Method and system for determining distance between pressure relief drill holes in three-dimensional stress field

Abstract

The invention discloses a method and system for determining the pressure relief drill hole spacing in a three-dimensional stress field, and relates to the field of drill hole spacing layer.The method comprises the steps that the roadway bearing pressure peak value range is obtained; acquiring corresponding crustal stress magnitude, crustal stress azimuth angle and inclination angle; the cohesion C, the internal friction angle phi, the Poisson's ratio v and the pressure relief drill hole radius of the roadway surrounding rock are determined; the stress is converted into a stress load under a drilling coordinate system through a coordinate conversion method; on the basis of a Kirsch solving method and by means of the determined drilling radius and the obtained stress load under the drilling coordinate system, the normal stress sigma r, sigma t and sigma v and the shear stress taurt, taurv and tautv of any point within the preset range of the hole under the drilling coordinate system are obtained; based on the M-C strength criterion of the three-dimensional state, the radius r of the pressure relief drilling anti-reflection ring is obtained through solving by means of rock mechanical parameters; and according to the r, the arrangement mode of the pressure relief drill holes is determined. Aiming at unreasonable pressure relief drill hole arrangement and unclear pressure relief parameters in the prior art, the method improves the normativity of roadway surrounding rock drill hole pressure relief.

Description

Technical Field

[0001] The present application relates to the field of borehole spacing arrangement, and in particular to a method and system for determining pressure relief borehole spacing in a three-dimensional stress field. Background Art

[0002] Coal is a key industrial raw material in my country. Its huge demand has led to the extension of mine mining to deeper areas year by year. Under deep mining conditions, the stability control of surrounding rocks of chambers, tunnels and boreholes is the focus and difficulty of research. The excavation of tunnels will break the original stress balance state, causing stress redistribution and stress concentration. Under the influence of high stress environment and superimposed mining, the surrounding rock of the tunnel will produce large expansion deformation. Single anchor cable support has poor control effect on the stability of the surrounding rock of the tunnel. To this end, the use of drilling unloading to transfer the concentrated high stress around the tunnel to the deep stable rock mass, reducing the deformation and damage of the surrounding rock of the tunnel, is an effective auxiliary support method.

[0003] However, when designing the borehole pressure relief scheme, most of them use the empirical analogy method or numerical simulation method to determine the pressure relief borehole layout parameters, which lacks theoretical basis and quantitative analysis methods. Although a few studies have carried out theoretical calculations, most of them simplify the calculation model into a plane strain problem, ignoring the real three-dimensional stress environment of the underground rock mass, and failing to accurately reflect the interaction mechanism between the pressure relief borehole and the complex ground stress field, resulting in a deviation between the obtained borehole layout parameters and the actual engineering conditions. Due to the unreasonable determination of the borehole spacing, problems such as insufficient pressure relief in some areas, unsatisfactory pressure relief effect, and difficulty in transferring high stress to the deep often occur, which ultimately leads to poor control of the stability of the tunnel surrounding rock. In severe cases, it may even cause dynamic disasters such as roof collapse, large-scale anchor / cable failure, etc., which bring hidden dangers to coal mine safety production. Summary of the invention

[0004] In response to the problem of unreasonable arrangement of pressure relief boreholes in the prior art leading to stress concentration in the surrounding rock of the tunnel, the present application provides a method and system for determining the spacing between pressure relief boreholes in a three-dimensional stress field. By obtaining the magnitude and direction of the ground stress corresponding to the peak value of the support pressure, a ground stress coordinate system, a geodetic rectangular coordinate system and a borehole coordinate system are established and coordinate conversion is performed. Based on the Kirsch solution method and the Mohr-Coulomb yield criterion, an implicit equation for the boundary of the plastic zone around the borehole is established, and a reasonable radius of the pressure relief borehole anti-transmission circle and borehole spacing are solved to improve the stability of the surrounding rock of the tunnel.

[0005] The purpose of this application is achieved through the following technical solutions.

[0006] One aspect of the present application provides a method for determining the spacing of pressure relief boreholes in a three-dimensional stress field, including: S1, obtaining the peak range of tunnel support pressure through a borehole stress meter; S2, obtaining the ground stress magnitude, ground stress azimuth and inclination corresponding to the peak range of support pressure through ground stress measurement; S3, determining the parameters of the tunnel surrounding rock through rock mechanics tests, the parameters including cohesion C, internal friction angle φ and Poisson's ratio v; S4, determining the radius of the pressure relief borehole according to the engineering geological parameters and construction conditions of the construction mine; S5, establishing a ground stress coordinate system, a geodetic rectangular coordinate system and a borehole coordinate system, and converting the ground stress magnitude, azimuth and inclination obtained in S2 in the ground stress coordinate system into stress loads in the borehole coordinate system through a coordinate conversion method. ; S6, in the borehole coordinate system, based on the Kirsch solution method and using the borehole radius determined by S4 and the stress load in the borehole coordinate system obtained by S5, the normal stresses σr, σt, σv and shear stresses τrt, τrv, τtv at any point within the preset range of the hole in the borehole coordinate system are obtained; S7, based on the MC strength criterion of the three-dimensional state, using the rock mechanics parameters obtained in S3, an implicit equation of the boundary of the plastic zone around the borehole is established, and the stress component at any point within the preset range of the hole in the borehole coordinate system obtained by S6 is substituted into the implicit equation to solve the radius r of the pressure relief borehole anti-transmission circle; S8, according to the radius r of the pressure relief borehole anti-transmission circle, determine the row spacing PR of two adjacent pressure relief boreholes and the arrangement of the pressure relief boreholes.

