Experimental Research On Shear Mechanical Properties Of Sand-concrete Interface

The interaction between soil and structure is commonly happened such as pile andsurrounding soil, retaining wall and backfill, underground tunnel structure andsurrounding soil. The simulation of the interaction is important for accurately forecastthe behavior of the structures under various loads.In this study, firstly, a series of direct shear tests of sand-concrete interface underconstant/varying normal stress were conducted by the Shear Trac-?largedirect shear apparatus. The test results indicate that the shear stress-shear displacementcurves of the loose-concrete and dense sand-concrete interface in the process ofmonotonic shear under constant normal stress show strain-hardening andstrain-softening characteristics, respectively. In the process of cyclic shear underconstant normal stress, the relationship between shear stress and shear displacement ofthe loose or dense sand-concrete interface all present line relationship duringunloading?while the shear stress-shear displacement curves of the loose-concreteinterface and dense sand-concrete interface show strain-hardening characteristics afterunloading and begin to reverse shearing. The test results also indicate that the shearstress-shear displacement curves of the loose/dense sand-concrete interface showstrain-hardening characteristics under the second normal stress in the process ofmonotonic shear under varying normal stress.Then, a mathematical analytical model was developed to fit the relationshipbetween shear stress and shear displacement for different sand-concrete interface andshear conditions. The results based on this model indicate that the relationship betweenshear stress and shear displacement for loose sand-concrete interface subjected to constant normal stress during the monotonic shear condition can be fitted withhyperbola curve, and that for dense sand-rough concrete and dense sand-smoothconcrete interface in the same conditions can be fitted with tri-linear, and bi-linearcurves, respectively. However, In the process of cyclic shear, the relationship betweenshear stress and shear displacement for loose/dense sand-concrete interface subjected toconstant normal stress were fitted with hyperbola and straight line in different stages.Furthermore, In the process of monotonic shear under varying normal stress, therelationship between shear stress and shear displacement of loose sand-concreteinterface can be fitted with piecewise hyperbola and that of dense sand-concreteinterface can be fitted with tri linear broken line and hyperbola in different stages.Finally, the FRIC subroutine has been programmed according to the mathematicalmodel for the loose sand-concrete interface. The development of the negative skinfriction and the neutral plane depth during the consolidation of soft soils was analyzedbased on this model.