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We report the experimental application of distributed optical fiber sensors, based on stimulated Brillouin scattering (SBS), to the monitoring of a small-scale granular slope reconstituted in an instrumented flume and subjected to artificial rainfall until failure, and to the monitoring of a volcanic rock slope. The experiments demonstrate the sensors’ ability to reveal the sudden increase in soil strain that foreruns the failure in a debris flow phenomenon, as well as to monitor the fractures in the tuff rocks. This study offers an important perspective on the use of distributed optical fiber sensors in the setting up of early warning systems for landslides in both rock and unconsolidated materials.

Due to the inherently unfavorable geological conditions coupled with various triggering factors, reservoir bank slopes often exhibit long-term and complex deformation processes with multiple accelerating phases, which poses constant threats to the safe operations of hydropower stations, as well as the safety of the residents, houses, and infrastructures both upstream and downstream of the reservoirs. In this study, the quantile regression has been used to develop a fundamental tool for the prediction and early warning of this type of complex slope deformation. The application of this tool is illustrated in the case study of the Duonuo near-dam slope at Baishui River in China. Quantile regression can estimate the parameters of the prediction model, such as the Fukui–Okubo model used in this study, based on different quantile levels. This enables the predictive uncertainty to be quantified and obtain a possible failure-time horizon. Further, two indicators, i.e., the reliability indicator and the strength indicator, have been defined to aggregate the predictive information of the quantile regression. As such, the reliability and intensity of failure precursory signals associated with the accelerating behavior can be diagnosed. Finally, a probabilistic warning indicator has been proposed to establish an early warning procedure, which can measure the risk levels of a slope failure in real time. Two case studies, i.e., the Duonuo slope and the Vajont landslide, have been used to verify the effectiveness of the proposed early warning indicator. Thus, the tool developed in this study provides valuable references for predictive decision-making and disaster management of reservoir bank slopes. It can also easily be transferred to unstable slopes with similar evolution characteristics in other hazardous areas.HighlightsA new prediction approach using quantile regression and Fukui–Okubo model is proposed for reservoir bank slope failure.A failure time window is used to quantify predictive uncertainty in a reservoir bank slope failure prediction.Two indicators are developed for precursory diagnosis of reservoir bank slope failure.A dimensionless indicator for early warning of reservoir bank slope failure is proposed.

As a result of the dilation of soil matrix, dense submarine sand slopes can temporarily be steeper than the natural angle of repose. These slopes gradually fail by the detachment of individual grains and intermittent collapses of small coherent sand wedges. The key question is whether steep disturbances in a submarine slope grow in size (destabilizing breaching) or gradually diminish (stabilizing breaching) and thereby limit the overall slope failure and resulting damage. The ability to predict whether the breaching failure is stabilizing or destabilizing is also crucial for the assessment of safety of submarine infrastructure and hydraulic structures located along rivers, lakes, and coasts. Through a set of large-scale laboratory experiments, we investigate the validity of an existing criterion to determine the failure mode of breaching (i.e., stabilizing or destabilizing). Both modes were observed in these experiments, providing a unique set of data for analysis. It is concluded that the existing method has limited forecasting power. This was quantified using the mean absolute percentage error, which was found to be 92%. The reasons behind this large discrepancy are discussed. Given the complexity of the underlying geotechnical and hydraulic processes, more advanced methodologies are required.

To reduce the significant losses caused by slope failures and landslides, it is of great significance to detect and predict these disasters scientifically. This study focused on Huangdao District of Qingdao City in Shandong Province, using the improved Faster R-CNN network to detect slope failures and landslides. This study introduced a multi-scale feature enhancement module into the Faster R-CNN model. The module enhances the network’s perception of different scales of slope failures and landslides by deeply fusing high-resolution weak semantic features with low-resolution strong semantic features. Our experiments show that the improved Faster R-CNN model outperformed the traditional version, and that ResNet50 performed better than VGG16 with an AP value of 90.68%, F1 value of 0.94, recall value of 90.68%, and precision value of 98.17%. While the targets predicted by VGG16 were more dispersed and the false detection rate was higher than that of ResNet50, VGG16 was shown to have an advantage in predicting small-scale slope failures and landslides. The trained Faster R-CNN network model detected geological hazards of slope failure and landslide in Huangdao District, missing only two landslides, thereby demonstrating high detection accuracy. This method can provide an effective technical means for slope failures and landslides target detection and has practical implications.

