Experience from past earthquakes has demonstrated the vulnerability of structures to seismically ... more Experience from past earthquakes has demonstrated the vulnerability of structures to seismically induced ground deformation. During earthquake, soil can fail due to liquefaction with devastating effect such as landslides, lateral spreading, or large ground settlement. The phenomenon of liquefaction of soil had been observed for many years, but was brought to the attention of engineers after Niigata (1964) Alaska earthquakes (1964). Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world (Borcherdt R.D 1991; Dobry R, 1981). During the Bhuj earthquake, India on 26th January 2001 (M=7.7) lot of damages had been occurred due to liquefaction and other ground failures (Rao and Mohanty, 2001). In this paper, a preliminary liquefaction hazard assessment was carried out using the availa...
Jet grouting employs the injection of a controlled amount of cement grout into the required volum... more Jet grouting employs the injection of a controlled amount of cement grout into the required volume of soil mass to improve the in situ ground. This ground improvement technique is applied for foundation modification and restoration works such as for waterproofing of dam foundations, confinement for excavations, underpinning of foundations, limiting subsidence over tunnels, etc. This technique can help improve the soil to support foundation loads with minimal settlement and function as excavation support or serve as both foundation and excavation support in a single operation. Such dual capability of the system increases the economic viability by saving time and cost. This paper briefly explains the limitations of various ground improvement methods, the applicability of jet grouting for various geotechnical engineering challenges, the importance of a field quality plan to achieve required design aspects. Case studies are presented that demonstrate the versatility of this emerging tec...
Advancements in Materials, Health and Safety towards Sustainable Energy & Environment (MHS-2014), Aug 2014
The damage induced by seismic events is well known among the civil engineering, geological and se... more The damage induced by seismic events is well known among the civil engineering, geological and seismological community. Seismologists and geologists who study this hazard at a deeper level are concerned more with the history and cause of earthquake events rather than their effects. When considering the engineering point of view, Civil engineers who work with the finding of these researchers work on the seismic effects on the substructures and super structures. When seismic energy is released during an earthquake it passes from the bedrock, then through the soil and to the sub structure through which it is transmitted to the super structure. Liquefaction phenomena is a consequence of earthquake induced pore water pressure in the soil due to this released energy. This phenomenon is uncertain and varies with the change in drainage and soil density. Various deterministic and probabilistic based methods have been developed in the recent past after various case histories. It is crucial to understand the performance of critical structures such as pipelines, road networks, nuclear reactors etc during liquefaction. The current study majorly focuses on the liquefaction assessment for critical structures using numerical modeling. Sand particles are modeled and tested under dynamic loading to understand the microscopic behavior of the particles. The resulting information can be used by the geotechnical engineers while constructing foundation system for nuclear reactors.
Granular materials such as soil are inherently discrete and their behavior is very complex.
Und... more Granular materials such as soil are inherently discrete and their behavior is very complex.
Understanding behavior of such materials under cyclic loading is intricate. Traditionally, continuum
principles are employed to study the deformation of soil by geotechnical engineers. But, discontinuous
nature of soil is required to be considered to understand micro features such as anisotropy, dilatancy,
shear localization etc. Also the strength loss when subjected to cyclic loading is affected by particle size,
shape and its distribution. In this paper 3D discrete element modeling of cyclic triaxial test was carried
out with respect to different particle size distribution and void ratios under drained condition. This study
evaluates the dependence of shear modulus on particle distribution.
The complexity involved in understanding physical phenomena is obvious and can be attempted by
... more The complexity involved in understanding physical phenomena is obvious and can be attempted by
simulating them. Simulation of complex phenomena such as liquefaction of soil requires the understanding of
mechanism rather than the basis for the cause. Numerical simulations are capable of providing a comprehensible
basis for such complex phenomena. In this study, it has been attempted to understand the behavior of granular soils
under cyclic loading by 3D modeling of cyclic triaxial test. Nonlinear behavior of soil can be best embodied by
Discrete Element Modeling (DEM) as it considers soil as discrete assembly of particles. So, using DEM cyclic
triaxial testing has been modeled in undrained condition for an assemblage of random spherical particles of equal
and different sizes. From the analysis it has been identified that at a constant confining pressure and loading,
uniformly graded sample has a greater resistance to failure during cyclic loading than non-uniform distribution. The
outcome of the study is useful to understand liquefaction phenomena.
