高地应力层状软岩隧道大变形预测分级研究

Study of Large Deformation Classification Criterion for Layered Soft Rock Tunnels under High Geostress

为探明高地应力层状软岩隧道的非对称变形破坏规律及其支护结构的非对称受力特性,结合碳质千枚岩力学特性与变形破坏机制的各向异性特性,对层状软岩隧道围岩的非对称变形破坏特征进行了分析.在93座典型高地应力层状软岩隧道变形数据的基础上,系统性地分析了隧道拱顶沉降、水平收敛、最大变形量与地应力、岩体抗压强度、隧道埋深之间的关系.研究结果表明:高地应力层状软岩隧道的变形量与最大地应力、岩体抗压强度、埋深的分布较为离散,在一定地应力、岩体强度或埋深条件下,隧道变形量既存在于高值区间,也存在于低值区间;隧道变形量随地应力的增大、岩体强度的降低、埋深的升高逐渐向高值区间靠拢,高地应力层状软岩隧道大变形是高地应力、软弱围岩、层理弱面耦合作用的结果;基于隧道最大变形量与隧道强度应力比的幂指数变化规律,提出了高地应力层状软岩隧道的大变形预测分级指标.

The asymmetric deformation failure characteristics and asymmetric mechanical behaviour ofsupporting structures in layered soft rock tunnels under high geostress, combined with the anisotropic mechanicalproperties of carbonaceous phyllite, were investigated. Based on the deformation data of 93 layered soft rocktunnels under high geostress, the relationships between roof settlement, horizontal convergence, largestdeformation and geostress, rock compressive strength, and overburden depth were systemically analysed. Theresults show that the deformations are discretely distributed according to the variations in geostress, rockcompressive strength, and overburden depth. Under certain parameters of geostress, rock compressive strength, oroverburden depth, the deformations are distributed in both the high- and low-value zones. With increasinggeostress and overburden depth, and with decreasing rock compressive strength, the deformations graduallyapproach the high-value zone. This means that the large deformations of layered soft rock tunnels under highgeostress are determined by the combined action of high geostress, weak surrounding rock, and a weak beddingplane. Based on the power exponent variation law between the largest deformation and the strength-stress ratio, anew classification criterion for large deformations is proposed for layered soft rock tunnels under high geostress.