The essential issues solved by geoenvironmental engineers relate to the assurance of uncontaminated regions of the subsurface just as the remediation of locales of the subsurface that have been sullied by releasing waste materials, spilling over the ground and underground stockpiling tanks and penetration of pesticides. In city areas, garbage and waste materials are generally dumped into landfills. A landfill site, which is otherwise called a trash dump, is used for the disposal of waste materials by burial. A safe landfill is a deliberately built sorrow in the ground into which wastes are put. The principal objective is to stay away from any water driven association between the wastes and the surrounding environment especially groundwater. This paper discusses landfill, in terms of its construction, stability and failure. The analysis and modelling of the landfill failure occurred in different countries like Poland, Turkey, Israel, the Philippines, China and Sri Lanka which are discussed.

A real-scale slope failure model experiment is performed to analyze the movement behavior of the slope during failure, and the results are analyzed through the x–MR control chart method, along with inverse displacement and various analysis sections such as K-values. As a result, the portent of failure can be identified to be about 7.7–18.3 min prior to the final slope failure. As a result of the analyses of changes in the control limit in the various analyses sections, it is considered that the application of K = 3 to the x-MR control chart is effective. It is observed that using the x-MR control chart technique of the inverse displacement is useful for the early prediction of the anomalous behavior of a slope, through a more quick and objective judgment. Henceforth, it is necessary to establish clear techniques for prediction and analyses of slope failure through continuous research, and those results can be used as the basic data of a slope instrumentation management standard that can contribute to the mitigation of life and property damage caused by slope failure hazards.

Hillslopes are important elements of mountain landscapes, but there is still limited understanding of how hillslopes respond to river incision and rock mass properties at the landscape scale. Topographic characteristics at Qingyang Mountain (QYM) on the tectonically active northeastern Tibetan Plateau, which we documented using field observations and geometric measurements of high-resolution DEMs, are the result of differences in river incision over timescales of 100,000 years or more. Hillslope erosion at QYM is achieved by slope failures that increase hillslope angles as rivers incise. Based on the Culmann's method, we consider the slope relief of 221–231 m to be limiting values corresponding to the observed threshold slope angle of ~ 26.3° in eastern QYM. Multi-scale analysis of lidar point clouds, obtained by laser scanner, and Structure from Motion photogrammetry reveal a spatial variation of bedrock fracture density that is consistent with lateral evolution of ridge-valley topography. Areas of higher fracture density correspond to eroded gullies, and areas of lower fracture density are found in ridges separating these gullies. Our results suggest that difference in tectonic fracturing of the rock mass dominantly drives lateral erosion of slopes in the study area.

During the highway construction along the Yangtze River in Anhui, China from 2015 to 2018, regional slope failures occurred frequently near the routes and constituted significant hazards to infrastructures. Especially from June to September in 2016 and 2017, the high-temperature weather and intensive rainfall hit this region, triggering a lot of slope failures. These slope failures have two puzzling features: (1) low height (2.5–5 m) or gentle dip angles (8–25°). Such height and dips are unlikely to fail in theory; (2) slope failure emerged immediately during rainfall, while the slope materials consist of clay soil with extremely low permeability. Field investigations, laboratory tests, and a large-scale slope model test were conducted to investigate the failure modes and mechanism of the slope failures. The results show (1) low steep slopes generally show failure modes of surface erosion, or repeated local failures around the slope shoulder, while the gentle slopes often display failure modes of overall failure or even landslides; (2) the slope material mainly contains clay mineral of illite and displays strong shrinkage ability, which is prone to forming desiccation cracks during drying evaporation. Desiccation cracks can significantly improve the infiltration capacity of soils with three or four orders of magnitude. Shear strength of the soil is sensitive to water and decreases sharply with the increased water content; (3) the large-scale slope model test confirms that desiccation cracks can induce slope failure by providing preferential flow pathways for rainwater to rapidly infiltrate into deep soils. Based on the above results, the difference of failure modes and scales between the steep slope and gentle slope is interpreted. It is inferred that desiccation cracks are difficult to develop stably and constantly on the inclined surface of steep slopes due to the intense surface runoff. Thus, surface erosion and shallow flow-slip dominate the failure modes of the low steep slopes. Conversely, a gentle slope surface is favorable for the development of desiccation cracks. Hence, overall slope instability or a landslide is more likely to occur in a gentle slope after long periods of drying-wetting cycles.

