A large deformation grading method combining while-drilling parameters and borehole testing

Abstract

The application provides a large deformation grading method combining with drilling parameters and drilling tests, and belongs to the field of tunnel engineering construction. Specifically, the method comprises the following steps: obtaining engineering rock mass quality indexes; obtaining soft rock mass strength through drilling; obtaining strain data by driving a stress-strain measuring rod into the drilling; calculating soft rock ground stress according to the material parameters of the stress-strain measuring rod and the measured strain data, and obtaining a soft rock strength stress ratio in front of a working face; obtaining the surrounding rock deformation amount through vertical deformation calculation of the stress-strain measuring rod, and solving a tunnel longitudinal deformation curve through a formula, so as to calculate the final deformation amount of the surrounding rock; continuously monitoring for a period of time, and calculating the deformation rate of the working face end of the stress-strain measuring rod; and comprehensively obtaining the soft rock tunnel large deformation grading result according to the calculated strength stress ratio, deformation rate and final deformation amount of the surrounding rock. The method can conveniently and quickly grade the large deformation of the soft rock tunnel, the process is simple, the result is accurate and has timeliness, and the method can be widely used in engineering.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering construction technology, specifically to a method for classifying large deformations by combining drilling parameters and borehole testing. Background Technology

[0002] During tunnel construction in complex and challenging mountainous areas, the complex geological environment, the presence of numerous weak surrounding rocks with poor conditions, and high ground stress all contribute to significant deformation problems of varying degrees, severely impacting construction. Large deformation in soft rock refers to substantial deformation occurring within the soft rock mass during tunnel construction and operation due to geological conditions and engineering design. This deformation not only affects tunnel stability but also increases the difficulty and cost of construction and maintenance. Therefore, the primary task during construction is to accurately determine the level of large deformation and take targeted measures to prevent and control different levels of large deformation.

[0003] Extensive research has been conducted by scholars both domestically and internationally on the problem of large deformation in tunnel surrounding rock. Various approaches have been adopted, employing multiple indicators to define, delineate, and classify large deformations. Empirical formulas or mathematical models are frequently used for calculation and judgment, but these methods involve numerous factors and complex indicator systems, making it difficult to quickly and accurately determine the level of large deformation. Therefore, to better and more rapidly identify the potential level of large deformation based on tunnel excavation conditions, and to provide a basis for adjusting construction methods and formulating support measures, it is necessary to propose a rapid and effective method for classifying large deformations. Summary of the Invention

[0004] This invention provides a method for classifying large deformations by combining drilling parameters and borehole test data during construction. This method is applicable to the classification of large deformations in soft rock tunnels, and the process is simple and the results are accurate. This solves the problem that existing technologies cannot simultaneously achieve simplicity, applicability and accuracy.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for classifying large deformations by combining drilling parameters and borehole testing, the specific steps of which are as follows:

[0007] S1. Classify the surrounding rock of the tunnel according to the "Engineering Rock Mass Classification Standard" and obtain the engineering rock mass quality index BQ;

[0008] S2. Obtaining Rock Mass Strength: The strength R of the soft rock mass in front of the tunnel face is obtained by drilling holes and using the drilling parameters during the drilling process. c ;

[0009] S3. Drive an elastic stress-strain measuring rod that can deform with the surrounding rock into the borehole. Multiple test sections are arranged along the axial direction on the elastic stress-strain measuring rod, and strain gauges are arranged at the test sections.

[0010] S4. Measure the strain at each measuring point on the deepest test section of the stress-strain probe and convert it to obtain the in-situ stress σ; use the measured in-situ stress and rock mass strength to calculate the rock mass strength-stress ratio R. c / σ, thus obtaining the first-class large deformation level for soft rock tunnels;

[0011] S5. Measure the strain at each measuring point on multiple test sections along the longitudinal direction of the stress-strain measuring rod, interpolate the calculation results to obtain the curvature function of the measuring rod, and calculate the vertical deformation function of the stress-strain measuring rod through integration; calculate the final deformation of the surrounding rock through the formula and fit the deformation curve of the longitudinal section of the tunnel surrounding rock; determine the large deformation level of the second type of soft rock tunnel based on the obtained final deformation U of the surrounding rock.

[0012] S6. Continuously monitor the deformation of the stress-strain measuring rod for a period of time, and calculate the deformation rate v at the end of the stress-strain measuring rod face. p The large deformation level of the third category of soft rock tunnels was determined.

[0013] S7, combined with the deformation rate v of the surrounding rock p Deformation U and rock mass strength stress ratio R c / σ, based on the principle of unfavorable conditions, comprehensively determine the large deformation level of soft rock tunnels.