The microtremor method is very useful in urban areas to estimate local site effects for microzona... more The microtremor method is very useful in urban areas to estimate local site effects for microzonation
purposes. As seismic waves propagate from bedrock to the ground, their characteristics are site
specific due to the heterogeneity of substrata. Source, path and site effects are prime parameters
that affect ground response. Many destructive earthquakes that occurred in the past (e.g. Bhuj 2001,
Bingol 2003, Kashmir 2005, Haiti 2010, Tohoku 2011, Van 2011 and Yunnan 2012) clearly illustrate
the effects of local soils on damage severity and pattern. The Indian sub-continent has more than
400 major faults that influence seismic activity and India has experienced several devastating
earthquakes (Assam 1897 (M58?7), Kangra 1905 (M58?6), Bihar-Nepal 1934 (M58?4), AssamTibet 1950 (M58?7), Latur 1993 (M56?4), Chamoli 1999 (M56?8), Bhuj 2001 (M57?6) and Sikkim
2011 (M56?9)). The state of Andhra Pradesh is located in the central part of peninsular India (zones II and III according to Indian seismic code) and has a record of earthquakes along the coast. This study considered Vijayawada (zone III), the third largest city in the state. Microtremor surveys were carried
out at 75 different locations in the Vijayawada urban area and analysis was carried out using the Nakamura technique. Dynamic characterisation was carried out by considering the shape of the response curve, horizontal to vertical (H/V) amplitude, predominant frequency and the characteristic
soil profile at all the test sites. Based on this detailed analysis, a classification is proposed and a predominant frequency map of the study area was developed. It was found that areas in the north eastern and south eastern parts of the city, with silty and clayey sand formations, have comparatively high predominant frequencies (>4 Hz). The northern and western parts of the city, with high silty clay and silty sand, are characterised by moderate frequency values (2–4 Hz). Low (,2 Hz) values of predominant frequencies were observed at a few locations. The H/V amplitudes are high (2–3) in the eastern and western regions.
15th World Conference on Earthquake Engineering (15 WCEE), May 2012
It is the most discerned fact that earthquake ground motion alters as it propagates through the s... more It is the most discerned fact that earthquake ground motion alters as it propagates through the soil from bedrock to
the surface. The parameters that need to be defined in order to estimate the ground response during an earthquake
are mainly dependent on the earthquake magnitude, local geology, surface topography, fault mechanism, the length
of the propagation path between the source and site, and dynamic properties of the soil through which the seismic
waves travel from the focus (Abrahamson & Shedlock 1997). The ground motion analysis is one of the pivotal tasks
of a geotechnical engineer in seismically active areas. In this paper, a study on ground response analysis at the Park
hotel located in Kolkata city, India is carried out detailed which lies in seismic zone III (IS: 1893, 2002) of the
zonation map of India. It has several active faults in the vicinity. The Peak Ground Acceleration (PGA) of the city
ranges from 0.1g to 0.34g. Amplification has always been a significant parameter for civil engineering structures.
The site amplification factors for the city are found out using the shear wave velocities with which the ground
response can be analyzed.
Mechanisms related to the local soil and rock properties have the capacity to influe... more Mechanisms related to the local soil and rock properties have the capacity to influence ground motions and
inturn regulate damage. Amplification mechanisms control the frequency content of ground motions. The city of Vijayawada
which falls in zone III according to IS 1893:2002 is one of the important and a major business centre in the state of Andhra
Pradesh, India. It is located on the banks of the river Krishna which occupies an area of about 73 km
2
and is located at 16 31’ N
latitude and 80 39’ E longitude. To identify the dominant earth period and study the dynamical behavior of alluvium in the ci ty
of Vijayawada the microtremor survey in 67 sites have been recorded. Microtremor is one of the recent advances i n the
geophysical survey techniques but is quite different from the other methods. The results from the Microtremor survey provide the fundamental basis for the analysis of the response of the ground to earthquake movement. With spectral analysis of microtremor records, predominant frequencies, amplification factors, vulnerability index of the ground can be determined.
