CN109736886B - intensity stress ratio rock burst criterion method considering tunnel surrounding rock stress distribution - Google Patents
intensity stress ratio rock burst criterion method considering tunnel surrounding rock stress distribution Download PDFInfo
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Abstract
the invention discloses an intensity stress ratio rock burst criterion method considering tunnel surrounding rock stress distribution, which comprises the following steps: a concept of stress concentration is provided, and a quantitative representation method of a stress concentration value of the surrounding rock is provided; step two: based on a large number of engineering rockburst examples, combining stress concentration parameters with an intensity stress ratio and a rockburst grade in the aspect of describing stress field disturbance and rockburst strength to obtain measured data of the stress concentration, the intensity stress ratio and the rockburst intensity, and representing the measured data in a two-dimensional plane determined by the intensity stress ratio and the stress concentration; step three: and carrying out multi-parameter expression empirical fitting, carrying out comprehensive quantitative expression on a fitting result, and establishing a more accurate and reasonable criterion of rock burst strength-stress ratio. The rock burst strength prediction method provided by the invention is simple and easy to implement, is convenient for actual engineering, has higher prediction precision, and can be used for guidance of design and construction.
Description
Technical Field
The invention belongs to the technical field of underground engineering, and particularly relates to an intensity stress ratio rock burst criterion method considering tunnel surrounding rock stress distribution.
background
Deep rock mass excavation in a high ground stress environment is increasing, rock burst is one of major engineering geology problems of deeply buried long and large tunnels, and prevention and control problems of the deep rock mass excavation are more and more prominent. The accurate rockburst prediction is beneficial to adopting corresponding engineering measures in design and construction, and the loss caused by rockburst disasters is reduced or avoided. At present, rock burst is researched more theories, but various theoretical prediction methods provided based on the rock burst theory and the rock burst destruction mechanism have the problem of low accuracy rate in engineering application. Therefore, the research work of the rock burst mechanism and the prediction model has very important significance for reducing life and property loss and guiding engineering practice.
at present, in engineering practice, a simple grading method is generally adopted to predict the rock burst, wherein a stress ratio criterion is widely applied to prediction of strain type rock burst. The stress ratio rock burst criterion based on the strength theory mainly utilizes the ratio of tangential stress or far-field maximum principal stress borne by a rock body after engineering excavation to uniaxial compressive strength of surrounding rocks, and comprises a ceramic-damper criterion, a Norway Barton criterion, a Russense criterion and a Hoek criterion. In addition, the rock burst criterion comprises an energy method, a rigidity method, a lithology method, a critical depth method and the like. Since the combined influence of various factors cannot be considered, the result is often greatly different from the actual situation. Therefore, people introduce fuzzy mathematical methods and grey system theories to predict the rock burst and obtain certain effects, but the interrelation among all the influence factors is rarely studied deeply, and the prediction needs to artificially set the weight values of main factors and all discrimination factors, but the rock burst is a sudden complex catastrophe process, the importance weight value determined by experts or the objective weight value determined based on index values is difficult to comprehensively reflect the degree of interdependence or interrelation among the influence factors, and the application of the factors is also limited. Although the neural network method, the support vector machine method, the distance discrimination method and the like solve the problem, the problems are limited by the bottleneck problem of knowledge acquisition, and the application limitation exists.
The strain rock burst mainly occurs in the loading process of tangential stress concentration after cavern excavation, so that the strength-stress ratio criterion is often used as a key index in rock burst evaluation no matter a single-factor stress ratio rock burst criterion or a multi-factor nonlinear prediction method. The stress ratio rock burst criterion based on the strength theory is mainly based on the relation between the strength of rock and the secondary concentrated stress of excavated surrounding rock, and simply takes the relative magnitude of stress as a failure criterion. However, the deformation and damage of the surrounding rock caused by excavation not only depend on the stress of the rock mass, but also relate to a strain path and the original stress history of the strain path. In the process of excavating the underground cavern, surrounding rocks experience a complex stress path, the tangential loading stress of the surrounding rocks is larger at the cave wall and is gradually reduced towards the inside of the surrounding rocks by a certain gradient, and the distribution of the buried depth, the excavation mode, the geological structure and the like can be influenced. Therefore, the intensity criterion of simply considering the stress magnitude of the surrounding rock and neglecting the stress distribution has certain one-sidedness.
