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Papers by P Anbazhagan

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Mar 1, 2023

Indian Geotechnical Journal

The maximum possible earthquake magnitude ( ) calculation is indispensable in many seismic/engine... more The maximum possible earthquake magnitude ( ) calculation is indispensable in many seismic/engineering applications. It is obligatory for earthquake engineering community, disaster management agencies and the insurance industry. However, there is no universally accepted practice for estimating the value of (Kijko and Singh, 2011).The maximum magnitude is dened as the upper limit of earthquake magnitude for a given region and is synonymous with the magnitude of the largest credible. It assumes a sharp cutoff magnitude at , so that, by denition, no earthquakes are to be expected with magnitude exceeding . Presently, deterministic and probabilistic based approaches are being used for estimation. These approaches are based on the frequency magnitude distribution, seismicity data and maximum observed magnitude ( ) of seismic study area (SSA) which have lots of uncertainty. These approaches are suitable for the regions having long seismicity data and high seismicity rate. Furthermore, t...

$Research paper thumbnail of Characterization of Rail Track Subsurface Using Seismic Refraction Survey$

Contemporary Topics on Testing, Modeling, and Case Studies of Geomaterials, Pavements, and Tunnels, 2011

Pure and Applied Geophysics, 2009

In this paper an attempt has been made to evaluate the spatial variability of the depth of weathe... more In this paper an attempt has been made to evaluate the spatial variability of the depth of weathered and engineering bedrock in Bangalore, south India using Multichannel Analysis of Surface Wave (MASW) survey. One-dimensional MASW survey has been carried out at 58 locations and shear-wave velocities are measured. Using velocity profiles, the depth of weathered rock and engineering rock surface levels has been determined. Based on the literature, shear-wave velocity of 330 ± 30 m/s for weathered rock or soft rock and 760 ± 60 m/s for engineering rock or hard rock has been considered. Depths corresponding to these velocity ranges are evaluated with respect to ground contour levels and top surface levels have been mapped with an interpolation technique using natural neighborhood. The depth of weathered rock varies from 1 m to about 21 m. In 58 testing locations, only 42 locations reached the depths which have a shear-wave velocity of more than 760 ± 60 m/s. The depth of engineering rock is evaluated from these data and it varies from 1 m to about 50 m. Further, these rock depths have been compared with a subsurface profile obtained from a twodimensional (2-D) MASW survey at 20 locations and a few selected available bore logs from the deep geotechnical boreholes.

Natural Hazards and Earth System Science, 2009

In this work an attempt has been made to evaluate the seismic hazard of South India (8.0 • N-20 •... more In this work an attempt has been made to evaluate the seismic hazard of South India (8.0 • N-20 • N; 72 • E-88 • E) based on the probabilistic seismic hazard analysis (PSHA). The earthquake data obtained from different sources were declustered to remove the dependent events. A total of 598 earthquakes of moment magnitude 4 and above were obtained from the study area after declustering, and were considered for further hazard analysis. The seismotectonic map of the study area was prepared by considering the faults, lineaments and the shear zones in the study area which are associated with earthquakes of magnitude 4 and above. For assessing the seismic hazard, the study area was divided into small grids of size 0.1 • ×0.1 • , and the hazard parameters were calculated at the centre of each of these grid cells by considering all the seismic sources with in a radius of 300 km. Rock level peak horizontal acceleration (PHA) and spectral acceleration (SA) values at 1 s corresponding to 10% and 2% probability of exceedance in 50 years have been calculated for all the grid points. The contour maps showing the spatial variation of these values are presented here. Uniform hazard response spectrum (UHRS) at rock level for 5% damping and 10% and 2% probability of exceedance in 50 years were also developed for all the grid points. The peak ground acceleration (PGA) at surface level was calculated for the entire South India for four different site classes. These values can be used to find the PGA values at any site in South India based on site class at that location. Thus, this method can be viewed as a simplified method to evaluate the PGA values at any site in the study area.

