Physical and mechanical properties of the coal-bearing strata rock in Shendong coal field

The physical and mechanical parameters of rock are the basic data for numerical simulation,similar simula- tion,key layer judgment,roof classification,support selection. Therefore,the test drilling holes were drilled from the ground to the floor of coal seam in the coal mine of the Bulianta,Daliuta and Buertai. Brazil splitting,uniaxial compres- sion and three axis compression tests were carried out. Finally,the parameters of density,RQD value,tensile strength, compressive strength,elastic modulus,cohesion and internal friction angle in different sedimentary periods were ana- lyzed. The results indicate that the strata of three test mines can be divided into eight depositional periods,cretaceous and Jurassic diazepam group,Jurassic Zhiluo formation,Jurassic Yanan group 1-2 coal,Jurassic Yanan group 2-2 coal, Jurassic Yanan group siltstone,Jurassic Yanan group 4 coal and at the bottom of Jurassic Yanan group,respectively.The sandstone is the main rock in the strata of Shendong coal field,especially in Cretaceous,sandy mudstone and mud- stone did not appear. With the increase of deposition time,the density of the rock has an increasing trend. However,the increase is not obvious. The tensile strength,compressive strength,elastic modulus and cohesion of the rock show a positive relationship with the deposition time. But there is no significant relationship among the RQD value,the internal friction angle and the deposition time. The deposition time has great influence on the mechanical parameters of the rock. The effect of deposition time on the tensile strength of mean-grained sandstone is the largest. The maximum value is 31. 2 times of the minimum value. The effect of deposition time on the compressive strength and elastic modulus of mean-grained sandstone is the largest. The maximum value of compressive strength is 12. 4 times of the minimum val- ue. The maximum value of elastic modulus is 32. 8 times of the minimum value. The physical and mechanical parame- ters of rock in the Cretaceous and Jurassic diazepam group are much smaller than other sedimentary periods.