[0007] Specifically, the peak value of the abutment pressure is the maximum abutment pressure value formed at the leading position of the tunnel due to stress redistribution after the tunnel surrounding rock is excavated. The peak value of the abutment pressure reflects the stress state of the rock around the tunnel and is an important basis for determining the measurement position of the ground stress. Borehole stress meter: an instrument used to measure the stress state of the rock mass in the borehole. By installing strain gauges or other sensors in the borehole, the strain data on the borehole wall can be obtained, and then the stress magnitude and direction of the rock mass can be calculated. Azimuth and inclination of ground stress: two angle parameters reflecting the spatial direction of ground stress. The azimuth represents the angle between the ground stress and the due north direction in the horizontal plane, and the value range is 0° to 360°; the inclination represents the angle between the ground stress and the horizontal plane, and the value range is 0° to 90°. Ground stress coordinate system: an orthogonal coordinate system established with the main direction of ground stress as the coordinate axis. The maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 are usually used as coordinate axes to represent the spatial distribution state of ground stress. Borehole coordinate system: an orthogonal coordinate system established with the borehole axis as the coordinate axis. Usually, the borehole axis direction is taken as the z-axis, the borehole radius direction is taken as the x-axis, and the direction perpendicular to the x-axis and z-axis is taken as the y-axis. The borehole coordinate system is used to analyze the stress distribution around the borehole. Kirsch solution: an analytical method for solving the stress distribution around a circular hole. Based on the Kirsch solution under the full plane strain state, the normal stress and shear stress state at any point around the hole can be obtained. Mohr-Coulomb strength criterion (MC strength criterion): an empirical criterion for describing the shear strength characteristics of geotechnical materials. Pressure relief borehole anti-reflection zone: a stress reduction area formed in the rock mass around the borehole due to the pressure relief effect of the borehole, with the pressure relief borehole as the center. The radius of the pressure relief borehole anti-reflection zone reflects the pressure relief range of a single borehole and is a key parameter for determining the borehole spacing.

[0008] More specifically, when determining the radius of the pressure relief drilling hole, it is necessary to comprehensively consider factors such as the engineering geological parameters and construction conditions of the construction mine. According to the geological data of the mine, obtain geological parameters such as the lithology, stratigraphic structure, and rock integrity of the rocks around the tunnel. Lithology: Determine the main rock types of the tunnel surrounding rock, such as sandstone, mudstone, limestone, etc. The mechanical properties and pressure relief effects of different lithologies are different. Stratigraphic structure: Analyze the inclination, thickness, and bedding characteristics of the stratum in which the tunnel is located, and evaluate the influence of the stratigraphic structure on the drilling construction and pressure relief effect. Rock integrity: Evaluate the degree of development of joints and fissures in the tunnel surrounding rock. The higher the rock integrity, the greater the difficulty of drilling construction, but the better the pressure relief effect. Combined with the construction conditions of the mine, determine the process parameters of drilling construction. Drilling diameter: According to the specifications and construction capacity of the existing drilling rig equipment, select a suitable drill bit diameter, usually 50 to 100 mm. Drilling depth: According to the stress distribution characteristics of the tunnel surrounding rock and the pressure relief requirements, determine the drilling depth, generally 2 to 5 m. Drilling angle: The drilling angle is determined according to the pressure relief design requirements and site conditions, and is usually perpendicular to the tunnel wall or inclined at a small angle. In this application, the drilling radius ranges from 0.1m to 0.5m.

[0009] Further, S2, obtaining the magnitude of the in-situ stress, the in-situ stress azimuth and the inclination angle corresponding to the peak range of the supporting pressure through in-situ stress measurement, including: within the peak range of the supporting pressure determined in step S1, obtaining the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 within the corresponding range through in-situ stress measurement; obtaining the stress inclination angles α1, α2 and α3, and the stress azimuth angles β1, β2 and β3 corresponding to the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 through in-situ stress measurement.

