Application of Smoothed Particle Hydrodynamics (SPH) for the Simulation of Flow-like Landslides on 3D Terrains

Flow-type landslide is one type of landslide that generally exhibits characteristics of high flow velocities, long jump distances, and poor predictability. Simulation of it facilitates propagation analysis and provides solutions for risk assessment and mitigation design. The smoothed particle hydrodynamics (SPH) method has been successfully applied to the simulation of two-dimensional (2D) and three-dimensional (3D) flow-like landslides. However, the influence of boundary resistance on the whole process of landslide failure is rarely discussed. In this study, a boundary algorithm considering the friction is proposed, and integrated into the boundary condition of the SPH method, and its accuracy is verified. Moreover, the Navier-Stokes equation combined with the non-Newtonian fluid rheology model was utilized to solve the dynamic behavior of the flow-like landslide. To verify its performance, the Shuicheng landslide event, which occurred in Guizhou, China, was taken as a case study. In the 2D simulation, a sensitivity analysis was conducted, and the results showed that the shearing strength parameters have more influence on the computation accuracy in comparison with the coefficient of viscosity. Afterwards, the dynamic characteristics of the landslide, such as the velocity and the impact area, were analyzed in the 3D simulation. The simulation results are in good agreement with the field investigations. The simulation results demonstrate that the SPH method performs well in reproducing the landslide process, and facilitates the analysis of landslide characteristics as well as the affected areas, which provides a scientific basis for conducting the risk assessment and disaster mitigation design.

Towards a rapid assessment of highway slope disasters by using multidisciplinary techniques

Mega-earthquakes and extreme climate events accompanied by intrinsic fragile geology lead to numerous landslides along mountain highways in Taiwan, causing enormous life and economic losses. In this study, a system for rapid slope disaster information integration and assessment is proposed with the aim of providing information on landslide occurrence, failure mechanisms, and subsequent landslide-affected areas to the highway authority rapidly. The functionality of the proposed system is deployed into three units: (1) geohazard rapid report (GeoPORT I), (2) multidisciplinary geological survey report (GeoPORT II), and (3) site-specific landslide simulation report (GeoPORT III). After landslide occurrence, the seismology-based monitoring network rapidly provides the initial slope disaster information, including preliminary location, event magnitude, earthquake activity, and source dynamics, within an hour. Within 3 days of the landslide, a multidisciplinary geological survey is conducted to collect high-precision topographical, geological, and remote-sensing data to determine the possible failure mechanism. After integrating the aforementioned information, a full-scale three-dimensional landslide simulation based on the discrete element method is performed within 10 days to reveal the failure process and to identify the areas potentially affected by subsequent disasters through scenario modeling. Overall, the proposed system can promptly provide comprehensive and objective information to relevant authorities after the event occurrence for hazard assessment. The proposed system was validated using a landslide event in the Central Cross-Island Highway of Taiwan.

Landslide Hazard Assessment and Runout Simulation by Utilizing Remote Sensing, Geophysical, and Geological Techniques

Landslide events in Karakorum ranges are frequent and have already damaged local infrastructures and roads. In the hilly regions, landslide characterization and predicting its deposition pattern are essential for accurate engineering hazard assessment. To this end, numerical simulation models are commonly used tools. However, appropriate model parameters are often not available to predict and generate real landslide scenarios. This work describes the use of multidisciplinary techniques to estimate the model parameters for a slope prone to landslide and simulate the hazard level. The first important parameter, landslide boundary, and dynamics were estimated from temporal satellite images by identifying the areas with prominent deformations using the Interferometric Synthetic Aperture Radar (InSAR) technique. The susceptible subsurface strata volume and the possible landslide initiation depth were determined with the electrical resistivity method. In addition, voxel 3D electrical resistivity models were created to present the depth of the existing rupture and the nature of subsurface strata. The soil mechanical parameters were calculated during field visits and laboratory tests. The parameters adopted from different techniques helped simulate the susceptible landslide volume and initiation depth. These parameters are a critical factor in developing an accurate high-speed landslide model through numerical simulation. The applied methodology is vital to understand the dynamics of a particular slope and perform accurate engineering hazard assessment with numerical simulation. The results are essential to predict the potential deposition areas of the landslide event accurately, minimize the risk level, and take proactive mitigation measures.