In summary, the stress state in the process of rock mass deformation failure and rock burst is very complex, and has certain uncertainty in a certain sense, and due to the uncertainty, simply taking the stress magnitude as the failure criterion is one-sided. At present, no rockburst distinguishing method comprehensively considering stress magnitude and distribution exists.
Disclosure of Invention
the invention aims to provide a strength-stress ratio rock burst criterion method considering stress distribution of tunnel surrounding rocks so as to solve the problems.
The technical scheme for solving the technical problems is as follows: a criterion method for judging the intensity stress ratio rock burst considering the stress distribution of tunnel surrounding rock comprises the following steps:
Step 1, a concept of stress concentration is provided to express the concentration degree of secondary disturbance stress in a surrounding rock disturbance area, namely surrounding rock stress distribution, and the physical meaning is as follows: reflecting the attenuation change condition of the tangential stress of the surrounding rock from the cave wall to the inside of the surrounding rock, and calculating the stress concentration by using the following formula,
Wherein eta is used to express the stress concentration of the surrounding rock in the tangential direction, wherein R0In order to excavate the hole diameter, the unit m is that the equivalent weight method can be adopted to calculate the hole diameter of the non-circular chamber; sigmaθThe maximum initial stress of the cross section of the tunnel before excavation is in unit of MPa; sigmaθmaxThe maximum value of the tangential stress of the hole wall is in MPa;
Step 2, obtaining the actually measured data of the stress concentration, the strength stress ratio and the rockburst intensity by using the existing engineering data, and expressing the rockburst intensity in a two-dimensional plane determined by the strength stress ratio and the stress concentration;
And 3, carrying out interval division on different intensities of the rock burst in a two-dimensional plane determined by the intensity stress ratio and the stress concentration, carrying out double-parameter rock burst intensity empirical fitting of the intensity stress ratio and the stress concentration, carrying out comprehensive quantitative expression on fitting results of all intensity intervals, and comprehensively judging the rock burst intensity by combining the intensity stress and the stress concentration.
Further, the formula of stress concentration in step 1 can be further simplified to
Wherein eta is used to express the stress concentration of the surrounding rock in the tangential direction, wherein R0In order to excavate the hole diameter, the unit m is that the equivalent weight method can be adopted to calculate the hole diameter of the non-circular chamber; sigmaθThe maximum initial stress of the cross section of the tunnel before excavation is in unit of MPa; sigmaθmaxThe maximum value of the tangential stress of the hole wall is expressed in MPa.
Furthermore, the concrete mode of comprehensively judging the rock burst strength by combining the strength stress and the stress concentration in the step 3 is as follows,
Judging that no rock burst exists when the strength stress ratio R is less than or equal to 0.3; when R is more than 0.3 and less than or equal to 0.4, judging the rock burst to be weak; and when R is more than 0.4, comprehensively judging the rock burst strength by combining the stress concentration eta and the strength stress R, judging weak rock burst when eta-2R is less than 1.5 or eta/R is more than or equal to 8.6, judging medium rock burst when eta-2R is more than or equal to 1.5 or eta-6.8R is less than 0.7, and judging strong rock burst when eta-6.8R is more than or equal to 0.7 or eta/R is less than 8.6.
the invention introduces the concept of stress concentration, discusses the correlation relation between rock burst and stress magnitude and stress distribution on the basis of summarizing a large number of engineering rock burst examples, combines stress concentration parameters with strength-stress ratio and rock burst grade in the aspect of describing stress field disturbance and rock burst strength, develops multi-parameter expression empirical fitting and establishes a more accurate and reasonable prediction method. The method has important theoretical value and application prospect for improving the prevention and control level of the rockburst disaster and reducing the loss of personnel, equipment and construction period.
specifically, the invention has the following technical characteristics and advantages:
1. The rock burst criterion based on the strength theory only considers the stress of surrounding rocks but not stress distribution of the surrounding rocks, the concept of stress concentration is introduced, a simplified calculation method is provided, a large number of engineering examples are combined, rock burst data obtained by engineering are represented in a two-dimensional plane of the stress concentration and strength stress ratio, multi-parameter expression empirical fitting is carried out, and the established rock burst criterion is higher in rock burst prediction accuracy.