[0010] Further, S5, establishes a geostress coordinate system, a geodetic rectangular coordinate system and a borehole coordinate system, and converts the geostress magnitude, azimuth and inclination angle in the geostress coordinate system obtained in S2 into stress loads in the borehole coordinate system through a coordinate conversion method, including: using the directions of the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 obtained in step S2 as coordinate axes, and establishing an orthogonal coordinate system O-XYZ. The X-axis coincides with the direction of the maximum principal stress σ1, the Y-axis coincides with the direction of the intermediate principal stress σ2, and the Z-axis coincides with the direction of the minimum principal stress σ3. With the drilling construction position as the origin, establish the geodetic rectangular coordinate system O-X'Y'Z'. The X' axis points to the east, the Y' axis points to the north, and the Z' axis points vertically upward. The borehole coordinate system OX”Y”Z” is established according to the borehole inclination angle δ and the borehole azimuth angle w of the borehole spatial arrangement position relative to the geodetic coordinate system. The borehole inclination angle δ refers to the angle between the borehole axis and the vertical direction (Z' axis), and the value range is 0°~90°. The borehole azimuth angle w refers to the angle between the projection of the borehole axis on the horizontal plane (X'O'Y' plane) and the true north direction (Y' axis), and the value range is 0°~360°. The Z” axis coincides with the borehole axis, and the X” axis and the Y” axis are orthogonal to the Z” axis on the borehole section. According to the coordinate conversion formula, the stress state under the geostress coordinate system O-XYZ is converted into the stress load under the borehole coordinate system OX”Y”Z”. The stress state under the geostress coordinate system is represented by the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3, as well as the corresponding stress inclination angles α1, α2 and α3, and the stress azimuth angles β1, β2 and β3. The stress tensor in the geostress coordinate system is converted into the stress tensor in the earth rectangular coordinate system through the rotation transformation matrix. The stress tensor in the earth rectangular coordinate system is then converted into the stress tensor in the borehole coordinate system through the rotation transformation matrix. The stress components σ'x, σ'y, σ'z, τ'xy, τ'yz and τ'zx in the borehole coordinate system OX”Y”Z” are obtained, which are the stress loads in the borehole coordinate system.

[0011] Further, the coordinate transformation formula is:

[0012]

[0013] Wherein: l1, m1 and n1 represent the cosine value of the angle between X′ and the borehole coordinate system X″, Y″ and Z″; l2, m2 and n2 represent the cosine value of the angle between Y′ and the borehole coordinate system X″, Y″ and Z″; l3, m3 and n3 represent the cosine value of the angle between Z′ and the borehole coordinate system X″, Y″ and Z″. d1, e1 and f1 represent the cosine value of the angle between X and the geodetic coordinate system X′, Y′ and Z′; d2, e2 and f2 represent the cosine value of the angle between Y and the geodetic coordinate system X′, Y′ and Z′; d3, e3 and f3 represent the cosine value of the angle between Z and the geodetic coordinate system X′, Y′ and Z′.

[0014] di=cosαi sinβi(i=1,2,3), ei=cosαi·cosβi(i=1,2,3), fi=sinαi(i=1,2,3), l1=cosδ·cosw, m1=c osδ·sinw, n1=-sinδ, l2=-sinw, m2=cosw, n2=0, l3=sinδ·cosw, m3=sinδ·sinw, n3=cosδ.

[0015] Further, S6, in the drilling coordinate system, based on the Kirsch solution method and using the drilling radius determined in S4 and the stress load in the drilling coordinate system obtained in S5, the normal stress σr, σt, σv and shear stress τrt, τrv, τtv of any point within the preset range of the hole in the drilling coordinate system are obtained, including: according to the stress load σ'x, σ'y, σ'z, τ'xy, τ'yz and τ'zx in the drilling coordinate system OX"Y"Z" obtained in step S5, the normal stress σr, σt, σv and shear stress τrt, τrv, τtv of any point around the drilling in the polar coordinate system in the three-dimensional space obtained by the Kirsch solution method:

[0016]

[0017] Among them, θ and r are the polar coordinates of any point, ν is the Poisson's ratio, and a is the equivalent radius of the drill hole.

[0018] Further, S7, based on the MC strength criterion of the three-dimensional state, using the rock mechanics parameters obtained in S3, establishes an implicit equation for the boundary of the plastic zone around the borehole, and brings the stress component of any point within the preset range of the hole in the borehole coordinate system obtained in S6 into the implicit equation to solve the radius r of the pressure relief borehole anti-reflection ring, including: using the stress invariant I′1 and the Lode angle θσ, the Mohr-Coulomb yield surface is expressed as:

[0019]

[0020] Among them, I′1 represents the principal stress invariant, reflecting the average level of the stress state; θσ represents the Lode angle, which represents the angle of the stress state on the π plane and reflects the relative magnitude relationship of the stress state; represents the friction angle in the rock mass; C represents the cohesion in the rock mass; J2 represents the second invariant deviator stress;

[0021]

