To study the failure mechanism of high ductile coagulation (HDC) under sulfate attack in cold saline soil area, cement-based cementing material (cement: fly ash: sand: water reducing agent: water = 1:1:0.72:0.03:0.58) and 2 % polyvinyl alcohol fiber (PVA) were used to prepare HDC sample, to increase the density and ductility of concrete. a 540-day sulfate-long-term immersion test was performed on HDC specimens under two low-temperature curing environments and different sulfate solution concentrations (5 %, 10 %). Using a combination of macro and microscopic methods, according to the principle of energy dissipation, To study the relationship between the evolution of energy (total damage energy U, dissipated energy Uds, elastic strain energy Ues) and the deterioration of strength and the change of pore structure during the compression process of HDC. According to the characteristics of stress-strain curves during HDC compression, the damage evolution characteristics of characteristic stress points during HDC compression are summarized, establish energy storage indicators Kel to evaluate the degree of internal damage of HDC. The results show that during the compression damage process of HDC after long-term soaking in sulfate solution under low temperature environment, Uds and Ues of HDC at characteristic stress points both increase first and then decrease, Kel are reduced first and then increased. The development trend of elastic strain energy and dissipative energy of HDC in 10 % sulfate solution is more drastic than that in 5 % sulfate solution. Compared with the other three groups, the D group energy storage level rises and falls more violently, and the HDC has a smaller ability to resist damage under this condition. Through the study of the correlation between macro and micro changes of HDC in cold saline soil areas and energy evolution, to provide a reference for the stable operation of highly ductile concrete in cold saline soil areas.

During the landfilling and resource utilization of solidified soil, it is inevitable that the material will be influenced by the surrounding water environment. Processes such as soaking and infiltration of both clean water and contaminated liquids can have an impact. This paper investigates the strength and structural stability of soil contaminated with a high concentration of lead or copper that has been solidified with red mud-carbide slag-phosphogypsum (RCP-Pb or RCP-Cu, respectively) in strongly acidic water, weakly acidic water, and pure water, as well as in two different modes of soaking and infiltration. The unconfined compressive strength, apparent and microscopic morphology, mineral composition, and functional groups of solidified soil before and after the action of different water solutions were compared, and the water and acid resistance of solidified soil was comprehensively analyzed. The results indicate that under the influence of a strongly acidic water environment, the strength of RCP-Pb and RCP-Cu can decrease by up to 26.4% and 18.5%, respectively, compared to the standard solidified specimens. Conversely, in a weakly acidic environment, the strength of the specimens can increase by a maximum of 21.1% and 32.8%, respectively. Under the two different water environment modes of action, RCP-Pb exhibits a greater increase in strength (39.8%) under soaking conditions, while RCP-Cu shows a greater increase (44.4%) under water infiltration. Based on the microscopic images, the pore counts in specimens in weakly acidic and pure water environments are greater than those in standard solidified specimens, while the porosity is less than that in standard solidified specimens. The surface of the particles exhibited increased roughness. A noticeable finding is that, under the infiltration of a strongly acidic water environment, the porosity of RCP-Pb increases to 20.22%, and the pore counts of RCP-Cu rise to 534. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that as the acidity of the water environment increased, the CaCO3 content significantly decreased. However, hydration products such as calcium silicate hydrate (C-S-H), calcium aluminate hydrate (C-A-H), calcium aluminosilicate hydrate (C-A-S-H), and ettringite (AFt) did not show significant differences. Consequently, the specimens maintained a stable strength and structure even under such a water environment.

Due to Paleo-clay's unique properties and widespread distribution throughout China, it is essential in geotechnical engineering. Rainfall frequently causes the deformation of Paleo-clay slopes, making slope instability prediction crucial for disaster prevention. This study explored Paleo-clay's strength degradation and slope stability under soaking and wet-dry cycles. Using Mohr-Coulomb failure envelopes from experiments, curve fitting was used to find the patterns of Paleo-clay strength degradation. Finite element simulations and the strength discounting method were used to analyze the stability and deformation of Paleo-clay slopes. The results indicate that wet-dry cycles impact them more than soaking. Paleo-clay's cohesion decreases exponentially as the number of wet-dry cycles and soaking times rise, but the internal friction angle changes very little. After 10 wet-dry cycles and 24 days of soaking, iron-bearing clay's cohesion decreased to 17% and 44% and reticular clay's to 32% and 48%. Based on the study area characteristics, three slope types were constructed. Their stability exhibited exponential decay. Under soaking, stability remained above 1.4; under wet-dry cycles, type I and II stability fell below 1.0, leading to deformation and failure. All types showed traction landslides with sliding zones transitioning from deep to shallow. Practical engineering should focus on the shallow failures of Paleo-clay slopes.

This paper presents experimental studies on a compacted expansive soil, from Nanyang, China for investigating the at-rest lateral earth pressure sigma(L) of expansive soils. The key studies include (i) relationships between the aL and the vertical stress sigma(V) during soaking and consolidation, (ii) the influences of initial dry density p(d0) and moisture content w(0) on the vertical and lateral swelling pressures at no swelling strain (i.e. sigma(V0) and sigma(L0)), and (iii) evolution of the sigma(L) during five long-term wetting-drying cycles. Experimental results demonstrated that the post-soaking sigma(L)-sigma(V) relationships are piecewise linear and their slopes in the passive state (sigma(L) > sigma(V)) and active state (sigma(L) < sigma(V)) are similar to that of the consolidation sigma(L)-sigma(V) relationships in the normal- and over-consolidated states, respectively. The soaking sigma(L)-sigma(V) relationships converge to the consolidation sigma(L)-sigma(V) relationships at a threshold aV where the interparticle swelling is restrained. The sigma(L0) and sigma(V0) increase monotonically with p(d0); however, they show increasingthen-decreasing trends with the w(0). The extent of compaction-induced swelling anisotropy, which is evaluated by sigma(L0)/sigma(V0), reduces with an increase in the compaction energy and molding water content. The sigma(L) reduces over moisture cycles and the stress relaxation in the sigma(L) during soaking is observed. An approach was developed to predict the at-rest soaking sigma(L)-sigma(V) relationships, which requires conventional consolidation and shear strength properties and one measurement of the sigma(L)-sigma(V) relationships during soaking. The proposed approach was validated using the results of three different expansive soils available in the literature. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

In salt-rich soft soil regions, as a backfill material, foamed lightweight soil (FLS) is often subjected to long-term chemical erosion of groundwater, which would lead to a continuous degradation of strength properties, and ultimately causes a risk to the long-term safety of infrastructures. Combining sulfate chemical soaking test and dry-wet cycle test, this paper investigates the durability changes of FLS under different densities of FLS, sulfate concentrations, and cation types of sulfate. The results indicate that the dynamic strength degradation of FLS under dry-wet cycles is much greater than that under sulfate soaking. When other influencing factors remain unchanged, the corrosiveness of Na2SO4 solution is greater than that of MgSO4 solution. Moreover, this paper establishes a dynamic strength degradation prediction model for FLS based on the experimental results, which can scientifically guide the durability changes of FLS under different influencing factors.