CN114417488A - Railway deep-buried soft rock large-deformation tunnel ground stress field inversion method - Google Patents
Railway deep-buried soft rock large-deformation tunnel ground stress field inversion method Download PDFInfo
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Abstract
The invention relates to the technical field of tunnel construction, in particular to a method for inverting a ground stress field of a railway deep-buried soft rock large-deformation tunnel. The inversion method provided by the invention comprises the following steps: the method comprises the following steps: distributing a plurality of surrounding rock stress monitoring points; step two: monitoring the surrounding rock stress value of each surrounding rock stress monitoring point; step three: analyzing the change of the surrounding rock pressure of each surrounding rock stress monitoring point; step four: establishing a ground stress function expression according to the stress values of the three surrounding rock stress monitoring points and the coordinates of the surrounding rock stress monitoring points; step five: the surrounding rock pressure value of each surrounding rock stress monitoring point is brought into a ground stress function, and surrounding rock stress of each surrounding rock stress monitoring point is calculated; step six: and comparing the calculated value and the measured value of the ground stress function of each surrounding rock stress monitoring point, wherein the calculated value and the measured value of the ground stress function are highly similar. The method has the advantages of simple and clear ground stress function form, small calculation amount and higher precision in a local area.
Description
Technical Field
The invention relates to the technical field of tunnel construction, in particular to a method for inverting a ground stress field of a railway deep-buried soft rock large-deformation tunnel.
Background
The earth stress is constantly changing as the earth develops movement. It is determined by the stress generated by the structure movement, the loading and unloading caused by the lifting movement of the earth crust, the temperature difference stress of the magma movement, the change of the physical and mechanical properties of the rock mass, etc. However, in the current state of the art, it is difficult to calculate the value of the earth stress field according to the evolution of the earth. In the 70 s, scholars at home and abroad establish calculation methods such as an elasticity calculation method, an elastoplasticity calculation method, a viscoelasticity calculation method and the like of an underground cavern on the basis of a large amount of researches, wherein the calculation methods comprise a finite element method, a boundary element method and the like, and are calculation methods of a series of plane problems and space problems, and program software can be used for stress analysis of a stratum around a cave and can also consider the effects of a lining structure and anchor and shotcrete support. These methods allow numerical calculations of subsurface structures to be developed into more complete calculation theories.
Such calculation methods are collectively referred to as stratigraphic structure methods. Although the calculation theory of the stratum structure method is more perfect, a plurality of problems still exist in the application. The most important of the methods is that the distribution rule and the magnitude of the initial ground stress input as a known quantity are often unclear, the dereferencing degrees of stratum parameters such as elastic modulus, Poisson's ratio and the like have arbitrariness to different zones, the rules of stress relaxation and creep after engineering construction can only be simulated by adopting an ideal model according to engineering conditions, and the conditions of damage after the stratum is stressed and deformed lack of judgment criteria meeting the reality. As a result, the results obtained by the calculation analysis often deviate largely from the actual results.
Aiming at the situation, an inversion calculation method capable of obtaining various unknown parameters according to field actual measurement information obtained in engineering is generated. The inversion calculation method can be combined with the stratum structure method, the result obtained by the inversion calculation is provided for the stratum structure method as necessary calculation parameters, the calculation precision of various numerical calculation methods can be improved, and the excavation of the stratum and the design and construction of support are guided. A discussion will be made herein of the inversion of the initial ground stress.
In the engineering, the initial ground stress value for application mainly depends on actual measurement data, a few measuring points cannot meet the engineering requirement easily, and meanwhile, the initial stress field required in the engineering can be regarded as a relatively stable stress field with neglected time factors (geological age). Therefore, the inversion is carried out by using the stress values of a few measuring points, a relatively accurate initial stress field is provided, and the method is an effective method for solving the engineering stability problem.
