CN113971308B - Tunnel address area in-situ ground stress field inversion method characterized by composite regression model - Google Patents
Tunnel address area in-situ ground stress field inversion method characterized by composite regression model Download PDFInfo
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Abstract
The invention provides a tunnel address area in-situ ground stress field inversion method characterized by a composite regression model, which belongs to the technical field of tunnel engineering and comprises the following steps: obtaining rock parameters, a tunnel address area contour map and a tunnel longitudinal section map; obtaining a plurality of segment models or a plurality of virtual segment models of the tunnel address area three-dimensional numerical model; judging whether the model is a virtual segment model; the data of the inversion result of the drilling in the section of each virtual section model in the section are reserved and spliced, so that the first-class multi-inversion regression model is used for representing the in-situ stress field of the tunnel address area; and respectively inverting the in-situ stress field of the segmented model by using the respective measured values of the drilling holes of the segmented models, and splicing the inversion results of the segmented models to realize the representation of the in-situ stress field of the tunnel address region by the second-class multi-inversion regression model. The invention can avoid the error influence of the tunnel longitudinal dimension effect on the inversion of the ground stress field, and fully characterize the ground stress difference distribution characteristics of each local area in the tunnel longitudinal direction.
Description
Technical Field
The invention belongs to the technical field of tunnel engineering, and particularly relates to a tunnel address area in-situ stress field inversion method characterized by a composite regression model.
Background
The method is limited by high in-situ ground stress actual measurement drilling cost and high site requirement, and cannot perform large-scale initial ground stress field actual measurement work on underground engineering. Therefore, inversion of the initial ground stress field within the entire underground engineering range through limited borehole actual measurement data is a common means for investigating the ground stress field distribution law in the current engineering design stage. The basic principle of in-situ stress field inversion is briefly that the stress result obtained by applying various dead weights or structural boundary conditions to a three-dimensional numerical model approximates the actual ground stress. The in-situ ground stress result of the underground engineering area obtained through ground stress field inversion can be applied to a plurality of aspects such as supporting structure safety checking calculation, rock burst prediction, large deformation prediction and the like. Therefore, reducing the residual error between the inversion result and the measured value has great significance for optimizing the engineering application of the ground stress field inversion.
At present, the in-situ ground stress field inversion is widely applied to tunnel engineering, hydraulic and hydroelectric engineering and coal mine engineering. In the water conservancy and hydropower engineering and the coal mine engineering, the sizes of the three-dimensional numerical models established based on the site ranges are relatively coordinated, so that it is reasonable to solve the in-situ stress field of the whole site model by using an inversion regression model. The tunnel engineering is greatly different from the water conservancy and hydropower engineering and the coal mine engineering, the longitudinal dimension of the tunnel engineering is far greater than that of other directions, and the actually measured ground stress distribution characteristics of a limited number of ground stress drilling holes longitudinally distributed along the tunnel are greatly different. However, the ground stress field inversion is applied to tunnel engineering, the influence of the size effect on inversion errors is not considered independently, and an inversion regression model is still adopted to solve the in-situ ground stress field of the whole tunnel address area.
The main problems of the existing tunnel address area ground stress field inversion method are as follows: (1) The influence of the tunnel engineering longitudinal size effect on the inversion error of the in-situ ground stress field cannot be considered differently; (2) The drilling holes of the long, large and deep buried tunnels are often separated by a few kilometers, the difference of the ground stress distribution characteristics of the drilling holes is large, and the method for solving an inversion regression model by using measured data of all the drilling holes at different positions can only obtain a local inversion optimal solution; (3) The inversion result of the tunnel portal segment is rejected, affected by the numerical model boundary effect.
Disclosure of Invention
Aiming at the defects in the prior art, the in-situ stress field inversion method for the tunnel address region represented by the composite regression model improves the in-situ stress inversion precision and solves the problems of error influence of tunnel longitudinal dimension effect on inversion of the ground stress field and insufficient ground stress difference distribution characteristic representation of each local area in the tunnel longitudinal direction.