Natural Hazards and Earth System Science, 2006

Deterministic Seismic Hazard Analysis (DSHA) for the Bangalore, India has been carried out by con... more Deterministic Seismic Hazard Analysis (DSHA) for the Bangalore, India has been carried out by considering the past earthquakes, assumed subsurface fault rupture lengths and point source synthetic ground motion model. The sources have been identified using satellite remote sensing images and seismotectonic atlas map of India and relevant field studies. Maximum Credible Earthquake (MCE) has been determined by considering the regional seismotectonic activity in about 350 km radius around Bangalore. The seismotectonic map has been prepared by considering the faults, lineaments, shear zones in the area and past moderate earthquakes of more than 470 events having the moment magnitude of 3.5 and above. In addition, 1300 number of earthquake tremors having moment magnitude of less than 3.5 has been considered for the study. Shortest distance from the Bangalore to the different sources is measured and then Peak Horizontal Acceleration (PHA) is calculated for the different sources and moment magnitude of events using regional attenuation relation for peninsular India. Based on Wells and Coppersmith (1994) relationship, subsurface fault rupture length of about 3.8% of total length of the fault shown to be matching with past earthquake events in the area. To simulate synthetic ground motions, Boore (1983, 2003) SMSIM programs have been used and the PHA for the different locations is evaluated. From the above approaches, the PHA of 0.15 g was established. This value was obtained for a maximum credible earthquake having a moment magnitude of 5.1 for a source Mandya-Channapatna-Bangalore lineament. This particular source has been identified as a vulnerable source for Bangalore. From this study, it is very clear that Bangalore area can be described as seismically moderately active region. It is also recommended that southern part of Karnataka in particular Bangalore, Mandya and Kolar, need to be upgraded from current Indian Seismic Zone II

Natural Hazards, 2009

This article presents the results of probabilistic seismic hazard analysis (PSHA) for Bangalore, ... more This article presents the results of probabilistic seismic hazard analysis (PSHA) for Bangalore, South India. Analyses have been carried out considering the seismotectonic parameters of the region covering a radius of 350 km keeping Bangalore as the center. Seismic hazard parameter 'b' has been evaluated considering the available earthquake data using (1) Gutenberg-Richter (G-R) relationship and (2) Kijko and Sellevoll (1989, 1992) method utilizing extreme and complete catalogs. The 'b' parameter was estimated to be 0.62 to 0.98 from G-R relation and 0.87 ± 0.03 from Kijko and Sellevoll method. The results obtained are a little higher than the 'b' values published earlier for southern India. Further, probabilistic seismic hazard analysis for Bangalore region has been carried out considering six seismogenic sources. From the analysis, mean annual rate of exceedance and cumulative probability hazard curve for peak ground acceleration (PGA) and spectral acceleration (Sa) have been generated. The quantified hazard values in terms of the rock level peak ground acceleration (PGA) are mapped for 10% probability of exceedance in 50 years on a grid size of 0.5 km 9 0.5 km. In addition, Uniform Hazard Response Spectrum (UHRS) at rock level is also developed for the 5% damping corresponding to 10% probability of exceedance in 50 years. The peak ground acceleration (PGA) value of 0.121 g obtained from the present investigation is slightly lower (but comparable) than the PGA values obtained from the deterministic seismic hazard analysis (DSHA) for the same area. However, the PGA value obtained in the current investigation is higher than PGA values reported in the global seismic hazard assessment program (GSHAP) maps of Bhatia et al. (1999) for the shield area.

Geotechnical Testing Journal, 2010

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright

Geotechnical and Geological Engineering, 2008

Geomechanics and Geoengineering, 2010

and-conditions-of-access.pdf This article may be used for research, teaching and private study pu... more and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

In the present study, acceleration design-response spectra (ADRS) for deep and shallow sites have... more In the present study, acceleration design-response spectra (ADRS) for deep and shallow sites have been proposed for different seismic site classification as per NEHRP. Nonlinear site response analysis has been performed at different subsurface profiles and surface spectra have been derived. The site factors in terms of short period or 0.2 s (Fa) and long period or 1.0 s (Fv) for both the regions has been estimated. Finally, using these site factors, ADRS for both the regions have been proposed. This is the first time such extensive study has been done for developing the ADRS for the deep and shallow sites of India or Asia for different seismic site class.

