shear displacement s curve of the anchor body-rock mass interface obtained from the above conversion, the peak shear strength τ of the interface can be determined. u =649.6 kPa and its corresponding shear displacement value s u =1.5mm, and residual shear strength value τ r =289.7 kPa and its corresponding shear displacement value s r =37.7mm, therefore the residual peak ratio R can be calculated using the following formula. τ value:

[0145]

[0146] Alternatively, the peak torsional shear strength M at the interface between the anchor body and the rock mass can be determined based on the torque M-rotation angle θ curve obtained above. u = 367.3 kN·m and its corresponding shear displacement θ u =2.86°, and residual shear strength value M r =163.8 kN·m and its corresponding shear displacement θ r =72°, so the residual peak ratio R can be calculated using the following formula. M value:

[0147]

[0148] Step 6: Determine the basic toughness parameters of the shear resistance at the interface between the anchor body and the rock mass (see appendix). Figure 7 Based on the shear stress τ-shear displacement s curve of the anchor body-rock mass interface obtained by the above conversion, the basic toughness parameter RI of the shear resistance of the anchor body-rock mass interface is calculated by the following formula. τ :

[0149]

[0150] In the formula, RI τ To evaluate the basic toughness parameters of the shear resistance at the interface between the anchor body and the rock mass, RI τ The value is between 0 and 1, RI τ The higher the value, the better the toughness; S ABDE S ABCELet τ be the area enclosed by the interval from the peak shear strength displacement point A to the residual shear strength displacement point E on the s-axis, the entire τ-s curve, and the horizontal line representing the peak shear strength, respectively; τ u s u These represent the peak shear strength at the interface between the anchor body and the rock mass and its corresponding shear displacement; s r Let s be the residual shear strength value at the interface between the anchor body and the rock mass and its corresponding shear displacement. r =λπd, where d is the diameter of the anchor body, λ is the residual shear displacement coefficient at the interface, λ = 0.2~0.5, and in this example λ is taken as 0.2, s r =0.2πd;τ i s i These are the i-th interface shear stress and its corresponding displacement data collected between the peak shear strength displacement point and the residual shear strength displacement point, respectively.

[0151] In this example, the basic toughness parameter RI of the shear resistance at the interface between the anchor body and the rock mass is... τ for:

[0152]

[0153] In this example, the expression for the curve Q(s) of the shear stress τ-shear displacement s at the interface between the anchor body and the rock mass can also be obtained from the above-mentioned expression. Then, the basic toughness parameter RI of the shear resistance of the interface between the anchor body and the rock mass can be calculated using the following formula. τ :

[0154]

[0155] In the formula, Q(s) is a function of the performance peak at the interface between the anchor body and the rock mass; τ u s u These represent the peak shear strength at the interface between the anchor body and the rock mass and its corresponding shear displacement; s r Let s be the residual shear strength value at the interface between the anchor body and the rock mass and its corresponding shear displacement. r =λπd, where d is the diameter of the anchor body, λ is the residual shear displacement coefficient at the interface, λ = 0.2~0.5, and in this example λ is taken as 0.2, s r =0.2πd.

[0156] In this example, regression analysis of the curve yields Q(s) = 820.5 × e -0.55·s +289.6571, the basic toughness parameter RI of the shear resistance at the interface between the anchor body and the rock mass is:

[0157]

[0158] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A unit cell test device for interfacial torsional shear characteristics and toughness parameters of soil and rock, characterized in that: The device includes a unit sample preparation device, a centering device, a special drilling tool, a rib, and a torque loader. The unit sample preparation device includes a test box, a top plate, a pressure cap, a silicone membrane, and a water bladder. The centering device includes a centering bracket and a centering guide tube. The special drilling tool includes a power head, a drill rod, and a drill bit. The rib includes a rib head and a rib body. The output end of the torque loader is fixedly connected to a clamp. The torque loader is equipped with torque and torsion angle sensors.

2. The unit cell test device for interfacial torsional shear characteristics and toughness parameters of soil and rock mass according to claim 1, characterized in that: The test box has an open structure at the top. The top plate is bolted to the top of the test box. There are through holes on both the left and right sides of the test box. Gaskets are installed inside the through holes. The pressure caps are respectively installed on the outside of the corresponding through holes and are connected to the test box by bolts. The water bladder is installed inside the test box at the lower end of the top plate. A water pipe is fixedly connected to the water bladder. The inner wall of the test box is lined with a silicone membrane.

