Method and device for analyzing stability of advanced core soil of tunnel face

Abstract

The invention provides a tunnel face advanced core soil stability analysis method considering a spatial effect, which is based on a traditional prism-wedge model and aims at the problem of non-uniform distribution of surrounding rock stress in a tunnel excavation process, and virtual support force and a vertical deformation pressure reduction coefficient are introduced into the model. The method comprises the following steps: setting a hypothesis condition, and establishing a tunnel face stability analysis model based on a prism-wedge model; determining a tunnel face core soil stability coefficient by solving the tunnel face stability analysis model; and determining the stability degree of the current tunnel face core soil by using the stability coefficient of the tunnel face core soil, and determining advance support measures according to the stability degree. The method is simple in structure and convenient to calculate, the model prediction precision is effectively improved, a reliable theoretical basis is provided for tunnel support design and construction parameter optimization, and the method has a good engineering application prospect.

Description

Technical Field

[0001] The present application relates to the technical fields of tunnel engineering and rock and soil mechanics, and in particular to a method and device for analyzing the stability of advanced core soil of a tunnel face. Background Art

[0002] During tunnel construction, the tunnel face, as a critical component directly bearing the excavation load, has a direct impact on the safety of the entire tunnel project. Traditional tunnel face stability analysis methods typically assume that the surrounding rock load is uniformly distributed, ignoring spatial effects caused by factors such as geological conditions, tunnel cross-section shape, and load distribution. In actual projects, the surrounding rock stress is dynamically released after excavation, and due to spatial effects, the surrounding rock pressure in front of the tunnel face is reduced, resulting in large deviations in the traditional model when predicting core soil stability. Although some studies have used numerical simulation and limit equilibrium methods to analyze advance support, they still do not fully consider spatial effects. Therefore, a new stability analysis method is urgently needed to accurately calculate the stability of the tunnel face core soil by considering spatial effects, providing a theoretical basis for the design of advance support measures (such as anchor support, pipe roof reinforcement, and pre-grouting reinforcement). Summary of the Invention

[0003] In view of the above problems, the embodiments of the present application provide a method and device for analyzing the stability of the advanced core soil of the tunnel face taking into account the spatial effect, which is used to accurately describe the complex state of the surrounding rock stress and local deformation of the tunnel face after tunnel excavation, and guide the optimal design of the support structure to overcome the above problems or at least partially solve the above problems.

[0004] In a first aspect, an embodiment of the present application provides a method for analyzing the stability of advanced core soil of a tunnel face taking into account spatial effects, the method comprising:

[0005] Establish a tunnel face stability analysis model based on the prism-wedge model;

[0006] Determine the values ​​of key parameters of the tunnel face stability analysis model;

[0007] Solve the tunnel face stability analysis model based on the values ​​of key parameters and determine the tunnel face core soil stability coefficient;

[0008] For the tunnel face where the core soil stability coefficient is less than the stability threshold, advance support measures are implemented.

[0009] Optionally, establishing a tunnel face stability analysis model based on a prism-wedge model includes:

[0010] Considering the spatial effect during face excavation, the assumptions for the tunnel face stability analysis model are set;

[0011] Based on the classic prism-wedge model, a tunnel face stability analysis model is established which considers the combined effects of tunnel face spatial effect and advance support.

[0012] Optionally, the tunnel face stability analysis model is:

[0013]

[0014] F q =α(x)qB(Dcotθ0+L e )

[0015] Where K is the stability coefficient of the core soil of the tunnel face; θ0 is the angle between the failure surface of the tunnel face and the horizontal; is the internal friction angle of the surrounding rock; P1 is the support force provided by the anchor; α(x) is the vertical deformation pressure reduction coefficient considering the spatial effect; α1 is the vertical deformation pressure reduction coefficient of the disturbed section in front of the tunnel face under pipe-roof support; α2 is the cohesion increase coefficient of the surrounding rock under pre-grouting reinforcement; F c F is the resultant force of the sliding surface cohesion of the tunnel face; w is the deadweight of the sliding body on the tunnel face; F q is the resultant vertical deformation pressure above the sliding body on the tunnel face; q is the vertical deformation pressure; α=1.38; H is the tunnel depth; B is the tunnel face span; D is the tunnel face height; L e is the length of the unsupported section of the tunnel; β1, β2, β3 are Correlation coefficient; c / (kPa) is the initial cohesion of surrounding rock; γ / (kN / m 3 ) is the surrounding rock weight.

