Method and system for pre-reinforcing surrounding rock

Abstract

The invention belongs to the field of surrounding rock pre-reinforcement, and relates to a surrounding rock pre-reinforcement method and system.The surrounding rock pre-reinforcement method comprises the steps that the real-time tunnel face surrounding rock grade and rock mass parameters are obtained, and the rock mass parameters comprise the elastic modulus, the cohesive force and the internal friction angle; constructing numerical models under different grades of surrounding rocks based on the real-time tunnel face surrounding rock grades and rock mass parameters; based on the numerical models under different grades of surrounding rocks, a strength reduction method is adopted, and the safety coefficient of the tunnel face is calculated through a finite difference model and a cuspidal point mutation model to obtain a surrounding rock pre-reinforcement strategy; and the surrounding rock is pre-reinforced in real time according to the surrounding rock pre-reinforcing strategy. The problems of poor safety and low efficiency of tunnel construction caused by an immobilized surrounding rock pre-reinforcement strategy aiming at a complex and changeable geological environment are solved.

Description

Technical Field

[0001] The invention relates to the field of surrounding rock pre-reinforcement, and particularly discloses a surrounding rock pre-reinforcement method and system. Background Art

[0002] As a vital component of modern transportation networks, tunnel engineering plays a crucial role in promoting regional economic development and improving transportation infrastructure. During tunnel excavation, due to the complexity of the geological environment, especially when encountering weak surrounding rock and poor geological conditions, tunnel stability becomes a critical factor in project safety and success. To ensure tunnel stability, pre-reinforcement of the surrounding rock has become an essential engineering measure.

[0003] Traditional surrounding rock pre-reinforcement methods are often based on the geological conditions of the initial surrounding rock, and a fixed surrounding rock pre-reinforcement measure is adopted throughout the entire process of tunnel construction. Existing surrounding rock pre-reinforcement measures include applying advanced pipe-roof grouting reinforcement, applying face anchor reinforcement, and applying face shotcrete reinforcement. Among them, applying advanced pipe-roof grouting reinforcement is: before tunnel excavation, a circle of pipe roofs is driven in advance around the surrounding rock at the top of the tunnel. This circle of pipe roofs forms an "arch effect", which can transfer the upper surrounding rock pressure to both sides of the tunnel through the "arch effect"; applying face anchor reinforcement is: driving multiple anchors on the face to give the face a support force to prevent the face from being squeezed, deformed, and collapsed. Figure 1 and Figure 2 shown.

[0004] However, the traditional surrounding rock pre-reinforcement method has the following problems:

[0005] (1) In view of the complex and changeable geological environment, a fixed surrounding rock pre-reinforcement measure is always adopted under different geological conditions. There is a lack of real-time selection of appropriate surrounding rock pre-reinforcement measures based on the surrounding rock grade and rock mass parameters of the tunnel face under different geological conditions. As a result, the support strength of the fixed surrounding rock pre-reinforcement measures is excessive or insufficient, which affects the stability and construction safety of the tunnel, increases construction costs and time, and reduces the overall efficiency of the project.

[0006] For example, when the geological conditions of the surrounding rock are good in the early stage of tunnel construction, but are relatively weak or more broken in the later stage, the initially set surrounding rock pre-reinforcement measures may not be able to provide sufficient support strength under the geological conditions of the surrounding rock in the later stage, which may easily lead to surrounding rock collapse or instability during tunnel construction; or, when the geological conditions of the surrounding rock are relatively weak or more broken in the early stage of tunnel construction, but are relatively good in the later stage, the initially set surrounding rock pre-reinforcement measures may provide excessive support strength under the geological conditions of the surrounding rock in the later stage, resulting in waste of resources and increased costs; such surrounding rock pre-reinforcement measures set based on the initial surrounding rock geological conditions may not only affect the construction safety of the tunnel, but also increase construction costs and time, and reduce the overall efficiency of the project.

[0007] (2) The specific effects of different surrounding rock pre-reinforcement measures on tunnel stability are unclear, and there is a lack of means to quantify the differences between different surrounding rock pre-reinforcement measures. Summary of the Invention

[0008] The purpose of the present invention is to provide a surrounding rock pre-reinforcement method and system to solve the problem that fixed surrounding rock pre-reinforcement strategies in complex and changeable geological environments lead to poor safety and low efficiency in tunnel construction.

[0009] The specific scheme of the present invention is as follows:

[0010] A surrounding rock pre-reinforcement method, comprising:

[0011] Obtaining real-time tunnel face surrounding rock grade and rock mass parameters, including elastic modulus, cohesion, and internal friction angle;

[0012] Construct numerical models of surrounding rock with different grades based on real-time tunnel face surrounding rock grades and rock mass parameters;

[0013] Based on numerical models of surrounding rock of different grades, the strength reduction method is used to calculate the safety factor of the tunnel face through the finite difference model and the cusp catastrophe model to obtain the surrounding rock pre-reinforcement strategy;

[0014] The surrounding rock is pre-reinforced in real time according to the surrounding rock pre-reinforcement strategy.

[0015] In some embodiments, the surrounding rock pre-reinforcement strategy includes no advance support, applying advance pipe-roof support, and applying advance pipe-roof support and tunnel face anchor support in sequence.