In order to achieve the above purpose, the invention adopts the following technical scheme:
The scheme provides a tunnel address area in-situ stress field inversion method characterized by a composite regression model, which comprises the following steps:
S1, uniformly distributing drill holes at different elevations of a tunnel along the longitudinal direction, and measuring the ground stress of tunnel engineering to obtain rock parameters, a tunnel address area contour map and a tunnel longitudinal section map;
S2, establishing a tunnel address area three-dimensional numerical model by using the obtained rock parameters, the tunnel address area contour map and the tunnel longitudinal section map, and carrying out segmentation processing on the tunnel address area three-dimensional numerical model to obtain a plurality of segmentation models or a plurality of virtual segmentation models of the tunnel address area three-dimensional numerical model;
S3, judging whether the model is a virtual segmentation model, if so, entering a step S4, otherwise, entering a step S5;
S4, only retaining the data in the section according to the inversion result of the drilling in the section of each virtual section model, and splicing the data to realize that the first-class multi-inversion regression model represents the in-situ stress field of the tunnel address region;
S5, respectively inverting the in-situ stress field of the segmented model by using the respective measured values of the drilling holes of the segmented models, and splicing inversion results of the segmented models to realize that the second-class multi-inversion regression model characterizes the in-situ stress field of the tunnel address region.
The invention has the beneficial effects that:
According to the invention, the tunnel is divided into a series of small models with more coordinated three-dimensional sizes by avoiding the error influence of the longitudinal size effect of the tunnel on the inversion of the ground stress field, so that the error caused by numerical calculation is reduced; according to the method, the ground stress distribution difference characteristics of different areas of the tunnel are fully considered, the ground stress field distribution of the tunnel address area is represented by a plurality of regression models, each regression model only represents the ground stress distribution characteristics of a respective local area, and the error influence of the ground stress distribution differences of different areas on inversion results is avoided; according to the invention, each inversion regression model can obtain an optimal solution, and the situation that a single regression model obtains a local optimal solution at an individual drilling position does not exist; the invention has strong operability, and the prior art can increase a plurality of groups of calculation working conditions according to the principle of the invention to obtain the inversion result with higher precision than the original inversion method.
Further, the width dimension and the height dimension of the tunnel address area three-dimensional numerical model established in the step S2 are consistent.
The beneficial effects of the above-mentioned further scheme are: the width size and the height size of the tunnel address area three-dimensional numerical model established by the invention are consistent, and errors caused by the boundary effect of the model can be eliminated.
Further, in the step S2, the segmentation processing is performed on the three-dimensional numerical model of the tunnel address area, which includes the following steps:
s21, according to a ground stress field inversion method, respectively and independently inverting the ground stress field corresponding to the three-dimensional numerical model of the whole tunnel address area by utilizing the measured stress of each drilling hole;
S22, obtaining the segmented positions of two adjacent holes based on the inversion error of the inversion result of the hole A at the position of the hole B and the inversion error of the inversion result of the hole B at the position of the hole A in each two adjacent holes A and B;
s23, judging whether to cut the three-dimensional numerical model of the tunnel address area, if so, entering a step S24, otherwise, entering a step S25;
S24, carrying out sectional cutting on the three-dimensional numerical model of the tunnel address area according to the sectional positions of two adjacent drilling holes to obtain sectional models, and carrying out grid encryption on each sectional model according to inversion requirements;
s25, virtually segmenting the tunnel address area three-dimensional numerical model according to segmentation positions of two adjacent drilling holes to obtain a virtual segmentation model.
The beneficial effects of the above-mentioned further scheme are: according to the invention, the tunnel is divided into a series of small models with more coordinated three-dimensional sizes by avoiding the error influence of the longitudinal size effect of the tunnel on the inversion of the ground stress field, so that the error caused by numerical calculation is reduced.
Further, in the step S21, the regression model expression of the ground stress field corresponding to the whole tunnel address region model is independently inverted by using the measured data of the drill hole as follows:
Wherein, Representing the j-th measured stress component of the kth borehole, a 0 representing a constant, a i representing the i-th regression coefficient,Representing the numerical simulation calculation of the kth borehole, e jk representing the random error of the kth borehole, n representing the total number of regression coefficients.
Further, the expression for determining the segment positions of two adjacent boreholes a and B in the step S22 is as follows:
Wherein L A represents the distance between the segment position along the tunnel longitudinal direction and the a borehole, δ B-A represents the relative error of inverting the whole tunnel address region model at the a borehole with the B borehole actual measurement data, δ A-B represents the relative error of inverting the whole tunnel address region model at the B borehole with the a borehole actual measurement data, and L represents the distance along the tunnel longitudinal direction between the a and B boreholes.
