Study on disaster-causing structure classification,disaster-pregnant and failure modes of surrounding rock mass in sandy dolomite tunnels
Sandy dolomite is widely distributed in underground engineering in southwest China.Severely and completely sandy dolomite has a broken rock mass structure and poor water stability.During the construction of the sandy dolomite tunnels,disasters such as collapse,water inrush and water-sand inrush occurs frequently.However,the research on the gestation,formation and occurrence of sandy dolomite tunnel disasters is almost empty,and special systematic research needs to be carried out.This paper collected more than eighty cases of sandy dolomite tunnel collapse,water inrush and water-sand inrush.In-depth investigation and analysis of the geologic and structural conditions of the occurrence of related disasters were performed.From the bad geological conditions and the main influencing factors of disasters,the hazard-causing structures of the sandy dolomite tunnels are divided into four categories including eight types.The first category is fault,including three types,i.e.,the anhydrous fault type,the water-conductive fault type and the water-resistive fault type.The second category is fracture,including the monoclinic fracture type,the interlayer fracture type and the sandy strip type,The third category is fold,including the anticline type and the syncline type.The final category is the karst pipeline.These hazard modes are divided into three types based on the time evolution characteristics of disaster occurrence,such as the immediate revealed type,the progressive failure type and the intermittent failure type.From the perspective of the main engineering site where the disaster occurs,the tunnel is divided into twenty failure modes of four parts.And the corresponding engineering control measures are put forward.Finally,the case analysis and control measures of the typical disaster tunnel section of the Water Diversion Project in Central Yunnan are introduced.Consequently,the research results have important significance for the design,construction,risk assessment and preventive control of underground engineering in sandy dolomite.
tunnel engineeringsandy dolomitehazard-causing structurehazard modefailure modeengineering case
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