Abstract:From the material science point of view, saturated frozen soil is a natural particulate composite, composed of solid grains, ice and unfrozen water. The mechanical behaviour of such a material is strongly affected by the amount of ice. The amount of ice depends on the temperature and the applied mechanical stresses. The influence of ice content and temperature on the mechanical behaviour and the coupling effects on the reverse direction can be mentioned as the main difference between frozen and unfrozen soils.… Show more
“…The prepared earth samples were placed in a conservation box at a temperature of 25 ± 2 °C and 50% relative humidity and maintained to the appropriate age. Conduct the corresponding tests and record the test data according to <Standard for Soil Test Methods GBT 50123-201933> 36 . Figure 3 Soil specimens preparation instrument.…”
Section: Test Materials and Methodsmentioning
confidence: 99%
“…Chang et al 33 pointed out that the Xanthan gum has a better reinforcement effect on well graded soil, and the reinforcement effect mainly depends on four factors: soil type, xanthan gum content, curing age, and mixing method. The results of Ahmadi et al [34][35][36] showed that the cleaning improver such as xanthan gum can significantly improve the mechanical properties of soil after dry-wet cycle (W-D) and freeze-thaw cycle (F-T). Kumar et al 24 confirmed that the Xanthan gum is more efficient in reducing soil permeability compared to guar gum and pectin.…”
The low liquid limit silty soil in the North China plain area is generally unsuitable for direct use as roadbed and slope soil. In order to improve the performance of low liquid limit silty soil, xanthan gum was used as an improver. Through a series of tests, the improvement effect of xanthan gum on low liquid limit silty soil was studied. The test results showed that Xanthan gum as an improver could significantly improve the unconfined compressive strength of silty soil. With the increase in dosage and curing age, the unconfined compressive strength of improved silty soil continued to improve and eventually tended to stabilize. The optimal dosage and curing period were 2% and 7 days, respectively. In addition, Xanthan gum could greatly improve the permeability and disintegration of low liquid limit silty soil. The permeability coefficient of improved silty soil with a content of 0.75% Xanthan gum and a 7-day curing period was 4.73 × 10−4 m·s−1, which was only 1.10% of that of plain silty soil at the same curing period. After immersion in water for 12 h, the soil only experienced slight disintegration. The scanning electron microscope image showed that the gel generated by the hydration reaction of Xanthan gum could improve the compactness and integrity of the soil by filling the voids, thus significantly improving the mechanical and hydraulic properties of the low liquid limit silty soil.
“…The prepared earth samples were placed in a conservation box at a temperature of 25 ± 2 °C and 50% relative humidity and maintained to the appropriate age. Conduct the corresponding tests and record the test data according to <Standard for Soil Test Methods GBT 50123-201933> 36 . Figure 3 Soil specimens preparation instrument.…”
Section: Test Materials and Methodsmentioning
confidence: 99%
“…Chang et al 33 pointed out that the Xanthan gum has a better reinforcement effect on well graded soil, and the reinforcement effect mainly depends on four factors: soil type, xanthan gum content, curing age, and mixing method. The results of Ahmadi et al [34][35][36] showed that the cleaning improver such as xanthan gum can significantly improve the mechanical properties of soil after dry-wet cycle (W-D) and freeze-thaw cycle (F-T). Kumar et al 24 confirmed that the Xanthan gum is more efficient in reducing soil permeability compared to guar gum and pectin.…”
The low liquid limit silty soil in the North China plain area is generally unsuitable for direct use as roadbed and slope soil. In order to improve the performance of low liquid limit silty soil, xanthan gum was used as an improver. Through a series of tests, the improvement effect of xanthan gum on low liquid limit silty soil was studied. The test results showed that Xanthan gum as an improver could significantly improve the unconfined compressive strength of silty soil. With the increase in dosage and curing age, the unconfined compressive strength of improved silty soil continued to improve and eventually tended to stabilize. The optimal dosage and curing period were 2% and 7 days, respectively. In addition, Xanthan gum could greatly improve the permeability and disintegration of low liquid limit silty soil. The permeability coefficient of improved silty soil with a content of 0.75% Xanthan gum and a 7-day curing period was 4.73 × 10−4 m·s−1, which was only 1.10% of that of plain silty soil at the same curing period. After immersion in water for 12 h, the soil only experienced slight disintegration. The scanning electron microscope image showed that the gel generated by the hydration reaction of Xanthan gum could improve the compactness and integrity of the soil by filling the voids, thus significantly improving the mechanical and hydraulic properties of the low liquid limit silty soil.
