Study On The Mechanical Properties Of The Mixed Lightweight Soil Made From Sea Silt And Construction Waste Adding Phosphate Tailing Sand

The sea silt soft has some characteristics as big rheological property, high compressibility and low bearing capacity. When building embankment on it, drainage and consolidation treatment must be used, and construction period is long relatively. According to the characteristics of the sea silt soft, this study comprehensive utilization of Lianyungang’s three solid wastes:sea silt, lightweight construction waste and phosphate tailing sand in mixed lightweight soil. The mixed lightweight soil changed wastes into valuable materials and protected environment. It had the general features of the mixed lightweight soil:lightweight and high strength. In addition, because the lightweight insulation wall materials were strong water absorption, when the moisture rate of sea silt is less than 100%, the sea silt could be mixed directly without draining. Therefore, the mixed lightweight soil of sea silt and construction waste should be popularized vigorously.This study was based on laboratory testing, the mechanical properties of this lightweight soil were studied and the conclusion was drawn as follows:1. This paper discussed the preparation method of the mixed lightweight soil specimens in detail, and analyzed the technical feasibility of the mixed lightweight soil that was made of sea silt and lightweight insulation wall materials, solidified with cement and adding proper phosphate tailing.2. The factors influencing density and strength of the mixed lightweight soil specimens were analyzed. The experiment results showed that the main factors affecting density were amounts of light construction waste and phosphate tailing sand:with the increasing amount of lightweight construction waste, the specimens’ density decreased; with the increasing amount of phosphate tailing sand, the specimens’density decreased. The main factors affecting strength were amounts of cement, lightweight construction waste and phosphate tailing sand:with the increasing amount of cement, the specimens’strength increased; with the increasing amount of lightweight construction waste, the specimens’strength first increased and then decreased; with the increasing amount of phosphate tailing sand, the specimens’strength first increased and then decreased. The main factors affecting the ratio of strength and density were amounts of cement, lightweight construction waste and phosphate tailing sand:the rule was consistent with variation of the strength. Moreover, two kinds of ratio formula were provided in the cases of adding and not adding phosphate tailing sand.3. By experiment of consolidated undrained triaxial shear tests (CU) and consolidated drained triaxial shear tests (CD), the mechanics characters and the influencing factors of the lightweight mixture soil specimen were amounts of lightweight construction waste, cement and phosphate tailing sand confining pressures. The stress-strain relationship is of two kinds of morphologies of hardening and softening. The shear strength parameters and their influencing factors of the mixed lightweight soil were studied and the regular pattern of strength parameters was properly explained with the material structure.4. Through the research of the micro and fine structure, the strength of the mixed lightweight soil came from the cementing action of sea silt-cement composite binder, the packing effect of lightweight construction waste and the supporting role of phosphate tailing sand. This study linked the microstructure and macro strength to prove that the internal micro crack in the mixed lightweight soil specimens occurred in the interface of the lightweight construction waste particles and the cement stabilized soil.5. A double-exponential constitutive model was founded to satisfy simultaneously the hardening and softening morphologies of stress-strain relationship. The double-exponential constitutive model was simple with only three parameters:a and b, c. The fitting precision of the model was expressed with correlation coefficient and root mean square deviation. The fitting precision and the parameter sensitivity were analyzed.