[0014] Furthermore, in step S3, five test sections are evenly distributed along the axial direction on the stress-strain measuring rod, with four strain gauges arranged circumferentially on the inner surface of each test section, and an angle measuring instrument is provided at the end of the stress-strain measuring rod.

[0015] Further, in step S4, the rock mass strength stress ratio R is obtained. c The specific method for / σ is as follows:

[0016] Based on the strain ε measured by the stress-strain measuring rod and the material parameters of the rod, combined with the deflection angle θ of the rod, the transverse horizontal stress σ on the stress-strain measuring rod is calculated. x and vertical stress σ y ;

[0017] σ x =ε x E / cosθ

[0018] σ y =ε y E / cosθ

[0019] Where: E is the elastic modulus of the stress-strain measuring rod;

[0020] The formula for calculating the maximum ground stress σ is:

[0021]

[0022] The calculated maximum geostress σ and the soft rock mass strength R c Calculate the rock mass strength-stress ratio R c / σ.

[0023] Furthermore, based on the rock mass strength-stress ratio R c The criteria for determining the large deformation level of a Class I soft rock tunnel are as follows:

[0024] When the rock mass strength-stress ratio is between 0.25 and 0.5, the large deformation level of a high-stress soft rock tunnel is classified as Level I; when the rock mass strength-stress ratio is between 0.15 and 0.25, the large deformation level is classified as Level II; when the rock mass strength-stress ratio is between 0.05 and 0.15, the large deformation level is classified as Level III; and when the rock mass strength-stress ratio is less than 0.05, the large deformation level is classified as Level IV.

[0025] Furthermore, in step S5, the method for calculating the deformation U of the surrounding rock is as follows:

[0026] S51. Based on the strain at each test section of the stress-strain measuring rod, calculate the longitudinal strain values ​​of the upper and lower surfaces of each test section; calculate the beam bending curvature ρ at each test section based on the beam bending geometry relationship in mechanics of materials.

[0027]

[0028] Where: r is the radius of the stress-strain measuring rod;

[0029] S52. Based on the principle of cubic spline interpolation, interpolate the test results to obtain the function S of the stress-strain measuring rod curvature ρ and the distance x from the fixed end in the deep soft rock. i (x);

[0030] S i (x)=a i +b i (xx i )+c i (xx i ) 2 +d i (xx i ) 3

[0031] Where: i is the interval number of the piecewise function of the cubic spline curve, a i b i c i d i Let x be the undetermined fitting parameters for the corresponding interval. i This represents the starting position of the i-th segment;

[0032] S53. Calculate the vertical deformation y of the stress-strain measuring rod using the curvature function of the stress-strain measuring rod;

[0033] S54. Calculate the deformation of the surrounding rock at each test section by measuring the vertical deformation of the stress-strain measuring rods at the five test sections. Then, calculate the final deformation of the surrounding rock from the deformation of the surrounding rock at each test section. Take the average value as the final deformation result of the surrounding rock and determine the large deformation level of the second type of soft rock tunnel.

[0034] Furthermore, in step S53, the method for calculating the vertical deformation y of the stress-strain measuring rod is as follows:

[0035] Based on the small deflection assumption in mechanics of materials, the curvature expression is:

[0036]

[0037] The spline curve function obtained by interpolation is integrated twice with respect to x to obtain the vertical deformation y of the stress-strain measuring rod as a function of distance x from the fixed end of the soft rock deep part;

[0038] y(x)=∫[∫S i (x)dx+C1]dx+C2;

[0039] Where: C1 and C2 are undetermined constants for integration;

[0040] The following formulas apply to the relationship between the deformation of the surrounding rock at different test sections of the tunnel and the final deformation of the surrounding rock:

[0041]

[0042] Among them: U x For the deformation of the surrounding rock at different cross sections; U r∞ denoted as _x_, where _x_ is the final deformation of the surrounding rock; _x* is the ratio of the distance from a certain section to the tunnel face to the tunnel radius, where x*<0 indicates the section is after the tunnel face, and x*>0 indicates the section is before the tunnel face; _BQ_ is the tunnel surrounding rock classification index; _p1_, _p2_..._p9_ are calculation parameters.

[0043] The following equations can be established to solve for the rigid body displacement of the stress-strain measuring rod by using the ratio of the deformation of the surrounding rock at the test section to the final deformation of the surrounding rock and the vertical deformation y of the measuring rod at each point:

[0044]

[0045] In the formula: ΔU is the rigid body displacement of the stress-strain measuring rod, y i y j The vertical deformation of the measuring rod at points i and j; denoted as the ratio of the deformation of the surrounding rock at sections i and j to the final deformation of the surrounding rock;

[0046] The above equations were established for each monitoring point, and several ΔU values ​​were obtained. The average value was taken as the final rigid body displacement result. The deformation of the surrounding rock at each test section was the sum of the rigid body displacement of the stress-strain measuring rod and the vertical deformation of the stress-strain measuring rod.