At present, the inversion method of the ground stress field mainly comprises a displacement inverse analysis method and a stress inverse analysis method. Due to the formation of the new Olympic tunnel construction technology, the measurement information of the convergence displacement of the hole periphery enters the visual field of scientific research personnel, and the measurement information obtained by tunnel construction can also be used for inversion research of the ground stress while the research on the design theory of the convergence limiting method is carried out. However, the inverse calculation equation of the method assumes that the surrounding rock is an isotropic medium with elasticity and homogeneity, but the actual situation is not the case; various parameters in the material constitutive equation are also determined by indoor experiments, and the correctness of the inversion calculation result is also influenced by the fact that the field environment is different from the laboratory condition. Therefore, the displacement inversion analysis method is only suitable for the working conditions of simple landform and single stratum distribution. Early studies of stress inversion analysis methods mostly belong to the category of qualitative analysis, for example, the initial ground stress field is divided into a self-gravity stress field, a structural stress field, a temperature stress field, a geomagnetic stress field, and the like. In most of the works, the dead weight and the tectonic stress field are the main components of the stress field of the rock mass, and in the deep rock mass, the distribution of the stress field is also affected by the temperature and the like. By analyzing the characteristics and the influence factors of the two methods, a boundary load adjustment method, a side pressure coefficient method and the like are generated. In recent years, with the progress of computer technology and numerical analysis methods, this problem has been achieved in research of quantitative analysis. The currently used analytical methods are: a stress function method, a multiple linear regression analysis method, a least square method, a quasi-linear gradient search solution, a global intelligent search optimal solution and the like. Most of these methods are based on measured stress values at certain positions for fitting analysis, and belong to a point selection method in mathematical concepts. However, this kind of method can only target the initial ground stress field in a local area, because the distribution of the initial stress field is complicated, and the accumulated experience is not enough to perform a large-scale analysis and calculation.
By comparing and researching the methods and combining engineering practice, the stress function method has the advantages of accurate local range of obtained results and small calculated amount, and is widely applied to engineering practice. In the finite element method, the shape function in a weighting form can approximately calculate the stress at any point in a plane according to the measured stress values of different positions of the same section, can meet the actual engineering conditions while reducing the calculated amount, is suitable for calculating the plane internal stress, and carries out the inversion of the ground stress in the local area of the section of the tunnel by adopting the method provided by the text and combining the geological structure conditions of the engineering area according to the actual measurement result of the ground stress of the large-deformation tunnel of the soft rock of a certain engineering and simultaneously assisting the numerical simulation experiment.
Disclosure of Invention
In order to solve the problems that the existing method only can use the initial ground stress field in a local area range as a target, the distribution of the initial stress field is complex, large-scale analysis and calculation cannot be performed, and the calculation accuracy is low, the invention provides the inversion method of the ground stress field of the railway deep-buried soft rock large-deformation tunnel, and the inversion method has the advantages of accurate local range of obtained results and small calculation amount.
The technical scheme adopted by the invention for realizing the purpose is as follows: a railway deep-buried soft rock large deformation tunnel ground stress field inversion method is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: distributing a plurality of surrounding rock stress monitoring points;
step two: monitoring the surrounding rock stress value of each surrounding rock stress monitoring point;
step three: stress values of three surrounding rock stress monitoring points and surrounding rock stress monitoring point coordinates are selected to establish a ground stress function expression
Wherein, in the step (A),
the stress value of any coordinate point; x and y are coordinate values; i. j and m represent three surrounding rock stress monitoring points;
step four: the surrounding rock stress value of each surrounding rock stress monitoring point is brought into a ground stress function, and surrounding rock stress of each point in the whole surrounding rock area is calculated;
step five: and comparing the magnitude of the calculated value and the measured value of the geostress function of each surrounding rock stress monitoring point, wherein the calculated value and the measured value of the geostress function are highly similar, the calculation result can be applied to the inversion of the bias geostress field with two-dimensional anisotropy, and the method can be popularized to the inversion of the three-dimensional anisotropy geostress field.
Further, in the first step, the more monitoring points are distributed, the denser the stress inversion result is, and the more accurate the stress inversion result is.
Furthermore, in the step one, the number of the surrounding rock stress monitoring points is at least three, and the longitudinal distribution of the surrounding rock stress monitoring points cannot be on the same straight line.
