Experimental Study On Mechanical Properties And Long-term Deformation Of Soda Residue Soil Under Complex Stress Conditions

Soda residue(SR)is a kind of industrial wastes produced in the process of soda with the method of ammonia-soda.Applying SR to backfilling not only solves the problem of land occupation and environmental pollution,but also saves material cost for foundation engineering.The mechanical properties and long-term deformation of soda residue soil(SRS)under complex stress conditions are the key point to be solved in the engineering application of SRS.Multiple soil tests were performed on the undisturbed SRS of Tianjin Port.Then,the mechanical properties and long-term deformation of SRS were discussed.In final,the predict models of strength and long-term deformation for SRS based on the results of tests were proposed.The main contents and conclusions of this paper are as follows:(1)Conventional soil tests were performed on the SRS of Tianjin Port.Then,the basic physical and mechanical properties of SRS were analyzed.It is found that SRS is characterized by high water content,large pore ratio,low density,high liquid and plastic limit,high compressibility,poor plasticity and permeability.SRS belongs to fine inorganic soil,and can be further divided into high liquid limit silty according to casagrande plastic map.SRS’s spescial properties should pay attention on When apply it to engineering.(2)Static triaxial compression tests were performed on the undisturbed SRS of Tianjin Port.Then,the shear properties of SRS under different consolidation conditions were discussed.Meanwhile,a structural strength model(SSM)based on Mohr-Coulomb theory was proposed.SSM reflects the influence of soil structure on undrained strength,and divides the undrained strength into two parts: friction strength and original structural strength.Friction strength characterizes the magnitude of friction between soil particles.Original structural strength represents the structural effect on soil strength.On this basis,the SRS strength model was established by combining the test results with SSM.The SRS strength model can effectively predict the undrained strength of undisturbed SRS in Tianjin Port under different consolidation conditions.(3)Dynamic triaxial compression tests were performed on the undisturbed SRS of Tianjin Port.Then,the dynamic properties of SRS under different stress conditions were discussed.It was found that the double-power function model can describe the non-monotonic changes of the cyclic pore pressure and cumulative strain of the overconsolidated soil under the dual effects of cyclic compression and dilatancy.Meanwhile,the structural equivalent overconsolidation model which considering the structural influence was proposed based on Yasuhara equivalent overconsolidation model.The cyclic pore pressure model of SRS was added into the structural equivalent overconsolidation model,and the post-cyclic strength model of SRS was obtained.(4)Long-term deformation tests were performed on the undisturbed SRS of Tianjin Port.The long-term one-dimensional consolidation deformation of SRS under different stress conditions were analyzed.Based on the test results,the predict model of long-term one-dimensional deformation deformation for SRS are established.The predict model of long-term one-dimensional deformation was applied to the road engineering in Tianjin Port,and the long-term settlement of the SR foundation were predicted.