Comparison of Methods for Determining Precompression Stress Based on Computational Simulation

Abstract

There are many methods for determining precompression stress (σ p ), whose value is affected by the slope of the soil compression curve. This study was designed to evaluate the hypothesis that for a certain compression curve all methods used to determine σ p present the same value and accuracy. The aim of this study was to compare the accuracy and the relationship among seven of these methods by computational simulation of soil compression curves under nine scenarios. The following methods were used: Casagrande, Pacheco Silva, intersection of the initial void ratio with the virgin compression line (VCLzero), and the regression methods based on 2 (reg1), 3 (reg2), 4 (reg3), and 5 (reg4) points for modeling the elastic curve. Under each scenario, created by combining the swelling and the compression indices, 1,000 compression curves were computationally simulated via the Monte Carlo method. Subsequently, 95 % percentile confidence intervals were built using the 1,000 estimates of σ p from each method under each scenario. Most of the differences among the methods were detected under scenarios consisting of high swelling and low compression indices. In general, Casagrande, Pacheco Silva, and reg4 were strongly correlated and presented the highest values of σ p , as well as similar variability. The latter two can be considered as alternatives to the standard method of Casagrande, except for Pacheco Silva when the curve has a low compression index (≤0.2) and from medium to high swelling index (≥0.025), for which differences (p<0.05) were detected.

Estimation of precompression stress in an Ultisol cultivated with sugarcane

“…Pearson correlation coefficient. *p-value < 0.01 by t-test The linear and positive impacts of BD on σ p have also been observed by Imhoff et al (2004), Saffih-Hdadi et al (2009, Lima et al (2015Lima et al ( , 2016 and Schjønning & Lamandé (2018). Imhoff et al (2004) attributed the positive effect of BD to the increase of the frictional forces in the soil mass and explained that these forces impede the displacement and separation of the particles under stress, increasing the load-bearing capacity of the soil.…”

“…The resistance of soil to compaction is assumed as the precompression stress (σ p ) (Stettler et al, 2014;Schjønning & Lamandé, 2018), which can be obtained via the compression curve. The determination of σ p is complex and time-consuming (Lima et al, 2016;Schjønning & Lamandé, 2018), and therefore, pedo-transfer functions have been used to estimate σ p as a function of soil physical parameters, which can be easily obtained in the field (Schjønning & Lamandé, 2018). Water content (Oliveira et al, 2011;Severiano et al, 2013) and soil bulk density (Lima et al, 2015) are significantly correlated with σ p .…”

Soil Compressibility under Irrigated Perennial and Annual Crops in a Semi-Arid Environment

“…Other studies have focused on investigating the methods applied in determination of σ p and pedotransfer functions (Dias Junior and Pierce, 1996;Imhoff et al, 2004;Cavalieri et al, 2008;Suzuki et al, 2008;Severiano et al, 2011;Silva and Lima, 2016).…”