CN115688237A - Geostress inversion analysis method and system for tunnel soft rock deformation grade evaluation - Google Patents
Geostress inversion analysis method and system for tunnel soft rock deformation grade evaluation Download PDFInfo
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Abstract
The invention discloses a ground stress inversion analysis method and a ground stress inversion analysis system for tunnel soft rock deformation grade evaluation, which are used for obtaining physical and mechanical parameters of surrounding rocks of a tunnel site area and ground stress drilling data and constructing a three-dimensional geomechanical model of the tunnel site area; carrying out coordinate axis transformation on the actually measured ground stress data; calculating an initial ground stress field of an inversion tunnel site area based on multiple regression; checking the significance of the inversion result and the inversion coefficient; and calculating to obtain the crustal stress distribution at the axis of the tunnel, and evaluating the large deformation grade of the tunnel soft rock based on an intensity stress ratio method. The method has the advantages of simplicity, quickness and high prediction precision for the inversion of the ground stress level of the mountain tunnel and the evaluation of the deformation level of the extruding surrounding rock, can greatly improve the prediction efficiency, is better applied to guiding and dynamically adjusting the construction process and the supporting time of the large soft rock deformation section of the tunnel, and obviously improves the construction safety of the large soft rock deformation section of the tunnel.
Description
Technical Field
The invention relates to the field of geotechnical, in particular to a ground stress inversion analysis method and system for tunnel soft rock deformation grade evaluation.
Background
At present, the crustal stress characteristics of the tunnel site area can be obtained by adopting crustal stress measurement technology. However, due to the limitation of high cost, large-scale geostress measurement cannot be performed in the tunnel site area, and therefore, it is particularly necessary to obtain the geostress characteristics of the whole tunnel site area by using the inversion of the only geostress measurement result. In addition, for the soft rock tunnel, the ground stress size and distribution characteristics are the internal power of soft rock deformation and are also important basis of tunnel design. The engineer will simply fit the measured ground stress results linearly and use it as a basis for design. However, the method cannot accurately acquire the geostress value and the distribution characteristics of the geostress value in the tunnel site area at all, so that the prediction accuracy of the large deformation grade of the soft rock of the tunnel is low.
Therefore, a method for simply and accurately inverting the crustal stress of the tunnel site area and accurately predicting the large deformation grade of the soft rock of the tunnel must be designed.
Disclosure of Invention
The invention provides a ground stress inversion analysis method for tunnel soft rock deformation grade evaluation, aiming at the problem of low prediction precision of tunnel soft rock large deformation grade in a tunnel design stage.
The invention is realized by the following technical scheme:
a geostress inversion analysis method for tunnel soft rock deformation grade evaluation comprises the following steps:
step 1, acquiring surrounding rock mechanical parameters and an actually measured crustal stress result of a tunnel site area;
step 3, carrying out coordinate axis conversion on the ground stress result actually measured in the step 1 to obtain a stress component corresponding to the ground stress result actually measured;
and 6, substituting the long axial crustal stress value of the tunnel into a crustal stress regression equation of the tunnel site area to obtain the crustal stress characteristic of the tunnel site area and predict the deformation grade of the soft rock of the tunnel.
Preferably, the mechanical parameters of the surrounding rocks in the step 1 comprise elastic modulus, weight and poisson ratio.
Preferably, in the step 1, the stress value of the tunnel site area is measured by adopting a hydraulic fracturing method or a stress relieving method.
Preferably, the inversion range of the ground stress field in the step 2 is the whole tunnel engineering area, the tunnel engineering area is expanded to a certain range to form the inversion range of the ground stress field, and a ridge line and a valley line are used as boundaries of the inversion range of the ground stress field.
Preferably, the calculation method of the stress component is as follows:
the original coordinate systems are marked as x, y and z, the new coordinate systems are marked as x ', y ', z ', and the direction cosines between the two coordinate systems are marked as a, b and c.