[0022] Wherein, J3 represents the third invariant deviatoric stress; σ(1) represents the maximum principal stress of the unit cell; σ(2) represents the intermediate principal stress of the unit cell; σ(3) represents the minimum principal stress of the unit cell; according to the normal stresses σr, σt, σv and shear stresses τrt, τrv, τtv at any point (r, θ) within the preset range of the hole in the drilling coordinate system obtained in step S6, an implicit expression for the approximate solution of the failure size of the drilling hole at any rotation angle in space in the three-dimensional stress field is established: Among them, α1, α2, α3, β1, β2 and β3 represent the azimuth and inclination angles corresponding to the principal stress; δ and ω represent the inclination and azimuth angles of the roadway relative to the geodetic coordinate system; a represents the equivalent radius of the borehole; C represents the cohesion of the rock mass; represents the internal friction angle of the rock mass; v represents the Poisson's ratio of the rock mass; by using numerical solution methods such as Newton iteration method and arc length method, the implicit expression is solved to obtain the coordinates (r, θ) of the boundary point of the plastic zone around the borehole that meets the yield condition, where r is the radius of the pressure relief borehole anti-permeability circle.

[0023] Among them, rock mass strength criteria are not limited to the MC strength criterion, but also include classic strength criteria such as the Matsuoka-Nakai criterion, the Mogi-Coulomb criterion, the Drucker-Prager criterion, and the Lade-Duncan criterion.

[0024] Further:

[0025]

[0026] Where:

[0027]

[0028] Among them, p is the average stress, which reflects the influence of hydrostatic pressure on material yield; q is the generalized shear stress, which reflects the influence of shear stress on material yield.

[0029] Further:

[0030] I1=σ r +σ θ +σ v

[0031]

[0032] Among them: σr, σθ, σv represent normal stress; τrθ, τrv, τθv represent shear stress;

[0033] Further, S8, according to the radius r of the pressure relief borehole anti-reflection circle, determine the row spacing PR of two adjacent pressure relief boreholes and the arrangement of the pressure relief boreholes, including: adopting a single row parallel arrangement, that is, arranging a row of pressure relief boreholes on both sides of the tunnel. This arrangement is simple and easy to implement, and can form a relatively uniform pressure relief effect on both sides of the tunnel, which is conducive to maintaining the stability of the rock mass around the tunnel. Arrangement position of the first borehole: The first borehole is arranged at a distance of r from the working face, that is, the boreholes are arranged at a position of a radius r of an anti-reflection circle in front of the working face. In this way, it can be ensured that during the advancement of the working face, there is always a complete pressure relief anti-reflection circle in front of the working face, which releases the stress in the rock mass near the working face in advance and reduces the stress concentration of the working face. Arrangement of subsequent boreholes: Arrange the second to nth boreholes in parallel along the advancement direction of the working face. Parallel arrangement can ensure that the pressure relief effect of each borehole is relatively independent, and the mutual interference between adjacent boreholes is small, which is conducive to forming a continuous and uniform pressure relief area. The row spacing PR of two adjacent pressure relief boreholes: According to the radius r of the anti-reflection circle of the pressure relief borehole, the row spacing PR of two adjacent pressure relief boreholes is determined to be 2r. The selection of this row spacing is based on the following considerations: When the row spacing PR = 2r, the anti-reflection circles of the two adjacent boreholes are just tangent, which can form a continuous pressure relief area and avoid the existence of a pressure relief blind area. If the row spacing PR>2r, there will be a pressure relief blind area between adjacent boreholes, and the rock mass stress cannot be effectively released, which may lead to local stress concentration and surrounding rock damage. If the row spacing PR<2r, the anti-reflection circles of adjacent boreholes will overlap. Although the pressure relief effect is more significant, the number of boreholes and construction costs will increase, and excessive pressure relief may cause excessive damage and deformation of the surrounding rock. Therefore, the row spacing PR = 2r is the optimal choice to balance the pressure relief effect and construction cost, which can not only form a continuous and effective pressure relief area, but also control the number of boreholes and engineering investment.

[0034] Preferably, the surrounding rock stress reduction rate is selected as the evaluation index of the pressure relief and permeability enhancement effect, and the objective function is established. The surrounding rock stress reduction rate reflects the effectiveness of the pressure relief drilling arrangement scheme in reducing the concentration of surrounding rock stress. The optimal drilling arrangement scheme X_opt and the optimal drilling spacing PR_opt are solved by the particle swarm algorithm. Specifically, the objective function is established, and the expression is: f(X) = E(X), where X represents the drilling arrangement scheme, and E(X) represents the surrounding rock stress reduction rate. Surrounding rock stress reduction rate E(X): According to the geological conditions and initial stress state of the rock mass around the tunnel, a surrounding rock stress distribution model before the pressure relief drilling is constructed is established to obtain the initial maximum principal stress σ_max_0; for a given drilling arrangement scheme X, a surrounding rock stress distribution model after the pressure relief drilling is constructed is established to obtain the maximum principal stress σ_max_X after pressure relief; the surrounding rock stress reduction rate E(X) is calculated: E(X) = (σ_max_0-σ_max_X) / σ_max_0×100%. The adjacent drilling row spacing range, drilling arrangement range and drilling number upper limit are converted into mathematical constraints: adjacent drilling row spacing constraint: PRmin≤PR≤PRmax; drilling arrangement range constraint: drilling arrangement is within a certain range from the working surface, such as [d_min, d_max]; drilling number constraint: drilling number n≤Nmax. Construct a complete optimization model: objective function: max f(X)=E(X); decision variables: X={(x1,y1),(x2,y2),...,(xn,yn),PR}; constraints: PRmin≤PR≤PRmax; d_min≤xi≤d_max, i=1,2,...,n; n≤Nmax, where (xi,yi) represents the position coordinates of the i-th drilling hole and PR represents the row spacing of adjacent drilling holes.

