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应用弹、塑性应力－应变理论，根据井眼围岩应力状态对岩石塑性体积应变影响的假设条件，弹、塑性岩石的应力－应变简化曲线，以及极限强度和残余强度准则，推导出了求解岩石变形参数关系式．并分析了井眼围岩的临界井眼压力状态，建立了求解弹、塑性地层井眼围岩应力状态方程，为合理预测和过后分析井眼缩径和井壁的稳定性提供了计算方法．计算实例表明，当轴向应力较小时，会导致井壁岩石产生较大的塑性屈服区；塑性区半径会随井眼压力的增大而减小．
According to the elastic and plastic stress-strain theory, according to the assumptions of the influence of stress state of rock surrounding rock on the plastic volumetric strain of rock, the stress-strain simplified curve of elastic rock and plastic rock, and the ultimate strength and residual strength criterion, Deformation parameters of the relationship. The critical wellbore pressure state of wellbore surrounding rock is analyzed, and the stress state equation of surrounding rock of wellbore and plastic strata is established. The calculation method is provided for the reasonable prediction and subsequent analysis of borehole diameter reduction and wellbore stability. The calculation example shows that when the axial stress is small, the plastic deformation zone will be produced in the sidewall rock, and the radius of plastic zone will decrease with the increase of wellbore pressure.