Journal of Testing and Evaluation, 2011

Geomechanics and Geoengineering, 2010

Natural Hazards and Earth System Science, 2009

Natural Hazards, 2011

The conventional Cornell’s source-based approach of probabilistic seismic-hazard assessment (PSHA... more The conventional Cornell’s source-based approach of probabilistic seismic-hazard assessment (PSHA) has been employed all around the world, whilst many studies often rely on the use of computer packages such as FRISK (McGuire FRISK—a computer program for seismic risk analysis. Open-File Report 78-1007, United States Geological Survey, Department of Interior, Washington 1978) and SEISRISK III (Bender and Perkins SEISRISK III—a computer program for seismic hazard estimation, Bulletin 1772. United States Geological Survey, Department of Interior, Washington 1987). A “black-box” syndrome may be resulted if the user of the software does not have another simple and robust PSHA method that can be used to make comparisons. An alternative method for PSHA, namely direct amplitude-based (DAB) approach, has been developed as a heuristic and efficient method enabling users to undertake their own sanity checks on outputs from computer packages. This paper experiments the application of the DAB app...

Geotechnical and Geological Engineering, 2008

Japanese Geotechnical Society Special Publication, 2015

This study proposes to develop a low cost damping scheme using soil and waste tyre crumb mixture ... more This study proposes to develop a low cost damping scheme using soil and waste tyre crumb mixture for low to moderate rise buildings. The proposed study consists of two parts, first characterizing soil and waste tyre mixtures and finding out the optimal size of tyre crumbs. The second part is to design the isolation system for low to moderate rise buildings and determine optimum dimension of the system. In the first part, a series of Unconsolidated Undrained triaxial test and large scale direct shear test have been carried out to select the optimum size of tyre crumbs from seven different crumb sizes. The Rubber Soil Mixtures (RSM) sample that provides higher shear strength, energy absorption capacity and stiffness is considered as the optimal size and further used in numerical simulations. In the second part, to analyze the damping effect of RSM, extensive numerical simulations have been carried out on the soil-foundation-structure system with varying thickness of RSM around isolated footing, varying percentage of rubber in RSM and input time history. The reduction in shaking level in terms of acceleration and inter storey drift, at different floor level with the use of RSM can be reduced by 40 to 50%.

Pure and Applied Geophysics

Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, Mar 1, 2023

Indian Geotechnical Journal

$Research paper thumbnail of Characterization of Rail Track Subsurface Using Seismic Refraction Survey$

Contemporary Topics on Testing, Modeling, and Case Studies of Geomaterials, Pavements, and Tunnels, 2011

Pure and Applied Geophysics, 2009

Natural Hazards and Earth System Science, 2009

Natural Hazards and Earth System Science, 2006

Natural Hazards, 2009

Geotechnical Testing Journal, 2010

Geotechnical and Geological Engineering, 2008

Geomechanics and Geoengineering, 2010

Journal of Testing and Evaluation, 2011

Geomechanics and Geoengineering, 2010

Natural Hazards and Earth System Science, 2009

Natural Hazards, 2011

Geotechnical and Geological Engineering, 2008

Japanese Geotechnical Society Special Publication, 2015

Pure and Applied Geophysics

Standard Penetration Test (SPT) N values and the energy correction factor play a crucial role in ... more Standard Penetration Test (SPT) N values and the energy correction factor play a crucial role in the soil liquefaction assessment. In the Liquefaction potential assessment, the cyclic resistance ratio is estimated considering soil strength measured through SPT N values. Due to various mechanical energy losses, energy measured just below anvil and above the sampler doesn't equal the theoretical energy, hence corrected SPT N values are used in the most of the codes. However Indian Standard Code does not specify any correction for hammer energy, various studies have shown that there is a need to upgrade the present version of IS 1893. In this study, an attempt has been made to measure, hammer energy first time in India uses indigenously developed SPT-Hammer Energy Measuring Apparatus (HEMA) by the Department of Civil Engineering, IISc, Bangalore at below the anvil and above the sampler tube. Then variations of energy values are used to understand the effect on the estimation of liquefaction potential in Indian cities.

