A rockburst prediction method and system for hard rock in high ground stress areas

Abstract

The present invention relates to the field of underground engineering technology, and discloses a rockburst prediction method for hard rock in high ground stress areas, comprising the following steps: A. determining the range of rockburst occurrence in rock mass; B. predicting the rockburst location: within the determined rockburst range, the rock mass is divided into parts, and rockburst prediction is performed on different parts of the rock mass; in step B, the following rockburst prediction is performed for each part: B11. determining the initial stress σ1 of the rock mass, the uniaxial compressive strength R c , uniaxial tensile strength of rock R t , calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v , B12, predict the rockburst location according to the following criteria: σ1≥0.15R c , R c ≥15R t , K v ≥0.55,W et ≥2.0; when the predicted location satisfies the above four criteria at the same time, the location is set as the rockburst location. The prediction method of the present invention can more accurately determine the rockburst location.

Description

Technical Field

[0001] The present invention relates to the field of underground engineering technology, and in particular to a rockburst prediction method and system for hard rock in high geostress areas. Background Art

[0002] Rockburst refers to the explosion of rock caused by the violent release of strain energy contained in rock strata or rock mass due to instability, usually accompanied by loud noise and scattering of collapsed rock fragments.

[0003] Based on the existing research results, rock burst prediction can be roughly divided into three categories: theoretical analysis method, field measurement method and engineering experience analogy method.

[0004] (1) Theoretical analysis method: The general method is to predict the possibility of rock burst after excavation based on the physical and mechanical parameters and stress state of the rock and the criterion obtained from the rock burst mechanism theory. The main criteria include E. Hoek stress criterion, Kidybinski energy criterion, Professor Hou Faliang's critical depth criterion, Tao Zhenyu's lithology criterion, Gu Mingcheng's comprehensive criterion and other criteria.

[0005] When there are multiple judgment factors in rockburst prediction, different judgment criteria may produce different prediction results, resulting in one judgment criterion predicting rockburst while another judgment criterion predicting no rockburst. If the effectiveness of the judgment results is not evaluated and analyzed, the judgment of multiple factors cannot produce more accurate results.

[0006] (2) On-site measurement method: On-site measurement method is a method of directly monitoring and testing the rock mass on site with the help of some necessary instruments. It can be used to determine the possibility of rock burst and to estimate the approximate time and scope of rock burst, so as to achieve the purpose of taking timely measures to evacuate workers and their equipment within the predicted time and scope, ensure safe production, and reduce construction cost losses. At present, there are two main on-site measurement methods at home and abroad: one is the direct contact method and the other is the geophysical method.

[0007] (3) Engineering experience analogy method: The engineering experience analogy method is a new rockburst intensity prediction method established on the basis of existing similar rockburst cases, which is summarized and analyzed by using mathematical principles and methods such as multi-objective decision science or statistical thinking, and taking multiple factors into consideration. These methods are often greatly affected by the sample or regional restrictions. For example, the neural network model has high requirements for samples, the distance discrimination model does not consider the influence of prior probability, and the sample selection is small and not typical enough.

[0008] The use of the above rockburst prediction method often leads to insufficient accuracy of the prediction results, which makes it impossible to accurately guide construction and excavation operations, which is not conducive to improving the efficiency of construction operations. Summary of the invention

[0009] The present invention aims to provide a rockburst prediction method and system for hard rock in high ground stress areas, so as to accurately determine the rockburst location.

[0010] In order to achieve the above object, the present invention adopts the following technical scheme:

[0011] A method for predicting rock burst in hard rock in high ground stress areas comprises the following steps:

[0012] A. Determine the scope of rock burst;

[0013] B. Predict rockburst location: Within the determined rockburst range, the rock mass is divided into parts and rockburst prediction is performed on different parts of the rock mass;

[0014] In step B, the following rockburst predictions are performed for each location:

[0015] B11. Determine the initial stress σ1 of the rock mass and the uniaxial compressive strength R of the rock mass c , uniaxial tensile strength of rock R t , calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v ,

[0016] B12. Predict the rockburst location based on the following criteria: σ1 ≥ 0.15R c , R c ≥15R t , K v ≥0.55,W et ≥2.0; when the predicted location meets the above four criteria at the same time, the location is set as the rockburst location.

