Basic Testisng Research On Overlying Strata Deformation And Characteristics Of Surface Movement Under Deep Mining

The law of overlying strata deformation, break and movement, and behavior characteristics under deep mining is obviously different from that of shallow mining. Some relevant researches are far from enough, and still be blank or lack of necessary basic research in many aspects. This paper is supported by the National Natural Science Foundation of China (50874070), Doctoral Fund of Ministry of Education of China(200804240004) and Natural Science Foundation of Shandong(Y2008F01). It is under condition of working faces which are more than 1000m mining depth in the TangKou Coalmine, Zibo Mining Group Co., Ltd. The stress and strain field evolution and dynamic evolution law of overlying strata during mining process was basically studied combining with indoor tests of rock mechanics, mechanical physical simulation and similar material simulation. The main research contents and conclusions are as follows:(1) Some specimens of coal were used to make uniaxial and triaxial compression tests, regressively analyzing the main stress formula of coulomb criterion; short time creep tests of specimens were carried out to analyze the characteristics of creep failure and creep constitutive model by step loading, gaining the creep parameters under each stress level by curving fitting.(2) Based on the pillar monitoring of abutment pressure, lateral deformation and roof abscission layer in 4301 working face, the failure movement of coal and overlying strata during mining process was analyzed. The results indicate that the pillars are at the unsteady time during mining process with the maximum pillar change range of lateral displacement, and the pillar force is corresponding to deformation; spatial structure with internal-external stress field characteristics is formed after mining, and the maximum influence range of external stress arch is also the range of overlying strata which has obvious influence on surface subsidence.(3) Applying the combination of new physical simulation test of mechanics with 3-D similar material simulation test, the change of abutment pressure on coal and dynamic evolution law of overlying strata during subsidence movement were studied and analyzed the relationship between abutment pressure and overlying strata movement, proposing the overlying strata deformation model based on the transfer of stress field. Taking the edge points of external stress field as the endpoints to calculate each angle value of surface movement basin would be more suitable for the characteristics of larger influence range but smaller mining effect under deep mining.(4) Numerical simulation test was made to study the evolution law of overlying strata stress field based on the indoor testing results. The results show that the stress field of overlying strata has the apparent characteristics of dividing zone after mining and forms a decreased main stress zone around goaf corresponding to the failure zone of mining overlying strata.(5)Through curve fitting and parameters got by model, some data of surface observation stations laid flexibly along any direction in 230 and 430 mining area were analyzed by inversion processing, gaining the reliable surface movement law and estimated parameters of deformation. The characteristics of discontinuous subsidence movement, mutational concentrated deformation and periodic delay movement under deep mining were even more apparent than that of shallow mining.