ENGINEERING GEOLOGICAL AND GEOTECHNICAL CHARACTERISTICS OF LANDSLIDE IN GORNJI HRGOVI, MUNICIPALITY OF SREBRENIK

Natural disasters during May 2014 caused a flood of water outside the unregulated bed of the river Tinja in the local area of Gornji Hrgovi. The flood effect affected the undermining and destruction of the foot part of the slope, reactivation and regressive development of the landslide, which was manifested by further secondary "breaking" of the sliding body towards the hypsometrically top part of the slope and intersection of the primary water pipeline. Gravitational displacement of the colluvial material resulted in significant degradation of the agricultural land surface in the central part of the unstable slope, while in the accumulation zone the accumulated slide mass destroyed the earth road communication. Based on the conducted geotechnical researches, determined engineering-geological and hydrogeological composition and properties of the terrain, the zoning of the terrain according to the degree of stability was performed, important recommendations and conditions of the landslide remediation method were presented.

Characterization of an Unstable Slope Using Geophysical, UAV, and Geological Techniques: Karakoram Himalaya, Northern Pakistan

Given active tectonism, rough terrain, and climate, the mountainous ranges in northern Pakistan are prone to geohazards, including earthquakes, unstable slopes, and landslides. The frequent landsliding in the region poses a risk to communities, economic activities, and transportation networks. In this context, the unstable slope above Mayun village calls for a multi-method approach for better assessment of the slope for planning interventions aimed at hazard mitigation. We conducted an integrated study including uncrewed aerial vehicle (UAV) and ground-penetrating radar (GPR) in coordination with geomorphic field observations to image the possible slip surfaces for a comprehensive understanding of a potential future rockslide with significant socioeconomic consequences. UAV-derived results helped delineate the overall extent of the unstable slope and its downslope area in a quick, remote, and safe way. GPR profiles have enabled the reconstruction of the bedrock’s morphology and its internal structure and the depth distribution of cracks running through the overburden and bedrock. The results provided insight into the stable and unstable compartments of the slope due to the thin cover of surficial deposits, high impedance contrast at the overburden-bedrock interface, lateral heterogeneities, and presence of open cracks, and almost detached blocks, respectively. These data on the dynamic properties of a landslide-prone slope could be used for the correct planning of civil infrastructure to minimize the potential risk of building damage in the seismically active Hunza valley.

A Case Study of a Large Unstable Mass Stabilization: “El Portalet” Pass at the Central Spanish Pyrenees

This case study presents the engineering approach conducted for stabilizing a landslide that occurred at “El Portalet” Pass in the Central Spanish Pyrenees activated due to the construction of a parking lot. Unlike common slope stabilization cases, measures projected here were aimed at slowing and controlling the landslide, and not completely stopping the movement. This decision was taken due to the slow movement of the landslide and the large unstable mass involved. The degree of success of the stabilization measures was assessed by stability analyses and data obtained from different geotechnical investigations and satellite survey techniques such as GB-SAR and DinSAR conducted by different authors in the area under study. The water table was found to be a critical factor in the landslide’s stability, and the tendency of the unstable slope for null movement (total stability) was related to the water table lowering process, which needs more than 10 years to occur due to regional and climatic issues. Results showed a good performance of the stabilization measures to control the landslide, demonstrating the effectiveness of the approach followed, and which became an example of a good response to the classical engineering duality cost–safety.

Study on Stability of Exit Slope of Chenjiapo Tunnel Under Condition of Long-term Rainfall