The beneficial effects of the above-mentioned further scheme are: the effective range of the inversion accuracy of each borehole can be determined according to the relative error between the inversion result of each borehole at the adjacent borehole and the actual measurement value of the adjacent borehole, and the segmentation position can be quantitatively determined, in other words, the higher the inversion accuracy of which borehole in the adjacent boreholes is, the farther the inversion range of the effective accuracy is, and the farther the segmentation position is from the borehole position.
Further, in the step S5, when the in-situ stress field segment inversion is performed on each segment model by using the respective measured values of the holes of each segment model, if m holes are counted, the inversion regression model expression of the segment to which the hole belongs is solved by using each measured value of the holes as follows:
wherein m represents the mth borehole, Representing the j-th measured stress component of the mth borehole, a 0 representing a constant, a i representing the i-th regression coefficient,Representing the numerical simulation calculation of the mth borehole, e jm representing the random error of the mth borehole, and n representing the total number of regression coefficients.
The beneficial effects of the above-mentioned further scheme are: and each drilling hole establishes a regression model in the drilling hole section, so that the interference of each drilling hole on the unified regression model is avoided, and the regression models of each drilling hole are independent and cannot influence each other.
The working principle of the invention is as follows:
Uniformly distributing the drill holes on different high layers of the tunnel along the longitudinal direction, and measuring the ground stress of the tunnel engineering to obtain rock parameters, a contour map of a tunnel address area and a longitudinal section map of the tunnel, so that the actually measured stress of each drill hole fully reflects the ground stress distribution characteristics of each local area; establishing a tunnel address area three-dimensional numerical model by using the measured rock mass parameters, the tunnel address area contour map and the tunnel longitudinal section map, wherein the width dimension and the height dimension of the three-dimensional numerical model are consistent, and errors caused by model boundary effects are eliminated; according to various existing ground stress inversion methods, on the premise of not cutting the three-dimensional numerical model of the tunnel address area, the ground stress fields corresponding to the three-dimensional numerical model of the whole tunnel address area are respectively and independently inverted by utilizing measured stress of each drilling hole; determining the effective range of inversion precision of each drilling hole according to the relative error of the inversion result of each drilling hole at the adjacent drilling hole and the measured value of the adjacent drilling hole, and determining the segmentation position; obtaining virtual segment models according to the segment positions of the obtained two adjacent drilling holes, carrying out segment cutting on the three-dimensional numerical model of the tunneling address area to obtain segment models, and carrying out grid encryption on each segment model according to inversion requirements; the inversion result of the drilling in each virtual segment model segment only reserves the data in the segment, and the data are spliced to realize that the first-class multi-inversion regression model represents the in-situ stress field of the tunnel address region; according to various ground stress inversion methods, the in-situ ground stress field of the segmented model is inverted again by utilizing respective drilling actual measurement values of the segmented models, inversion results of the segmented models are spliced, and the in-situ ground stress field of the tunnel address region is represented by the second-class multi-inversion regression model.
Drawings
FIG. 1 is a flow chart of the steps of a method for inverting the in-situ stress field of a tunnel address region represented by a multiple regression model in an embodiment of the present invention.
Fig. 2 is a flow chart of a method for processing a three-dimensional numerical model of a tunnel address region in situ stress field inversion method in step S2 of a tunnel address region represented by a multiple regression model according to an embodiment of the present invention.
FIG. 3 is a three-dimensional numerical model of the tunnel address region according to an embodiment of the present invention.
Fig. 4 is a three-dimensional numerical model diagram of tunneling address segmentation in an embodiment of the present invention.
FIG. 5 is a graph showing the comparison of the measured value of σ x with the inversion value of σ x in an embodiment of the invention.
FIG. 6 is a graph showing the comparison of the measured value of σ y with the inversion value of σ y in an embodiment of the invention.
FIG. 7 is a graph showing the comparison of the measured value of σ z with the inversion value of σ z in an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and all the inventions which make use of the inventive concept are protected by the spirit and scope of the present invention as defined and defined in the appended claims to those skilled in the art.