[0016] Optionally, determining the values ​​of key parameters of the tunnel face stability analysis model includes:

[0017] Determine the equivalent stress release rate in the trapezoidal load distribution of the sliding body on the tunnel face;

[0018] Based on the equivalent stress release rate, vertical deformation pressure, tunnel face span, and tunnel face height, the resultant vertical deformation pressure above the tunnel face sliding body is determined;

[0019] Based on the bolt support resultant force of each row on the tunnel face, the bolt support resultant force of all rows on the tunnel face is determined by summing them up;

[0020] According to the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face, the vertical pressure reduction coefficient of the pipe roof is determined;

[0021] The cohesion increase coefficient is determined based on the cohesion of the pre-grouting slurry and the grouting filling rate.

[0022] Optionally, the vertical pressure reduction coefficient of the pipe roof is determined based on the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face, including:

[0023] The pipe roof is discretized into n micro-ends, and the differential equation of the two-parameter elastic foundation beam is established;

[0024] Convert the differential equation of the two-parameter elastic foundation beam into a finite difference equation;

[0025] Based on the boundary conditions at both ends of the pipe roof, the pipe roof foundation reaction force at each node is determined according to the finite difference equation;

[0026] According to the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face, the vertical pressure reduction coefficient of the pipe roof is divided into two sections, and the vertical pressure reduction coefficient of the pipe roof is determined.

[0027] In a second aspect, an embodiment of the present application provides a device for analyzing the stability of advanced core soil of a tunnel face, the device comprising:

[0028] The model building module is used to set assumptions and establish a tunnel face stability analysis model based on the prism-wedge model;

[0029] A parameter determination module is used to determine the values ​​of key parameters of the tunnel face stability analysis model;

[0030] A calculation module is used to solve the tunnel face stability analysis model based on the values ​​of key parameters and determine the stability coefficient of the core soil of the tunnel face;

[0031] The analysis module implements advanced support measures for the tunnel face where the core soil stability coefficient is less than the stability threshold.

[0032] Optionally, the parameter determination module includes:

[0033] The first parameter determination unit is used to determine the equivalent stress release rate in the trapezoidal load distribution of the sliding body on the tunnel face;

[0034] The second parameter determination unit is used to determine the vertical deformation pressure resultant above the tunnel face sliding body based on the equivalent stress release rate, the vertical deformation pressure, the tunnel face span, and the tunnel face height;

[0035] A third parameter determination unit is configured to determine the resultant force of all rows of anchor support on the tunnel face by summing the resultant force of anchor support on each row of the tunnel face;

[0036] The fourth parameter determination unit determines the pipe roof vertical pressure reduction coefficient based on the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face;

[0037] The fifth parameter determination unit determines a cohesion increase coefficient based on the cohesion of the pre-grouting slurry and the grouting filling rate.

[0038] The specific beneficial effects are:

[0039] By incorporating a spatial effect reduction factor into the prism-wedge model, this embodiment of the present application accurately reflects the dynamic changes in surrounding rock stress after tunnel excavation and the reduction effect of spatial effects on face pressure, thereby improving the accuracy of core soil stability prediction at the face. Compared with traditional methods, this invention can increase the stability factor by an average of 40% to 60% (the specific value is determined by engineering parameters), providing a scientific basis for the optimized design of tunnel support structures and significantly improving the safety and economic efficiency of tunnel construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0041] Figure 1 This is a flow chart of a method for analyzing the stability of advanced core soil at a tunnel face provided by an embodiment of the present application;

[0042] Figure 2 This is the structural diagram of the classic prism-wedge model;

[0043] Figure 3 is a structural diagram of a tunnel face stability analysis model provided in an embodiment of the present application;

[0044] Figure 4 A schematic diagram of a rectangular coordinate system established when determining the vertical deformation pressure reduction coefficient provided in an embodiment of the present application;

[0045] Figure 5 The calculation model of the tunnel face under the tunnel face anchor reinforcement provided in the embodiment of the present application;

[0046] Figure 6 This is the discretization result of the dual-parameter elastic foundation beam provided in the embodiment of this application. DETAILED DESCRIPTION

[0047] The exemplary embodiments of the present application will be described in more detail below in conjunction with the accompanying drawings in the embodiments of the present application. Although the accompanying drawings show exemplary embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0048] After tunnel excavation, surrounding rock stress is not released all at once but rather develops dynamically. Virtual support forces provide support for the tunnel chamber and a certain distance in front of the tunnel face (i.e., in the direction of excavation). These forces decrease from a certain distance in front of the tunnel face to the rear. This results in an increasing load on the sliding mass at the tunnel face, rather than the uniformly distributed load in traditional models. Virtual support forces are imaginary forces introduced through numerical models to simulate the influence of support structures on surrounding rock stability. They do not represent actual physical forces but rather a mathematical approximation of the support effect.

