CN117741734A - Stress measurement method of tunnel surrounding rock and application of stress measurement method in rock burst prevention and control - Google Patents
Stress measurement method of tunnel surrounding rock and application of stress measurement method in rock burst prevention and control Download PDFInfo
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Abstract
The invention relates to the technical field of rock burst control, solves the technical problems of low reliability and no representativeness in rock mass stress measurement near a tunnel face, in particular to a stress measurement method of tunnel surrounding rock and application thereof in rock burst control, and comprises the following steps: respectively arranging an earthquake survey line along the side walls of two sides of the excavated surrounding rock, and acquiring earthquake record data of the surrounding rock by exciting an earthquake source; and determining the rock mass wave velocity V of the surrounding rock according to the seismic record data. The stress measurement method provided by the invention can be used for directly measuring the stress of the rock mass near the face, and meanwhile, the distribution state of the stress of the rock mass in the area can be fully embodied through the arrangement of the mass points, so that the representativeness of the stress measurement is ensured, the reliability of the stress measurement result of the rock mass is improved, and the accuracy of criterion calculation in the rock burst prediction can be improved.
Description
Technical Field
The invention relates to the technical field of rock burst control, in particular to a stress measurement method of tunnel surrounding rock and application of the method in rock burst control.
Background
Rock burst is an engineering geological disaster of burst and injection of rock which suddenly occurs in tunnel and mine construction under high ground stress background. When the rock burst occurs, a large amount of broken rock blocks are sprayed out to destroy engineering structures, bury machine equipment, hurt personnel and harm greatly. Its occurrence is abrupt, and its forecast is an international problem, and no effective method is found at present.
Many researchers at home and abroad consider the ratio of the maximum shear stress or the main stress of the tunnel section to the compressive strength of the rock as the most main factor for determining the rock burst. Most researchers consider it as a filling condition, and rock burst must occur as long as it reaches a certain value; there are also some researchers' trends to comprehensive criteria, considering that the ratio of stress to strength is only a necessary condition, and only the rock burst occurs if all the conditions are satisfied.
The expression of these criteria is easy to understand, but there are some difficulties in the practical operation in engineering. It is difficult to quickly and accurately measure the stress of surrounding rock on site, and even if a point stress is measured, it is difficult to judge how representative it is. This results in inaccurate calculation of the criteria and is prone to erroneous decisions. And because the test of rock mass stress near the face is carried out in a bare rock state, great danger is brought to staff, the reliability and representativeness of a measuring result are difficult to ensure, so that the criterion forecasting method is difficult to implement, but the basic principle of the criterion has very important significance for guiding the development of forecasting technology.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a stress measurement method of tunnel surrounding rock and application thereof in rock burst prevention and control, and solves the technical problems of low reliability and no representativeness in rock mass stress measurement near a tunnel face.
In order to solve the technical problems, the invention provides the following technical scheme: a method of stress measurement of tunnel surrounding rock, the method comprising the steps of:
s1, arranging an earthquake survey line along the side walls of two sides of the excavated surrounding rock respectively, and acquiring earthquake record data of the surrounding rock by exciting an earthquake source;
s2, determining the rock mass wave velocity V of the surrounding rock according to the seismic record data;
s3, sampling surrounding rock to obtain a plurality of rock masses, and measuring the rock mass wave velocity of the rock masses in the state without deep buried stress through experiments；
S4, according to the rock wave velocity V and the rock wave velocityAnd calculating the rock mass stress sigma of the surrounding rock.
Further, in step S1, the specific process includes the following steps:
s11, respectively arranging N detectors at equal intervals L on two sides of the side wall of the surrounding rock close to the tunnel face;
s12, respectively arranging K seismic source excitation points on two sides of the side wall of the surrounding rock far away from the tunnel face to serve as seismic sources;
and S13, exciting a seismic source on the seismic source excitation point, and recording seismic record data of surrounding rock through a detector.
Further, in step S4, the rock mass stress σ is calculated as:
；
in the above-mentioned method, the step of,representing the rock mass wave velocity, namely the rock mass wave velocity in the deep buried stress state; />Representing the rock wave velocity, namely the rock wave velocity in the state of no deep buried stress; />Representing rock mass stress; />Representing parameters related to the integrity of the rock mass;the wave velocity-stress coefficient is shown, the … shows a higher order term through a pressure test, and the coefficient is small and can be ignored in practical application.
Further, the seismic source adopts an explosive or spark seismic source and a non-explosive seismic source for impacting the seismic source.