Example 1
The invention provides a tunnel address area in-situ stress field inversion method characterized by a multiple regression model as shown in fig. 1, which comprises the following steps:
S1, uniformly distributing drill holes at different elevations of a tunnel along the longitudinal direction, and measuring the ground stress of tunnel engineering to obtain rock parameters, a tunnel address area contour map and a tunnel longitudinal section map;
S2, establishing a tunnel address area three-dimensional numerical model by using the obtained rock parameters, the tunnel address area contour map and the tunnel longitudinal section map, and carrying out segmentation processing on the tunnel address area three-dimensional numerical model to obtain a plurality of segmentation models or a plurality of virtual segmentation models of the tunnel address area three-dimensional numerical model;
S3, judging whether the model is a virtual segmentation model, if so, entering a step S4, otherwise, entering a step S5;
S4, only retaining the data in the section according to the inversion result of the drilling in the section of each virtual section model, and splicing the data to realize that the first-class multi-inversion regression model represents the in-situ stress field of the tunnel address region;
S5, respectively inverting the in-situ stress field of the segmented model by using the respective measured values of the drilling holes of the segmented models, and splicing inversion results of the segmented models to realize that the second-class multi-inversion regression model characterizes the in-situ stress field of the tunnel address region.
And the width dimension and the height dimension of the tunnel address area three-dimensional numerical model established in the step S2 are consistent.
As shown in fig. 2, in the step S2, the segmentation processing is performed on the three-dimensional numerical model of the tunnel address area, which includes the following steps:
s21, according to a ground stress field inversion method, respectively and independently inverting the ground stress field corresponding to the three-dimensional numerical model of the whole tunnel address area by utilizing the measured stress of each drilling hole;
S22, obtaining the segmented positions of two adjacent holes based on the inversion error of the inversion result of the hole A at the position of the hole B and the inversion error of the inversion result of the hole B at the position of the hole A in each two adjacent holes A and B;
s23, judging whether to cut the three-dimensional numerical model of the tunnel address area, if so, entering a step S24, otherwise, entering a step S25;
S24, carrying out sectional cutting on the three-dimensional numerical model of the tunnel address area according to the sectional positions of two adjacent drilling holes to obtain sectional models, and carrying out grid encryption on each sectional model according to inversion requirements;
s25, virtually segmenting the tunnel address area three-dimensional numerical model according to segmentation positions of two adjacent drilling holes to obtain a virtual segmentation model.
In the step S21, the regression model expression of the ground stress field corresponding to the whole tunnel address region model is independently inverted by using the measured data of the drill hole as follows:
Wherein, Representing the j-th measured stress component of the kth borehole, a 0 representing a constant, a i representing the i-th regression coefficient,Representing the numerical simulation calculation of the kth borehole, e jk representing the random error of the kth borehole, n representing the total number of regression coefficients.
Solving regression coefficients of a ground stress field regression model by utilizing a multiple regression method and a least square estimation method, and calculating an expression for enabling the residual square sum of the least square method to be minimum as follows:
Wherein the method comprises the steps of The j-th measured value of the stress component representing the kth borehole, m representing the total number of boreholes, s representing the total number of stress components, a 0 representing a constant, a i representing the i-th regression coefficient, n representing the total number of regression coefficients,Representing the numerical simulation calculation of the kth borehole, e jk representing the random error of the kth borehole, Q being the sum of squares of the residuals.
The expression for determining the segment positions of two adjacent boreholes a and B in step S22 is as follows:
Wherein L A represents the distance between the segment position along the tunnel longitudinal direction and the a borehole, δ B-A represents the relative error of inverting the whole tunnel address region model at the a borehole with the B borehole actual measurement data, δ A-B represents the relative error of inverting the whole tunnel address region model at the B borehole with the a borehole actual measurement data, and L represents the distance along the tunnel longitudinal direction between the a and B boreholes.
In the step S3, when the in-situ stress field segment inversion is performed on each segment model by using the respective measured values of the holes of each segment model, if m holes are total, the inversion regression model expression of the segment of the hole is solved by using the measured data of each hole as follows:
wherein m represents the mth borehole, Representing the j-th measured stress component of the mth borehole, a 0 representing a constant, a i representing the i-th regression coefficient,Representing the numerical simulation calculation of the mth borehole, e jm represents the random error of the mth borehole.
The method of combining the multiple regression method with the least square estimation is utilized, so that the residual square sum of the inversion regression model corresponding to each drilling hole can take the minimum value:
Qmin＝(Q1)min+(Q2)min+(Q3)min+…+(Qm)min
Where Q min represents the total sum of squares of residuals minimum, (Q m)min represents the sum of squares of residuals minimum for the inverted regression model corresponding to the mth borehole, for a total of m boreholes.