Utilizing rubber tyres in vibration mitigation can be a viable approach of resolving the chronic ... more Utilizing rubber tyres in vibration mitigation can be a viable approach of resolving the chronic problems associated with disposal of waste tyres. However, the dynamic properties of sand-tyre crumb mixtures (STCM) are essential for the design of a vibration isolation system. In this study, the dynamic properties of STCM in terms of shear modulus and damping ratio are presented against the shear strain. The modulus and damping ratio of STCM for small to large shear strain were measured using Torsional resonant column tests and cyclic triaxial tests, for two composition of tyre crumbs (50% and 75%) and three different confining pressure (50, 100, and 200 kPa). The results showed that, shear modulus and the damping ratio of the mixtures are strongly influenced by the percentage of rubber inclusion. Shear modulus decreased with an increase in tyre crumb inclusion for all the confining pressure, whereas the damping ratio increases with the increase in rubber content in STCM. For any percentage of tyre crumbs inclusion, the shear modulus increases and damping ratio decrease with increasing confining pressure. These results are useful to understand the dynamic response of STCM and further used in model studies to design a low cost isolation system.

This paper presents forensic investigations of earthquake induced failures during Sikkim 2011 Ear... more This paper presents forensic investigations of earthquake induced failures during Sikkim 2011 Earthquake, India. Detailed field geotechnical observations and geophysical investigations have been carried out at selected locations affected by 2011 Sikkim earthquake. Field observation, drilling of boreholes with sample collection (DBS), surface wave testing by Multichannel Analysis of Surface Wave (MASW) method and Ground Penetrating Radar (GPR) survey have been carried out at sites having slope failures, settlement and structural failures. Three different failure cases: distressed pavement over a natural slope, a school building, and secretariat building failures are discussed with reference to the field tests carried out. GPR radargram showed the cracked portion of pavement and the depth of the cracks. DBS and MASW at school building show the presence of loose cohesionless soil layer below the top dense layer, which might have undergone cyclic mobility and hence resulted in a settlement and cracks in the floor slab. GPR investigation at Sikkim secretariat building showed that the building is constructed on a sloped ground, where one side is filled with soil (damaged side) and the other side is directly resting on the rock. The study highlights the possible reasons for local seismic wave amplification and the associated damage with the help of field investigation carried out.

Study of seismic hazard and site response are essential and has become mandatory for the design o... more Study of seismic hazard and site response are essential and has become mandatory for the design of important structures. Subsurface investigation is an important step, from where input parameters for site response studies like shear wave velocity (Vs), density, thickness and damping characteristics etc are obtained. Most of the site response studies at shallow bedrock site are usually carried out by using Standard penetration test (SPT) N values and Vs from Multichannel Analysis of Surface Waves (MASW) with assumption that soil layers are horizontal, uniform and homogeneous. These assumptions are not completely true in shallow bedrock region due to heterogeneous soil deposits. The objective of this study is to generate subsurface profiles at shallow bedrock region using integrated site investigation testing. In this study drilling of borehole with SPT N value measurement, seismic testing of MASW and Electrical Resistivity Tomography (ERT) has been carried out at selected locations in Hampi, Karnataka, India. SPT gives soil type and density, MASW gives shear wave velocity and resistivity testing gives layer thickness. Integrated subsurface profiles are generated and are used to understand variation of subsurface layers in shallow bedrock sites and validate 1-D site response study assumptions. These subsurface profiles may be further used to understand difference of 1-D and 2-D site response.

