A long-term dynamic monitoring method for targeted identification of tensile-shear fracture network in tunnel surrounding rock

Abstract

The present invention discloses a long-term dynamic monitoring method for targeted identification of tensile-shear fracture networks in tunnel surrounding rocks. Based on the surrounding rock yield criterion, the present invention determines the range of the tunnel plastic zone through theoretical analysis through ground stress environment testing combined with surrounding rock mechanical property determination. Using wireless radio frequency identification technology, semi-active electronic tags are arranged inside the surrounding rock within the range of 1.2-2 times the plastic zone through tunnel surrounding rock drilling. Based on the impact of tunnel mining, the tag arrangement density and information collection frequency are adjusted to obtain multi-point displacement information inside the surrounding rock. By collecting the tag displacement evolution information, the relative displacement size, direction and spatial position change relative to the borehole between adjacent tags in the same borehole are determined. The relative displacement vector evolution process of the tags in the tunnel surrounding rock is periodically recorded by a signal receiving device, and the development morphology of the tunnel tensile-shear fracture network is deduced and judged, so as to realize the targeted identification and long-term dynamic monitoring of the surrounding rock tensile-shear fracture network, and provide real-time information support for the refined targeted control of the surrounding rock.

Description

Technical Field

[0001] The invention relates to the technical field of engineering rock mass, in particular to a long-term dynamic monitoring method for targeted identification of tensile-shear fracture networks of tunnel surrounding rocks. Background Art

[0002] In the soft rock tunnels located in the complex environment of "three highs and one disturbance" at depth, the deformation, destruction and instability of the surrounding rock are significantly affected by high ground stress and mining disturbance, and based on this, a tensile-shear fracture network with significant directional characteristics is generated, resulting in non-uniform deformation or local instability of the surrounding rock, seriously affecting the safe mining and work efficiency of the working face. The development of tensile-shear fractures in the tunnel surrounding rock will cause deformation and destruction of varying degrees in the roof, floor and both sides, affecting the safe production efficiency of the working face. At present, there are few monitoring methods for the evolution of tensile-shear fractures in the tunnel surrounding rock; during the tunnel maintenance period, it is impossible to effectively monitor the development of the tunnel surrounding rock fracture network in real time. Existing methods such as borehole peeping can only monitor the tunnel surrounding rock fractures at a certain moment, and cannot achieve real-time dynamic monitoring of the tunnel surrounding rock; existing methods such as borehole peeping and microseismic monitoring cannot accurately target the tunnel surrounding rock fracture network, and cannot effectively distinguish the development of tensile-shear fractures in the surrounding rock; Summary of the invention

[0003] The purpose of the present invention is to provide a long-term dynamic monitoring method for targeted identification of tensile shear fracture network of tunnel surrounding rock in order to solve the above-mentioned technical problems. In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

[0004] A long-term dynamic monitoring method for targeted identification of tensile-shear fracture network of surrounding rock in tunnels involves the following steps:

[0005] (1) Based on the mine geological data, the stress relief method is used to test and determine the ground stress environment information around the tunnel, and to clarify the geological conditions, rock type and mechanical properties of the surrounding rock of the tunnel, including the direction and magnitude of the principal stress near the tunnel and the mechanical parameters of the coal rock mass surrounding the tunnel;

[0006] (2) Based on the Mohr-Coulomb surrounding rock yield criterion and combined with the initial stress field measured on site, the stress distribution around the roadway is determined, the stress equation of the roadway plastic zone is established, the critical stress for the rock mass to enter the plastic state is calculated, and the boundary of the roadway plastic zone under the engineering conditions is determined;

[0007] (3) The laboratory determines the optimal transmission frequency of the electrical signal in the coal rock mass surrounding the tunnel. By changing the frequency of the electrical signal generated by the signal generator, the signal strength, waveform, and phase received by the receiver after passing through different coal rock masses are observed to determine the frequency range with relatively high signal strength, relatively low transmission loss, and relatively large signal-to-noise ratio;

[0008] (4) Selecting a low-frequency signal within the optimal transmission frequency range as the activation frequency of the electronic tag, setting a high-frequency signal within the optimal transmission frequency range for data transmission, and using polypropylene, which is lightweight, chemically resistant, and suitable for harsh environments, as the packaging material to encapsulate the semi-active electronic tag;

[0009] (5) Determine the scope of influence of the engineering environment on the mining surrounding rock of the tunnel. Based on the radius of the tunnel plastic zone obtained by theoretical calculation, arrange drilling holes on the top and bottom plates and the left and right sides of the tunnel within 1.2-2 times the plastic zone. The drilling direction of the drilling holes is perpendicular to the free surface exposed by the tunnel excavation. The number of drilling holes in each direction shall be no less than 3 and evenly arranged.

