The frequent occurrence of earthquakes worldwide has rendered highway slope protection projects highly vulnerable to damage from seismic events and their secondary disasters. This severely hampers the smooth implementation of post-disaster rescue and recovery efforts. To address this challenge, this study proposes a comprehensive method for assessing seismic losses in slope protection projects, incorporating factors such as topography and elevation to enhance its universality. The method categorizes seismic losses into two main components: damage to protection structures and costs associated with landslide and rockfall clearance and transportation. This study estimates the cost range for common protection structures and clearance methods under general conditions based on widely recognized quota data in China. It establishes criteria for classifying the damage states of protection structures and provides loss ratio values based on real-world seismic examples and expert experience, constructing a model for assessing damage losses. Additionally, by summarizing the geometric characteristics of soil and rock accumulations on road surfaces, a method for estimating landslide volumes is proposed, considering the dynamic impact of slope gradients on clearance and transportation volumes, and a corresponding cost assessment model for clearance and transportation is developed. The feasibility and reliability of the proposed method are verified through two case studies. The results demonstrate that the method is easy to implement and provides a scientific basis for improving relevant standards and practices. It also offers an efficient and scientific tool for loss assessment to industry practitioners.

The restraining effect of soilbags inhibits soil dilatancy, enhancing the strength and stiffness of the wrapped soil. As a permanent slope protection structure (SSPS), the application of counterpressure enhances stability by improving slope surface stiffness and limiting deformation. While reinforced slopes have been extensively studied, mechanistic investigations into the stability and failure processes of SSPS remain limited. This study numerically investigated the macro-meso mechanisms of SSPS instability using the discrete element method. Macroscopically, rainfall infiltration increases water absorption, resulting in longitudinal settlement, deformation, and eventual instability. With a friction coefficient of 0.5, the lower soilbags resist sliding forces until the front soilbags are damaged. Inadequate sufficient friction causes the front soilbags to be displaced outward, leading to structural collapse as the lower soilbags bear the additional load. Microscopically, geosynthetic wrapping restrains soil dilatancy, promoting tighter particle arrangements and secondary reinforcement through soilbag expansion. During instability, primary contact forces concentrate on longitudinal settlement, vertical back pressure, and downslope sliding, with force chain evolution revealing slip band formation. Soilbags facilitate coordinated particle deformation and stress distribution, transitioning from anisotropic to isotropic states as instability progresses. These findings enhance the understanding of SSPS instability mechanisms, providing guidance for more reliable design and construction practices.

Soil cement is a construction material with significant potential for widespread application in water resource management, particularly in providing overtopping protection for levees. However, the requirement for base soil to have a specific particle composition-predominantly coarse particles with minimal fine particles-limits its broader practical use. This study focuses on clarifying the erosion resistance of soil-cement material manufactured from clayey silt (ML) soil, a type of soil that does not meet the Portland Cement Association's requirements for mixing with fly ash and cement. Hydraulic model experiments were conducted to assess the erosion resistance of this soil-cement material under overflow conditions. Remarkably, the results showed high erosion resistance, withstanding flow velocities exceeding 6.15 m/s with minimal erosion damage. This level of performance suggests that the ML soil-fly ash-cement solution is well-suited for protecting levees up to 4 m in height during overtopping events. Specifically, for levees with a height of 3 m and slope coefficients of m = 2 and m = 3, the permissible overflow depths are 0.4 m and 0.5 m, respectively. For 4 m-high levees with the same slope coefficients, the permissible overflow depths are 0.3 m and 0.4 m, respectively. Elucidating the erosion resistance of soil cement made from ML soil is expected to promote the application of this material for levee protection during overtopping scenarios.

External-soil spray seeding technology is a widely used method for ecological slope protection, playing a significant role in mitigating soil erosion, landslides, and other geological challenges. However, research on the technical stability of external-soil spray seeding is limited, resulting in suboptimal protective effects and hindering broader application. This review highlights emerging research themes for advancing ecological slope stability, including: ecological substrate, vegetated ecosystem, the mechanical properties and hydrological characteristics of the external-soil spray seeding technology. The review identifies new research themes for developing futuristic ecological slopes can be summarized as: (1) whether or not to find the stability models on the shear strength and bond strength of the substrate under water saturation, (2) how to establish models with the effect of grassland ratio, slope angle, seeding amount, and planting season on the long-term growth of ecological slope protection, (3) how to improve quantitative mechanical models between the roots and soil, (4) how to propose the relevant analytical and numerical methods for root-soil-atmosphere. The findings offer valuable guidelines for improving ecological slope stability and advancing the application of external-soil spray seeding technology.

