Study On Mechanical Properties Of Reinforced Construction And Demolition Of Materials

With the development of society and the rapid increase in population,the automobile industry,transportation industry and construction industry continue to advance while a large number of natural resources are being consumed,accompanied by a large amount of solid waste.The risks caused by solid waste is huge,such as encroachment on soil,polluted water,air and waste of resources.How to reduce risks has become a global challenge.Waste tires have light weight,high strength and stable performance and there is great potential for construction and demolition of waste.In recent years,they have been widely used in road geotechnical engineering.At present,there are few studies on reinforced construction and demolition of waste in China,and there is a lack of related research on construction and demolition of waste reinforced with tire,which is not conducive to promote the application of construction and demolition of waste and waste tires in geotechnical engineering.Considering the effects of confining pressure,particle gradation,and sand contents,the stress-strain,volumetric change,modulus,and energy absorption capacity were studied through large-strain static triaxial tests.Moreover,the constitutive model of construction and demolition of material was discussed.Comprehensive analysis demonstrates that the optimal form of construction and demolition of material is used as the roadbed filler.Construction and demolition of material reinforced with biaxial geogrid and micro-tire were used as fillers.Large-strain dynamic triaxial tests were carried out to study the axial cumulative deformation,development of excess pore water pressure,dynamic stress-strain,and dynamic elastic modulus of unreinforced soil,unreinforced construction and demolition of material,and reinforced construction and demolition of material.Moreover,the model for predicting the cumulative axial deformation within 10 cycles and over 10 cycles of construction and demolition of material under different reinforced forms was discussed.Finally,the interface behaviour between construction and demolition of material and waste tire strip are studied.This paper conducted pull-out test to evaluate interface behaviour,including the relationship between the pull-out load and displacement,the strength parameters of the interface between the reinforcement and construction and demolition of material,the relationship between the tensile strain of the reinforcement and displacement,the interface friction resistance and relative displacement,and the influence of the number of transverse ribs of waste tire strips with steel wires on the interface strength.The main conclusions of this topic are as follows:(1)Under lower axial strain,the peak stress of 20 mm construction and demolition of material is greater than that of 40 mm construction and demolition of material.With the increase of axial strain,the peak strength of 40 mm construction and demolition of material gradually increased.When an appropriate amount of sand is added to 40 mm construction and demolition of material the soil changes from obvious strain hardening and contractancy to weak strain hardening and dilatancy.Moreover,under a smaller axial strain,the peak strength of the 40 mm construction and demolition of material increased.According to the analysis of shear strength parameters,when the mass percentage ofconstruction and demolition of material is 40-60%,the shear strength of mixtures is the highest.The fitting results of Duncan-Chang model show that the model is not suitable for construction and demolition of material.On the contrary,the modified power-law model can better reflect the strain softening,hardening,dilatancy and contractancy behaviour of construction and demolition of material.From the perspective of indoor basic tests,ecological environment,and economic costs,it is recommended to use 20 mm construction and demolition of material in road geotechnical applications.(2)The number of cycles and the amplitude of dynamic stress have significant effects on the dynamic properties of sand,unreinforced construction and demolition of material,and reinforced construction and demolition of material.The dynamic performance of construction and demolition of material reinforced with tires and biaxial geogrid is significantly different.The results of the axial cumulative deformation of each sample are in accordance with the stability theory.When the confining pressure and the numbers of cycle are constant,the estimated value of the critical dynamic stress of unreinforced construction and demolition of material is higher than that of unreinforced sand.The reinforcement effect of the top tire is better than that of the bottom micro tire.The reinforcement effect of two-layer tires is not obvious.The model for predicting the axial cumulative deformation of construction and demolition of material is suitable for the hyperbolic model within 10 cycles.However,over 10 cycles,the model for predicting the axial cumulative deformation of construction and demolition of material is suitable for the modified Monismith model.Outside the range of plastic stability,the excess pore water pressure changes greatly.Within the range of plastic stability,the axial cumulative deformation almost stops,and the excess pore water pressure gradually stabilizes.For coarse-grained filler,three-dimensional tire is better than two-dimensional geogrid.(3)The biaxial geogrid has poor toughness.The peak strengths under different normal stresses are similar,but the tensile strains are quite different.Compared with biaxial geogrid,waste tire strips with steel wires can play a better role.With the increase in the number of transverse ribs of waste tire strips with steel wires,the interface strength between reinforcement and soil gradually increase.When the number of ribs is 1 and 3,the localized stress of the reinforcement is not obvious,resulting in a constant tensile strain of the reinforcement after the displacement is 20 mm.On the contrary,when the number of ribs is 4,the end bearing resistance of the reinforcement and the frictional resistance are relatively large.The local concentrated stress causes the soil particles in the filler to slide or even break.Relative to the front displacement,the rear end of the reinforcement will produce a hysteresis displacement.When the displacement is small,the friction resistance with uneven distribution of the biaxial geogrid is similar to that of a waste tire strip with no steel wires.As the displacement increases,the interface friction resistance gradually becomes uniform along the pull-out direction.Waste tire strip with no steel wires is different from biaxial geogrid.When the normal stress is high,the interface frictional resistance at the early stage is nonuniformly distributed.When the normal stress is low,the interface frictional resistance during the initial stage is uniformly distributed.When the normal stress is 50 kPa,as the number of transverse ribs increases,the interface frictional resistance changes close to 0,and the lateral resistance increases linearly.With an increase in the number of transverse ribs,the pull-out load of waste tire strip with steel wires gradually increases.Another key fact to remember: waste tire stripwith steel wires,which have high strength,small deformations,and are not easy to fracture,avoid the disadvantages of biaxial geogrid and waste tire strip without steel.