Effect of particle composition and matric suction on shear strength of residual soil
Granite residual soil can experience significant deterioration in strength when exposed to water,leading to geological hazards and engineering problems such as collapses and landslides.The particle composition of residual soil varies vertically due to weathering,and this study investigated the influence of particle composition and matric suction on the mechanical properties of unsaturated granite residual soil.Five types of residual soil with different particle compositions were tested using soil-water char-acteristic curves and direct shear tests at different degrees of saturation.The fractal dimension D was used to characterize the par-ticle composition of the residual soil,and it was found that D increased with the content of fine particles in the soil.The results show that the soil-water characteristic curve of residual soil is affected by particle composition.The VG model parameters are lin-early related to the fractal dimension D.Particle composition and matric suction affect the contact between soil particles,which in turn affects the shear strength of residual soil.The apparent internal friction angle φ and the apparent cohesion c of residual soil increase with increasing matric suction ψ,and φ gradually stabilizes while c decreases when matric suction ψ reaches about 200 kPa.Empirical formulas that include the fractal dimension D and matric suction ψ can be used to predict the shear strength pa-rameters(φ,c)of residual soil.These research findings can provide reference for the selection of mechanical strength parameters in engineering design in areas with granite residual soil.
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