Mechanical Properties of Mega-Thick Alluvium and Their Influence on the Surface Subsidence

Surface subsidence caused by mining is closely related to the nature and structure of overburden and soil layer. Characteristics of mining subsidence under the condition of mega-thick alluvium are special. Through analyzing the mechanism of mining subsidence with mega-thick alluvium, surface subsidence was divided into three parts, i.e., bedrock surface subsidence with non-alluvium, bedrock surface subsidence with mega-thick alluvium and consolidation subsidence. Mechanical Properties of Mega-thick Alluvium and their Influence on the Surface Subsidence were studied by means of geotechnical test and numerical simulation. The shear strength of clayey soil in Jiaozuo mining area were researched through unconsolidated undrained triaxial test. The ranges of internal friction angle and cohesion force of clayey soil in this area were presented. Taking a panel covered by mega-thick alluvium as an example, based on the test results, the influences of thickness, friction angle and cohesive force of alluvium on surface subsidence were analyzed. Results of numerical simulation were compared with field data. Results show that the maximum surface subsidence value increases with the increase of the thickness of alluvium, decreases with the increase of the friction angle and cohesive force. This paper combines geotechnical tests of alluvium mechanical properties with surface subsidence, which has a certain guiding significance for the study of mining subsidence.