[0049] In order to accurately reflect the dynamic release and spatial effect of surrounding rock stress during tunnel excavation, this paper introduces virtual support force and deformation pressure reduction coefficient based on the traditional prism-wedge model to analyze the stability of the core soil at the tunnel face. Figure 1 , Figure 1 A schematic flow chart of a method for analyzing the stability of advanced core soil at a tunnel face provided in an embodiment of the present application, wherein the method may include:

[0050] Step 101: Set assumptions and establish a tunnel face stability analysis model based on a prism-wedge model.

[0051] In the embodiments of this application, since the existing technology does not fully consider the spatial effects during tunnel face excavation, especially the dynamic changes in surrounding rock pressure after tunnel excavation, the assumptions for the tunnel face stability analysis model are set, including:

[0052] Assumption 1: The tunnel face is completely destroyed;

[0053] Assumption 2: The angle between the failure plane of the tunnel face and the horizontal direction is θ0, in, is the internal friction angle of the surrounding rock;

[0054] Assumption 3: The surrounding rock satisfies the Mohr-Coulomb strength criterion.

[0055] The classic prism-wedge model consists of a wedge and a prism above it, such as Figure 2 As shown in the figure, D is the tunnel face height (when the micro-step method is used, D is the tunnel face height of the upper step), B is the tunnel face span, L eis the length of the unsupported section.

[0056] Based on the evolution characteristics of the spatial effect and on the basis of the classic prism-wedge model, a tunnel face stability analysis model considering the combined effects of the tunnel face spatial effect and advance support is established. Figure 3 shown.

[0057] The evolution characteristics include the evolution of the displacement release rate δ(x), the virtual support force P(x), and the deformation pressure reduction coefficient α(x) with the excavation distance x.

[0058] The expression of the tunnel face stability analysis model is:

[0059]

[0060] F q =α(x)qB(Dcotθ0+L e )(4)

[0061] Where K represents the stability coefficient of the core soil of the tunnel face; P1 / (kN) is the support force provided by the anchor; α(x) is the vertical deformation pressure reduction coefficient considering the spatial effect; α1 is the vertical deformation pressure reduction coefficient of the disturbed section in front of the tunnel face under pipe-roof support; α2 is the cohesion increase coefficient of the surrounding rock under pre-grouting reinforcement; F c / (kN) is the resultant force of the sliding surface cohesion of the tunnel face; F w / (kN) is the deadweight of the sliding body on the tunnel face; F q / (kN) is the resultant vertical deformation pressure above the sliding body on the tunnel face; q / (kPa) is the vertical deformation pressure; α=1.38; H / (m) is the tunnel depth; B / (m) is the tunnel face span; D / (m) is the tunnel face height; L e / (m) is the length of the unsupported section of the tunnel; β1, β2, β3 are Correlation coefficient; c / (kPa) is the initial cohesion of surrounding rock; γ / (kN / m 3 ) is the surrounding rock weight.

[0062] exist Figure 3 In the figure, P1 represents the characteristic point related to the load borne by the sliding body at the tunnel face. When considering spatial effects, the load distribution is adjusted by introducing a vertical deformation pressure reduction factor. The value of P1 reflects the stress release of the surrounding rock during excavation and provides a key parameter for stability analysis. Figure 3 The dotted line part in the figure represents the supporting effect of the virtual support force on the sliding body load.

[0063] The derivation process of the calculation formula of the core soil stability coefficient K of the tunnel face is given below:

[0064] 1) According to the limit equilibrium method, the calculation formula for the stability coefficient of the core soil of the tunnel face is obtained as follows:

[0065]

[0066] Where K is the stability coefficient of the core soil at the tunnel face; F1 and F2 are the anti-sliding force and sliding force along the failure surface respectively;

[0067] 2) According to the static equilibrium conditions in the vertical and horizontal directions, we can obtain:

[0068] P1+Tcosθ0=Nsinθ0(6)

[0069] α1F q +F w -Tsinθ0=Ncosθ0 (7)

[0070] Wherein, N is the normal force acting on the sliding surface;

[0071] Combining equations (6) and (7), we can obtain:

[0072] N=cosθ0(α1F q +F w )+sinθ0P1 (8)

[0073] 3) According to the shear force formula of the Mohr-Coulomb criterion, the shear force T of the slip surface can be obtained based on formula (8):

[0074]

[0075] Where: F c is the resultant cohesive force of the sliding surface of the wedge.

