Soil Displacements due to Tunneling in Dense Silty Sand Layer Underneath Bridge Pile Foundation in Bangkok

Abstract

A tunnel was bored by means of EPB shield in dense silty sand layer about 27.5 m below ground surface in Bangkok. The main route of the monitored tunnel is located underneath a bridge and busy roads. Several factors including soil parameters, surcharges, and obstructions play an important role in obtaining an accurate estimation of soil movements in response to tunneling. This research aims to demonstrate the use of elasto-plastic failure criteria of Mohr Coulomb soil model to back-simulate the ground surface and subsurface settlements. The two-dimensional (2D) numerical analyses were carried out to confirm the design assumptions, Young Modulus. The settlements yielded by the numerical method were similar to the field monitored data at both ground surface and subsurface. The results based on empirical method for surface settlements were also acceptable. In short, the back-simulation and analysis of this study and those of the previous projects of tunneling provide an accurate prediction for future tunnel excavation with similar geological conditions.