The exit slope of Chenjiapo Tunnel is located directly above the exit of Chenjiapo Tunnel on Enshi to Laifeng expressway. During the excavation of the exit of the right line of the tunnel, the left side of the front edge of the slope slips. Under the joint action of excavation and rainfall, a large landslide of 6.27×10 4 m 3 and a huge unstable slope of 8.69×10 5 m 3 are formed. The landslide body and unstable slope body not only cause the tunnel to be shut down, but also directly threaten the operation safety of the later expressway. Therefore, in order to study the stability change process of the exit slope of Chenjiapo tunnel under the condition of long-term rainfall, the finite element calculation of the slope is carried out by GeoStudio software. The results show that under the condition of long-term continuous rainfall, the safety factor of the slope decreases with the increased rainfall time, but the reduction rate gradually slows down, and finally tends to be stable. The safety factor of the slope is reduced from 1.187 in the natural state to 1.015, which indicates that the slope is still in a stable state under the condition of long-term continuous rainfall, but the safety reserve is not high, and it is easy to lose stability and damage due to the influence of external adverse factors. As the rainfall continues, the seepage line inside the slope is rising, and the saturated area of the soil at the toe of the slope is increasing. Until the slope begins to drain outwards, the seepage field inside the slope is basically stable. The maximum horizontal displacement of the slope increases with the increased rainfall time, but the increase rate gradually slows down until it tends to be stable. The maximum horizontal displacement of the slope occurred in the middle surface of the slope at the beginning of the rainfall, and gradually transferred to the toe of the slope within 7 days of the rainfall and continued until the end of the rainfall. At the end of the rainfall, the maximum horizontal displacement of the toe of the slope is 0.128 m, and the toe of the slope will be damaged first. At the beginning of the rainfall, the plastic zone of the slope is only scattered at the slope surface and the slope toe. And then as the rainfall continues, the distribution range of the plastic zone in the slope surface, the slope toe and the slide zone gradually widen, and the slope stability gradually decreases. The maximum horizontal displacement and plastic zone of the slope are concentrated at the toe of the slope, the slope presents obvious traction failure characteristics. According to the results of field survey, there are small-scale gravel soil collapses and shear outlets at the front edge of the slope, and the survey results are consistent with the simulation results. It is suggested to set up perfect drainage engineering in the middle and back of the slope, and set anti slide piles and drainage holes at the toe of the slope to reinforce the slope.

Application of the high-resolution digital elevation model in an integrated numerical method for the occurrence mechanism and post-failure behavior of the landslide

<p>In 2009, a large-scale landslide was triggered by typhoon rainfall and buried an entire village, which named Hsiaolin and located in Taiwan. <br>After that, Soil and Water Conservation Bureau (SWCB) has promoted a national project for the prevention work of large-scale landslide. The national project includes with the investigation of potential area, the design of monitoring system, and the design of warning system, etc. <br>The investigation of potential large-sclae landslide was based on the  digital elevation model with 1 meter resolution. However, the investigation of the underground was lack and not clear enough. Therefore, the specific landslide's body is hardly to estimate and it causes difficulty in follow-up works. <br>This study applied two methods to investigate the scenario of slope failure. The first method is based on the limited equilibrium method, which proposed by Yoshino and Uchida (2019). The method was used to search the specific region of unstable slope based on a series of high-resolution digital elevation models. After the specific region of unstable slope was confirmed, the landslide can be simulated by a numerical model, which this study proposed to represent the entire landslide process from occurrence to post-failure . <br>These proposed methods were applied at Baolai area, south Taiwan to track the evolution of the potential area. The failure scenario could be evaluated by the proposed numerical model. By this study, the investigation of underground can be evaluated and these results are very important information for the design of monitoring system.</p>

The Parker Quarry Lagerstätte of Vermont—The first reported Burgess Shale–type fauna rediscovered

Soft-bodied fossils of Cambrian age, now known as Burgess Shale–type biotas, were first described from the Parker Slate of the northwest Vermont (USA) slate belt in the late 19th century, 25 years before the discovery of the Burgess Shale in British Columbia, Canada. Here, we report the rediscovery of fossiliferous horizons at Parker’s Cobble, the site of the original quarry, which was thought to have been exhausted by excavation. New discoveries include a radiodont, multiple specimens of a new bivalved arthropod, a priapulid, and other undescribed forms. Pervasive soft-sediment deformation suggests accumulation near the toe of a steep unstable slope, similar to the setting of the Burgess Shale. Although fossils are rare, the exceptional preservation of some soft-bodied taxa suggests that recovered diversity was limited by transport into an inhospitable benthic setting rather than by decay, and this implies a potential for future discoveries of new taxa.