Naveen James

Seismic microzonation of a nuclear power plant site with detailed geotechnical, geophysical and site effect studies

This paper highlights the seismic microzonation carried out for a nuclear power plant site. Nuclear power plants are considered to be one of the most important and critical structures designed to withstand all natural disasters. Seismic microzonation is a process of demarcating a region into individual areas having different levels of various seismic hazards. This will help in identifying regions having high seismic hazard which is vital for engineering design and land-use planning. The main objective of this paper is to carry out the seismic microzonation of a nuclear power plant site situated in the east coast of South India, based on the spatial distribution of the hazard index value. The hazard index represents the consolidated effect of all major earthquake hazards and hazard influencing parameters. The present work will provide new directions for assessing the seismic hazards of new power plant sites in the country. Major seismic hazards considered for the evaluation of the hazard index are (1) intensity of ground shaking at bedrock, (2) site amplification, (3) liquefaction potential and (4) the predominant frequency of the earthquake motion at the surface. The intensity of ground shaking in terms of peak horizontal acceleration (PHA) was estimated for the study area using both deterministic and probabilistic approaches with logic tree methodology. The site characterization of the study area has been carried out using the multichannel analysis of surface waves test and available borehole data. One-dimensional ground response analysis was carried out at major locations within the study area for evaluating PHA and spectral accelerations at the ground surface. Based on the standard penetration test data, deterministic as well as probabilistic liquefaction hazard analysis has been carried out for the entire study area. Finally, all the major earthquake hazards estimated above, and other significant parameters representing local geology were integrated using the analytic hierarchy process and hazard index map for the study area was prepared. Maps showing the spatial variation of seismic hazards (intensity of ground shaking, liquefaction potential and predominant frequency) and hazard index are presented in this work.

Seismic Zonations at Micro and Macro-Level for Regions in the Peninsular India

Due to the lack of proper preparedness in the country against natural disasters, even an earthquake of moderate magnitude can cause extensive damage. This necessitates seismic zonation. Seismic zonation is a process in which a large region is demarcated into small zones based on the levels of earthquake hazards. Seismic zonation is generally carried out at micro-level, meso-level and macro-level. Presently, there are only a few guidelines available regarding the use of a particular level of zonation for a given study area. The present study checks the suitability of various levels of seismic zonation for different regions and reviews the feasibility of various methodologies for site characterization and site effect estimation. Further the seismic zonation was carried out both at the micro (for the Kalpakkam) and macro-level (for Karnataka state) using the appropriate methodologies. Based on this, recommendations have been made regarding the suitability of various methodologies as well as the grid size to be adopted for different level of zonation based on actual studies. KEywoRdS Macro-Level, Micro-Level, Peninsular India, Seismic Hazard, Seismic Zonation, Site Effects

Macro-Level Assessment of Seismically Induced Landslide Hazard for the State of Sikkim, India Based On GIS Technique

This paper presents a macro-level seismic landslide hazard assessment for the entire state of Sikkim, India, based on the Newmarks methodology. The slope map of Sikkim was derived from ASTER Global Digital Elevation Model (GDEM). Seismic shaking in terms of peak horizontal acceleration (PHA) at bedrock level was estimated from deterministic seismic hazard analysis (DSHA), considering point source model. Peak horizontal acceleration at the surface level for the study area was estimated based on nonlinear site amplification technique, considering B-type NEHRP site class. The PHA at surface was considered to induce driving forces on slopes, thus causing landslides. Knowing the surface level PHA and slope angle, the seismic landslide hazard assessment for each grid point was carried out using Newmarks analysis. The critical static factor of safety required to resist landslide for the PHA (obtained from deterministic analysis) was evaluated and its spatial variation throughout the study area is presented. For any slope in the study area, if the in-situ (available) static factor of safety is greater than the static factor of safety required to resist landslide as predicted in the present study, that slope is considered to be safe.

