Soil-Cement Screw Pile: Alternative Pile for Low- and Medium-Rise Buildings in Soft Bangkok Clay

Bangkok clay is a soft marine clay with high water content and low bearing capacity. Bored piles installed by the dry process commonly are used for low- to medium-rise buildings in the metropolis. However, the installation of bored piles is time consuming and labor intensive, and requires skillful supervision, quality control, and the disposal of excavated spoils. The soil-cement screw pile (SCSP), a composite piling system which incorporates a soil-cement column (SCC) and a screw pile (SP), is an innovative alternative piling solution. This paper presents the ultimate load, time and cost analysis, and suggested effective design method for this piling system in soft Bangkok clay. The load capacity predictive equations for the SCSP were proposed and validated based on the field static pile load test results. These equations were used successfully for the installation of this piling system in construction projects on soft Bangkok clay. The unit cost of the SP was found to be the highest, and the unit cost of the SCSP and bored pile was found to be the lowest and almost similar. As a result, the application of the full SCSP and bored pile is more economical than the partial SCSP and SP under the same ultimate load design. However, the partial SCSP and SP have more advantages in terms of construction time and are suitable for a time-constrained project. The SCSP has higher efficiency, productivity, and competitiveness than the traditional dry-process bored pile. The outcome of this research will lead to the development of guidelines and a code of practice for SCSP in soft clay, which will be useful for the construction industry, particularly pertaining to the scheduling and cost performance of SCSPs in construction projects. (c) 2020 American Society of Civil Engineers.