Landslides

Earthquake-induced plane failure is typically generated on bedding rock slopes. This failure mode has been widely observed in the past earthquakes in Western China (e.g., Wenchuan earthquake). Among them, the multi-slip plane failure may occur with the presence of multiple bedding planes or internal discontinuities within the slopes. This study developed an extended Newmark sliding block model to investigate the multi-slip seismic displacements of the bedding rock slopes. The unified formulation is presented for seismic sliding analysis of bedding rock slopes with arbitrary numbers and inclinations of bedding planes. Both horizontal and vertical earthquake ground motions and the possible amplifications that may result from site and topographic effects are considered. The developed model is validated by the results from shaking table test. The multi-slip mechanism and the effects of dip angle of bedding planes and vertical ground motion are investigated. The results show that (1) the multi-slip failure evolution is different to that identified from the traditional method, indicating the significant interactions among the seismic sliding behavior associated with bedding planes. (2) The influence of the vertical component of ground motion on the multi-sliding displacement is within a range of 20%. (3) The dip angle of sliding planes has a large effect on the sliding displacement, even if the yield coefficient remains the same. Finally, the proposed method is used to evaluate the seismic displacement and performance of the Liujiawan landslide that was triggered in Wenchuan earthquake.

This paper presents recent innovations implemented in the LaRiMiT (Landslide Risk Mitigation Toolbox) webtool. These include an innovative methodology for utilising experts’ scoring of landslide risk mitigation measures directly within the decision support tool, and updating of the tool’s database over structural measures to include many nature-based solutions (NBS) for mitigating landslide risk. Landslides are a common and treacherous natural hazard, and due to the effect of climate change on the frequency and intensity of extreme weather events, climate-driven landslides are expected to become more frequent. This negative trend is a driving factor for developing decision-support solutions for risk mitigation, and the LaRiMiT toolbox and the expert scoring methodology presented in this article contribute to meeting these needs. Selecting suitable structural measures is complicated due to factors such as site-specific conditions, local knowledge and resources, socio-economic constraints, and environmental considerations. LaRiMiT uses user-input attributes of site-specific slope movements combined with expert scoring of the suitability of various mitigation solutions to identify and select appropriate mitigation measures from an extensive database of structural solutions. While the LaRiMiT database initially included only conventional (grey) solutions relying on traditional methods, it has been recently expanded to include nature-based solutions (NBS), which are sustainable techniques for managing erosion and mitigating shallow landslides using vegetation and the use of natural materials. NBS and conventional solutions can also be combined to provide hybrid solutions. The proposed methodology for implementing expert scoring is dynamic and iterative, consisting of statistical pooling of experts’ scores collected via online surveys, and consolidating these into an expert scoring utility embedded in the LaRiMiT web portal engine. An initial application of this methodology has been tested by surveying a set of landslides experts, mostly in Europe, and applying it to the structural measures database in the LaRiMiT tool. Although the number of experts in this initial application is limited, dynamic updating of the scoring allows the tool to continuously improve as additional experts contribute.

The combination of dense urban development, hilly terrain, and intense seasonal rainfall has caused acute landslide problems in Hong Kong, which are manifested by a death toll of over 470 people since the late 1940s. Tackling landslide problems in an urban setting, in particular under the effect of climate change, calls for a development and implementation of a holistic risk management strategy. It entails the use of engineering and non-engineering approaches, involving policy, legislative, administrative, innovation, technical, educational, community-based, and emergency-preparedness provisions. In this paper, these two approaches are showcased by the slope safety system that has been developed and promulgated in managing landslide risk for building Hong Kong as a world-class smart city.

On June 28, 2010, a catastrophic rock avalanche occurred after an extreme rainstorm at Guanling with N 25°59′10′′ in latitude and E 105°16′50′′ in longitude, Guizhou, China. This rock avalanche has a long run-out distance of 1.5 km, with 1.75 million cubic meters of debris instantly burying two villages and resulting in 99 deaths. It originated in the coal measure strata, with the upper part of limestone and dolomite, the middle part of the sandstone with gentle inclination, and the lower part of shale and mudstone, together locally with coals. This kind of unique structure, with hard resistant caprock overlying softer ductile rocks, coupled with the central outflow region at the contact zone, has catastrophic potential for rock avalanches and creates challenges for engineering geological/hydrogeological analysis. The topography showed that the hillside slopes were steeper at the upper portion but gentler in the lower portion, looked like the shape of a “boot.” The upper steep landform easily led to slope instability due to its high static shear stresses, and the wide middle and lower parts provided kinematic conditions for long run-out. Transformation of the larger potential energy into kinetic energy contributed to the formation of a rapid long run-out rock avalanche. The rainfall from June 27 to 28 was the apparent trigger of this catastrophic avalanche. The measured rainfall of more than 310 mm within 24 h exceeded the local historical records that were recorded over the last 60 years. The pore pressure on discontinuities of sandstone had an effect on the slope stability. The valley runoff supplied a saturated base for the long run-out debris, inducing an additional increase of the terminus distance and the increased velocity of the avalanche movement.

