Research on Sand Burst Mechanism and Control Technology of Neogene Soft Rock Tunnel
To study the mechanism of sand surge disaster in tunnel construction in the Neoproterozoic sandstone stratum and to develop corresponding treatment measures,the Xiangshan Tunnel of the Yinchuan-Lanzhou High-speed Railway was taken as the research object.Firstly,the sand surge phenomenon during the construction process were analyzed,quantitative analysis of the composition of the surrounding rock particle size,the water content of the rock layer,mud content was made and the mechanism of the sand surge in this type of stratum was researched.Secondly,the reinforcement measures taken after the disaster occurred were summarized,and the reasons that the reinforcement measures adopted in the process failed to meet expectations were analyzed.Finally,the curtain grouting+surface precipitation program was explained.Through the study,it is concluded that:(1)The phenomenon of sand gushing in the Neoproterozoic soft rock tunnel is mainly related to the particle size,water content,mud content,and force on the critical surface.(2)When the sand layer water content increased to 20%,the phenomenon of sand surge intensified leading to large area slip.(3)For different sizes of the sand surge to take a small conduit in advance combined with backward grouting way reinforcement and cave precipitation measures,due to the high content of fine sand and the impact of groundwater,the effects do not reach expectations.(4)Curtain grouting and surface precipitation are used to reinforce the surrounding rock,which achieve the expected effect.
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