Vegetation concrete is one of the most widely used substrates in ecological slope protection, but its practical application often limits the growth and nutrient uptake of plant roots due to consolidation problems, which affects the effectiveness of slope protection. This paper proposed the use of a plant protein foaming agent as a porous modifier to create a porous, lightweight treatment for vegetation concrete. Physical performance tests, direct shear tests, plant growth tests, and scanning electron microscopy experiments were conducted to compare and analyze the physical, mechanical, microscopic characteristics, and phyto-capabilities of differently treated vegetation concrete. The results showed that the higher the foam content, the more significant the porous and lightweight properties of the vegetation concrete. When the foam volume was 50%, the porosity increased by 106.05% compared to the untreated sample, while the volume weight decreased by 20.53%. The shear strength, cohesion, and internal friction angle of vegetation concrete all showed a decreasing trend with increasing foaming agent content. Festuca arundinacea grew best under the 30% foaming agent treatment, with germinative energy, germinative percentage, plant height, root length, and underground biomass increasing by 6.31%, 13.22%, 8.57%, 18.71%, and 34.62%, respectively, compared to the untreated sample. The scanning electron microscope observation showed that the pore structure of vegetation concrete was optimized after foam incorporation. Adding plant protein foaming agents to modify the pore structure of vegetation concrete is appropriate, with an optimal foam volume ratio of 20-30%. This study provides new insights and references for slope ecological restoration engineering.

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).

Bedding slope is a typical heterogeneous slope consisting of different soil/rock layers and is likely to slide along the weakest interface. Conventional slope protection methods for bedding slopes, such as retaining walls, stabilizing piles, and anchors, are time-consuming and labor- and energy-intensive. This study proposes an innovative polymer grout method to improve the bearing capacity and reduce the displacement of bedding slopes. A series of large-scale model tests were carried out to verify the effectiveness of polymer grout in protecting bedding slopes. Specifically, load-displacement relationships and failure patterns were analyzed for different testing slopes with various dosages of polymer. Results show the great potential of polymer grout in improving bearing capacity, reducing settlement, and protecting slopes from being crushed under shearing. The polymer-treated slopes remained structurally intact, while the untreated slope exhibited considerable damage when subjected to loads surpassing the bearing capacity. It is also found that polymer-cemented soils concentrate around the injection pipe, forming a fan-shaped sheet-like structure. This study proves the improvement of polymer grouting for bedding slope treatment and will contribute to the development of a fast method to protect bedding slopes from landslides.

Traditional slope protection methods face many challenges when applied to carbonaceous mudstone slopes. The objective of this study was to develop a novel protection method based on vegetation concrete with carbonaceous mudstone aggregates (VCCMA) and then examine its performance and underlying protective mechanism. Hence, physical model tests were performed on highly-weathered carbonaceous mudstone slopes under wet-dry cycles considering three different protection cases, i.e., no protection, protection using porous concrete with carbonaceous mudstone aggregates (PCCMA) and protection using VCCMA. The erosion characteristics, volumetric moisture contents, and slope deformations of the slopes were measured. Finally, the performances and underlying mechanisms of the protection methods for slopes were compared. The results demonstrate that the unprotected slope, the PCCMA-protected slope, and the VCCMA-protected slope were descending according to the erosion damage, the particle loss amount, and the deformation during five wet-dry cycles. Among the two protected cases, the VCCMA exhibits better erosion coefficient, water retention capacity and disintegration resistance of the slope. The runoff volume depends on the protection method and shows a weaker correlation with wet-dry cycles. In the case of PCCMA protection, the protection effects come from self-weight consolidation, water interception, and integral protection structure. The VCCMA protection case incorporates additional protective mechanisms, including soil moisture regulation by leaf transpiration, resistance to rainfall splashing and scouring by stems and leaves, and soil reinforcement and anchoring by roots. Therefore, the VCCMA holds significant potential for effectively protecting problematic slopes. These findings provide valuable guidance for the protection of highly-weathered carbonaceous mudstone slopes.