[0010] (6) Electronic tags are arranged using a YT24 pneumatic rock drill, with the tags spaced 0.2-0.5 m apart, evenly placed in accordance with the principle of dense in shallow areas and sparse in deep areas. Epoxy resin glue is used to fix the relative position of the electronic tags in the borehole;

[0011] (7) A low-frequency excitation signal is sent in the tunnel by a reader / writer to excite the electronic tags in the surrounding rock, and the displacement information of the electronic tags arranged in the borehole is periodically collected. The signal collection frequency can be adjusted to a cycle of 1-7 days according to the degree of impact of mining;

[0012] (8) Based on the periodically collected displacement information of the electronic tags, a multi-point displacement vector field of the surrounding rock is established; the increase in the relative distance between adjacent electronic tags along the drilling direction is taken as the location of the development of tension fracture; the increase in the relative distance between adjacent electronic tags along the normal direction of the drilling is taken as the location of the development of shear fracture; and the deviation of continuous electronic tags from the drilling direction at the same angle is taken as the location of the rotation of the rock mass in the surrounding rock;

[0013] (9) According to the relative displacement evolution law of the electronic tags in the surrounding rock, the development state and development process of the tensile-shear fracture network in the surrounding rock are judged, the morphological characteristics of the fracture network are analyzed, and the dynamic evolution process of the tensile-shear fracture network is obtained, so as to realize the long-term dynamic monitoring of the development of the tensile-shear fracture network in the surrounding rock during the tunnel service period.

[0014] Furthermore, the mechanical parameters of the coal rock mass surrounding the tunnel include elastic modulus, cohesion, internal friction angle, and Poisson's ratio.

[0015] The present invention has significant technical effects due to the adoption of the above technical solutions: (1) This method is based on the range of the surrounding rock plastic zone. By arranging semi-active electronic tags in the tunnel surrounding rock, the relative displacement information of multiple points in the surrounding rock is obtained, so that the tunnel surrounding rock fracture network is visualized and clarified. (2) This method fully considers the timeliness of the development of the tunnel surrounding rock tensile shear fracture network, and reflects the real-time changes of the surrounding rock at different times and depths through the displacement evolution law of the electronic tags, thereby realizing the dynamic monitoring of the surrounding rock tensile shear fracture network. At the same time, the low energy consumption of the semi-active electronic tags during the dormant period is fully utilized. According to the differences in the impact of mining on the tunnel, data is continuously collected dynamically and periodically, which can meet the long-term intermittent collection of tunnel surrounding rock displacement information and realize long-term monitoring of the tunnel surrounding rock fracture network development process. (3) This method uses the different directions and sizes of the relative displacement of electronic tags in the borehole to determine the development of tensile fractures when adjacent electronic tags are relatively far apart in the borehole direction, the development of shear fractures when adjacent electronic tags are relatively far apart in the borehole normal direction, and the rock mass rotation when continuous electronic tags deviate from the borehole direction at the same angle. This method achieves targeted identification of tensile shear fractures and rock mass rotation in the surrounding rock of the tunnel, providing data support for targeted support of the tunnel surrounding rock. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a technical roadmap of a long-term dynamic monitoring method for targeted identification of tensile-shear fracture network of tunnel surrounding rock in the present invention;

[0017] Figure 2a It is a schematic diagram of the roadway section label in the electronic label arrangement diagram used for targeted identification of the tensile-shear fracture network of the roadway surrounding rock in the present invention;

[0018] Figure 2b It is a schematic diagram of full-length lane tags in the electronic tag arrangement diagram used for targeted identification of the tensile-shear fracture network of the lane surrounding rock in the present invention;

[0019] Figure 3a It is a tensile fracture principle diagram in the tensile shear fracture network identification diagram of the tunnel surrounding rock in the present invention;

[0020] Figure 3b It is a rock mass rotation principle diagram in the schematic diagram of the tunnel surrounding rock tensile shear fracture network identification in the present invention;

[0021] Figure 3c This is the shear fracture principle diagram in the schematic diagram of the tunnel surrounding rock tensile shear fracture network identification in the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be noted that the terms "vertical", "upper", "lower", "horizontal", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, "first", "second", "third", and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0024] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, it can be a mechanical connection, it can be an electrical connection, it can be a direct connection, it can be connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] like Figure 1 -3, a long-term dynamic monitoring method for targeted identification of tensile-shear fracture network of tunnel surrounding rock in the present invention involves the following steps:

