To dispose of the large amount of OSA (oil shale ash) and FA (fly ash) in Northeast China, a novel subgrade material obtained by modifying SC (silty clay) with OSA and FA was produced. First, the effect of F-T (freeze-thaw) cycles and stress states on the resilient modulus of unmodified SC and the modified SC were investigated. Second, the damage ratio was introduced to describe the relationship of resilient modulus versus F-T cycles. Third, the effect of F-T cycles on the microstructure of soils was investigated. The results indicate that in addition to stress state, resilient modulus is significantly influenced by F-T cycles. For unmodified SC, the resilient modulus continually decreases with increasing F-T cycles. As for the modified soil, the resilient modulus decreases sharply after the first F-T cycle and then tends to be stable. The damage ratio and its fitting equation are effectively adopted to describe the variation characteristic of the resilient modulus after F-T cycles. As observed from SEM testing, the effect of F-T cycles on soils is to destroy the initial structure and increase the porosity of soils. It could be concluded that the microstructure change during F-T cycles is the main factor that results in the decrease of the resilient modulus.

To reduce the impact of road ice and snow disaster, it is necessary to adopt low energy consumption and efficient active deicing and snow melting methods. In this article, three functional components are combined into a conductive ethylene propylene diene monomer (EPDM) rubber composite material with good interface bonding. Among them, the mechanical and electrical properties of the composite material are enhanced by using carbon fiber cloth as a heating layer. EPDM rubber plays a mainly protective role. Further, aluminum silicate fiber cloth is used as a thermal insulation layer. The mechanical properties of EPDM rubber composites reinforced by carbon fiber cloth and the thermal behaviors of the composite material in high and low temperature environments were studied. The heat generation and heat transfer effect of the composite were analyzed by electrothermal tests. The results show that the conductive EPDM rubber composite material has good temperature durability, outstanding mechanical stability, and excellent heat production capacity. The feasibility of the material for road active deicing and snow melting is verified. It is a kind of electric heating deicing material with broad application prospects.

To achieve the purposes of storing industry solid wastes and enhancing subgrade stability in seasonally frozen regions, Structure III, which utilized the modified silty clay (SC) and extruded polystyrene (XPS) board as a novel subgrade thermal insulation layer (NSTIL), was presented. The above modified SC consisted of oil shale industry solid waste, fly ash and SC. In terms of environmental impact, the average single pollution index, the Nemerow integrated pollution index and national standards were carried out to estimate whether the modified SC could be used as a subgrade filler. These results show that, although the modified SC will produce pollution to the environmental background, the concentration of each hydrochemical constituent from the modified SC meets the corresponding national standards in China. In terms of the thermal insulation capability, the numerical simulation of coupling moisture and temperature was applied to analyze that of Structures I, II and III. The research results show that the numerical results of the Structure I are approximated to the official website information of Jilin province, indicating that the above numerical simulation is effective for coupling moisture and temperature of frozen soil. Both modified SC and NSTIL have the advantage of good thermal insulation property, but the thermal insulation property of the NSTIL is greater. Furthermore, the NSTIL at the top of the Structure III can protect the SC of the experimental road from the damage of frost heave. The research results are of great significance for reducing environmental pollution caused by oil shale industry solid waste and fly ash, increasing the utilization rate of industrial waste and enhancing the subgrade stability in seasonally frozen regions.