Preferably, the method for establishing the three-dimensional geomechanical model in the step 4 is as follows:
s41, establishing a plurality of three-dimensional geomechanical models according to topographic data of the inversion range of the ground stress field;
s42, endowing the surrounding rock mechanical parameters to each rock-soil body in the three-dimensional geomechanical model by adopting an elastic constitutive relation;
and S43, setting different structural boundary conditions for each three-dimensional geomechanical model according to the calculation working conditions.
Preferably, the setting method of the configuration boundary condition is as follows:
applying a self-weight stress load to the three-dimensional geomechanical model;
applying horizontally and uniformly distributed constructional loads on the side, with higher terrain, of the three-dimensional geomechanical model along the X-axis direction;
applying a horizontal triangular structure load on the side, with higher terrain, of the three-dimensional geomechanical model along the X-axis direction;
applying horizontally and uniformly distributed constructional loads on the side, with higher terrain, of the three-dimensional geomechanical model along the Y-axis direction;
applying a horizontal triangular structure load on the side, with higher terrain, of the three-dimensional geomechanical model along the Y-axis direction;
and setting a forced displacement on the three-dimensional geomechanical model for simulating a pure shear stress field.
Preferably, in step 5, F statistics is used to test the significance of the regression result of the multiple linear regression analysis, and t statistics is used to test the significance of the partial regression coefficient of the multiple linear regression analysis;
the expression for the F statistic is as follows:
where n is the degree of freedom of an explanatory variable, m is the degree of freedom of a response variable, S R Is the regression sum of squares of the regression results, S T Is the sum of the squares of the total deviations;
obtaining a critical value F of the F graduation according to a given checking level alpha α (n, n-m-1) if F>F α (n, n-m-1), the linear relation between the response variable and the explanation variable is obvious, otherwise, the response variable and the explanation variable are not linear;
the expression for the t statistic is as follows:
wherein, b ii Is a normal matrix X T The ith element on the diagonal of X is looked up according to a given checking level alpha to obtain a critical value t of t graduation α/2 (m-n-1) if T i >t α/2 (m-n-1), the explanatory variable is considered to have a significant effect on the response variable.
Preferably, in step 6, the long axial crustal stress value of the tunnel is substituted into a tunnel site area regression crustal stress equation to obtain a crustal stress characteristic of the tunnel site area, and the deformation grade of the soft rock of the tunnel is predicted based on a surrounding rock strength-stress ratio theory.
A system of a ground stress inversion analysis method for tunnel soft rock deformation grade evaluation comprises,
the data acquisition module is used for acquiring the mechanical parameters of surrounding rocks in a tunnel site area and an actually measured ground stress result;
the inversion range module of the ground stress field is used for determining the inversion range of the ground stress field of the tunnel site area;
the stress component module is used for carrying out coordinate axis conversion on the actual measurement ground stress result to obtain a stress component corresponding to the actual measurement ground stress result;
the three-dimensional geomechanical model module is used for establishing a three-dimensional geomechanical model according to the surrounding rock mechanical parameters and the inversion range of the ground stress field of the tunnel site area and applying a structural boundary condition to the three-dimensional geomechanical model;
the regression analysis module is used for carrying out numerical simulation calculation on the three-dimensional geomechanical model according to the stress component, extracting the ground stress result of the corresponding measuring point in the calculation result of the three-dimensional geomechanical model according to the measured point in the actual measurement, and carrying out multiple linear regression analysis on the extracted ground stress result pair to obtain a tunnel site area regression ground stress equation;
and the prediction module is used for substituting the long axial crustal stress value of the tunnel into a tunnel site region regression crustal stress equation to predict the deformation grade of the soft rock of the tunnel.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a ground stress inversion analysis method for tunnel soft rock deformation grade evaluation, which comprises the steps of obtaining physical and mechanical parameters of surrounding rocks of a tunnel site area and ground stress drilling data, and constructing a three-dimensional geomechanical model of the tunnel site area; carrying out coordinate axis transformation on the actually measured ground stress data; calculating an initial geostress field of an inversion tunnel site area based on multiple regression; checking the significance of the inversion result and the inversion coefficient; and calculating to obtain the crustal stress distribution at the axis of the tunnel, and evaluating the large deformation grade of the tunnel soft rock based on an intensity stress ratio method. The method has the advantages of simplicity, quickness and high prediction precision for the inversion of the ground stress level of the mountain tunnel and the evaluation of the extrusion surrounding rock deformation level, can greatly improve the prediction efficiency, is better applied to guiding and dynamically adjusting the construction process and the supporting time of the tunnel soft rock large deformation section, obviously improves the construction safety of the tunnel soft rock large deformation section, has simple process, and can make up the defect of low prediction precision of the tunnel soft rock large deformation level in the tunnel design stage.
