Experimentalstudy On The Engineering Properties Of Lightweight Soil Using Recycled Sludge

Mixed lightweight soil is mainly composed of raw soil, lightweight material, curingagent and water etc. From the viewpoint of environmental protection, lightweighttechnology is to transform the discarded materials, such as dredged silt, constructionwaste soil, waste foam plastics, industrial waste fly ash, waste gypsum, etc., intolightweight soil that can be utilized comprehensively, which can produce goodeconomic benefit, environmental benefit and social benefit. Therefore, it has importanttheoretical and practical significance to develop the technology, which not only cansolve the environment pollution, but also can dispose a large amount of discarded soil,and to transform it into a renewable resource, so as to meet the goals of environmentalprotection and sustainable development.Based on previous researches, this dissertation makes a series of investigations onthe preparation, strength and deformation properties of mixed lightweight soil usingrecycled sludge by means of unconfined compressive strength test, conventionaltriaxial test and direct shear tests. The main results are as follows:(1) The preparation of lightweight soil samples is divided into four steps: weighingmaterial, mixing, mould and curing. Considering the fresh cement has certain porosity,the mixing formula of lightweight soil using recycled sludge. The effect of EPS beadsvolume fraction, cement content and curing age, etc., on the density and unconfinedcompressive strength of mixed lightweight soil, is analyzed using density test andunconfined compressive tests.(2) The effect of EPS beads volume fraction, cement content, confining pressure andcuring age, etc., on the deformation properties of mixed lightweight soil, is analyzed through conventional triaxial compressive test and direct shear test.(3) The direct shear test indicates that the curves of shear stress-shear strain of thelightweight soil using recycled sludge has two characteristics: strain hardening andstrain softening, which mainly depends on the normal stress, EPS beads volumefraction, cement content and curing age.(4) The conventional triaxial test and direct shear test results indicates that the trendsof the p-q or p-S curves of the lightweight soil using recycled sludge is linear and canbe expressed as q mp or S ptan c, where the value of α or c decreaseswith the increase of the EPS beads volume fraction and increases with the increase ofcement content, but has little effect on the value of m and φ.(5) The mainly failure shapes of the lightweight soil samples are: shear failure,drum-shaped damage and compaction shape without significantly damaging surface, ofwhich the failure modes are mainly connected with confining pressure and curing age.