“…On the other hand, the mean and deviatoric stress-induced pore pressure development at high UWC condition can play important roles in mechanical and hydrological analyses of frozen saline soil [13,31], and an effective stress model with the consideration of pore pressure can be a better option for thermo-hydro-mechanical modeling than a total stress model. However, the study of load-induced pore pressure development for frozen soil is quite scarce, although pore-water pressure in frozen soil has been measured for other kinds of investigation, such as freezing and thawing tests [15,18,54], cryogenic suction at the water-ice interface [19,30], and water redistribution in one dimensional freezing process [40,56,57].…”
A systematical testing program on frozen Onsøy clay under isotropic loading and undrained shearing at different temperatures (− 3 ~ − 10 °C), strain rates (0.2~5%/h) and initial Terzaghi effective stress (20~400 kPa) was conducted with the focus on pore pressure development. It is meant to increase the understanding and facilitate the development of an ‘effective stress’-based model for multi-physical analysis for frozen soils. This study adopted the pore pressure measurement method suggested by Arenson and Springman (Can Geotech J 42 (2):412–430, 2005. https://doi.org/10.1139/t04-111) and developed a new testing procedure for frozen soils, including a ‘slow’ freezing method for sample preparation and post-freezing consolidation for securing hydraulic pressure equilibrium. The B-value of frozen soils is less than 1 and significantly dependent on temperature and loading history. The dilative tendency or pore pressure development in an undrained shearing condition is found to be dependent on both unfrozen water content and mean stress, which is consistent with unfrozen soils. Besides, the experimental results reported in the literature regarding uniaxial tests show that the shear strength does not share the same temperature- and salinity-dependency for different frozen soil types. The rate dependency of frozen soils is characterized between rate dependency of pure ice and that of the unfrozen soil and is therefore highly determined by the content of ice and the viscous behavior of ice (through temperature dependency). This paper also explains the pore pressure response in freezing and thawing is dependent on volumetric evolution of soil skeleton.
“…This process triggers the creation of new cracks, the expansion of existing cracks, and a reduction in slope strength (Kjelstrup et al, 2021;. This degradation compromises the mechanical integrity of rocks in geological engineering, threatening the safety and stability of infrastructures in cold regions (Ghoreishian Amiri et al, 2022). The expansion of pores and microcracks in rocks leads to a greater water storage capacity, intensifying frost damage upon subsequent freezing (Zhang et al, 2020).…”
In cold regions, rocks undergo periodic temperature fluctuations, resulting in deterioration in pore structure and mechanical behavior. This degradation can lead to instability in rock masses and contribute to landslides. While many studies have investigated the effects of freeze-thaw (F-T) cycles on the mechanical behavior of rocks, the micro-level mechanisms of deterioration remain less understood. In this study, the evolution of the pore structure of a prefabricated sandstone with 30 freeze-thaw cycles ranging from −20°C to 20°C is explored using CT scanning. The influence of the prefabricated crack is highlighted. The results indicate a significant impact of freeze-thaw cycles on large pores, with their proportion increasing from 15.28% to 38.72% after 30 F-T cycles. Within the initial 10 F-T cycles, pore structure changes occur without the expansion of prefabricated crack. However, after 15 F-T cycles, prefabricated crack begins extending downward, eventually becoming nearly continuous after 30 F-T cycles. Prefabricated crack notably influences pore distribution during freeze-thaw cycles, with higher porosity near the fracture, where pores initially expand and connect. These findings provide insights into the damage mechanism in sandstone under F-T cycles.
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