[0076] 4) According to formula (9), the forces can be decomposed along the tangential direction of the slip surface to obtain:

[0077] F1=T+cosθ0P1(10)

[0078] F2=sinθ0(α1F q +F w ) (11)

[0079] Substituting the shear force T into F1, we can obtain:

[0080]

[0081] 5) Substituting equations (12) and (11) back into equation (5) and simplifying them, we can obtain:

[0082]

[0083] In order to simplify Equation (13), define β1, β2, β3:

[0084]

[0085] Among them, β1, β2, β3 are correlation coefficients, and they are all related to Related;

[0086] 6) Substitute equations (14) to (16) into equation (13), simplify equation (13), and finally obtain the calculation formula for the core soil stability coefficient K of the tunnel face:

[0087]

[0088] Based on Figure 2 The geometric parameters of the prism-wedge model (D, B, L e ) can be concluded:

[0089]

[0090] F q =α(x)qB(Dcotθ0+L e )

[0091] Thus, a model that takes into account parameters such as spatial effect, surrounding rock cohesion, and internal friction angle has been established. This model is the calculation model for the stability coefficient K of the core soil of the tunnel face. The stability coefficient K can be calculated using the above formula (1). On this basis, the stability of the tunnel face can be analyzed and compared using the stability coefficient K of the core soil of the tunnel face.

[0092] Step 102: Determine the values ​​of key parameters of the tunnel face stability analysis model; the key parameters include equivalent stress release rate, vertical deformation pressure resultant, face anchor support resultant, pipe roof vertical pressure reduction coefficient, and pre-grouting cohesion enhancement coefficient;

[0093] After the tunnel face stability analysis model is established in step 101, the tunnel face core soil stability coefficient K can be calculated using the model. In order to solve the model, it is necessary to first determine the key parameters in the model. The calculated key parameters are substituted into formula (1) to finally obtain the core soil stability coefficient K. The key parameters include:

[0094] 1) Vertical deformation pressure reduction factor considering spatial effects

[0095] The strength and stiffness of the advanced core soil determine the strength of its support for the tunnel wall in front of the tunnel face, and the support effect affects the variation of the virtual support force. In the embodiment of this application, the equivalent stress release rate δ is defined to measure the variation of the virtual support force, and it is set as:

[0096]

[0097] Where P0 represents the original rock stress, P x Expressed as virtual support force.

[0098] The vertical deformation pressure reduction coefficient α(x) considering the spatial effect reflects the stress release process of the surrounding rock, so it is approximately taken as the equivalent stress release rate δ, and the expression is:

[0099]

[0100] Where, q is the vertical deformation pressure;

[0101] The calculation formula of the core soil stability coefficient K of the tunnel face (Formula 1) and the vertical deformation pressure above the tunnel face sliding body F q The calculation formula (Formula 4) is combined to obtain:

[0102] K=K(x)(19)

[0103] The above formula shows that the stability coefficient K of the core soil of the face is a function of the excavation distance x. Within the range of the independent variable x, the degree of stress release is different, so the stability coefficient K is a range value. However, in reality, the position of the face is fixed, and the stability coefficient K is a range value, which is inconsistent with the actual situation. Therefore, in order to determine the specific K value, it is necessary to find a characteristic point to represent the reduction effect of spatial effect on the surrounding rock pressure. To simplify the calculation, the horizontal coordinate of the trapezoid centroid is used as the characteristic point. When the surrounding rock parameters (i.e., original rock stress, internal friction angle and cohesion) are given, the relationship between the equivalent stress release rate and the distance from the face can be obtained, that is:

[0104] δ=(p0-p x ) / p0

[0105] Through the geometric relationship, the longitudinal length of the sliding body on the tunnel face can be determined, thus providing a basis for determining the equivalent stress release rate. At the same time, ignoring the advanced support structure and only considering the relationship between the load and the sliding body position, the following can be established: Figure 4 The rectangular coordinate system shown.

[0106] Figure 4 In the equation, let point A be a vertex of the sliding body. From the geometric relationship in the prism-wedge model, we can obtain:

[0107] L 楔形体 =Dcotθ0(20)

[0108] Among them, L 楔形体 Indicates the longitudinal length of the sliding body on the tunnel face;

[0109] Based on the above formula, the coordinates of point A are (-Dcotθ0,D), and the corresponding equivalent stress release rate is αA .

[0110] Since the pre-convergence deformation occurs at 1 times the tunnel diameter in front of the face, θ0 is greater than 45°, so no matter what the working condition is, the stress release process has occurred at point A, α A ≠0, that is, α A q>0, so the simplified load distribution is trapezoidal rather than triangular.

