Innovative Approaches to Soft Clay Stabilization: Utilizing Sustainable Materials for the Stone Column Technique

Many coastal areas have soft clay soils, characterized by high compressibility and low bearing capacity. There are several methods for improving soil characteristics, one of which is stone columns technique. This method can reduce the possibility for liquefaction, speed the consolidation effect, strengthen the soil, and lessen the compressibility of soft, loose, and fine-graded soils. In this study, unit cell stone columns with 50- and 75-mm diameters and the length of stone column to the depth of the soft clay (L/H) of 1 and 0.75, were subjected to laboratory experiments on soft clay soil with a cohesion of 7 kPa. Crushed asphalt, crushed concrete, crushed ceramic, dolomite, and treated concrete were tested as filler materials in the stone columns. In addition, tests were conducted on both unreinforced and geogrid-encased stone columns. The main objective is to identify the most effective filler material that improves in load-bearing capacity and minimizes the settlement. The behavior of stone columns was assessed by varying stress concentration ratio (n) and the load improvement factor (LIF). The results indicate that both n and LIF increase with increasing the settlement to the plate diameter ratio, reaching a stable value when that ratio reaches 10% or higher. Consequently, it can be inferred that using floating stone columns is more economically efficient than using end-bearing stone columns. Increasing the length and reinforcing the vertically encased stone columns improve both the bearing capacity and the stress concentration ratio. All the materials used in this study improved the bearing capacity and reduced settlement. It is observed that treated concrete yielded the best results in improvement, while crushed asphalt is considered the most economical option compared to the other materials used.