scholarly journals The influence of the grain-size distribution and soil structure on the unsaturated shear strength of loess sediments in Belgrade, Central Serbia

2009 ◽  
pp. 83-91 ◽  
Author(s):  
Gordana Hadzi-Nikovic
Keyword(s):  
Grain Size ◽  
Shear Strength ◽  
Ground Water ◽  
Water Level ◽  
Size Distribution ◽  
Soil Water ◽  
Grain Size Distribution ◽  
Unsaturated Soil ◽  
Laboratory Testing ◽  
Soil Structure

There is a negative pore water pressure or matric suction in the zone above the ground water level in silty loess soil, which can be as deep as 5-10 m in the Belgrade area. This primary characteristic of unsaturated soil, i.e., matric suction, should be included in laboratory testing and geotechnical analyses. Direct shear or triaxial testing of unsaturated soil are very expensive and time-consuming and require specially modified equipment. Instead, the prediction of unsaturated shear strength using the soil water characteristic curve, SWCC, and the effective shear strength parameters c' and ?' is a widely accepted practice. In this study, constitutive soil-water characteristic curves were obtained from the results of experimental testing by draining saturated soil samples under different pressures. This testing was performed for the first time in Serbia in a 15 bar pressure plate extractor according to ASTM standards. The laboratory testing included natural samples of loess sediments with the original macroporous structure and loess sediments with a destroyed soil structure. The influence of the grain-size distribution and natural soil structure on the unsaturated shear strength of Belgrade loess sediments above the ground water level was also evaluated. The obtained results are in accordance with the results from other investigations.

Use of the grain-size distribution for estimation of the soil-water characteristic curve

2002 ◽  
Vol 39 (5) ◽  
pp. 1103-1117 ◽  
Author(s):  
Murray D Fredlund ◽  
G Ward Wilson ◽  
Delwyn G Fredlund
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Soil Water ◽  
Grain Size Distribution ◽  
Unsaturated Soil ◽  
Soil Property ◽  
Characteristic Curve ◽  
Engineering Practice ◽  
Soil Water Characteristic Curve ◽  
Mass Properties

The implementation of unsaturated soil mechanics into engineering practice is dependent, to a large extent, upon an ability to estimate unsaturated soil property functions. The soil-water characteristic curve (SWCC), along with the saturated soil properties, has proven to provide a satisfactory basis for estimating the permeability function and shear strength functions for an unsaturated soil. The volume change functions have not been totally defined nor applied in geotechnical engineering. The objective of this paper is to present a procedure for estimating the SWCC from information on the grain-size distribution and the volume–mass properties of a soil. SWCCs represent a continuous water content versus soil suction relationship. The proposed method provides an approximate means of estimating the desorption curve corresponding to a soil initially slurried near the liquid limit. The effects of stress history, fabric, confining pressure, and hysteresis are not addressed. A database of published data is used to verify the proposed procedure. The database contains independent measurements of the grain-size distribution and the SWCC. The level of fit between the estimated and measured SWCCs is analyzed statistically. The proposed procedure is compared to previously proposed methods for predicting the SWCC from the grain-size distribution. The results show that the proposed procedure is somewhat superior to previous methods.Key words: soil-water characteristic curve, grain-size distribution, volume-mass properties, pedo-transfer function, unsaturated soil property functions.

scholarly journals Evaluation of prediction models applied to the soil-water characteristic curve of ideal materials

2020 ◽  
Vol 195 ◽  
pp. 02024
Author(s):  
Roberto Dutra Alves ◽  
Gilson de F. N. Gitirana ◽  
Sai K. Vanapalli
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Soil Water ◽  
Grain Size Distribution ◽  
Characteristic Curve ◽  
Empirical Models ◽  
Spherical Particles ◽  
Soil Water Characteristic Curve ◽  
Varying Coefficients ◽  
Semi Empirical

The development of theoretical and semi-empirical models to study capillary mechanisms and predict the soil-water characteristic curve (SWCC) generally requires the idealization of pore space and pore water, considering simplifying hypotheses. The study of ideal materials comprised of particles with controlled shape and size allows the evaluation of such simplifying hypotheses and the subsequent generalization to actual soils. In this paper, four theoretical and semi-empirical models for the prediction of the SWCC are applied to the prediction of artificial materials comprised of spherical particles. Nineteen grain-size distribution curves, with varying coefficients of uniformity are considered. The dataset is comprised of materials previously published and additional tests carried out by the authors, under highly controlled conditions. The analyses allowed the evaluation of the effect of grain-size distribution curve and shape of the particles. The limitations and advantages of each prediction model was investigated, and a detailed comparison is presented, guiding future implementations of improved models.

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