[0017] The principle and advantage of this solution are: Since the geological conditions of each project are very complex, the present invention starts from four aspects, namely mechanical requirements, brittleness requirements, integrity requirements and energy storage requirements, and uses four criteria to more accurately determine the location of rockburst. The judgment conditions for rockburst in this solution are more perfect, which can improve the accuracy of prediction. After excavation and comparison with prediction, it was found that the rockburst damage type, rockburst grade, rockburst occurrence location, etc. are basically consistent.

[0018] In this plan, multiple locations are monitored according to the scale of the project and the complexity of the geological structure to make more accurate judgments on the rockburst development part, rockburst grade and rockburst damage type, so as to facilitate the guidance of construction and excavation operations, thus saving costs and improving efficiency and safety.

[0019] Preferably, as an improvement,

[0020] The step C is to determine the rockburst level, specifically:

[0021] According to the rockburst location predicted in step B, the maximum tangential stress of the rock mass, the rock cracking stress, and the rock failure stress are calculated for the rockburst location, and the rockburst level is determined according to the following criteria:

[0022] If σ max / (K v σ cd )>1.0or(100σ max ) / (GSIσ cd )>1.0, the rock burst level is severe rock burst;

[0023] If σ max / (K v σ cd ) = 0.5~1.0 or (100σ max ) / (GSIσ cd ) = 0.5~1.0, the rock burst level is severe rock burst;

[0024] If σ max / (K v σ ci ) = 0.5~1.0 or (100σ max ) / (GSIσ ci ) = 0.5~1.0, the rock burst level is medium rock burst;

[0025] If σ max / (K v σ ci )<0.5or(100σ max ) / (GSIσ ci )<0.5, the rockburst level is slight rockburst;

[0026] σ max is the maximum tangential stress of the surrounding rock of the cavern; ci is the rock crack initiation stress; cd is the rock failure stress; K v is the rock mass integrity coefficient; GSI is the geological strength factor.

[0027] This solution can predict the rockburst level at the predicted rockburst location, making it easier to understand the rockburst situation, so as to prepare in advance to take corresponding support measures according to the rockburst prediction and improve safety.

[0028] Preferably, as an improvement, the method further comprises step D, of checking the accuracy of the rockburst position predicted in step B:

[0029] The rock cave model is used to simulate the cave after excavation to obtain the location of stress concentration points as reference rockburst locations;

[0030] The reference rockburst location is compared with the predicted rockburst location to verify the accuracy of the predicted rockburst location.

[0031] This scheme can more accurately reflect the influence of the cavern excavation process and the deviatoric stress characteristics of the initial stress field, thereby improving the accuracy of the prediction results.

[0032] Preferably, as an improvement, when the overlap rate between the reference rockburst position and the predicted rockburst position reaches a set value, it is judged that the predicted rockburst position has a high accuracy;

[0033] If the coincidence rate between the reference rockburst position and the predicted rockburst position does not reach a set value, it is judged that the accuracy of the predicted rockburst position is low.

[0034] This scheme determines the accuracy of the predicted rockburst position by calculating whether the overlap rate between the reference position and the predicted rockburst position reaches a set value, thereby verifying the predicted position, which can further improve the accuracy of the prediction results and facilitate accurate guidance of excavation in the later stage.

[0035] Preferably, as an improvement, the calculation method of Kv in step B comprises the following steps:

[0036] According to the mechanical properties of the rock burst rupture surface, the type of rock burst damage is determined, and the value of Kv is determined according to the type of rock burst damage. The rock burst damage types include pressure-induced tensile rock burst, pressure-induced tensile fracture-bending rock burst, pressure-induced tensile fracture-shear rock burst, and pressure-induced tensile fracture-slip rock burst. The first three types are strain-type rock bursts, and the fourth type is a compound rock burst.

[0037] When it is a strain-type rockburst, Kv=1;

[0038] When it is a compound rockburst, Kv is the square of the ratio of the wave velocity of the rock mass and the rock under the same confining pressure conditions.

[0039] There are many types of rockbursts, and they occur in different locations. In this scheme, pressure-induced tensile rockbursts mainly occur in the side walls, while pressure-induced tensile-bending rockbursts and pressure-induced tensile-shear rockbursts mainly occur in the arch foot, the intersection of the caverns, the turning part, and the lower part of the side walls. Pressure-induced tensile-slip rockbursts are related to the development location of the structural surface, and they are developed in the side walls and arch feet. This scheme takes different values ​​of Kv according to different rockburst types, so it can be applied to different rockburst types and achieve corresponding predictions for different rockburst types, which can improve the accuracy of the prediction.

