Case study: Design optimization and field tests of a large geotextile mat cofferdam combined with steel sheet piles

Abstract

A case study on a large geotextile mat cofferdam combined with steel sheet piles was conducted using field testing and numerical simulation to optimize the design and assess its performance. The failure mechanism and overall stability were investigated by numerical simulation, considering potential influence factors, including pile length, width ratio ($W_{\text{2}}/W_{\text{1}}$), water level, and excavation depth. The width ratio was identified as a critical influencing factor. Specifically, an optimized ratio of $W_{\text{2}}/W_{\text{1}}=0.6$ demonstrated the best overall performance. When the steel sheet pile intersects the potential failure surface, the stability improvement is most significant, particularly with a length of 15 $m$ in the current case. Field tests were employed to examine the performance of the optimized cofferdam design. Water level fluctuations, surface displacements, and both horizontal and vertical displacements at various depths were monitored to assess the cofferdam’s behavior. Results from both numerical simulations and field monitoring conclusively affirm the cofferdam’s capability to meet stringent safety criterion during the construction and operational phases. This work fills gaps in standardization of large geotextile mat cofferdam design by providing guidance on geometric configuration, reinforcement integration, and soft soil risk management, thereby advancing engineering practices for similar projects.