The objective of this paper is to estimate the maximum magnitude () which is defined as the upper... more The objective of this paper is to estimate the maximum magnitude () which is defined as the upper limit of earthquake magnitude for a given region by a new approach considering regional rupture characteristics. The proposed method has been explained in details and examined for an active seismic region. Seismic study area (SSA) has been generated by dividing into radii of 200 km and 500 km, based on the seismicity and seismotectonics. The regional rupture character has been established by considering Percentage Fault Rupture (PFR), which is the ratio of subsurface rupture length (RLD) to Total Fault Length (TFL) expressed in percentage. PFR is used for determining RLD, which is further used for estimating the maximum magnitude for each source. Maximum magnitude for SSA of Kanpur region has been estimated and compared with the values from existing methods. It is observed from the study that the existing deterministic and probabilistic estimation methods are sensitive to SSA radius, magnitude of completeness (, and parameters and values. However from the proposed method is a function of the rupture character and is irrespective of the SSA and , and parameters and values. KEYWORDS Maximum earthquake magnitude (), regional Rupture Characteristics, and G-R parameters, magnitude of completeness, maximum observed magnitude (). You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)

This study investigates the mechanical behavior of geosynthetic-reinforced composite materials, S... more This study investigates the mechanical behavior of geosynthetic-reinforced composite materials, Sand-Tyre Crumb Mixtures (STCM) by conducting Unconsolidated Undrained (UU) triaxial tests. The main objective of this study is to evaluate the stress-strain characteristics of STCM in geosynthetic-reinforced works. The mechanical behavior of geosynthetic-reinforced STCM has been investigated by varying proportions of tyre crumbs (50% and 75% tyre crumbs by volume), type of geosynthetic (geotextile, geogrid and geonets), number of geosynthetic layers (1 to 4 layers) and confining pressure. A series of UU triaxial tests has been carried out to select the optimum size of tyre crumb. Tyre crumb that provides comparatively higher stiffness is considered as the optimal size and has been used in the investigation on geosynthetic-reinforced STCM. The results demonstrate that STCM reinforced by geotextile has enhanced peak strength, axial strain at failure, energy absorption and ductility capacity. Also, it has been found that the type of geosynthetic significantly influences the shear strength of STCM.

Liquefaction hazard is one of the major concerns for earthquake geotechnical engineering. In this... more Liquefaction hazard is one of the major concerns for earthquake geotechnical engineering. In this paper an attempt has been made to assess liquefaction potential of Chennai city using SPT N values. Chennai is located between 12.75° to 13.25° N and 80.0° to 80.5° E on the southeast coast of India and in the northeast corner of Tamil Nadu. To understand the liquefaction possibility of Chennai city, about 650 Borelogs have been collected from different geotechnical agencies and used for the analysis. These boreholes were drilled for different projects in Chennai, most of them were drilled up to hard stratum and a minimum depth of 10m. SPT borehole data contains information about depth of water table, the classification of soil and the field observed 'N' values, index properties, rock depth. These borehole information are used to prepare N corrected table by applying the universally followed correction factors for liquefaction study. These corrected N values are further used to estimate the factor of safety against liquefaction of soil layer. Based on the factor of safety, the regional liquefaction hazard maps have been developed for depths of 1.5m, 3.0m, 6.0m and 10.0m. To represent the worst scenario, least factor of safety has been identified for each borehole location and mapped. Further the estimated factor of safety against liquefaction is used to estimate liquefaction potential index by considering depth of layer. These results are analyzed and compared in this paper.

Ground penetrating radar (GPR) is a widely used non destructive testing method for the identifica... more Ground penetrating radar (GPR) is a widely used non destructive testing method for the identification of subsurface features in transportation geotechnical engineering. GPR is a geophysical technique to detect and identify structures, either natural or man-made, below the ground surface with the help of electromagnetic radiations. In this study an attempt has been made to extent possibility of using GPR for pavement structural evaluation. The structural assessment of existing road pavements are carried out using GPR antennas of 1.6 GHz and 500 MHz. A model test section was constructed using different layers of Sand, Red soil, Concrete block and steel pipes to estimate the difference in dielectric properties. Field GPR survey has been carried out at selected eight locations in Bangalore. GPR data has been collected and thickness is evaluated, in the same location boreholes were drilled core samples are collected. Thickness of core samples are measured in the lab and compared with GPR results. The obtained results from both borehole data and GPR data shows almost similar.