The technical scheme also provides an application method of the stress measurement method in rock burst prevention and control, and the method calculates the anchoring force required by the application of the rock mass stress of the tunnel surrounding rock near the tunnel face to the single anchor rod for rock burst prevention and controlAnd anchoring depth->Is calculated by the computer.
Further, the anchoring force required by the single anchor rodAnd anchoring depth->The calculation method of (1) comprises the following steps:
s10, calculating rock mass stress on each particle on tunnel surrounding rockAnd according to the rock stress on several particlesEstablishing a stress field of tunnel surrounding rock;
s20, according to the stress of the rock massCalculating the most of each particle in the surrounding rock of the tunnelTension margin in small principal stress direction；
S30, according to the tension allowance of each particle in the direction of the minimum main stress of the surrounding rock of the tunnelDrawing a stretching allowance contour map of all particles in the surrounding rock of the tunnel;
s40, determining the anchoring force required for preventing and controlling the rock burst single anchor rod according to the tension allowance contour mapAnd anchoring depth->。
Further, in step S20, the tension marginThe calculation formula of (2) is as follows:
；
in the above-mentioned method, the step of,is the tensile strength of the rock mass in the surrounding rock of the tunnel.
Further, in step S40, the anchoring depth required for the single boltThe method comprises the following steps: taking the 0 contour line in the tension allowance contour line as the anchoring depth required by preventing and controlling the rock burst single anchor rod>。
Further, in step S40, the anchoring forceThe calculation formula of (2) is as follows:
；
in the above-mentioned method, the step of,the safety coefficient is 1.8; />Is the pulling tension on the effective acting area of a single anchor rod (anchor rope).
By means of the technical scheme, the invention provides a stress measurement method of tunnel surrounding rock and application thereof in rock burst prevention and control, and the method at least has the following beneficial effects:
1. the stress measurement method provided by the invention can be used for directly measuring the stress of the rock mass near the face, and meanwhile, the distribution state of the stress of the rock mass in the region can be fully embodied through the arrangement of the mass points, so that the representativeness of the stress measurement is ensured, a calculation formula is constructed through the specific analysis between the wave velocity and the stress, the reliability of the stress measurement result of the rock mass is improved, the accuracy of the criterion calculation in the rock burst forecast is improved, and the misjudgment rate is further reduced.
2. According to the method, the rock mass stress obtained through measurement is applied to the prevention and treatment of rock burst, the theory is full, the accuracy is good, the anchoring force and the anchoring depth which are necessary for preventing and treating the rock burst can be determined under the condition that the safety performance of a tunnel is completely guaranteed, blind reinforcement is reduced, and engineering investment is reduced.
3. The application of the invention is a rock burst control method based on a rock burst secondary tensile stress cause mechanism, which can not only completely and effectively prevent rock burst, but also save engineering investment. Therefore, the method can be applied to high-ground-stress underground engineering and mining engineering, and has a very wide application prospect.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:
FIG. 1 is a schematic layout of a seismic line of the present invention;
FIG. 2 is a schematic illustration of a sample core of the present invention;
FIG. 3 is a graph showing the variation of wave velocity with depth according to the present invention;
FIG. 4 is a schematic diagram of the stress-wave velocity relationship test results for a class I rock mass according to the present invention;
FIG. 5 is a schematic diagram of the stress-wave velocity relationship test results of a type II rock mass according to the present invention;
FIG. 6 is a stress-strain curve of the marble of the present invention under the condition of 15 MPa;
FIG. 7 is a stress-strain curve of the marble of the present invention under 20 MPa;
FIG. 8 is a stress-strain curve of the marble of the present invention under the condition of 25 MPa;
FIG. 9 is a stress-strain curve of the marble of the present invention under the condition of 30 MPa;
FIG. 10 is a chart of geologic structure shifts in front of a face of the present invention;
FIG. 11 is a graph showing the wave velocity distribution of surrounding rock in front of the face of the present invention;
FIG. 12 is a schematic illustration of a contour map of the stretch allowance of the present invention.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. Therefore, the implementation process of how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented.
Rock burst is an engineering geological disaster of burst and injection of rock which suddenly occurs in tunnel and mine construction under high ground stress background. When the rock burst occurs, a large amount of broken rock blocks are sprayed out to destroy engineering structures, bury machine equipment, hurt personnel and harm greatly. Its occurrence is abrupt, and its forecast is an international problem, and no effective method is found at present.
Many studies have been conducted on rock burst forecasting. These studies have focused mainly on two aspects, one being the study of the precursors of rock burst, trying to forecast by looking for the regularity of the precursors; on the other hand, the research of the rock burst mechanism searches the condition of rock burst occurrence and searches a forecasting path.