[0040] Preferably, as an improvement, it is suitable for the working condition that the axial direction of the cavern is parallel to the direction of the maximum principal stress and the rockburst is mainly controlled by the intermediate principal stress.

[0041] The prediction method of this scheme can reflect the impact of the cavern excavation process.

[0042] Preferably, as an improvement, it is suitable for high geostress areas and extremely high geostress areas.

[0043] The prediction method of this scheme has a wide range of applicability and is suitable for working conditions in high geostress areas and extremely high geostress areas.

[0044] A rockburst prediction system for hard rock in high ground stress areas, comprising:

[0045] A rockburst range determination module is used to determine the range of rockburst in the rock mass;

[0046] The rockburst location prediction module is used to predict the rockburst location within the rockburst range;

[0047] The rockburst location prediction module includes:

[0048] The rock mass part division module is used to divide the rock mass into different parts within the determined rock burst range;

[0049] The parameter acquisition module is used to receive the initial stress σ1 of the rock mass at each part, the uniaxial compressive strength R of the rock mass c , uniaxial tensile strength of rock R t ;

[0050] Calculation module, used to calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v ;

[0051] The prediction module is used to predict rockburst at each location in the rock mass location division module. For each location, when it satisfies σ1≥0.15R c , R c ≥15R t , K v ≥0.55,W et ≥2.0, the location is set as the rockburst location and the rockburst location is output.

[0052] Preferably, as an improvement, it also includes:

[0053] The simulation module is used to simulate the excavated cavern using the rock cavern model to obtain the location of the stress concentration point as a reference rockburst location;

[0054] A comparison module is used to compare the reference rockburst position with the predicted rockburst position, calculate the overlap rate between the reference rockburst position and the predicted rockburst position, and verify the prediction accuracy;

[0055] Output module, used to output prediction results.

[0056] Preferably, as an improvement, when the overlap rate between the reference rockburst position and the predicted rockburst position reaches a set value, the accuracy of the predicted rockburst position is judged to be high, and the predicted position is output as the rockburst position; if the overlap rate between the reference rockburst position and the predicted rockburst position does not reach the set value, the accuracy of the predicted rockburst position is judged to be low, and the predicted position is output as not the rockburst position.

[0057] Beneficial effects: The rockburst prediction system for hard rock in high-stress areas provided in this solution can realize the prediction and verification of the rockburst location. This solution can accurately verify the accuracy of the predicted rockburst location, thereby determining a more accurate rockburst location, which is convenient for guiding construction and excavation, saving costs, and improving efficiency and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of the destruction type of rock burst in an embodiment of the present invention.

[0059] Figure 2 This is a scene diagram of the rock burst damage type in an embodiment of the present invention.

[0060] Figure 3 This is a layout diagram for predicting rock burst in the pilot tunnel of the main powerhouse in an embodiment of the present invention.

[0061] Figure 4 This is a diagram showing the predicted rock burst layout for the side excavation of the main powerhouse in an embodiment of the present invention.

[0062] Figure 5 This is a diagram showing the predicted layout of rock burst in the pilot tunnel of the main transformer room in an embodiment of the present invention.

[0063] Figure 6 This is a diagram for predicting rock burst in the side excavation of the main transformer room in an embodiment of the present invention.

[0064] Figure 7 It is a layout diagram for predicting rock burst in the pilot tunnel of the tail adjustment chamber in an embodiment of the present invention.

[0065] Figure 8 This is a layout diagram for predicting rock burst in the side excavation of the tail adjustment chamber in an embodiment of the present invention.

[0066] Fig. 9 This is the rock burst prediction layout diagram of the pilot tunnel in layer I of the 1# tailwater tunnel in the embodiment of the present invention.

[0067] Fig.10This is the predicted layout diagram of rock burst in the side excavation of layer I of the 1# tailwater tunnel in the embodiment of the present invention.

[0068] Fig.11 This is the rock burst prediction layout diagram of the pilot tunnel in layer I of the 2# tailwater tunnel in the embodiment of the present invention.