In one practical example of the invention:
taking a tunnel engineering as an example, the improvement effect of the method on inversion errors is discussed. The total hydraulic fracturing method ground stress measurement drilling holes (drilling holes 1 and drilling holes 2) of the tunnel engineering tunnel address area are respectively arranged on the left side and the right side of the tunnel, and the distance between the two drilling holes is 4.3Km. Wherein the depth of the final hole of the drilling hole 1 is 427m, and the total number of the measuring points is 5; the final hole depth of the drilling hole 2 is 370m, and the total number of the measuring points is 3.
The two-hole measured ground stress results are shown in table 1:
TABLE 1
As shown in fig. 3, the data such as rock mass parameters, tunnel address area contour map, tunnel longitudinal section map, etc. are collected based on the information such as the tunnel address area survey data and design file. Based on these data, a three-dimensional numerical model of the tunneling site area is built in ANSYS numerical simulation software. Meanwhile, in order to eliminate errors caused by model boundary effects, the three-dimensional numerical model has a width of about 1500m, a height of about 1400m and a length of about 16000m according to the principle that the width dimension is at least coordinated with the height dimension.
Rock mass parameter information collected according to the information such as the tunnel engineering address area geological survey data, the design file and the like is shown in table 2:
TABLE 2
And independently inverting the ground stress field corresponding to the three-dimensional tunnel address area model of the whole tunnel address area by using the measured stress of the drilling holes 1 and 2 on the premise of not cutting the three-dimensional numerical model of the tunnel address area by using a multiple regression method.
Solving regression coefficients by adopting a least square estimation method, and inverting the actual measurement stress of the drilling holes 1 and 2 to obtain the whole tunnel address area ground stress field regression model expression as follows:
Wherein, The ground stress field result of the whole tunnel address area obtained by inversion of the actual measurement stress of the drilling hole 1 is shown,The ground stress field result of the whole tunnel address area obtained by inversion of the actual measurement stress of the drilling hole 2 is shown,The result obtained by applying dead weight to the three-dimensional model of the tunnel address area is shown,The results obtained after applying the unit structural stress in the X direction to the three-dimensional model of the tunnel address region are shown,The results obtained after applying the unit structural stress in the Y direction to the three-dimensional model of the tunnel address region are shown,And (3) representing the result obtained after the equivalent boundary displacement is applied to the tunnel address region three-dimensional model XOY plane.
Inquiring the ground stress inversion value of the position of the drill hole 2 based on the inversion result of the drill hole 1, and comparing the ground stress inversion value with the actual measurement value of the corresponding position of the drill hole 2 to obtain the inversion error of the drill hole 1; similarly, the inversion error of the borehole 2 is obtained by inquiring the inversion value of the ground stress at the position of the borehole 1 based on the inversion result of the borehole 2 and comparing the inversion value with the actual measurement value of the corresponding position of the borehole 1.
Specific inversion results for borehole 1 and borehole 2 are shown in table 3:
TABLE 3 Table 3
The inversion relative error values for each well are counted as shown in table 4:
TABLE 4 Table 4
| Inversion type | Relative error at borehole 1 | Relative error at borehole 2 |
| Inversion based on measured data of borehole 2 | 26.7％ | / |
| Inversion based on measured data of borehole 1 | / | 26.0％ |
Based on the relative error values of the holes in table 4, the expression of the segment positions between the holes 1 and 2 is found using the expression of determining the segment positions of two adjacent holes as follows:
Where L Drilling holes 1 denotes the distance of the segment location from the borehole 1.
If the virtual segmentation is judged to be selected, only the inversion result on the left side of the segmentation position of the ground stress field of the whole tunnel address area inverted by using the measured data of the drilling hole 1 is reserved; for the ground stress field of the whole tunnel address area inverted by using the measured data of the drill hole 2, only the inversion result on the right side of the segmentation position is reserved. Therefore, the in-situ stress field of the tunnel address region can be represented by the first multi-inversion regression model on the premise of not cutting the numerical model. The inversion values for each well are shown in table 5:
TABLE 5
As shown in fig. 4, if the actual segmentation model is selected, the segmentation model is obtained by segmenting the three-dimensional numerical model of the tunneling address area according to the obtained segmentation positions of two adjacent drilling holes, and each segmentation model is processed according to the inversion precision requirement grid, and after the model is segmented, two three-dimensional numerical models are respectively obtained.
