Experimental Studyof Fibre-Reinforced Clay Soil Mixedwith Municipal Solid Waste Incineration Bottom Ash

Bottom ashes(BA)as a product of municipal solid waste incineration(MSWI),which is non-toxic,stable and active.Mixing with clay can improve the mechanical properties of clay and realize the resource utilization of BA.The thesis takes bottom ash mixed soil(BA-soil)as the research object and intends to use it as roadbed filler.In order to make it better applied in actual projects,it is necessary to improve the shear strength of BA-soil.On the basis of a large number of investigations,the dynamic and static tests of BA-soil with fiber-reinforced were carried out,and its engineering mechanical properties were studied.The research is as follows:The influence of the content and length of polypropylene fiber on the mechanical properties of the BA-soil was studied by large triaxial test.By varying the fiber length and content,the stress-strain relationship and strength characteristics of fiber reinforced BA-soil were analyzed under different confining pressures.The main stress difference and shear resistance of fiber reinforced BA-soil were discussed.The law of strength variation was used to analysis analyse the reinforcing mechanism of fibers during the process of soil shearing.The results demonstrate that the strength and deformation resistance of fiber reinforced BA-soil are significantly enhanced when compared with the clay and BA-soil.The internal friction angle increases slightly,whereas the cohesion of the reinforced soil increases significantly.The sample can reach the maximum strength and have the best reinforcement effect when the fiber length is 2.5 cm and content is 0.3%.At this time,the variation of soil deflection stress is the most obvious.Large-scale direct shear,cyclic shear and post-circular direct shear tests were carried out on 0.3% fiber-BA-soil,the characteristics of cyclic shear and post-cyclic monotonic direct shear under different vertical stress,shear displacement amplitude and degree of compaction were studied.The results show that the shear stress-displacement curves of the direct shear test are weakly hardened before cycle.The shear stress-displacement curves show obvious softening in the monotone shear test after cyclic loading.Cyclic Shear hardening and shrinkage occur in the cyclic shear process under different vertical stresses and shear displacement amplitudes.The hardening degree and shrinkage decrease gradually with the increase of cycle times.With the increase of the degree of compaction,the specimen develops from obvious hardening to softening.The greater compacting degree,the less settlement and smaller shrinkage.Comparing with the results of cyclic and non-cyclic monotonic direct shear,the shear strength,cohesion and friction angle are increased.The addition of polypropylene fibers can form a spatial network skeleton with the BA-soil,so as to increase the resistance to deformation,increase the bearing capacity and reduce vertical settlement.