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Loess slopes with steep gradients are particularly prone to vertical tension cracks at the crest, resulting from unloading and other factors. These cracks significantly affect the spatiotemporal distribution of moisture infiltration during rainfall, potentially leading to slope instability. This study investigates the impact of crest-tension cracks on moisture infiltration in loess slopes under extreme rainfall conditions, focusing on crack position, depth, and width. Soil moisture content and the dynamics of wetting fronts were monitored to assess how these tension cracks influence infiltration patterns. The results indicate that tension cracks at the slope crest act as preferential infiltration pathways, causing water retention within the cracks and forming a “U-shaped” preferential infiltration zone. The extent of this “U-shaped” wetting front is influenced by the crack’s width, depth, and proximity to the slope shoulder; wider, deeper cracks closer to the shoulder result in a more pronounced wetting front. Over time, as rainfall persists, the influence of preferential infiltration decreases, and the infiltration patterns of slopes with crest cracks begin to resemble those of homogeneous slopes. In both cases, wetting fronts exhibit intersecting patterns: one parallel to the slope crest and the other parallel to the slope surface. During the initial stages of rainfall, the migration speed of wetting fronts in slopes with crest-tension cracks was significantly higher than in homogeneous slopes. However, after prolonged rainfall, the migration speeds of wetting fronts in both scenarios converged. A strong linear correlation was observed between the average migration depth of the horizontal wetting front at the slope crest and the parallel wetting front on the slope surface, for both slope types. These findings deepen our understanding of moisture migration dynamics in loess slopes with crest-tension cracks, providing insights for developing effective slope hazard mitigation strategies.

Abstract PurposeMicrobially induced calcite precipitation (MICP) has been shown to mitigate sand erosion; however, only few studies have used it on loess soils.Materials and methodsThis study used MICP to investigate the effects of this technology on the improvement of the surface erosion resistance of loess slopes. Polyvinyl acetate (PVAc) was added to the cementation solution to further increase slope stability.Results and discussionThe obtained results showed that MICP treatment resulted in an improvement of erosion resistance and treatment with 3 L/m2 bacterial suspension of Sporosarcina pasteuriiand 3 L/m2 cementation solution (0.75 M of Ca(Ac)2 and 0.75 M of urea) achieved the best erosion control and the highest surface strength. However, in rainfall simulation experiment, the eroded loss weight of loess soil in MICP-treated slopes still remained large. After adding PVAc to the cementation solution, the stability of the loess slope increased significantly and resulted in less soil loss after rainfall erosion and an increase in surface strength. With 60 g/L PVAc, the surface strength of the slope decreased by about 130 kPa compared with 40 g/L PVAc because of the thinner depth of cementation. The high erosion resistance of the slope with added PVAc could be attributed to (1) the network structure of PVAc to affix the calcium carbonate precipitation and (2) the stronger resistance to tension or shear force from PVAc. These results demonstrated that MICP-PVAc treatment significantly mitigated surface erosion of loess slopes, which presents promising potential for application in the field.

Earthquakes are one of the main factors inducing large-scale loess bedrock and especially loess-mudstone landslides in Western China, and these types of landslides are often closely related to fault zones. To study the influence of high anti-dip angle fault zones (HADAFZs) on loess-mudstone slopes (LMSs) during earthquakes, a scaled model with an HADAFZ of 80° using a shaking table test and numerical calculation, subjected to earthquake waves, was applied to reveal the rules of seismic response and failure characteristics. The acceleration dynamic response had a top surface amplification effect on the slope surface, an accelerated increase effect on the slope-surface hanging wall, an amplification effect away from the free slope face in the loess stratum, and a combination of elevation and lithology effects in the vertical section. At the loess–weathered mudstone (L–W) and weathered mudstone–mudstone (W–M) interfaces, the amplification response of a hanging wall was the largest, fault zone was the second, and foot wall was the smallest. Furthermore, the key value of input peak ground acceleration (PGA) for the dynamic response was a = 0.3 g. The hanging wall amplification effect became apparent while a > 0.3 g, and cracks appeared on the surface of the slope. The dynamic response of the soil pressure was influenced by the hanging wall amplification effect and had a positive correlation with the thickness of the overlying layers, both in the loess stratum and at the L–W interface. However, the dynamic soil pressure maximum variation (DSPMV) on both sides of the fault zone was larger than that in the fault zone. The development of an HADAFZ in the LMS hindered the integral connection of the potential sliding surface and restricted the overall sliding failure of the slope during the earthquakes.

Geological disasters occur frequently in the Loess Plateau due to the joint fissures in the strata and human engineering activities. Against this background, the deformation and failure mode of the loess slope with the structural plane under excavation and the extension mechanism of the structural plane are analyzed and summarized. The results showed that: (1) Through the physical model test, the deformation failure mode of the slope is summarized as the tension-splitting, pressure-sliding shallow failure. The collapse failure process is defined as four stages: Compression deformation, creep deformation, slip deformation and slip failure. (2) Slope displacement is concentrated beneath the pressure plate, increasing linearly under load conditions but becoming nonlinear after excavation conditions. As the excavation angle rises, the displacement range along the structural plane gradually extends toward the slope toe. The displacement time-history curve shows three stages: The lifting load stage, the cumulating deformation stage, and the sliding failure stage. (3) The stress redistribution caused by excavation, prompting deformation and potential failure. As internal stress nears the soil strength limit, human-induced disturbances exacerbate stress redistribution, leading to accumulated stress. Finally released through deformation and cracking. Each excavation condition modifies the original loading transfer path, driving stress redistribution at the slope surface and at the structural plane’s tip. (4) The sudden drop in stress level and sudden rise of accumulated settlement are the characteristics of slope sliding failure. The position of the structural plane determines the position of the slope sliding surface. (5) According to the external characterization of the structural plane, the extension process of the structural plane can be defined as four stages: Initiation of crack extension, classification deformation, subsection extension and compression sealing. According to the extension of the structural plane, the spreading cracks of the slope’s internal structural plane are defined as two types: Fractured cracks and shear cracks.