At present, research on rock burst precursors mainly focuses on aspects of microseismic, acoustic emission, electromagnetic radiation and the like. Before the occurrence of the rock burst, the acoustic emission and the microseismic activity are frequent and the energy is enhanced, but the relation between the activity and the occurrence time and intensity of the rock burst is not clear, and no rule which can be followed is found yet. In recent years, many on-site monitoring experiments are carried out, for example Yang Zhiguo (2008), in the mountain copper mine of white gourd, the microseism activity of a mining area is monitored and analyzed by utilizing a microseism monitoring system, and the relation between the microseism and rock burst is sought; tang Chunan (2010) carrying out rock burst prediction research by adopting microseismic monitoring in the mosaic secondary TBM diversion tunnel; chen Binghui (2010) and Cheng Wuwei (2010) monitor acoustic emissions during the whole TBM tunneling process in the mall secondary diversion tunnel; tang Shaohui (2002) and Liu Weidong (2009) have conducted intensive studies on the characteristics of a rock mass micro-fracture signal and a construction interference signal, and found that it is difficult to distinguish a micro-shock, an acoustic emission signal and a construction interference even by means of waveform analysis, adaptive filtering, wavelet waveform analysis, and the like. There are several problems to be solved in the research of the relation between microseismic and acoustic emissions and rock burst:
(1) At present, research discovers that the relation between the occurrence of rock burst and the time sequence and the quantity of microseismic and acoustic emission signals is not clear, and the occurrence of rock burst cannot be judged according to precursors;
(2) The identification of the rock mass micro-fracture signals is difficult, and the construction interference signals and the micro-vibration signals have strong similarity and are difficult to distinguish;
(3) The acoustic emission monitoring distance is limited, the positioning error is large, and the acoustic emission monitoring distance is difficult to be practically applied to engineering. The prediction of rock burst with acoustic emissions and microseismic precursors should be a very promising approach, but the state of the art has not yet reached a level of reliability.
Electromagnetic radiation has been used in coal mines as a precursor to rock burst. Experimental observation shows that the rock mass is accompanied by electromagnetic radiation when internal fracture occurs, and the electromagnetic radiation energy index and the pulse index show obvious changes before and after rock burst occurs. However, the mechanism of the generation of the rock explosion is not clear at present, the electromagnetic radiation characteristics of different lithologies are obviously different, and the critical value of the rock explosion of various rocks is difficult to determine. At present, the research of electromagnetic radiation method forecast is mainly focused on coal mines, and the electromagnetic interference in tunnels is large and difficult to apply.
In summary, the precursor phenomena such as microseismic, acoustic emission and electromagnetic radiation do have a certain reaction before the occurrence of the rock burst, but no criterion for reliably predicting the occurrence time and intensity of the rock burst is found at present, and further research is needed.
The main aim of the research of the rock explosion mechanism is to search the main cause of the rock explosion, search the necessary condition and the sufficient condition of the rock explosion, establish the criterion standard of the rock explosion, and predict the section and the intensity level of the rock explosion. The research works mainly comprise the steps of observing and summarizing engineering geological conditions and ground stress states of rock burst occurrence through engineering practice, and combining rock physical mechanics experiments and theoretical analysis to analyze and extract main factors and technical indexes affecting the rock burst so as to establish a discrimination mode. At present, the research on the rock burst mechanism is popular at home and abroad.
Four researchers at home and abroad have influence, E.Hoek, turchainnov and Russense respectively propose methods for judging the occurrence degree of rock burst according to the ratio of the maximum tangential stress of a tunnel to the uniaxial compressive strength of the rock according to the respective researches, and the methods are slightly different in numerical values of classification. Unlike the former three, kidybinski's research concept is that he claims a method of discriminating rock burst by the ratio of elastic energy to loss strain energy.
According to the research experience of the Qinling mountain tunnel in China Gu Mingcheng, a 4-factor comprehensive judging method is provided, and comprises the following steps of: uniaxial compression and tensile strength ratio of rock and energy storage condition: the method for judging the ratio of the maximum shear stress to the uniaxial compressive strength is not essentially different from the Hoek method, but is more convenient to apply, zhang Jingjian (2008) provides comprehensive revisions to the criteria of Gu Mingcheng and Tao Zhenyu, and Wu Faquan (2010) derives a stress criterion and an energy criterion by using the Griffis strength theory.
In view of the above criteria, researchers consider that the ratio of the maximum shear stress or principal stress of the tunnel section to the compressive strength of the rock is the most important factor in determining the rock burst. Most researchers consider it as a filling condition, and rock burst must occur as long as it reaches a certain value; there are also some researchers' trends to comprehensive criteria, considering that the ratio of stress to strength is only a necessary condition, and only the rock burst occurs if all the conditions are satisfied.