[0016] In some embodiments, the step of calculating the safety factor of the tunnel face to obtain a surrounding rock pre-reinforcement strategy includes the following steps:

[0017] S1. Calculate the safety factor of the tunnel face without advance support. If the safety factor of the tunnel face is greater than 1, adopt the surrounding rock pre-reinforcement strategy without advance support. If the safety factor of the tunnel face is less than or equal to 1, execute step S2.

[0018] S2. Calculate the safety factor of the tunnel face under the application of advanced pipe-roof support. If the safety factor of the tunnel face is greater than 1, adopt the surrounding rock pre-reinforcement strategy of applying advanced pipe-roof support. If the safety factor of the tunnel face is less than or equal to 1, execute step S3.

[0019] S3. Calculate the tunnel face safety factor when applying advanced pipe-roof support and tunnel face anchor support in sequence. If the tunnel face safety factor is greater than 1, adopt the surrounding rock pre-reinforcement strategy of applying advanced pipe-roof support and tunnel face anchor support in sequence.

[0020] In some embodiments, the calculation of the safety factor of the tunnel face comprises the steps of:

[0021] S11. Based on the numerical models of surrounding rock of different grades, the preset initial reduction coefficients and the preset variation of the reduction coefficients, a strength reduction method is used to obtain a number of reduction coefficients and the corresponding tunnel face displacements through a finite difference model;

[0022] S12, performing quadratic polynomial fitting on a plurality of reduction coefficients and the tunnel face displacements corresponding to the plurality of reduction coefficients, respectively, to obtain a plurality of quadratic polynomials of the tunnel face displacements;

[0023] S13, linearly changing a plurality of quadratic polynomials of face displacement to obtain a plurality of standard potential functions of the cusp catastrophe model, and obtaining a plurality of control variable u values and a plurality of control variable v values based on the plurality of standard potential functions of the cusp catastrophe model;

[0024] S14. Based on the values of the plurality of control variables u and the values of the plurality of control variables v, a plurality of discriminant values under the tunnel face displacement corresponding to the reduction coefficient are obtained by using the discriminant of the cusp catastrophe model;

[0025] S15. Based on a plurality of discriminant values under the tunnel face displacement corresponding to the reduction coefficient, the mutation point of the numerical model under different grades of surrounding rock is determined, and the reduction coefficient corresponding to the mutation point is used as the tunnel face safety factor.

[0026] In some embodiments, the strength reduction method includes:

[0027] Based on the initial reduction coefficient and the change value of the reduction coefficient, the change value of the reduction coefficient is gradually increased on the initial reduction coefficient through a finite difference model, so that the reduction coefficient increases in equal value, thereby generating several reduction coefficients;

[0028] When the reduction coefficient increases, the cohesion and the internal friction angle are reduced synchronously to generate a number of reduced cohesion and internal friction angles corresponding to the reduction coefficients.

[0029] In some embodiments, obtaining the tunnel face displacements corresponding to the plurality of reduction coefficients includes:

[0030] Based on several reduction coefficients and the reduced cohesion and internal friction angle corresponding to the reduction coefficients, the tunnel face displacements corresponding to the reduction coefficients are obtained through the finite difference model.

[0031] In some embodiments, the reduction formula for reducing the cohesion and the internal friction angle is:

[0032]

[0033] Among them, F is the reduction factor, C is the cohesion, and C F is the reduced cohesive strength, is the internal friction angle, is the reduced internal friction angle.

[0034] In some embodiments, the expression of the fourth-order polynomial of the tunnel face displacement is:

[0035] S=a4F 4 +a3F 3 +a2F 2 +a1F+a0,

[0036] Where F is the reduction coefficient, S is the tunnel face displacement corresponding to the reduction coefficient, and ɑ1, ɑ2, ɑ3, and ɑ4 are the coefficients of each polynomial obtained by fitting the reduction coefficient F and the tunnel face displacement S corresponding to the reduction coefficient into a fourth-order polynomial.

[0037] In some embodiments, the expression of the standard potential function of the cusp catastrophe model is:

[0038] S'=p 4 +up 2 +vp+c,

[0039] Among them, p is the intermediate variable in the linear change process, c is the constant term, S′ is an equation of the standard potential function expression of the cusp catastrophe model obtained after the linear change, and u and v are the control variables in the standard potential function of the cusp catastrophe model obtained after the linear change.

[0040] The present invention also relates to a surrounding rock pre-reinforcement system, which is used in the above-mentioned surrounding rock pre-reinforcement method, comprising:

[0041] A real-time data acquisition module is used to obtain real-time tunnel face surrounding rock grade and rock mass parameters, including elastic modulus, cohesion, and internal friction angle; and to construct numerical models for different grades of surrounding rock based on the real-time tunnel face surrounding rock grade and rock mass parameters;

[0042] The reduction module is used to obtain several reduction coefficients and the corresponding tunnel face displacements of the reduction coefficients based on the numerical models of different grades of surrounding rock, the preset initial reduction coefficients and the preset change value of the reduction coefficients by using the strength reduction method and the finite difference model;

[0043] A polynomial fitting module is used to perform fourth-order polynomial fitting on a plurality of reduction coefficients and the tunnel face displacements corresponding to the plurality of reduction coefficients, thereby obtaining a plurality of fourth-order polynomials of the tunnel face displacements;