[0069] Fig.12 This is the predicted layout diagram of rock burst in the side excavation of layer I of the 2# tailwater tunnel in the embodiment of the present invention.

[0070] Fig.13 Schematic diagram comparing surrounding rock damage and rockburst prediction for the main powerhouse layer I excavation in an embodiment of the present invention.

[0071] Fig.14 Schematic diagram comparing surrounding rock damage and rockburst prediction for the expansion of the tailgate chamber layer I in an embodiment of the present invention.

[0072] Fig.15 Schematic diagram comparing surrounding rock damage and rock burst prediction during upper excavation of No. 1 tailwater tunnel in an embodiment of the present invention. DETAILED DESCRIPTION

[0073] The following is further described in detail through specific implementation methods: Example

[0074] This embodiment provides a rockburst prediction method for hard rock in high geostress areas, which is applicable to the working conditions where the axial direction of the rock cave is parallel to the direction of the maximum principal stress and the rockburst is mainly controlled by the intermediate principal stress, and is applicable to high geostress areas and extremely high geostress areas. In my country, general rock mass engineering is considered to be a high geostress area with an initial geostress of 20-30 MPa.

[0075] A rockburst prediction method for hard rock in high ground stress areas, the specific steps are as follows:

[0076] A. Determine the scope of rock burst: Use geological survey methods and microseismic monitoring methods to assist in determining the scope of rock burst. In this embodiment, based on the work experience of engineers and the use of existing geological survey methods and microseismic monitoring methods, the location of rock burst can be assisted in predicting, thereby improving the accuracy of the prediction. Both geological survey methods and microseismic monitoring methods are existing technologies and will not be described in detail here.

[0077] B. Predicting rockburst location: rockburst prediction is performed on different parts of the rock mass within the determined rockburst range. In this embodiment, the rock mass cavern is divided into spandrel, upper haunch, lower haunch and arch foot;

[0078] In step B, the following rockburst predictions are performed for each location:

[0079] B11. Determine the initial stress σ1 of the rock mass and the uniaxial compressive strength R of the rock massc , uniaxial tensile strength of rock R t , calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v ,

[0080] B12. Predict the rockburst location based on the following criteria:

[0081] σ1≥0.15R c (Mechanical requirements)

[0082] R c ≥15R t (Brittleness requirement)

[0083] K v ≥0.55 (completeness requirement)

[0084] W et ≥2.0 (energy storage requirement),

[0085] When the predicted location satisfies the above four criteria at the same time, the location is set as the rockburst location.

[0086] C. Determine the rockburst level, specifically:

[0087] According to the predicted rockburst location in step B, the maximum tangential stress, rock cracking stress, and rock failure stress of different parts of the rock mass are calculated, and the rockburst level is determined according to the following criteria (see Table 1):

[0088] Table 1:

[0089]

[0090] σ max is the maximum tangential stress of the surrounding rock of the cavern; ci is the rock crack initiation stress; cd is the rock failure stress; K v is the rock mass integrity coefficient; GSI is the geological strength factor.

[0091] The GSI (Geological strength index) method was first proposed by E. Hoek et al. to evaluate rock mass quality and to achieve an effective combination with the Hoek-Brown empirical criterion. The GSI value of rock mass quality is qualitatively determined by the rock mass structure coefficient and the structural surface state coefficient.

[0092] After long-term research, people found that rockbursts generally only occur in hard brittle rocks, and the magnitude of the sum of the stress components (σ1+σ3) on the tunnel cross section is generally high. This study divides rockbursts into three types according to the rockburst breeding mechanism: strain-type rockburst, structural rockburst, and compound rockburst. The mechanism type of underground cavern rockburst is mostly strain-type rockburst, occasionally compound rockburst, and no structural rockburst.

[0093] Step D, checking the accuracy of the rockburst location predicted in step B:

[0094] The rock cave model is used to simulate the cave after excavation to obtain the location of the stress concentration point as a reference rockburst location; the location of the stress concentration point is the location with the largest deformation;

[0095] The reference rockburst location is compared with the predicted rockburst location to verify the accuracy of the predicted rockburst location.

[0096] When the coincidence rate between the reference rockburst position and the predicted rockburst position reaches a set value, it is judged that the predicted rockburst position has high accuracy;

[0097] If the coincidence rate between the reference rockburst position and the predicted rockburst position does not reach a set value, it is judged that the accuracy of the predicted rockburst position is low.

