When the effect of intermediate principal stress was considered in different degrees , the dimensions and shapes of surrounding rock mass is rather different , and this phenomenon will be more obvious with the increase of the difference of horizontal stress and vertical stress 当不同程度地考虑中间主应力的影响时,围岩塑性区形状和大小有较大不同,且随水平应力与垂直应力差异性的增大,这种影响趋于明显。