Taking a multiple regression method as an example, the ground stress field of the left three-dimensional numerical model in fig. 3 is inverted by using the measured data of the borehole 1, and the ground stress field of the right three-dimensional numerical model in fig. 3 is inverted by using the measured data of the borehole 2.
Solving an inversion regression model of each segment based on measured data of each borehole, and inverting a regression equation expression of the three-dimensional numerical model on the left side in FIG. 3 by using the borehole 1 as follows:
Wherein, Representing the results of inverting the three-dimensional numerical model on the left in figure 3 by borehole 1,The result obtained by applying dead weight to the three-dimensional model of the tunnel address area is shown,The results obtained after applying the unit structural stress in the X direction to the three-dimensional model of the tunnel address region are shown,The results obtained after applying the unit structural stress in the Y direction to the three-dimensional model of the tunnel address region are shown,And (3) representing the result obtained after the equivalent boundary displacement is applied to the tunnel address region three-dimensional model XOY plane.
Solving an inversion regression model of each segment based on measured data of each borehole, and inverting a regression equation expression of the three-dimensional numerical model on the right side in FIG. 3 by using the borehole 2 as follows:
Wherein, Representing the results of borehole 1 inverting the three-dimensional numerical model on the right in figure 3,The result obtained by applying dead weight to the three-dimensional model of the tunnel address area is shown,The results obtained after applying the unit structural stress in the X direction to the three-dimensional model of the tunnel address region are shown,The results obtained after applying the unit structural stress in the Y direction to the three-dimensional model of the tunnel address region are shown,And (3) representing the result obtained after the equivalent boundary displacement is applied to the tunnel address region three-dimensional model XOY plane.
Therefore, the in-situ stress field of the tunnel address region is represented by the multi-inversion regression model of the second type, and the inversion result data at the drilling position are shown in table 6:
TABLE 6
In this example, the inversion errors of the in-situ stress field of the tunnel address region represented by the first-type multi-inversion regression model and the in-situ stress field of the tunnel address region represented by the second-type multi-inversion regression model are shown in table 7:
TABLE 7
| Inversion model | Average error of all measuring points |
| Multiple inversion regression model of the second class | 6.9％ |
| Multiple inversion regression model of the second class | 6.0％ |
Therefore, the inversion accuracy of the in-situ stress field of the second-type multi-inversion regression model representation tunnel address area is higher than that of the first-type multi-inversion regression model representation tunnel address area.
In order to compare the inversion method provided by the invention with the improvement effect of inversion errors by the traditional method, according to the traditional method, the actual measurement data of the drill holes 1 and 2 are simultaneously brought into the regression model of the ground stress field corresponding to the whole tunnel address region model to be independently inverted by the actual measurement data of the drill holes to obtain a regression model, and the expression is as follows:
Wherein, Representing the results of the measured data of borehole 1 and borehole 2 using conventional methods to individually invert the ground stress field corresponding to the entire tunnel address region model,The result obtained by applying dead weight to the three-dimensional model of the tunnel address area is shown,The results obtained after applying the unit structural stress in the X direction to the three-dimensional model of the tunnel address region are shown,The results obtained after applying the unit structural stress in the Y direction to the three-dimensional model of the tunnel address region are shown,And (3) representing the result obtained after the equivalent boundary displacement is applied to the tunnel address region three-dimensional model XOY plane.
The data of the inversion result of the conventional single regression model at the drilling position are shown in table 8:
TABLE 8
As shown in fig. 5, fig. 6 and fig. 7, the inversion stress and the measured stress of the second-type multiple inversion regression model provided by the invention and the conventional single regression model are compared, that is, the content of table 6 is compared with the content of table 8, and the average relative error statistical results of the two methods at all measuring points are shown in table 9:
TABLE 9
As can be seen from comparison of average relative error statistics results at all measuring points, the inversion error can be reduced from 12.7% to 6.0% by adopting the inversion method for the in-situ stress field of the tunnel address region represented by the multiple regression model.
