Effect of polypropylene fiber inclusion on the compressibility and consolidation characteristics of dredged marine soil

Abstract

Dredged marine soil (DMS) is a geo-waste that was produced during maintenance dredging. It is unlikeable to the geotechnical engineer as the soil is weak and low in bearing capacity. However, the poor engineering properties of DMS can be improved by soil reinforcement. So far, there has been little quantitative analysis of high water content DMS in terms of compressibility and consolidation. Hence, this experimental study evaluates the effect of PP fiber on the compressibility and consolidation behaviors of DMS. Different water contents (ranging from 0.90 to 1.46 times the liquid limit of the soil), type of soil (ML and MH), and fiber contents (0–1.00% by dry weight of soil) were chosen as the experimental variables in this research. A series of one-dimensional consolidation tests by using conventional oedometer were conducted on the reinforced DMS to determine the compressibility and consolidation characteristics such as compression index (cc), coefficient of consolidation (cv), coefficient of volume compressibility (mv), and soil constraint modulus (D). From the study, in term of compressibility, DMS admixed with 0.5% of PP fiber has resulted in lower consolidation settlement and high stiffness than DMS with 1.0% of PP fiber. Hence, it is suggested that 0.5% of PP fiber in DMS is the optimum content. As for consolidation, the cv values are in the range of 0.05–0.5 and 0.5–10 m2/year, which classify the soil in the range of high plasticity clay and low-medium plasticity silt, respectively. Although the results show that the addition of PP fiber in DMS has improved the soil, however, it is not substantial. Therefore, it is recommended to use higher content of PP fiber or admixed the soil with a binding agent such as cement to enhance the weak and high water content of DMS.