[0044] A conversion module is used to linearly transform a plurality of quadratic polynomials of face displacement to obtain a plurality of standard potential functions of cusp catastrophe models, and to obtain a plurality of control variable u values and a plurality of control variable v values based on the plurality of standard potential functions of cusp catastrophe models;

[0045] The discriminant module is used to calculate the tunnel face safety factor based on several control variable u values and several control variable v values through the cusp catastrophe model discriminant formula, and obtain the surrounding rock pre-reinforcement strategy according to the tunnel face safety factor;

[0046] The pre-reinforcement module is used to perform real-time pre-reinforcement of surrounding rock according to the surrounding rock pre-reinforcement strategy.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] Based on the real-time surrounding rock grade and rock mass parameters of the tunnel face, the strength reduction method is used to calculate the tunnel face safety factor through the finite difference model and the cusp catastrophe model to obtain the surrounding rock pre-reinforcement strategy. The surrounding rock is pre-reinforced in real time according to the surrounding rock pre-reinforcement strategy. The surrounding rock can be dynamically adjusted according to the real-time geological conditions of the surrounding rock to achieve real-time and effective pre-reinforcement of the surrounding rock. This meets the need for dynamic adjustment of the pre-reinforcement strategy as the geological conditions of the surrounding rock change during tunnel construction, avoids the situation where a fixed pre-reinforcement strategy cannot meet the complex and changeable geological conditions, and prevents the occurrence of insufficient or excessive pre-reinforcement strength. It provides a scientific and accurate surrounding rock pre-reinforcement strategy for tunnel construction, achieves real-time and effective pre-reinforcement, thereby improving the safety and efficiency of tunnel construction and saving costs. At the same time, it can quantify the specific effects of different surrounding rock pre-reinforcement strategies on tunnel stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the existing surrounding rock pre-reinforcement measures in the present invention.

[0050] Figure 2 This is a schematic diagram of the existing surrounding rock pre-reinforcement measures in the present invention.

[0051] Figure 3 This is a flow chart of a surrounding rock pre-reinforcement method in Example 1 of the present invention.

[0052] Figure 4 Schematic diagram of the equilibrium surface and bifurcation set in Example 1 of the present invention.

[0053] Figure 5 This is a block diagram of a surrounding rock pre-reinforcement system in Example 1 of the present invention.

[0054] Figure 6 Schematic diagram of a fourth-order polynomial fitting curve without advanced support in Example 2 of the present invention.

[0055] Figure 7 Schematic diagram of a fourth-order polynomial fitting curve under advanced pipe-roof support in Example 2 of the present invention.

[0056] Figure 8 Schematic diagram of a fourth-order polynomial fitting curve when the advanced pipe-roof support and the tunnel face anchor support are applied sequentially in Example 2 of the present invention.

[0057] Reference symbols: F-reduction factor, S-tunnel face displacement corresponding to the reduction factor. DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0059] Example 1

[0060] A surrounding rock pre-reinforcement method, comprising:

[0061] Obtain real-time tunnel face surrounding rock grade and rock mass parameters, including elastic modulus, cohesion and internal friction angle;

[0062] Construct numerical models of surrounding rock with different grades based on real-time tunnel face surrounding rock grades and rock mass parameters;

[0063] Based on numerical models of surrounding rock of different grades, the strength reduction method is used to calculate the safety factor of the tunnel face through the finite difference model and the cusp catastrophe model to obtain the surrounding rock pre-reinforcement strategy;

[0064] The surrounding rock is pre-reinforced in real time according to the surrounding rock pre-reinforcement strategy.

[0065] The surrounding rock pre-reinforcement strategies include no advance support, application of advance pipe-roof support, and application of advance pipe-roof support and face anchor support in sequence.

[0066] Based on the real-time surrounding rock grade and rock mass parameters of the tunnel face, the strength reduction method is used to calculate the tunnel face safety factor through the finite difference model and the cusp catastrophe model to obtain the surrounding rock pre-reinforcement strategy. The surrounding rock is pre-reinforced in real time according to the surrounding rock pre-reinforcement strategy. The surrounding rock can be dynamically adjusted according to the real-time geological conditions of the surrounding rock to achieve real-time and effective pre-reinforcement of the surrounding rock. This meets the need for dynamic adjustment of the pre-reinforcement strategy as the geological conditions of the surrounding rock change during tunnel construction, avoids the situation where a fixed pre-reinforcement strategy cannot meet the complex and changeable geological conditions, and prevents the occurrence of insufficient or excessive pre-reinforcement strength. It provides a scientific and accurate surrounding rock pre-reinforcement strategy for tunnel construction, achieves real-time and effective pre-reinforcement, thereby improving the safety and efficiency of tunnel construction and saving costs. At the same time, it can quantify the specific effects of different surrounding rock pre-reinforcement strategies on tunnel stability.

[0067] like Figure 3 As shown, a surrounding rock pre-reinforcement method specifically includes the following steps:

[0068] S1. Obtain the real-time tunnel face surrounding rock grade and rock mass parameters, and construct numerical models under different grades of surrounding rock based on the real-time tunnel face surrounding rock grade and rock mass parameters.