The expression of these criteria is easy to understand, but there are some difficulties in the practical operation in engineering. It is difficult to quickly and accurately measure the stress of surrounding rock on site, and even if a point stress is measured, it is difficult to judge how representative it is. This results in inaccurate calculation of the criteria and is prone to erroneous decisions. And because the test of rock mass stress near the face is carried out in a bare rock state, great danger is brought to staff, the reliability and representativeness of a measurement result are difficult to ensure, so that the criterion forecasting method is difficult to implement, but the basic principle of the criterion has very important significance for guiding the development of forecasting technology.
Based on the technical defects in the prior art, please refer to fig. 1-12, the present embodiment provides a stress measurement method of tunnel surrounding rock and an application thereof in rock burst prevention, wherein the stress measurement method comprises the following steps:
s1, arranging an earthquake survey line along the side walls of two sides of the excavated surrounding rock respectively, and acquiring earthquake record data of the surrounding rock by exciting an earthquake source; in step S1, the specific process includes the following steps:
s11, respectively arranging N detectors at equal intervals L on two sides of the side wall of the surrounding rock close to the tunnel face;
s12, respectively arranging K seismic source excitation points on two sides of the side wall of the surrounding rock far away from the tunnel face to serve as seismic sources;
and S13, exciting a seismic source on the seismic source excitation point, and recording seismic record data of surrounding rock through a detector.
Specifically, as shown in fig. 1, a seismic line is arranged along each side of the side walls of two sides of the excavated surrounding rock, the length of the seismic line is determined according to the field conditions, and generally, 4 detectors are arranged on each side, and the interval is 4m. After the seismic source excitation is used, 3-direction data in the axial direction, the lateral horizontal direction and the lateral vertical direction of the tunnel are recorded through detectors; the number of channels of the seismograph is more than 24, and the seismograph can be matched with non-explosive sources such as explosive sources, spark sources, impact sources and the like.
S2, determining the rock mass wave velocity V of surrounding rock according to the seismic record data, analyzing the seismic record data by using TST tunnel seismic data processing software after the seismic record data are acquired, and obtaining the rock mass wave velocity V in front of a tunnel and the distribution condition of geological structures, so that the rock mass wave velocity V can be directly determined by means of the prior art, and the rock mass wave velocity V can also be determined by adopting other methods, and the method is not limited in the embodiment.
S3, sampling surrounding rock to obtain a plurality of rock masses, and measuring the rock mass wave velocity of the rock masses in the state without deep buried stress through experimentsThe method comprises the steps of carrying out a first treatment on the surface of the Sampling at the position of the surrounding rock, where the stress of the rock mass is required to be measured, sampling rock blocks, namely cores, at different positions by drilling equipment, and measuring the wave velocity in the cores in a laboratory, wherein the drilled sample, namely the cores, are in a normal pressure state under the conventional condition, so that the wave velocity of the rock blocks in the state without deep buried stress can be reflected by experiments>As shown in fig. 2, is a rock mass sampled in an actual sceneAnd (3) a sample.
S4, according to the rock wave velocity V and the rock wave velocityThe rock mass stress sigma of the surrounding rock is calculated, and the calculation formula of the rock mass stress sigma is as follows:
；
in the above-mentioned method, the step of,representing the rock mass wave velocity, namely the rock mass wave velocity in the deep buried stress state; />Representing the rock wave velocity, namely the rock wave velocity in the state of no deep buried stress; />Representing rock mass stress; />Representing parameters related to the integrity of the rock mass; />The wave velocity-stress coefficient is shown, the … shows a higher order term through a pressure test, and the coefficient is small and can be ignored in practical application. After the parameters of the rock mass are experimentally determined, the stress state of the position of the rock mass can be calculated according to the wave velocity V of the rock mass detected by an earthquake method.
In step S4, in order to verify the feasibility of the rock mass stress σ calculation formula, the present embodiment is demonstrated by the following, specifically:
the basic theory of rock mechanics holds that the wave velocity of a rock mass depends on the elastic modulus and density of the rock mass. In practical engineering, the elastic modulus and the density are related to the stress state of the rock mass in addition to lithology and the integrity of the rock mass. The inventor finds rock mass by testing wave velocity of drilling rock mass in a small bay hydropower station and a mall hydropower stationThe wave velocity of the rock mass is increased along with the depth and is larger than that of the rock core, so that the integrity of the rock mass is realizedA peculiar phenomenon of more than 1 is called wave velocity reverse hanging phenomenon. As shown in fig. 3, the variation of wave velocity with depth is demonstrated.
