Method and system for identifying cracking stress field tensor of in-situ engineering surrounding rock step-by-step excavation plate

Abstract

The invention relates to the technical field of geotechnical engineering and mining engineering, in particular to a method and a system for identifying in-situ engineering surrounding rock step-by-step excavation plate cracking stress field tensor. A layered sparse modeling method is adopted; in-situ stress and servo keeping are applied through whole-process servo control, tunnel step-by-step excavation unloading is conducted, and the force ratio serves as the balance condition; the measuring range of a measuring circle is automatically generated, the stress tensor is monitored and obtained, and the main stress and the deflection degree are measured according to the length and the direction of a main stress axis. According to the method provided by the invention, microcracks can be generated by adopting a particle flow program leveling joint model, and the limitation that a finite element method cannot directly characterize cracks is overcome. According to the technical scheme, the influence of microcracks caused by step-by-step excavation on the main stress and the deviation is fully considered, the key effect of the size and the direction of the in-situ engineering tunnel step-by-step excavation unloading main stress is fully shown, and an effective method is provided for deeply understanding the in-situ engineering step-by-step excavation surrounding rock fracture mechanism.

Description

Technical Field

[0001] The invention relates to the technical fields of geotechnical engineering and mining engineering, and in particular to a method and system for identifying a tensor of a cracking stress field of a step-by-step excavation plate of surrounding rock in an in-situ engineering project. Background Art

[0002] Plate cracking failure refers to the tensile fracture of hard rock when it is unloaded during excavation. The mechanism behind this failure is similar to the axial splitting observed in laboratory tests of rocks under low confining pressure. However, it is different from the shear failure that occurs under high confining pressure. This phenomenon is difficult to explain using traditional strength theory. Existing simulation studies oversimplify the stress state, excavation path, and step-by-step excavation process, and there is limited research on plate cracking failure during step-by-step tunnel excavation. The stress path near the tunnel face undergoes a complex stress path, including stress increase, decrease, and directional rotation. Existing technologies fail to simulate the changes in the magnitude and direction of the principal stress of plate cracking in step-by-step excavation of surrounding rock in situ engineering.

[0003] The above technology does not take into account the stress path of tunnel excavation unloading, that is, the in-situ stress path "three-dimensional stress state step-by-step excavation". The above technology has the problem of being unable to reproduce the stress tensor evolution process of surrounding rock step-by-step excavation unloading under the in-situ stress path. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the present invention provides a method for identifying the cracking stress field tensor of the surrounding rock of an in-situ engineering project in a step-by-step excavation plate, and realizes the identification and characterization of the cracking stress field tensor of the surrounding rock of an in-situ engineering project in a step-by-step excavation plate through algorithm development.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation slabs, comprising: adopting a layered sparse modeling method;

[0007] Servo control applies in-situ stress to the target value, and static balance is achieved through force ratio;

[0008] Keep the servo state, carry out tunnel excavation and unloading in steps, and use the force ratio after each step of excavation as the end condition;

[0009] The measuring circle determination range is automatically generated to monitor and obtain the stress tensor. The length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection.

[0010] As a preferred scheme of the method for identifying the cracking stress field tensor of the in-situ engineering surrounding rock in step-by-step excavation of the plate described in the present invention, the layered sparse modeling method includes using a particle flow program flat joint model in multiple internal rectangular areas, and the particle diameter increases from the inside to the outside, so that the surrounding rock around the tunnel has sufficient resolution while ensuring the calculation efficiency.

[0011] As a preferred solution of the method for identifying the stress field tensor of the in-situ engineering surrounding rock in step-by-step excavation plate described in the present invention, the in-situ stress includes: σ1=70MPa, σ2=65MPa, σ3=30MPa.

[0012] As a preferred solution of the method for identifying the cracking stress field tensor of the in-situ engineering surrounding rock in step-by-step excavation plate described in the present invention, wherein: the servo control includes implementing the servo control by writing a code, ensuring that the in-situ stress path is the same as the in-situ test, and implementing the excavation by deleting particles in the area;

[0013] The excavation direction is from +X to -X, and the process is divided into stages I-II and III-V.

[0014] As a preferred solution of the method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation plate described in the present invention, wherein: in the I-II stage, true triaxial stress is applied in the model;

[0015] In the III-V stage, the true triaxial stress is maintained and the stress is increased by applying 1.0×10 -5 The force ratio limit maintains static equilibrium.

[0016] As a preferred solution of the method for identifying the cracking stress field tensor of the in-situ engineering surrounding rock in step-by-step excavation plate described in the present invention, the monitoring and acquisition of the stress tensor includes generating a measuring circle using Python language programming and calculating the average tensor of the particles in the measuring circle in three directions.

