Experimental Study On Mechanical Properties Of Foamed Mixture Lightweight Soil Using River Sludge

A lot of sludge is deposited below our country’s vast waters,and in order to ensure the smooth river and clean water,the number of dredged sludge every year is amazing.To achieve the purpose of recycling,making waste profitable,improved soil using dredged sludge as raw material applied to practical engineering,can not only provide a feasible and effective way for sludge treatment,but also provide a reliable guarantee for the growing demand for engineering soil.Sludge air foam mixed light soil as an improved treatment method of dredged sludge,is a lightweight soil mainly used cement as curing agent,added into air foam as lightweight material,formed after a certain process flow,holding obvious characteristics in aspects of soil bulk density,mobility,strength,deformation,economic,environmental protection and so on.In this paper,the Foamed Mixture Lightweight Soil Using River Sludge(FMLSS)was made by using dredged sludge from a river in Suzhou as raw soil,cement as solidified material and foamed air as lightweight material,and based on the laboratory experiments,its physical and mechanical properties were studied:(1)Basic physical properties: the density and permeability of the FMLSS were studied by density test and penetration test.The density can be reduced to about 1.05 g/cm3 by adjusting the content of each component in the mixed soil,which proves that adding foamed air as lightweight material is a feasible way to reduce the bulk density of the soil;the permeability coefficient can reach the standard of general clay,and basically maintain at the same order of magnitude with changes of cement incorporation ratio,foamed air incorporation ratio,water content and curing age,proving a good anti permeability performance of FMLSS.(2)Strength characteristics: via unconfined compressive strength test,static triaxial test(UU)and standard consolidation test,the mechanical properties of the FMLSS were studied.The main factors affecting the strength of mixed soil are cement incorporation ratio,foamed air incorporation ratio,water content and curing age;the unconfined compressive strength has an exponential relationship with cement incorporation ratio,foamed air incorporation ratio and water content and a hyperbolic relationship with curing age;the strength and stiffness of the 28 d curing time can be used as a mechanical property index for design and construction;the shear strength mainly consists of the adhesion and friction components,and the cohesive strength and the friction angle are more affected by the cement incorporation ratio.(3)Deformation characteristics: soil deformation mainly experiences four stages of compaction,elastic deformation,plastic yielding and failure;the relationship between failure strain and each component obtained by tests can be used as the basis for deformation control in engineering;Duncan-Chang model is in line with the changes stress strain curve of unconfined compressive strength and static triaxial,and can reflect the nonlinear characteristics of FMLSS.(4)Relationship between microstructure and macroscopic mechanical properties: the internal microstructure characteristics of FMLSS can be quantitatively analyzed by using mercury intrusion porosimetry(MIP),and the obtained parameters characterizing of soil microstructure characteristics of pore volume ratio K and pore size distribution coefficient of Cu have a good correlation with FMLSS’s strength and deformation;based on the analysis of correlation in microstructure and mechanical properties,it can further reveal the failure mechanism of FMLSS,and provide the basis for the optimization of the proportion of FMLSS.