Ground Penetration Radar (GPR) has been used to locate the soil characteristics, water table dep... more Ground Penetration Radar (GPR) has been used to locate the soil characteristics, water table depth, depth of
bedrock, buried utilities and cavities below the ground surface. GPR works by sending a tiny pulse of energy into a material
and recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area
make up what is called a scan. Reflections are produced whenever the energy pulse enters into a material with different
electrical conduction properties (dielectric permittivity) from the material it left. The strength, or amplitude, of the reflection is
determined by the contrast in the dielectric constants of the two materials. This means that a pulse which moves from dry san d
to wet sand will produce a very strong, brilliantly visible reflection, w hile one moving from dry sand to limestone will produce
very weak reflections. Materials with a high dielectric are very conductive. Materials with a high dielectric are very
conductive and thus attenuate the signal rapidly. Water saturation dramatically raises the dielectric of a material, so a survey
area should be carefully inspected for signs of water penetration. Radar surveys should never be conducted through standing
water, no matter how shallow. Depth penetration through a material with a high dielectric will not be very good. At Habsiguda and NGRI stations GPR survey has been carried out in an area of 130m x 20m for identifying the utility and other service lines. Excavation was also made to check the efficiency of the survey carried out.
"It is a well established fact that the degree of damage due to an earthquake depends on the d... more "It is a well established fact that the degree of damage due to an earthquake depends on the dynamic properties of soil and on the amplification of seismic waves. Also geologic deposits can amplify strong ground motions depending on the physical conditions. Amplification can be identified by using written
records in different thickness of soils for one or several earthquakes, but the major restraint is the resource limitation i.e., availability of these records is impossible at all times. This limitation can be overcome by recording the microvibrations of the ground. The city of Vijayawada falling in seismic Zone III, according to Indian Seismic code 1893:2002, is one of the important urban centre and a major business centre in the
state of the Andhra Pradesh, India. It is located on the banks of the holy river Krishna which occupies an area of about 73 km2
and is located 16°31’N latitude and 80° 39’E longitude. To estimate the peak frequency of ground and to study on the loose alluvial strata, extensive microtremor testing has been
carried out in Vijayawada at 66 locations to understand the site specific ground response during earthquake shaking. Microtremor technique is one of the recent advances in the geophysical survey techniques but is quite different from the other methods. Analysis has been done at all test sites using
microtremor records and predominant frequency map is generated which reflects the fundamental characteristics of possible site effects. "
"Site effects play a major role in the seismic ground motion and have been ascertained by many se... more "Site effects play a major role in the seismic ground motion and have been ascertained by many seismologists and earthquake engineers. Traditionally, direct waves were used for the site effect study (Gutenberg, 1957; Borcherdt, 1970)but later it has been realized that the source, path and site characterization are the important parameters that affect earthquake ground motion. Local site effects can cause considerable modification of seismic amplitudes. Depending on the ground characteristics, the ground shaking is influenced, which may result in the amplification (causing resonance) or attenuation. Nonlinear amplification at sediments sites appears to be more pervasive than seismologists used to think (Aki et.al., 1991). Spectral amplification factor is a parameter which can be used to find out theses effects. Site effect is also an important parameter in microzonation study. The information about the local site effects is useful in the simulation of strong ground motions and hence, the results of the site response studies are one of the most important inputs for seismic hazard assessment of a region. In this research paper, Vijayawada city which falls in zone III (IS 1893: 2002) has been considered for the site response study. It is the 34th largest town in India (population wise), and the 3rd largest town in Andhra Pradesh. The shear wave velocities and bulk density are used to estimate the average spectral amplification factor. Amplified site response at the
soft soil sites are obtained using the input shear wave velocities"
Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes, w... more Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes, which insists on the necessity for carrying out seismic hazard analysis and microzonation studies for different regions of the country. Even though the zoning of the country has been done it offers a very vague idea of the earthquake hazard in any particular region due to the lack of database in India with regard to the earthquakes prior to historical period. Detailed geotechnical site characterization is an important task in the seismic hazard analysis for finding out the response of soils below, under cyclic /dynamic loads. In this paper, Vijayawada city which falls in zone III (IS 1893: 2002) has been considered for the detailed study. It is the 34th largest town in India (population wise), and the 3rd largest town in Andhra Pradesh. Using the borehole data collected from different sources, 2 dimensional soil profiles are developed.The predominant soil in the northern, eastern, western and southern part of the city has been identified. Using this geotechnical data, the locations that are prone to liquefaction hazard can also be identified.
