Test Research On The Shear Strength Characteristics Of Rock-Soil Aggregate Mixture

Coarse aggregate and soil-rock mixture are important filling materials. Because of their good engineering property, they are widely used in engineering. Large test instruments are often adopted to study their mechanical characteristics and other related parameters. The paper uses the large-scale direct shear test to study soil-rock mixture so as to provide theoretical basis for its application in the practical engineering.The research objects of the paper are red clay, gravel and soil rock mixture collected from Yuzhang quarry, in Nanchang City.Three kinds of tests have been carried out as follows :(1) the conventional direct shear test, to study the influence of the water content and dry density on unsaturated red clay shear strength characteristics.(2) large direct shear test, to study the strength characteristics and particle breakage law of coarse aggregate of different particle size and gradation under high normal stress and also to study effects of different water content, stone content, vertical pressure and properties of soil and rock on mechanics parameters of soil rock mixture.The main research outcomes are as follows:1.Under the same dry density, with the increase of water content and vertical pressure,the strain characteristics of unsaturated red clay’s shift from strain softening type to hardening type. Internal friction angle decreases as moisture content increases, and cohesion firstly increases as moisture content increases and then decreases. In the case of the same moisture content, with the increase of dry density, the curve shows a more obvious strain softening phenomenon, and internal friction angle and cohesion increase as the dry density increases.2. Particles in the shearing process are mainly broken into ones of the secondary sizes,and even more. The particle breakage rate and shear strength increase as the vertical pressure increases under the same grain samples and increase as the particle size increases under the same vertical pressure. The better the particle gradation is, the harder particle isbroken. Under the higher vertical pressure, the shear strength envelope of coarse aggregate is not always linear,part of which is curve,and hardening type and shear shrinkage properties are also revealed. The higher the vertical pressure is, the greater the weakening effect on dilatancy is and the shear contraction effect is more obvious. The internal friction angle of single particle group increases as particle size increases.3. Soil-rock mixtures under different moisture contents and stone contents show hardening characteristics and shear shrinkage effect. The shear strength of samples increases as vertical pressure increases and decreases as moisture content increases.Moreover, it generally increases as stone content increases. The cohesion decreases as moisture content increases and it decreases firstly as the stone content increases and then increases and decreases again at last. The internal friction angle decreases as moisture content increases and it firstly increases as stone content increases and then reduces again.