[0069] Before and during tunnel construction, geological surveys and predictions are carried out on the surrounding rock. A combination of long-distance macroscopic predictions and short-distance accurate predictions, in-tunnel detection and external ground surveys, and geological and geophysical methods are used to obtain real-time face rock grade and rock mass parameters from the tunnel's surrounding rock. Rock mass parameters include elastic modulus, cohesion, and internal friction angle.

[0070] Among them, according to the Kilometer Tunnel Design Specifications (JTG3370.1-2018), the surrounding rock grade is usually divided into six levels; there are also smart devices that can obtain the surrounding rock grade through sonar testing.

[0071] Based on the tunnel face surrounding rock grade, elastic modulus, cohesion and internal friction angle, numerical models for different surrounding rock grades that conform to the Mohr-Coulomb constitutive model are constructed, including:

[0072] A geometric model is established based on the surrounding rock grade of the tunnel face. The geometric model is based on the tunnel depth, the geological conditions around the tunnel, the tunnel geometry, and the selected excavation method.

[0073] Then mesh the geometric model. Meshing is done by using the built-in language of numerical simulation software to mesh the entire geometric model.

[0074] Then, the elastic modulus, cohesion and internal friction angle are assigned to the meshed geometric model to form the Mohr-Coulomb constitutive model.

[0075] Then, boundary conditions are set for the numerical models under different levels of surrounding rock to be constructed. Boundary conditions refer to giving a constraint force to the boundary, usually fixing the five faces of the ground, front, back, left and right, so as to establish the required numerical models under different levels of surrounding rock.

[0076] S2. Based on the numerical models of surrounding rock with different grades, the strength reduction method is adopted to calculate the safety factor of the tunnel face through the finite difference model and the cusp catastrophe model to obtain the surrounding rock pre-reinforcement strategy.

[0077] The surrounding rock pre-reinforcement strategies include no advance support, application of advance pipe-roof support, and application of advance pipe-roof support and face anchor support in sequence.

[0078] S21. Calculate the safety factor of the tunnel face without advance support. If the safety factor of the tunnel face is greater than 1, adopt the surrounding rock pre-reinforcement strategy without advance support, and no pre-reinforcement of the surrounding rock is required. If the safety factor of the tunnel face is less than or equal to 1, execute step S22.

[0079] S22. Calculate the safety factor of the tunnel face under the application of advanced pipe-roof support. If the safety factor of the tunnel face is greater than 1, adopt the surrounding rock pre-reinforcement strategy of applying advanced pipe-roof support. In this case, it is necessary to drive the pipe-roof into the surrounding rock and inject grouting to pre-reinforce the surrounding rock with the advanced pipe-roof support. If the safety factor of the tunnel face is less than or equal to 1, execute step S23.

[0080] S23. Calculate the safety factor of the tunnel face under the sequential application of advanced pipe-roof support and tunnel face anchor support. If the tunnel face safety factor is greater than 1, adopt the surrounding rock pre-reinforcement strategy of sequentially applying advanced pipe-roof support and tunnel face anchor support. In this case, the pipe-roof and anchors need to be driven into the surrounding rock in sequence to pre-reinforce the surrounding rock with the advanced pipe-roof support and tunnel face anchor support.

[0081] The tunnel face safety factor is set as 1. When the tunnel face safety factor is greater than 1, the surrounding rock pre-reinforcement strategy adopted is considered safe. When the tunnel face safety factor is less than or equal to 1, the surrounding rock pre-reinforcement strategy adopted is considered unsafe.

[0082] By successively calculating the tunnel face safety factor without advance support, the tunnel face safety factor with advance pipe-roof support, and the tunnel face safety factor with advance pipe-roof support and tunnel face anchor support, a surrounding rock pre-reinforcement strategy suitable for the current surrounding rock geological conditions is obtained based on the tunnel face safety factor. The surrounding rock pre-reinforcement strategy can be dynamically adjusted according to different surrounding rock geological conditions, and real-time effective pre-reinforcement of the surrounding rock can be achieved through a real-time surrounding rock pre-reinforcement strategy.

[0083] The calculation of the safety factor of the tunnel face includes the following steps:

[0084] S211. Based on the numerical models of surrounding rock of different grades, the preset initial reduction coefficients and the preset change values of the reduction coefficients, a strength reduction method is adopted to obtain several reduction coefficients and the tunnel face displacements corresponding to the several reduction coefficients through a finite difference model.

[0085] First, a small initial reduction factor is preset. This initial reduction factor, along with the cohesion and internal friction angles of the numerical model for different rock mass grades, is input into a finite-difference model (FLAC3D). The finite-difference model calculates the extrusion deformation of a tunnel face under this initial reduction factor and outputs the tunnel face displacement under this initial reduction factor, i.e., the tunnel face displacement corresponding to the initial reduction factor. Within the finite-difference model, the displacement of the extracted elements is monitored using the FISH language. The element with the largest tunnel face displacement is selected, typically at the center of the tunnel face, which is often most susceptible to instability. The displacement of this point is then retrieved to obtain the tunnel face displacement under this initial reduction factor.

[0086] Then, the strength reduction method is adopted, a reduction coefficient change value is preset, and the loop command in the finite difference model is used to gradually increase the reduction coefficient change value on the initial reduction coefficient so that the reduction coefficient increases in value. That is, starting from the initial reduction coefficient, a reduction coefficient change value is added to the previous reduction coefficient to generate several reduction coefficients.