Experience from past earthquakes has demonstrated the vulnerability of structures to seismically ... more Experience from past earthquakes has demonstrated the vulnerability of structures to seismically induced ground deformation. During earthquake, soil can fail due to liquefaction with devastating effect such as landslides, lateral spreading, or large ground settlement. The phenomenon of liquefaction of soil had been observed for many years, but was brought to the attention of engineers after Niigata (1964) Alaska earthquakes (1964). Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world (Borcherdt R.D 1991; Dobry R, 1981). During the Bhuj earthquake, India on 26th January 2001 (M=7.7) lot of damages had been occurred due to liquefaction and other ground failures (Rao and Mohanty, 2001). In this paper, a preliminary liquefaction hazard assessment was carried out using the available SPT data. From these investigations it was observed that a vast majority of liquefaction occurrences were associated with sandy soils and silty clays of low plasticity.
Experience from past earthquakes has demonstrated the vulnerability of structures to seismically ... more Experience from past earthquakes has demonstrated the vulnerability of structures to seismically induced ground deformation. During earthquake, soil can fail due to liquefaction with devastating effect such as landslides, lateral spreading, or large ground settlement. The phenomenon of liquefaction of soil had been observed for many years, but was brought to the attention of engineers after Niigata (1964) Alaska earthquakes (1964). Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world (Borcherdt R.D 1991; Dobry R, 1981). During the Bhuj earthquake, India on 26th January 2001 (M=7.7) lot of damages had been occurred due to liquefaction and other ground failures (Rao and Mohanty, 2001). In this paper, a preliminary liquefaction hazard assessment was carried out using the availa...
Jet grouting employs the injection of a controlled amount of cement grout into the required volum... more Jet grouting employs the injection of a controlled amount of cement grout into the required volume of soil mass to improve the in situ ground. This ground improvement technique is applied for foundation modification and restoration works such as for waterproofing of dam foundations, confinement for excavations, underpinning of foundations, limiting subsidence over tunnels, etc. This technique can help improve the soil to support foundation loads with minimal settlement and function as excavation support or serve as both foundation and excavation support in a single operation. Such dual capability of the system increases the economic viability by saving time and cost. This paper briefly explains the limitations of various ground improvement methods, the applicability of jet grouting for various geotechnical engineering challenges, the importance of a field quality plan to achieve required design aspects. Case studies are presented that demonstrate the versatility of this emerging tec...
Advancements in Materials, Health and Safety towards Sustainable Energy & Environment (MHS-2014), Aug 2014
The damage induced by seismic events is well known among the civil engineering, geological and se... more The damage induced by seismic events is well known among the civil engineering, geological and seismological community. Seismologists and geologists who study this hazard at a deeper level are concerned more with the history and cause of earthquake events rather than their effects. When considering the engineering point of view, Civil engineers who work with the finding of these researchers work on the seismic effects on the substructures and super structures. When seismic energy is released during an earthquake it passes from the bedrock, then through the soil and to the sub structure through which it is transmitted to the super structure. Liquefaction phenomena is a consequence of earthquake induced pore water pressure in the soil due to this released energy. This phenomenon is uncertain and varies with the change in drainage and soil density. Various deterministic and probabilistic based methods have been developed in the recent past after various case histories. It is crucial to understand the performance of critical structures such as pipelines, road networks, nuclear reactors etc during liquefaction. The current study majorly focuses on the liquefaction assessment for critical structures using numerical modeling. Sand particles are modeled and tested under dynamic loading to understand the microscopic behavior of the particles. The resulting information can be used by the geotechnical engineers while constructing foundation system for nuclear reactors.