Further, the number of the surrounding rock stress monitoring points is 7.
The invention has the technical effects and advantages that:
(1) the ground stress function has a simple and clear form, small calculation amount and high precision in a local area.
(2) The anisotropy of the ground stress field and the stress concentration area in the excavated tunnel can be well fitted, and the influence of the geological structure on the ground stress distribution is shown.
(3) According to the method, the stress values of other unknown points are conjectured according to the surrounding rock stress values of a limited number of surrounding rock stress monitoring points, the anisotropic ground stress field is obtained through accurate inversion, ground stress measurement point data can be directly adopted to carry out ground stress inversion of the whole ground area through a ground stress function, parameters such as a jointed stratum and the like do not need to be considered in the inversion, the inversion precision is related to the number and the interval of the measurement points of the ground stress, and the more the points are, the more the ground stress inversion result is accurate.
Drawings
FIG. 1 is a layout diagram of the stress monitoring points of the surrounding rock according to the invention;
FIG. 2 is a cross section distribution diagram of the pressure values of the surrounding rock at the stress monitoring points of the surrounding rock;
FIG. 3 is a cloud diagram of the ground stress distribution inverted by the method of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
Example (b):
in this embodiment, the tunnel is integrally in the form of tectonic denudation and erosion of low-middle mountain landform, the surrounding rocks at the monitored fracture surface are mainly Jurassic and Pingxiang groups, small red bridge group mudstone, sandstone with shale, conglomerate and the like, the hard degree of the main lithologic rocks is divided into soft rocks which are seriously or seriously affected by the geological structure, and joints are relatively developed or developed. When the surrounding rock is in a block (stone) and crushed (stone) embedded structure, positioning the IV level; when the rock mass is broken to be in a gravel-broken loose structure, the grade is V.
As shown in fig. 1-3, a method for inverting a ground stress field of a railway deep-buried soft rock large-deformation tunnel comprises the following steps:
the method comprises the following steps: laying 7 surrounding rock stress monitoring points, as shown in fig. 1, the more the monitoring points are laid, the more the intensity is, the more accurate the inversion result is, and the longitudinal distribution of the surrounding rock stress monitoring points cannot be on the same straight line;
step two: monitoring the surrounding rock stress values of all surrounding rock stress monitoring points, as shown in fig. 2, the maximum surrounding rock pressure appears at the left arch waist, the surrounding rock pressure at the left arch waist is greater than that at the right arch waist, the right surrounding rock pressure at the maximum span is greater than that at the left arch foot, the right surrounding rock pressure at the arch foot is greater than that at the left arch foot, the situation of obvious asymmetry is presented, the situation is possibly influenced by bias voltage, and meanwhile, the surrounding rock of the tunnel is considered to present obvious orthogonal anisotropy according to the category (shale) of the rock; the current maximum surrounding rock pressure appears at the left arch waist, exceeds 260kPa, and the distribution of the ground stress field is uneven;
step three: selecting stress values of three surrounding rock stress monitoring points and coordinates of the surrounding rock stress monitoring points to establish a ground stress function expression, and establishing the ground stress function expression as follows:
in the formula
Is the stress value of any point;
、
、
the parameter is an intermediate parameter and can be determined by the stress of a surrounding rock stress monitoring point; x and y are as followsMarking a value;
in the above-mentioned crustal stress function, the stress values of three surrounding rock stress monitoring points and the coordinates of the surrounding rock stress monitoring points are respectively substituted into the above-mentioned formula, so that the stress value and the coordinates of the surrounding rock stress monitoring points can be obtained
；
In the above-mentioned ground stress function, expressed by a matrix equation, there are:
in the formula
，
；
In the above-mentioned ground stress function, the method is to find
Post substitution
Stress value of any surrounding rock stress monitoring point in unit
The stress value of the surrounding rock stress monitoring point is used for representing;
in the above-mentioned ground stress function, the matrix is inverted, and the undetermined parameter can be expressed by stress of surrounding rock stress monitoring point, i.e. it is
，
，
，
In the above-mentioned ground stress function,
it can also be written as:
；
step four: the surrounding rock pressure values of all surrounding rock stress monitoring points are brought into a ground stress function, surrounding rock stress of all surrounding rock stress monitoring points is calculated, the stress values of i, j and m points in a formula are measured, the stress values of other surrounding rock stress monitoring points with known coordinates are obtained through the ground stress function, as shown in fig. 3, the ground stress values corresponding to all the monitoring points can be clearly seen through a ground stress distribution cloud chart, the unit of horizontal and vertical coordinates in the graph is meter, and each coordinate point corresponds to one ground stress value;
step five: the method comprises the steps of calculating a ground stress function to obtain the stress concentration of surrounding rock stress at the left arch waist and the right side wall foot of the tunnel, obviously influencing the bias load and the anisotropy, comparing the sizes of a ground stress function calculated value and an actually measured value of each surrounding rock stress monitoring point, enabling the ground stress function calculated value to be highly similar to the actually measured value, applying the calculated result to the inversion of the bias ground stress field with the two-dimensional anisotropy, and popularizing the method to the inversion of the three-dimensional anisotropy ground stress field.
