湿度劣化作用下泥质砂岩输水隧洞安全性分析

Safety Analysis of Argillaceous Sandstone Water Conveyance Tunnel Considering the Humidity Degradation of the Surrounding Rock Strength

为分析软岩遇水劣化对围岩承载力的影响、评估输水隧洞的安全性,以兰州市水源地建设工程输水隧洞泥质砂岩为研究对象,开展不同浸润时间的单轴及三轴压缩试验,将泥质砂岩湿度劣化过程等效为围岩弹模及强度折减,开展考虑围岩劣化的输水隧洞施工期和运行期安全性仿真分析。结果表明:随浸润时间增加,岩样单轴抗压强度逐渐减小,最大轴向应变逐渐增大,三轴压缩条件下岩样偏应力峰值逐渐减小;施工期泥质砂岩洞段围岩位移随湿度扩散深度增大而增大;运行期围岩劣化使管片衬砌位移和主应力增大,管片间张开度增大,隧洞运行时容易发生渗漏;围岩加固和豆粒石填充可有效减小管片间的张开度,使管片受力最不利位置从拱底变为拱顶,降低隧洞渗漏水的可能性,有利于输水隧洞的安全运行。

In order to analyze the impact of water-induced deterioration of soft rocks on the bearing capacity of surrounding rocks and evaluate the safety of water tunnels,this study took the silty sandstone in the water supply tunnel at the Lanzhou Water Source Construction Project as the research object,and carried out uniaxial and triaxial compression tests under different rock soaking times,in which the moisture deterio-ration process of silty sandstone was equivalent to the reduction of surrounding rock elastic modulus and strength,and conducted a simulation analysis on the safety of the water tunnel during construction and operation,considering the moisture degradation of surrounding rocks.The results indicate that as the soaking time increases,the uniaxial compressive strength of the rock samples gradually decreases,the maximum axial strain gradually increases,and the peak deviatoric stress of the rock samples under triaxial compression conditions gradually decreases.During the construction period,the displacement of surrounding rocks in the silty sandstone tunnel increases with the acceleration of moisture diffusion depth.During the operational period,the deterioration of surrounding rock results in increased displacement and principal stress of the segment lining,as well as the opening between pipe sections,which makes the tunnel easier to leak.The reinforcement of surrounding rocks and the filling of pebble stones effectively reduce the opening between the segments,shift the most unfavorable position of stress on the segments from the arch bottom to the arch top,reduce the possibility of tunnel leakage,and facilitate the safe operation of the water tunnel.