双孔劈裂条件下地应力及孔间应力的耦合分析

Coupling analysis of in-situ stress and inter hole stress under double-hole splitting

针对注浆过程中的裂纹扩展问题,通过理论分析和数值模拟,研究了地应力与孔间应力耦合作用下劈裂注浆的作用机理.研究结果表明:单孔劈裂主要受地应力影响,钻孔沿着最大主应力方向或垂直于最小主应力方向扩展.双孔劈裂受到地应力与孔间应力扰动的耦合作用,相当于力矩合成定理,使钻孔沿其合力方向扩展(孔距较大时相当于两个单孔劈裂);其劈裂破坏过程可分为应力积累、裂纹稳定扩展、失稳破坏三个阶段,双孔间观测点处的最大主应力和孔隙水压力会随着计算步数的增加分别对应形成应力跌落区和能量累积区;钻孔间距较小时初始起裂压力的变化不明显,而间距较大时初始起裂压力随侧压力系数的增加而增加.

Based on the problem of crack propagation in the grouting process,theoretical analysis and numerical simulation are adopted to study the mechanism of splitting grouting under the coupling effect of in-situ stress and inter hole stress.The results show that single-hole splitting is mainly affected by in-situ stress,boreholes cracking evolves along the direction of the maximum principal stress or perpendicular to the direction of the minimum principal stress.Double-hole splitting is affected by the coupling effect of inter hole stress and in-situ stress disturbance,which is equivalent to the theorem of moment composition,making the boreholes cracking develop along the direction of its resultant force(when the distance between holes is long,it is equivalent to the splitting of two single holes).The failure process can be divided into three stages:stress accumulation,stable crack propagation,and instability failure.The maximum principal stress and pore water pressure at the observation points between two holes will form stress drop area and energy accumulation area,respectively,with the increase of calculated steps.When the space between boreholes is small,the initial crack pressure changes little;when the space between boreholes is great,the initiation crack pressure increases with the lateral pressure coefficient.