[0047] U x =△U+y.

[0048] Furthermore, in step S54, based on the calculation formula between the deformation amount of the surrounding rock at different cross sections and the final deformation amount of the surrounding rock, the deformation amount of the surrounding rock at different cross sections is substituted into the calculation formula to calculate the final deformation amount of the surrounding rock, and the average value of the calculation results of each cross section is taken as the final deformation amount of the surrounding rock.

[0049] Furthermore, the standard for determining the large deformation level of Class II high-stress soft rock tunnels based on the final deformation of the surrounding rock is as follows:

[0050] When the final deformation of the surrounding rock U < 30%U0, the deformation level is Level 1; when the final deformation of the surrounding rock is 30%U0≤U < 50%U0, the deformation level is Level 2; when the final deformation of the surrounding rock is 50%U0≤U < 80%U0, the deformation level is Level 3; when the final deformation of the surrounding rock is 80%U0≤U < 100%U0, the deformation level is Level 4; where U0 is the net displacement control benchmark value.

[0051] Further, in step S6, the deformation rate v of the stress-strain measuring rod p The calculation method is as follows:

[0052] By continuously monitoring the deformation of the stress-strain measuring rod over a period of time, the deformation rate v of the stress-strain measuring rod at the tunnel face end is calculated using the following formula. p :

[0053]

[0054] Where: △U t Δt represents the deformation of the end face of the stress-strain measuring rod over a period of time, where Δt is the measurement time.

[0055] Furthermore, according to the deformation rate v p The criteria for judging the large deformation level of Category III high-stress soft rock tunnels are as follows: when the deformation rate is between 10 and 30 mm / d, the deformation rate is classified as low speed and the deformation level is Level 1; when the deformation rate is between 30 and 50 mm / d, the deformation rate is classified as medium speed and the deformation level is Level 2; when the deformation rate is between 50 and 80 mm / d, the deformation rate is classified as high speed and the deformation level is Level 3; and when the deformation rate is greater than 80 mm / d, the deformation rate is classified as extremely high and the deformation level is Level 4.

[0056] The beneficial effects of this invention are:

[0057] This invention obtains basic classification parameters by drilling holes at the tunnel face and inserting stress-strain measuring rods. Classification results can then be obtained through simple calculations, significantly improving classification efficiency. It overcomes the limitations of existing classification methods for large deformations in soft rock tunnels, possessing wider applicability in engineering and ensuring the accuracy and timeliness of calculations for large deformation classifications in soft rock tunnels. Attached Figure Description

[0058] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 This is a flowchart of the method of the present invention.

[0060] Figure 2 This is a front view of the stress-strain measuring rod in this invention.

[0061] Figure 3 This is a side view schematic diagram of the stress-strain measuring rod in this invention.

[0062] Figure 4 This is a front view of the arrangement of stress and strain measuring rods in this invention.

[0063] Figure 5 This is a side view of the arrangement of stress and strain measuring rods in this invention.

[0064] Figure 6 This is a schematic diagram of an angle measuring instrument positioned at the end of a stress-strain measuring rod.

[0065] Figure 7(a) , 7(b) This is a curve showing the longitudinal deformation of the tunnel calculated and predicted using this method. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0067] A method for classifying large deformations by combining drilling parameters and borehole testing, the specific steps of which are as follows:

[0068] S1. Classify the surrounding rock of the tunnel according to the "Engineering Rock Mass Classification Standard" and obtain the engineering rock mass quality index BQ;

[0069] S2. Obtaining Rock Mass Strength: The strength R of the soft rock mass in front of the tunnel face can be obtained by drilling holes and using the drilling parameters during the drilling process. c ;

[0070] S3. Drive an elastic stress-strain measuring rod that can deform with the surrounding rock into the borehole. Multiple test sections are arranged along the axial direction on the elastic stress-strain measuring rod, and strain gauges are arranged at the test sections.

[0071] S4. Measure the strain at each measuring point on the deepest test section of the stress-strain probe and convert it to obtain the in-situ stress σ; use the measured in-situ stress and rock mass strength to calculate the rock mass strength-stress ratio R. c / σ, thus obtaining the first-class large deformation level for soft rock tunnels;

[0072] S5. Measure the strain at each measuring point on multiple test sections along the longitudinal direction of the stress-strain measuring rod, interpolate the calculation results to obtain the curvature function of the measuring rod, and calculate the vertical deformation function of the stress-strain measuring rod through integration; calculate the final deformation of the surrounding rock through the formula and fit the deformation curve (LDP curve) of the longitudinal profile of the tunnel surrounding rock; determine the large deformation level of the second type of soft rock tunnel based on the obtained final deformation U of the surrounding rock.