[0087] When the reduction coefficient increases, the cohesion and internal friction angle of the numerical model under different grades of surrounding rock are reduced synchronously, that is, a process of simulating the change of the surrounding rock's own strength after excavation is carried out. In this process, the cohesion and internal friction angle of the rock mass are continuously weakened, and the reduced cohesion and internal friction angle corresponding to several reduction coefficients are generated.

[0088] The reduction formula of cohesion is:

[0089]

[0090] Among them, F is the reduction factor, C is the cohesion, and C F is the reduced cohesive strength.

[0091] The reduction formula of internal friction angle is:

[0092]

[0093] in, is the internal friction angle, F is the reduction coefficient, is the reduced internal friction angle.

[0094] Finally, based on several reduction coefficients and the reduced cohesion and internal friction angle corresponding to the reduction coefficients, the tunnel face displacements corresponding to the reduction coefficients are obtained through the finite difference model.

[0095] S212. Performing quadratic polynomial fitting on the reduction coefficients and the tunnel face displacements corresponding to the reduction coefficients to obtain quadratic polynomials of the tunnel face displacements, and generating a quadratic polynomial fitting curve based on the quadratic polynomials of the tunnel face displacements.

[0096] The reduction coefficient and the tunnel face displacement corresponding to the reduction coefficient are fitted with a fourth-order polynomial using the polyfit function in the Mat Lab software. That is, the fourth-order polynomial of the tunnel face displacement is obtained by fitting using the least squares method. The expression of the fourth-order polynomial of the tunnel face displacement is:

[0097] S=a4F 4 +a3F 3 +a2F 2 +a1F+a0,

[0098] Where F is the reduction coefficient, S is the tunnel face displacement corresponding to the reduction coefficient, and ɑ1, ɑ2, ɑ3, and ɑ4 are the coefficients of each polynomial obtained by fitting the reduction coefficient F and the tunnel face displacement S corresponding to the reduction coefficient into a fourth-order polynomial.

[0099] A fourth-order polynomial fitting is performed on each reduction coefficient and the tunnel face displacement corresponding to the reduction coefficient to obtain several fourth-order polynomials of the tunnel face displacement, and a fourth-order polynomial fitting curve is generated based on the several fourth-order polynomials of the tunnel face displacement.

[0100] A quartic polynomial is obtained through quartic polynomial fitting, which can be converted into the standard potential function of the cusp catastrophe model. Only by converting the quartic polynomial into the standard potential function of the cusp catastrophe model can the displacement mutation point be found through the cusp catastrophe model. Therefore, it is necessary to fit the reduction coefficient and the tunnel face displacement corresponding to the reduction coefficient with a quartic polynomial.

[0101] S213. Linearly transforming the quadratic polynomials of the several face displacements to obtain several standard potential functions of the cusp catastrophe model, and obtaining several control variable u values and several control variable v values based on the several standard potential functions of the cusp catastrophe model.

[0102] The fourth-order polynomial of each tunnel face displacement is linearly changed to obtain several standard potential functions of the cusp catastrophe model.

[0103] The expression of the standard potential function of the cusp catastrophe model is:

[0104] S'=p 4 +up 2 +vp+c,

[0105] Among them, p is the intermediate variable in the linear change process, c is the constant term, S′ is an equation of the standard potential function expression of the cusp catastrophe model obtained after the linear change, and u and v are the control variables in the standard potential function of the cusp catastrophe model obtained after the linear change.

[0106] The values of the control variables u and v are directly obtained from the expression of the standard potential function of the cusp catastrophe model.

[0107] S214. Based on the multiple control variable u values and the multiple control variable v values, obtain multiple discriminant values under the tunnel face displacement corresponding to the reduction coefficient through the cusp catastrophe model discriminant.

[0108] The formula for the discriminant of the cusp catastrophe model is:

[0109] Δ=8u 3 +27v 2 ,

[0110] Among them, Δ is the discrimination value.

[0111] The origin of the cusp catastrophe model discriminant is:

[0112] The expression of the standard potential function of the theoretical cusp catastrophe model is:

[0113] V(x)=x 4 +ux 2 +vx,

[0114] Among them, u and v are the control variables of the cusp catastrophe model; x is the state variable of the cusp catastrophe model.

[0115] The equilibrium equation of the cusp catastrophe model can be obtained by transforming the standard potential function of the cusp catastrophe model. The expression of the equilibrium equation of the cusp catastrophe model is:

[0116]

[0117] Among them, u and v are the control variables of the cusp catastrophe model; x is the state variable of the cusp catastrophe model. The equilibrium equation of the cusp catastrophe model is expressed as a wrinkled curve in the (x, u, v) space, that is, the cusp equilibrium surface and bifurcation set, such as Figure 4 shown.

[0118] The discriminant of the cusp catastrophe model is obtained by eliminating x by setting the standard potential function of the cusp catastrophe model to zero and the equilibrium equation of the cusp catastrophe model to zero.

[0119] S215. Based on a plurality of discriminant values under the tunnel face displacement corresponding to the reduction coefficient, the mutation point of the numerical model under different grades of surrounding rock is determined, and the reduction coefficient corresponding to the mutation point is used as the tunnel face safety factor.

