Soil modification is an effective method for enhancing the mechanical properties, including its strength, deformation capacity, and dynamic mechanical stability. Nanomaterials have broad prospects in soil modification due to their small particle size, large specific surface area, and non-toxic and harmless properties. Using the laboratory dynamic triaxial test method, this paper presents a scientific evaluation on the dynamic stability and freeze-thaw resistance of loess modified with nano-silica. This study has investigated the effects of nano-silica content, dynamic stress amplitude, confining pressures, and freeze-thaw cycles on the cumulative deformation behavior of nano-silica modified loess subjected to cyclic loading. Based on the shakedown theory, the shakedown state of 60 samples was evaluated, and an equation for the critical dynamic stress of modified loess was established under the shakedown limit state. The experimental results show that nano-silica can effectively fill the micropores in soil and form a cohesive gel that enhances the bonding between soil particles, significantly increasing the cohesion of the loess due to its nanoscale (10- 9) small size. The 2.5 % content of nano-silica is the optimal dosage for reinforcing loess. Under the same confining pressure condition, the failure strength of the 2.5 % nano-silica modified loess is about 1.4-2.1 times that of the loess, and the residual strength is about 1.2-1.5 times that of the loess. The incorporation of nano-silica significantly improves the dynamic stiffness and freeze-thaw resistance of loess, increasing the reinforcement factor by 51 %-69 % under unfrozen conditions and still increasing it by 43 %-64 % after experiencing one freeze-thaw cycle. Similarly, nano-silica significantly enhanced the dynamic strength and strength parameters of loess. Nano-silica exerts an influence on the shakedown state of the soil, wherein the impact becomes more significant with increasing dynamic stress amplitude.

Loess is a geological formation with poor geotechnical performances. To upgrade and allow use of this kind of material in civil engineering projects, it is common to add few percent of hydraulic binders. However, the mechanical properties of those materials are often estimated. Their performances are thus sharply downgraded during structure design processes of road structures and their uses are generally limited to the capping layer. However, it is possible to measure accurately mechanical performances of these materials to use them in subbase layers of pavements. Based on results, a design has been proposed and implemented on a real scale test section. The test has been instrumented with strain gauges and preliminary results are presented.

This research focuses on soils derived from volcanic ash in the city of Popayan, stabilized with low percentages of cement. The results reveal high variability in properties due to changes in moisture content, structural condition, and curing time. The study involved evaluating the physical and mechanical properties in both natural state and after modification with cement at 3%, 4%, and 5%. Natural state soils exhibit deficient conditions, such as subgrades or embankments, necessitating improvement in various cases. When cement is used as a stabilizer, it is possible to conclude that there is an increase in mechanical strength and marginal improvements in hydraulic properties (cement- modified soil). However, these improvements are not comparable to the significant enhancements observed after reaching a 5% cement content (soil-cement).

In cold regions, freeze-thaw cycles (FTCs) can alter the properties of soil used as a foundation filler, leading to failures in foundation engineering. The increase in biomass power plants has resulted in a significant amount of waste biomass ash, causing negative environmental impacts. To address these issues, waste wheat straw biomass ash (WSBA) is harnessed to enhance the properties of silty clays. This study examines how WSBA affects the mechanical properties and microstructure of silty clay after FTCs through FTCs tests, Triaxial tests, and Scanning Electron Microscopy (SEM) tests. The findings reveal that incorporating WSBA significantly enhances the mechanical properties and microstructure of the soil by filling internal pores and strengthening its structure. The mechanical properties of all soil samples exhibit significant deterioration after 1 FTC, with gradual stabilization ensuing after 6 FTCs. Notably, WSBA-modified samples show better resistance to freeze-thaw weathering compared to unmodified samples, particularly at a WSBA content of 10%. Furthermore, the study establishes empirical formulas linking mechanical parameters, freeze-thaw cycles, and WSBA content using binary quadratic equations. The investigation results could serve as a valuable reference for projects involving roadway subgrade backfill materials in regions with seasonal frozen soil.

Large quantities of abandoned marine soft soil are generated from coastal engineering which cannot be directly utilized for construction without modification. The utilization of traditional binders to modify abandoned marine soft soil yields materials with favorable mechanical properties and cost efficiency. However, the production of traditional binders like cement leads to environmental pollution. This study uses a CGF all-solid-waste binder (abbreviated as CGF) composed of industrial solid waste materials such as calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS), and fly ash (FA), developed by our research team, for the modification of abandoned marine soft soil (referred to as modified soil). It is noteworthy that the marine soft soil utilized in this study was obtained from the coastal area of Jiaozhou Bay, Qingdao, China. Physical property tests, compaction tests, and unconfined compressive strength (UCS) tests were conducted on the modified soil. The investigation analyzed the effects of binder content, compaction delay time, and curing time on the physical, compaction, and mechanical properties of CGF-modified soil and cement-modified soil. Additionally, microscopic experimental results were integrated to elucidate the mechanical improvement mechanisms of CGF on abandoned marine soft soil. The results show that after modification with binders, the water content of abandoned marine soft soil significantly decreases due to both physical mixing and chemical reactions. With an increase in compaction delay time, the impact of chemical reactions on reducing water content gradually surpasses that of physical mixing, and the plasticity of the modified soil notably modifies. The addition of binders results in an increase in the optimum moisture content and a decrease in the maximum dry density of CGF-modified soil, while the optimum moisture content decreases and the maximum dry density increases for cement-modified soil. Moreover, with an increase in binder content, the compaction curve of CGF-modified soil gradually shifts downward and to the right, while for cement-modified soil, it shifts upward and to the left. Additionally, the maximum dry density of both CGF-modified and cement-modified soils shows a declining trend with the increase in compaction delay time, while the optimum moisture content of CGF-modified soil increases and that of cement-modified soil exhibits a slight decrease. The strength of compacted modified soil is determined by the initial moisture ratio, binder content, compaction delay time, and curing time. The process of CGF modification of marine soft soil in Jiaozhou Bay can be delineated into stages of modified soil formation, formation of compacted modified soil, and curing of compacted modified soil. The modification mechanisms primarily involve the alkali excitation reaction of CGF itself, pozzolanic reaction, ion-exchange reaction, and carbonization reaction. Through quantitative calculations, the carbon footprint and unit strength cost of CGF are both significantly lower than those of cement.