[0073] S6. Continuously monitor the deformation of the stress-strain measuring rod for a period of time, and calculate the deformation rate v at the end of the stress-strain measuring rod face. p The large deformation level of the third category of soft rock tunnels was determined.

[0074] S7, combined with the deformation rate v of the surrounding rock p Deformation U and rock mass strength stress ratio R c / σ, based on the principle of unfavorable conditions, comprehensively determine the large deformation level of soft rock tunnels.

[0075] The detailed testing methods and data processing procedures are as follows:

[0076] Specifically, in step S3, five test sections are evenly distributed along the axial direction on the stress-strain measuring rod, with four strain gauges arranged circumferentially on the inner surface of each test section, such as... Figure 2 , Figure 3 As shown; the stress-strain measuring rod is driven into the borehole at the tunnel face, as indicated. Figure 3 , Figure 4 As shown. Furthermore, since the stress-strain measuring rod may have a deflection angle, an angle measuring instrument is installed at the end of the stress-strain measuring rod.

[0077] In step S4, the rock mass strength stress ratio R is determined. c The specific method for / σ is as follows:

[0078] Based on the strain ε measured by the stress-strain measuring rod and the material parameters of the rod, combined with the deflection angle θ of the rod, the transverse horizontal stress σ on the stress-strain measuring rod can be calculated. x and vertical stress σ y ;

[0079] Equation 1: σ x =ε x E / cosθ

[0080] Equation 2: σ y =ε y E / cosθ

[0081] Where: E is the elastic modulus of the stress-strain measuring rod; thus, the maximum ground stress σ can be determined:

[0082] Formula 3:

[0083] The calculated maximum geostress σ and the soft rock mass strength R c The rock mass strength-stress ratio R can then be calculated. c / σ, determine the classification level of large deformation of the first type of soft rock tunnel.

[0084] Based on the rock mass strength-stress ratio R c The criteria for determining the deformation grade of the surrounding rock are detailed in Table 1, and are as follows:

[0085] When the rock mass strength-stress ratio is between 0.25 and 0.5, the large deformation level of a high-stress soft rock tunnel is classified as Level I; when the rock mass strength-stress ratio is between 0.15 and 0.25, the large deformation level is classified as Level II; when the rock mass strength-stress ratio is between 0.05 and 0.15, the large deformation level is classified as Level III; and when the rock mass strength-stress ratio is less than 0.05, the large deformation level is classified as Level IV.

[0086] Table 1. Classification Standards for Class I Deformation Grades (Strength-Stress Ratio)

[0087]

[0088] In step S5, the method for calculating the deformation U of the surrounding rock is as follows:

[0089] First, the displacement and deformation process of the stress-strain measuring rod is simplified, considering it as a rigid body displacement that occurs first with the soft rock, followed by deformation of the measuring rod due to the different displacements of different parts of the soft rock. Since the stress-strain measuring rod is relatively long, the end of the measuring rod inside the borehole can be considered a fixed end, where the deformation of the surrounding rock and the vertical displacement of the stress-strain measuring rod are both zero.

[0090] S51. Based on the strain of each test section of the stress-strain measuring rod, the longitudinal strain values ​​of the upper and lower surfaces of the five test sections are calculated; the beam bending curvature ρ at each test section is calculated based on the beam bending geometry relationship in mechanics of materials.

[0091] Formula 4:

[0092] Where: r is the radius of the stress-strain measuring rod.

[0093] S52. Based on the principle of cubic spline interpolation, interpolate the test results to obtain the function S of the stress-strain measuring rod curvature ρ and the distance x from the fixed end in the deep soft rock. i (x);

[0094] The interpolation method is as follows:

[0095] The basic form of the spline curve function is (Equation 5): S i (x)=a(xx i ) 3 +b(xx i ) 2 +c(xx i )+d;

[0096] The spline curve passes through the interpolation point, i.e. (Equation 6): S i (x i )=y i S i (xi+1 )=y i+1 .

[0097] Satisfying differential continuity (Equation 7): S′ i (x i+1 )=S′ i+1 (x i+1 ), S″ i (x i+1 )=S″ i+1 (x i+1 ).

[0098] Where S i (x) is the spline interpolation function, x i y i Let a, b, c, and d be the coordinates of the known points, and a, b, c, and d be constants.

[0099] S53. The vertical deformation of the stress-strain measuring rod can be calculated using the curvature function of the stress-strain measuring rod.