Drawings
FIG. 1 is a flow chart of a geostress inversion analysis method for tunnel soft rock deformation level evaluation according to the invention;
FIG. 2 is a three-dimensional geomechanical model of a tunnel site area of a Shijiashan tunnel in an embodiment of the present invention;
FIG. 3 illustrates model boundary conditions in an embodiment of the present invention;
FIG. 4 is a comparison graph of the maximum principal stress calculation result and the actual measurement result in the embodiment of the present invention;
FIG. 5 is a comparison graph of a minimum principal stress calculation result and an actual measurement result in an embodiment of the present invention;
FIG. 6 is a graph comparing a vertical principal stress calculation result with an actual measurement result according to an embodiment of the present invention;
FIG. 7 is a graph showing the long axial stress distribution characteristics of a Shi-shan tunnel according to an embodiment of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.
As shown in fig. 1, a geostress inversion analysis method for tunnel soft rock deformation level evaluation includes the following steps:
step 1, acquiring surrounding rock mechanical parameters and an actually measured crustal stress result of a tunnel site area;
specifically, the ground stress result of the tunnel site area is measured by a ground stress measuring method, preferably a hydraulic fracturing method or a stress relieving method.
And collecting the surrounding rocks of the tunnel site area and obtaining mechanical parameters of the surrounding rocks, including elastic modulus (E), gravity (gamma) and Poisson ratio (mu), through indoor tests.
specifically, the inversion range of the ground stress field includes all the engineering areas, and is expanded to a certain extent, and the ridge line and the valley line are used as boundaries of the inversion range of the ground stress field, because such boundaries do not produce displacement perpendicular to the plane.
Step 3, carrying out coordinate axis conversion on the ground stress result actually measured in the step 1 to obtain a stress component corresponding to the ground stress result actually measured;
specifically, the coordinate axis transformation is performed on the actually measured stress result, the original coordinate system is marked as x, y, z, and the new coordinate system is marked as x ', y ', z ', and the direction cosine between the two coordinate systems is marked as a, b, c, and when the original coordinate system is transformed into the new coordinate system, the stress component can be calculated according to the following formula:
s41, importing the terrain data in the inversion range of the ground stress field into finite element software, and establishing 6 three-dimensional geomechanical models;
s42, each rock-soil body in the three-dimensional geomechanical model adopts an elastic constitutive relation, and the obtained elastic modulus, the gravity and the Poisson ratio are endowed to each rock-soil body during calculation;
s43, setting different structural boundary conditions for each three-dimensional geomechanical model according to the calculation conditions, and specifically comprising the following steps:
(1) Applying self-weight stress load to the three-dimensional geomechanical model,
except the top surface which is kept as a free surface, other surfaces apply displacement constraint;
(2) Applying horizontally and uniformly distributed construction loads on the higher side of the model terrain along the X-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface which is reserved as a free surface;
(3) Applying horizontal triangular structure load on the higher side of the model terrain along the X-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface reserved as a free surface;
(4) Applying horizontally and uniformly distributed construction loads on the higher side of the model terrain along the Y-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface which is reserved as a free surface;
(5) Applying horizontal triangular structure load on the higher side of the model terrain along the Y-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface reserved as a free surface;
(6) And (3) setting forced displacement on the three-dimensional geomechanical model to simulate a pure shear stress field.
And 5, performing numerical simulation calculation on each three-dimensional geomechanical model, extracting a stress result of a corresponding measuring point in the three-dimensional geomechanical model according to the measured measuring point position, and performing multiple linear regression analysis on the stress result to obtain a tunnel site region regression ground stress equation.