[0098] In this embodiment, Shuangjiangkou Hydropower Station is taken as an example for explanation. The specific modes of the main destruction of Shuangjiangkou Hydropower Station are plate-like rupture, sheet-like rupture, V-shaped rupture, and stress and structure coordination type destruction, and the surrounding rock destruction rules are: difference characteristics of the left and right banks (the left bank is mainly brittle destruction of high ground stress, and the right bank is mainly block falling and collapse controlled by the structural surface), circumferential unloading characteristics (unloading cracks are nearly parallel to the air-facing surface, and the annular caverns are developed), rock structure effects (surrounding rock destruction around faults, large and large structural surfaces and sections with relatively developed structural surfaces), cave direction effects (east-west, northwest and northeast caverns are more severely damaged than north-south caverns), cavern mutation effects (cavern turning convex surfaces and cavern intersections often suffer more severe damage), destruction location characteristics (the upstream side spandrels, upper side walls and downstream side arch feet, and lower side walls of the three north-south caverns of the water diversion and power generation system are more easily destroyed), and destruction time effects (due to the gradual deformation and destruction of the rock mass and the adjustment of stress as the excavation proceeds, secondary damage occurs after surrounding rock spraying).

[0099] Based on the mechanical properties of the rockburst rupture surface, we divide rockbursts into four categories: pressure-induced tensile fracture rockburst (type I), pressure-induced tensile fracture-bending rockburst (type II), pressure-induced tensile fracture-shear rockburst (type III), and pressure-induced tensile fracture-slip rockburst (type IV). The first three types are strain-type rockbursts, and the fourth type is a compound rockburst. Figure 1 .

[0100] K in step Bv The calculation method includes the following steps:

[0101] According to the mechanical properties of the rock burst rupture surface, the type of rock burst damage is determined, and the value of Kv is determined according to the type of rock burst damage;

[0102] When it is a strain-type rockburst, K v =1;

[0103] When it is a compound rockburst, K v It is the square of the ratio of the wave velocities of the rock mass and rock under the same confining pressure conditions.

[0104] Among the rockburst types, type I mainly occurs at the side wall, and types II and III mainly occur at the arch foot, the intersection of the cave, the turning part, and the lower part of the side wall. Type IV is related to the development location of the structural surface, and it develops at the side wall and arch foot. Figure 2 .

[0105] In this embodiment, when checking the accuracy of the rockburst position prediction, the location of the stress concentration point of the cavern after excavation is simulated in combination with the cavern model, where the deformation is large. Then, the accuracy of the rockburst position prediction is checked at the location corresponding to the rockburst occurrence. Combined with the judgment method of the above-mentioned steps B and C, the accuracy of rockburst prediction in high geostress areas and extremely high geostress areas can be improved.

[0106] This embodiment also provides a rockburst prediction system for hard rock in high geostress areas, including:

[0107] A rockburst range determination module is used to determine the range of rockburst in the rock mass;

[0108] The rockburst location prediction module is used to predict the rockburst location within the rockburst range;

[0109] The rockburst location prediction module includes:

[0110] The rock mass part division module is used to divide the rock mass into different parts within the determined rock burst range;

[0111] Parameter acquisition module, used to receive the initial stress σ of the rock mass at each location 1jia , uniaxial compressive strength of rock block R c , uniaxial tensile strength of rock R t ;

[0112] Calculation module, used to calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v ;

[0113] The prediction module is used to predict rockburst at each location in the rock mass location division module. For each location, when it satisfies σ1≥0.15R c , R c ≥15R t , K v ≥0.55,W et ≥2.0, the position is set as the rockburst position and the rockburst position is output;

[0114] The rockburst level determination module is used to calculate the maximum tangential stress, rock cracking stress and rock failure stress of the rockburst location according to the rockburst location predicted by the rockburst location prediction module, and determine the rockburst level according to the following judgment conditions:

[0115] If σ max / (K v σ cd )>1.0or(100σ max ) / (GSIσ cd )>1.0, the rock burst level is severe rock burst;

[0116] If σ max / (K v σ cd ) = 0.5~1.0 or (100σ max ) / (GSIσ cd ) = 0.5~1.0, the rock burst level is severe rock burst;

