Failure Characteristics Of Single-fracture Limestone Under Hydro Mechanical Coupling And Analysis Of Insidious Fault Water Inrush

Fractured rock mass is a kind of complex medium widely existed in nature.Its internal defects such as joints and micro-cracks bring safety hazards to rock underground engineering construction,and hydraulic coupling has mechanical properties and engineering problems.Relevance is crucial for the long-term stability of various types of rock engineering operations.The scale of rock underground engineering is expanding continuously.The engineering problems such as seepage,rush and sudden in water engineering are becoming more and more prominent.It is obvious.Therefore,it is of great practical significance to study the hydraulic coupling crack propagation law of rock mass under complex conditions.Based on the previous research results,this paper uses the indoor test,theoretical analysis and other research methods to carry out the triaxial test on the hydraulic characteristics of single-fracture limestone by conducting single and triaxial compression tests on intact limestone,and the hydraulic force on single-fracture limestone.The characteristics of the study are more comprehensive,the main research contents of this paper are as follows:(1)Through the triaxial compression mechanical properties test of intact limestone,the basic parameters such as triaxial strength and shear strength index c,?,Poisson's ratio?and deformation modulus E₅₀ of limestone are obtained.The influence of confining pressure on the mechanical properties of limestone.(2)Using the MTS815 rock multi-functional electro-hydraulic servo test machine,the hydraulic coupling triaxial compression test was carried out on the single-fracture limestone,and the stress-strain of the fractured limestone under hydraulic coupling was obtained under the condition of confining pressure and pore pressure.The curve shows four kinds of peak curve types with the change of the inclination angle of the crack.When the fracture angle is15°,the stress-strain curve mainly appears as the front high and low bimodal,and the crack-angle curve is 45°.It is presented as a front low and high bimodal,single peak residual type,and the stress-strain curve is mainly a conventional single peak type when the fracture angle is 75°.Under the same pore pressure and confining pressure,the fractured rock samples under hydraulic coupling also change with the change of the crack angle.The fracture strength of the fractured rock sample with the crack angle of 75°is the highest,15°.Second,45°is the smallest.(3)Carry out the theoretical study on the rock-wing crack propagation model of hydraulic coupling,and modify the existing wing crack model by the hydraulic coupling rock wing crack propagation model,and use the elastic mechanics theory to establish the finite element model.The analysis results of the hydraulic coupling rock wing crack propagation model and the finite element results are validated,and the residual square sum is introduced to judge the wing crack model under the optimal hydraulic coupling.(4)Applying the theoretical analysis results to the project of insidious fault water inrush in coal mine floor,combined with the results of theoretical analysis,the fracture mechanics foundation of insidious fault water inrush,the mechanical model of insidious fault water inrush,and the mechanical judgment of insidious fault water inrush.According to the analysis,a prediction method for insidious fault water inrush is proposed.