Geological Terrain Mapping using Geographic Information System (GIS) and Drone Photogrammetry

The research area was conducted within the Bukit Persekutuan, Kuala Lumpur, and it was located at the latitude 3° 8'32.93"N and longitude 101°40'32.80"E. The researcher carried out geological terrain mapping to evaluate the research area in accordance with the geological terrain classification attributes of each thematic map produced, namely, Terrain map, slope gradient map, erosion, and instability map, as well as construction suitability map. The occurrence of landslide events within the research area becomes a major contributing factor to thoroughly conducting an investigation by field mapping and analysing using the Geographic Information System (GIS) technology. The application of Geographic Information System (GIS) and drone photogrammetry images play an essential role to analyze and process the data, thus, generate the thematic maps. The research area indicates that about 79.11% of the overall area was not appreciable with erosion, 8.58% contribute to the erosion, 11.00% of recent general instability, and 2.97% represent a landslide event. The suitability for development mapping illustrated Class I (23.40), Class II (36.37%), Class III (26.39%), and Class IV (15.50%) where it can be referred to the construction suitability classification system, the suitability for development was high in class I, moderate in class II, low in class III and not suitable in class IV.

Remediating a Landslide Affected Well for Subsequent Abandonment - Challenges Overcome and Solutions Applied

Control/Tracking Number 21 ADIP-P-4946-SPE Abstract Description This paper will present a case study to describe the well integrity complications of an onshore gas well in Romania affected by a landslide event, the challenges overcome during the land consolidation/excavation around the well, and the remediation solution of the well's casings. After being severely affected by a landslide, the subject well stopped production having a surface deviation from the original position of 5m and a landslide plane at cca 25m. The primary scope of the project was to restore the integrity of the well in order to safely abandon the well so that people and environment were not exposed to risk or danger. The project was elaborated through a collaborative effort of multidisciplinary teams including company personnel, such as well integrity engineers, completion engineers, geologists, abandonment team members, civil engineers, HSSE and construction, as well as several service providers. As part of the Phase to consolidate the well's surrounding area, additional risk mitigations were identified through HAZID workshops and implemented, such as creating gas drainage shafts, utilizing ATEX equipment and cold cutting tools for casings, tools, and organizing Rescue People Services. These elements and more aspects were elements of safety included in the project to better assure the success. The project has several milestones, the first being the consolidation of the well surroundings using 33 cement pillar rings with a total diameter of 8m and depth of 32m. A gas relief column was necessary to ensure the gas infiltration was exhausted from the soil. Once the ring was formed around the well, the excavation commenced inside the ring, avoiding impact with the conductor pipe of the well. This activity posed notable HSSE challenges, requiring solutions derived from HAZID workshops based on evaluations of the various discipline teams and certified parties. Following the excavation, the planned casing remediation included cold cutting the casing using diamond encrusted equipment, due to the gas presence at the well area. Casing restoration was planned for use of bolts to reconnect the casings, thus preventing welding.

GIS-BASED LANDSLIDE VOLUME ESTIMATION USING DIGITAL TERRAIN MODELS DERIVED FROM LIDAR AND RADAR SYSTEMS: CASE OF PIDIGAN, ABRA