[0111] Assume that point C is the vertex of the sliding body at the tunnel face, and its coordinates are (0, D). If there is an unsupported section, the coordinates of point C are (L e ,D), the corresponding equivalent stress release rate is α C ; Let point B be the horizontal coordinate corresponding to the centroid of the trapezoid. From the centroid formula of the right-angled trapezoid, we know that

[0112]

[0113] Among them, L BC Represents the distance between point B and point C;

[0114] According to formula (21), the coordinates of the centroid point B are From this we can make:

[0115] α0=α(x)=α(x B )=δ B (twenty two)

[0116] Where α0 represents the equivalent stress release rate in the trapezoidal load distribution of the sliding body on the tunnel face; x B represents the abscissa of point B;

[0117] Where, δ B is the equivalent stress release rate corresponding to point B.

[0118] According to formula (22) and formula (4), F q The calculation formula is:

[0119] F q =α0qB(Dcotθ0+L e )(twenty three)

[0120] Therefore, we can solve F in equation (4) by (23). q , when F is determined q Then combine the stability coefficients K and F c and F w The relevant formula can be used to calculate the stability coefficient K of the core soil of the tunnel face considering the spatial effect of the tunnel face.

[0121] 2) Resultant force of anchor support on the tunnel face

[0122] The interaction between the face anchor and the surrounding rock can reduce the stress loss at the face, effectively increase the minimum principal stress at the face, reduce the extrusion deformation of the core soil at the face, and improve the stability of the surrounding rock. The area in front of the face can be divided into a non-anchored area and an anchored area, such as Figure 5 As shown, face anchor bolts have five failure modes: 1) tensile failure of the anchor bolt at the face failure plane; 2) shear failure of the surrounding rock-grout interface in the non-anchored area; 3) shear failure of the surrounding rock-grout interface in the anchored area; 4) shear failure of the anchor bolt-grout interface in the non-anchored area; and 5) shear failure of the anchor bolt-grout interface in the anchored area. Because face anchor bolts have a short effective anchoring length and are typically used in weak surrounding rock, failure modes 4) and 5) are generally not encountered. Therefore, this paper only considers failure modes 1), 2), and 3).

[0123] Based on the above analysis, the calculation formula for the tunnel face anchor support force P1 under the above failure modes 1)-3) is obtained as follows:

[0124]

[0125] Where: P 1i / (kN) is the resultant force of the i-th row of anchor bolts; n b is the total number of anchor rows.

[0126] exist Figure 5 In, l Ii / (m) is the length of the i-th row of anchors in the non-anchored area, l IIi / (m) is the length of the i-th row of anchor rods in the anchoring area, L b / (m) is the length of the anchor rod, y i / (m) is the vertical coordinate of the i-th row anchor, x i is the horizontal coordinate where the i-th row of anchors intersects the failure surface.

[0127] 3) Pipe roof vertical pressure reduction coefficient

[0128] like Figure 6 As shown, the total length is L p The pipe rack is discretized into n pieces with a length of ΔL p The micro-end is set, and two virtual nodes -2, -1, n+1, and n+2 are set at both ends of the pipe roof. The elastic foundation beam is discretized and a two-parameter elastic foundation beam differential equation is established. The establishment of the two-parameter elastic foundation beam differential equation adopts the establishment method in the existing technology and can be divided into two steps: the first step adopts the Winkler (E.Winkler) model and combines it with the Bernoulli-Euler classical theory to obtain the differential relationship between load, displacement and internal force; the second step is to modify the differential equation obtained in the first step according to the two-parameter model proposed by Pasternak in 1954 to obtain the two-parameter elastic foundation beam differential equation.

[0129] The central point difference is used to transform the differential equation of the two-parameter elastic foundation beam into a finite difference equation. The transformed finite difference equation is:

[0130] C i (ω i+2 -4ω i+1 +6ω i -4ω i-1 +ω i-2 )-D i (6ω i+1 -2ω i +ω i-1 )+B i ω i =q i (25)

[0131] Where:

[0132]

[0133] Among them, D i is the tunnel face height of the i-th node; B i is the span of the tunnel face at the i-th node; ΔL p is the length of each micro-end obtained after the tube roof is discretized; ω i / (m) is the deflection of the i-th node; q i / (kPa) is the load on the i-th node; EI / (N·m 2 ) is the bending stiffness of the pipe shed; b / (m) is the diameter of the pipe shed; b i is the diameter of the pipe roof at the i-th node; S p / (m) is the distance between pipe sheds; k i / (MPa / m) is the base bed coefficient of the i-th node; G p / (MPa) is the shear modulus of surrounding rock; E s / (GPa) is the elastic modulus of the pipe-roof steel pipe; E c / (GPa) is the elastic modulus of the pipe-roof grouting body; I s / (m 4 ) is the moment of inertia of the pipe-roof steel pipe; I c / (m 4 ) is the moment of inertia of the pipe-roof grouting body.

