Design, Construction, and Performance of Soil Cement Column Walls with Cross Walls for Deep Excavation in Soft Clay: A Case Study of a Road Tunnel

Abstract

This paper presents the design, construction, and performance of a ground improvement system for deep excavations in soft clay, combining soil cement column walls (SCC-W) with soil cement column cross walls (SCC-CW) and buttresses. This method is demonstrated through a road tunnel project built just 2.5 meters from an existing building—one of the few cases where the SCC-W with SCC-CW system has been used as a retaining structure. The paper discusses the design approach, construction methods, and excavation procedures used to control ground deformation and minimize the impact on nearby structures.A comparison is made between results from 3D finite element analysis using the Mohr-Coulomb model and actual field measurements. The results show that combining SCC-CW and buttresses with SCC-W greatly improves stability and reduces soil displacement, compared to using SCC-W alone. In particular, SCC-CW enhances base stability by increasing the factor of safety (F.S.) against basal heave failure. This combined system allows for bracing-free deep excavations in soft Bangkok clay, while also reducing ground movement, construction time, and costs.

Keywords: case study, cross wall, Deep excavation, Soft clay, soil cement column