3. The unit cell test device for interfacial torsional shear characteristics and toughness parameters of soil and rock mass according to claim 2, characterized in that: The pressure caps on both sides are replaced with bottom caps and protective sleeves, respectively. The bottom caps and protective sleeves are bolted to the test box. The centering bracket is bolted to one side of the test box. The centering guide tube is fixedly connected to the centering bracket. The drill bit is threaded to the drill rod. The drill rod is inserted into the centering guide tube. The power head is used to drive the drill rod to rotate. The rib head is a hollow square column. The rib body is a hollow cylinder. Four longitudinal ribs are evenly distributed around the rib body. The bottom of the longitudinal ribs is 1cm-2cm higher than the rib body.

4. The unit cell test apparatus for interfacial torsional shear characteristics and toughness parameters of soil and rock mass according to any one of claims 1-3, characterized in that, The following testing methods are included: S1. Use a unit sample preparation device to prepare soil or rock simulation materials, and compact them in layers to make unit sample blanks; S2. Use a centering device and a special drilling tool to drill inside the unit blank to form anchor holes or pile holes; S3. Grout is injected into the anchor holes or pile holes inside the unit sample blank through reinforcement, bottom cover and casing and cured to harden into anchor body or pile body, and finally form unit sample for rock-soil interface torsional shear test. S4. Use a torque loader to perform a torsion shear test on the anchor body or pile body in the unit sample. S5. Based on the results of the torsion-shear test, plot the torque-torsion angle and shear stress-shear displacement curves of the interface between the anchor body or pile body and the soil and rock mass, and obtain the peak value and residual shear strength value of the interface as well as the residual peak ratio. S6. Based on the full-process curve obtained above, calculate the basic toughness parameters of the shear resistance of the anchor body or pile body at the interface with the soil and rock mass.

5. The method according to claim 4, characterized in that, The specific steps of step S1 are as follows: S11. Determine the unit blank size according to the test requirements: the thickness of the unit blank t = 10cm-20cm, the height h = 20cm-50cm, and the width b = 20cm-50cm. Customize the unit blank manufacturing device according to the unit blank size, and then assemble the unit blank manufacturing device. S12. The soil used in the test or the rock simulation material prepared according to the physical and mechanical properties of the original rock is filled into the test box through the opening at the top of the box in layers, and the layers are evenly compacted to form a unit sample blank. The thickness of each layer of filling material is 5cm-10cm. S13. Apply ground pressure to the top of the unit sample blank. The magnitude of the ground pressure is determined by calculation based on the actual burial depth of the soil and rock mass. The ground pressure is applied and maintained by an external pressure pump pumped to the water bag through a water pipe.

6. The method according to claim 4, characterized in that, The specific steps of step S2 are as follows: S21. Remove the pressure caps on both sides of the test box, prepare the centering device and special drilling tool, ensure that the equipment is complete and check its condition; S22. Securely connect the bottom of the centering bracket to the through hole on one side of the sample box with bolts, and confirm that the connection is secure; S23. Assemble special drilling tools: Select the drill bit according to the required anchor hole or pile hole diameter d. The value of the anchor hole or pile hole diameter d generally needs to meet h / d=5-10 and b / d=5-10. Connect the drill bit to the drill rod with threads and ensure that the axes of the drill bit and the drill rod are consistent. S24. Pass the drill rod through the centering guide tube, check the overall verticality and stability of the special drilling tool, start the power head to drive the special drilling tool to rotate, control the special drilling tool to drill into the unit sample blank, guide the drill rod and drill bit along the centering guide tube, and ensure that it remains vertical throughout the drilling process until the anchor hole or pile hole is formed.

7. The method according to claim 4, characterized in that, The specific steps of step S3 are as follows: S31. Use bolts to install the bottom cover and protective sleeve onto the through holes on both sides of the sample box, and place a rubber sealing gasket in the middle. S32. Insert reinforcement bars into anchor holes or pile holes; S33. Use a long-nozzle funnel to inject grout into the anchor hole or pile hole through the cavity in the middle of the reinforcement. The grout used is self-compacting concrete grout. S34. After grouting, the sample is generally cured indoors at normal temperature and pressure for 14 or 28 days to allow the grout injected into the anchor hole or pile hole to harden to a sufficient strength to form the anchor body or pile body.

