Experimental Study On Particle Breakage Of Quartz Sand During Shearing

With the rapid development of building technology,construction of large rockfill dams and industrial-civil building have also received more and more attention.As the best holding layer,particle breakage will also occur during use of the sand layer,especially in the pile tip.The particle breakage phenomenon is the most obvious xunder the action of shear stress.In the classical soil mechanics theory,it is assumed that the soil particles can not be crushed,the deformation of the soil is the result of internal pore water removal and particle arrangement reorganization,and the strength theory is established in the intergranular friction and slip.Based on it.However,in practice,when the soil particles are subjected to external stress loads greater than their own strength,partial or total damage will occur.Different materials will have different fracture ultimate stresses,and when the stress is subjected to its own ultimate stress,it will break.Related studies have shown that quartz sand will be significantly broken when it is subjected to about ten MPa.Particle breakage directly changes the soil’s own structure and particle gradation,thereby changing the basic characteristics such as compactness,pore water pressure,and permeability coefficient,thereby further affecting its own strength and changing mechanical properties.Based on the previous studies,this experiment has improved and innovated the experiment,further refined the test,and made the test process closer to reality.In this test,a high-pressure triaxial instrument was used to perform an indoor consolidation drainage triaxial shear test on standard sand,and then a test curve was drawn based on the test record for analysis.The research content of this experiment mainly includes the following aspects:(1)research on the effect of particle breakage during the process of sample preparation and consolidation;(2)research on particle breakage during shearing under the same confining pressure;3)Study on particle breakage during shearing under the same shear strain and different shear strain conditions;(4)Study on the variation of crushing parameters during shearing,including relative fracture potential Bp,overall fracture parameter Bt and relative The fracture parameter Br;(5)the relationship between the relative fracture parameter Br and the stress strain and the relationship with the internal friction angle(p.The experimental research shows that:(1)particle breakage will occur during the sample preparation process,and the amount of crushing can not be neglected;in the process of isotropic consolidation,smaller particle breakage occurs,and the amount of crushing is negligible;(2)When the confining pressure is 2 MPa,the fracture is not too obvious,mainly because the small principal stress direction is less constrained and the intergranular occlusal force is smaller.Therefore,the particle breakage during shearing is not obvious;but as the confining pressure increases,The constraint of small principal stress direction increases,which causes the particles to break obviously during the shearing process;the particles with larger particle size will first break.With the increase of confining pressure,the particle size of the broken particles gradually becomes smaller.Path development;(3)Shear stress is not the only condition that affects particle breakage,and is also affected by shear strain;(4)The relative fracture parameter Br is not only related to confining shear stress,but also closely related to shear strain;(5)The relative crushing parameter Br can be well fitted with the shear strain,and the increase of the relative crushing parameter Br eauses the intermal friction angle φ to decrease.