深井掘进技术在厚层高渗透性粉细砂层中适用性的数值模拟研究

Numerical Simulation Study on Applicability of Vertical Shaft Machine in Thick and High Permeability Silty Fine Sand

科学合理高效开发深层地下空间是城市不断发展的必然趋势与重要难题。深井掘进技术(vertical shaft machine,VSM)是一种开挖超深竖井的新型工法,该技术施作的竖井结构形式简单、结构受力状态好、施工速度快、对周边环境扰动小、适用性广泛,可被广泛用于城市深层地下空间的点状开发。以中国首例使用VSM施工的南京市儿童医院沉井停车库项目为原型,建立在砂性土中开挖60 m竖井的数值模型,重点研究VSM竖井在厚层高渗透性的粉细砂层开挖过程的变形情况与开挖面的稳定性问题。数值模型结果表明:60 m竖井开挖过中地表变形量均控制在毫米数量级,且最大地表变形量不超过13 mm;在水位差1 m的水下施工过程中安全系数均较好控制在2.0以上。对于变形问题,分析不同开挖深度下的井底隆起变形和地表变形情况,表明在60 m开挖深度内,使用VSM开挖砂性土竖井在深度、安全性和对周边环境扰动上均具有明显优势。针对开挖面稳定性,计算分析与竖井内外水位差和竖井深度相关的开挖面安全系数,计算结果可用于指导实际施工,实现分段施工与精细化控制。

Scientific,rational and efficient development of deep underground space is an inevitable trend and an important problem in the continuous development of cities.Vertical shaft machine(VSM)is a new construction method for excavating ultra-deep shafts,which has a fast excavation speed and wide applicability.The shaft constructed by VSM is simple in structure,good in structural stress state,fast in construction,and has little disturbance to the surrounding environment,and can be widely used in point-like excavation for the utilization of deep underground spaces in cities.The first case of using VSM in the construction of the parking garage project of Nanjing Children s Hospital in China was used as a prototype,and a numerical model for excavating a 60 m shaft with VSM in sandy soil was established focusing on the deformation of the silty fine sand and the stability of the excavation surface.The results of the numerical model show that the surface deformation during the excavation of the 60 m shaft is controlled at the order of millimeter,and the maximum surface deformation do not exceed 13 mm.The safety factor is well controlled above 2.0 during the underwater construction process with a water level difference of 1 m.For the deformation problem,the uplift deformation of the bottom of the well and the surface deformation under different excavation depths were analyzed.And the safety factor of the excavation surface was calculated and analyzed related to the water level difference inside and outside the shaft and the depth of the shaft,which could guide the actual construction and realize segmented construction and refined control.