Physical-Mechanical Properties Based On Two-Phase Model Of EPS Beads-Mixed Lightweight Soil

Technologies to generate wastes into resources are receiving increasing attention around the world with the continued depletion of natural resources and emphasis on the environment conservation. EPS (Expanded Polystyrene) beads-mixed lightweight soil is one of them.EPS beads-mixed lightweight soil is a lightweight soil formed by mixing original soil with EPS beads, solidification agents and water. It can be used to reduce the environmental pollution. Furthermore, due to its intrinsic low self weight, it has also been adopted in improving the foundation stability and reducing the ground settlement. This soil has promising future due to its advantages such as light weight, high strength, self-standing, short project execution time, re-utilization of surplus soils, and environmental friendliness. However, to make full use of this soil, more study is needed since the research on this soil is still in its infancy in China. In this dissertation, the lightweight mixture specimens were prepared by treating dredged silt with cement and EPS or WEPS (waste expanded polystyrene). Based on the view of composite materials, laboratory tests were conducted to investigate density property, deformation property and strength property of the EPS beads-mixed lightweight soil. The main content can be summarized as follows:1. Two-phase Model StudyEPS bead-mixed lightweight soil is formed by mixing original soil with solidification agents, lightweight materials and water. The original soil is solidification treated and lightweight treated. It is a composite material comprised of solidified soil and lightweight EPS. Two-phase density model and two-phase strength model were proposed based on the elasticity and the principles of soil mechanics.2. Study on Density PropertyBy density tests, the influencing factors on the density were identified. The density is found to be mainly affected by the EPS volumetric ratio while the effects of the curing period, the cement content and the type of lightweight material were negligible. Based on the results, the two-phase density model was verified, and its simplified version was proposed for engineering design.3. Study on Deformation PropertyThe failure mode, failure strain and deformation modulus were studied by the direct box shear test and unconfined compression strength test.4. Study on Strength PropertyThe shear strength of EPS beads-mixed lightweight soil is an important property in engineering design and analysis. Direct box shear tests were conducted to obtain the shear strength parameters, namely the cohesion and the friction angle. The effects of the cementcontent, the EPS volumetric ratio and the curing period on the shear strength parameters were established. Moreover, attempt was made to explain the strength parameters based on the two-phase strength model.