Southwest Monsoon (Habagat) and Typhoon Luis caused a deep-seated landslide that struck Sitio Kayang, Brgy. Immuli, Pidigan, Abra on August 15, 2018. Rainfall-induced deep-seated landslides displace partially at a time which necessitates the determination of remaining landslide volume along the slope. In this study, the potential landslide volume and mass transport were estimated using several remote sensing products, including SAR (Synthetic Aperture Radar) data and LiDAR-DTM (Light Detection and Ranging-Digital Terrain Model). The post-landslide DTM was generated using Sentinel-1 SAR data. The potential landslide volume and landslide failure surfaces were ascertained through the stability analysis using Scoops3D, while the mass transport volume was obtained from the pre- and post-landslide DTM. Results showed that the estimated total volume in all the landslide areas was 135,962 m3. Meanwhile, the remaining landslide volume (i.e., difference between potential volume from pre-landslide event and volume of transported mass) yielded illogical values due to the derived large mass transport values. This blunder may be attributed to the generalization of the transported volume (due to Sentinel-1 DTM coarse resolution), and decorrelation due to vegetation cover. Overall, the LiDAR-DTM data delivered a high-resolution estimation of the potential landslide volume and proved to be useful for landslide application studies. Future studies may incorporate field data (e.g., geotechnical parameters, groundwater, landslide actual measurements) for more accurate performance of stability analysis and may best to utilize LiDAR-DTM in post-landslide volume computation for a more reliable estimation of mass transport and potentially remaining landslide volume.

The February 2004 Landslide Event in Geomorphic Perspective

<p>In February 2004 a severe storm impacted the lower half of the North Island, New Zealand. Intense rainfall during the storm triggered extensive landsliding throughout the Tertiary hill country of Wanganui, Manawatu, and Wairarapa. The storm event also produced floods estimated to have a return period of 100 years. Flooding impacted on many communities, destroying homes, drowning livestock, and ruining crops. Because the effects of flooding were more immediate, and affected a greater number of people, landsliding damage received little coverage in the news media. However, the importance of these large rainfall-triggered, multiple landslide events that occur periodically in New Zealand should not be underestimated. New Zealand is losing valuable hillslope soil through erosion processes at a rate far in excess of the development of new soil. Landsliding is the most obvious and active hillslope erosion process operating in the hill country of New Zealand today. This study examines the impact of the February 2004 landslide event from a geomorphic perspective, addressing questions such as: what changes to landforms were produced by this event, and, how much geomorphic work (volume of material, moved a given distance in a given time) was done by landsliding during the event. The proposition underlying this study is that it is not just the magnitude of the triggering event that determines the geomorphic response in terms of landform change and work done, but also that the nature of the terrain influences the magnitude (e.g. landslide densities, volumes, areal extent) of the landsliding produced. In order to test this hypothesis the study was undertaken in two parts. The first, a catchment-based study using mostly field methods to produce a sediment budget and landform change measurement. Secondly, a regional analysis of four areas which experienced the most severe landslide damage were analysed in terms of terrain and landslide characteristics. From the methodologies employed in these studies it is demonstrated that terrain characteristics are highly influential in determining the type and severity of landsliding. To determine the geomorphic significance of the event in terms of the history of similar New Zealand landslide events, a frequency-magnitude analysis comparison was conducted, and the results compared with studies of previous rainfall-triggered, multiple landslide events. The results of the catchment-based study, the regional study, and the frequencymagnitude analysis show that the February 2004 event is likely to be the most geomorphically significant event of its type (rainfall-triggered) to have occurred in New Zealand over the past 100 years. The area affected (16,000 [square kilometer]) and number of landslides produced (~70,000) are greater than previously documented events. Landslide densities are also amongst the highest recorded in New Zealand. Although the majority of landslides were shallow regolith failures, large scars from deep-seated, rotational landslides will be visible in the landscape for hundreds of years. Material eroded from hillslopes during the event is estimated (conservatively) to be in excess of 20 million tonnes. While the majority of this eroded material remains within the hillslope system (depositional slopes and fans), a considerable proportion (an average of 25 % in the study catchment) is transferred to fluvial systems via fluvial coupling and removed from hillslopes permanently.</p>