Claims (5)
1. The in-situ stress field inversion method for the tunnel address region characterized by the composite regression model is characterized by comprising the following steps of:
S1, uniformly distributing drill holes at different elevations of a tunnel along the longitudinal direction, and measuring the ground stress of tunnel engineering to obtain rock parameters, a tunnel address area contour map and a tunnel longitudinal section map;
S2, establishing a tunnel address area three-dimensional numerical model by using the obtained rock parameters, the tunnel address area contour map and the tunnel longitudinal section map, and carrying out segmentation processing on the tunnel address area three-dimensional numerical model to obtain a plurality of segmentation models or a plurality of virtual segmentation models of the tunnel address area three-dimensional numerical model;
S3, judging whether the model is a virtual segmentation model, if so, entering a step S4, otherwise, entering a step S5;
S4, only retaining the data in the section according to the inversion result of the drilling in the section of each virtual section model, and splicing the data to realize that the first-class multi-inversion regression model represents the in-situ stress field of the tunnel address region;
s5, respectively inverting the in-situ stress field of the segmented model by using the respective measured values of the drilling holes of the segmented models, and splicing inversion results of the segmented models to realize that a second-class multi-inversion regression model represents the in-situ stress field of the tunnel address region;
In the step S2, the segment processing is performed on the three-dimensional numerical model of the tunnel address area, which includes the following steps:
s21, according to a ground stress field inversion method, respectively and independently inverting the ground stress field corresponding to the three-dimensional numerical model of the whole tunnel address area by utilizing the measured stress of each drilling hole;
s22, obtaining the segmented positions of two adjacent holes based on the inversion error of the inversion result of the hole A at the position of the hole B and the inversion error of the inversion result of the hole B at the position of the hole A in each two adjacent holes A and B;
in step S21, the regression model expression of the ground stress field corresponding to the whole tunnel address region model is independently inverted by using the measured data of the drill hole as follows:
Wherein, Represent the firstFirst of the drill holesThe actual measurement value of each stress component,A constant is represented by a number of times,Represent the firstThe number of regression coefficients is chosen such that,Represent the firstThe numerical simulation of the individual boreholes calculates the values,Represent the firstRandom errors of individual boreholes, n representing the total number of regression coefficients.
2. The method for inversion of in-situ stress field of tunnel address region represented by multiple regression model according to claim 1, wherein the width dimension and the height dimension of the three-dimensional numerical model of tunnel address region established in step S2 are identical.
3. The method for inverting the in-situ stress field of the tunnel address region represented by the multiple regression model according to claim 1, wherein the step S2 of segmenting the three-dimensional numerical model of the tunnel address region further comprises:
S23, judging whether the tunnel address area three-dimensional numerical model is actually cut, if so, entering a step S24, otherwise, entering a step S25;
S24, carrying out sectional cutting on the three-dimensional numerical model of the tunnel address area according to the sectional positions of two adjacent drilling holes to obtain sectional models, and carrying out grid encryption on each sectional model according to inversion requirements;
s25, virtually segmenting the tunnel address area three-dimensional numerical model according to segmentation positions of two adjacent drilling holes to obtain a virtual segmentation model.
4. The method for inversion of the in-situ stress field of the tunnel address region characterized by the multiple regression model according to claim 1, wherein the expression for determining the segment positions of the two adjacent boreholes a and B in step S22 is as follows:
Wherein, Indicating the distance of the segment location from the a borehole along the tunnel longitudinal direction,Representing the relative error of the whole tunnel address region model at the drilling A by using the measured data of the drilling B,Representing the relative error of the whole tunnel address region model at the drilling position B by using the measured data of the drilling hole A,Representing the distance between the a and B boreholes along the longitudinal direction of the tunnel.
5. The method for inverting the in-situ stress field of the tunnel address region represented by the multiple regression model according to claim 1, wherein when the in-situ stress field of the segmented model is respectively and sectionally inverted by using the respective measured values of the boreholes of the segmented models in step S5, if m boreholes are totally formed in the segmented model, the inversion regression model expression of the segmented model to which the boreholes belong is solved by using the measured values of each borehole as follows:
Wherein, Represent the firstA plurality of the holes are drilled,Represent the firstFirst of the drill holesThe actual measurement value of each stress component,A constant is represented by a number of times,Represent the firstThe number of regression coefficients is chosen such that,Represent the firstThe numerical simulation of the individual boreholes calculates the values,Represent the firstRandom errors of individual boreholes, n representing the total number of regression coefficients.
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