Experimental Study On Strength And Dilatancy Characteristics Of Sand-Tire Crumbs Lightweight Mixtures

The application of old tire resources to civil engineering can not only address growing environmental and economic concerns,but also help solve geotechnical problems related to the strength,deformation and stability of soils,such as soft ground treatment,lightweight fill behind high retaining walls and landslides protection engineering,etc.In this paper,the tire crumbs obtained by mechanically chopping old tires are used to investigate the effects of tire content,tire particle size and effective confining pressure on the strength and dilatancy characteristics of sand-tire crumbs lightweight mixtures through a series of drained triaxial tests.The major contents and conclusions are as follows:(1)To investigate the effect of tire content on the strength and dilatancy characteristics of the mixtures,five groups of comparative tests for mixtures with different mass percentage content of tire crumbs(0%,5%,10%,15% and 20%)and five groups of comparative tests for mixtures with different volume percentage content of tire crumbs(0%,5%,10%,15% and 20%)were conducted.By comparing the test results,it is found that the shear strength,dilatancy,initial stiffness and post-peak strength loss of sand-tire crumbs mixtures decrease with an increase in tire content.The peak friction angle and maximum dilatancy angle decrease with increasing the tire content,while the axial strain corresponding to peak-state deviatoric stress increases with an increase in tire content.(2)In order to study the effect of tire particle size on the strength and dilatancy characteristics of the mixtures,four groups of sand mixed with TC1(2.36-3.0mm),TC2(2.36-3.0mm),TC3(2.36-3.0mm)and TC4(2.36-3.0mm)were tested.Through comparative experimental analysis,it can be concluded that the initial shear stiffness of the mixture increases with increasing the average size of tire particles.The larger the size of tire particles in the mixture,the higher peak strength could be obtained at smaller axial-strain level.The peak-state friction angle and dilatancy angle of the mixture also increase with increasing the average particle size of tire crumbs.(3)To study the effect of effective confining pressure on the strength and dilatancy characteristics of sand-tire crumbs mixtures,four groups of tests under different effective confining pressures(0.1 MPa,0.2 MPa,0.3 MPa and 0.4 MPa)were carried out.The experimental results show that the mixtures can obtain higher peak-state stress at relatively large axial strain level with an increase in the effective confining pressure in the test.Besides,increasing the effective confining pressure can increase the overall shear stiffness of the specimen.However,the peak friction angle and dilatancy angle decrease with an increase in effective confining pressure.It is found that the Bolton's dilatancy equation proposed for pure sand is also applicable to sand-tire crumbs mixtures.The slope of this equation,i.e.,the dilatancy coefficient can hardly be affected by the tire content in the mixture and the effective confining pressure.However,the intercept of the equation(the critical state friction angle)decreases with an increase in tire content.