Experimental Research On Particle Breakage And Strength Characteristics Of Chuanxi Talus Mixed Soil With Different Coarsegrain Contents

In the west of Sichuan,there is a kind of special slope collapse mixed soil,which is made of coarse and fine particles.Due to the unique composition of this mixed soil,particle breakage often occurs under stress,and particle breakage can change the particle size,particle size distribution,degree of compaction,contact stress between particles,etc.,so that redistribution of contact stress between particles is adjusted,the contact pressure becomes uniform,and the effect of dilatancy is reduced,thereby reducing the geomaterials shear strength,resulting in the design of the actual project shear strength lower than the soil's own shear strength,increasing the risk of soil instability,therefore,it is necessary to systematically study the particle breakage of mixed soils in western Sichuan and their strength characteristics after crushing.In this paper,the soil samples with obvious differences in six kinds of coarse-grained contents at different heights in a colluvium-mixed soil in western Sichuan are taken as the research object.Based on the large static coarse particle soil triaxial test equipment,the coarse-grained content of mixed-grained particles is systematically studied.The impact of the shear strength and its crushing on the shear strength,and analysis of the impact mechanism.The main achievements and conclusions of this paper are as follows:First of all,six kinds of soil samples were subjected to routine physical tests,including screening tests,natural moisture content,drying moisture content,water immersion moisture content,and natural density.According to the analysis of the screening test results,there were obvious differences in the coarse-grained content of the six kinds of mixed soils,and they were named as No.1 to 6 according to the sequence of the coarse-grained particles from low to high.The No.1 soil had a coarse particle content of 12.15%,and No.6 soil had a coarse particle content of 84.22%.Secondly,the triaxial consolidation test of large static coarse particle soil was performed on the six soil samples under the confining pressure of seven groups.The soil samples after the tests were subjected to a screening test.The relative breaking ratewas used as an index to study the degree of particle crushing.Comparing the experimental data,the relative breaking rateof the 6 soil samples under the confining pressure of the 7 groups was obtained,and the relationship between the soil pressure and the confining pressure was drawn.The analysis shows that the relative breaking ratesof the six soil samples increase with the increase of confining pressure.Under the same consolidation confining pressure,the higher the coarse grain content,the greater the relative breaking rate.The rate of increase of the relative breaking ratewas dynamically changed.After the content of coarse granules exceeded 42.71%,the rate of increase of the relative crushed rateaccelerated,and the skeleton of the mixed soil was controlled by fine granules to complete the transformation to the control of coarse granules.Only from the filling effect,with the increase of the content of coarse particles,the number of contact points between particles gradually decreases,the particles tend to form stress concentration,resulting in a significant increase in the relative breakage rate.When the confining pressure exceeds 600kPa,the units between particles stress on the surface increases continuously,and the shear strength of more particles is achieved.In order to be able to carry the increasing stress,the contact area between the particles is increased by crushing,resulting in a rapid increase in the relative breaking rate,thus the coarse particle content The inflection point value was changed at two rates of 42.71%and confining pressure tail 600kPa.Then,consolidation tests were carried out for No.3 soil?42.71%for coarse particles?and No.5 soil?73.94%for coarse particles?.There were a lot of clay minerals in the fine particles of mixed soils in western Sichuan,making it easy.With carbonates forming cement bodies between coarse particles,the higher the fine particle content is,the richer the more abundant the cementation effect is,and the finer particle content of No.3 soil is higher than that of No.5 soil,so there is a greater Because of cementation,the₃-relationship curve between the selected water content and the drying moisture content is relatively parallel,while the cementation effect of No.5 soil is limited.When the consolidation confining pressure is small,the two₃-curves are basically parallel.As the consolidation confining pressure continues to increase,the effect of limited cementation on the particle breakage phenomenon gradually decreases,and the particle breakage curve tends to coincide.The₃-curve under soaking water content is obviously separated from the relationship curve between the other two water contents,and when the confining confining pressure exceeds 400 kPa,the change rate of the relative breakage rateappears obvious mutation,ie solid The critical value of the confining pressure becomes smaller,which indicates that the soil structure has undergone a slight change in its own structure after soaking,and the strength has been significantly reduced.It shows that the water content has a great influence on the crushing of the mixed soil particles,and the degree of this effect is also closely related to the content of coarse particles.Finally,the shear test results of six soil samples under seven confining pressures were analyzed.It was found that the deviatoric stress increased with the increase of confining pressure and coarse particle content,and the cohesive forces of the six soil samples were also obtained.The internal friction angle was analyzed and the results showed that with the increase of the content of coarse particles,there was no obvious regular change in cohesion,and the internal friction angle increased continuously.The curve of the relationship between the content of coarse particles and the internal friction angle was linearly and piecewise fitted.It is found that when the content of coarse particles is in the range of 0³0%,the internal friction angle increases slowly with the increase of the content of coarse particles.In the range of30%⁶0%,the internal friction angle increases dramatically as the content of coarse particles increases.In more than 60%,the internal friction angle increases and then declines with the content of coarse particles increasing,therefore,there are two internal friction angles within the limits,the coarse particles respectively are 35%and 75%.