Loss of matric suction during rain has an important effect on the instability of expansive soil slope. A new device was designed for testing the expansive force in order to propose and determine the equivalent expansive force corresponding to the matric suction. First, the internal relation between the matric suction and the corresponding equivalent expansive force of unsaturated expansive soil was analyzed. Then, numerical algorithm implementation of the equivalent expansive force was discussed, and the equivalent expansive force was introduced into the strength reduction finite element method (FEM). Finally, the equivalent effects of the matric suction and the equivalent expansive force were compared and analyzed by evaluating the stability of an unsaturated expansive soil slope. The results show that the new testing device significantly improves the accuracy of the expansive force test and shortens the testing time. The relation between the matric suction and the equivalent expansive force with the change in initial water content is obvious. The equivalent expansive force can reflect the macro contribution of matric suction to unsaturated expansive soil, and the developed strength reduction FEM based on the equivalent expansive force can be used to evaluate the rainfall-induced instability of an expansive soil slope caused by the decrease in matric suction resulting from the rainfall infiltration.

When tests are conducted on the field slope under artificial rainfall, because artificial rainfall is often limited to implementation in the mode of local rainfall, there is a boundary constraint effect between the rainfall area and the non-rainfall area, which is manifested in the lateral infiltration of rainwater and the slope deformation retardation of non-rainfall area to the rainfall area. Firstly, a deep-buried isolated trench was proposed to solve these boundary constraints. Then, field cracking tests and the corresponding numerical simulation were conducted under rainfall. In the end, the response of water content and the cracking failure characteristics of the slope were analyzed during rainfall, and the effect of a deep-buried isolated trench on the cracking characteristics of the slope was evaluated. The results indicate that the proposed deep-buried isolated trench measure can effectively eliminate the deformation retardation resulting from the adjacent non-rainfall area so a through-crack parallel to the slope shoulder that extended on both sides of the boundary of the rainfall slope was observed at the slope crest and a cracking failure in the shape of the overall downward cutting was realized. As the crack occurred, the rainwater infiltration further aggravated expansion of depthwise cracks, and a local sliding zone was formed in the upper part of the slope. The deep-buried isolated trench solves the boundary constraints, such as lateral infiltration of rainwater and deformation retardation, and can provide an effective technical measure for the field slope test under artificial rainfall.

To avoid large deformation, resulting from liquefaction, in inclined and deeply deposited liquefiable soil, it is necessary to design economical and reasonable reinforcement schemes. A reinforcement scheme employing subarea long-short gravel piles was proposed, and it was successfully applied in the embankment construction of the Aksu-kashgar highway. To reveal its underlying mechanism and effect on the seismic performance of the highway, the dynamic responses of natural foundation and two kinds of reinforced foundations were analyzed and compared under this scheme, using the program FEMEPDYN. Results showed that both the seismic subsidence and the excess pore pressure ratios were far less in the foundation reinforced with isometric gravel piles and in the foundation reinforced with subarea long-short gravel piles, compared with that in natural foundation. Therefore, the potential hazards of liquefaction were overcome in these two kinds of reinforced foundations. Furthermore, it was obvious that the shielding region only formed within the foundation reinforced with subarea long-short gravel piles. With the shielding effect, the proposed reinforcement scheme employing subarea long-short gravel piles not only eliminated liquefaction in deeply deposited liquefiable soil, but it also demonstrated an outstanding advantage in that the total length of gravel piles used was greatly reduced compared to the total length in the isometric gravel piles scheme and the interphase long-short gravel piles.

Oil leakage will not only pollute the soil but also change its physical-mechanical behavior, and loess has complex properties in the environment of oil presence. Artificial loess contaminated by diesel oil is collected as the research object. The physical and mechanical properties of clean loess and contaminated loess, including liquid and plastic limits, permeability, compression properties, and compressive strength characteristics, are estimated through a series of laboratory tests under different oil contents, water contents, and dry densities. Results show that liquid limits, plastic limits, and permeability coefficient of diesel-contaminated loess decrease with the increase of oil content. The compression modulus and compressive strength of diesel-contaminated loess increase with the increase of dry density at the same oil content. Adding diesel oil, the change law of the unconfined compressive strength of contaminated loess is opposite at the two different water contents. The variation of the compression modulus and unconfined compressive strength of diesel oil-contaminated loess is basically identical at the same condition. The findings of this study would be expected to bridge the gap between theory and practice in treatment and remediation of contaminated soil in the region of oil production.

When loess is contaminated by oil, different modes of contamination will have a certain impact on the mechanical behaviors of loess in the oil-production areas. This study is aimed at evaluating the effect of diesel oil contamination on mechanical behaviors of loess through extensive laboratory tests. Two different modes of oil contamination were proposed and applied in compression tests, direct shear tests, and unconfined compressive strength tests to study the compressibility and strength characteristics of diesel-contaminated loess. Results show that two different modes of oil contamination have significant effects on the mechanical behaviors of loess. In comparison with clean loess, the compressibility of contaminated loess increases, and its unconfined compressive strength and shear strength all decrease under the first mode of oil contamination. The compression modulus, friction angle, and unconfined compressive strength of diesel oil-contaminated loess using the second mode of oil contamination are larger than those in the first mode of oil contamination at the same oil content and dry density. Understanding these effects on mechanical behaviors of loess under different modes of oil contamination can significantly guide soil and environment-remediation activities in loess oil-production areas.

The large-scale accumulation of lithium-feldspar tailings generated during lithium ore beneficiation poses environmental and resource-utilization challenges. Cemented lithium-feldspar tailings backfill (CLFTB) provides an effective approach for their underground disposal and resource utilization; however, its mechanical performance remains a key concern. Nanocellulose, with its high specific surface area and fibrillar structure, has potential for improving the stability and mechanical properties of cementitious tailings backfill. This study investigates the effects of nanocellulose type and dosage on the macro- and micro-scale performance of CLFTB. Three nanocellulose types, namely carboxylated cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and microfibrillated cellulose (MFC), were incorporated at dosages of 0.6–1.5 kg/m³. Uniaxial compressive-strength tests and microstructural analyses were conducted to evaluate their effects. The results showed that all nanocellulose-modified groups exhibited higher compressive strength than the control group. The optimum dosage was 0.9 kg/m³, while MFC provided the greatest strength enhancement among the three nanocellulose types. Nanocellulose incorporation also altered the failure behavior and mitigated crack propagation. EDS analysis further revealed differences in the local elemental characteristics of the modified specimens. Overall, the results demonstrate that nanocellulose, particularly MFC, can effectively enhance the mechanical performance and stability of CLFTB.