[0120] If the discriminant value is greater than zero, the numerical model under different grades of surrounding rock is judged to be in a stable state. If the discriminant value is less than or equal to zero, the numerical model under different grades of surrounding rock is judged to be in an unstable state. Among several discriminant values under the tunnel face displacement corresponding to the reduction coefficient, the reduction coefficient corresponding to the positive discriminant value where the discriminant value changes from positive to negative is judged to be the mutation point of the numerical model under different grades of surrounding rock. At this time, the reduction coefficient is used as the tunnel face safety factor.

[0121] S3. Perform real-time pre-reinforcement of the surrounding rock according to the surrounding rock pre-reinforcement strategy.

[0122] According to the surrounding rock pre-reinforcement strategy, a multi-arm drilling rig is used for rapid positioning, mechanized automatic drilling, and rapid installation of pre-reinforcement components, improving construction efficiency and reinforcement effects, and completing real-time and effective pre-reinforcement.

[0123] The present invention also relates to a surrounding rock pre-reinforcement system, such as Figure 5 As shown, a surrounding rock pre-reinforcement method for the above-mentioned surrounding rock comprises:

[0124] The real-time data acquisition module is used to obtain the real-time tunnel face surrounding rock grade and rock mass parameters, including elastic modulus, cohesion, and internal friction angle; based on the real-time tunnel face surrounding rock grade and rock mass parameters, numerical models for different grades of surrounding rock are constructed;

[0125] The reduction module is used to obtain several reduction coefficients and the corresponding tunnel face displacements of the reduction coefficients based on the numerical models of different grades of surrounding rock, the preset initial reduction coefficients and the preset change value of the reduction coefficients by using the strength reduction method and the finite difference model;

[0126] A polynomial fitting module is used to perform fourth-order polynomial fitting on a plurality of reduction coefficients and the tunnel face displacements corresponding to the plurality of reduction coefficients, thereby obtaining a plurality of fourth-order polynomials of the tunnel face displacements;

[0127] A conversion module is used to linearly transform a plurality of quadratic polynomials of face displacement to obtain a plurality of standard potential functions of cusp catastrophe models, and to obtain a plurality of control variable u values and a plurality of control variable v values based on the plurality of standard potential functions of cusp catastrophe models;

[0128] The discriminant module is used to calculate the tunnel face safety factor based on several control variable u values and several control variable v values through the cusp catastrophe model discriminant formula, and obtain the surrounding rock pre-reinforcement strategy according to the tunnel face safety factor;

[0129] The pre-reinforcement module is used to perform real-time pre-reinforcement of surrounding rock according to the surrounding rock pre-reinforcement strategy.

[0130] Example 2

[0131] A specific implementation of a surrounding rock pre-reinforcement method includes:

[0132] S1. The real-time tunnel face surrounding rock grade obtained from the tunnel surrounding rock is Grade 5. The rock mass parameters include an elastic modulus of 300 MPa, cohesion of 50 kPa, and an internal friction angle of 20°. Based on the real-time tunnel face surrounding rock grade and rock mass parameters, a numerical model for Grade 5 surrounding rock conforming to the Mohr-Coulomb constitutive model was constructed.

[0133] S2. Based on the numerical model of the fifth-level surrounding rock, the strength reduction method is used to calculate the safety factor of the tunnel face without advanced support through the finite difference model and the cusp catastrophe model. The fourth-order polynomial fitting curve without advanced support can be obtained, where the horizontal axis represents the reduction coefficient F and the vertical axis represents the tunnel face displacement S corresponding to the reduction coefficient, as shown in the figure. Figure 6 As shown in Table 1, the discrimination values of tunnel face displacement corresponding to different reduction coefficients without advanced support can be obtained.

[0134] Table 1 Discriminant values of tunnel face displacement corresponding to different reduction coefficients without advance support

[0135] F S / mm Δ 0.64 108.25 1.57E-10 0.66 134.362 1.2E-10 0.68 163.377 -8.2E-08 0.70 196.244 -1.7563

[0136] It can be seen from Table 1 that when the reduction coefficient F = 0.66, the discriminant value is greater than 0, and when the reduction coefficient F = 0.68, the discriminant value is less than 0. Therefore, the reduction coefficient of 0.66 corresponding to the positive discriminant value where the discriminant value changes from positive to negative is judged as the mutation point of the numerical model under the fifth-level surrounding rock. At this time, 0.66 is used as the safety factor of the tunnel face.

[0137] It can be seen from this that the safety factor of the tunnel face without advance support is 0.66, which is less than 1. Therefore, the surrounding rock pre-reinforcement strategy without advance support cannot be adopted and the next step should be executed.

[0138] S3. Based on the numerical model of the fifth-level surrounding rock, the strength reduction method is used to calculate the safety factor of the tunnel face under the application of advanced pipe-roof support through the finite difference model and the cusp catastrophe model. The fourth-order polynomial fitting curve under the application of advanced pipe-roof support can be obtained, where the horizontal axis represents the reduction coefficient F and the vertical axis represents the tunnel face displacement S corresponding to the reduction coefficient, as shown in the figure. Figure 7 As shown in Table 2, the discrimination values of tunnel face displacement corresponding to different reduction coefficients under the application of advanced pipe-roof support can be obtained.

