Assessment of the Optimal Ratio of By-product Slag or Traditional Crushed Aggregate in a Replacement Mixture for Soft Soil Improvement and Optimal Replacement Thickness

摘要

The sustainable use of a byproduct, such as steel slag coarse aggregate (SSCA), mixed with soil at a certain percentage of the dry weight of the same soil as a replacement mixture to improve soft soils in Egypt was studied. Using partial replacement in practical engineering has improved shallow soft soil deposits to reduce excessive settlement when subjected to excess load and increase its low bearing capacity. This technique will minimize the negative effects of byproducts on the environment and reduce the use of natural materials, such as traditional crushed stone aggregate (TCSA). This technique also can be economic. Recently, the utilization of waste and recycled materials as a sustainable source of permeable material must be developed to improve problematic/soft soils. This research presents a suggested technique to improve soft soil collected from a failure site in Alexandria, Egypt, under an excess store load as a case study. A comparison between SSCA and TCSA in replacement mixtures with different mixture ratios and thicknesses was performed. This study adopted a top replacement mixture layer with different mixture ratios and thicknesses experimentally to optimize these parameters. The results of the treatment for improved shallow soft soil layer deformation and strength are compared. The study results show that using SSCA mixed with air-dried soil as a partial replacement top layer significantly improved the compressibility, soil index properties and strength of this shallow soft soil layer compared with using the TCSA mixture at the same replacement percentage and same thickness. Notably, the optimal percentage of SSCA in a replacement mixture does not exceed 50 of the air-dried natural soil, and the optimal thickness corresponds to a 0.80 footing width/diameter ratio. Back analyses of the case study were performed using a numerical axisymmetric footing soil model in PLAXIS to verify the laboratory experimental results and highlighted the reduction in long-term deformation problems. The numerical and experimental results agree closely. The utilization of massive industrial waste provides sustainable soil improvement and is environmentally friendly.