Ground subsidence is a common urban geological hazard in several regions worldwide. The settlement of loess fill foundations exhibits more complex subsidence issues under the coupled effects of geomechanical and seepage-driven processes. This study selected 21 ascending Sentinel-1 A radar images from April 2023 to October 2024 to monitor the loess fill foundation in Shaanxi, China. To minimize errors caused by the orbital phase and residual flat-earth phase, this research combined PS-InSAR technology with the three-threshold method to improve the SBAS-InSAR processing workflow, thereby exploring time-series deformation of the loess fill foundation. Compared with conventional SBAS-InSAR technology, the improved SBAS-InSAR technique provided more consistent deformation time-series results with leveling data, effectively capturing the deformation characteristics of the fill foundation. Additionally, geographic information system (GIS) spatial analysis techniques and statistical methods were employed to analyze the overall characteristics and spatiotemporal evolution of the ground surface deformation in the study area. On the other hand, the major drivers of the subsidence in the study area were also discussed based on indoor experiments and engineering geological data. The results showed gradual and temporal shifts of the subsidence center toward areas with the maximum fill depths. In addition, two directions of uneven subsidence were observed within the fill foundation study area. The differences in the fill depth and soil properties caused by the building foundation construction were the main factors contributing to the uneven settlement of the foundations. Foundation deformation was also positively and negatively affected by surface water infiltration. This study integrates remote sensing and engineering geological data to provide a scientific basis for accurately monitoring and predicting loess fill foundation settlement. It also offers practical guidance for regional infrastructure development and geological hazard prevention.

Setting an expandable polystyrene (EPS) board on box culverts can reduce the vertical earth pressure (VEP) acting on the culvert roof. However, long-term backfill load will induce creep in both the EPS board and the surrounding soil, resulting in a change in the stress state of the culvert-soil system. A mechanical model for the long-term interaction of backfill-EPS board-box culvert was established, and theoretical formulas were derived for calculating the earth pressure around the culvert. Numerical simulation was employed to validate the accuracy of the proposed theoretical approach. Research indicates that, with EPS board, the VEP decreases rapidly then slightly increases with time and eventually approaches an asymptotic value, ultimately decreasing by 33%. However, the horizontal earth pressure (HEP) shows the opposite pattern and ultimately increases by 15%. The foundation contact pressure (FCP) increases nonlinearly and reaches a stable value, ultimately increasing by 10.2%. Without the EPS board, the VEP and HEP are significantly different from those with the EPS board. Although EPS boards can reduce the VEP on the culvert, attention should be paid to the variation of HEP caused by the creep of the EPS board and backfill.

The stability of loess high-fill slopes is a crucial issue in engineering, where the presence of fissures significantly impacts slope stability. This study investigates the seepage-mechanical response and fissure evolution characteristics of loess high-fill slopes under the coupled effects of consolidation, rainfall, and evaporation through model testing. The disaster chain evolution process of the slope under these coupled effects is revealed. The results show that the development of fissures in loess high-fill slopes does not follow a directional pattern and has a uniform influence on soil properties. Under rainfall, the slope exhibits preferential flow paths, which guide the deformation and failure modes. With the development of fissures, the fill material shows a cumulative damage effect, leading to progressive performance degradation and continuous decline in slope stability. This study enriches the theoretical framework for stability analysis of high-fill fissured slopes and provides guidance for disaster prevention and mitigation in loess regions.

Laying geogrids and compressible materials, such as expandable polystyrene (EPS), on the tops of culverts under high fill can improve the stability of the fill and reduce the earth pressure on the tops of culverts. The creep of geogrids and compressible materials under high fill affects the stress state of culvert - soil systems. However, the long-term behaviour of culverts with geogrids and EPS is not clear. This paper investigates the long-term behaviour of culvert - soil interactions under high fill, specifically focusing on the creep effects of geogrids and EPS boards. A novel mechanical model for determining the long-term stress characteristics of culverts is proposed based on limit equilibrium theory. A comparison with finite difference simulation results was conducted to validate the proposed model. The findings reveal that the vertical earth pressure on the culvert top gradually transfers to the culvert side, exhibiting a nonlinear decrease over time. Moreover, the horizontal earth pressure on the culvert sidewall exhibits nonlinear growth with time, decreasing incrementally with depth. The maximum horizontal earth pressure on the culvert sidewall increases by 12.5% postconstruction, emphasizing the importance of accounting for the creep effects of geogrids and EPS boards in engineering design to prevent structural issues.

Creep deformation control is the key point and difficulty in the construction of loess high fill, the creep characteristics of loess with different compactness and confining pressure conditions has been studied. To achieve the objective, the influence of different conditions on the creep deformation characteristics of loess were analyzed by the triaxial creep tests of loess under different compaction and confining pressures. The results show that the instantaneous deformation of the soil samples gradually decrease with increasing compactness, and the total creep deformation also decreases. With the increase of confining pressure, the deformation increase gradually with the compactness decreased. Finally, in order to describe the creep process of loess, the creep model suitable for different compactness is proposed, which is based on fractional calculus and the continuous damage theory. Through fitting verification, the applicability of the theoretical model to the description of loess creep characteristics is proved, and then the whole stages of loess creep can be better described.

The problems of gully and soil erosion caused by large-scale urban construction and agricultural development in China have become more and more serious in recent years. In an effort to solve this problem, a series of gully stabilization and highland protection projects have been carried out on the Loess Plateau, and this has resulted in a large number of high-loess-filled-slopes (HLFSs). Although these filled slopes uses several different mitigation measures, the HLFSs have been eroded and destroyed under the action of water. In order to study the influence of different mitigation measures on the stability of HLFSs and their failure process, this paper uses a flume test of the effects of various mitigation measures on this failure process. The results show that: (1) the failure processes of slopes with different mitigation measures are obviously different. Slope deformation u with a declining gradient mitigation mainly occurs on the surface of the slope body, and although slope erosion is quite serious, the slope does not fail as a whole. Slopes with a stepwise drainage channel mitigation show little erosion, but material can easily slide along the horizontal drainage channels. (2) The slope deformation process is correlated with changes in pore-water pressure. When local instability occurs, there is always a pre-process of continuously rising pore-water pressure. When a failure occurs, the pore-water pressure of the soil at each position of the slope body suddenly fluctuates under instantaneous excitation. (3) The response of soil pore pressure and the development characteristics of tension cracks affect the deformation of the slopes, which is also the cause of the differences slope instability caused by different mitigation measures. These research results provide reference for the protection of HLFS engineering projects from heavy rains.