[0139] Table 2 Discrimination values of tunnel face displacement corresponding to different reduction coefficients under advanced pipe-roof support

[0140] F S / mm Δ 0.70 139.49 8.84E-06 0.72 164.13 1.23E-05 0.74 189.69 -3.5E-04 0.76 216.74 -1.48034

[0141] It can be seen from Table 2 that when the reduction coefficient F = 0.72, the discriminant value is greater than 0, and when the reduction coefficient F = 0.74, the discriminant value is less than 0. Therefore, the reduction coefficient of 0.72 corresponding to the positive discriminant value where the discriminant value changes from positive to negative is judged as the mutation point of the numerical model under the fifth-level surrounding rock. At this time, 0.72 is used as the safety factor of the tunnel face.

[0142] It can be seen from this that when the safety factor of the tunnel face with the advanced pipe-roof support is 0.72 and is less than 1, the surrounding rock pre-reinforcement strategy with the advanced pipe-roof support cannot be adopted and the next step should be executed.

[0143] S4. Based on the numerical model of the fifth-level surrounding rock, the strength reduction method is used to calculate the safety factor of the tunnel face under the sequential application of advanced pipe-roof support and tunnel face anchor support through the finite difference model and the cusp catastrophe model. The fourth-order polynomial fitting curve under the sequential application of advanced pipe-roof support and tunnel face anchor support can be obtained, where the abscissa represents the reduction coefficient F and the ordinate represents the tunnel face displacement S corresponding to the reduction coefficient, as shown in the figure. Figure 8 As shown in Table 3, the discrimination values under tunnel face displacement corresponding to different reduction coefficients under the application of advanced pipe-roof support and tunnel face anchor support can be obtained.

[0144] Table 3. Discrimination values of tunnel face displacement corresponding to different reduction coefficients when advanced pipe-roof support and tunnel face anchor support are applied in sequence.

[0145]

[0146]

[0147] It can be seen from Table 3 that when the reduction coefficient F = 1.02, the discriminant value is greater than 0, and when the reduction coefficient F = 1.04, the discriminant value is less than 0. Therefore, the reduction coefficient of 1.02 corresponding to the positive discriminant value where the discriminant value changes from positive to negative is judged as the mutation point of the numerical model under the fifth-level surrounding rock. At this time, 1.02 is used as the safety factor of the tunnel face.

[0148] It can be seen from this that when the safety factor of the tunnel face is 1.02 greater than 1 under the sequential application of advanced pipe-roof support and tunnel face anchor support, the surrounding rock pre-reinforcement strategy of sequentially applying advanced pipe-roof support and tunnel face anchor support is adopted. In this case, the pipe-roof and anchor bolts need to be driven into the surrounding rock in sequence to pre-reinforce the surrounding rock with advanced pipe-roof support and tunnel face anchor support.

[0149] S5. Using a three-arm hydraulic fully automatic rock drilling rig, according to the surrounding rock pre-reinforcement strategy of sequentially applying advanced pipe-roof support and face anchor support, rapid positioning and automatic drilling are carried out to drive the pipe-roof and anchor bolts into the surrounding rock in sequence, completing real-time and effective pre-reinforcement.

[0150] Therefore, when the surrounding rock grade of the tunnel face is level five, the elastic modulus is 300 MPa, the cohesion is 50 kPa, and the internal friction angle is 20°, a surrounding rock pre-reinforcement strategy of sequentially applying advanced pipe-roof support and tunnel face anchor support is adopted to achieve real-time and effective pre-reinforcement.

[0151] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A surrounding rock pre-reinforcement method, characterized in that: include: Obtaining real-time tunnel face surrounding rock grade and rock mass parameters, including elastic modulus, cohesion, and internal friction angle; Construct numerical models of surrounding rock with different grades based on real-time tunnel face surrounding rock grades and rock mass parameters; Based on numerical models of surrounding rock of different grades, the strength reduction method is used to calculate the safety factor of the tunnel face through the finite difference model and the cusp catastrophe model to obtain the surrounding rock pre-reinforcement strategy; The surrounding rock is pre-reinforced in real time according to the surrounding rock pre-reinforcement strategy.

2. The surrounding rock pre-reinforcement method according to claim 1, characterized in that: The surrounding rock pre-reinforcement strategies include no advance support, applying advance pipe-roof support, and applying advance pipe-roof support and tunnel face anchor support in sequence.

3. A surrounding rock pre-reinforcement method according to claim 2, characterized in that: The method of calculating the safety factor of the tunnel face to obtain the surrounding rock pre-reinforcement strategy includes the following steps: S1. Calculate the safety factor of the tunnel face without advance support. If the safety factor of the tunnel face is greater than 1, adopt the surrounding rock pre-reinforcement strategy without advance support. If the safety factor of the tunnel face is less than or equal to 1, execute step S2. S2. Calculate the safety factor of the tunnel face under the application of advanced pipe-roof support. If the safety factor of the tunnel face is greater than 1, adopt the surrounding rock pre-reinforcement strategy of applying advanced pipe-roof support. If the safety factor of the tunnel face is less than or equal to 1, execute step S3. S3. Calculate the tunnel face safety factor when applying advanced pipe-roof support and tunnel face anchor support in sequence. If the tunnel face safety factor is greater than 1, adopt the surrounding rock pre-reinforcement strategy of applying advanced pipe-roof support and tunnel face anchor support in sequence.