[0017] As a preferred solution of the method for identifying the stress field tensor of the cracking of the in-situ engineering surrounding rock excavation step by step described in the present invention, the length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection, including that the principal stress axis is symmetrical along the center point of the measuring circle, and half of the principal stress axis is the magnitude of the principal stress. The magnitude of the change in the direction of the principal stress axis after the surrounding rock excavation unloading indicates the degree of principal stress deflection.

[0018] As a preferred solution of the stress field tensor system for identifying cracking of in-situ engineering surrounding rock in step-by-step excavation, the present invention includes: a modeling module, a servo stress control module, a step-by-step excavation unloading module, and a stress tensor monitoring module.

[0019] Modeling module, adopts layered sparse modeling method;

[0020] Servo stress control module, servo control applies in-situ stress to the target value, and static balance is achieved through force ratio;

[0021] The step-by-step excavation and unloading module maintains the servo state and performs step-by-step excavation and unloading of the tunnel. The force ratio after each step of excavation is used as the end condition;

[0022] The stress tensor monitoring module automatically generates the measurement circle measurement range, monitors and obtains the stress tensor. The length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection.

[0023] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of any one of the methods for identifying the cracking stress field tensor of the step-by-step excavation plate of the surrounding rock of an in-situ engineering project are implemented.

[0024] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of any one of the methods for identifying the cracking stress field tensor of the step-by-step excavation plate of the surrounding rock of an in-situ engineering project are implemented.

[0025] Beneficial effects of the present invention: The simulation method proposed in the present invention uses a particle flow program flat joint model to generate microcracks, overcoming the limitation that the finite element method cannot directly characterize ruptures. The technical solution fully considers the influence of microcracks caused by step-by-step excavation on the principal stress and deviation size. As the excavation progresses, the direction and size of the principal stress in the surrounding area have changed considerably, which can cause microscopic damage and form local ruptures near the tunnel. The key role of the size and direction of the principal stress in the step-by-step excavation unloading of the in-situ engineering tunnel can be fully demonstrated, providing an effective method for in-depth understanding of the surrounding rock rupture mechanism of the step-by-step excavation of the in-situ engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0027] Figure 1 A schematic flow chart of a method for identifying the stress field tensor of in-situ engineering surrounding rock during step-by-step excavation of a plate is provided as an embodiment of the present invention.

[0028] Figure 2 A schematic diagram of layered sparse modeling of a particle flow program for a method of identifying the stress field tensor of an in-situ engineering surrounding rock excavation plate in a step-by-step manner is provided as an embodiment of the present invention.

[0029] Figure 3 A schematic diagram of a measuring circle monitoring stress tensor for a method of identifying the stress field tensor of cracking of an in-situ engineering surrounding rock in a step-by-step excavation plate provided by an embodiment of the present invention.

[0030] Figure 4 A schematic diagram of the principal stress deflection results of a step-by-step excavation of a stress field tensor method for identifying cracking of an in-situ engineering surrounding rock during step-by-step excavation is provided as an embodiment of the present invention: (a) excavation step 1 - case II, (b) excavation step 2 - case II, and (c) excavation step 3 - cases I-III.

[0031] Figure 5 A schematic diagram of the distribution results of maximum, intermediate, minimum principal stresses and microcracks of a stress field tensor method for identifying cracking of in-situ engineering surrounding rock during step-by-step excavation of a plate provided by an embodiment of the present invention (excavation step 3 - case I). DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0033] Example 1

[0034] Reference Figure 1 , which is the first embodiment of the present invention, and provides a method for identifying the stress field tensor of the cracking of the surrounding rock of the in-situ engineering step-by-step excavation plate, such as Figure 1 As shown, including:

[0035] S1, adopting layered sparse modeling method;

[0036] It should be noted that the layered sparse modeling method includes that the particles in multiple internal rectangular areas increase in size from the inside to the outside, and the particle bonding model adopts the particle flow program flat joint model to ensure sufficient resolution of the surrounding rock around the tunnel while ensuring calculation efficiency.

[0037] S2. Servo control applies in-situ stress to the target value, and static balance is achieved through force ratio; it should be noted that the in-situ stress includes, σ1=70MPa, σ2=65MPa, σ3=30MPa.

[0038] Furthermore, the servo control includes implementing servo control by writing code to ensure that the in-situ stress path is the same as the in-situ test. The servo control includes two stages: servo loading and servo confining pressure maintenance. Servo loading is to apply three-dimensional stress to the target value at a certain loading rate. The disturbance caused by surrounding rock excavation can still be kept within a small range of the target value through servo.