[0134] Combined with the boundary conditions at both ends of the pipe shed (bending moment and shear force are 0), and in parallel with equations (25) and (26), the deflection ω of the i-th node of the pipe shed can be obtained by calculation: i , and then get the deflection ω of the i-th node i The calculation formula of the pipe-roof foundation reaction force at the i-th node is:

[0135]

[0136] According to formula (28) and formula (29), the variable base bed coefficient of the initial support and the variable base bed coefficient of the surrounding rock in front of the tunnel face are calculated respectively. Then, the calculated base bed coefficient is substituted into formula (27) to obtain the foundation reaction force of the pipe-roof at the i-th node.

[0137] The calculation formulas for the initial support variable bed coefficient k(x) and the variable bed coefficient k(x′) of the surrounding rock in front of the tunnel face are as follows:

[0138]

[0139] Among them, x / (d) is the initial support age corresponding to the pipe-roof node; k0=q0 / s0 is the stability value of the initial support base coefficient, in MPa / m; q0 / (kPa) is the load at the initial support arch; s0 / (m) is the vertical displacement of the arch; x′ / (m) is the distance from the pipe-roof node to the tunnel face; μ is the Poisson's ratio; k1 / (MPa / m) is the stability value of the surrounding rock base coefficient.

[0140] According to the overlap length L of the pipe roof plap The relationship between the size of the disturbance range in front of the tunnel face divides the pipe roof vertical pressure reduction coefficient α1 into two sections, namely:

[0141]

[0142] Among them, R q is the total foundation reaction of the pipe shed.

[0143] According to formula (30), the pressure reduction coefficient α1 in formula (1) can be determined.

[0144] The overlap length L of the pipe rack in the above formula is plap It is the joint length between the current pipe shed and the next pipe shed.

[0145] 4) Pre-grouting cohesion increase coefficient

[0146] Pre-grouting reinforcement mainly improves the surrounding rock strength by increasing the cohesion of the surrounding rock in front of the tunnel face, but the effect of increasing the internal friction angle is relatively limited, so only the effect of grouting on cohesion is considered. The cohesion increase coefficient α2 after pre-grouting reinforcement is calculated as follows:

[0147]

[0148] Among them, c g / (kPa) is the slurry cohesion, L g / (m) is the grouting range; ξ is the grouting filling rate, and the specific values ​​are shown in Table 1.

[0149] Table 1 Grouting filling ratio of soil and rock formations

[0150]

[0151] Step 103, determining the stability coefficient of the core soil of the tunnel face by solving the tunnel face stability analysis model;

[0152] Substituting the key parameters solved in step 102 into equation (1) again, the stability coefficient K of the core soil of the tunnel face can be obtained.

[0153] Step 104 : The stability coefficient of the core soil of the tunnel face is used to determine the stability of the core soil of the tunnel face, and whether to adopt advanced support is determined based on the stability.

[0154] The stability coefficient K is compared with the stability threshold. If the stability coefficient K is greater than the stability threshold, it indicates that the core soil of the current tunnel face is stable. Otherwise, it indicates that the core soil of the current tunnel face is unstable and advanced support is required on the tunnel face.

[0155] In the embodiments of the present application, by introducing the spatial effect into the traditional stability analysis model, the prediction accuracy of the stability coefficient K is significantly improved, thereby improving the accuracy of the advanced support design measures to a certain extent.

[0156] A construction method for tunnel face advance support construction is carried out based on a tunnel face advance core soil stability analysis method. The construction method includes:

[0157] Step 101: Calculate the support force of the tunnel face anchor bolts and determine the optimal anchor bolt reinforcement length and arrangement density;

[0158] For the tunnel face anchor support, the tunnel face support force is calculated according to formula (24), and the optimal anchor reinforcement length and arrangement density are determined.

[0159] Determine the anchor reinforcement length L b , the value should ensure that the anchor rod still has sufficient anchoring length outside the plastic failure surface to give full play to the anchoring force. Usually L b Take it as the minimum length required below the calculated failure surface to the stable rock mass (even if the plastic zone corresponding to P1 is completely wrapped in the anchor zone). In other words, after calculating the plastic zone range from the equivalent stress release rate or the plastic zone depth, and adding a certain safety anchorage margin, the optimal L is obtained. b .

