A method for predicting the disaster level of large deformation of surrounding rocks in highland temperate zones

Abstract

The present invention discloses a method for predicting the disaster grade of large deformation of surrounding rock in high geothermal zones, including: S1: Obtain the maximum horizontal principal ground stress and the vertical stress; S2: Obtain the uniaxial saturated compressive strength, viscosity coefficient and creep time of the surrounding rock at normal temperature; S3: Obtain the reduced compressive strength under the influence of temperature according to the uniaxial saturated compressive strength, viscosity coefficient and creep time of the surrounding rock at normal temperature; S4: Obtain the surrounding rock heat damage coefficient according to the uniaxial saturated compressive strength of the surrounding rock at normal temperature, the surrounding rock quality index, the number of joint sets per unit volume of rock mass and the maximum horizontal principal ground stress; S5: Obtain the high geothermal influence factor considering the influence of high geothermal on the large deformation of the surrounding rock according to the maximum horizontal principal ground stress and the vertical stress; S6: Obtain the deformation coefficient according to the maximum horizontal principal ground stress, the high geothermal influence factor and the reduced compressive strength under the influence of temperature; S7: Determine the grade of large deformation of the surrounding rock in high geothermal zones according to the deformation coefficient and the surrounding rock heat damage coefficient.

Description

Technical Field

[0001] The present invention relates to the technical field of geological exploration, and particularly relates to a method for predicting the disaster level of large deformation of surrounding rock in high geothermal zones. Background Art

[0002] Disaster prediction and classification is the most important content in the study of large deformation. As a serious geological disaster, the large deformation of surrounding rock has a serious impact on tunnel engineering construction. Although domestic and foreign scholars have done a lot of exploration and research work, due to the immaturity of the large deformation theory and the complexity of the on-site geological rock mass conditions, the prediction of large deformation disasters is still the weakest link in this field. At present, the discriminant method for the large deformation classification of soft rock in tunnels in high ground stress areas given in the "Code for Design of Railway Tunnels" (2016 edition) is adopted in China, using the ratio of surrounding rock strength to stress (the ratio of surrounding rock strength to the maximum in-situ stress) and the deformation characteristics of the surrounding rock. Among them, the surrounding rock strength is a comprehensive index, which is related to the surrounding rock strength, the cohesion and internal friction angle of the rock mass, as well as the degree of joint fissure development, groundwater, etc. It is very difficult to obtain accurate surrounding rock strength on site.

[0003] The above discriminant criteria for large deformation can generally only judge the deformation of the surrounding rock under general conditions. However, with the vigorous development of underground projects such as water conservancy and transportation, the buried depth of the tunnels built at home and abroad is getting larger and larger. As the buried depth increases, the geological environment of the underground rock mass becomes more complex, often accompanied by high

[0004] geothermal temperature, high seepage water pressure and other complex geological conditions. Obviously, it is difficult to realize the prediction of large deformation of surrounding rock in high geothermal environments using traditional discriminant methods. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for predicting the disaster level of large deformation of surrounding rock in high geothermal zones, so as to solve the problem that the existing method for judging the surrounding rock level cannot realize the prediction of the surrounding rock level in high geothermal zones.

[0006] The technical solution for the present invention to solve the above technical problems is as follows:

[0007] The present invention provides a method for predicting the disaster level of large deformation of surrounding rock in high geothermal zones, and the method for predicting the disaster level of large deformation of surrounding rock in high geothermal zones includes:

[0008] S1: Conduct in-situ stress tests on the large deformation of the surrounding rock in high geothermal zones, and obtain the maximum horizontal principal in-situ stress and vertical stress;

[0009] S2: Obtain the uniaxial saturated compressive strength, viscosity coefficient and creep time of the surrounding rock at normal temperature;

[0010] S3: Obtain the reduced compressive strength under the influence of temperature according to the uniaxial saturated compressive strength of surrounding rock at normal temperature, the viscosity coefficient, and the creep time, considering the influence of high geotemperature on the strength of surrounding rock;

[0011] S4: Obtain the surrounding rock heat damage coefficient according to the uniaxial saturated compressive strength of surrounding rock at normal temperature, the surrounding rock quality index, the number of joint sets per unit volume of rock mass, and the maximum horizontal principal in-situ stress;

