Modelling of Static Liquefaction of Partially Saturated Non-Cohesive Soils

Abstract

Static soil liquefaction is widely known to be a serious danger to the stability of structures. The phenomena governing pore water generation, which leads to liquefaction in fully saturated soils, are already quite well described. However, much less is known of these phenomena occurring in partially saturated porous media, although this, too, is an important issue in geotechnics. This study presents the application of a semi-empirical model to predict the response of partially saturated soils under undrained conditions. The model proposed is based on an incremental equation describing the pre-failure undrained response of partially saturated non-cohesive soils during monotonic shearing in a standard triaxial test. Improved differential equations taking into account pore fluid compressibility were implemented together with empirical coefficients describing soil skeleton compressibility during the unloading phase. Model coefficients were determined in triaxial compression tests. The influence of the saturation level represented by Skempton’s parameter B on the full spectrum of predicted stress paths was shown. For the analyzed saturation range, the maximum stress deviator normalized by initial mean effective stress varied from 0.38 to 1.67 for B values between 0.93 and 0.29, respectively. Model predictions were confronted with the results of triaxial tests for two types of non-cohesive soils (quartz medium sand and copper ore post-flotation industrial tailings). Good agreement between experimental data and theoretical predictions was achieved.

Constitutive modelling of instabilities and strengths of an unsaturated tailings

“…𝑒𝑒 CSL = 0.92 − 0.0159ln(𝑝𝑝 ′ ) for 𝑝𝑝 ′ < 250 kPa; 𝑒𝑒 CSL = 1.68 − 0.153ln(𝑝𝑝 ′ ) for 𝑝𝑝 ′ < 250 kPa according to [7]. No suction hardening information recorded 4 OZM 50 tailings, [6] No suction hardening information recorded, 𝑒𝑒 CSL = 0.908 − 0.0225ln(𝑝𝑝 ′ ) 5 Skarpa sand, [6] No suction hardening information recorded, 𝑒𝑒 CSL = 0.746 − 0.0635log…”

“…Desaturation can enhance the stability of a natural soil or tailings, but there is no guarantee of safety from desaturation alone. There are many reported liquefactions of unsaturated tailings with sand or silt sized particles in either static or seismic conditions [5][6][7][8][9][10][11]. At a loose state a sample will reduce its volume when shearing causing the degree of saturation 𝑆𝑆 r to increase.…”

Experimental Study on Different Improvement Schemes of EICP-Lignin Solidified Silt

“…Therefore, some scholars have proposed enzyme-induced calcium carbonate precipitation (EICP) technology to directly use urease to replace MICP, which also brings new research and application ideas to bio-geotechnical soils. The principle of EICP technology is to mix urease and calcium from urea into the soil [ 17 , 18 , 19 , 20 ]; it promotes the decomposition of urea into NH 4+ and CO 3 2− , and finally forms calcium carbonate precipitation in an alkaline environment to solidify the soil. At present, the method for extracting urease is mainly from the seeds of legumes and bacteria; the supernatant of the solution, that is, the crude extract of urease, can be obtained via low-temperature high-speed centrifugation of urease in plant cells [ 21 , 22 , 23 ].…”

Modelling unsaturated silty tailings and the conditions required for static liquefaction

“…They can experience a reduction in effective stress and strain soften during closed-system loading, attaining a very low residual strength. The conditions required for it to occur are not well understood although there is evidence of it in poorly graded materials containing predominantly sand sized particles when the degree of saturation ( ) is as low as 90% (Grozic et al, 1999;He & Chu, 2014;Lu et al, 2017;Shi et al, 2021;Świdziński & Smyczyński, 2022). In materials which are well graded, and/or contain significant quantities of silt sized particles, it has occurred when is slightly less than 90% (Bella & Musso, 2022).…”