Research Of Quantitative Relation Between Coal-mining-induced Subsidence And Geological Influencing Factors By Means Of Numerical Test

As so far now, the mechanisms and the regularity of how geological factors influencing the mining subsidence had been studied a lot, but due to the geological factors had not been fully considered, so the quantitative relation between these factors and the mining subsidence had little been realized, and the research achievement at present can't meet the demand of accurate prediction before the mining activities. So by means of numerical test, this paper got the date between the geological factors, such as tectonic medium, interfaces and stresses, and mining subsidence under some certain mining conditions. At last, the quantitative relations were established. The main results were as following :Without considering structural interfaces and tectonic stresses, when the mining depth was certain, the losses thickness had a negative relation with the ground maximum subsidence value, and the relation was positive between the bedrocks thickness and the maximum subsidence value. The comprehensive hardness of overburdens and the ratio of soil and rock thicknesses could be used to reflect the thickness and hardness characteristics of tectonic medium, and the former had a negative relation with the ground maximum subsidence value, the latter had a positive relation. If the phicical and mechanical parameters of overlying strata couldn't be obtained, then the comprehensive hardness of overburdens couldn't be actually calculated, under this situation, the ratio of soil and rock thicknesses could be used to predict the mining subsidence as the main structural medium factor, and the quantitative relation between the ratio and the maximum subsidence value was as following :f₄(x) = -80.54*(0.49x+1)¹⁰+80.54*(0.06x+1)¹⁰-524.8776Without tectonic stresses's influencing, letting average degree of rock represent the joint density in RFPA numerical software, when the average degree of rock increased, the joint density would reduce meanwhile, and the maximum subsidence value would reduce accordingly. As for the joint's angle, the maximum value would decrease firstly and then increase, the minimum appeared when the joint angle was between 40 degree and 50 degree, and the position of the maximum value in the groud was different as the angle changed.For the tectonic medium without interfaces, with the increasing of compressive stresses value, the groud subsidence value would reduce while the scope would enlarge. For the overburden obtaining joints, the maximum subsidence value would reduce when the angle was fixed but the compressive stress value increased, and the maximum subsidence value would reduce firstly and then increase when the compressive stress value was fixed but the angle increased. For the reverse fault, the maximum subsidence value would reduce with the subsidence scope enlarging when the drop and angle were fixed, and the maximum subsidence value would increase with the drop's increasing when the compressive stress was certain. When it was to the normal fault, with the increasing of tensile stress value, the distribution scope of tensile stress area enlarged, the maximum subsidence value increased, but the scope of subsidence basin had little change.