Bài báo này trình bày một nghiên cứu trường hợp về sự rút lui của vách đá và sự phát triển tiến triển của các lớp talus trong khu vực sạt lở đá Hungtsaiping ở Đài Loan. Phân tích địa hình và mô hình hóa vật lý đã xác định các loại hình liên quan đến sự rút lui của vách đá, bao gồm sự rút lui theo hàng song song thành dòng thẳng của sườn dốc chuyển đổi thành sự rút lui theo hàng song song thành dòng thẳng trung tâm. Mô hình rút lui của vách đá và sự lắng đọng của talus tại Hungtsaiping có thể được phân loại như sau: (1) rút lui đồng thời với độ dốc steeper; (2) rút lui đồng thời với độ dốc nhẹ; (3) rút lui thành dòng thẳng trung tâm với độ dốc steeper; (4) rút lui thành dòng thẳng trung tâm với độ dốc nhẹ; (5) rút lui thành dòng thẳng song song với độ dốc steeper; và (6) rút lui thành dòng thẳng song song với độ dốc nhẹ. Bài báo này xác định các yếu tố kiểm soát cơ bản liên quan đến sự rút lui của vách đá và đề xuất một kịch bản có thể để giải thích sự rút lui của vách đá và sự phát triển tiến triển của các lớp talus trong khu vực Hungtsaiping từ năm 1904 đến 2006.

Flexible barriers have been widely adopted to mitigate the debris flow disasters. However, the research on the coupled interaction analysis between flexible barriers and debris flows with boulders in front is rarely reported. In this paper, a two-stage coupled modeling technique which can account for the debris mobility, the non-linear behavior of a flexible barrier, and the dynamic interaction between flexible barriers and debris flows is developed firstly based on the Arbitrary Lagrangian-Eulerian (ALE) method using LS-DYNA. The proposed coupling model is verified by a large-scale field test, comparing the flow velocity and flow depth of the debris flow, as well as the internal force and deformation of the flexible barrier. Further, the proposed numerical model is adopted to study the performance of flexible barrier impacted by debris flow with boulders in front. Two practical cases that the debris flow contains a single boulder with a diameter of 2 m and 1 m in front, respectively, are investigated. The impact positions are both the bottom center of the middle functional module of the barrier. The numerical results show that the barrier cannot intercept the debris flow with a boulder of 2 m in diameter. When the flexible barrier is subjected to three 1 m boulders in front of the debris flow, plastic hinges are formed at impact positions of the steel posts. It is recommended that additional protection measurements are required to maintain the structural integrity.

This paper deals with groundwater hydrology at a prominent fracture zone landslide slope (Nuta–Yone landslides) in Japan with an objective to explore an efficient method for the application of landslide stability enhancement measures. The correlation analyses between the hydrological parameters and ground surface movement data at this landslide resulted in low correlation values indicating that the geological formation of the area is extremely complex. For the purpose of understanding the groundwater flow behavior in the landslide area, a three-dimensional transient groundwater flow model was prepared for a part of the landslide slope, where the levels of effectiveness of applied landslide stability enhancement measures (in the form of multilayered deep horizontal drains) are different, and was calibrated against the measured water surface elevations at different piezometer locations. The parameter distributions in the calibrated model and the general directions of the groundwater flow in terms of flow vectors and the results of particle tracking at the model site were interpreted to understand the reasons for variations in effectiveness of existing landslide stability enhancement measures and to find potentially better locations for the implementation of future landslide stability enhancement measures. From the modeling results, it was also understood that groundwater flow model can be effectively used in better planning and locating the landslide stability enhancement measures.

Landslides which occur at unexpected locations and times, and which have unrecognizable risk areas, often cause mass casualties. Despite there being few preceding landslides in the same season, the catastrophic Qijiaba landslide occurred in the new government-selected settlement of Wufu village, Sichuan Province, China, on September 5, 2021, killing three people and destroying 13 houses. In this paper, the landslide features and causes are discussed based on field investigations, remote sensing interpretations, and laboratory-based soil experiments. The results showed that it was a typical soil landslide within a geomorphic hollow of the slope with a volume of 20,230 m3, recurrence interval of at least 69 years, and runout distance of 137.5 m. This type of landslide is difficult to predict. The soil strength in the sliding surface decreased suddenly as the water content increased, and the soil’s rich clay mineral and high clay particle contents determined its high mobility (Heim’s ratio of 0.44). The occurrence time of the Qijiaba landslide lagged 1.3 days behind the peak rainfall, and the 2-day cumulative rainfall was a crucial factor in the landslide occurrence. Finally, the large water confluence area behind the main scarp was determined to be 3.9 times the area of the landslide itself, thereby providing abundant water conditions to induce failure. The factors underlying the casualties included inappropriate site selection, insufficient awareness of potential landslides, and failure to evacuate in time. The results of this study provide a basis for future prevention, mitigation, and early warning of similar landslides.

Landslide inventories are extremely important. They are vital for hazard analyses. This article presents an inventory of landslides in Mexico from 1935 to 2017. Although landslide monitoring studies exist in specific areas of the country, so far, no historical catalog has been published that provides a basis for spatial-temporal analysis and determining impact in terms of the loss of human lives. The reported events were categorized as the following types of displacements: fall, landslide, and complex movement and flow; data were standardized and stored using SPSS software. In addition, estimates were produced to ascertain the number of people who may have been affected by landslides in 2019 based on their relationship with marginalization levels at the national level, as elaborated by the National Population Council (CONAPO). Marginalization degrees represent the exclusion of a population from development through socioeconomic inequalities that manifest themselves as low income and the lack of education, health, infrastructure, and access to basic services. It was found that localities with high and very high marginalization levels account for almost half of the landslides over 82 years. This study reveals new findings in terms of the spatial distribution of events and the affected populations that are considered a valuable contribution to the study of landslides in Mexico.