Modelling the behavior of inundated collapsible soils

Abstract

The properties of collapsible soil exhibit a lot of sensitivity toward the increase of water content, especially when the soil is close to the dry state. The inundation of collapsible soils induces a considerable drop in the void ratio (e) (ie, collapse potential, Cp, increase), which in return affects the dry unit weight ( d ), friction angle ( ), and shear strength of the soil. The presented study employs large numbers of sandy and silty specimens of collapsible soils with different initial conditions (gathered from the literature) to develop a correlation that evaluates Cp of the soil (ie, settlement) due to inundation. The developed relationship accounts for the soil's initial properties such as the void ratio (e 0 ), degree of saturation (Sr), and pressure applied to the inundated specimens. The presented model reflects the significant influence of Sr on Cp of inundated soil which considerably decreases by the increase of Sr. The determined properties of inundated collapsed soil, such as e and , are employed to construct the post-inundation stress-strain curve (ie, mobilized shear strength) of the soil based on the concepts of the conventional triaxial test. Comparisons between predicted and measured stress-strain curves of inundated collapsible soils are presented for validation. K E Y W O R D Scollapse potential, collapsible soil, constitutive model, stress-strain curve INTRODUCTIONCollapsible soils or metastable soils are unsaturated soils that undergo a significant volume reduction upon saturation with or without additional load. Generally, collapsible soils maintain an open "honeycombed" structure that could have negative pore water pressure and cementing agents that result in considerable shear strength. As a result of wetting, effective stresses are reduced due to the dissipation of the negative pore water pressure. Furthermore, the water dissolves or softens the bonds between the particles, causing a reduction in shear strength, nonetheless a denser particle packing.Collapsible soils may exist in natural deposits as well as in man-made fills and have been under investigation for many years in a broad literature. El Howayek et al 1 investigated the susceptibility of man-made fills to undergo collapse by conducting experimental investigations on two loess soil types that were compacted to a wide range of values of relative compaction (RC). El Howayek et al 1 observed that even specimens compacted to approximately 90% RC on the dry side of the optimum moisture content experienced large wetting-induced strains. In general, El Howayek et al 1 concluded that the collapse potential increases with decreasing compaction water content, RC, and degree of saturation.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Variation of Collapse Potential with Initial Suction Pressure for Natural and Treated Unsaturated Gypseous Soil

“…In the past, some correlations were attempted to produce the collapse of sandy and silty soil (not gypseous soil) such as [1,5] with coefficient of correlation (R 2 ) of 0.82 for both, which considered as a higher coefficient of correlation (R 2 ) value. They studied the effect of initial water content, wetting pressure, and initial void ratio.…”

“…Unsaturated soils with a large volume loss upon impregnation, together with or without additional stress, are called collapsible or metastable soils. Collapsible soils typically keep an unlock, "honeycombed" formation with cementing agents that produce significant shear strength and negative pore water pressure [1]. Effective stresses are decreased due to wetting because the negative pore water pressure is dissipated.…”

A comprehensive study on soil parameters influencing collapsibility of loess through data analysis

“…( 6), which is based on the results of 45 tests performed on three different types of sandy soil. Recently, Ashour et al (2020) presented Eq (7) to predict the CP using a dataset comprising 339 data records.…”

Collapsibility of Gypseous Soil Treated with Pectin-Biopolymer through Leaching

“…When dry, gypsum ofers an apparent cementation, but water infltration causes breakdown and softening of the soil, which can lead to partial or full collapse of buildings [6]. Temperature, the amount of water in contact with the gypsum substrates, applied pressure, water velocity, and grain size are all natural elements that might infuence gypsum dissolving [7,8]. Long-term dissolution is a major regulating element in modifying the geotechnical parameters of gypseous soils.…”