Loess landslides are one of the most important natural hazards among various landslide types in China, and rainfall is the main factor triggering loess slope instability. To gain deeper insights into the processes behind slope failure triggered by precipitation, this study conducted an indoor slope rainfall modelling test based on the case of the Shixiakou landslide in Jinzhou, Lanzhou. The test employed a custom-built rainfall simulation device, precisely controlling rainfall intensity and duration to mimic natural rainfall conditions. Soil moisture sensors, pore-water pressure transducers, and strain gauges were strategically installed within the loess slope model to monitor soil moisture dynamics, pore-water pressure variations, and lateral stress distribution in real-time. This investigation examined the progressive failure mechanism of loess slopes under rainfall infiltration through integrated monitoring. The experimental results demonstrate that sustained precipitation triggers a sequential failure process characterized by four distinct phases: initial surface scouring, subsequent basal slope instability, progressive mid-slope shear failure, and ultimate crown section collapse, and finally traction failure mode. It is worth noting that cracks play a crucial role in slope failure by creating preferential channels for water infiltration and subsequent failure development.

The long-term safety and durability of anchor systems are the focus of slope maintenance management and sustainable operation. This study presents the observed temperature, humidity, and anchor bolt stress at varying depths from four-year remote real-time monitoring of the selected loess highway cut-slope. The potential correlation between slope hydrothermal environment and anchor stress is analyzed. The anchor serviceability and durability were evaluated by establishing a time-dependent mathematical model of axial forces. The results show that the slope shallow loess exhibited hydro-thermal fluctuations annually during operation, subjecting the loess to continuous dry–wet cycles. Soil elastic deformation induces anchor axial force fluctuations due to hydro-thermo effects, while damage creep leads to the annual increase in axial force peaks and valleys. The increase in axial force is more significant at the upper slope and lower slope, thereby increasing the risk of retrogressive landslides in loess slopes. The time-dependent model of anchor axial force composing negative exponential and sine functions was proposed. The cyclic amplitudes, lower limits, and periods of temperature and humidity in slope can determine the model coefficients. The development patterns of axial force are classified into stable type, slow growth type, and accelerated growth type according to the characteristics of the model coefficients. Predicted results indicate that the anchor axial forces are lower than the landslide threshold within 30 years of slope operation, ensuring long safety and serviceability. Results provide a reference for the long-term safety evaluation and formulation of maintenance plans for loess slopes reinforced by anchor systems.

This paper aimed to screen the potential species suitable for ecological restoration and slope stability from local natural growing plants in China Loess Plateau under a semiarid climate. As part of the field investigations of local natural growing plants, potential species, which are suitable candidates for ecological restoration and slope stability, were nominated in the hilly-gullied region in the Yan'an area. The results showed that Artemisia spp. is the best candidate to form a stable root-soil composite system to support the loose loess and reinforce the loose soil, particularly suitable as pioneer plant in the initial stage of loess slope ecosystem reconstruction. Field root pull-out test and direct shear test for soil without roots and root-soil composite systems were conducted to analyse the reinforcement effect of Artemisia spp. The results from quantitative analysis of the slope protection effect showed that the slope safety factor could be obviously improved by the growth of Artemisia spp. As the survey, test, stability analysis and case study shown, Artemisia spp. can effectively prevent the occurrence of loess flow slides and shallow landslides, which has extensive application prospect.

Rainfall-induced instability of loess slopes presents significant threats to infrastructure and ecological systems. Vegetation serves as an effective measure to enhance slope stability through mechanical reinforcement by roots and hydrological regulation of soil moisture. The influence of vegetation root system characteristics, including root tensile strength and rooting depth, on the stability of loess slopes subjected to rainfall infiltration is investigated using a finite element model developed in COMSOL®, which couples seepage and mechanical behavior. Rainfall infiltration, pore water pressure evolution, and progressive slope failure are simulated to analyze the stability response. Varying levels of additional cohesion provided by roots and different rooting depths are systematically evaluated. The results indicate that stronger root systems and deeper rooting depths significantly enhance slope stability by increasing the factor of safety, delaying plastic zone development, and reducing displacement. The reinforcement effect becomes more pronounced on steeper slopes, while its marginal contribution diminishes with increasing root depth beyond a certain threshold. These findings provide insights into the role of vegetation in mitigating rainfall-induced slope failures and provide practical guidance for the selection and application of vegetation in ecological slope stabilization projects.

In order to effectively reduce the impact of rainfall-induced landslides on properties and life, it is important to understand rainfall-caused landslides and their sliding mechanisms. The objective of this paper is to study the effects of different rainfall patterns and different slope structures on the deformation and failure process of shallow loess slopes. To achieve the objective, three categories of indoor physical model experiments of a loess slope with and without a vertical joint were implemented under different rainfall patterns. Three kinds of sensors, including volumetric water content, matric suction, and pore-water pressure sensors, were buried in the model slopes to record the internal changes driving deformation. Analyses of the sensor records and the associated deformational changes, and the experimental results under different conditions show that the matric suction in loess slopes decreased gradually. Loess strength reduced with the continuous increase of volumetric water content. After excess pore-water pressure was generated by the slope deformation and poor drainage of the loess, it decreased the effective stress and the loess strength, which resulted in landslides. In addition, it was observed that the influence of slope structure on stability was greater than that of rainfall patterns. This paper attempts to explain the failure mode and triggering mechanisms of shallow loess landslides induced by rainfall.