In the past few decades, rapid urbanization can be seen all over the world, while most of this ha... more In the past few decades, rapid urbanization can be seen all over the world, while most of this has occurred in developing countries, owing to the breakdown of the rural economy and the consequential migration of rural population to urban areas. It is foreseen that severe devastation and high death tolls could be resulted if a major earthquake occurs in one of these urban cities, where fragile buildings and infrastructures prevail. On the other hand, scrap tire disposal has been a significant environmental problem in many urban cities due to the huge increase in the number of vehicles. It has been a hot topic among engineering community to find new beneficial ways to recycle and reuse the huge stockpile. This paper proposes a new method of utilizing scrap tires for earthquake protection. The method involves mixing scrap tires with soil sediments and placing the mixtures around foundations of building structures for seismic isolation. The validity of the proposed method has been shown by a series of numerical simulations.

$Research paper thumbnail of Characterization of Rail Track Subsurface Using Seismic Refraction Survey$

The efficiency of track foundation material gradually decreases due to insufficient lateral confi... more The efficiency of track foundation material gradually decreases due to insufficient lateral confinement, ballast fouling, and loss of the shear strength of soil due to local liquefaction and clay pumping. This paper presents characterization of rail track subsurface to identify ballast fouling and subsurface layers (capping layer, sub grade) strength using seismic refraction survey. Seismic refraction survey of multichannel analysis of surface wave analysis (MASW) has been carried out in model track and field track. Shear wave velocity obtained from MASW was used to identify the fouling character of track ballast, there by to evaluate track conditions. The shear velocity of fouled ballast increases with fouling percentage and reaches a maximum value then decreases. This character is used to define optimum and critical fouling points of fouled ballast. This article also highlights ballast gradation followed in India and comparison of Indian ballast gradation with international gradation standards. The ballast gradation followed by Indian railways is poorly graded and more favorable for drainage.

Determining flexible and rigid pavement layer thickness and stiffness are important for pavement ... more Determining flexible and rigid pavement layer thickness and stiffness are important for pavement evaluation and provides data for pavement management systems (PMS). Many conventional methods practiced are time consuming and random testing. In this study an attempt has been made to assess thickness and structural characters of the existing road pavements using GPR antenna of 1.6 GHz and MASW of 24 channel geode seismograph with 4.5Hz geophones. Eight testing locations have been carefully selected in Bangalore by considering surface quality and type of roads. GPR and MASW survey has been carried out simultaneous in these locations. GPR gives electromagnetic wave velocity of subsurface layers, which are used to estimate pavement layer thickness. MASW gives shear wave velocity, which are used to estimate low strain dynamic properties of pavement layers. These results are compared with boreholes samples collected in the same locations. Initial comparison shows that these non destructive tests are effective in assessing thickness and quality (stiffness) with accuracy of more than 93% within short time.

Devastating earthquakes have caused large causalities in the early 20 th century in Himalayan reg... more Devastating earthquakes have caused large causalities in the early 20 th century in Himalayan region. Owing to the increase in population and with the increase in the infrastructure, compared to the past the damages will be catastrophic is case of any future event. Many researchers have highlighted the possible existence of seismic gap along the Himalayan region both in terms of time and location. Understanding of site effects and amplification become mandatory in this region. Site amplification depends on the dynamic properties of soil, thickness above rock/ hard layer and input ground motion. Limited attempt has been made in India to measure and understand site effects in deep basic due to paucity of recorded ground motion data at rock and ground. Hence in this paper an attempt has been made to estimate amplification from past event isoseismal map and compared with the surface PGA (Peak Ground Acceleration) obtained from site response analysis for selected sites.