Shilpa Pal

Study of effect of seismic displacements on landslide susceptibility zonation (LSZ) in Garhwal Himalayan region of India using GIS and remote sensing techniques

Landslides are the most damaging and threatening aftereffect of seismic events in Garhwal Himalayas. It is evident from past seismic events in Uttarakhand, India that no other phenomena can produce landslides of so great in size and number as a single seismic event can produce. Landslide inventories are produced for the study area before and after the occurrence of Chamoli Earthquake using Panchromatic (PAN) sharpened Linear Imaging Self Scanning-III (LISS-III) images. A sudden increase in number of landslides after the earthquake is observed. Further, two Landslide Susceptibility Zonation (LSZ) maps have been derived using pre- and post-Chamoli Earthquake landslide inventories. The difference of two LSZ indicates that landslides are very complex phenomenon and are affected by static factors in seismic conditions also. An attempt has been made to estimate the seismic displacements using Differential Synthetic Aperture Radar Interferometry (DIn SAR). European Remote Sensing Satellite-1/2 (ERS-1/ 2) SAR images have been used for preparing differential interferogram. Geometric and temporal decorrelation in SAR images is very high in the study area, which limits the use of DInSAR for displacement estimation. Theoretical displacement has been estimated using fault displacement modeling parameters for Chamoli earthquake. Post-Chamoli earthquake landslide inventory is overlaid over displacement map for understanding the impact of seismic displacement pattern with other static factors on the occurrence of landslides. It is observed that distribution and size of landslides is affected by displacement pattern controlled by other static factors also.

Inclusion of earthquake strong ground motion in a geographic information system-based landslide susceptibility zonation in Garhwal Himalayas

Garhwal Himalayas are seismically very active and simultaneously suffering from landslide hazards. Landslides are one of the most frequent natural hazards in Himalayas causing damages worth more than one billion US

An Overview of Recent Developments in Landslide Vulnerability Assessment-Presentation of a New Conceptual Framework

and around 200 deaths every year. Thus, it is of paramount importance to identify the landslide causative factors to study them carefully and rank them as per their influence on the occurrence of landslides. The difference image of GIS-derived landslide susceptibility zonation maps prepared for pre- and post-Chamoli earthquake shows the effect of seismic shaking on the occurrence of landslides in the Garhwal Himalaya. An attempt has been made to incorporate seismic shaking parameters in terms of peak ground acceleration with other static landslide causative factors to produce landslide susceptibility zonation map in geographic information system environment. In this paper, probabilistic seismic hazard analysis has been carried out to calculate peak ground acceleration values at different time periods for estimating seismic shaking conditions in the study area. Further, these values are used as one of the causative factors of landslides in the study area and it is observed that it refines the preparation of landslide susceptibility zonation map in seismically active areas like Garhwal Himalayas.

Empirical-based seismically induced slope displacements in a geographic information system environment: a case study

Open image in new window Landslides are one of the most destructive natural disasters, responsible for significant loss of life and livestock as well as damage to critical infrastructure, agricultural lands, housing and assets in mountainous regions. Despite all the recent technical progress towards landslide forecasting and mitigation, human activities are still affected by landslide disasters. Hence, assessment of landslide risk and vulnerability becomes an important aspect in all landslide studies. Vulnerability is a fundamental component in the evaluation of risk, and its estimation is essential in making a reasonable prediction of the landslide consequences. Most of the approaches applied for carrying out landslide risk assessment have inherent limitations. In most countries, there are no standard parameters and hence landslide risk assessment is still in its developing stage. The assessment of risk of communities prone to landslide is a topic that is gaining importance. In the field of landslide research, most of the studies have been focused on the landslide hazards maps. But, only a few studies have discussed on the risk and vulnerability aspects. This paper summarizes previous research on risk and vulnerability assessment and also discusses different methods suitable for estimating vulnerability of various elements to landslides. In addition, it proposes a conceptual framework for the assessment of landslide hazard and vulnerability, and mapping procedures for risk assessment.

Seismic Analysis of Multistoried Building with Optimized Damper Properties

Landslides are one of the most damaging and threatening hazards associated with seismically induced slope movements. Estimations of support conditions for slope displacements are important for taking preventive measures to avoid landslide events in future. Californias Division of Mines and Geology (DMG) procedure is utilised in the present paper for estimating the slope failure mechanism under seismic conditions. In this study, the DMG procedure has been explained and has also been incorporated in a Geographic Information System (GIS) using Arc-GIS software from Environmental Systems Research Institute. Further, it is utilised for establishing a seismically induced slope displacement map for the Skien municipality area of Telemark County in Norway. The motivation for selecting this site was the availability of geotechnical parameters for the site. Three different displacement maps have been produced for earthquake scenarios of magnitude 5, 6 and 7, respectively. The maximum displacement of 133 cm is estimated for earthquake scenario of magnitude 7. It is noticed that the sensitive areas for slope failure remain the same under different earthquake scenarios. A displacement tool based on the DMG procedure has been created in the Arc-tool box in Arc-GIS software. This tool minimises the efforts for inserting formulas for making raster displacement maps. By using the displacement tool one can generate final products like displacement maps automatically at high accuracy and in quick time. The prepared slope displacement maps of study area are used for landslide susceptibility zonation (LSZ) map preparation. The LSZ maps are useful for landslide hazard assessment and further can be utilised by planners, civil engineers and local administrators for town planning and policy-making.

