Effects of Gravel Content on Shear Resistances of Gravelly Soils under Simple Shear Conditions

  • 游 泰清

Student thesis: Doctoral Thesis

Abstract

Shallow landslides in colluvium which generally consists of wide particle gradation in a loose state occur in steep-slope terrains To perform stability analyses shear strength parameters that represents soil constituents in-situ stress state and shearing mode are needed Due to the presence of oversized gravel particles block sampling and large-scale testing apparatus are required to determine the shear strength parameters of colluvial deposits Limited by the sampling methods and testing apparatus laboratory testing on soils with oversized particles is a challenging task In addition the effects of particle size on colluvium or rockfill are difficult to evaluate and could be site-dependent A comprehensive study is performed to study the effects of gravel content on shear resistances under simple shear conditions on the framework of intergrain state concept To quantitatively evaluate the size and boundary conditions of simple shear testing distinct element method (DEM) were carried out and validated by physical element tests on uniform and mixture steel balls using a simple shear apparatus The validated models are used to evaluate the influences of specimen dimensions and maximum particle size on macroscopic stress-strain responses and microscopic uniformity on particle force and displacement fields A series of drained simple shear tests were performed on reconstituted specimens of gap- and well-graded sands The results show that: (1) the shear strength of granular soils depends on the packing condition of dominant particles with the intergrain granular void ratio being a more representative parameter for the soil packing condition than the global void ratio; (2) the drained shear strength of loose sand-like colluvial soils is dominated by sand matrix properties and the inclusion of gravel content reduces the strength by no more than 20% compared to that of pure sand The experimental study on undrained simple shear tests was conducted on reconstituted specimens of gap- graded silt and well-graded sandy silt The results indicate that (1) the undrained shear strength of dense gap-graded silt with gravels is dominated by silt matrix properties and the inclusion of gravel content increases the strength by no more than 7% compared to that of pure silt; (2) the strength parameters of colluvium can be estimated from the fine particle matrix with proper adjustment of gravel content
Date of Award2016 Aug 15
LanguageEnglish
SupervisorWen-Jong Chang (Supervisor)

Cite this

Effects of Gravel Content on Shear Resistances of Gravelly Soils under Simple Shear Conditions
泰清, 游. (Author). 2016 Aug 15

Student thesis: Doctoral Thesis