Winter irrigation is widely carried out to alleviate soil salinization in Northwest China. In recent years, the effects of irrigation amount and irrigation schedule on soil water and salt distribution and water use efficiency (WUE) during crop growth periods have been extensively studied, but the effects of winter irrigation on water use efficiency have been generally ignored. This work was conducted from November 2018 to October 2020 in two kinds of saline-alkali farmlands (mild saline-alkali farmland and moderate saline-alkali farmland) with five winter irrigation amounts (0, 150, 225, 300 and 375 mm). The results indicated that, during the winter irrigation period, the maximum moisture content layer in the soil becomes more shallow with the increase in the winter irrigation amount and the salinity of the soil. The salt return process mainly occurs during the late thawing period. After two years, for a winter irrigation amount of 150 mm to 375 mm, the change rate of soil salt in mild saline-alkali farmland decreased from −2.50% to −15.38% in the 0–100 cm profile, and that value in moderate saline-alkali farmland decreased from 12.22% to −16.85%. Compared with the non-winter irrigation treatment, the sprouting rate, survival rate, morphological index and cotton yield in the coming year are greater under the winter irrigation treatment. For mild saline-alkali farmland and moderate saline-alkali farmland, to keep soil desalinated, enhance cotton growth and save water resources, the recommended winter irrigation amounts are 225 mm and 300 mm, respectively. The research methods and results are of great significance for rationally evaluating the sustainable winter irrigation amount for cotton fields under mulched drip irrigation in different saline-alkali farmlands.

For strengthening sustainability of subgrade life-cycle service performance and storing industry solid wastes in seasonally frozen regions, compared to previous research of modified silty clay (MC) which consisted of oil shale ash (OSA), fly ash (FA), and silty clay (SC), we identified for the first time, the variations in the thermal insulation capability of MC with different levels of dry density and moisture content. Taking into consideration the effects of 0–20 freeze-thaw (F-T) cycles by a laboratory test, and by the numerical simulation of coupling moisture-temperature, while considering the effects of F-T cycles, the thermal insulation capability of the MC board and the XPS board were studied quantitatively. The testing results show that the thermal conductivity of MC and SC gradually decreases as the number of F-T cycles increases, and that of the XPS board increases with the increased number of F-T cycles, and tend to be of a constant value of 0.061 W/m/K after 17 F-T cycles. The specific heat capacity of the solid particles of the MC, SC, and XPS board does not change regularly as their moisture content, and the number of F-T cycles change, and their variations are in the range of the test error (2%). Simulation results show that MC has the advantage of the thermal insulation property to reduce the frost-depth of 0.21 m, and the thermal insulation property of the composite layer consisting of the MC and XPS board is greater to reduce the frost-depth of 0.55 m, so that it can protect both the SC and sand gravel of the experimental road from the frost heave damage. The research methods and results are very significant in accurately evaluating the thermal insulation capacity and the sustainability of MC and the composite layer consisting of the MC and XPS board, strengthening the stability of the subgrade and increasing the availability of industrial waste.

To achieve the purposes of disposing industry solid wastes and enhancing the sustainability of subgrade life-cycle service performance in seasonally frozen regions compared to previous research of modified silty clay (MSC) composed of oil shale ash (OSA), fly ash (FA), and silty clay (SC), we identified for the first time the axial deformation characteristics of MSC with different levels of cycle load number, dynamic stress ratio, confining pressure, loading frequency, and F-T cycles; and corresponding to the above conditions, the normalized and logarithmic models on the plastic cumulative strain prediction of MSC are established. For the effect of cycle load number, results show that the cumulative plastic strain of MSC after 1, 10, and 100 cycle loads occupies for 28.72%~35.31%, 49.86%~55.59%, and 70.87%~78.39% of those after 8000 cycle loads, indicating that MSC possesses remarkable plastic stability after 100 cycles of cycle loads. For the effect of dynamic stress ratio, confining pressure, loading frequency, and F-T cycles, results show that dynamic stress ratio and F-T cycles are important factors affecting the axial deformation of MSC after repeated cycle loads; and under the low dynamic stress ratio, increasing confining pressure and loading frequency have insignificant effect on the axial strain of MSC after 8000 loads. In term of the normalized and logarithmic models on the plastic cumulative strain prediction of MSC, they have a high correlation coefficient with testing data, and according to the above models, the predicted result shows that the cumulative plastic strain of MSC ranges from 0.38 cm to 2.71 cm, and these predicted values are within the requirements in the related standards of highway subgrades and railway, indicating that the cumulative plastic strain of MSC is small and MSC is suitable to be used as the subgrade materials.