The inventor shows through the sound wave test result in the main building of the first-stage hydropower station of the brocade screen that the rock mass sound wave velocity in the surrounding rock can reach 6300 m/s under the high stress condition, which is far higher than the normal wave velocity of the indoor complete rock core, that is to say, the internal stress of the rock mass is increased at the same time in the high surrounding pressure state, the elastic modulus is increased, and the rock wave velocity is increased. According to the basic theory of sound waves, the phenomenon can be conveniently analyzed according to the logic relation between the sound wave speed and the stress and the experimental result of rock mechanics.
1. Mathematical relationship between wave velocity and elastic modulus
In practical engineering, the wave propagation speed can be set according to the transverse wave propagation speed in the infinite body of the Hooke mediumAnd longitudinal wave velocity->Is calculated by the formula:
；
at a known transverse wave propagation velocityAnd longitudinal wave velocity->Can push G and/or ++under the precondition of (1)>And E, wherein->For sonic velocity, G and E are elastic moduli as follows:
；
in the above-mentioned method, the step of,is the density of the medium; />Is lame constant, < >>。
From the above, it is apparent that when the elastic modulus of the rock mass or rock mass is relatively high, the corresponding sonic wave velocityWill increase. Since the elastic modulus of rock is different in different stress environments, in a high stress environment of the east edge of Qinghai-Tibet plateau, the problem of researching the acoustic wave velocity of rock has to be considered, so that the influence of high ground stress on the elastic modulus of rock mass is formed, and the influence of high ground stress on the acoustic wave velocity of rock mass (rock mass) is formed.
2. Preliminary relation of elastic modulus and stress
The elastic modulus of rock is different in different stress environments, and the phenomenon is widely known in laboratory true and false triaxial rock mechanics experiments. Fig. 6 to 9 are stress-strain curves of marble under 15MPa, 20MPa, 25MPa, and 30MPa, respectively, in a certain engineering.
From the experimental curves of fig. 6-9 described above, it can be seen that the elastic modulus of the rock increases significantly with increasing surrounding rock. The increase in modulus of elasticity in turn ultimately leads to an increase in the sonic wave velocity of the rock. In underground engineering with lower ground stress, the wave velocity of the rock mass is often not changed greatly, so that the rock mass acoustic wave velocity can be directly compared with the rock mass (not loaded) acoustic wave velocity, the damage degree of the rock mass is judged, and the development degree of the EDZ is researched.
3. Research current situation of rock mass wave velocity detection technology
The detection of the rock mass wave velocity has a mature technology, so that the distribution of parameters such as the rock mass longitudinal wave velocity, the transverse wave velocity, the poisson ratio and the like along the tunnel mileage can be obtained, and the velocity and the positioning accuracy are better than 10%. The technologies are used for advanced prediction of tunnel geology, prediction of engineering geology problems such as fracture structures, fracture zones, karst, rock mass engineering categories and the like, obtain good effects, and are not used for research of rock burst prediction. The main consideration in advanced geological forecast is the low stress state, and the influence of the ground stress on the wave velocity is small.
In early tunnel geological advanced forecasting research, the applicant and the application team have established a set of brand-new seismic wave method tunnel advanced forecasting methods TST (Tunnel Seismic Tomography). The method greatly improves the resolution ratio based on the backscattering theory and the synthetic aperture offset imaging technology; extracting a front echo by adopting a direction filtering technology, filtering out a direction-finding echo and surface wave interference, and reducing false alarm; and the wave speed scanning analysis is realized by adopting the principle of superposition energy maximization. The geological structure in the range of 100-150 meters in front of the face can be obtained, the wave velocity distribution of rock mass in front of the face can be obtained, and the error is less than 10%. Typical results are shown in fig. 10 and 11, wherein fig. 10 is a geological structure migration image represented by rock mass wave impedance change, and the abscissa of the image is tunnel mileage and the ordinate is tunnel transverse distance. Blue stripes represent lithologic change interfaces of rock mass from hard to soft, red represents lithologic change interfaces from soft to hard, and a combination of blue and red indicates the presence of fracture zones, etc. The dense stripes represent structural development and the sparse stripes indicate complete rock mass. Fig. 11 is a wave velocity distribution diagram of surrounding rock in front of a face, wherein the abscissa represents tunnel mileage, and the ordinate represents wave velocity, wherein different colors represent different wave velocities, and the wave velocities are sequentially from red to blue and from high to low.
