Study on roof rock temperature and stress under heat transfer in underground coal gasification channel

Aiming at the problems of roof rock stability and efficient utilization of gasification heat in underground coal gasification, a calculation model of flow field and stress field with heat-fluid-solid coupling was established. The temperature and stress changes of roof rock were explored. It is found that the temperature increment of roof rock before combustion surface is lower than that after combustion surface. With the advance of the combustion surface, both the temperature increment and high temperature area of the roof rock around the exhaust drilling hole increase. The high temperature can greatly increase the tensile stress and shear stress at the bottom of roof rock, and the maximum tensile stress and shear stress increase by more than 10 times. The maximum tensile stress and shear stress occur at the location of the combustion surface of the roof rock bottom, and tensile failure mainly occurs in roof rock.