A strength criterion for frozen sodium sulfate saline soil

Abstract

Salt content has been proven to be an important influencing factor on the mechanical properties of frozen saline soils, whose strength criterion is different from that of unfrozen saline soils or frozen soils without salts. In this paper, a series of conventional triaxial tests are carried out for frozen saline soils with sodium sulfate at a temperature of -6°C. A strength criterion of the frozen saline soils, including the influence of salt content, is established by using the generalized nonlinear strength theory. Based on conventional triaxial test results, a modified hydrostatic pressure expression is proposed according to the critical strength function of the modified Cam clay model in the meridian plane. The influence of salt content on the shear strength of the frozen saline soils is investigated according to their freezing temperature curves as well as the formation of salt and ice crystals. The relationship between salt content and friction angle is analyzed. The proposed strength criterion of frozen saline soil is proved to be reliable by extrusion elongation triaxial tests. This criterion can reasonably reflect the major nonlinear strength characteristics of frozen saline soils, including the influences of change in salt content, pressure melting, and ice crushing.Key words: sodium sulfate, frozen saline soil, strength criterion, freezing temperature, deviatoric plane.Résumé : La teneur en sel est avérée être un facteur d'influence importante sur les propriétés mécaniques des sols salins congelés, dont son critère de résistance est différent de celle des sols salins dégelés ou des sols gelés sans sels. Dans cet article, une série d'essais triaxiaux classiques sont effectués pour les sols salins congelés avec du sulfate de sodium à la température de -6°C. Un critère de résistance de sols salins congelés, y compris l'influence de la teneur en sel, est établi en utilisant la théorie généralisée de la résistance non linéaire. Sur la base de résultats d'essais triaxiaux classiques, une expression de pression modifiée hydrostatique est proposée, conformément à la fonction de la résistance critique du modèle Cam clay modifié dans le plan méridien. L'influence de la teneur en sel sur la résistance au cisaillement des sols salins congelés est étudiée en fonction de leurs courbes de température de congélation, et aussi la formation de cristaux de glace et de sel. La relation entre la teneur en sel et l'angle de frottement est analysée. Le critère de la résistance proposé de sol salin congelé est prouvé fiable par des essais triaxiaux d'allongement par extrusion. Ce critère peut raisonnablement refléter les principales caractéristiques de résistance non linéaire des sols salins congelés, y compris les influences de l'évolution de la teneur en sel, de la fusion et du broyage de glace sous pression. [Traduit par la Rédaction] Mots-clés : sulfate de sodium, sols salins congelés, critère de résistance, température de congélation, plan déviatorique.

Investigation on the Nonlinear Strength Properties and Damage Statistical Constitutive Model for Frozen Sandy Soils

“…With respect to frozen soils, the bonding e ect of ice crystals and soil particles possesses tensile strength, which will be weakened due to the pressure melting under relatively high con ning pressures, similar to the cohesive behaviors of cemented clay. In the previous study [13,14,17,18,37], it is indicated that the strength of frozen soils increases rst and then decreases with the increase of con ning pressures. e maximum value q max of the q-p curve corresponds to failure mean stress p cr .…”

“…Later, Nguyen et al [42] proposed that the CSL of the cemented clay eventually reduced to an asymptote coinciding with the CSL of natural clay. Lai et al [17] and Liao et al [18] employed a modi ed mean e ective stress expression to describe the strength criterion for frozen soils.…”

“…Hence, in this paper, based on the research results of Nguyen et al [42], Lai et al [17], and Liao et al [18], we propose a modi ed strength criterion to simulate the variation tendency of the rst increasing and then decreasing phenomena for frozen sandy soils. Here, the graphic illustration and the proposed modi ed strength criterion are given in Figure 8 and (28) to (30).…”

“…Lai et al [16] established a parabolic curve for frozen silt soils in the meridian plane and Lade-Duncan model in the deviatoric plane to describe the shape function. Lai et al [17] and Liao et al [18] modified the hydrostatic pressure to simulate the strength in the q-p plane and employed a combination of LD and SMP models to describe the deviatoric plane. Lai et al [19] proposed a relationship between the first principal σ 1 and the third principal stress σ 3 , and then they established a nonlinear strength formula for frozen sandy soils.…”

Axial Uplift Behaviour of Belled Piers in Coarse-Grained Saline Soils

“…Massive infrastructures have been designed and constructed in Northern China, such as the West-East electricity transmission project, and have to face the problematic soils, e.g., coarse-grained saline soils, especially those distributed in the Gobi Desert or the desert margin in inland areas [1,2]. e coarse-grained saline soils experienced cyclic salification and desalination due to complex processes that salt in soils periodically exists in crystalline or dissolved state, accompanied by a continuing migration and accumulation of dissolved salt, resulting in particular engineering properties [3,4].…”