UH model for granular soils considering low confining pressure
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RESEARCH PAPER
UH model for granular soils considering low confining pressure YangPing Yao1 • NingBo Wang1 • Dong Chen1 Received: 22 July 2020 / Accepted: 21 September 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The mechanical behaviors including strength and isotropic compression of granular soils under low confining pressure are systematically analyzed. The compressive hardening parameter ps is introduced in semi-logarithmic coordinates to express the curved normal compression line of granular soils in the e-ln p plane, to describe the little compressibility of granular soils under low confining pressure. The nonlinear variation of critical friction angle with confining pressure is considered by introducing the interlocking strength parameter s0 into strength criteria. Based on the unified hardening model for clays and sands (CSUH model), the unified hardening (UH model) for granular soils considering low confining pressure, called UH-L model, is established. The UH-L model behaves significantly different with the CSUH model under low confining pressure, while tends to be same as the CSUH model with increasing confining pressure. The relationship between parameter ps and s0cotu, as well as the effect of ps and s0cotu on model performance are analyzed. Good agreement with the experimental data shows that the UH-L model is capable of uniformly describing the stress–strain relations and strength of granular soils with interparticle locking over a wide confining pressure load range, especially at low confining pressure. Keywords Granular soils Isotropic compression Interlocking strength Low confining pressure The CSUH model
1 Introduction Granular soils, such as rockfill material, gravel and sandy soils, have been widely used in geotechnical engineering and received extensive study by many researchers. Compared with clays [31, 32, 40], granular soils exhibit complex mechanical properties as follows [9, 14, 16, 27, 30]: (1) isotropic compression lines and critical state lines are curved in the e-ln p plane; (2) stress–strain relations depend on initial confining pressure and initial void ratio. For example, a dense granular soil behaves strain softening and negative dilatancy under low confining pressure, while it shows strain hardening and positive dilatancy under high confining pressure; (3) significant particle breakage is observed under high and ultra-high confining pressure. To predict the mechanical behaviors of granular soils, various constitutive models have been established. Among them, the constitutive models that introduce state
& YangPing Yao [email protected] 1
School of Transportation Science and Engineering, Beihang University, Beijing 100191, China
parameter to consider stress–strain relations dependent on initial confining pressure and initial void ratio are most widely accepted. Jefferies [10] firstly introduced the state parameter into sand constitutive model. Yu [45] defined a general stress ratio-state varia
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