由于双向非等压应力条件作用下的圆形巷道弹塑性问题求解难度较大，目前难以得到精确解析解。基于Mohr-Coulomb强度准则，将Kirsch解代入塑性条件中研究了非等压应力条件下圆形巷道围岩塑性区近似边界方程、分析了塑性区影响因素及形成力学机制。结果表明:侧压系数影响塑性区形态，原岩应力方向影响蝶形塑性区蝶叶方位，巷道半径与围岩岩性对塑性区形态均没有影响，但对塑性区的发育深度起着决定作用;侧压系数不等于1时，最大主应力方向不再平行于巷道切向，最小主应力方向不再经过巷道中心位置，引起围岩剪切破坏方向发生变化，而塑性区的扩展受控于最大剪应力的分布，此时塑性区形态偏离圆形;剪应力峰值点曲线与塑性区边界均随侧压系数变化而发生变化，但塑性区边界总是位于剪应力云图中最大剪应力峰值位置，且侧压系数越小主应力方向变化越大，塑性区不规则形态越明显;该求解方法没有考虑塑性区对弹性区应力的影响，属于近似求解法，但塑性区形态、发育规律与数值模拟结果相一致，并对解决工程问题具有指导作用，说明该塑性区边界方程近似解法是可信的。通过该近似方程能够掌握巷道围岩塑性区发育扩展规律，依此提出的可接长锚杆支护技术能够有效解决深部巷道锚杆易随顶板整体下沉、锚索破断引发的冒顶问题，较好的消除了冒顶隐患。

At present,it is difficult to obtain the exact analytical solution of elastic-plastic problem of circular roadway under bidirectional non-axisymmetric stress. Based on Mohr-Coulomb strength criterion, the approximate boundary equation of plastic zone is studied by substituting Kirsch equation into plastic condition. Also,the influencing factors and mechanics mechanism of formation of plastic zone are analyzed. The results show that the lateral pressure coeffi- cient affects the shape of plastic zone,the direction of in-situ stresses affects the position of butterfly leaf of butterfly- shaped plastic zone,and the radius and lithology of roadway affect the radius of plastic zone. When the value of lateral pressure coefficient is not equal to 1. 0,the direction of maximum principal stress is not parallel to the tangent direction of roadway,and the direction of the minimum principal doesn’t go through the radial direction of roadway,which cau- ses the change of shear failure direction of surrounding rock. The expansion of plastic zone is controlled by the distri- bution of maximum shear stress,and the shape of plastic zone deviates from the circle. The peak point curve of shear stress and the boundary of plastic zone change with the change of lateral pressure coefficient,but the boundary of plas- tic zone always locates at the peak value in the contour of shear stress. The smaller the lateral pressure coefficient,the greater the change of principal stress direction,and the more obvious the irregular shape of plastic zone is. The approx- imate method for solving the boundary of plastic zone does not consider the effect of plastic zone on the stress in elastic zone,but the shape and development of plastic zone are consistent with the results of numerical simulation. The study has a guiding role in solving engineering problems,which proves that the approximate solution of plastic zone boundary equation is valid. Through the approximate method,the development law of plastic zone in surrounding rock can be ob- tained. The support technology of butt long bolt can effectively solve the problem of roof fall triggered by the break of cable bolt and the overall subsidence of bolt with overall subsidence of roof,and better eliminate the hidden danger of roof fall. The field test results show that the equation of plastic zone has a theoretical significance and engineering ap- plication value.