[0117] If σ max / (K v σ ci ) = 0.5~1.0 or (100σ max ) / (GSIσ ci ) = 0.5~1.0, the rock burst level is medium rock burst;

[0118] If σ max / (K v σ ci )<0.5or(100σ max ) / (GSIσ ci )<0.5, the rockburst level is slight rockburst;

[0119] σ max is the maximum tangential stress of the surrounding rock of the cavern; ci is the rock crack initiation stress; cd is the rock failure stress; K v is the rock mass integrity coefficient; GSI is the geological strength factor;

[0120] The simulation module is used to simulate the excavated cavern using the rock cavern model to obtain the location of the stress concentration point as a reference rockburst location;

[0121] A comparison module is used to compare the reference rockburst position with the predicted rockburst position, calculate the overlap rate between the reference rockburst position and the predicted rockburst position, and verify the prediction accuracy;

[0122] Output module, used to output prediction results.

[0123] When the overlap rate between the reference rockburst position and the predicted rockburst position reaches a set value, it is judged that the accuracy of the predicted rockburst position is high, and the predicted position is output as the rockburst position; if the overlap rate between the reference rockburst position and the predicted rockburst position does not reach the set value, it is judged that the accuracy of the predicted rockburst position is low, and the predicted position is output as not the rockburst position. When the predicted rockburst position is not very accurate, the microseismic monitoring method in the prior art can be combined to predict and correct the rockburst position again in actual applications.

[0124] In this embodiment, the coincidence rate of the reference rockburst position and the predicted rockburst position is mainly based on the elevation, vertical and horizontal pile number and area of ​​the reference rockburst position and the predicted rockburst position to judge the matching degree between the two. At the same time, the artificial experience of observing the damage situation is used to assist in judging whether the reference rockburst position is consistent with the predicted rockburst position, such as the damage depth, etc. In addition, the cross-sectional view of the reference rockburst position and the plan view of the predicted rockburst position can be compared.

[0125] In this embodiment, Shuangjiangkou Hydropower Station is taken as an example for explanation. The axes of the three major caverns of Shuangjiangkou Hydropower Station are parallel to the direction of the maximum principal stress, so the rock burst is mainly controlled by the intermediate principal stress. The maximum tangential stress is calculated by the elastic mechanics formula, and the ratio of it to the single extraction compressive strength of the rock is used to preliminarily judge the rock burst situation. However, since the geological conditions of each project are very complex, comprehensive factors need to be considered. This embodiment draws on the Gu-Tao criterion modified by Zhang Jingjian, starting from four aspects, namely mechanical requirements, brittleness requirements, integrity requirements and energy storage requirements, which can more accurately judge the rock burst location, and increase the criterion in this embodiment, which can effectively improve the accuracy of rock burst prediction.

[0126] The three caverns of the underground powerhouse of Shuangjiangkou Hydropower Station under construction have carried out macroscopic rockburst predictions in different parts of the middle guide tunnel, the first layer, the second layer, and the third layer. The rockburst prediction method is mainly the judgment method and geological survey method provided in this embodiment, supplemented by microseismic monitoring. After excavation and comparison with the prediction, it was found that the rockburst damage type, rockburst grade, and rockburst occurrence location are basically consistent.

[0127] Based on the criteria proposed in this embodiment, rock burst prediction is carried out for the three caverns of the main powerhouse, main transformer room and tailwater room, tailwater tunnel and other water diversion power generation system caverns. The prediction diagram is shown in Figure 3-12 , Figure 3-12 In the figure, the pile number position corresponding to the predicted rockburst position can be indicated.

[0128] Track the intensity of rockbursts in each chamber and compare them with the predicted results:

[0129] (1) The excavation of the first floor of the main powerhouse is expected to cause more serious damage to the surrounding rock of the upper spandrel and arch waist on the upstream side, especially near the road pile numbers K0-68~K0-00m, K0+30-50m and K0+140m, where there is a possibility of medium rock burst, and the dominant damage locations are the upper arch waist and spandrel. The damage of the downstream side expansion is expected to be mainly spalling and layer cracking, mainly occurring in the lower arch waist and arch foot. The upstream side of the powerhouse is expanded from K0-68.8 to K0+80m, and the downstream side is expanded from K0-68.8m to K0+120m. Judging from the damage of the expanded section, several medium rock bursts are within the predicted range, achieving accurate prediction ( Fig.13 ).