Site-Specific Vulnerability Assessment of Buildings Exposed to Rockfalls

In today’s scenario where space is an issue, the increase in population has led to a boom in the construction industry. With the lack of land for construction, the buildings are becoming higher and more complex, so with the increase in the number of stories, it is necessary to make them safe under adverse seismic conditions. Dampers are one way to make the structure earthquake resistant and the optimization of their properties is sometimes required. In this study, the damper properties, i.e., damping and stiffness have been optimized using self-organizing migrating genetic algorithm (SOMGA) and genetic algorithm (GA) technique on a model of 10-storey building which has equal mass, stiffness, etc. on all the floors. The optimized damper properties obtained from SOMGA result in the reduction of 52% of the storey displacement while that of GA is 60% as compared to the undamped model. Both techniques provide better optimized damper properties. It is observed that the optimized damper helps in significant reduction of the seismic response of the structure, thus justifying the need of optimized parameters of dampers.

A modified approach for semi-quantitative estimation of physical vulnerability of buildings exposed to different landslide intensity scenarios

A landslide is one of the most common hazards occurring in mountainous region in response to a number of natural and anthropogenic processes. In particular, South Asian nation including India is the worst hit by landslides. Thus the vulnerability assessment towards landslides becomes an important aspect, as it pose risk to human life, environment, buildings, and infrastructures. From the perspective of natural and engineering sciences, vulnerability is defined as the degree of loss, or damage to a set of element at risk within the affected area due to landslides. It acts as a primary component in the evaluation of landslide risk, and its accurate estimation is necessary in making a reasonable prediction of the landslide consequences. The present paper aims to produce a framework for assessing the physical vulnerability of building exposed to rockfall using the empirical formula proposed by Li et al. (Landslides 7(2):125–134, 2010 [3]) in terms of resistance offered by building and the intensity of rockfall. The proposed methodology permits to obtain an estimate of vulnerability of buildings when hit by three different intensities (low, medium and high) of rockfall. Finally, application of this proposed framework is illustrated through a case study from Chamoli district, Uttarakhand (India).

Hybrid SOMA: A Tool for Optimizing TMD Parameters

ABSTRACT Landslides are the most common natural disasters in mountainous regions, being responsible for significant loss of life as well as damage to critical infrastructure and properties. As the world population grows, people tend to move to higher locations to construct buildings, thereby making structures vulnerable due to landslides. This paper discusses previous research on the vulnerability assessment of structures exposed to landslides and presents a modified semi-quantitative approach to assess the scenario-based physical vulnerability of buildings based on their resistance ability and landslide intensity. Resistance ability is determined by integrating expert knowledge-based resistance factors assigned to five primary building parameters. Landslide intensity matrix defining different intensity levels is proposed based on combinations of landslide velocity and volume. Physical vulnerability of buildings is estimated and classified as class I, II or III for scenario-based low to very high landslide intensity. Finally, the application of the model is illustrated with a case study of 71 buildings from Garhwal Himalayas, India.

Cost Optimization of 2-Way Ribbed Slab Using Hybrid Self Organizing Migrating Algorithm

Tuned Mass Damper are widely used in the engineering community for reduction in response of the structure during the hazardous earthquake excitations or for other uses such as vibration control in slender and tall buildings. But it is not necessary that the TMD used is reducing the response of the structure effectively for the parameters set for it during the application. So for the TMD to work at its best, the optimal parameters have to be found. The work discusses the optimum parameters of Tuned Mass Damper for seismically excited structures. The Hybrid Self Organizing Migrating Genetic Algorithm (SOMGA) and Self Organizing Migrating algorithm with Quadratic Interpolation (SOMAQI) are used to find the Optimum values of TMD parameters. All parameters of TMD are searched in order to find the best results. TMD parameters are checked under different excitations and the present approach is also compared with other published results.

Shear Seam in Dam Foundation System

In this paper, an optimization problem of 2-way ribbed slab or waffle square slab has been solved using a hybrid variant of self organizing migrating algorithm, C-SOMAQI. The main objective of this problem is to design a 2-way ribbed waffled slab of dimension 10 m * 10 m with optimum cost of steel as well as concrete. The design variables of 2-way ribbed waffled slab are taken as the effective depth of the slab (j), ribs width (p), the spacing between ribs (b), effective depth of ribs (d), and the area of reinforcement. Various population based techniques are available in literature to solve optimization problems. In this paper, a low population based hybrid technique C-SOMAQI has been taken to solve this problem that provides the solution at an optimum cost. To validate the claim, this problem has also been solved theoretically and a comparative analysis between these two solutions has been made. The study concludes that C-SOMAQI provides better results as compare to theoretical method.