To sum up, due to the rock integrity factorIs defined as rock mass wave velocity and rock mass wave velocity +.>Squaring the ratio, then:
；
wherein V represents the rock mass wave velocity, i.e. the rock mass in-situ wave velocity shown in fig. 3;the rock mass wave velocity is expressed, namely, the rock mass wave velocity in the state of no deep buried stress. In general, the rock mass contains cracks, water and other reasons, and the in-situ wave velocity of the rock mass is lower than that of the rock core, so the rock mass integrity coefficient is +.>Less than 1. However, the rock mass integrity factor +.>The phenomenon of hanging upside down more than 1 shows that the wave velocity of the rock mass is related to lithology and integrity, and is also closely related to the stress state. In the research, the indoor test of the wave velocity and pressure relation is carried out on two rock masses, the test result also clearly shows that the wave velocity and the stress have clear positive correlation relation, the positive correlation relation can be expressed by a power function, the result is as shown in fig. 4 and 5, a functional relation curve of the wave velocity and the stress of the rock mass is established by taking the axial stress as an abscissa and the longitudinal wave velocity of the rock mass as an ordinate, and the wave velocity-stress parameters such as b, c and the like are obtained through function fitting in combination with test data.
；
In the above-mentioned method, the step of,representing the rock mass wave velocity, namely the rock mass wave velocity in the deep buried stress state; />Representing the wave velocity of the rock mass, i.e. the wave velocity of the rock mass in the state without deep buried stress, can be passed by the sampleTesting and determining; />Representing rock mass stress; />Representing parameters related to the integrity of the rock mass, taking 1 for the complete rock mass and the deep buried rock mass, typically less than 1; />The wave velocity-stress coefficient is shown, the … shows a higher order term through a pressure test, and the coefficient is small and can be ignored in practical application. After the parameters of the rock mass are experimentally determined, the stress state of the position of the rock mass can be calculated according to the wave velocity V of the rock mass detected by an earthquake method.
In the invention, the method can also forecast the possible section and grade of the rock burst by combining the compressive strength test result of the rock core, which is a new way for rock burst prediction through wave velocity detection.
In this embodiment, the rock mass stress obtained by the stress measurement method is also provided to be applied to rock burst prevention and control, and the specific contents are as follows:
the rock burst is a project geological disaster commonly encountered in deep underground engineering, especially in southwest China, the construction ground stress value is very high, large-scale underground engineering is numerous, and the rock burst problem becomes a problem which must be considered in engineering construction, and the construction safety and the long-term operation safety of the engineering are deeply influenced.
The traditional method for preventing and controlling the rock burst is based on the knowledge of the mechanism of the rock burst pressure shear damage cause. Based on the knowledge, only the compressive stress and the shear stress in the surrounding rock of the tunnel can be controlled in engineering design, and the prestress of the anchor cable is used for resisting the compressive stress and the shear stress in the surrounding rock to prevent and treat the rock burst. However, because the compressive stress and the shear stress in the surrounding rock are very high in magnitude, the compressive shear stress which can cause the rock burst is generally above 5MPa, and the strongest engineering anchoring means have to be adopted to counter the compressive shear stress, so that the engineering investment is doubled.
New researches show that the theory of the mechanism of the pressure shear cause of the rock burst is not complete. In fact the rock burst is induced by a secondary tensile stress generated under conditions of compressive shear stress. There is no implosion without secondary tensile stress. All the results of the microscopic mechanism observation experiments (SEM experiments) of the rock burst prove the secondary tensile stress causative mechanism of the rock burst. Based on the new cause mechanism knowledge, the rock burst control method generates necessarily generated quality change. From the traditional control of compressive shear stress in surrounding rock to control rock burst, sublimation to control of secondary tensile stress to control rock burst is a qualitative leap. Because the secondary tensile stress is much lower than the compressive shear stress in magnitude and is generally within 1MPa, the anchoring strength and engineering investment can be greatly reduced.
The application is a rock burst control method based on a rock burst secondary tensile stress causative mechanism. Not only can completely and effectively prevent rock burst, but also can save engineering investment. The method can be applied to high-ground-stress underground engineering and mining engineering, and has a very wide application prospect.
Aiming at the defects of the traditional rock burst compression shear stress control, the method has the advantages that the specific application method is obtained by applying the measured rock mass stress to the rock burst control, the theory is full, the accuracy is good, the anchoring force and the anchoring depth which are necessary for rock burst control can be determined under the condition that the tunnel safety performance is completely ensured, the blind reinforcement is reduced, and the engineering investment is reduced.
