Stability of Excavation Face of Double-Mode Shield in Earth Pressure Mode Crossing Fault Zone of Pearl River
In view of the stability of the excavation face of the double-mode shield crossing the fault zone of the Pearl River,the project of the section from Hongshengsha Station to Yufengwei Station of the second phase of Guangzhou Metro Line Seven was studied.Through numerical simulations conducted to analyze the whole area and the local high-risk area of the shield crossing the fault zone of the Pearl River,this paper explored the construction risk of the shield crossing process.Besides,this paper analyzed the influence of different support stresses and grouting pressures on the stability of the excavation face and ground deformation,and finally,the tunneling parameters analysis was used to evaluate the rationality of numerical simulation.The results show that ① when the tunnel excavation surface is distributed with soft soil above and hard soil below,large ground settlement is prone to occur during the shield tunneling process.When it is distributed with hard soil above and soft soil below,large ground uplift is prone to occur;② The excavation face is likely to become unstable in the weak local stratum when the shield passes through the composite stratum.The soil mass in the weak stratum deforms towards the inside of the tunnel when the support stress is less than the static earth pressure in the weak stratum,and the deformation increases with the reduction of the support stress ratio;③ The grouting pressure does not affect the stability of the excavation face but is inversely proportional to the ground settlement.Greater grouting pressure indicates lighter ground settlement,and the shield tunneling verifies the correctness of the numerical simulation results.
dual-mode shieldfault zoneexcavation face stabilitynumerical simulationsupport stressgrouting pressure