软硬岩交替区隧道初始地应力场反演研究

Inversion study on initial in-situ stress field of tunnels in soft and hard alternating rock area

软硬岩交替区岩体结构面两侧岩性变化剧烈,地应力分布复杂。为探明软硬岩交替形成的岩体结构面对初始地应力场的影响,以云南曼么二号隧道为研究背景,构建包含高程信息的三维数值计算模型,基于多元线性回归法反演获得了隧道轴线处的初始地应力场,分析了软硬岩交界面处水平主应力异常的影响因素。结果表明:水平主应力异常与软硬岩交界面两侧围岩弹性模量、埋深和结构面倾角的差异性有关;通过正交试验对各影响因素进行显著性评价,发现围岩弹性模量和埋深对水平主应力的影响显著,是水平主应力异常的关键因素。研究成果可为隧道(洞)开挖过程围岩稳定性评价与支护方案设计等提供依据。

The lithology on both sides of the structural surfaces in soft and hard alternating rock areas changes dramatically,leading to complex distribution of in-situ stress.In order to ascertain the influence of rock mass structural surface in the soft and hard alternating rock area on the in-situ stress field,a 3D numerical computational model containing elevation information was established for the Manmo No.2 Tunnel in Yunnan Province.The initial in-situ stress field of the tunnel axis was obtained by inversion with multiple linear regression method,and the influencing factors of the horizontal principal stress anomaly at the interface of soft and hard rocks were analyzed.The results show that the anomaly of the horizontal principal stress was related to the differences of elasticity modulus of country rock on both sides of the interface,the burial depth and the dip angle of structural surface.The significance of each influencing factors was evaluated by orthogonal test.It was found that the elasticity modulus of country rock and the burial depth had a significant influence on the horizontal principal stress,which were key factors for the anomaly of the horizontal principal stress.The research results can provide basis for country rock stability monitoring and the design of support scheme during tunnel excavation.