The result shows that the method has very high precision at the position of the surrounding rock stress monitoring point, can fully utilize the ground stress value at the position of the measuring point, can obtain the ground stress of any coordinate point, can be used for two-dimensional anisotropic ground stress inversion, applies the result to tunnel excavation and improves the construction efficiency.
TABLE 1 comparison of measured and inverted ground stresses at the measurement points
| Measurement point number | Actual measurement of ground stress MPa | Inverse ground stress MPa | Error% |
| 1 | 34.9 | 34.89 | 0.028653 |
| 2 | 34.6 | 34.59 | 0.028902 |
| 3 | 263.3 | 263.29 | 0.003798 |
| 4 | 177 | 176.99 | 0.00565 |
| 5 | 43 | 42.99 | 0.023256 |
| 6 | 217.6 | 217.59 | 0.004596 |
| 7 | 81.2 | 81.19 | 0.012315 |
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (4)
1. A railway deep-buried soft rock large deformation tunnel ground stress field inversion method is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: distributing a plurality of surrounding rock stress monitoring points;
step two: monitoring the surrounding rock stress value of each surrounding rock stress monitoring point;
step three: stress values of three surrounding rock stress monitoring points and surrounding rock stress monitoring point coordinates are selected to establish a ground stress function expression
Wherein, in the step (A),
the stress value of any coordinate point; x and y are coordinate values; i. j and m represent three surrounding rock stress monitoring points;
step four: the surrounding rock stress value of each surrounding rock stress monitoring point is brought into a ground stress function, and surrounding rock stress of each point in the whole surrounding rock area is calculated;
step five: and comparing the magnitude of the calculated value and the measured value of the geostress function of each surrounding rock stress monitoring point, wherein the calculated value and the measured value of the geostress function are highly similar, the calculation result can be applied to the inversion of the bias geostress field with two-dimensional anisotropy, and the method can be popularized to the inversion of the three-dimensional anisotropy geostress field.
2. The railway deep-buried soft rock large-deformation tunnel ground stress field inversion method according to claim 1, characterized by comprising the following steps: in the first step, the more monitoring points are distributed, the more densely the stress inversion result is accurate.
3. The railway deep-buried soft rock large-deformation tunnel ground stress field inversion method according to claim 1, characterized by comprising the following steps: in the first step, the number of the surrounding rock stress monitoring points is at least three, and the longitudinal distribution of the surrounding rock stress monitoring points cannot be on the same straight line.
4. The railway deep-buried soft rock large-deformation tunnel ground stress field inversion method according to claim 3, characterized by comprising the following steps: the number of the surrounding rock stress monitoring points is 7.
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| CN106021840A (en) * | 2016-02-03 | 2016-10-12 | 中原工学院 | Method for inverting transverse isotropic rock mass ground stress |
| CN114169238A (en) * | 2021-12-06 | 2022-03-11 | 广西长兴工程建设有限公司 | Automatic inversion method for joint development tunnel surrounding rock mechanical parameters |
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