[0130] (2) It is expected that after the expansion of the two sides of the tailgate chamber I layer, the overall surrounding rock damage will be more serious than when the middle guide tunnel is opened, especially in the arch spandrel and upper waist of the road pile number K0+25m~K0-14.5m section. Medium-intensity rock bursts may occur. The downstream side is weaker than the middle guide tunnel, mainly with spalling and splitting. It is recommended to reinforce the three sections where large structural surfaces are developed, namely the K0+110m~120m fault, the K0-10m~K0-14.5m fault and the K0+35m~K0+50m structural surface, to prevent the occurrence of stress-structure coordinated control failure (Type IV). Up to now, the upstream and downstream sides of the tailgate chamber have been expanded from K0-14.8 to K0+120m. Judging from the damage of the expanded section, the medium rock bursts here are all within the predicted range, achieving accurate prediction. Fig.14 .

[0131] (3) The pile number range of the construction drawing of the 1# tailwater tunnel is Tail 1 (K0+163.481~K0+933.941). The right spandrel of the Tail 1 (K0+163.481~K0+563.481) section is predicted to be a strong rockburst area, the right spandrel of the Tail 1 (K0+563.481~K0+933.941) and the left wall foot of the Tail 1 (K0+163.481~K0+563.481) are predicted to be moderate rockburst areas, and the other areas are slight rockburst areas. Fig.15 .

[0132] Now the 1# tailwater tunnel is being excavated, with the pile number range from K0+220m to K0+380m. Judging from the damage in the expanded section, a strong rock burst occurred in the right shoulder area, which is all within the predicted range and has achieved accurate prediction.

[0133] This proposal summarizes a method for predicting rockbursts in high-stress areas, starting from the four aspects of mechanical requirements, brittleness requirements, integrity requirements and energy storage requirements, and considering the conditions for rockbursts to occur is relatively complete; after predicting rockbursts, it can be used to guide construction and excavation, which can effectively save costs and improve efficiency; in addition, for different levels of rockbursts, corresponding support measures can be prepared in advance to improve safety.

[0134] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A rockburst prediction method for hard rock in high geostress areas, characterized in that: The following steps are involved: A. Determine the scope of rock burst; B. Predict rockburst location: Within the determined rockburst range, the rock mass is divided into parts and rockburst prediction is performed on different parts of the rock mass; In step B, the following rockburst predictions are performed for each location: B11. Determine the initial stress σ1 of the rock mass and the uniaxial compressive strength R of the rock mass c , uniaxial tensile strength of rock R t , calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v , B12. Predict the rockburst location based on the following criteria: σ1 ≥ 0.15R c , R c ≥15R t , K v ≥0.55,W et ≥2.0; when the predicted location meets the above four criteria at the same time, the location is set as the rockburst location; The step C is to determine the rockburst level, which is as follows: According to the rockburst location predicted in step B, the maximum tangential stress of the rock mass, the rock cracking stress, and the rock failure stress are calculated for the rockburst location, and the rockburst level is determined according to the following criteria: If σ max / (K v σ cd )>1.0or(100σ max ) / (GSIσ cd )>1.0, the rock burst level is severe rock burst; If σ max / (K v σ cd ) = 0.5~1.0 or (100σ max ) / (GSIσ cd ) = 0.5~1.0, the rock burst level is severe rock burst; If σ max / (K v σ ci ) = 0.5~1.0 or (100σ max ) / (GSIσ ci ) = 0.5~1.0, the rock burst level is medium rock burst; If σ max / (K v σ ci )<0.5or(100σ max ) / (GSIσ ci )<0.5, the rockburst level is slight rockburst; σ max is the maximum tangential stress of the surrounding rock of the cavern; ci is the rock crack initiation stress; cd is the rock failure stress; K v is the rock mass integrity coefficient; GSI is the geological strength factor.

2. A rockburst prediction method for hard rock in high geostress areas according to claim 1, characterized in that: The method further includes step D, which verifies the accuracy of the rockburst location predicted in step B: The rock cave model is used to simulate the cave after excavation to obtain the location of stress concentration points as reference rockburst locations; The reference rockburst location is compared with the predicted rockburst location to verify the accuracy of the predicted rockburst location.