In order to achieve the above effects, the application method provided in this embodiment includes the following steps:
s10, calculating rock mass stress on each particle on tunnel surrounding rockAnd according to the rock stress on several particlesEstablishing a stress field of tunnel surrounding rock, +.>Representing the rock mass stress on the ith particle; due to the rock mass even at one pointStress is also difficult to judge how representative it is, thus leading to inaccuracy of criteria and easy to cause erroneous judgment. For example, in the rock burst prediction research of the underground tunnel group of the secondary hydropower station of the brocade, two inventors respectively predict according to criteria, and the prediction results of the two are greatly different. The two auxiliary tunnel rock burst sections are 18.48% and 16.29% of the total length, the 15% of the drain tunnel rock burst section, and the calculation result of the criterion method is quite different from the actual situation.
In this step, the stress field is established by measuring the stress of the rock mass near the face by the stress measurement method, and a plurality of mass points can be arranged in the region to measure the stress of the rock mass respectively, so that the stress field capable of representing the region is established by taking the mass points as the abscissa and the stress of the rock mass as the ordinate, and the stress distribution state of the region is represented.
S20, according to the stress of the rock massCalculating the tension allowance of each particle in the direction of the minimum main stress of the surrounding rock of the tunnelTension allowance->The calculation formula of (2) is as follows:
；
in the above-mentioned method, the step of,the tensile strength of the rock mass in the surrounding rock of the tunnel;
the definition of the tension allowance is defined on the basis of the control principle of the tensile stress of the surrounding rock explosion, and the rock explosion of the tunnel surrounding rock essentially belongs to brittle surrounding rock fracture. The modes of burst fracture of brittle surrounding rock can be divided into three types: pure Zhang Polie, zhang Jian fracture and compression shear fractureThe source is as follows: theoretical analysis on the cause of rock burst of brittle rock mass. Of the three types of pure Zhang Polie, zhang Jian and compression shear fracture, pure sheet fracture is requiredAnd->The lowest magnitude, i.e. the lowest strain energy required. In the case of a free space, the breaking process of the rock always selects the lowest energy mode for breaking.
Therefore, in underground engineering, a rock burst which breaks in the direction of the excavated free surface always starts to break from the pure fracture type, and since the rock burst always starts to break from the pure fracture type and faces the free direction, the tension allowance of the rock mass in the surrounding rock of the tunnel has a critical meaning for controlling the rock burst.
On the basis of the tensile strength of the rock mass and the tensile stress field of the rock mass, the tensile allowance in the direction of the minimum main stress of the surrounding rock of the tunnel is establishedIs a calculation formula of (2). Tension allowance of a certain particle in surrounding rock>When the pressure is less than or equal to 0, tension fracture of surrounding rock possibly occurs, and the tension fracture is a necessary condition for rock burst.
S30, according to the tension allowance of each particle in the direction of the minimum main stress of the surrounding rock of the tunnelDrawing a stretching allowance contour map of all particles in the tunnel surrounding rock, and scientifically determining the occurrence area of rock burst and corresponding anchoring prevention measures as shown in fig. 12 by drawing the stretching allowance contour map of all particles in the tunnel surrounding rock, and calculating the stretching allowance of each particle in the direction of the minimum main stress of the tunnel surrounding rock>And then, summarizing all the data to draw a stretching allowance contour map, wherein the stretching allowance contour map can be automatically generated or hand-drawn by adopting corresponding software.
S40, determining the anchoring force required for preventing and controlling the rock burst single anchor rod according to the tension allowance contour mapAnd anchoring depthThe method comprises the steps of carrying out a first treatment on the surface of the As shown in fig. 12, in the contour map of the tension margin, the contour line with the tension margin equal to 0 is determined as the anchoring bottom boundary required by rock burst control, and the depth is the anchoring depth +.>The method comprises the following steps: the 0 contour line is used as the anchoring depth required by preventing and controlling the rock burst single anchor rod>。
Correspondingly, during the anchoring process, the tensile stress in the axial direction of the anchor rod (anchor cable) is increasedDifferent, for engineering safety, tensile stress is adopted in the design>Is carried into the calculation, i.e. using +.>Carrying out calculation to obtain maximum tension allowance +.>The calculation formula is as follows:
；
in the above-mentioned method, the step of,is the maximum value of tensile stress in the rock mass, < >>Is the tensile strength of the rock mass.
Tension on effective area of single anchor rod (anchor cable) according to definition of tension allowanceThe calculation formula of (2) is as follows:
；
wherein,is the effective acting area of a single anchor rod (anchor rope).