The multiple regression analysis method comprises the following steps:
wherein, c i Partial regression coefficients, σ, for response variables with respect to explanatory variables jk Measured stress result of j direction of k observation point, sigma i jk Is the calculated value of the stress component of the k observation points j under the working condition i.
The multiple regression calculation should also check the significance of the regression results and the partial regression coefficients. The significance of the regression results can be verified by the F statistic, and the partial regression coefficients of the response variables with respect to the explanatory variables need to be verified by the t statistic.
The calculation method of the F statistic is as follows:
observation sigma of investigating response variables jk Sum of squared deviations S of T Decomposing it can yield:
wherein S is R Is the regression sum of squares of the regression results, S c Is the sum of the squared errors of the regression results,
is the average of the observed samples. The F statistic and its distribution can thus be constructed as:
where n is the degree of freedom for the explanatory variable and m is the degree of freedom for the responsive variable. Whereby a table look-up yields the critical value F of the F division according to a given level of checking alpha α (n, n-m-1) if F>F α (n, n-m-1), considering that the linear relation between the response variable and the explanation variable is obvious, and otherwise, considering that the linear relation does not exist between the response variable and the explanation variable.
Similarly, a t test method in the multiple regression model is constructed, and the test statistic and the distribution thereof are constructed as follows:
wherein, b ii Is a normal matrix X T The ith element on the diagonal of the X,
whereby a table look-up yields a threshold value t for the t division based on a given level of detectability alpha α/2 (m-n-1) if T i >t α/2 (m-n-1), the explanatory variable is considered to have a significant effect on the response variable, whereas the coefficient is considered to have no statistical significance on the response variable.
And S6, substituting the long axial earth stress value of the tunnel into an earth stress regression equation of the tunnel site area to obtain earth stress characteristics of the tunnel site area, and performing predictive analysis and interpretation on the deformation grade of the soft rock of the tunnel based on the surrounding rock strength-stress ratio theory.
Predicting the soft rock deformation grade of the tunnel according to the strength-stress ratio G specified by the corresponding technical specification n And classifying the deformation of the tunnel extruding surrounding rock.
The invention also provides a system of the ground stress inversion analysis method for tunnel soft rock deformation grade evaluation, which comprises a data acquisition module, a ground stress field inversion range module, a stress component module, a three-dimensional geomechanical model module, a regression analysis module and a prediction module.
The data acquisition module is used for acquiring the mechanical parameters of surrounding rocks in a tunnel site area and an actually measured ground stress result;
the inversion range module of the ground stress field is used for determining the inversion range of the ground stress field of the tunnel site area;
the stress component module is used for carrying out coordinate axis conversion on the actual measurement ground stress result to obtain a stress component corresponding to the actual measurement ground stress result;
the three-dimensional geomechanical model module is used for establishing a three-dimensional geomechanical model and applying a structural boundary condition to the three-dimensional geomechanical model;
the regression analysis module is used for carrying out numerical simulation calculation on the three-dimensional geomechanical model according to the stress component, extracting the ground stress result of the corresponding measuring point in the calculation result of the three-dimensional geomechanical model according to the measuring point in practical measurement, and carrying out multiple linear regression analysis on the extracted ground stress result pair to obtain a tunnel site area ground stress regression equation;
and the prediction module is used for substituting the long axial crustal stress value of the tunnel into a crustal stress regression equation of the tunnel site area to predict the deformation grade of the soft rock of the tunnel.
