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