In this study, the mechanical and durability performance of clay soils reinforced with different proportions of Cherry Marble Powder (CMP) and non-woven geotextile configurations, both independently and in combination, is investigated in detail at both the macro and micro levels. The effectiveness of reinforcement in the stabilization of clay soils in cold climates has been evaluated by means of Gray Correlation Analysis (GCA). The results show that as the CMP ratio and the number of geotextiles increase, the peak strength of the soil increases, with higher CMP levels showing perfect plastic behavior and more geotextiles showing linear strain hardening, particularly in combination. Substantial strength reductions post-7th cycle ranged between 91.09 % and 103.38 % for 12 % CMP and 219.83 % and 270.42 % for three-layered geotextile groups. Cohesion increased by 59.76 % and 179.41 %, while the internal friction angles remained stable and decreased after F-T cycles, except with additives. Failure modes shifted with CMP content, F-T cycles and confining pressure. The transition was from strain hardening to strain softening, with increased shear fracture planes and brittleness. The energy absorption capacity (EAC) increased with the CMP ratio, with the geosynthetic reinforcement increasing the EAC by a factor of 1.5 before and after the F-T cycles. The combined use of CMP and geotextiles in soil stabilization improved the engineering properties in areas of frost, with the optimum gradation being three layers of geotextile and a CMP ratio of 12 %, which effectively mitigated the effects of the maximum F-T cycle.

Rapidly growing urbanization and industrialization drive the continued development of soil stabilization and ground improvement techniques. Rice husk ash (RHA) is widely regarded as a highly promising construction material in civil engineering due to its excellent pozzolanic properties and has garnered significant attention from researchers. This paper presents an experimental study and a micro-mechanical discussion on the role of RHA in the mechanical improvement of soil. RHA was mixed with the native soil in varying proportions, ranging from 0% to 12%. Several laboratory tests were conducted, including standard proctor compaction tests, Atterberg limit tests, freeze-thaw tests, unconfined compression tests, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). The results indicated that the optimal moisture content (OMC) of the soil mixture increased while the maximum dry density (MDD) decreased with higher RHA dosage. The Atterberg limits of the soil mixture exhibited a positive correlation with the RHA content. A substantial enhancement in the soil's strength, stiffness, and ductility was observed upon the incorporation of RHA. It was noted that the strength loss of the untreated samples and those with 12% RHA was 34.91% and 12.89%, respectively, following 12 freeze-thaw cycles. Furthermore, XRD test results revealed that the treated specimen had an identical mineral composition to the control specimen, with no generation of hydration products. SEM analysis also highlighted that the filling effect of RHA significantly reduced pore content and pore connectivity within the soil, accompanied by a shift in the specimen's pores from mesopores to small and micropores. The excellent thermal insulation and heat retention properties of RHA, along with its pore-refining effect, make a positive contribution to enhancing the frost resistance of the specimens. These findings contribute to guiding the effective application of RHA in civil engineering, offering eco-friendly solutions for biomass waste management, and promoting the sustainable development of construction materials.

Changing precipitation patterns and global warming have greatly changed winter snow cover, which can affect litter decomposition process by altering soil microenvironment or microbial biomass and activity. However, it remains unknown how and to what extent snow cover affects litter decomposition during winter and over longer periods of time. Here, we conducted a meta-analysis to synthesize litter decomposition studies under different levels of snow cover. Overall, deepened snow significantly enhanced litter decomposition rate and mass loss by 17% and 3%, respectively. Deepened snow enhanced litter carbon loss by 7% but did not impact the loss of litter nitrogen or phosphorus. Deepened snow increased soil temperature, decreased the frequency of freeze-thaw cycles, and stimulated microbial biomass carbon and bacterial biomass during winter, but had no effect on these parameters in summer. The promoting effect of deepened snow cover on litter decomposition in winter is mainly due to its positive effect on microbial decomposition by increasing soil temperature and reducing freezethaw cycles exceeded its negative effect on physical fragmentation of litter by reducing freeze-thaw cycles. Our findings indicate that the changes in winter snow cover under global change scenarios can greatly impact winter litter decomposition and the associated carbon cycling, which should be taken into consideration when assessing the global carbon budget in modeling.

In the context of global warming, increasingly widespread and frequent freezing and thawing cycles (FTCs) will have profound effects on the biogeochemical cycling of soil carbon and nitrogen. FTCs can increase soil greenhouse gas (GHG) emissions by reducing the stability of soil aggregates, promoting the release of dissolved organic carbon, decreasing the number of microorganisms, inducing cell rupture, and releasing carbon and nitrogen nutrients for use by surviving microorganisms. However, the similarity and disparity of the mechanisms potentially contributing to changes in GHGs have not been systematically evaluated. The present study consolidates the most recent findings on the dynamics of soil carbon and nitrogen, as well as GHGs, in relation to FTCs. Additionally, it analyzes the impact of FTCs on soil GHGs in a systematic manner. In this study, particular emphasis is given to the following: (i) the reaction mechanism involved; (ii) variations in soil composition in different types of land (e.g., forest, peatland, farmland, and grassland); (iii) changes in soil structure in response to cycles of freezing temperatures; (iv) alterations in microbial biomass and community structure that may provide further insight into the fluctuations in GHGs after FTCs. The challenges identified included the extension of laboratory-scale research to ecosystem scales, the performance of in-depth investigation of the coupled effects of carbon, nitrogen, and water in the freeze-thaw process, and analysis of the effects of FTCs through the use of integrated research tools. The results of this study can provide a valuable point of reference for future experimental designs and scientific investigations and can also assist in the analysis of the attributes of GHG emissions from soil and the ecological consequences of the factors that influence these emissions in the context of global permafrost warming.