Example 1
Referring to fig. 2-7, as shown in fig. 1, the present embodiment relates to a geostress inversion analysis method for tunnel soft rock deformation level evaluation, which includes the following steps:
s1, acquiring surrounding rock mechanical parameters and an actually measured crustal stress result of a tunnel site area;
in this embodiment, a tunnel site area of a shijiashan tunnel of a shaggan mountain rail transit project of the city of city, prefecture, and countryside is used as an explanatory object, a hydrofracturing method is used to obtain a ground stress value of a drilled hole DZ-sjsssd-02A, and an actual measurement result is shown in table 1:
TABLE 1
Wherein S is H Is the maximum horizontal principal stress, S h Is the minimum horizontal principal stress, S v Is the vertical principal stress
Indoor analysis is performed on the rock sample of the tunnel site area, and calculation parameters of rock and soil mass are obtained, as shown in table 2:
TABLE 2
S2, determining an inversion range of an initial ground stress field of a tunnel site area;
and determining the range of the inversion regression, including the whole engineering area, and expanding the range, wherein the calculation ranges of an X axis and a Y axis are 750m and 5000m, and the calculation range of a Z axis is 300m below the designed elevation of the tunnel axis to the natural earth surface.
S3, carrying out coordinate axis conversion on the actually measured ground stress result to obtain a corresponding stress component;
the measured ground stress result is converted into coordinate axis, and the existing ground stress result can be converted into S because the ground stress result measured by the hydraulic fracturing method of the Shijiashan tunnel has no shear stress in a vertical plane x ，S y ，S z ，S xy The stress values after conversion are shown in table 3:
TABLE 3
S4, establishing a three-dimensional geomechanical model, and applying a structural boundary condition to the model;
as shown in fig. 2, the topographic data of the inversion area is imported into finite element calculation software, a three-dimensional geomechanical model of the tunnel site area under 6 working conditions is established,
each rock-soil body adopts an elastic constitutive relation, and the obtained physical and mechanical parameters of the rock-soil body are endowed to each unit during calculation;
as shown in fig. 3, applying different structural boundary conditions to each model specifically includes:
(1) Applying a self-weight stress load to the model, and applying displacement constraint to other surfaces except the top surface which is reserved as a free surface;
(2) Applying a horizontally uniformly distributed construction load of 1MPa on the higher side of the model terrain along the X-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface which is reserved as a free surface;
(3) Applying a horizontal triangular structure load of 1kPa/m on the higher side of the model terrain along the X-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface which is reserved as a free surface;
(4) Applying a horizontally uniformly distributed construction load of 1MPa on the side with higher terrain of the model along the Y-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface which is reserved as a free surface;
(5) Applying a horizontal triangular structure load of 1kPa/m on the side with higher terrain of the model along the Y-axis direction, and applying displacement constraint on other unloaded surfaces except the top surface which is reserved as a free surface;
(6) A forced displacement of 1cm was set on the XOY plane to simulate a pure shear stress field.
S5, extracting stress results of each measuring point under each calculation working condition, and performing multiple linear regression analysis;
extracting the ground stress calculation results of each measuring point under each working condition, substituting the results into a formula to perform multiple linear regression calculation to obtain 1 free term and 6 partial regression coefficients, namely c 0 ＝-0.653,c 1 ＝5.131,c 2 ＝1.450,c 3 ＝1.956,c 4 ＝5.788,c 5 ＝1.203,c 6 =0.254. The ground stress regression equation for the tunnel site zone is thus:
wherein the content of the first and second substances,
the calculated stress for the tunnel region is,
and
respectively representing the calculated stresses caused by the horizontal construction loads in the X and Y directions,
and
respectively representing the calculated stresses caused by the X-direction and Y-direction triangular horizontal compressive loads,
representing the calculated stress caused by gravity,
representing the calculated stress caused by the construction shear load.
The results of the regression calculations and the partial regression coefficients were tested for significance, and the results are shown in table 4:
TABLE 4
Therefore, the inversion regression result is good, the significance is obvious, and a comparison graph of the inversion result and the actual measurement result is provided in figures 4-6.
Further, the calculation results of the long axial stress of the tunnel under each working condition are extracted and substituted into a regression equation to obtain the distribution characteristics and the distribution rules of the long axial stress of the tunnel in the Shijiashan mountain, as shown in FIG. 7.
And S6, substituting the obtained result into a tunnel site region regression ground stress equation to obtain the long axial ground stress level of the tunnel, and performing prediction analysis and interpretation on the deformation grade of the soft rock of the tunnel based on the surrounding rock strength-stress ratio theory.
