The Yellow River Delta contains extensive fine-grained silts. Assessing long-term property changes is vital for infrastructure stability. Stress relaxation is a critical indicator of the time-dependent stress evolution in soils. As a region characterized by the widespread distribution of typical coastal fine-grained soils, stress relaxation exhibits complex variations under the combined influences of depth, salinity, pH, and other factors. Current research lacks characterization of pre-strain ( ) effects and its correlation with in-situ testing, requiring further breakthroughs. This study represents the first systematic application of the cone penetration test (CPT) to the investigation of soil stress relaxation behavior. A five-element viscoelastic constitutive model was developed, accurately characterizing stress relaxation and identifying the incomplete relaxation phenomenon along with the effects of pre-strain. Three CPT relaxation stages were identified, and a method to estimate was developed, validating a CPT-based theoretical framework for soil relaxation. Furthermore, using SBT (Soil Behavior Type)-based classification as an example, penetration data corrected for stress relaxation reclassify sand-like soils within fine-grained layers as silty or clayey soils, bringing the predicted results closer to actual conditions and improving soil stratification accuracy. This study confirmed the multivariate linear relationship between the Young's modulus ( E t ) derived from cone tip resistance ( q c ) and the elastic coefficients of the five-element model. The findings demonstrate the feasibility of in-situ CPT for stress relaxation testing, offering a novel theoretical foundation and methodological guidance, improving the accuracy of long-term silt mechanical behavior assessments in Yellow River delta silt.
Liu et al. (Fri,) studied this question.
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