Studying On The Rheological Mechanics Characteristics Of The Accumulation Gravel Soil By Virtual Test

Accumulation of gravel soil is a kind of soil-rock mixture. Its compositionfactors are extremely complex, which was mainly constituted by weathering,unloading, alluvial, deluvial, etc. The deformation mechanism of soil-rock mixturenot only depend on space between soil and rock but also depend on the soil andcrushed stone’s contact state and their relative motion. Furthermore, its stress-strainrelationship and deformation failure mechanisms is diffent from normal soil and rockbecause of talus deposit is made up of weak parent soil, stiff macadam or rock blocks.Slope and landslides consist of accumulation gravel soil exist in the China widely,Sliding slope due to rainfall or engineering activities resulting in huge economiclosses and make personnel injuries or deaths.But current research on accumulation ofgravel soil is still confined to a particular project. This article is depended on thelaboratory test of accumulation gravel soil which collected from Zhaoshan area,several conclusions are putted forword in the following:1. Based on the discrete element software PFC2D, author had generated arbitraryshape stone block in Fish language. And author realize the accumulation gravel soilmesoscopic parameters calibration by changing the parameters. Compared withlaboratory test, the founded model can represent the shear failure process of soil-rockmixture accurately,2.The bigger friction coefficient of soil-rock mixture the greater internal frictionangle, the stronger shear strength of gravel soil, and the softening characteristics andthe dilatancy more obvious, so do the residual strength and the axial deformation.When the friction coefficient increased by0.1, the peak deviator stress averageincreased118.85kPa and the residual strength average increased90.44kPa..With theincrease of friction coefficient, diluvial gravel soil’s cracks develop from the singleshear to the shear zone. Apart form the influntion of the soil-rock particles’ surfacefriction, the shear strength of diluvial gravel soil is related to embedding between soiland crushed stone. Moreover the bite force between particles play a major role whenthe axial strain reaches a certain value.3. As the confining pressure of laboratory test and virtual test insreased, the shearstrength, internal friction angle, residual strength and the initial tangential modulusincreased, and so do the softening phenomenon of later test and the non-uniformity offorce chain between soil and rock. When the confining pressure is small, bulk straintransform from the shear shrinkage to dilatancy quickly during the trial. With the increase of confining pressure, the volume strain will be increased, and dilatancyphenomenon can not be happened until large axial strain has been occurred.4. Young’s modulus is proportional to the soil-rock material rigidity. As the peakvalue of principal stress difference of material and the initial tangential strainincreased, axial strain of shear failure decreased. Young’s modulus does not play asignificant role on residual strength. When young’s modulus is small, gravel compressand overlap between soil particles increase, showing obvious decrement phenomenon.In addition, the greater bond strengh the smaller axial deformation is and whencohesive force is too big, particles are squeezed in its center instead of tangential slip.5. The rheological virtual simulation test of gravel soil showed that exponentialfunction can precise fitting the axial rheological and volume change of diluvial gravelsoil. Axial flow and volume of gravel soil rheology showed significant nonlinear, andthe nonlinear degree increase with deviator stress and rheological time. Cell pressurehas a strong impact on the axial rheological, axial flow is smaller the greater theconfining pressure. And later in the loading process confining pressure effect on axialdeformation increased with the increase of the axial pressure increase.