4. A surrounding rock pre-reinforcement method according to claim 3, characterized in that: The calculation of the safety factor of the tunnel face comprises the following steps: S11. Based on the numerical models of surrounding rock of different grades, the preset initial reduction coefficients and the preset variation of the reduction coefficients, a strength reduction method is used to obtain a number of reduction coefficients and the corresponding tunnel face displacements through a finite difference model; S12, performing quadratic polynomial fitting on a plurality of reduction coefficients and the tunnel face displacements corresponding to the plurality of reduction coefficients, respectively, to obtain a plurality of quadratic polynomials of the tunnel face displacements; S13, linearly changing a plurality of quadratic polynomials of face displacement to obtain a plurality of standard potential functions of the cusp catastrophe model, and obtaining a plurality of control variable u values and a plurality of control variable v values based on the plurality of standard potential functions of the cusp catastrophe model; S14. Based on the values of the plurality of control variables u and the values of the plurality of control variables v, a plurality of discriminant values under the tunnel face displacement corresponding to the reduction coefficient are obtained by using the discriminant of the cusp catastrophe model; S15. Based on a plurality of discriminant values under the tunnel face displacement corresponding to the reduction coefficient, the mutation point of the numerical model under different grades of surrounding rock is determined, and the reduction coefficient corresponding to the mutation point is used as the tunnel face safety factor.

5. The surrounding rock pre-reinforcement method according to claim 4, characterized in that: The strength reduction method comprises: Based on the initial reduction coefficient and the change value of the reduction coefficient, the change value of the reduction coefficient is gradually increased on the initial reduction coefficient through a finite difference model, so that the reduction coefficient increases in equal value, thereby generating several reduction coefficients; When the reduction coefficient increases, the cohesion and the internal friction angle are reduced synchronously to generate a number of reduced cohesion and internal friction angles corresponding to the reduction coefficients.

6. A surrounding rock pre-reinforcement method according to claim 5, characterized in that: Obtaining the tunnel face displacements corresponding to the reduction coefficients includes: Based on several reduction coefficients and the reduced cohesion and internal friction angle corresponding to the reduction coefficients, the tunnel face displacements corresponding to the reduction coefficients are obtained through the finite difference model.

7. The surrounding rock pre-reinforcement method according to claim 5, characterized in that: The reduction formula for reducing the cohesion and internal friction angle is: Among them, F is the reduction factor, C is the cohesion, and C F is the reduced cohesive strength, is the internal friction angle, is the reduced internal friction angle.

8. The surrounding rock pre-reinforcement method according to claim 4, characterized in that: The expression of the fourth-order polynomial of the tunnel face displacement is: <h2 style=";text-align:left;direction:ltr">S=a4F<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> +a3F<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +a2F<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a1F+a0, Where F is the reduction coefficient, S is the tunnel face displacement corresponding to the reduction coefficient, and ɑ1, ɑ2, ɑ3, and ɑ4 are the coefficients of each polynomial obtained by fitting the reduction coefficient F and the tunnel face displacement S corresponding to the reduction coefficient into a fourth-order polynomial.

9. The surrounding rock pre-reinforcement method according to claim 4, characterized in that: The expression of the standard potential function of the cusp catastrophe model is: S'=p 4 +up 2 +vp+c, Among them, p is the intermediate variable in the linear change process, c is the constant term, S′ is an equation of the standard potential function expression of the cusp catastrophe model obtained after the linear change, and u and v are the control variables in the standard potential function of the cusp catastrophe model obtained after the linear change.

10. A surrounding rock pre-reinforcement system, characterized in that: A surrounding rock pre-reinforcement method according to any one of claims 1 to 9, comprising: A real-time data acquisition module is used to obtain real-time tunnel face surrounding rock grade and rock mass parameters, including elastic modulus, cohesion, and internal friction angle; and to construct numerical models for different grades of surrounding rock based on the real-time tunnel face surrounding rock grade and rock mass parameters; The reduction module is used to obtain several reduction coefficients and the corresponding tunnel face displacements of the reduction coefficients based on the numerical models of different grades of surrounding rock, the preset initial reduction coefficients and the preset change value of the reduction coefficients by using the strength reduction method and the finite difference model; A polynomial fitting module is used to perform fourth-order polynomial fitting on a plurality of reduction coefficients and the tunnel face displacements corresponding to the plurality of reduction coefficients, thereby obtaining a plurality of fourth-order polynomials of the tunnel face displacements; A conversion module is used to linearly transform a plurality of quadratic polynomials of face displacement to obtain a plurality of standard potential functions of cusp catastrophe models, and to obtain a plurality of control variable u values and a plurality of control variable v values based on the plurality of standard potential functions of cusp catastrophe models; The discriminant module is used to calculate the tunnel face safety factor based on several control variable u values and several control variable v values through the cusp catastrophe model discriminant formula, and obtain the surrounding rock pre-reinforcement strategy according to the tunnel face safety factor; The pre-reinforcement module is used to perform real-time pre-reinforcement of surrounding rock according to the surrounding rock pre-reinforcement strategy.

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