[0039] S3, keep the servo state, and carry out tunnel excavation and unloading in steps. After each step of excavation, the force ratio (1.0×10 -5 ) as the end condition; the excavation direction is from +X to -X, and the process is divided into stages I-II and III-V. Excavation is achieved by deleting particles in the area. Excavation is a step-by-step excavation, which is achieved by deleting particles within a specific contour line;

[0040] S4. Automatically generate the measurement circle measurement range, monitor and obtain the stress tensor, and the length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection. The principal stress axis is symmetrical along the center point of the measurement circle, and half of the principal stress axis is the magnitude of the principal stress. The change in the direction of the principal stress axis after the surrounding rock excavation and unloading indicates the degree of principal stress deflection. The three principal stresses of the stress tensor are perpendicular to each other, and the length of the principal stress axis indicates the magnitude of the principal stress.

[0041] Example 2

[0042] The second embodiment of the present invention provides a stress field tensor system for identifying cracking of the surrounding rock of an in-situ engineering project by step-by-step excavation, which is characterized by comprising a modeling module, a servo stress control module, a step-by-step excavation unloading module, and a stress tensor monitoring module.

[0043] Modeling module, adopts layered sparse modeling method;

[0044] Servo stress control module, servo control applies in-situ stress to the target value, and static balance is achieved through force ratio;

[0045] The step-by-step excavation and unloading module maintains the servo state and performs step-by-step excavation and unloading of the tunnel. The force ratio after each step of excavation is used as the end condition;

[0046] The stress tensor monitoring module automatically generates the measurement circle measurement range, monitors and obtains the stress tensor. The length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection.

[0047] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0048] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0049] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0050] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0051] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0052] Example 3

[0053] refer to Figure 2-Figure 5 , which is the third embodiment of the present invention, provides a method for identifying the stress field tensor of the step-by-step excavation plate cracking of the surrounding rock of an in-situ engineering project. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0054] In order to improve the surrounding rock and calculation efficiency near the excavation, layered sparse modeling was implemented using the code. The model size is 20×20×8m, with different particle size regions of 7, 14 and 20m from the inside to the outside. The maximum diameters of the filling particles are 0.166, 0.581 and 1.328m, respectively, and the ratio of the maximum particle size to the minimum particle size is 1.66. The excavation size is scaled uniformly with a scaling factor of 0.282. Servo control is implemented by writing code to ensure that the stress path is the same as the in-situ test, and excavation is achieved by deleting the particles in this area. The excavation direction is from +X to -X. The process is divided into several stages: (1) In stage I-II, true triaxial stress (σ1=70MPa, σ2=65MPa, σ3=30MPa) is applied to the model of 210761 particles, as shown in Figure 2As shown; (2) In the third stage, a straight-walled semicircular arch tunnel is excavated. The height and bottom width of the tunnel are 2.4 m each, the excavation depth is 4 m, and the number of particles in this stage is 198703; (3) In the fourth stage, the side of the straight-walled semicircular arch tunnel is expanded. The middle height of the tunnel is maintained at 2.4 m, the bottom width is expanded to 4 m, and the excavation depth is 3 m. The number of particles in this stage is 194603. (4) In the fifth stage, the bottom is expanded, the bottom width is maintained at 4 m, the bottom height is expanded by 2 m, and the excavation depth is 3 m. The number of particles in this stage is 183890. The model maintains true triaxial stress in stages III-V and maintains static equilibrium by applying a force ratio limit of 1.0×10-5. This staged excavation under true triaxial stress state is consistent with the stress path of field experiments, which is different from most previous studies that apply stress before excavation. The stress field tensor is calculated using the stress components acting on the three planes of the XYZ axis coordinate system. This calculation yields mutually perpendicular principal stress axes characterized by their relative lengths corresponding to specific stress components. It is implemented by writing a code using a measured circle. Figure 3 The measurement circle distribution and the principal stress expressions are shown. A total of 3200 measurement circles are located at X = 0 and X = 2m, of which 40 circles are oriented along the Y and Z axes and 1 circle is aligned with the X axis. In addition, at Y = 0m, there are 800 measurement circles, of which 40 are arranged along the X direction, 20 along the Z direction, and 1 along the Y direction. The radius of each measurement circle is 0.6m and the center is located at 0.25m, which improves the resolution of the stress field tensor distribution. The magnitude and direction of the stress field tensor are intuitively represented by a long symbol.

