Initial data from monitoring of a landslide process affecting Emine Cape, Bulgaria

In October 2019, a 3D extensometer was installed to monitor slow landslide movements, affecting the slope of Cape Emine north of the lighthouse. For almost 2 years of observations, a tendency of shrinkage of the zone as a result of lateral pressure from the southern landslide was established. The movements are divided into two stages: the first – until December 2020, and the second – after that date. In the months from April to June the movements in direction X are more intensive due to the rainy situation at this time of the year.

Effect of the anchors' free length that made of tubular screw rods on the forces distribution in pile-anchor retaining structures on highways

Pile-supported retaining structures are widely used to protect road sections from landslide processes. The article describes the design and calculation peculiarities of pile-supported retaining structures reinforced with a drill and inject anchors from tubular screw rods. The authors considered two options for this type of anchors setup: without free length and with a pre-set free length. In the software geotechnical complex Plaxis, on the finite element method basis, mathematical modeling and calculation of a pile-supported anchor retaining structure with different free anchors lengths from tubular screw rods for various soils types have been performed. Numerical relationships have been obtained between the anchors' free length and the resulting forces in the retaining structure. The performed calculations series of the test scheme showed that with an increase in the free anchors' length in the retaining structure, there is a decrease in the applied load in its load-bearing elements due to the horizontal displacements growth. The article presents the survey results of a real road section, on which a landslide displacement is being prepared, and considers a design solution for a pile-supported anchor retaining structure to ensure its safe operation. Performed a series of calculations for various landslide process development stages in this area showed that the effect of the anchors' free length also largely depends on the state of the adjacent soil mass. Obtained results clearly show that the design of a free length section for anchors made of tubular screw rods makes it possible to design more cost-effective pile-supported anchor holding structures without reducing their reliability.

Landslide Process Revealed by Mineralogical Properties of Landslide Deposits in the Sa Pa District, Vietnam

Hau Thao Village is located in Sa Pa Prefecture, in northern Vietnam. The village contains one of the most picturesque landscapes with terraced paddy fields located in landslide topography formed on a gentle slope. However, the creation of the topography has not been sufficiently clarified. In this study, samples of soil and stone are taken from two landslide areas in Hau Thao Village for mineral composition analysis, clarifying that the sauce rock of the deposits comprising the landslide areas is made up of granitoids, forming the upper slope above the fault located in the hinterland. The landslides occurring in Hau Thao Village are caused by the remobilization of the secondary deposits transported from the upper part of the slope by debris flow.

New insights into the delayed initiation of a debris flow in southwest China

On 6 July 2020, 3 h 40 min after rainfall stopped, a delayed debris-flow disaster occurred due to colluvium deposits in a hollow region (CDH) in the Chenghuangmiao gully, Sichuan Province, China, which resulted in 4 deaths and 27 injuries. This study explores the initiation process of the delayed debris flow and the cause for the delay. Field investigations, catchment geometry interpretation, laboratory tests, theoretical calculations, and fluid-solid coupling numerical simulation were performed to obtain landslide parameters and understand the mechanisms of the event. Results show: (1) The event was a giant low-frequency viscous debris flow. (2) Its initiation was caused by the delayed landslide process under the influence of back-end confluence. (3) The debris-flow discharge in the main gully increased over 19.5 min. (4) The seepage process inside the CDH continued for 3 h 20 min after the rainfall stopped before its pore pressure and reduction in strength was sufficient to initiate the debris flow. This research provides new insights on delayed debris-flow disasters; it is a reference for improving disaster management systems, especially monitoring and early warning systems, thereby avoiding future casualties.

JUSTIFICATION OF STRENGTHENING A SLIDING BRIDGE SUPPORT (ON THE EXAMPLE OF THE BRIDGE THROUGH THE R. IZHORA ON THE HIGH-SPEED ROAD SAINT PETERSBURG - MOSCOW)

The article describes the experience of strengthening the foundations of the bridge support laying on a landslide slope. The bridge under consideration crosses the river Izhora in the Leningrad region. Numerical modeling of the process of development of support deformations is carried out. Analysis of the calculations showed that the development of the landslide process occurred as a result of waterlogging of the soil massif and soaking of soils at the base of support No. 10. Structural strengthening of the support in the form of buttresses was developed and numerically substantiated to eliminate deformation of the bridge support.

The role of unpaved roads in the formation of landslide processes (on the example of Voronezh region)

The article gives a brief description of the Voronezh region, provides data on the cause of landslides in its territory. The cyclical nature of landslide processes is noted, which in the region is on average 6-8 years. Attention is focused on anthropogenic activity, leading to the occurrence of creeping layers of the earth. The main causes of erosion processes are: significant plowing of the area (80%), which is not subject to the rules of anti-erosion agrotechnology; the irrational use of pastures and hayfields; an extensive gully-beam network. The role of temporary reservoirs formed in the ruts of unpaved roads, passing along the slopes and ravines, as a source of overmoistening of the soil layers and initiation of landslide processes is considered. The analysis of the landslide distribution over the territory of the Voronezh region and their dependence on the network of dirt roads is given. The areas of the Voronezh region were ranked by the number of landslide processes associated with the impact of a number of unpaved highways. Of the 32 districts of the region, according to this ranking, 12 are extremely dangerous, very dangerous and dangerous, and the same areas have a very extensive network of unpaved roads running near ravines, steep banks of rivers and ponds, where potentially flow of landslide processes. Dirt roads often have relatively deep ruts where melted or rainwater accumulates, forming local micro-ponds. Flowing to the waterproof layer, water saturates the soil layer, which can slide down the slope, forming a landslide process. It is necessary to predict the possibility of the occurrence of dangerous natural phenomena when laying automobile dirt roads.

Distinct Element Simulation of a Landslide Process

The paper presents a numerical simulation of the development of a catastrophic landslide in a sandstone quarry and methods of reconstructing the quarry to its previous condition from before the landslide. The important objective of the paper is to present the capabilities of the numerical method used in the analysis of the landslide process, namely the Distinct Element Method (DEM). This method is poorly known, though it is capable of solving important geotechnical problems in which massive displacements are modelled. The features of the method are presented on the basis of a case study. Therefore a numerical analysis is carried out to show the performance of DEM in generating a displacement of several dozen meters in the example of a catastrophic landslide that occurred some years ago in a sandstone quarry. This engineering problem makes it possible to describe and analyse the mechanisms, causes and consequences of the landslide.