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| Research on the Advanced Measures for Large Span Tunnel in Dense Dry Fine Sand Stratum |
| WANG Li - qing |
| (The Third Railway Survey and Design Institute Group Corporation，Tianjin 300251，China) |
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Abstract Research purposes ： In the construction process of Shangbai tunnel in Datong - Xi an Passenger Dedicated Line，tunnel face presents dense dry fine sand stratum， lenticular， and disturbance produced sand leakage and sand gushing，unable to formthe desired contour，so there is a higher risk. The main performance is that the cohesion is low， the disturbance of a short time accumulates piles，and can not form the arch effect; high sensitivity，damage is often instantaneous，sudden，prone to cavities， which generally form cavity from the soil sand boundaries. In view of the existing problems，the measures need to be studied to ensure the tunnel face stability and construction safety by means of what measures to reinforce the dense dry fine sand stratum，to form the arch effect and tunnel face stability and control of subsidence and deformation. Research conclusions ：( 1) Make full use of high pressure jet grouting to mix fine sand with cement，recombine the rock mass structure， and form cyclic concretion body to solve the construction problems. (2) Realizing the mechanized construction of the large section of the weak stratum is the guarantee of realizing the basic requirements of the 11 six in one modem construction management. ( 3 ) It remove the pipe - shed studio， which has simple process， less interference, easy operation and high efficiency. (4) Horizontal rotary jet grouting pile in advance reinforcement can protect the surrounding rock and form cyclic concretion body around the scheduled tunnel, which has the advantages of large stiffness $ high strength and strong controllability in the construction. Preliminary arch after excavation can play a role, to ensure the safety of construction and control the high risk tunnel construction risk, which is innovation and breakthrough in the technical field of construction. (5 ) As a new technology in the consolidation of the pipe shed, the smaller diameter of the pile adding pipe shed makes up for the construction defects of the consolidation, inhibits the settlement and deformation, and has low investment$ good stress$ safety in construction and other advantages$ which can be further promoted and applied.
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Received: 23 November 2015
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2016, Vol. 33 