[0100] Based on the small deflection assumption in mechanics of materials, the expression for curvature ρ is:

[0101] Formula 6:

[0102] Therefore, by integrating the spline curve function (Equation 5) obtained by interpolation twice with respect to x, we can obtain the function y(x) of the vertical deformation y of the stress-strain measuring rod as a function of the distance x from the fixed end of the soft rock deep part:

[0103] Formula 7: y(x)=∫[∫S i (x)dx+C1]dx+C2.

[0104] Where C1 and C2 are undetermined constants for integration.

[0105] The following formulas relate the deformation at different test sections of the tunnel to the final deformation:

[0106] Formula 8:

[0107] Among them: U x For the deformation of the surrounding rock at different cross sections; U r∞ denoted as , where is the final deformation of the surrounding rock; x* is the ratio of the distance from a certain section to the tunnel face to the tunnel radius, x*<0 indicates the section is after the tunnel face, and x*>0 indicates the section is before the tunnel face; BQ is the tunnel surrounding rock classification index; p1, p2...p9 are calculation parameters, selected by interpolation according to Tables 2 and 3.

[0108] Table 2 Parameter values ​​(x<0)

[0109] Burial depth <![CDATA[p1]]> <![CDATA[p2]]> <![CDATA[p3]]> <![CDATA[p4]]> <![CDATA[p5]]> <![CDATA[p6]]> 100 0.185136 0.000136 0.028811 -0.000345 -0.643230 0.712535 200 0.214468 0.000127 0.047077 -0.000138 -0.569442 0.589863 300 0.213224 0.000093 0.081506 -0.000440 -0.811229 0 400 0.124963 0.002164 0.134810 0.007251 -1.129572 3.107974 500 0.407024 0.003173 0.430409 0.013567 -6.920099 0

[0110] Table 3 Parameter values ​​(x>0)

[0111] Burial depth <![CDATA[p1]]> <![CDATA[p2]]> <![CDATA[p3]]> <![CDATA[p4]]> <![CDATA[p5]]> <![CDATA[p6]]> <![CDATA[p7]]> <![CDATA[p8]]> <![CDATA[p9]]> 100 0.267998 -0.000312 0 0.700272 -0.563461 -0.001260 0 0.599310 0.574235 200 0.243497 -0.001130 1.549152e-6 0.180743 0.087168 -0.004785 6.584718e-6 0.139921 0.090688 300 0.213685 -0.000971 1.351156e-6 0.170296 0.064002 -0.004811 6.696621e-6 0.134251 0.067169 400 0.178584 -0.000759 9.739105e-7 0.142372 0.054677 -0.004841 6.577050e-6 0.117858 0.055755 500 0.217034 -0.001076 1.461192e-6 0.083573 0.057961 -0.005089 6.925480e-6 0.074315 0.058418

[0112] Equation 10 and the calculated vertical deformation y of the measuring rod at each point can be used to establish an equation to solve for the rigid body displacement of the measuring rod under stress and strain:

[0113] Formula 9:

[0114] In Equation 11: ΔU is the rigid body displacement of the stress-strain measuring rod, y i y j The vertical deformation of the stress-strain measuring rod at points i and j; Let i be the ratio of the deformation of the surrounding rock at sections i and j to the final deformation of the tunnel.

[0115] Equations were established for each point, and several ΔU values ​​were obtained. The average value was taken as the final rigid body displacement result. The deformation of the surrounding rock at each test section was the sum of the rigid body displacement of the stress-strain measuring rod and the vertical deformation of the stress-strain measuring rod.

[0116] Equation 10: U x =△U+y.

[0117] The deformation of the surrounding rock at the five test sections can be calculated from Equation 12 and the vertical deformation at the five measuring points on the stress-strain measuring rod. The final deformation of the surrounding rock is calculated from Equation 10 and the deformation of the surrounding rock at each section. The average value of the calculation results is taken as the final deformation of the surrounding rock.

[0118] Based on the calculated final deformation of the surrounding rock, the large deformation level of the second type of high-stress soft rock tunnel is determined according to Table 4. Specifically, when the final deformation of the surrounding rock U < 30%U0, the deformation level is Level 1; when the final deformation of the surrounding rock is 30%U0 ≤ U < 50%U0, the deformation level is Level 2; when the final deformation of the surrounding rock is 50%U0 ≤ U < 80%U0, the deformation level is Level 3; and when the final deformation of the surrounding rock is 80%U0 ≤ U < 100%U0, the deformation level is Level 4; where U0 is the net displacement control benchmark value.

