Construction Risks of the Shield Tunnel Undercrossing the Operating Line in Loess Platea Area and Its Countermeasures
Based on the diversion tunnel of the south main line in PhaseⅡof Hanjiang-to-Weihe River Water Diversion Project in the loess platea area,this paper discusses and analyzes the influence of formation disturbance caused by the shield diversion tunnel under the subgrade section of the expressway and operating line in the loess platea area.On this basis,measures such as strengthening grouting,pre-strengthening of strata,controlling shield soil bin pressure and excavation amount are proposed to mitigate construction risks associated with uneven formation settlement.The study also investigates on the gushing formation mechanism of shield tunneling through loess platea areas to address challenges related to high groundwater levels,strong sand permeability,significant mud leakage per ring,prolonged cleaning time,water gushing at shield tail,and frequent spouting of screw excavators.Consequently,anti-spouting construction countermeasures including slag improvement and optimization of shield tunneling parameters are formulated.Construction risk analysis is conducted for underpass operation lines in loess platea areas along with corresponding countermeasures to provide guidance for field operations and similar projects.
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