Innovative solution: soil cement column walls as a temporary retaining structure for excavation in soft Bangkok clay

Abstract

The installation of temporary retaining walls for excavation activities is considered a crucial and costly aspect in the realm of geotechnical engineering construction. Several past studies have been undertaken on the stability aspects of the deep mixing method for soil–cement column walls in soft Bangkok clay are available. However, there has been a lack of research focusing specifically on the relationship between execution time, cost, and stability of these walls, a topic on which this study is focused. The principal aim of this research was to investigate and make a comparative analysis of the stability, construction cost, and construction duration of retaining walls under varying construction site conditions. This study placed particular emphasis on shallow excavation conducted in the context of soft Bangkok clay, and its focus was to determine the most effective construction management strategies within the given contextual parameters. The investigated wall systems comprised of soil–cement columns (SC), stiffened soil–cement columns (SSC), and sheet pile walls. The SC had a diameter of a diameter of 0.6 m, while the SSC was composed of an embedded steel pipe with a diameter of 0.2 m (SSC-IRow Wall). The stability of the walls under investigation was assessed through the utilization of finite element (FE) simulation. The finite element model was initially calibrated through a comparison between the simulation results and the data obtained from field measurements. For a 4.5 m deep excavation with a required factor of safety > 1.3, the SCC and SSCC Walls were found to have an advantage over the conventional sheet pile wall. The SC Wall, consisting of two rows and measuring 7 m in length, demonstrated superior efficiency in terms of both time and cost, regardless of whether it was implemented in unconfined or confined construction sites. The utilization of the SSC-IRow Wall was suggested as an alternative in cases where the use of a thick SC Wall was prohibited. A systematic approach for the selection and design of the SC and SSC Wall systems was proposed, drawing upon a thorough examination and evaluation of the study findings. The results of this study possess the capacity to be utilized in excavation endeavors encompassing diverse depths in the context of soft Bangkok clay and comparable soil conditions.