[0160] To determine the density of anchor bolts, first let the design bearing capacity of a single anchor bolt be P bolt , then the required number of rows or anchor rods per square meter should meet the following requirements:

[0161]

[0162] Where A is the load-bearing area of ​​the tunnel face, and ρ can be rounded up and appropriately adjusted with reference to the minimum spacing requirements in the construction specifications to take into account both construction feasibility and support effect.

[0163] Step 102: For the advanced pipe-roof support, determine the critical reinforcement length of the pipe-roof, and determine the vertical pressure reduction coefficient of the pipe-roof based on the critical reinforcement length of the pipe-roof;

[0164] Based on equations (25) and (27), the foundation reaction force distribution and the corresponding equivalent bed coefficient of the pipe-roof at different burial depths are obtained. The stability value k1 of the surrounding rock bed coefficient is then obtained using equation (29). Finally, at the node where the foundation reaction force or bed coefficient transitions from the initial value to the stable value k1, the corresponding pipe-roof burial length, i.e., the critical reinforcement length, is determined. After obtaining the critical reinforcement length, the vertical pressure reduction coefficient α1 of the pipe-roof can be calculated based on equation (30).

[0165] Step 103: For pre-grouting reinforcement, the cohesion increase coefficient is calculated by formula (31) based on the grouting filling rate and the slurry cohesion, thereby correcting the stability calculation;

[0166] Step 104: Calculate the stability coefficient K using the key parameters calculated in steps 101-103 according to formula (1);

[0167] Step 105: Compare the stability coefficient K calculated in step 104 with the stability threshold. When the stability coefficient K is greater than the stability threshold, perform advance support on the tunnel face.

[0168] In this embodiment, the stability threshold can be obtained by calculating the stability coefficient of the tunnel face in the past stable state. The average value of the historical stability coefficients or a value greater than the average value can be used as the threshold; it can also be calculated according to safety design requirements.

[0169] In actual engineering construction, the core soil stability coefficient K is first calculated through the core soil stability coefficient calculation model of the tunnel face, and then a preliminary assessment of the tunnel face stability is carried out. If the assessment results indicate the existence of instability risk, advanced support measures are adopted to achieve the goal of safe and stable tunnel face during tunnel construction.

[0170] An embodiment of the present application provides a device for analyzing the stability of advanced core soil of a tunnel face, the device comprising:

[0171] The model building module is used to set assumptions and establish a tunnel face stability analysis model based on the prism-wedge model.

[0172] A calculation module is used to determine the stability coefficient of the core soil of the tunnel face by solving the tunnel face stability analysis model;

[0173] The analysis module is used to determine the stability of the core soil of the tunnel face using the stability coefficient of the core soil of the tunnel face and to determine the advance support measures based on the stability.

[0174] The device in the embodiment of the present application can be an electronic device or a component in an electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal or other device other than a terminal. For example, the electronic device can be a GPU BOX, a mobile phone, a tablet computer, a laptop computer, a PDA, an in-vehicle electronic device, a mobile Internet device (Mobile Internet Device, MID), an augmented reality (AR) / virtual reality (VR) device, a robot, a wearable device, an ultra-mobile personal computer (Ultra-mobile personal computer, UMPC), a netbook or a personal digital assistant (Personal Digital Assistant, PDA), etc. It can also be a server, a network attached storage (NAS), a personal computer (PC), a television (TV), an ATM or a self-service machine, etc., and the embodiment of the present application does not specifically limit it.

[0175] The device in the embodiment of the present application may be a device having an operating system. The operating system may be an Android operating system, a Linux operating system, a Windows operating system, or other possible operating systems, which are not specifically limited in the embodiment of the present application.

[0176] The tunnel face advanced core soil stability analysis device provided in the embodiment of the present application can achieve Figure 1 To avoid repetition, the various processes implemented in the method embodiment are not described here.

[0177] An embodiment of the present application also provides a computer-readable storage medium having a computer program / instruction stored thereon. When the computer program / instruction is executed by a processor, the steps of the method for analyzing the stability of the advanced core soil of the tunnel face considering spatial effects as disclosed in the embodiment of the present application are implemented.

[0178] An embodiment of the present application further provides a computer program product, which, when executed on an electronic device, enables a processor to implement the steps of the method for analyzing the stability of advanced core soil of a tunnel face considering spatial effects as disclosed in the embodiment of the present application.

[0179] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0180] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, apparatuses, electronic devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0181] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0182] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable terminal device to implement the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0183] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0184] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements that are inherent to such process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0185] The above is a detailed introduction to the method and device for analyzing the stability of the advanced core soil of the tunnel face taking into account the spatial effect provided by this application. This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method of this application and its core idea; at the same time, for general technical personnel in this field, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on this application.