[0012] S5: Obtain the high geotemperature influence factor according to the maximum horizontal principal in-situ stress and the vertical stress, considering the influence of high geotemperature on large deformation of surrounding rock;

[0013] S6: Obtain the deformation coefficient according to the maximum horizontal principal in-situ stress, the high geotemperature influence factor, and the reduced compressive strength under the influence of temperature;

[0014] S7: Determine the grade of large deformation of surrounding rock in high geotemperature zones according to the deformation coefficient and the surrounding rock heat damage coefficient.

[0015] Optionally, in step S3, the reduced compressive strength R c 1 is:

[0016]

[0017] where R c is the uniaxial saturated compressive strength of surrounding rock at normal temperature, σ s is the yield strength of surrounding rock, σ0 is the creep stress of surrounding rock, α is the coefficient of thermal expansion, E1 is the viscoelastic modulus, E is the elastic modulus, T is the geotemperature, η is the viscosity coefficient, and t is the creep time.

[0018] Optionally, in step S4, the surrounding rock heat damage coefficient γ is:

[0019]

[0020] where R c is the uniaxial saturated compressive strength of surrounding rock at normal temperature, σ max is the maximum horizontal principal in-situ stress, J n is the number of joint sets per unit volume of rock mass, and RQD is the surrounding rock quality index.

[0021] Optionally, in step S5, the high geotemperature influence factor S is:

[0022]

[0023] where λ 20 is the thermal conductivity of surrounding rock at 20 degrees, T is the geotemperature, κ is the linear expansion coefficient of surrounding rock, e is the porosity of surrounding rock; σ maxis the maximum horizontal principal stress; σ v is the vertical stress, and α is the coefficient of thermal expansion.

[0024] Optionally, in the step S6, the deformation coefficient D is:

[0025]

[0026] wherein, R c 1 is the reduced compressive strength under the influence of temperature, S is the high geothermal influence factor, and σ max is the maximum horizontal principal stress.

[0027] Optionally, when the geothermal temperature is greater than 28°C, the geothermal temperature is determined as a high geothermal temperature.

[0028] The present invention has the following beneficial effects:

[0029] 1. The relevant parameters obtained in this solution are all relatively easy to obtain, greatly reducing the workload. For complex geological conditions, compared with the existing large deformation disaster prediction methods, this solution can predict large deformation more quickly and is more applicable to the prediction of large deformation under high geothermal conditions.

[0030] 2. When predicting the large deformation grade of surrounding rock, this solution comprehensively considers the complex geological conditions of surrounding rock in high geothermal areas, and effectively predicts and classifies the large deformation disasters of surrounding rock in high geothermal areas from three aspects: the influence of high temperature on the strength of surrounding rock, the high geothermal disasters caused by the quality of surrounding rock, and the influence of high geothermal on the deformation of surrounding rock. Through this method, this solution obtains a relatively accurate deformation grade to ensure accurate support strategies are collected during the subsequent optimization of tunnel surrounding rock support, better control deformation, improve construction safety and efficiency, and ensure the stability of the tunnel at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flowchart of the method for predicting the large deformation disaster grade of surrounding rock in high geothermal areas of the present invention. DETAILED DESCRIPTION

[0032] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0033] Embodiment

[0034] The present invention provides a method for predicting the large deformation disaster grade of surrounding rock in high geothermal areas. Referring to Figure 1 as shown, the method for predicting the large deformation disaster grade of surrounding rock in high geothermal areas includes:

[0035] S1: Conduct in-situ stress tests on the large deformation of surrounding rock in high geothermal areas and obtain the maximum horizontal principal in-situ stress and vertical stress;

[0036] Since the present invention is directed to the large deformation of the surrounding rock in the highland temperate zone, when implementing the present invention, it is necessary to detect the temperature of the surrounding rock at the predicted large deformation, that is, to measure the ground temperature T. When T is greater than 28 degrees Celsius, it is determined that the large deformation is in the highland temperate zone, and then the following specific methods are carried out.

