Abstract: To study the mining damage regulations of the ground surface under the geological conditions of thick loess and thin bedrock in mountain areas,Hezhai coal mine,in the south of Shanxi province,is chosen as the study case.Based on the field investigations,the numerical simulation software of UDEC is employed to obtain the relationship between strata fracture and surface displacement.The numerical tests show that the most serious surface deformations happen upon the fracture positions of the rock strata.A fracture model of overlying strata is established as the beam structure under non-uniform load,from which the span equations of the primary fracture and periodic fractures are deduced.The comparison between the calculated results and the locations of surface fissures measured by investigation shows the method developed in this study is available.The study shows that it is feasible to predict the surface crack spacing by using the non-uniform load beam structure fracture model under the condition of thin bedrock geological condition in the thick loess layer in the mountain area.

Key words: Mountain areas, Thick loess, Beam structure, Non-uniform load, Crack spacing