[0035] The particle swarm algorithm is used to solve the optimization model: initialize the particle swarm, each particle represents a drilling arrangement plan, including the drilling position coordinates and row spacing; for each particle, calculate the surrounding rock stress reduction rate E(X) as the particle's fitness value; update the individual optimal position and global optimal position of the particle; according to the individual optimal position and global optimal position of the particle, update the particle's speed and position;

[0036] Another aspect of the present application also provides a system for determining the spacing between pressure relief boreholes in a three-dimensional stress field, which is used to execute a method for determining the spacing between pressure relief boreholes in a three-dimensional stress field of the present application.

[0037] Compared with the prior art, the advantages of this application are:

[0038] The ground stress component corresponding to the peak value of the tunnel support pressure is obtained by combining the borehole stress meter and the ground stress measurement, taking into account the actual stress state of the tunnel, and providing reliable stress boundary conditions for the determination of subsequent drilling layout parameters.

[0039] The geostress coordinate system, geodetic rectangular coordinate system and borehole coordinate system are introduced. The geostress components are converted into stress loads around the borehole through coordinate transformation, which realizes the coupled analysis of the spatial distribution characteristics of geostress and the borehole layout parameters and improves the accuracy of determining the borehole layout parameters.

[0040] Based on the Kirsch solution method, an analytical expression of the stress component around the borehole was established. Combined with the Mohr-Coulomb yield criterion, an implicit equation for the boundary of the plastic zone around the borehole was established. By solving the equation, the radius of the pressure-relief borehole anti-reflection circle was obtained, and the quantitative analysis and evaluation of the pressure-relief and anti-reflection effect of the borehole was realized.

[0041] On the basis of determining the radius of the pressure relief drilling hole anti-reflection circle, the optimal matching between the drilling arrangement and the pressure relief anti-reflection effect is achieved by reasonably setting the row spacing between adjacent drilling holes, avoiding problems such as incomplete pressure relief due to over-drilling or over-sparse drilling, and achieving the optimization of the pressure relief anti-reflection effect.

[0042] A row of pressure relief drill holes are arranged on both sides of the tunnel in a single-row parallel arrangement. The first drill hole is arranged at the radius of the pressure relief drill hole permeability enhancement circle from the working face, and subsequent drill holes are arranged parallel to the advancement direction of the working face. The arrangement is simple and feasible, which facilitates the implementation of the project.

[0043] By optimizing the layout parameters of the pressure relief drilling holes, the stress state of the tunnel surrounding rock is effectively improved, the stress concentration of the surrounding rock is reduced, and the stability of the tunnel surrounding rock is improved, providing a reliable measure for effectively preventing and controlling dynamic disasters such as roof falls, rock caving, and anchor failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present application will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0045] Figure 1 It is a schematic diagram of the tunnel drilling pressure relief scheme in the three-dimensional stress field provided by the present application;

[0046] Figure 2 It is a top view schematic diagram of the tunnel drilling pressure relief scheme in the three-dimensional stress field provided by the present application;

[0047] Figure 3 The invention is an exemplary flow chart of a method for determining the spacing between pressure relief boreholes in a three-dimensional stress field.

[0048] Description of the numbers in the figure:

[0049] 1. The mining working face in this section; 2. The goaf in the upper section; 3. The return air tunnel in this section. DETAILED DESCRIPTION