[0037] And in the present invention, the maximum horizontal principal in-situ stress and the vertical force are obtained by in-situ stress testing at the construction site.

[0038] S2: Obtain the uniaxial saturated compressive strength, viscosity coefficient, and creep time of the surrounding rock at normal temperature;

[0039] Here, parameters such as the uniaxial saturated compressive strength, viscosity coefficient, and creep time of the surrounding rock at normal temperature are measured according to laboratory tests.

[0040] S3: According to the uniaxial saturated compressive strength, viscosity coefficient, and creep time of the surrounding rock at normal temperature, considering the influence of high ground temperature on the strength of the surrounding rock, obtain the reduced compressive strength under the influence of temperature;

[0041] Specifically, the reduced compressive strength R under the influence of temperature c 1 is:

[0042]

[0043] wherein, R c is the uniaxial saturated compressive strength of the surrounding rock at normal temperature, σ s is the yield strength of the surrounding rock, σ0 is the creep stress of the surrounding rock, α is the thermal expansion coefficient, E1 is the viscoelastic modulus, E is the elastic modulus, T is the ground temperature, η is the viscosity coefficient, and t is the creep time.

[0044] The present invention predicts the influence of high temperature on the long-term strength of the surrounding rock. Since it is difficult to obtain the long-term strength of the surrounding rock in the highland temperate zone by artificial methods, a reduction formula is adopted, thereby reducing the labor intensity of manual work, and the obtained long-term strength also has high accuracy.

[0045] S4: According to the uniaxial saturated compressive strength of the surrounding rock at normal temperature, the surrounding rock quality index, the number of joint groups per unit volume of rock mass, and the maximum horizontal principal in-situ stress, obtain the surrounding rock heat damage coefficient;

[0046] Specifically, the surrounding rock heat damage coefficient γ is:

[0047]

[0048] wherein, R c is the uniaxial saturated compressive strength of the surrounding rock at normal temperature, σ max is the maximum horizontal principal in-situ stress, J n$J$ is the number of joint sets per unit volume of rock mass, and the specific values are shown in Table 1 below. $RQD$ is the surrounding rock quality index.

[0049] Table 1 Number of joint sets $J$ per unit volume of rock mass n

[0050]

[0051] In the present invention, in order to ensure that the surrounding rock quality index can more accurately reflect the influence on high geothermal large deformation disasters, a surrounding rock quality heat damage factor is introduced. The larger the heat damage factor, the worse the surrounding rock quality, and the more serious the high geothermal disaster is triggered.

[0052] S5: According to the maximum horizontal principal ground stress and the vertical stress, considering the influence of high geothermal on the large deformation of the surrounding rock, a high geothermal influence factor is obtained;

[0053] Specifically, the high geothermal influence factor $S$ is:

[0054]

[0055] where $\lambda$ 20 is the thermal conductivity of the surrounding rock at 20 degrees, $T$ is the geothermal temperature, $\kappa$ is the linear expansion coefficient of the surrounding rock, $e$ is the porosity of the surrounding rock; $\sigma$ max is the maximum horizontal principal stress; $\sigma$ v is the vertical stress, and $\alpha$ is the thermal expansion coefficient.

[0056] The high geothermal influence factor $S$ represents the influence of temperature on the deformation of the surrounding rock. The higher the temperature of the surrounding rock, that is, the larger the high geothermal influence factor, the greater the deformation.

[0057] S6: According to the maximum horizontal principal ground stress, the high geothermal influence factor and the reduced compressive strength under the influence of temperature, a deformation coefficient is obtained;

[0058] The deformation coefficient $D$ is:

[0059]

[0060] where $R$ c 1 is the reduced compressive strength under the influence of temperature, $S$ is the high geothermal influence factor, $\sigma$ max is the maximum horizontal principal stress.

[0061] S7: According to the deformation coefficient and the surrounding rock heat damage coefficient, the grade of large deformation of the surrounding rock in the high geothermal zone is determined. See Table 2 for details:

[0062] Table 2 Classification of large deformation of the surrounding rock in the high geothermal zone

[0063]

[0064]

[0065] The present invention has the following beneficial effects:

[0066] 1. The relevant parameters obtained by this solution are all relatively easy to obtain, greatly reducing the workload. For complex geological conditions, compared with the existing large deformation disaster prediction methods, this solution can predict large deformation more quickly and is more applicable to the prediction of large deformation under high temperature and temperate conditions.

