Study On Failure Mechanism Of Fractured Rock Mass Induced By Mining And Its Engineering Application

Groundwater may flow into the goaf through various hydraulic channels during the coal mining process,which leads to water-inrush accidents,resulting in huge loss of lives and properties.Mining will induce the fracture of the surrounding rock of the goaf,and the interconnected fracture network constitutes the main channel for groundwater.Therefore,it is of great theoretical and practical significance to establish a prediction model for mining induced failure range from the perspective of rock damage and fracture mechanism.Chosing huaibei coalfield as a typical research object,this paper mainly explores the damage and fracture mechanism of surrounding rock in coal mining from the following aspects.Firstly,aiming at the limestone strata widely distributed in Huaibei coalfield,the evolution process of rock microfractures under chemical corrosion is simulated by coupling the fracture field and the concentration field,and the deterioration effect of rock mechanical properties under chemical damage is quantified by the fractal dimension.Secondly,Considering the existence of native fractures,a rock fracture criterion is derived.Using this fracture criterion,the development of water-conducting fractured zone in 839 working face of Qingdong coal mine is simulated.Thirdly,to explore the influence of spatial variability of rock strength on the development of water-conducting fractured zone,the uniaxial tensile strength,cohesion,internal friction angle and softening coefficient of overlying strata are regarded as random variables.The performance function of each particle in the overlying strata is derived and the failure probability of each particle is calculated.The model is applied in a typical working face of Huaibei coal field for verification.Through theoretical and simulation research,the main conclusions are as follows.The expansion rate of fracture width slows down with time and there is a linear relationship between the fractal dimension and the damage variable.The prediction of limestone strength deterioration by fractal theory is consistent with the experimental results.When considering the native fractures,the height of the water-conducting fractured zone reaches 92.5 m.Compared with the traditional numerical simulation,the key stratum method and empirical formula method,the result is closer to the field measurement results.The particle failure probability model can reflect the influence of local low strength area of overburden on the range of water-conducting fractured zone into the failure probability,and then predict the location of water-inrush.