Mechanism And Application Of The Ground Subsidence Of Soft Rock

This paper, taking the ground subsidence caused by mine mining with the soft rock overburden face as the research background, carried out in-depth and detailed study on the mechanism of ground subsidence with a comprehensive research method including, similar material simulation experiment, numerical simulation, as well as field measurements theoretical analysis and practical example.The research mainly includes the following 5 parts.(1) The characteristics of the ground subsidence in typical soft rock mine are analyzed according to the observation data of ground movement.(2) Besides the mechanism of ground subsidence, the paper, based on similar material simulation experiment, also studies the relationship between ground subsidence space and mining space.(3) The paper finds out the effect of different mechanical parameters of rock mass on the ground subsidence.(4)Based on elastic beam theory and stochastic medium theory, the prediction model is set up;(5) The calculation method of prediction parameters is found out according to the rule of space equivalent.Major findings and suggestions are as followings.(1) The characteristics of the ground subsidence of soft rock shows that the subsidence coefficient q is much bigger, the boundary of ground movement basin is in much slower convergence, sinking speed and deformation values are much bigger during mining.(2) According to the result of simulation experiment of similar material, the overlying strata will present the flexure subsidence of simply supported beam when roof is not caving. While in the roof fall behind, the broken roof will form a supporting role in "masonry beam" structure, it continuously makes the mining space be converted to ground subsidence space under the support of the masonry beam.(3)Similar material experiment and theoretical analysis show that, the roof is more easy bending and sinking in the condition of soft rock, and makes the falling space decrease, then the height of the caving zone is reduced. Also because it is not easy to form the separation cracks or will soon be closed in overburden during the mining process, the mining space is converted fully to the ground subsidence space. It is the main reason that the subsidence coefficient of soft rock is bigger than hard rock.(4)The coupling model in this paper has a higher degree of the measured data, which overcomes the shortcomings of the traditional method which has the fast convergent boundary.(5)By using the numerical simulation method, it is concluded that the elastic modulus of rock mass, the ratio of strata and mining thickness, the ratio of mining depth and thickness and the compressive strength of rock mass are the main factors influencing the ground subsidence. The index of ground subsidence is defined based on the deformation characteristics of soft rock, which includes T1(the product of elastic modulus E and the thickness of rock stratum), T2(lithology difference index) and T3 (average elastic modulus of rock mass).(6)According to the law of rock fracture, it reveals the variation of the subsidence coefficient, ie the subsidence coefficient decreases with the increase of mining depth, both negatively approximate logarithmic relationship, and the more hard rock, subsidence coefficient is smaller, and vice versa.(7) Based on the space equivalent effect, an approximate method for calculating the surface subsidence coefficient is proposed. It can be gained by mining rate ε 采,broken coefficient K碎of caving roof and spatial correlation coefficient Kq, ie(8)Based on the global optimization algorithm, the program is compiled to automatically solve the prediction parameters, and has been applied in different mines. The result shows that it need not provide the initial value, and has simpler program, higher accuracy and smaller influence of human, is consistent with the measured data, which can satisfy the engineering application.