And substituting the tunnel long axial ground stress result and the physical and mechanical parameters of the surrounding rocks into an intensity stress ratio calculation formula to obtain a corresponding intensity stress ratio Gn. The classification of the compressive surrounding rock deformation of the railway tunnel by the strength-stress ratio Gn specified in the technical specification of the compressive surrounding rock tunnel of the railway is shown in table 5:
TABLE 5
Therefore, the strength stress ratio and the surrounding rock deformation grading level of the tunnel surrounding rocks in different mileage sections of the Shijiashan tunnel can be obtained, and the following table shows that:
the method for inversion analysis of the ground stress of the tunnel soft rock deformation level provided by the invention is simple and quick for determining the ground stress of the mountain tunnel, has high prediction precision, improves the prediction efficiency and the feedback of a construction site, is better applied to guiding and dynamically adjusting the construction process and construction method conversion of the tunnel site soft rock large deformation section, and obviously improves the construction safety of the soft rock large deformation section.
The above contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention should not be limited thereby, and any modification made on the basis of the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. A geostress inversion analysis method for tunnel soft rock deformation grade evaluation is characterized by comprising the following steps:
step 1, acquiring surrounding rock mechanical parameters and an actually measured crustal stress result of a tunnel site area;
step 2, determining the inversion range of the ground stress field of the tunnel site area;
step 3, carrying out coordinate axis conversion on the ground stress result actually measured in the step 1 to obtain a stress component corresponding to the ground stress result actually measured;
step 4, establishing a three-dimensional geomechanical model according to the surrounding rock mechanical parameters of the tunnel site area and the inversion range of the ground stress field, and applying a construction boundary condition to the three-dimensional geomechanical model;
step 5, performing numerical simulation calculation on the three-dimensional geomechanical model according to the stress component, extracting a ground stress result of a corresponding measuring point in the calculation result of the three-dimensional geomechanical model according to the measured measuring point, and performing multiple linear regression analysis on the extracted ground stress result pair to obtain a tunnel site regression ground stress equation;
and 6, substituting the long axial crustal stress value of the tunnel into a crustal stress regression equation of the tunnel site area to obtain the crustal stress characteristic of the tunnel site area and predict the deformation grade of the soft rock of the tunnel.
2. The method for inversion analysis of geostress for tunnel soft rock deformation grade assessment as claimed in claim 1, wherein the surrounding rock mechanical parameters in step 1 include elastic modulus, gravity and poisson's ratio.
3. The inversion analysis method for geostress of soft rock deformation grade evaluation of tunnel according to claim 1, characterized in that in step 1, the geostress value of the tunnel site area is measured by using a hydraulic fracturing method or a stress relieving method.
4. The geostress inversion analysis method for tunnel soft rock deformation grade evaluation according to claim 1, wherein the geostress field inversion range in step 2 is the whole tunnel engineering area, the tunnel engineering area is expanded to a certain range to form a geostress field inversion range, and a ridge line and a valley line are used as boundaries of the geostress field inversion range.
5. The inversion analysis method for geostress of tunnel soft rock deformation grade evaluation according to claim 1, characterized in that the calculation method of the stress component is as follows:
wherein the original coordinate systems are marked as x, y and z, and the new coordinate systems are marked as x ', y ', z ', and the direction cosines between the two coordinate systems are marked as a, b and c.
6. The inversion analysis method for geostress of tunnel soft rock deformation grade evaluation according to claim 1, characterized in that the establishment method of the three-dimensional geomechanical model in step 4 is as follows:
s41, establishing a plurality of three-dimensional geomechanical models according to topographic data in the inversion range of the ground stress field;
s42, endowing the surrounding rock mechanical parameters to each rock-soil body in the three-dimensional geomechanical model by adopting an elastic constitutive relation;
and S43, setting different structural boundary conditions for each three-dimensional geomechanical model according to the calculation working conditions.