8. The method according to claim 4, characterized in that: The specific steps of step S4 are as follows: S41. Fix the protruding part of the anchor body or pile body into the clamp of the torque loader; S42. A torque loader is used to apply torque to the anchor body or pile body via a clamp to conduct a torsion-shear test. The loading method adopts the torsion-shear angle control method. The torque and torsion angle sensors of the torque loader are used to record the torsion-shear angle and its corresponding torque in real time. The loading speed of the torsion-shear test is generally controlled between 0.5° / min and 5° / min.

9. The method according to claim 4, characterized in that: The specific steps of step S5 are as follows: S51. Based on the results of the torsion shear test, plot the torque M-torsion angle θ curve of the entire process at the interface between the anchor body or pile body and the soil and rock. S52. From the torque M-torsion angle θ full-process curve, plot the shear stress τ-shear displacement s full-process curve at the interface between the anchor body or pile and the soil / rock mass, and convert it according to the following formula: In the formula, M and θ are the torque and corresponding torsional angle acting on the anchor body or pile, respectively; τ and s are the shear stress and corresponding shear displacement acting on the interface between the anchor body or pile and the soil and rock, respectively; d is the diameter of the anchor body or pile; and t is the bonding length between the anchor body or pile and the rock mass of the unit sample blank, i.e. the thickness of the unit sample blank. S53. Based on the shear stress τ-shear displacement s curve of the interface between the anchor body or pile and the soil obtained by the above conversion, the peak shear strength value τ of the interface can be determined. u and its corresponding shear displacement value s u and the residual shear strength value τ r and its corresponding shear displacement value s r Therefore, the residual peak ratio R can be calculated using the following formula. τ value: Alternatively, the peak torsional shear strength M at the interface between the anchor body or pile and the soil / rock mass can be determined based on the torque M-rotation angle θ curve obtained above. u and its corresponding shear displacement value θ u and residual shear strength value M r and its corresponding shear displacement value θ r Therefore, the residual peak ratio R can be calculated using the following formula. M value:

10. The method according to claim 4, characterized in that: The specific steps of step S6 are as follows: S61. Determine the basic toughness parameters of the shear resistance of the anchor body or pile body at the interface with the soil and rock mass. S62. Based on the shear stress τ-shear displacement s curve of the interface between the anchor body or pile and the soil obtained by the above conversion, the basic toughness parameter RI of the shear resistance of the interface between the anchor body or pile and the soil is calculated by the following formula. τ : In the formula, RI τ To evaluate the basic toughness parameters of the tensile shear properties of the anchor body or pile body at the interface with the soil and rock mass, RI τ The value is between 0 and 1, RI τ The higher the value, the better the toughness. ABDE S ABCE Let be the area enclosed by the interval from the peak shear strength displacement point A to the residual shear strength displacement point E on the s-axis, the entire τ-s curve, and the horizontal line representing the peak shear strength, respectively. Q(s) is the post-peak shear strength performance function of the anchor body or pile body at the interface with the soil and rock mass. τ u s u These are the peak shear strength values ​​at the interface between the anchor body or pile and the soil / rock mass, and their corresponding shear displacements; s r The residual shear strength value of the anchor body or pile body at the interface with the soil and rock mass and its corresponding shear displacement are taken as s. r =λπd, where d is the diameter of the pile or anchor body, λ is the residual shear displacement coefficient at the interface, and λ = 0.2-0.

5. Alternatively, based on the torque M-rotation angle θ curve of the anchor body or pile body at the interface with the soil and rock obtained from the experiment, the basic toughness parameter RI of the torsional shear performance of the anchor body or pile body at the interface with the soil and rock can be calculated using the following formula. M : In the formula, RI M To evaluate the basic toughness parameters of the torsional shear resistance of the anchor body or pile body at the interface with the soil and rock mass, RI M The value is between 0 and 1, RI M The higher the value, the better the toughness. ABDE S ABCE Let M be the area enclosed by the interval from the peak torsional shear strength corner point A to the residual torsional shear strength corner point E on the θ coordinate axis, the entire process curve of M-angle θ, and the horizontal line of peak torsional shear strength; u θ u These are the peak torsional shear strength values ​​at the interface between the anchor body or pile and the soil / rock mass, and their corresponding rotation angles, θ. r The residual torsional shear strength at the interface between the anchor body or pile and the soil / rock mass, and its corresponding rotation angle, are taken as θ. r =λπ, where λ is the residual torsional shear angle coefficient at the interface, λ = 0.2-0.5.

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