[0050] The method and system provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0051] The construction mine of this application is as follows Figure 1 As shown in the figure, it includes the mining face 1 of this section and the goaf 2 of the upper section. The working face is advanced in the direction indicated by the arrow in the figure. The return air roadway 3 of this section shown in the figure is subjected to drilling pressure relief treatment. Figure 3 The invention is an exemplary flow chart of a method for determining the spacing of pressure relief boreholes in a three-dimensional stress field, and the method comprises: obtaining the peak range of tunnel support pressure by means of a borehole stress meter; obtaining the ground stress magnitude, ground stress azimuth and inclination corresponding to the peak range of support pressure by means of ground stress measurement; determining the parameters of the tunnel surrounding rock by means of rock mechanics tests, the parameters including cohesion C, internal friction angle φ and Poisson's ratio v; determining the radius of the pressure relief borehole according to the engineering geological parameters and construction conditions of the construction mine; establishing a ground stress coordinate system, a geodetic rectangular coordinate system and a borehole coordinate system, and converting the ground stress magnitude, azimuth and inclination in the ground stress coordinate system into the borehole coordinate system by means of a coordinate conversion method. stress load in the borehole coordinate system; in the borehole coordinate system, based on the Kirsch solution method and using the determined borehole radius and the obtained stress load in the borehole coordinate system, the normal stress σr, σt, σv and shear stress τrt, τrv, τtv at any point within the preset range of the hole in the borehole coordinate system are obtained; based on the MC strength criterion of the three-dimensional state and using the obtained rock mechanics parameters, the implicit equation of the boundary of the plastic zone around the borehole is established, and the stress component at any point within the preset range of the hole in the borehole coordinate system is substituted into the implicit equation to solve the radius r of the pressure relief borehole anti-reflection circle; according to the radius r of the pressure relief borehole anti-reflection circle, the row spacing PR of two adjacent pressure relief boreholes and the arrangement of the pressure relief boreholes are determined.

[0052] The location of the peak support pressure measured by the borehole stress meter is 5m away from the working face, and this data is used as the basis for determining the location of the pressure relief borehole layout area. Based on the ground stress measurement method, the ground stress magnitude, ground stress azimuth and inclination at the peak support pressure range are measured as shown in Table 1:

[0053] <![CDATA[σ1 / MPa]]> <![CDATA[σ2 / MPa]]> <![CDATA[σ3 / MPa]]> <![CDATA[α1 / °]]> <![CDATA[α2 / °]]> <![CDATA[α3 / °]]> <![CDATA[β1 / °]]> <![CDATA[β2 / °]]> <![CDATA[β3 / °]]> 10.82 5.75 4.79 39.37 50.59 -1.47 119.35 -63.65 208.14

[0054] Through rock mechanics tests, the internal cohesion of the coal seam in the borehole pressure relief tunnel was determined to be C = 0.8MPa, the internal friction angle φ = 25°, and the Poisson's ratio v = 0.25. Through field measurements, the tunnel cross-sectional dimensions were determined to be 5400×3600mm. According to the engineering geological parameters and construction conditions of the construction mine, the radius of the pressure relief drill hole was determined to be a = 0.2m.

[0055] The geostress coordinate system O-XYZ is established, and the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 are coincident with the coordinate axes X, Y and Z respectively. According to the geostress measurement results, σ1 = 10.82MPa, σ2 = 5.75MPa, and σ3 = 4.79MPa. The geodetic rectangular coordinate system O-X'Y'Z' is established, with the tunnel axis as the Z' axis, the horizontal right of the tunnel section as the X' axis, and the vertical upward of the tunnel section as the Y' axis. According to the geostress azimuth and inclination data, α1 = 39.37°, α2 = 50.59°, α3 = -1.47°, β1 = 119.35°, β2 = -63.65°, and β3 = 208.14°, the stress components in the geodetic stress coordinate system are converted to the geodetic rectangular coordinate system through the coordinate transformation matrix.

[0056] The drilling coordinate system OX”Y”Z” is established, with the drilling axis as the Z” axis, the drilling radial as the X” axis, and the drilling tangent as the Y” axis. According to the drilling spatial arrangement position relative to the earth coordinate system, the drilling inclination and drilling azimuth are both 90°. The stress components in the earth rectangular coordinate system are converted to the drilling coordinate system through the coordinate transformation matrix:

[0057]

[0058] The stress components under the drilling coordinate system OX”Y”Z” are taken as the stress load around the drilling hole and are denoted as σx, σy, σz, τxy, τyz, and τzx, which are used in the subsequent calculation of the drilling plastic zone radius and drilling spacing.

[0059] in:

[0060] <![CDATA[d1]]> <![CDATA[d2]]> <![CDATA[d3]]> <![CDATA[e1]]> <![CDATA[e2]]> <![CDATA[e3]]> <![CDATA[f1]]> <![CDATA[f2]]> <![CDATA[f3]]> 0.67 -0.57 -0.47 -0.38 0.28 -0.88 0.63 0.77 -0.03 <![CDATA[l1]]> <![CDATA[m1]]> <![CDATA[n1]]> <![CDATA[l2]]> <![CDATA[m2]]> <![CDATA[n2]]> <![CDATA[l3]]> <![CDATA[m3]]> <![CDATA[n3]]> 0 0 -1 -1 0 0 0 1 0

[0061] The normal stress σ at any point around the borehole in the polar coordinate system in three-dimensional space obtained based on the Kirsch solution method r , σ t , σ v and shear stress τ rt , τ rv , τ tv The calculation formula is:

[0062]

[0063] Where θ and r are the polar coordinates of any point, ν is the Poisson's ratio, and a is the equivalent radius of the borehole.