[0119] Table 4 Classification Standards for Deformation Grades (Final Deformation of Surrounding Rock)

[0120]

[0121] In step S6, the deformation rate v of the stress-strain measuring rod p The calculation method is as follows:

[0122] By continuously monitoring the deformation of the stress-strain measuring rod over a period of time, the deformation rate v of the stress-strain measuring rod at the tunnel face end can be calculated using Equation 13. p :

[0123] Formula 11:

[0124] Where: △U t Δt represents the deformation of the end face of the stress-strain measuring rod over a period of time, where Δt is the measurement time.

[0125] Based on the calculated deformation rate v p The criteria for determining the large deformation level of Category III high-stress soft rock tunnels are detailed in Table 5. Specifically, when the deformation rate is between 10 and 30 mm / d, the deformation rate is classified as low-speed and the deformation level is Level 1; when the deformation rate is between 30 and 50 mm / d, the deformation rate is classified as medium-speed and the deformation level is Level 2; when the deformation rate is between 50 and 80 mm / d, the deformation rate is classified as high-speed and the deformation level is Level 3; and when the deformation rate is greater than 80 mm / d, the deformation rate is classified as extremely high and the deformation level is Level 4.

[0126] Table 5. Classification Standards for Three Types of Deformation Levels (Deformation Rate)

[0127] Deformation level Level 1 Level 2 Level 3 Level 4 <![CDATA[Deformation rate v p (mm / d)]]> 10～30 30～50 50～80 ＞80 Deformation rate classification low speed medium speed high speed Extremely high

[0128] In step S7, the three types of large deformation classification levels for soft rock tunnels are compared. Based on the principle of unfavorable conditions, the more dangerous deformation level is selected as the final large deformation level for high ground stress soft rock tunnels.

[0129] Experimental Example

[0130] Based on a tunnel on the Beijing-Shanghai High-Speed ​​Railway, with a span of 7m and a burial depth of 200m, the surrounding rock has poor integrity. According to the "Engineering Rock Mass Classification Standard," the surrounding rock was classified, and the basic quality index BQ = 195.9, classifying it as Class V surrounding rock. Stress-strain measuring rods were driven into the tunnel face at a certain section during construction.

[0131] According to the drilling parameters, the rock mass strength in front of the drilling face is 1.84 MPa.

[0132] After one day of monitoring, the following data points were obtained:

[0133] Table 6 Monitoring Data

[0134]

[0135] Based on the test values ​​in Table 6 and the calculation of ground stress using Equations 1, 2 and 3, the maximum value is taken as 15.54 MPa.

[0136] Strength-stress ratio is

[0137] According to Table 1, the large deformation level of a type I soft rock tunnel is Level III.

[0138] The curvature values ​​at each point are calculated using Equation 4.

[0139] Based on the principle of cubic spline interpolation, the test results are interpolated to obtain the function S of the stress-strain measuring rod bending curvature ρ and the distance x from the fixed end in the deep soft rock. i (x).

[0140] The expression for a piecewise cubic spline curve is:

[0141] Equation 12: S i (x)=a(xx i ) 3 +b(xx i ) 2 +c(xx i )+dx∈[x i ,x i +△x]

[0142] The parameter fitting results are shown in Table 7.

[0143] Table 7 Fitting results of rod curvature parameters

[0144] <![CDATA[a i ]]> <![CDATA[b i ]]> <![CDATA[c i ]]> <![CDATA[d i ]]> 0.00100 -0.000592 0.000198 0.000889 0.000579 -0.000292 -0.000686 0.000595 0.000459 0.001445 0.000467 0.000196 0.000459 0.002822 0.004734 0.002567

[0145] By integrating x twice consecutively, we can obtain the vertical deformation y of the measuring rod as a function of the distance x from the fixed end in the deep soft rock.

[0146] y(x)=∫[∫S i (x)dx+C1]dx+C2

[0147] By substituting the x-value, the vertical deformation at each point can be calculated. The calculation results are shown in Table 8.

[0148] Table 8 Vertical deformation at various points on the measuring rod (mm)

[0149] measuring point 1 2 3 4 5 Vertical deformation / mm 4.6 9.8 15.7 22.1 31.3

[0150] The rigid body displacement was calculated using Equation 11, and the average value was 28.2 mm.

[0151] The deformation of the surrounding rock at the tunnel face can be calculated using Equation 12, and the result is 59.5 mm.

[0152] The final deformation of the surrounding rock was calculated using the longitudinal deformation curve fitting formula (Equation 10), and the average value was 230.2 mm.

[0153] The control benchmark for the tunnel's net displacement is 300mm. The calculated results are greater than 50%U0 and less than 80%U0. According to Table 4, the large deformation level of the Class II soft rock tunnel is Level III.

[0154] Calculate the deformation rate:

[0155] According to Table 5, the large deformation level of the three types of soft rock tunnels is Level III.

