南昌河流阶地内地铁车站基坑变形研究

Study on Deformation of Deep Excavation for Metro Stations in River Terraces in Nanchang

对南昌地铁1~4号线车站基坑地层条件和支护结构进行统计分析,将赣江河流阶地分为典型的Ⅰ类(上覆约20 m厚河流沉积层、高地下水位)和Ⅱ类(约30 m厚河流沉积层、低地下水位)二元结构地层及相应的支护体系。然后,对Ⅰ类地层中地铁2号线丁公路南站和1号线珠江路站、Ⅱ类地层中的3号线振兴大道站分别开展基坑支护结构变形和地面沉降数值分析,计算与实测结果吻合很好,表明采用小应变刚度硬化模型(HSS)有限元分析和砂土变形模量E50ref=1.5N(N为修正标贯击数)可合理地预测南昌河流阶地内地铁车站基坑开挖引起的支护结构变形和地面沉降。在此基础上,对南昌河流阶地内的地铁车站基坑支护结构变形和地面沉降进行计算和统计分析,得出地铁车站基坑支护结构最大侧向变形和最大地面沉降与开挖深度的关系分别为δh,max/H=0.05%~0.12%,δv,max/H=0.03%~0.10%,最大沉降与最大侧移满足δv,max/δh,max=0.45~1.4。

Statistical analysis is firstly carried out for the ground conditions and retaining structures for deep excavations of the metro stations of Nanchang Metro Lines 1~4,which splits the River Terraces into two typical categories of ground conditions(typeⅠand typeⅡ)with corresponding retaining structures for deep excavations for metro stations.Then taking Nanchang Metro Line 2 Dinggong Road South Station,Line 1 Zhujiang Road Station and Line 3 Zhenxing Avenue Station as examples,numerical analyses with the small strain stiffness hardening(HSS)soil model are conducted and the predicted deflection of retaining walls and ground settlement are in agreement with field data.This shows that using HSS soil model and E50ref=1.5N for sand deformation modulus(N is the corrected count of blow)can well predict the deflection of retaining walls and ground settlement.On this basis,this paper numerically and statistically analyzes the deflection of retaining walls and ground settlement in Nanchang area,and draws conclusions that for the deep excavations of the subway stations in Nanchang typical river terraces,the ratios of the maximum lateral deflection of retaining wall structures and the maximum ground settlement to the excavation depth areδh,max/H=0.05%~0.12%andδv,max/H=0.03%~0.10%,respectively,and the ratio between the maximum ground settlement and maximum lateral deflection is aboutδv,max/δh,max=0.45~1.4.