2. the existing rock burst criterion is mainly considered by focusing on stress fields and rock mass mechanical characteristics, and influence on size effect is not directly related, while the size effect is always a hotspot for research in rock mechanics, but an effective research means and a calculation tool are lacked, and the criterion can combine rock burst and size effect from a quantitative angle.
3. The criterion overcomes the problem that the division of the traditional intensity stress ratio rock burst criterion interval is not uniform.
4. The established rock burst criterion is simple and convenient to apply, and can guide the design and construction of the deep-buried tunnel engineering.
Drawings
FIG. 1 shows the distribution of tangential stress within a certain depth range of the wall rock excavated by the chamber of the invention.
FIG. 2 is a two-dimensional distribution diagram of rock burst grades.
FIG. 3 is a fitting graph of a rock burst grade region.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the embodiments.
The method comprises the following specific implementation steps of:
Step 1: as shown in FIG. 1, in order to consider the stress distribution, it is necessary to make a series of simplifications on the stress disturbance area of the surrounding rock, and theoretical analysis shows that the stress and displacement change of the medium around the hole caused by load release is less than 5% outside 3 times of the hole diameter, so that the position of three times of the hole diameter is assumed to be equal to the original rock stress.
because the change rate of the surrounding rock stress is not a fixed value, the stress distribution is represented by the change rate of a straight line in order to conveniently represent the concentration degree of the secondary stress in the surrounding rock disturbance area and simplify the concentration degree into a triangle. Thereby, a stress concentration parameter is introduced:
Eta is used to represent the stress concentration in the tangential direction of the surrounding rock. In the formula, R0In order to excavate the hole diameter, the unit m is that the equivalent weight method can be adopted to calculate the hole diameter of the non-circular chamber; sigmaθthe maximum initial stress of the cross section of the tunnel before excavation is in unit of MPa; sigmaθmaxthe maximum value of the tangential stress of the hole wall is expressed in MPa.
For the calculation, we neglect the constant term and simplify it further to
Step 2: combining the site engineering rock burst data in the table 1, calculating to obtain the strength-stress ratio and the stress concentration eta of the surrounding rock of each rock burst cave, and expressing the calculated value in a two-dimensional plane determined by the strength ratio and the stress concentration, as shown in fig. 2, taking the stress concentration as an x-axis and the strength-stress ratio as a y-axis, and combining the engineering site data to obtain the actually measured data of the stress concentration, the strength-stress ratio and the rock burst intensity, which are expressed in the two-dimensional plane determined by the stress concentration and the strength-stress ratio.
And step 3: and (3) fitting the boundary regions of the rockburst intervals of different grades by using MATLAB programming, and establishing a rockburst strength criterion comprehensively considering the stress size and the stress distribution by using the boundary obtained by fitting as shown in figure 3. The method comprises the following specific steps: judging that no rock burst exists when the strength stress ratio R is less than or equal to 0.3; when R is more than 0.3 and less than or equal to 0.4, judging the rock burst to be weak; and when R is more than 0.4, comprehensively judging the rock burst strength by combining the stress concentration eta and the strength stress R, judging weak rock burst when eta-2R is less than 1.5 or eta/R is more than or equal to 8.6, judging medium rock burst when eta-2R is more than or equal to 1.5 or eta-6.8R is less than 0.7, and judging strong rock burst when eta-6.8R is more than or equal to 0.7 or eta/R is less than 8.6.
Wherein the strength-to-stress ratio R is sigmaθmax/σciDegree of stress concentrationUnit MPa.m-1，σciThe uniaxial compressive strength of the surrounding rock is unit MPa; the other parameters have the same meanings as described above.
TABLE 1 field engineering rockburst data
By referring to the method, the rock burst grades of other underground engineering samples are respectively predicted and evaluated to obtain the predicted intensity of other samples, and the intensity grade prediction result of the sample is compared with the actual rock burst intensity grade in the construction process, as shown in Table 2.
TABLE 2 prediction and actual results of the intensity of the domestic engineering rockburst
As can be seen from the statistical comparison in Table 2, the prediction accuracy of the traditional intensity stress ratio rock burst criterion is only about 40%, wherein the accuracy of Russense and Hoek criterion is 35.3%, the accuracy of Xunlengsheng criterion is 41.2%, and the rock burst prediction accuracy of the invention after considering stress distribution can reach 94.1%, which indicates that the accuracy of the technical scheme of the invention in rock burst prediction is higher.