Claims

1. A method for analyzing the stability of advanced core soil at a tunnel face, characterized in that: The method comprises: Establish a tunnel face stability analysis model based on the prism-wedge model; Determine the values ​​of key parameters of the tunnel face stability analysis model; Solve the tunnel face stability analysis model based on the values ​​of key parameters and determine the tunnel face core soil stability coefficient; For the tunnel face where the core soil stability coefficient is less than the stability threshold, advance support measures are implemented.

2. The method according to claim 1, characterized in that The establishment of a tunnel face stability analysis model based on a prism-wedge model includes: Considering the spatial effect during face excavation, the assumptions for the tunnel face stability analysis model are set; Based on the classic prism-wedge model, a tunnel face stability analysis model is established which considers the combined effects of tunnel face spatial effect and advance support.

3. The method according to claim 1, characterized in that The tunnel face stability analysis model is: F q =α(x)qB(D cotθ0+L e ) Where K is the stability coefficient of the core soil of the tunnel face; θ0 is the angle between the failure surface of the tunnel face and the horizontal; is the internal friction angle of the surrounding rock; P1 is the support force provided by the anchor; α(x) is the vertical deformation pressure reduction coefficient considering the spatial effect; α1 is the vertical deformation pressure reduction coefficient of the disturbed section in front of the tunnel face under pipe-roof support; α2 is the cohesion increase coefficient of the surrounding rock under pre-grouting reinforcement; F c F is the resultant force of the sliding surface cohesion of the tunnel face; w F is the deadweight of the sliding body on the tunnel face; q is the resultant vertical deformation pressure above the sliding body on the tunnel face; q is the vertical deformation pressure; α=1.38; H is the tunnel depth; B is the tunnel face span; D is the tunnel face height; L e is the length of the unsupported section of the tunnel; β1, β2, β3 are Correlation coefficient; c / (kPa) is the initial cohesion of surrounding rock; γ / (kN / m 3 ) is the surrounding rock weight.

4. The method according to claim 1, wherein The determination of the values ​​of key parameters of the tunnel face stability analysis model includes: Determine the equivalent stress release rate in the trapezoidal load distribution of the sliding body on the tunnel face; Based on the equivalent stress release rate, vertical deformation pressure, tunnel face span, and tunnel face height, the resultant vertical deformation pressure above the tunnel face sliding body is determined; Based on the bolt support resultant force of each row on the tunnel face, the bolt support resultant force of all rows on the tunnel face is determined by summing them up; According to the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face, the vertical pressure reduction coefficient of the pipe roof is determined; The cohesion increase coefficient is determined based on the cohesion of the pre-grouting slurry and the grouting filling rate.

5. The method according to claim 4, characterized in that Based on the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face, the vertical pressure reduction coefficient of the pipe roof is determined, including: The pipe roof is discretized into n micro-ends, and the differential equation of the two-parameter elastic foundation beam is established; Convert the differential equation of the two-parameter elastic foundation beam into a finite difference equation; Based on the boundary conditions at both ends of the pipe roof, the pipe roof foundation reaction force at each node is determined according to the finite difference equation; According to the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face, the vertical pressure reduction coefficient of the pipe roof is divided into two sections, and the vertical pressure reduction coefficient of the pipe roof is determined.

6. A tunnel face advanced core soil stability analysis device, characterized in that: The device comprises: The model building module is used to set assumptions and establish a tunnel face stability analysis model based on the prism-wedge model; A parameter determination module is used to determine the values ​​of key parameters of the tunnel face stability analysis model; A calculation module is used to solve the tunnel face stability analysis model based on the values ​​of key parameters and determine the stability coefficient of the core soil of the tunnel face; The analysis module implements advanced support measures for the tunnel face where the core soil stability coefficient is less than the stability threshold.

7. The device according to claim 6, characterized in that The parameter determination module includes: The first parameter determination unit is used to determine the equivalent stress release rate in the trapezoidal load distribution of the sliding body on the tunnel face; The second parameter determination unit is used to determine the vertical deformation pressure resultant above the tunnel face sliding body based on the equivalent stress release rate, the vertical deformation pressure, the tunnel face span, and the tunnel face height; A third parameter determination unit is configured to determine the resultant force of all rows of anchor support on the tunnel face by summing the resultant force of anchor support on each row of the tunnel face; The fourth parameter determination unit determines the pipe roof vertical pressure reduction coefficient based on the relationship between the overlap length of the pipe roof and the disturbance range in front of the tunnel face; The fifth parameter determination unit determines a cohesion increase coefficient based on the cohesion of the pre-grouting slurry and the grouting filling rate.

Images