基于多元线性回归的深部复杂地应力场反演分析

Inversion Analysis of Deep Complex In-situ Stress Field Based on Multiple Linear Regression

深埋隧道开挖过程中,赋存在岩体中的极高地应力会导致隧道周围岩体破裂、变形甚至发生岩爆。某高原铁路隧址区存在较高的自重应力和构造应力,岩爆问题突出,为确保隧道围岩稳定及施工安全,明晰隧址区地应力场特征,基于多元线性回归原理开展超大埋深隧道初始地应力场反演分析。首先辨析隧址区应力场的影响因素,再结合水压致裂法钻孔资料,提出多因素边界荷载条件,最后利用数值分析手段推演隧址区的地应力场分布情况。研究结果表明,现场地应力实测结果揭示隧址区最大水平主应力值为15.21~40.82 MPa,最大水平主应力方向为N42°~54°E;隧道沿线区域应力状态以水平构造应力为主,主应力随深度的增加而增大,呈现出σ_(H)>σ_(v)>σ_(h)的规律;对比地应力实测值与反演值,大部分测点结果较为接近,且其变化趋势相同,证明该方法推演地应力场合理,但个别测点误差较大,特别是最大水平主应力方位角α_(H);受限于水压致裂法测量原理,剪应力τ_(xy)的反演精度不高,对最大水平主应力方位角的计算有一定影响。

During the excavation process of deep-buried tunnels,the presence of extremely high in-situ stress within the rock mass may lead to fracturing,deformation,or even rock burst occurrences in the surrounding rock mass of the tunnel.In a high-altitude tunnel site,there are high self-weight stresses and tectonic stresses which exacerbate the rock burst issue.In order to ensure the stability of tunnel surrounding rock and construction safety,and clarify the characteristics of in-situ stress field in tunnel site,the inversion analysis of initial in-situ stress field of super-large buried tunnel was carried out based on the principle of multiple linear regression.The influencing factors of the stress field in the tunnel site were analysed.Combined with the drilling data of hydraulic fracturing method,the multi-factor boundary load conditions were proposed.By means of numerical analysis,the distribution of in-situ stress field in the tunnel site was deduced.The research results indicate that the in-situ stress measurements reveal a range of 15.21 to 40.82 MPa for the maximum horizontal principal stress in the tunnel site area.The measured direction of the maximum horizontal principal stress is N42°to 54°E.The stress state in the tunnel along the alignment is dominated by horizontal tectonic stress.The principal stresses increase with depth,following the patternσ_(H)>σ_(v)>σ_(h).A comparison between the measured and inverted values of in-situ stress indicates that the majority of measurement points exhibit close proximity,with similar trends in their variations.The results prove the rationality of the method for deducing the in-situ stress field.However,there are significant errors at some individual points,especially in the azimuth angleα_(H)of the maximum horizontal principal stress.Constrained by the measurement principles of the hydraulic fracturing method,the accuracy of the inversion for shear stressτ_(xy)is not high.Its value has a certain impact on the calculation of the azimuth angle of the maximum horizontal principal stress.