[1] The strain type rockburst analysis and rockburst expression [ J ], the report on rock mechanics and engineering, 2013 and 8, 1520 and 1527.
the technical solutions described in the present invention are only exemplary embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes and substitutions based on the present invention should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (3)
1. A criterion method for judging the intensity stress ratio rock burst by considering the stress distribution of tunnel surrounding rock is characterized by comprising the following steps of:
Step 1, a concept of stress concentration is provided to express the concentration degree of secondary disturbance stress in a surrounding rock disturbance area, namely surrounding rock stress distribution, and the physical meaning is as follows: reflecting the attenuation change condition of the tangential stress of the surrounding rock from the cave wall to the inside of the surrounding rock, and calculating the stress concentration by using the following formula,
Wherein eta is used to express the stress concentration of the surrounding rock in the tangential direction, wherein R0In order to excavate the hole diameter, the unit m is that the equivalent weight method can be adopted to calculate the hole diameter of the non-circular chamber; sigmaθThe maximum initial stress of the cross section of the tunnel before excavation is in unit of MPa; sigmaθmaxThe maximum value of the tangential stress of the hole wall is in MPa;
Step 2, obtaining the actually measured data of the stress concentration, the strength stress ratio and the rockburst intensity by using the existing engineering data, and expressing the rockburst intensity in a two-dimensional plane determined by the strength stress ratio and the stress concentration;
And 3, carrying out interval division on different intensities of the rock burst in a two-dimensional plane determined by the intensity stress ratio and the stress concentration, carrying out double-parameter rock burst intensity empirical fitting of the intensity stress ratio and the stress concentration, carrying out comprehensive quantitative expression on fitting results of all intensity intervals, and comprehensively judging the rock burst intensity by combining the intensity stress and the stress concentration.
2. The method for judging the intensity stress ratio rockburst according to the stress distribution of the tunnel surrounding rock, as claimed in claim 1, wherein: the formula of stress concentration in step 1 can be further simplified to
wherein eta is used to express the stress concentration of the surrounding rock in the tangential direction, wherein R0In order to excavate the hole diameter, the unit m is that the equivalent weight method can be adopted to calculate the hole diameter of the non-circular chamber; sigmaθThe maximum initial stress of the cross section of the tunnel before excavation is in unit of MPa; sigmaθmaxThe maximum value of the tangential stress of the hole wall is expressed in MPa.
3. The method for judging the intensity stress ratio rockburst according to the stress distribution of the tunnel surrounding rock, as claimed in claim 1, wherein: the concrete way of comprehensively judging the rock burst strength by combining the strength stress and the stress concentration in the step 3 is as follows,
Judging that no rock burst exists when the strength stress ratio R is less than or equal to 0.3; when R is more than 0.3 and less than or equal to 0.4, judging the rock burst to be weak; and when R is more than 0.4, comprehensively judging the rock burst strength by combining the stress concentration eta and the strength stress R, judging weak rock burst when eta-2R is less than 1.5 or eta/R is more than or equal to 8.6, judging medium rock burst when eta-2R is more than or equal to 1.5 or eta-6.8R is less than 0.7, and judging strong rock burst when eta-6.8R is more than or equal to 0.7 or eta/R is less than 8.6.
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| CN110318808A (en) * | 2019-06-25 | 2019-10-11 | 武汉工程大学 | A kind of Rockburst Prediction Method introducing gradient stress |
| CN111368359B (en) * | 2020-02-25 | 2023-07-07 | 浙江大学城市学院 | Tunnel plate crack buckling type rock burst judging method |
| CN112989638B (en) * | 2021-05-18 | 2021-08-10 | 中南大学 | Method for calculating interaction stress of porous tunnel under far field and any surface stress |
| CN114778800B (en) * | 2022-04-28 | 2023-08-08 | 中交第一公路勘察设计研究院有限公司 | Multi-factor rock burst prediction method based on analysis method |
| CN117332240B (en) * | 2023-12-01 | 2024-04-16 | 中铁四局集团有限公司 | Rock burst prediction model construction method, storage medium, rock burst prediction method and system |
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