含水率对古土壤隧道围岩膨胀性的影响

早胜3号隧道是银西(银川-西安)铁路控制性工程,隧道洞身穿越的第三系古土壤具有膨胀性,其变形影响到施工期围岩稳定及运营期结构安全。本文对古土壤物理力学性能、矿物成分与微观组构进行了测试,开展了不同含水率下原状、重塑古土壤试验,并应用GTS/NS有限元软件分析不同含水率下隧道围岩的力学特性及变形规律。结果表明:原状古土壤含水率低于19%时膨胀力变化较大,随含水率增大膨胀力近于完全释放;重塑古土壤膨胀力对含水率变化的敏感程度减弱,但重塑扰动使得相同含水率重塑古土壤的膨胀力远高于原状古土壤;不同含水率下围岩应力分布规律变化较小,拱顶沉降和边墙水平位移变化较大。本文确定了原状、重塑古土壤含水率与膨胀力的关系,对类似工程设计与施工具有指导作用。

Influence of Water Content on Swelling of Surrounding Rock of Paleosol Tunnel

Zaosheng No.3 tunnel is a controlled project of Yinchan-Xi’an Railway.The tertiary paleosol crossed by the tunnel is of swelling,and its deformation affects the stability of surrounding rock during construction and structural safety during operation.In this paper,the physical and mechanical properties,mineral composition and microstructure of paleosol were first tested,and then experiments on both the undisturbed and remodeled paleosol were carried out under different water contents.After that,GTS/NS finite element software was used to analyze the mechanics and deformation of the tunnel surrounding rock under different water contents.The results show that when the water content is less than 19%,the swelling force of the undisturbed paleosol changes greatly,and it is nearly completely released as water content increases.The remodeled paleosol shows less sensitivity to the change of water content,but due to the remodeling disturbance,the swelling force of the remodeled paleosol is higher than that of the undisturbed paleosol with the same water content.Under different water contents,the stress distribution of the surrounding rock changes slightly,while the settlement of the vault and the horizontal displacement of the sidewall significantly.This paper determines the relationships between the swelling force and water content of both the undisturbed and remodeled paleosol,which has a guiding role in the design and construction for similar projects.