The anchoring force is determined by the principle that the reinforcing measures can counteract tensile stress in the rock mass, prevent rock burst and meet certain safety factor requirements, so the anchoring forceThe calculation formula of (2) is as follows:
；
in the above-mentioned method, the step of,for the permanent anchor cable, the safety coefficient is generally set to be 1.8 according to technical specifications of GB50086-2015 rock-soil anchor rod and shotcrete support engineering.
Therefore, after the anchoring depth and the anchoring force are determined, engineering designers can design corresponding anchoring measures, the anchoring depth is shallow, the anchoring force is small, the anchor rod can be used for anchoring, and otherwise, the anchor cable is needed for anchoring.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, so that the same or similar parts between the embodiments are referred to each other. For each of the above embodiments, since it is substantially similar to the method embodiment, the description is relatively simple, and reference should be made to the description of the method embodiment for relevant points.
The foregoing embodiments have been presented in a detail description of the invention, and are presented herein with a particular application to the understanding of the principles and embodiments of the invention, the foregoing embodiments being merely intended to facilitate an understanding of the method of the invention and its core concepts; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (9)
1. A method for measuring stress of surrounding rock of a tunnel, which is characterized by comprising the following steps:
s1, arranging an earthquake survey line along the side walls of two sides of the excavated surrounding rock respectively, and acquiring earthquake record data of the surrounding rock by exciting an earthquake source;
s2, determining the rock mass wave velocity V of the surrounding rock according to the seismic record data;
s3, sampling surrounding rock to obtain a plurality of rock masses, and measuring the rock mass wave velocity of the rock masses in the state without deep buried stress through experiments；
S4, according to the rock wave velocity V and the rock wave velocityAnd calculating the rock mass stress sigma of the surrounding rock.
2. The stress measurement method according to claim 1, wherein in step S1, the specific process includes the steps of:
s11, respectively arranging N detectors at equal intervals L on two sides of the side wall of the surrounding rock close to the tunnel face;
s12, respectively arranging K seismic source excitation points on two sides of the side wall of the surrounding rock far away from the tunnel face to serve as seismic sources;
and S13, exciting a seismic source on the seismic source excitation point, and recording seismic record data of surrounding rock through a detector.
3. The method according to claim 1, wherein in step S4, the rock mass stress σ is calculated by the formula:
；
in the above-mentioned method, the step of,representing the rock mass wave velocity, namely the rock mass wave velocity in the deep buried stress state; />Representing the rock wave velocity, namely the rock wave velocity in the state of no deep buried stress; />Representing rock mass stress; />Representing parameters related to the integrity of the rock mass; />The wave velocity-stress coefficient is shown, the … shows a higher order term through a pressure test, and the coefficient is small and can be ignored in practical application.
4. The method of claim 2, wherein the source is a non-explosive source such as an explosive or spark source, or an impact source.
5. A method for applying the stress measuring method according to any one of the claims 1 to 4 in rock burst control,the method is characterized in that the anchoring force required by a single anchor rod for rock burst prevention and control is applied to the rock mass stress of the tunnel surrounding rock near the tunnel face by calculatingAnd anchoring depth->Is calculated by the computer.
6. The method of claim 5, wherein the anchoring force required for a single boltAnd anchoring depth->The calculation method of (1) comprises the following steps:
s10, calculating rock mass stress on each particle on tunnel surrounding rockAnd according to the rock stress on several particles +.>Establishing a stress field of tunnel surrounding rock;
s20, according to the stress of the rock massCalculating the tension allowance +.f of each particle in the direction of the minimum main stress of the surrounding rock of the tunnel>；
S30, according to the tension allowance of each particle in the direction of the minimum main stress of the surrounding rock of the tunnelDrawing a stretching allowance contour map of all particles in the surrounding rock of the tunnel;
s40, determining the anchoring force required for preventing and controlling the rock burst single anchor rod according to the tension allowance contour mapAnd anchoring depth->。
7. The application method according to claim 6, wherein in step S20, the tension margin is increasedThe calculation formula of (2) is as follows:
；
in the above-mentioned method, the step of,is the tensile strength of the rock mass in the surrounding rock of the tunnel.
8. The application method according to claim 6, wherein in step S40, the anchoring depth required for the single anchor is setThe method comprises the following steps: taking the 0 contour line in the tension allowance contour line as the anchoring depth required by preventing and controlling the rock burst single anchor rod>。
9. The method of claim 6, wherein in step S40, the anchoring force is appliedThe calculation formula of (2) is as follows:
；
in the above-mentioned method, the step of,the safety coefficient is 1.8; />Is the pulling tension on the effective acting area of a single anchor rod (anchor rope).
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