[0156] Comparing the large deformation levels obtained from three different criteria, the most dangerous one was selected as the final deformation level. The final result is: the large deformation level of this soft rock tunnel is level three.

[0157] As can be seen from the above embodiments, based on the method provided by the present invention, it is only necessary to obtain the parameters and input them into the computer program module set according to the above method to directly output the theoretical prediction results, which greatly improves the classification efficiency.

[0158] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for classifying large deformations by combining drilling parameters and borehole testing, characterized in that: The specific steps are as follows: S1. Classify the surrounding rock of the tunnel according to the "Engineering Rock Mass Classification Standard" and obtain the engineering rock mass quality index BQ; S2. Obtaining Rock Mass Strength: The strength R of the soft rock mass in front of the tunnel face is obtained by drilling holes and using the drilling parameters during the drilling process. c ; S3. Drive an elastic stress-strain measuring rod that can deform with the surrounding rock into the borehole. Multiple test sections are arranged along the axial direction on the elastic stress-strain measuring rod, and strain gauges are arranged at the test sections. S4. Measure the strain at each measuring point on the deepest test section of the stress-strain probe and convert it to obtain the in-situ stress σ; use the measured in-situ stress and rock mass strength to calculate the rock mass strength-stress ratio R. c / σ, thus obtaining the first-class large deformation level for soft rock tunnels; S5. Measure the strain at each measuring point on multiple test sections along the longitudinal direction of the stress-strain measuring rod, interpolate the calculation results to obtain the curvature function of the measuring rod, and calculate the vertical deformation function of the stress-strain measuring rod through integration; calculate the final deformation of the surrounding rock through the formula and fit the deformation curve of the longitudinal section of the tunnel surrounding rock; determine the large deformation level of the second type of soft rock tunnel based on the obtained final deformation U of the surrounding rock. S6. Continuously monitor the deformation of the stress-strain measuring rod for a period of time, and calculate the deformation rate v at the end of the stress-strain measuring rod face. p The large deformation level of the third category of soft rock tunnels was determined. S7, combined with the deformation rate v of the surrounding rock p Deformation U and rock mass strength stress ratio R c / σ, based on the principle of unfavorable conditions, comprehensively determine the large deformation level of soft rock tunnels.

2. The large deformation classification method combining drilling parameters and borehole testing according to claim 1, characterized in that: In step S3, five test sections are evenly distributed along the axial direction on the stress-strain measuring rod, with four strain gauges arranged circumferentially on the inner surface of each test section, and an angle measuring instrument is installed at the end of the stress-strain measuring rod.

3. The large deformation classification method combining drilling parameters and borehole testing according to claim 2, characterized in that: In step S4, the rock mass strength stress ratio R is obtained. c The specific method for / σ is as follows: Based on the strain ε measured by the stress-strain measuring rod and the material parameters of the rod, combined with the deflection angle θ of the rod, the transverse horizontal stress σ on the stress-strain measuring rod is calculated. x and vertical stress σ y ; s x =e x E / cosθ s y =e y E / cosθ Where: E is the elastic modulus of the stress-strain measuring rod; The formula for calculating the maximum ground stress σ is: The calculated maximum geostress σ and the soft rock mass strength R c Calculate the rock mass strength-stress ratio R c / σ.

4. The large deformation classification method combining drilling parameters and borehole testing according to claim 3, characterized in that: Based on the rock mass strength-stress ratio R c The criteria for determining the large deformation level of a Class I soft rock tunnel are as follows: When the rock mass strength-stress ratio is between 0.25 and 0.5, the large deformation level of a high-stress soft rock tunnel is classified as Level I; when the rock mass strength-stress ratio is between 0.15 and 0.25, the large deformation level is classified as Level II; when the rock mass strength-stress ratio is between 0.05 and 0.15, the large deformation level is classified as Level III; and when the rock mass strength-stress ratio is less than 0.05, the large deformation level is classified as Level IV.

5. The large deformation classification method combining drilling parameters and borehole testing according to claim 2, characterized in that: In step S5, the final deformation U of the surrounding rock is calculated as follows: S51. Based on the strain measured at each cross-section using the stress-strain measuring rod, calculate the longitudinal strain values ​​of the upper and lower surfaces of each cross-section; calculate the beam bending curvature ρ at each test cross-section based on the beam bending geometry relationship in mechanics of materials. Where: r is the radius of the stress-strain measuring rod; S52. Based on the principle of cubic spline interpolation, interpolate the test results to obtain the function S of the stress-strain measuring rod curvature ρ and the distance x from the fixed end in the deep soft rock. i (x); S i (x)=a i +b i (x-x i )+c i (x-x i ) 2 +d i (x-x i ) 3 Where: i is the interval number of the piecewise function of the cubic spline curve, a i b i c i d i Let x be the undetermined fitting parameters for the corresponding interval. i This represents the starting position of the i-th segment; S53. Calculate the vertical deformation y of the stress-strain measuring rod using the curvature function of the stress-strain measuring rod; S54. Calculate the deformation of the surrounding rock at each test section by measuring the vertical deformation of the stress-strain measuring rods at the five test sections. Then, calculate the final deformation of the surrounding rock from the deformation of the surrounding rock at each test section. Take the average value as the final deformation result of the surrounding rock and determine the large deformation level of the second type of soft rock tunnel.