3. A rockburst prediction method for hard rock in high geostress areas according to claim 2, characterized in that: When the coincidence rate between the reference rockburst position and the predicted rockburst position reaches a set value, it is judged that the accuracy of the predicted rockburst position is high; If the coincidence rate between the reference rockburst position and the predicted rockburst position does not reach a set value, it is judged that the accuracy of the predicted rockburst position is low.

4. The rockburst prediction method for hard rock in high geostress areas according to claim 1, characterized in that: K in step B v The calculation method includes the following steps: According to the mechanical properties of the rock burst rupture surface, the type of rock burst damage is determined, and K is determined according to the type of rock burst damage. v The values ​​of , the rockburst destruction types include pressure-induced tensile fracture type rockburst, pressure-induced tensile fracture-bending type rockburst, pressure-induced tensile fracture-shear type rockburst, and pressure-induced tensile fracture-slip type rockburst, among which the first three types are strain-type rockbursts, and the fourth type is a compound rockburst; When it is a strain-type rockburst, K v =1; When it is a compound rockburst, K v It is the square of the ratio of the wave velocities of the rock mass and rock under the same confining pressure conditions.

5. The rockburst prediction method for hard rock in high geostress areas according to claim 1, characterized in that: It is applicable to the working conditions where the axial direction of the rock cavern is parallel to the direction of the maximum principal stress and the rockburst is mainly controlled by the intermediate principal stress.

6. The rockburst prediction method for hard rock in high geostress areas according to claim 1, characterized in that: Suitable for high ground stress areas and extremely high ground stress areas.

7. A rockburst prediction system for hard rock in high geostress areas, characterized in that: include: A rockburst range determination module is used to determine the range of rockburst in the rock mass; The rockburst location prediction module is used to predict the rockburst location within the rockburst range; The rockburst location prediction module includes: The rock mass part division module is used to divide the rock mass into different parts within the determined rock burst range; The parameter acquisition module is used to receive the initial stress σ1 of the rock mass at each part, the uniaxial compressive strength R of the rock mass c , uniaxial tensile strength of rock R t ; Calculation module, used to calculate the ratio of surrounding rock elastic strain energy to loss strain energy W et , rock mass integrity coefficient K v ; The prediction module is used to predict rockburst at each location in the rock mass location division module. For each location, when it satisfies σ1≥0.15R c , R c ≥15R t , K v ≥0.55,W et ≥2.0, the position is set as the rockburst position and the rockburst position is output; The rockburst level determination module is used to calculate the maximum tangential stress, rock cracking stress and rock failure stress of the rockburst location according to the rockburst location predicted by the rockburst location prediction module, and determine the rockburst level according to the following judgment conditions: If σ max / (K v σ cd )>1.0or(100σ max ) / (GSIσ cd )>1.0, the rock burst level is severe rock burst; If σ max / (K v σ cd ) = 0.5~1.0 or (100σ max ) / (GSIσ cd ) = 0.5~1.0, the rock burst level is severe rock burst; If σ max / (K v σ ci ) = 0.5~1.0 or (100σ max ) / (GSIσ ci ) = 0.5~1.0, the rock burst level is medium rock burst; If σ max / (K v σ ci )<0.5or(100σ max ) / (GSIσ ci )<0.5, the rockburst level is slight rockburst; σ max is the maximum tangential stress of the surrounding rock of the cavern; ci is the rock crack initiation stress; cd is the rock failure stress; K v is the rock mass integrity coefficient; GSI is the geological strength factor.

8. The rockburst prediction system for hard rock in high geostress areas according to claim 7, characterized in that: Also includes: The simulation module is used to simulate the excavated cavern using the rock cavern model to obtain the location of the stress concentration point as a reference rockburst location; A comparison module is used to compare the reference rockburst position with the predicted rockburst position, calculate the overlap rate between the reference rockburst position and the predicted rockburst position, and verify the prediction accuracy; Output module, used to output prediction results.

9. A rockburst prediction system for hard rock in high geostress areas according to claim 8, characterized in that: When the overlap rate between the reference rockburst position and the predicted rockburst position reaches a set value, the accuracy of the predicted rockburst position is judged to be high, and the predicted position is output as the rockburst position; if the overlap rate between the reference rockburst position and the predicted rockburst position does not reach the set value, the accuracy of the predicted rockburst position is judged to be low, and the predicted position is output as not the rockburst position.

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