[0026] (1) Based on the mine geological data, the stress relief method is used to test and determine the ground stress environment information around the tunnel, and to clarify the geological conditions, rock type and mechanical properties of the surrounding rock of the tunnel, including the direction and magnitude of the principal stress near the tunnel and the mechanical parameters of the coal rock mass surrounding the tunnel;

[0027] (2) Based on the Mohr-Coulomb surrounding rock yield criterion and combined with the initial stress field measured on site, the stress distribution around the roadway is determined, the stress equation of the roadway plastic zone is established, the critical stress for the rock mass to enter the plastic state is calculated, and the boundary of the roadway plastic zone under the engineering conditions is determined;

[0028] (3) The laboratory determines the optimal transmission frequency of the electrical signal in the coal rock mass surrounding the tunnel. By changing the frequency of the electrical signal generated by the signal generator, the signal strength, waveform, and phase received by the receiver after passing through different coal rock masses are observed to determine the frequency range with relatively high signal strength, relatively low transmission loss, and relatively large signal-to-noise ratio;

[0029] (4) Selecting a low-frequency signal within the optimal transmission frequency range as the activation frequency of the electronic tag, setting a high-frequency signal within the optimal transmission frequency range for data transmission, and using polypropylene, which is lightweight, chemically resistant, and suitable for harsh environments, as the packaging material to encapsulate the semi-active electronic tag;

[0030] (5) Determine the scope of influence of the engineering environment on the mining surrounding rock of the tunnel. Based on the radius of the tunnel plastic zone obtained by theoretical calculation, arrange drilling holes on the top and bottom plates and the left and right sides of the tunnel within 1.2-2 times the plastic zone. The drilling direction of the drilling holes is perpendicular to the free surface exposed by the tunnel excavation. The number of drilling holes in each direction shall be no less than 3 and evenly arranged.

[0031] (6) Electronic tags are arranged using a YT24 pneumatic rock drill, with the tags spaced 0.2-0.5 m apart, evenly placed in accordance with the principle of dense in shallow areas and sparse in deep areas. Epoxy resin glue is used to fix the relative position of the electronic tags in the borehole;

[0032] (7) A low-frequency excitation signal is sent in the tunnel by a reader / writer to excite the electronic tags in the surrounding rock, and the displacement information of the electronic tags arranged in the borehole is periodically collected. The signal collection frequency can be adjusted to a cycle of 1-7 days according to the degree of impact of mining;

[0033] (8) Based on the periodically collected displacement information of the electronic tags, a multi-point displacement vector field of the surrounding rock is established; the increase in the relative distance between adjacent electronic tags along the drilling direction is taken as the location of the development of tension fracture; the increase in the relative distance between adjacent electronic tags along the normal direction of the drilling is taken as the location of the development of shear fracture; and the deviation of continuous electronic tags from the drilling direction at the same angle is taken as the location of the rotation of the rock mass in the surrounding rock;

[0034] (9) According to the relative displacement evolution law of the electronic tags in the surrounding rock, the development state and development process of the tensile shear fracture network in the surrounding rock are judged, the morphological characteristics of the fracture network are analyzed, the dynamic evolution process of the tensile shear fracture network is obtained, and the long-term dynamic monitoring of the tensile shear fracture network development of the surrounding rock in the tunnel service period is realized;

[0035] The mechanical parameters of the tunnel surrounding coal rock mass include elastic modulus, cohesion, internal friction angle, and Poisson's ratio.

[0036] The embodiment of the present application relates to a method for monitoring the fracture state of tunnel surrounding rock, which is particularly suitable for long-term dynamic monitoring and targeted identification of tensile shear fracture networks. In soft rock tunnels in a complex environment of "three highs and one disturbance" at depth, the deformation, destruction and instability of the surrounding rock are significantly affected by high ground stress and mining disturbance, and based on this, a tensile shear fracture network with significant directionality is generated, resulting in non-uniform deformation or local instability of the surrounding rock, which seriously affects the safe mining and work efficiency of the working face. Based on the surrounding rock yield criterion, the range of the tunnel plastic zone is determined by theoretical analysis through ground stress environment testing combined with the determination of the mechanical properties of the surrounding rock. Using wireless radio frequency identification technology, semi-active electronic tags are arranged inside the surrounding rock within the range of 1.2-2 times the plastic zone through the tunnel surrounding rock drilling to record the displacement information of the rock mass inside the surrounding rock. Based on the impact of tunnel mining, the density of electronic tag arrangement in the borehole and the frequency of tag displacement information collection are adjusted to obtain multi-point displacement information of the rock mass inside the surrounding rock. The relative displacement size, direction and spatial position change between adjacent electronic tags in the same borehole are determined by the displacement evolution information of the electronic tags collected by the receiver. The increase in the relative distance between adjacent electronic tags along the drilling direction is the location of tensile fracture development; the increase in the relative distance between adjacent electronic tags along the drilling normal direction is the location of shear fracture development, and the deviation of continuous electronic tags from the drilling direction at the same angle is the location of rock mass rotation in the surrounding rock. The signal receiving device periodically records the evolution process of the relative displacement vector of the electronic tags in the surrounding rock of the tunnel, records and analyzes the relative displacement change process of the rock mass in the surrounding rock, deduces and identifies the development morphology of the tunnel tensile-shear fracture network, realizes the targeted identification and long-term dynamic monitoring of the tensile-shear fracture network of the surrounding rock, and provides real-time information support for the refined targeted control of the surrounding rock.