Experimental Studies on Physical Properties and Strength Response of Construction and Demolition Wastes

There is increasing inclination towards the reuse of construction and demolition wastes (CDWs), primarily containing building derived materials (BDM) in engineering practices such as ground improvement. Currently BDMs are used in the form of recycled aggregates that incur extra cost due to refinements. The present study, thereby, emphasizes on the use of virgin BDM. No previous studies related to its characterization and utilization in ground improvement have been reported till now. Hence, this study focuses on the characterization of BDM and its durability aspects through physical, chemical, and microscopic studies to test their compatibility when used in conjunction with local soil contaminated with aggressive chemicals. Soil composition varies based on the vicinity of a chemical plant, waste processing plant, or a coastal area. Results from this study can be used to encourage the practical use of BDM especially in chemically contaminated soil and developing relevant standard codes.

Earthquake and Seismicity

This chapter presents the physics of earthquakes and earthquake mechanism. Theory of plate tectonics and elastic rebound theory are explained along with global seismicity. The seismicity of India and surroundings is discussed in detail highlighting spatially varied tectonic framework of the country. A guideline for preparation of seismotectonic map is also provided in the chapter. Measurement of earthquake size in terms of intensity and magnitude are discussed with popular scales employed worldwide. Different seismic source models such as linear, point, areal and gridded seismicity models are discussed. Seismicity analysis to estimate seismicity parameters for a region or seismic source zone is also presented.

Local Site Effects for Seismic Zonation

This chapter predominantly discuss about the role of Local site conditions on the amplification of seismic waves and the resulted earthquake disasters. In-depth discussions are made on the various local site conditions which influence the ground shaking. Different available methods for the assessing the local site conditions are presented in this chapter. Various codal provisions for site classifications are also discussed here. This chapter also presents the assessment of local site effect at micro and macro-level using the appropriate methodologies.

Seismic Hazard Analysis

This chapter highlights the significance of Ground Motion Prediction Equations to estimate the seismic hazard at a region based on earthquake magnitude and source to site distance. A glimpse of both deterministic and probabilistic approaches for hazard assessment is presented along with a discussion on the logic tree framework. This chapter also discuss seismic hazard case studies for India as reported by various researchers.

Seismic Site Characterization

This chapter describes different methodologies available for site characterization. The details of different low strain and high strain tests are also listed in this chapter. It also provides procedures for the evaluation of dynamic properties from the laboratory as well as in-situ tests. Further, this chapter also presents site characterization studies carried out at micro as well as macro-level.

Principles and Practices of Seismic Zonation

This chapter describes about the principles of seismic zonations in detail. Chapter 7 presents the integration of various earthquake hazards to hazard index number, both at micro and macro-level. This chapter also provides a detailed guideline for carrying out seismic zonation of region at different levels.

Recent Advances in Soil Dynamics Relevant to Geotechnical Earthquake Engineering

Evidences from past earthquakes clearly show that the damages due to an earthquake and its severity at a site are controlled mainly by three factors, i.e., earthquake source and path characteristics, local geological and geotechnical characteristics, and structural design and quality of the construction. Seismic ground response at a site is strongly influenced by local geological and geotechnical conditions. The exact information of the geological, geomorphological, and geotechnical data along with seismotectonic details at a particular site are necessary to evaluate the ground response. The geometry of the subsoil structure, the soil type, the lateral discontinuities, and the surface topography will also influence the site response at a particular location. Since the seismic effects on the structure depend fully on the site conditions, research in the area of soil dynamics becomes more useful. The first input required in evaluation of geotechnical aspect of seismic hazard is the rock-level peak horizontal acceleration (PHA) values. The surface-level acceleration values need to be calculated based on the site conditions and site amplification values. This chapter discusses the recent advances in soil dynamics, especially in the area of geotechnical earthquake engineering. The topics covered in this chapter include various methods for evaluating the local site effects, dynamic soil properties, different field and laboratory tests required, various site classification schemes, and different methods to evaluate the surface-level ground motion. In addition to this, the aspects which need to be considered in liquefaction potential evaluation are also discussed.