Abstract:
In order to study the variation law of shear strength of plastic coal under the coupling effect of temperature - moisture content,and ensure safe,efficient and stable mining of soft coal seam,the direct shear test was used to analyze the shear strength characteristics of remodeling coal under the coupling effect of low temperature (20 ℃ ,0 ℃ ,-10 ℃ ,-20 ℃ ,-30 ℃ , -40 ℃ ) and certain moisture content (0,0. 8%,4%,8%,12%,16%). The influence of temperature and moisture content on shear strength was analyzed by mathematical statistics. The results show that the cohesion of moisture content of remodeling coal at 0 increases exponentially with the decrease of temperature. Under the coupling effect of temperature and moisture content,the shear strength of remodeling coal is proportional to the vertical stress,which conforms to Mohr-Coulomb criterion. When the temperature is from 10 ℃ to 20 ℃ and the water content is from 12% to 16%,the cohesion reaches the maximum value of 322. 9 kPa,and the minimum cohesive of 138. 0 kPa appears near the temperature of -40 ℃ and the moisture content of 4%. At temperatures ranging from -20 ℃ to 40 ℃ ,the internal friction angle of remodeling coal gradually decreases to the minimum value of 18. 25° with the increase of water content. When the moisture content is 6% to 13% and the temperature is -20 ℃ to 10 ℃ ,the internal friction angle reaches the maximum value of 31. 45° and the corresponding shear strength reaches the maximum value. Under the coupling effect of temperature - moisture content, the shear strength, internal friction angle and cohesion of remodeling coal are greatly affected by temperature.