[0064] The normal stress σr, σt, σv and shear stress τrt, τrv, τtv at any point around the borehole can be expressed by the following cubic equation:

[0065] σ 3 -I1σ 2 +I2σ-I3=0

[0066] Where: I1, I2 and I3 are stress state invariants, and their expressions are:

[0067] I1=σ r +σ θ +σ v

[0068]

[0069] The calculation formula of the principal stress at any point around the borehole is:

[0070]

[0071] Where:

[0072]

[0073] Using stress invariants and Lode angles, the Mohr-Coulomb yield surface can be expressed as:

[0074]

[0075] The expressions of various physical quantities in the formula are as follows:

[0076]

[0077] I1′=(σ (1) +σ (2) +σ (3) )

[0078]

[0079] The implicit expression of the approximate solution of the failure size of the drill hole at any rotation angle in the three-dimensional stress field is as follows:

[0080] Substituting the borehole inclination angle δ = 90° and the azimuth angle ω = 90° into the implicit expression of the approximate solution of the borehole failure size, the solution is to obtain the radius of the pressure relief borehole anti-reflection circle r = 0.648m. According to the calculated radius r of the borehole plastic zone, the row spacing PR between two adjacent pressure relief boreholes is determined. Since the edges of the plastic zones of adjacent boreholes must be tangent to achieve the best pressure relief effect, the borehole row spacing PR should satisfy: PR = 2r = 2 × 0.648 = 1.296m. The borehole arrangement is determined to be a single row parallel arrangement, with a row of pressure relief boreholes arranged on each side of the tunnel. The first borehole is arranged at a distance of 0.648m (i.e., r) from the working face; along the advancing direction of the working face, the second, third, and nth boreholes are arranged in parallel with a spacing of 1.296m (i.e., R); the sequence of boreholes close to the coal wall is represented as d11, d12, and d1n; the sequence of boreholes close to the coal pillar is represented as d21, d22, and d2n. So far, based on the measured ground stress results and the calculated radius of the borehole pressure relief and permeability enhancement circle, the spacing of the pressure relief boreholes is determined to be 1.296m, and the arrangement is a single row parallel arrangement. The number of boreholes actually arranged is determined based on the cross-sectional dimensions of the roadway, providing guidance for the drilling construction.

Claims

1. A method and system for determining the spacing of pressure relief boreholes in a three-dimensional stress field, comprising: S1, obtain the peak range of tunnel support pressure through the borehole stress gauge; S2, obtain the ground stress magnitude, ground stress azimuth and inclination angle corresponding to the peak value of the support pressure through ground stress measurement; S3, determine the parameters of the tunnel surrounding rock through rock mechanics tests, including cohesion C, internal friction angle φ and Poisson's ratio v; S4, determine the radius of the pressure relief drilling hole according to the engineering geological parameters and construction conditions of the construction mine; S5, establishing a geostress coordinate system, a geodetic rectangular coordinate system and a borehole coordinate system, and converting the geostress magnitude, azimuth and inclination angle in the geostress coordinate system obtained in S2 into a stress load in the borehole coordinate system through a coordinate conversion method; S6, based on the Kirsch solution and using the drilling radius determined by S4 and the stress load in the drilling coordinate system obtained by S5, obtain the normal stress σ at any point within the preset range of the hole in the drilling coordinate system r , σ t , σ v and shear stress τ rt , τ rv , τ tv ; S7, based on the MC strength criterion of the three-dimensional state, using the rock mechanics parameters obtained in S3, establish the implicit equation of the boundary of the plastic zone around the borehole, and bring the stress component of any point within the preset range of the hole in the borehole coordinate system obtained in S6 into the implicit equation to solve and obtain the radius r of the pressure relief borehole anti-reflection circle; S8, determining the row spacing PR of two adjacent pressure relief boreholes and the arrangement of the pressure relief boreholes according to the radius r of the pressure relief borehole anti-reflection ring.

2. The method and system for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 1, characterized in that: S2, obtain the ground stress magnitude, ground stress azimuth and inclination corresponding to the peak range of the abutment pressure through ground stress measurement, including: In the support pressure peak range determined in step S1, the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 in the corresponding range are obtained by measuring the ground stress; The stress inclination angles α1, α2 and α3 corresponding to the maximum principal stress σ1, intermediate principal stress σ2 and minimum principal stress σ3, as well as the stress azimuth angles β1, β2 and β3 are obtained through ground stress measurement.

3. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 2, characterized in that: S5, establish the geostress coordinate system, the earth rectangular coordinate system and the borehole coordinate system, and transform the geostress magnitude, azimuth and inclination obtained in S2 in the geostress coordinate system into the stress load in the borehole coordinate system through the coordinate transformation method, including: Establishing a geostress coordinate system O-XYZ, wherein the three coordinate axes of the geostress coordinate system O-XYZ coincide with the directions of the maximum principal stress σ1, the intermediate principal stress σ2, and the minimum principal stress σ3 obtained in step S2 respectively; Establish a geodetic rectangular coordinate system O-X'Y'Z', and establish a drilling coordinate system OX"Y"Z" according to the drilling inclination angle δ and the drilling azimuth w of the drilling spatial arrangement position relative to the geodetic coordinate system; According to the coordinate conversion formula, the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 in the geostress coordinate system obtained in step S2 and the corresponding stress inclination angles α1, α2 and α3, as well as the stress azimuth angles β1, β2 and β3 are converted into the stress component σ in the borehole coordinate system OX”Y”Z”. x '、σ y '、σ z '、τ xy '、τ yz ' and τ zx ', and obtain the stress load in the drilling coordinate system.

4. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 3, characterized in that: Coordinate transformation formula: Wherein: l1, m1 and n1 represent the cosine value of the angle between X' and the borehole coordinate system X", Y" and Z"; l2, m2 and n2 represent the cosine value of the angle between Y' and the borehole coordinate system X", Y" and Z"; l3, m3 and n3 represent the cosine value of the angle between Z' and the borehole coordinate system X", Y" and Z"; d1, e1 and f1 represent the cosine value of the angle between X and the geodetic coordinate system X', Y' and Z'; d2, e2 and f2 represent the cosine value of the angle between Y and the geodetic coordinate system X', Y' and Z'; d3, e3 and f3 represent the cosine value of the angle between Z and the geodetic coordinate system X', Y' and Z'.

5. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 4, characterized in that: S6, obtain the normal stress σ at any point within the preset range of the hole in the drilling coordinate system r , σ t , σ v and shear stress τ rt , τ rv , τ tv ,include: The stress load σ under the drilling coordinate system OX"Y"Z" obtained in step S5 x '、σ y '、σ z '、τ xy '、τ yz ' and τ zx ', the normal stress σ at any point around the borehole in the polar coordinate system in three-dimensional space obtained by the Kirsch solution method r , σ t , σ v and shear stress τ rt , τ rv , τ tv : Among them, θ and r are the polar coordinates of any point, ν is the Poisson's ratio, and R is the equivalent radius of the drill hole.

6. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 5, characterized in that: S7, solving to obtain the radius r of the pressure relief drilling anti-reflection circle, including: Using stress invariant I1' and Lode angle θ σ , the Mohr-Coulomb yield surface is expressed as: Where I1' represents the principal stress invariant; θ σ represents the Lode angle; φ represents the friction angle in the rock mass; C represents the cohesion in the rock mass; J2 represents the second invariant deviator stress; I1′=(σ (1) +s (2) +s (3) ) Where J3 represents the third invariant deviatoric stress; σ (1) Represents the maximum principal stress of the unit cell; σ (2) represents the intermediate principal stress of the unit cell; σ (3) Represents the minimum principal stress of the unit cell; The normal stress σ at any point (r, θ) within the preset range of the hole in the drilling coordinate system obtained in step S6 r , σ t , σ v and shear stress τ rt , τ rv , τ tv , an implicit expression for the approximate solution of the failure size of the drill hole at any rotation angle in space in a three-dimensional stress field is established: Among them, α1, α2, α3, β1, β2 and β3 represent the azimuth and inclination angles corresponding to the principal stress; δ and ω represent the inclination and azimuth angles of the roadway relative to the geodetic coordinate system; R represents the equivalent radius of the borehole; C represents the cohesion of the rock mass; represents the friction angle of the rock mass; v represents the Poisson's ratio of the rock mass; By solving the implicit expression, the radius r of the pressure relief borehole anti-reflection circle is obtained.

7. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 6, characterized in that: Where: Where p represents the mean stress and q represents the generalized shear stress.

8. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 7, characterized in that: I1=σ r +s θ +s v Among them, σ r , σ t , σ v represents normal stress; shear stress τ rt , τ rv , τ tv Represents shear stress.

9. The method for determining the spacing between pressure relief boreholes in a three-dimensional stress field according to claim 8, characterized in that: S8, determining the row spacing PR of two adjacent pressure relief boreholes and the arrangement of the pressure relief boreholes according to the radius r of the pressure relief borehole anti-reflection ring, including: The drilling arrangement adopts a single-row parallel arrangement, with a row of pressure relief drilling holes arranged on both sides of the tunnel; The first drill hole is arranged at a distance r from the working surface, and the second to nth drill holes are arranged parallel to the advancing direction of the working surface; The row spacing between two adjacent pressure relief boreholes is PR=2r.

10. A system for determining the spacing of pressure relief boreholes in a three-dimensional stress field, characterized in that: Used to execute instructions to implement the method for determining the spacing between pressure relief drilling holes in a three-dimensional stress field as described in any one of claims 1 to 9.

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