7. The earth stress inversion analysis method for tunnel soft rock deformation grade evaluation according to claim 6, characterized in that the setting method of the construction boundary conditions is as follows:
applying a self-weight stress load to the three-dimensional geomechanical model;
applying horizontally and uniformly distributed constructional loads on the side, with higher terrain, of the three-dimensional geomechanical model along the X-axis direction;
applying a horizontal triangular structure load on the side, with higher terrain, of the three-dimensional geomechanical model along the X-axis direction;
applying horizontally and uniformly distributed construction loads on the side, with higher terrain, of the three-dimensional geomechanical model along the Y-axis direction;
applying a horizontal triangular structure load on the side, with higher terrain, of the three-dimensional geomechanical model along the Y-axis direction;
and setting a forced displacement on the three-dimensional geomechanical model for simulating a pure shear stress field.
8. The inversion analysis method for the geostress of tunnel soft rock deformation grade evaluation according to claim 1, characterized in that in step 5, F statistic is adopted to test the significance of the regression result of the multiple linear regression analysis, and t statistic is adopted to test the significance of the partial regression coefficient of the multiple linear regression analysis;
the expression of the F statistic is as follows:
where n is the degree of freedom of an explanatory variable, m is the degree of freedom of a response variable, S R Is the regression sum of squares of the regression results, S T Is the sum of the squares of the total deviations;
obtaining a threshold value F of the F graduation according to a given checking level alpha α (n, n-m-1) if F>F α (n, n-m-1), the linear relation between the response variable and the explanation variable is obvious, otherwise, the response variable and the explanation variable are not linear;
the expression for the t statistic is as follows:
wherein, b ii Is a normal matrix X T The ith element on the X diagonal is looked up according to a given check level alpha to obtain a critical value t of t graduation α/2 (m-n-1) if T i >t α/2 (m-n-1), the explanatory variable is considered to have a significant effect on the response variable.
9. The geostress inversion analysis method for tunnel soft rock deformation grade evaluation according to claim 1, characterized in that in step 6, the tunnel long axial geostress value is substituted into a tunnel site region regression geostress equation to obtain the geostress characteristics of the tunnel site region, and the tunnel soft rock deformation grade is predicted based on the surrounding rock strength-stress ratio theory.
10. A system for executing the geostress inversion analysis method for tunnel soft rock deformation grade assessment according to any one of claims 1-9, comprising,
the data acquisition module is used for acquiring the mechanical parameters of surrounding rocks in a tunnel site area and an actually measured ground stress result;
the inversion range module of the ground stress field is used for determining the inversion range of the ground stress field of the tunnel site area;
the stress component module is used for carrying out coordinate axis conversion on the actual measurement ground stress result to obtain a stress component corresponding to the actual measurement ground stress result;
the three-dimensional geomechanical model module is used for establishing a three-dimensional geomechanical model according to the surrounding rock mechanical parameters of the tunnel site area and the inversion range of the ground stress field and applying a structural boundary condition to the three-dimensional geomechanical model;
the regression analysis module is used for carrying out numerical simulation calculation on the three-dimensional geomechanical model according to the stress component, extracting the ground stress result of the corresponding measuring point in the calculation result of the three-dimensional geomechanical model according to the measured point in the actual measurement, and carrying out multiple linear regression analysis on the extracted ground stress result pair to obtain a tunnel site area regression ground stress equation;
and the prediction module is used for substituting the long axial crustal stress value of the tunnel into a tunnel site area regression crustal stress equation to predict the deformation grade of the soft rock of the tunnel.
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| CN116306154A (en) * | 2023-03-28 | 2023-06-23 | 成都理工大学 | High-stress soft rock tunnel deformation prediction and classification method |
| CN117171841B (en) * | 2023-08-03 | 2024-04-05 | 中铁二院工程集团有限责任公司 | Method for determining large deformation grade of surrounding rock of excavation section in railway tunnel during construction period |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116306154A (en) * | 2023-03-28 | 2023-06-23 | 成都理工大学 | High-stress soft rock tunnel deformation prediction and classification method |
| CN117171841B (en) * | 2023-08-03 | 2024-04-05 | 中铁二院工程集团有限责任公司 | Method for determining large deformation grade of surrounding rock of excavation section in railway tunnel during construction period |
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