6. The large deformation classification method combining drilling parameters and borehole testing according to claim 5, characterized in that: In step S53, the method for calculating the vertical deformation y of the stress-strain measuring rod is as follows: Based on the small deflection assumption in mechanics of materials, the curvature expression is: The spline curve function obtained by interpolation is integrated twice with respect to x to obtain the vertical deformation y of the stress-strain measuring rod as a function of distance x from the fixed end of the soft rock deep part; y(x)=∫[∫S i (x)dx+C1]dx+C2; Where: C1 and C2 are undetermined constants for integration; The following formula applies to the relationship between the deformation of the surrounding rock at different cross-sections of the tunnel and the final deformation of the surrounding rock: Among them: U x For the deformation of the surrounding rock at different cross sections; U r∞ denoted as _x_, where _x_ is the final deformation of the surrounding rock; _x* is the ratio of the distance from a certain section to the tunnel face to the tunnel radius, where x*<0 indicates the section is after the tunnel face, and x*>0 indicates the section is before the tunnel face; _BQ_ is the tunnel surrounding rock classification index; _p1_, _p2_..._p9_ are calculation parameters. Based on the ratio of the deformation of the surrounding rock at the test section to the final deformation of the tunnel and the calculated vertical deformation y of the measuring rod at each point, the following equations are established to solve for the rigid body displacement of the stress-strain measuring rod: In the formula: ΔU is the rigid body displacement of the stress-strain measuring rod, y i y j The vertical deformation of the measuring rod at points i and j; denoted as the ratio of the deformation of the surrounding rock at sections i and j to the final deformation of the tunnel. The above equations were established for each monitoring point, and several ΔU values ​​were obtained. The average value was taken as the final rigid body displacement result. The deformation of the surrounding rock at each test section was the sum of the rigid body displacement of the stress-strain measuring rod and the vertical deformation of the stress-strain measuring rod. U x =△U+y。 7. The large deformation classification method combining drilling parameters and borehole testing according to claim 6, characterized in that: In step S54, based on the calculation formula between the deformation amount of the surrounding rock at different cross sections and the final deformation amount of the surrounding rock, the deformation amount of the surrounding rock at different cross sections is substituted into the calculation formula to calculate the final deformation amount of the surrounding rock. The average value of the calculation results for each cross section is taken as the final deformation amount of the surrounding rock.

8. The large deformation classification method combining drilling parameters and borehole testing according to claim 7, characterized in that: The standard for determining the large deformation level of Class II high-stress soft rock tunnels based on the final deformation of the surrounding rock is as follows: When the final deformation of the surrounding rock U < 30%U0, the deformation level is Level 1; when the final deformation of the surrounding rock is 30%U0≤U < 50%U0, the deformation level is Level 2; when the final deformation of the surrounding rock is 50%U0≤U < 80%U0, the deformation level is Level 3; when the final deformation of the surrounding rock is 80%U0≤U < 100%U0, the deformation level is Level 4; where U0 is the net displacement control benchmark value.

9. The large deformation classification method combining drilling parameters and borehole testing according to claim 1, characterized in that: In step S6, the deformation rate v of the stress-strain measuring rod p The calculation method is as follows: By continuously monitoring the deformation of the stress-strain measuring rod over a period of time, the deformation rate v of the stress-strain measuring rod at the tunnel face end is calculated using the following formula. p : Where: △U t Δt represents the deformation of the end face of the stress-strain measuring rod over a period of time, where Δt is the measurement time.

10. The large deformation classification method combining drilling parameters and borehole testing according to claim 9, characterized in that: According to the deformation rate v p The criteria for judging the large deformation level of Category III high-stress soft rock tunnels are as follows: when the deformation rate is between 10 and 30 mm / d, the deformation rate is classified as low speed and the deformation level is Level 1; when the deformation rate is between 30 and 50 mm / d, the deformation rate is classified as medium speed and the deformation level is Level 2; when the deformation rate is between 50 and 80 mm / d, the deformation rate is classified as high speed and the deformation level is Level 3; and when the deformation rate is greater than 80 mm / d, the deformation rate is classified as extremely high and the deformation level is Level 4.

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