The February 2004 Landslide Event in Geomorphic Perspective

<p>In February 2004 a severe storm impacted the lower half of the North Island, New Zealand. Intense rainfall during the storm triggered extensive landsliding throughout the Tertiary hill country of Wanganui, Manawatu, and Wairarapa. The storm event also produced floods estimated to have a return period of 100 years. Flooding impacted on many communities, destroying homes, drowning livestock, and ruining crops. Because the effects of flooding were more immediate, and affected a greater number of people, landsliding damage received little coverage in the news media. However, the importance of these large rainfall-triggered, multiple landslide events that occur periodically in New Zealand should not be underestimated. New Zealand is losing valuable hillslope soil through erosion processes at a rate far in excess of the development of new soil. Landsliding is the most obvious and active hillslope erosion process operating in the hill country of New Zealand today. This study examines the impact of the February 2004 landslide event from a geomorphic perspective, addressing questions such as: what changes to landforms were produced by this event, and, how much geomorphic work (volume of material, moved a given distance in a given time) was done by landsliding during the event. The proposition underlying this study is that it is not just the magnitude of the triggering event that determines the geomorphic response in terms of landform change and work done, but also that the nature of the terrain influences the magnitude (e.g. landslide densities, volumes, areal extent) of the landsliding produced. In order to test this hypothesis the study was undertaken in two parts. The first, a catchment-based study using mostly field methods to produce a sediment budget and landform change measurement. Secondly, a regional analysis of four areas which experienced the most severe landslide damage were analysed in terms of terrain and landslide characteristics. From the methodologies employed in these studies it is demonstrated that terrain characteristics are highly influential in determining the type and severity of landsliding. To determine the geomorphic significance of the event in terms of the history of similar New Zealand landslide events, a frequency-magnitude analysis comparison was conducted, and the results compared with studies of previous rainfall-triggered, multiple landslide events. The results of the catchment-based study, the regional study, and the frequencymagnitude analysis show that the February 2004 event is likely to be the most geomorphically significant event of its type (rainfall-triggered) to have occurred in New Zealand over the past 100 years. The area affected (16,000 [square kilometer]) and number of landslides produced (~70,000) are greater than previously documented events. Landslide densities are also amongst the highest recorded in New Zealand. Although the majority of landslides were shallow regolith failures, large scars from deep-seated, rotational landslides will be visible in the landscape for hundreds of years. Material eroded from hillslopes during the event is estimated (conservatively) to be in excess of 20 million tonnes. While the majority of this eroded material remains within the hillslope system (depositional slopes and fans), a considerable proportion (an average of 25 % in the study catchment) is transferred to fluvial systems via fluvial coupling and removed from hillslopes permanently.</p>

Persistent Scatterer Interferometry for Pettimudi (India) Landslide Monitoring using Sentinel-1A Images

The continuous monitoring of land surface movement over time is of paramount importance for assessing landslide triggering factors and mitigating landslide hazards. This research focuses on measuring horizontal and vertical surface displacement due to a devastating landslide event in the west-facing slope of the Rajamala Hills, induced by intense rainfall. The landslide occurred in Pettimudi, a tea-plantation village of the Idukki district in Kerala, India, on August 6–7, 2020. The persistent-scatterer synthetic aperture radar interferometry (PSInSAR ) technique, along with the Stanford Method for Persistent Scatterers (StaMPS), was applied to investigate the land surface movement over time. A stack of 20 Sentinel-1A single-look complex images (19 interferograms) acquired in descending passes was used for PSInSAR processing. The line-of-sight (LOS ) displacement in long time series, and hence the average LOS velocity, was measured at each measurement-point location. The mean LOS velocity was decomposed into horizontal east–west (EW ) and vertical up–down velocity components. The results show that the mean LOS, EW, and up–down velocities in the study area, respectively, range from –18.76 to +11.88, –10.95 to +6.93, and –15.05 to +9.53 mm/y, and the LOS displacement ranges from –19.60 to +19.59 mm. The displacement values clearly indicate the instability of the terrain. The time-series LOS displacement trends derived from the applied PSInSAR technique are very useful for providing valuable inputs for disaster management and the development of disaster early-warning systems for the benefit of local residents.