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Development of Hybrid Computational Approaches for Landslide Susceptibility Mapping Using Remotely Sensed Data in East Sikkim, India
Published in Himansu Das, Jitendra Kumar Rout, Suresh Chandra Moharana, Nilanjan Dey, Applied Intelligent Decision Making in Machine Learning, 2020
Indrajit Chowdhuri, Paramita Roy, Rabin Chakrabortty, Subodh Chandra Pal, Biswajit Das, Sadhan Malik
East Sikkim is one of the four administrative districts in Sikkim India. It is located in the south-eastern portion of the state. And this district is divided into the three sub-divisions of Gangtok, Pakyong, and Rongli. The researched area covered 94 sq. km following the longitudinal and latitudinal extensions 88°27′ to 88°56′ E and 27°9′ to 27°25′ N respectively (Figure 4.1). Accordingly to the Indian Meteorological Department (IMD) East Sikkim belongs to the subtropical humid and temperate climate zone. As in the district of Sikkim, Teesta is the major river, and other major drainage systems are the Rangpo, Chhu, and Dik Chhu. The average rainfall is 3894 mm which mainly occurs during the period of May to September. Temperature varies in summer from 15°C to 20°C and in winter from 4°C to 10°C. Forest is the main land cover in this district and about 72.66 sq. km is its total area. Four types of forest coverage zones are found: mixed coniferous broad leaved forest, alpine coniferous, shrubs, and alpine meadow. Geomorphology consists of hilly, slope, and valley formations. The major soils are mountain meadow, brown red, yellow, and laterite. Predominant geological formations are recent alluvium Reyang, Gorubathan in the Daling group, migmatitic gneisses, augean gneiss, amphibolites in Darjeeling, and the Kanchenjunga group. This hilly area is mainly formed by gneiss, green schist, and amphibolites; they are all metamorphosed. The lineament of geological formation trends toward five directions: N–S, E–W, NE–SW, ENE–WSW, and NW–SE. Phylite, amphibolites, and schist were formed in the Precambrian era and alluvium along the river valley is from the Quaternary era.
Suction and infiltration measurement on cut slope in highly heterogeneous residual soil
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
T.H. Low, H.A. Faisal, M. Saravanan
Construction activities in hilly terrain residual soil frequently confront geotechnical engineers with slope instability problems. Failures in both natural and cut slopes of Peninsular Malaysia are usually brought about by rainfall during the monsoon season. The upper layer of residual soil profile is always partially saturated, and has a relatively higher permeability to infiltrating rainwater. This causes the pore water regime to be governed largely by rainfall pattern.
REDUCING SILT BY IMPLEMENTING ISO 14000 FOR HILLY PROJECTS
Published in C.V.J. Varma, B.S.K. Naidu, A.R.G. Rao, Silting Problems in Hydro Power Plants, 2020
A proper geological and geotechnical survey is vital before launching any developmental and construction project in the hills including the preparation of landslide hazard zone maps, so that prior knowledge about the status of the area to be undertaken for development is available. China with 60% mountainous area has taken a lead in studying and taking steps to prevent and rehabilitate landslides through the Institute of Mountain Hazards and Environment at Chengdu, since 1965.
Discontinuous rock slope stability analysis by limit equilibrium approaches – a review
Published in International Journal of Digital Earth, 2021
Mohammad Azarafza, Haluk Akgün, Akbar Ghazifard, Ebrahim Asghari-Kaljahi, Jafar Rahnamarad, Reza Derakhshani
Slope stability (earth or rock) is one of the most important issues in the geotechnical engineering field with a background of more than 300 years since the construction and development projects have always been faced with side-hill instabilities in different scales which were classified as slopes or landslides (Frasheri 2006). Generally, various approaches used for slope stability assessment can be classified as simple evaluations, planar failures, limit state criteria for limit equilibrium analysis, numerical methods, hybrid, and high-order approaches (Kliche 2018). In the meantime, limit equilibrium approaches due to their simplicity, rapid implementation; closed-form analysis, continuous access, easy assumptions, and providing multiple answers (e.g. F.S and probable sliding surface), the capability of being coupled or re-activated with other procedures are considered as the most flexible methodologies. Development of novel or hybrid procedures (rebuilt based on traditional progress) is conducted to achieve more accurate stability results, to cover more uncertainties, reduce the errors and establish generalized procedures for instability assessments as the main goal during the last decades. Application of the LEMs for stability analyses in the last recent 300 years indicate that these approaches are highly flexible to be integrated with high-level programming which is capable to cover more geomechanical features and geometrical properties. This advantage helps to reduce the uncertainties in the slope mass by considering the deterministic formulations.
Hydro-geomorphic assessment of erosion intensity and sediment yield initiated debris-flow hazards at Wadi Dahab Watershed, Egypt
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2021
Sara M. Abuzied, Biswajeet Pradhan
This study also suggests that irregular and heavy rainfalls in this arid region can cause slow sheet erosion on low slopes and rapid gully erosion on steep slopes, which have Precambrian basement rocks. The rate of soil erosion in Wadi Dahab is serious because of scarce vegetation, structural setting, randomly unpaved roads, rugged topography, thin soil horizon, and landslide occurrences. The results define the priority zones where different soil conservation actions should be applied by decision-makers. Our study recommends some important actions to reduce the sensitivity of erosion such as (1) Designing and adopting some strategies for land use planning and slope management to control surface erosion and runoff velocity; (2) decreasing the slope length and slope steepness by building of contour walls, bench terraces, check dams in gullies to break the slope; (3) maintaining roads, highways, and other infrastructure in hilly lands to avoid soil erosion; (4) constructing retentive walls after cutting hillslopes for any infrastructure building.
Seismic vulnerability assessment of earthquake-prone mega-city Shillong, India using geophysical mapping and remote sensing
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2020
Saurabh Baruah, Goutam Kashyap Boruah, Sangeeta Sharma, Washim Akram Hoque, Timangshu Chetia, Chandan Dey, Devakrishna Gogoi, Papu Kumar Das, Santanu Baruah, Dipak Basumatari, Jayanta Pathak, Anurup Gohain Barua, Sailendra Choudhury
Components of seismic risk assessment estimation are: (1) hazard analysis based upon local site effects (microzonation) and other components; and (2) utilisation of exposure information (structural inventory) for vulnerability analysis (Coburn and Spence 1992; CSSC 1999; Chandler and Lam 2001; Bendimerad 2001; Agrawal and Chourasia 2007; Yu, Chouinard, and Rosset 2016). Based on the above components, this study carries the site-specific vulnerability assessment in Shillong city. An additional factor contributing to the vulnerability of construction on slopes arises from the irregular configuration of “hill buildings” due to foundations located at different levels. The observed irregular configurations typically depict low structural ductility resulting in an increased vulnerability (Singh, Umrao, and Singh 2014). Although previous studies (Biswas et al. 2013) have been made towards the seismic hazard assessment pertinent to the Shillong city, no attempt on seismic vulnerability assessment has been made so far.