Discussion on characteristics of pebble layer and key tunnel technology in Eastern Qinghai
SHI Bo1，2，WANG Yongliang3，XIAO Bo1，2，LI Ke1，2
(1. China Merchants Chongqing Communications Research and Design Institute Co.，Ltd.，Chongqing 400067，China；2. National Engineering Laboratory for Highway Tunnel Construction Technology，Chongqing 400067，China；3. Qinghai Transportation Holdings Group Co.，Ltd.，Xining，Qinghai 810008，China)
Abstract：In order to improve the construction technology of the pebble layer tunnel in the eastern part of Qinghai，the characteristics of the pebble layer distributed in the area were summarized. The surface displacement and the deformation of the tunnel roof during the excavation process were measured by the 1∶20 geometric model test. Combined with the monitoring data of the tunnel site，it reveals the rule that the arch top displacement is fast in the early stage and slow in the later stage during the excavation of the pebble layer tunnel. According to the unique sedimentary distribution law of the pebble strata in the eastern part of Qinghai，four types for tunnels to crossing the pebble strata are summarized，and their risk points and countermeasures are analyzed. Based on the construction experience of many projects in this area，it is put forward that the core concepts and important difficulties in the design and construction of the pebble layer tunnel are put，and the scope of application of small pipes and self-advancing anchors is given. In the end，the calculation formula of the maximum allowable settlement value of the ground surface under the limit state through the peck formula is deduced，which is convenient to improve the tunnel construction management.
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2021, Vol. 40 