[0067] 2. When predicting the large deformation grade of surrounding rock, this solution comprehensively considers the complex geological conditions of surrounding rock in high temperature and temperate zones. From three aspects: the influence of high temperature on the strength of surrounding rock, the high temperature disaster caused by the quality of surrounding rock, and the influence of high temperature on the deformation of surrounding rock, it effectively predicts and classifies the large deformation disaster of surrounding rock in high temperature and temperate zones. Through this method, this solution obtains a relatively accurate deformation grade to ensure accurate support strategies are collected during the subsequent optimization of tunnel surrounding rock support, better control deformation, improve construction safety and efficiency, and ensure the stability of the tunnel at the same time.

[0068] Embodiment 2

[0069] 1. Select a high temperature zone area with complex geological conditions and serious heat damage, and conduct a preliminary judgment on the surrounding rock at the place where large deformation is predicted to occur. The measured ground temperature T = 45°C, which is in the high temperature and temperate zone and can be applied to the present invention.

[0070] 2. Conduct in-situ ground stress tests and obtain the maximum horizontal principal stress σ max and the vertical stress σ v , and according to the measured data, the specific parameters are as follows: σ max = 10.3 MPa, σ v = 6.3 MPa.

[0071] 3. Select the surrounding rock at the place where large deformation is predicted in the high temperature and temperate zone and conduct laboratory tests to measure the uniaxial compressive strength R c = 10.1 MPa of the surrounding rock, and parameters such as the viscosity coefficient η and creep time t obtained from the isothermal creep test. According to the rheological properties of the surrounding rock at high temperature, the long-term strength of the surrounding rock is reduced using the following formula:

[0072]

[0073] According to the exploration data, the surrounding rock in this high temperature and temperate zone is mainly soft rock. Therefore, the rheological H-K model is used to conduct an isothermal creep test. According to the creep test results, creep model and equation, the following parameters are obtained: the uniaxial compressive strength R c = 10.1 MPa, the yield strength σ s= 6.73 MPa, creep stress σ0 = 4 MPa, viscoelastic modulus E1 = 3380 MPa, elastic modulus E = 2000 MPa, viscosity coefficient η = 0.6×10 13 MPa, thermal expansion coefficient α = 8.6e-6 ℃ -1 , as t→∞, the reduced long-term strength R c 1 = 5.90 MPa.

[0074] 4. According to the exploration data, further combined with the uniaxial compressive strength R c = 10.1 MPa, the surrounding rock quality index RQD = 15, the number of joint sets per unit volume of rock mass J n = 20, the maximum horizontal principal stress σ max = 10.3 MPa. Thus, the surrounding rock heat damage factor γ = 75.3 is determined. According to Table 2, it is preliminarily judged as grade I large deformation.

[0075] 5. Calculate the geothermal influence factor S. From the above steps and known parameters, the uniaxial compressive strength R of the surrounding rock c = 10.1 MPa, which is less than 15 MPa. Therefore, the high geothermal influence factor is calculated, and the obtained parameters are as follows: λ 20 = 2.5 W / (m·℃), T = 45℃, the linear expansion coefficient κ of the surrounding rock = 7.1e-4, the porosity e of the surrounding rock = 0.55, the maximum horizontal principal stress σ max = 10.3 MPa, the vertical stress σ v = 6.3 Mpa, and S = 1.158 is obtained.

[0076] 6. According to the obtained reduced strength of the surrounding rock, the maximum horizontal principal stress, and the high geothermal influence factor, combined with the formula, the large deformation is predicted and graded, and the deformation coefficient D = 0.49 is obtained.

[0077] 7. According to Table 2, considering the two indicators of the surrounding rock heat damage coefficient and the deformation coefficient comprehensively, it is concluded that the surrounding rock belongs to grade I large deformation, and the relative deformation degree is greater than 1% and less than or equal to 2%. According to the quantitative prediction analysis of large deformation in high geothermal zones, large deformation is proposed, and corresponding support measures should be taken.

