软土地铁联络通道加固开挖的变形模拟分析

Simulation Analysis of the Excavation Deformation of a Reinforced Subway Cross-Passage in Soft Soil

文章针对珠三角地区冲积软土中的一个地铁联络通道开挖加固工程实例,用三维有限元模型分别对深层搅拌桩法加固和小导管注浆超前支护加固后的开挖过程进行了模拟,并计算分析了在不同方案下联络通道的拱顶位移。分析结果表明:深层搅拌桩适应性较强,可以采用不同方案加固土层和控制开挖变形,小导管注浆法则力有不逮;水泥搅拌桩和小导管超前支护联合应用可以有效降低软土中地下工程开挖引起的地层变形和工程造价,且变形的大小取决于加固后土体的整体强度;当强度达到某一值后,开挖进尺的影响大于支护时间的影响,否则相反。据此,可以合理安排开挖工法和步骤,缩短工期。

A case of reinforcement and excavation of a subway cross-passage in alluvial soft soil at the Pearl River Delta is studied, for which the 3D finite element model is used to simulate the excavation process under the different reinforcement options of a deep mixing pile or advance grouting condulet, and the crown displacements of the cross-passage under different options are calculated and analyzed. The results show that the deep mixing pile is highly adaptable and may strengthen the soil and control excavation deformation by different proposals, while the advance grouting condulet is incompetent. A combined application of the cement mixing pile and ad- vance grouting condulet can efficiently reduce construction costs and ground deformation caused by the excava- tion of underground works in soft soil. The magnitude of deformation depends on the overall strength of the soil mass after reinforcement, and the affect of advance rate on deformation is greater compared with that of support time if the strength of the soil mass reaches a certain value, otherwise the opposite is true. For these reasons, the excavation method and procedure can be rationalized to shorten the construction time.