Research On Reserving Coal Pillars Under Weathered Overlying Strata In Wolonghu Coal Mine

This paper took Wolonghu coal mine as an example, researched the study area’sgeological and hydrogeological conditions, watery features of loose aquifer besideswater-resisting-isolating capability of overlying strata, using the in-site drilling andthe indoor test technology. Conclusions are drawn as follows: the plasticity andswelling property of the soil of the third aquiclude is good and it has largethickness with distributional stability. So the soil of the third aquiclude is stableregional good water-resisting layer. The soil of the fourth aquifer is weak richwater aquifer. Influenced by weathering, the overlying strata of108working face ismainly composed of shale and siltstone whose strength are lower,it is good inimpermeability and revival capability of water-stop. The type of roof strata of108working face belongs to weak strata. The uniaxial compressive strength of thespecimen of10coal seam is close to or more than40MPa, so it is belonged to hardrocks. In the stoping upper bound lifting test section, the development height of theTwo Zone was observed. The exact damage by mining of overlying strata anddeformation position was got.Taking108working face as research object, three-dimensional numerical modelwas established under the condition of overlying strata with weathering zone andoverlying strata without weathering zone by use of FLAC^3D, and also the differencebetween stress field, displacement field and plastic failure was analyzed. Theheight of caving zone and the height of the fissure zone were calculated by practicalobserved, simulation and formulas. Comparing three kinds of results, the height ofcoal pillar was determined.