Research On Physical-Mechanical Properties Of Fiber EPS Foamed Bead Light Soil

Due to the excessive fill load or Insufficient bearing capacity of foundation,some engineering problems are easily to occur during engineering construction,such as soft ground settlement,road widening differential settlement,and unstability of retaining wall.EPS(Expanded Polystyrene)foamed bead light soil featuring with light weight and high strength can be used as fill material to reduce upper fill load,which provides a new technical measure to solve engineering problems;moreover,the environmental-friendly waste foam EPS is conductive to environment protection,therefore researches on this material is of great actual significance.EPS material enjoys sound elasticity and has significantly different property compared with soil.The failure of EPS foamed bead light soil features with Loose fragmentation and appears as sudden brittle failure,which restricts its widely application.Therefore,the fiber EPS foamed bead light soil of improved performances has become a new research focus.In this paper,EPS foamed bead fiber light soil was prepared using modified polypropylene fiber as reinforcement material.Moreover,its physical and mechanical properties were systematically studies via a series of laboratory tests.(1)The density performance of fiber EPS foamed bead light soil.Through density tests,it can conclude that the density is mainly determined by the incorporation ratio of EPS foamed beads,the most effective method to adjust density is to change the incorporation ratio of EPS foamed beads.A density model was established,of which the feasibility was verified.(2)The strength characteristics of fiber EPS foamed bead light soil.Through unconfined compressive strength test,it can conclude that the most important influence factors of strength are the incorporation ratio of EPS and cement,the incorporation ratio of fiber content is secondary factor;the optimum incorporation ratio of fiber was 0.3%;The empirical formula of strength was built.(3)The prescription design of fiber EPS foamed bead light soil.Based on empirical formula of density and strength,the mix proportion design method was put forward,the concept of specific strength was introduced,the optimization method of mix proportion scheme was put forward.(4)The Strength mechanism of fiber EPS foamed bead light soil was researched.matter components and microstructure of light soil were studied by XRD(X-ray diffraction)test and SEM(scanning electron microscopy)test,and its mechanism of strength was revealed.(5)The deformation characteristics of fiber EPS foamed bead light soil:(a)Through unconfined compressive strength test,we made comparative analysis on the uniaxial stress-strain characteristics and failure mode between non-fiber light soil and fiber light soil.Fiber enhanced the integrity and toughness,improve performances of light soil.In addition,the correlation between deformation modulus and compressive strength was established,and the failure mode of sample was analyzed.(b)The compression characteristic of the light soil was analyzed through consolidation test.We explored the reasonability of introducing conventional consolidation theory analytical methods into the study of light soil,and proposed e-p curve and e-logp curve were not suitable for describing fiber EPS foamed bead light soil,instead,?-p curve and ?-logp curve were good replacement for describing light soil.fiber EPS foamed bead light soil is a structural soil,when the stress is lower than its structural yield stress,the compressibility of EPS foamed bead fiber light soil is very small.In addition,we investigated the change rules of structural yield stress Py and compression modulus Es1-2,explored the relation of Settlement-time.(c)The stress-strain-pore water pressure characteristics of fiber EPS foamed bead light soil was studies through triaxial consolidated undrain(CU)test.There are two types of stress-strain relation: strain hardening and strain softening,and they are decided by cemention structure and confining pressure,the incorporation ratio was the internal cause,while confining pressure was the external cause.The change of pore water pressure was closely related to the internal cementation structure of mixed soil and confining pressure.The change rule of pore pressure coefficient was analyzed.(d)Stress-strain-volume deformation characteristics of fiber EPS foamed bead light soil were researched by triaxial CD(consolidated drained)test.It is similar with triaxial CU test,there are two types of stress-strain relation: strain hardening and strain softening,and there are two types of volume deformation characteristics: shear dilatancy and shear contraction,all these are decided by cemention structure and confining pressure.(6)Shear strength characteristics of fiber EPS foamed bead light soil.failure criterions,strength envelope,shear strength index,and failure mode of mixed soil were systematically studied by triaxial CU test,triaxial CD test.The contacts and differences between different kinds of failure criterions were analyzed.The ralation of strength index and incorporation ratios was investigated.(7)Study on the constitutive property of fiber EPS foamed bead light soil.In this paper,we extracted the Duncan-Chang model parameters of fiber EPS foamed bead light soil,calculated the theoretical curve of stress-strain-volumetric strain,and verified the feasibility of Duncan-Chang constitutive model by comparing the modeled results with measure results.The innovative points of this paper are as below:(1)Based on empirical formula of density and strength,the mix proportion design method and optimization method were put forward.(2)The matter components and microstructure were systematically studied,its mechanism of strength was revealed.(3)The macro-mechanical properties and the laws were systematically studies.