CN-121980749-A - Method for determining maximum attenuation coefficient of shear strength of rock mass in coal mine side slope fire area

Abstract

A method for determining a rock mass shear strength maximum attenuation coefficient of a coal mine side slope fire zone belongs to the technical field of geotechnical engineering side slope stability evaluation and safety control. The method provides a quantification index of 'maximum attenuation coefficient', establishes a complete system from uncertainty analysis to safety judgment, and realizes the span from experience judgment to scientific quantitative evaluation. The 'two-stage analysis' framework skillfully solves the multi-factor coupling problem of water level and intensity attenuation, and ensures the scientificity of the result by optimizing the logic of the water level and then determining the intensity limit. The method combines the statistical completeness of Monte Carlo sampling and the high efficiency of a response surface method, and greatly improves the calculation efficiency while ensuring the accuracy. And a final output result provides a direct and reliable basis for slope drainage design and safety early warning, and the engineering risk management and control capability is remarkably improved.

Inventors

• LIU GAN
• MENG SHANG
• ZHANG KAI
• MA KE
• LI HONGBO
• ZHAO ZHIQIANG
• WANG KEKE
• HUANG HUASEN
• LIU JIANING
• LI XIAOJUN

Assignees

• 中煤科工集团沈阳设计研究院有限公司

Dates

Publication Date

20260505

Application Date

20251217

Claims (6)

1. 1. The method for determining the maximum attenuation coefficient of the shear strength of the rock mass in the fire zone of the coal mine side slope is characterized by comprising the following steps of establishing a numerical model rich in the coal mine side slope in the fire zone, and designing a plurality of underground water level heights and the shear strength attenuation coefficients of the rock mass in the fire zone; Regarding the height of each underground water level, taking the cohesive force c and the internal friction angle phi of the rock mass in the fire area as random variables, generating a plurality of parameter samples by using a Monte Carlo sampling method, calculating the safety coefficient corresponding to each parameter sample by using a response surface method, and calculating the failure probability based on the number of samples with the safety coefficient smaller than 1 to obtain a relation curve of the failure probability and the height of the underground water level; Determining the optimal ground water level height from a relation curve of the failure probability and the ground water level height according to the expected failure probability; Under the optimal underground water level height, calculating the safety coefficient of the coal mine side slope by using a limit balance method for the shear strength attenuation coefficient of the rock mass in each fire zone, and obtaining a relation curve of the safety coefficient and the shear strength attenuation coefficient; and determining the maximum attenuation coefficient of the shear strength of the rock mass in the coal mine side slope burning area from the relation curve of the safety coefficient and the attenuation coefficient of the shear strength according to the minimum allowable safety coefficient.
2. 2. The method of claim 1, wherein the plurality of ground water level height values are designed in such a way that a plurality of water level height values are selected as design values in the fluctuation range in an equally-spaced or non-equally-spaced manner based on a historical highest water level, an annual average water level and a historical lowest water level of the ground water level of the area where the slope is provided by the engineering investigation data.
3. 3. The method of claim 1, wherein the shear strength attenuation coefficients of the plurality of burned-out zone rock masses are designed in such a way that, starting from 1.0, values are selected downwards at intervals of not more than 0.05 until the minimum value of the attenuation coefficient is selected such that the calculated safety coefficient is below the allowable minimum safety coefficient.
4. 4. The method of claim 1, wherein the probability of failure Pf is calculated by the formula: Pf=m/M, wherein M is the number of samples with a safety factor less than 1, and M is the total number of samples.
5. 5. The method of claim 1, wherein the optimal ground water level height corresponds to a water level height at a desired failure probability.
6. 6. A method according to claim 1, wherein the safety factor versus shear strength attenuation factor is obtained by plotting minimum safety factors for different attenuation factors.

Description

Method for determining maximum attenuation coefficient of shear strength of rock mass in coal mine side slope fire area Technical Field The invention belongs to the technical field of geotechnical engineering slope stability evaluation and safety control, and particularly relates to a method for determining a maximum attenuation coefficient of rock shear strength in a coal mine slope burning zone. Background In the mining activities of open pit coal mines, slope stability is a core issue concerning production safety and economic benefits. Among these, the fire zone formed by spontaneous combustion of coal seams is a highly detrimental geological factor. The internal structure of the rock body of the area is obviously changed due to high-temperature baking and chemical change, and the original joints develop, so that rock materials tend to be loose and broken, and the integrity is seriously damaged. The deterioration of the mechanical properties of the rock mass is concentrated and reflected in the large attenuation of the shear strength, so that the anti-slip capability of the side slope is directly weakened, potential hazards of landslide disasters are formed, and the greater the attenuation coefficient of the shear strength of the rock mass in a fire area is, the lower the stability of the side slope of the coal mine is likely to be. It is worth noting that when the groundwater level is in a higher state, the negative impact of the decay of the shear strength of the fire zone on the slope stability is greatly amplified. High water level means that the pore water pressure in the side slope rock-soil mass increases significantly. According to the effective stress principle in the rock-soil mechanics, the effective normal stress among rock mass particles on the sliding surface can be counteracted by the higher pore water pressure, so that the friction resistance of the surface, namely the anti-sliding force, is obviously reduced. Meanwhile, the softening and corrosion effects of the underground water on the rock mass jointly increase the sliding trend of the side slope. Therefore, under the coupling effect of the two adverse conditions of "fire zone strength is seriously deteriorated" and "high pore water pressure", the stable state of the side slope is drastically deteriorated. In view of the fact that the influence research of the attenuation of the shear strength of the rock mass in the fire zone on the stability of the coal mine slope is not comprehensive enough, the determination of the maximum attenuation coefficient of the shear strength of the rock mass in the fire zone on the coal mine slope still faces challenges, and therefore a new method for determining the maximum attenuation coefficient of the shear strength of the rock mass in the fire zone on the coal mine slope is needed. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a method for determining the maximum attenuation coefficient of the shear strength of the rock mass in the coal mine side slope burning area. The invention adopts the technical scheme that the method for determining the maximum attenuation coefficient of the shear strength of the rock mass in the coal mine side slope burning area is technically characterized by comprising the following steps: establishing a numerical model rich in coal mine slopes in a fire zone, and designing a plurality of underground water level heights and a plurality of rock mass shear strength attenuation coefficients in the fire zone; Regarding each underground water level height, taking the cohesive force c and the internal friction angle phi of the rock mass in the fire area as random variables, generating a plurality of parameter samples by using a Monte Carlo sampling method, calculating a safety coefficient corresponding to each parameter sample by using a response surface method, and calculating failure probability based on the number of samples with the safety coefficient smaller than 1 to obtain a relation curve of the failure probability and the underground water level height; Under the optimal underground water level height, calculating the safety coefficient of the coal mine side slope by using a limit balance method for the shear strength attenuation coefficient of the rock mass in each fire zone, and obtaining a relation curve of the safety coefficient and the shear strength attenuation coefficient; and determining the maximum attenuation coefficient of the shear strength of the rock mass in the coal mine side slope burning area from the relation curve of the safety coefficient and the attenuation coefficient of the shear strength according to the minimum allowable safety coefficient. Furthermore, the design mode of the plurality of ground water level height values is that a plurality of water level height values are selected as design values in the fluctuation range in a mode of equal intervals or unequal intervals based on the histor