[0037] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The above-described embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A long-term dynamic monitoring method for targeted identification of tensile-shear fracture network of tunnel surrounding rock, characterized in that: The following steps are involved: (1) Based on the mine geological data, the stress relief method is used to test and determine the ground stress environment information around the tunnel, and to clarify the geological conditions, rock type and mechanical properties of the surrounding rock of the tunnel, including the direction and magnitude of the principal stress near the tunnel and the mechanical parameters of the coal rock mass surrounding the tunnel; (2) Based on the Mohr-Coulomb surrounding rock yield criterion and combined with the initial stress field measured on site, the stress distribution around the roadway is determined, the stress equation of the roadway plastic zone is established, the critical stress for the rock mass to enter the plastic state is calculated, and the boundary of the roadway plastic zone under the engineering conditions is determined; (3) The laboratory determines the optimal transmission frequency of the electrical signal in the coal rock mass surrounding the tunnel. By changing the frequency of the electrical signal generated by the signal generator, the signal strength, waveform, and phase received by the receiver after passing through different coal rock masses are observed to determine the frequency range with relatively high signal strength, relatively low transmission loss, and relatively large signal-to-noise ratio; (4) Selecting a low-frequency signal within the optimal transmission frequency range as the activation frequency of the electronic tag, setting a high-frequency signal within the optimal transmission frequency range for data transmission, and using polypropylene, which is lightweight, chemically resistant, and suitable for harsh environments, as the packaging material to encapsulate the semi-active electronic tag; (5) Determine the scope of influence of the engineering environment on the mining surrounding rock of the tunnel. Based on the radius of the tunnel plastic zone obtained by theoretical calculation, arrange drilling holes on the top and bottom plates and the left and right sides of the tunnel within 1.2-2 times the plastic zone. The drilling direction of the drilling holes is perpendicular to the free surface exposed by the tunnel excavation. The number of drilling holes in each direction shall be no less than 3 and evenly arranged. (6) Electronic tags are arranged using a YT24 pneumatic rock drill, with the tags spaced 0.2-0.5 m apart, evenly placed in accordance with the principle of dense in shallow areas and sparse in deep areas. Epoxy resin glue is used to fix the relative position of the electronic tags in the borehole; (7) A low-frequency excitation signal is sent in the tunnel by a reader / writer to excite the electronic tags in the surrounding rock, and the displacement information of the electronic tags arranged in the borehole is periodically collected. The signal collection frequency can be adjusted to a cycle of 1-7 days according to the degree of impact of mining; (8) Based on the periodically collected displacement information of the electronic tags, a multi-point displacement vector field of the surrounding rock is established; the increase in the relative distance between adjacent electronic tags along the drilling direction is taken as the location of the development of tension fracture; the increase in the relative distance between adjacent electronic tags along the normal direction of the drilling is taken as the location of the development of shear fracture; and the deviation of continuous electronic tags from the drilling direction at the same angle is taken as the location of the rotation of the rock mass in the surrounding rock; (9) According to the relative displacement evolution law of the electronic tags in the surrounding rock, the development state and development process of the tensile-shear fracture network in the surrounding rock are judged, the morphological characteristics of the fracture network are analyzed, and the dynamic evolution process of the tensile-shear fracture network is obtained, so as to realize the long-term dynamic monitoring of the development of the tensile-shear fracture network in the surrounding rock during the tunnel service period.

2. A long-term dynamic monitoring method for targeted identification of tensile-shear fracture network of tunnel surrounding rock according to claim 1, characterized in that: The mechanical parameters of the tunnel surrounding coal rock mass include elastic modulus, cohesion, internal friction angle, and Poisson's ratio.

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