Freeze-thaw (F-T) weathering can alter the geometry of soils and rocks, imposing severe damage to the Earth's surface. However, it has the potential to favor the beneficiation of mineral resources. In this study, we simulated F-T weathering cycles on the graphite ore from Luobei, a seasonally frozen region in China. The deterioration of the graphite ore caused by F-T weathering was characterized by various means, including the P-wave velocity test, uniaxial compression test, optical microscope, and micro X-ray CT. The results showed that the emergence and propagation of surface defects and cracks in the graphite samples under F-T weathering resulted in weakened mechanical properties of the samples. Moreover, comminution and flotation tests indicated that F-T weathering also amplified the selective liberation between graphite and gangue minerals during crushing and grinding, which contributed to improved separation efficiency and flotation recovery of graphite with significantly reduced chemical usage and energy input. Our study offers a promising strategy for improved and more costefficient beneficiation of graphite ores in cold regions where natural F-T weathering occurs.

Freeze-thaw (FT) cycle is one of the most important factors contributing to the deterioration of expansive soil properties in seasonal frozen regions. In this study, a multiscale approach was used to investigate the impact of FT cycles on the volume deformation, mechanical properties and microstructure of expansive soil with different initial compaction states. FT cycle, unconfined compression, scanning electron microscopy and mercury intrusion porosimetry tests were carried out. The test results indicated that the volume deformation of the frozen expansive soil showed a completely opposite trend and varied in magnitude with different initial compaction states. The failure strength and elastic modulus of the expansive soil sample decreased significantly with increasing number of FT cycles. Under the impact of FT cycles, the porosity of the expansive soil increased significantly and the proportion of macropores grew. The growth of macropores and the generation of microcracks in the expansive soil were the main causes of FT damage. Besides, the FT damage variable was defined by the failure strength and had a good linear relationship with the soil porosity. In addition, the strength of loose and dense soil samples decreased significantly after FT cycles. It is found that an optimal compaction state may exist at around 95% compaction and the water content can be controlled on the dry side of the optimum water content, where FT cycles have minimal effect on the soil strength and microstructure. The study can provide guidelines for selecting the appropriate initial compaction and water content for the expansive soil projects in seasonal frozen regions.

Constructing hydraulic engineering ensures agricultural development and improves salinization environments. However, in seasonally frozen salinization regions, hydraulic engineering is prone to deformation failure. Leakage from canal raises the regional groundwater level, triggering secondary salinization environmental is-sues. Exploring the instability mechanisms is thus necessary for hydraulic engineering. Traditional deformation monitoring techniques and soil experiments are constrained by observation scale and timeliness. In this study, Sentinel-1B data from November 2017 to August 2019 were acquired. The small baseline subset (SBAS) InSAR approach was employed to interpret the seasonal deformation characteristics in both the vertical and slope di-rections of a damaged canal segment in Songyuan, Northeast China. The mechanical properties of saline-alkali soil under varying water contents were quantified by integrating unconfined compression experiment (UCE). In May, as the soil thawed downward, a frozen lenses with poor permeability formed at a depth of approximately 100 cm, causing the accumulation of meltwater and infiltrated precipitation between the frozen layer and the melting layer in the canal. The soil water content at a depth of 80 to 140 cm exceeded 22 %, reaching a threshold for rapid reduction in unconfined compression strength (UCS). Consequently, in spring, the low soil strength between the frozen layer and the melting layer resulted in interface sliding, with a displacement of-133.88 mm in the canal slope direction. Furthermore, the differential projection of freeze-thaw deformation in the slope direction caused continuous creep of the canal towards the free face, with a value of-23.27 mm, exacerbating the formation of the late spring landslide. Integrating InSAR and engineering geological analysis is beneficial for addressing deformation issues in hydraulic engineering. Ensuring the sustainable operation of hydraulic engi-neering holds important implications for mitigating the salinization process.

In cold and saline soil regions, freeze-thaw (F-T) cycles and salt erosion are two major factors determining the durability of concrete structures. This paper aims to investigate the influential mechanism and deterioration of the mechanical and microstructural properties for the concretes modified with nano-TiO2 (NT) and nano-SiO2 (NS) exposed to the coupled environment conditions of the F-T cycles and salt erosion. 180 F-T cycles were conducted on the concretes immersed in five kinds of environment media, namely, water (WF), air (AF), solution with a concentration of 5% Na2SO4 (SSF), solution with a concentration of 5% NaCl (SCF), and a mixture solution with the concentration of 5% Na2SO4 and 5% NaCl (HSF). The results indicate that the added nanoparticles and media significantly influence the overall performance of concrete samples. The SCF has the greatest influence on the degradation of concretes, following by the HSF, SSF, WF, and AF. Meanwhile, the compressive strength of concretes modified with NT is lower than that modified with NS. There is an optimal nanoparticles ratio for the nano-concrete samples to resist coupled effect of the F-T actions and salt erosion, and the optimal nanoparticles ratios for the concretes modified with NS and NT are 1% and 2%, respectively. Moreover, the filling effect on pore structure for the concretes modified with NS is better than that with NT, more hydration products and corrosion products occur on the concrete surfaces, and the crystals on the surface of concretes modified with NS are larger than that modified with NT. Furthermore, for the concretes modified with nanoparticles in the first 90 F-T actions, the gel micro-pores (5000 nm) decrease. However, the gel micro-pores decrease and the macro-pores increase within the 90-150 F-T cycles. This research would provide significant instructions on the exploration of the anti-erosion and frost-resistance of nano-concretes in marine and cold region engineering.