Rock slope failures pose significant challenges in geotechnical engineering due to the intricate nature of rock masses, discontinuities, and various destabilizing factors during and after excavation. In mining industries, such as national cement factories, multi-benched excavation systems are commonly used for quarrying. However, cut slopes are often designed with steep angles to maximize economic benefits, inadvertently neglecting critical slope stability issues. This oversight can lead to slope instability, endangering human lives and property. This study focuses on analyzing the stability of existing quarry cut slopes, estimating their final depth, and conducting a parametric study of geometric profiles including bench height, width, face angle, and rump width. Kinematic analysis helps identify potential failure modes. The results reveal that the existing quarry cut slope is prone to toppling, wedge failure, and planar failure with probabilities of 42.68%, 19.53%, and 14.23%, respectively. Numerical modeling using the finite element method (Phase2 8.0 software) was performed under both static and dynamic loading conditions. The shear reduction factor (SRF) of the existing quarry cut slope was 1.01 under static loading and 0.86 under dynamic loading. Similarly, for the estimated depth, the SRF was 0.82 under static loading and 0.7 under dynamic loading. These values indicate that the slope stability falls significantly below the minimum acceptable SRF, rendering it unstable. The parametric study highlights the face angle of the bench as the most influential parameter in slope stability. By adjusting the bench face angle from 90° to 75°, 70°, and 65°, the SRF increased by 31.6%, 35.4%, and 37.9%, respectively. Among these, a 70° bench face angle is recommended for optimal stability with a SRF of 1.27 under static loading and 1.18 under dynamic loading.

The topic of rainfall thresholds for landslide occurrence was thoroughly investigated, producing abundance of case studies at different scales of analysis and several technical and scientific advances. We reviewed the most recent papers published in scientific journals, highlighting significant advances and critical issues. We collected and grouped all the information on rainfall thresholds into four categories: publication details, geographical distribution and uses, dataset features, threshold definition. In each category, we selected descriptive information to characterize each one of the 115 rainfall threshold published in the last 9 years. The main improvements that stood out from the review are the definition of standard procedures for the identification of rainfall events and for the objective definition of the thresholds. Numerous advances were achieved in the cataloguing of landslides too, which can be defined as one of the most important variables, together with rainfall data, for drawing reliable thresholds. Another focal point of the reviewed articles was the increased definition of thresholds with different exceedance probabilities to be employed for the definition of warning levels in landslide early warning systems. Nevertheless, drawbacks and criticisms can be identified in most part of the recent literature on rainfall thresholds. The main issues concern the validation process, which is seldom carried out, and the very frequent lack of explanations for the rain gauge selection procedure. The paper may be used as a guide to find adequate literature on the most used or the most advanced approaches followed in every step of the procedure for defining reliable rainfall thresholds. Therefore, it constitutes a guideline for future studies and applications, in particular in early warning systems. The paper also aims at addressing the gaps that need to be filled to further enhance the quality of the research products in this field. The contribution of this manuscript could be seen not only as a review of the state of the art, but also an effective method to disseminate the best practices among scientists and stakeholders involved in landslide hazard management.