[0055] Figure 4The stress field tensor results after step-by-step excavation are given. The magnitude of the principal stress and the direction of the axis illustrate the rotation of the stress. In step 1-case II, the most significant observation is that the principal stress changes direction in the upper right and lower left regions of the excavation profile. Within a certain depth range, the direction of σ1 is arranged along the X-axis of the tunnel, the direction of σ2 is roughly parallel to the shallow excavation boundary, and the direction of σ3 is roughly perpendicular to the shallow excavation boundary. In step 2-case II, as the tunnel excavation boundary gradually increases, the principal stress rotation area and its magnitude and direction will be adjusted again. In step 3-cases I-III, the changes in the rotation amplitude and direction at different distances from the tunnel face are given. The magnitude and direction of the principal stress in the adjacent working face are significantly different from those in the non-adjacent working face. After tunnel excavation, the σ1 stress rotation angle of the surrounding rock in the upper right and lower left regions reaches the maximum value within a certain range, and deviates 90° in the X-axis direction. As the distance from the excavation profile increases, the deviation angle of σ1 gradually decreases to 0°. In the area where σ1 is facing the X-axis, changes in the directions of σ2 and σ3 are often observed at each monitoring point. Taking the upper right area as an example, the direction of σ2 gradually becomes parallel to the excavation profile found in this section, resulting in σ2 forming an angle of about 45° in the negative direction of the Y axis, indicating the direction change caused by the excavation activity in this area. The microcracks mainly extend in the direction parallel to σ1 and σ2, and the particle contact initially reaches the tensile bonding strength relative to σ1 and σ2. The results show that as the tunnel face enters the rock mass, the spatiotemporal evolution of the three-dimensional stress field undergoes a series of changes, mainly manifested as an increase or decrease in the principal stress. Along these changes, the principal stress axis rotates multiple times. The cracks caused by step-by-step excavation and the tunnel section jointly affect the magnitude and direction of the principal stress. This process illustrates the spatiotemporal evolution of the three-dimensional stress field, including the rotation of stress and the fluctuation of the magnitude of the principal stress.

[0056] like Figure 5 The visualization results of the stress field tensor regional changes after step-by-step excavation are given. Figure 4 The three principal stresses are displayed separately to visualize the regional range of the principal stress tensor.

[0057] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for identifying the stress field tensor of cracking of the surrounding rock of an in-situ engineering project in a step-by-step excavation plate, characterized in that: include, Adopting layered sparse modeling approach; Servo control applies in-situ stress to the target value, and static balance is achieved through force ratio; Keep the servo state, carry out tunnel excavation and unloading in steps, and use the force ratio after each step of excavation as the end condition; The measuring circle determination range is automatically generated to monitor and obtain the stress tensor. The length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection.

2. A method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation of plate as claimed in claim 1, characterized in that: The layered sparse modeling method includes using a particle flow program to model the flat joints in multiple internal rectangular areas, with the particles increasing from the inside to the outside, so that the surrounding rock around the tunnel has sufficient resolution while ensuring the calculation efficiency.

3. A method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation of plate as claimed in claim 2, characterized in that: The in-situ stresses include: σ1=70MPa, σ2=65MPa, and σ3=30MPa.

4. A method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation of plate as claimed in claim 3, characterized in that: The servo control includes implementing servo control by writing code, ensuring that the in-situ stress path is the same as the in-situ test, and implementing excavation by deleting particles in the area; The excavation direction is from +X to -X, and the process is divided into stages I-II and III-V.

5. A method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation of plate as claimed in claim 4, characterized in that: In the I-II stage, true triaxial stress is applied in the model; In the III-V stage, the true triaxial stress is maintained and the stress is increased by applying 1.0×10 -5 The force ratio limit maintains static equilibrium.

6. A method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation of plate as claimed in claim 5, characterized in that: The monitoring and obtaining of stress tensors includes generating a measuring circle by programming in Python language, and calculating average tensors of particles in three directions within the measuring circle.

7. A method for identifying the stress field tensor of cracking of the in-situ engineering surrounding rock in step-by-step excavation of plate as claimed in claim 6, characterized in that: The length and direction of the principal stress axis respectively measure the magnitude of the principal stress and the degree of deflection, including that the principal stress axis is symmetrical along the center point of the measuring circle, and half of the principal stress axis is the magnitude of the principal stress. The magnitude of the change in the direction of the principal stress axis after the surrounding rock excavation and unloading indicates the degree of principal stress deflection.

8. A system based on a method for identifying the cracking stress field tensor of the in-situ engineering surrounding rock in step-by-step excavation plate according to any one of claims 1 to 7, characterized in that: It includes modeling module, servo stress control module, step-by-step excavation and unloading module, and stress tensor monitoring module.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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