[0078] In summary, the method for predicting the disaster level of large deformation of surrounding rock in high geothermal zones in the present case comprehensively considers the complex geological conditions of surrounding rock in high geothermal zones, and effectively predicts and grades the large deformation disaster of surrounding rock in high geothermal zones from three aspects: the influence of high temperature on the strength of surrounding rock, the high geothermal disaster caused by the quality of surrounding rock, and the influence of high geothermal on the deformation of surrounding rock. It is applicable to the grade prediction of large deformation of most surrounding rock in high geothermal zones, with a clear applicable object, and relatively accurate deformation grades can be obtained through this method.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for predicting the disaster level of large deformation of surrounding rock in highland temperate zones, characterized in that, The method for predicting the disaster level of large deformation of surrounding rock in high-temperature temperate zones includes: S1: Conduct in-situ stress tests on the large deformation of surrounding rock in high-temperature temperate zones, and obtain the maximum horizontal principal in-situ stress and vertical stress; S2: Obtain the uniaxial saturated compressive strength, viscosity coefficient, and creep time of the surrounding rock at normal temperature; S3: Considering the influence of high ground temperature on the strength of the surrounding rock, obtain the reduced compressive strength under temperature influence based on the uniaxial saturated compressive strength, viscosity coefficient, and creep time of the surrounding rock at normal temperature; S4: Obtain the surrounding rock heat damage coefficient based on the uniaxial saturated compressive strength of the surrounding rock at normal temperature, the surrounding rock quality index, the number of joint sets per unit volume of rock mass, and the maximum horizontal principal in-situ stress; S5: Considering the influence of high ground temperature on the large deformation of the surrounding rock, obtain the high ground temperature influence factor based on the maximum horizontal principal in-situ stress and the vertical stress; S6: Obtain the deformation coefficient based on the maximum horizontal principal in-situ stress, the high ground temperature influence factor, and the reduced compressive strength under temperature influence; S7: Determine the level of large deformation of the surrounding rock in high-temperature temperate zones based on the deformation coefficient and the surrounding rock heat damage coefficient.

2. The large deformation disaster level prediction method for highland temperate surrounding rock according to claim 1, characterized in that In the step S3, the compressive strength R is reduced under the influence of the temperature c 1 is as follows: Among them, R c is the uniaxial saturated compressive strength of surrounding rock at normal temperature, σ s is the yield strength of surrounding rock, σ0 is the creep stress of surrounding rock, α is the thermal expansion coefficient, E1 is the viscoelastic modulus, E is the elastic modulus, T is the geothermal temperature, η is the viscosity coefficient, and t is the creep time.

3. The method for predicting the disaster level of large deformation of surrounding rock in highland temperate zone according to claim 1, characterized in that, In the step S4, the surrounding rock heat damage coefficient γ is: Among them, R c is the uniaxial saturated compressive strength of the surrounding rock at normal temperature, σ max is the maximum horizontal principal in-situ stress, J n is the number of joint sets per unit volume of rock mass, and RQD is the surrounding rock mass quality index.

4. The method for predicting the disaster level of large deformation of surrounding rock in highland temperate zones according to claim 1, wherein, In the step S5, the high ground temperature influence factor S is: where λ 20 is the thermal conductivity of the surrounding rock at 20 degrees, T is the geothermal temperature, κ is the linear expansion coefficient of the surrounding rock, and e is the porosity of the surrounding rock; σ max is the maximum horizontal principal stress; σ v is the vertical stress, and α is the thermal expansion coefficient.

5. The method for predicting the disaster level of large deformation of surrounding rocks in highland temperate zones according to claim 1, characterized in that In the step S6, the deformation coefficient D is: Among them, R c 1 is the reduced compressive strength under the influence of temperature, S is the high geothermal influence factor, and σ max is the maximum horizontal principal stress.

6. The method for predicting the disaster level of large deformation of surrounding rocks in highland temperate zones according to any one of claims 1-5, characterized in that, When the ground temperature is greater than 28°C, determine the ground temperature as high ground temperature.

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