Granular materials such as soil are inherently discrete and their behavior is very complex.
Und... more Granular materials such as soil are inherently discrete and their behavior is very complex.
Understanding behavior of such materials under cyclic loading is intricate. Traditionally, continuum
principles are employed to study the deformation of soil by geotechnical engineers. But, discontinuous
nature of soil is required to be considered to understand micro features such as anisotropy, dilatancy,
shear localization etc. Also the strength loss when subjected to cyclic loading is affected by particle size,
shape and its distribution. In this paper 3D discrete element modeling of cyclic triaxial test was carried
out with respect to different particle size distribution and void ratios under drained condition. This study
evaluates the dependence of shear modulus on particle distribution.
The complexity involved in understanding physical phenomena is obvious and can be attempted by
... more The complexity involved in understanding physical phenomena is obvious and can be attempted by
simulating them. Simulation of complex phenomena such as liquefaction of soil requires the understanding of
mechanism rather than the basis for the cause. Numerical simulations are capable of providing a comprehensible
basis for such complex phenomena. In this study, it has been attempted to understand the behavior of granular soils
under cyclic loading by 3D modeling of cyclic triaxial test. Nonlinear behavior of soil can be best embodied by
Discrete Element Modeling (DEM) as it considers soil as discrete assembly of particles. So, using DEM cyclic
triaxial testing has been modeled in undrained condition for an assemblage of random spherical particles of equal
and different sizes. From the analysis it has been identified that at a constant confining pressure and loading,
uniformly graded sample has a greater resistance to failure during cyclic loading than non-uniform distribution. The
outcome of the study is useful to understand liquefaction phenomena.
The microtremor method is very useful in urban areas to estimate local site effects for microzona... more The microtremor method is very useful in urban areas to estimate local site effects for microzonation
purposes. As seismic waves propagate from bedrock to the ground, their characteristics are site
specific due to the heterogeneity of substrata. Source, path and site effects are prime parameters
that affect ground response. Many destructive earthquakes that occurred in the past (e.g. Bhuj 2001,
Bingol 2003, Kashmir 2005, Haiti 2010, Tohoku 2011, Van 2011 and Yunnan 2012) clearly illustrate
the effects of local soils on damage severity and pattern. The Indian sub-continent has more than
400 major faults that influence seismic activity and India has experienced several devastating
earthquakes (Assam 1897 (M58?7), Kangra 1905 (M58?6), Bihar-Nepal 1934 (M58?4), AssamTibet 1950 (M58?7), Latur 1993 (M56?4), Chamoli 1999 (M56?8), Bhuj 2001 (M57?6) and Sikkim
2011 (M56?9)). The state of Andhra Pradesh is located in the central part of peninsular India (zones II and III according to Indian seismic code) and has a record of earthquakes along the coast. This study considered Vijayawada (zone III), the third largest city in the state. Microtremor surveys were carried
out at 75 different locations in the Vijayawada urban area and analysis was carried out using the Nakamura technique. Dynamic characterisation was carried out by considering the shape of the response curve, horizontal to vertical (H/V) amplitude, predominant frequency and the characteristic
soil profile at all the test sites. Based on this detailed analysis, a classification is proposed and a predominant frequency map of the study area was developed. It was found that areas in the north eastern and south eastern parts of the city, with silty and clayey sand formations, have comparatively high predominant frequencies (>4 Hz). The northern and western parts of the city, with high silty clay and silty sand, are characterised by moderate frequency values (2–4 Hz). Low (,2 Hz) values of predominant frequencies were observed at a few locations. The H/V amplitudes are high (2–3) in the eastern and western regions.
15th World Conference on Earthquake Engineering (15 WCEE), May 2012
It is the most discerned fact that earthquake ground motion alters as it propagates through the s... more It is the most discerned fact that earthquake ground motion alters as it propagates through the soil from bedrock to
the surface. The parameters that need to be defined in order to estimate the ground response during an earthquake
are mainly dependent on the earthquake magnitude, local geology, surface topography, fault mechanism, the length
of the propagation path between the source and site, and dynamic properties of the soil through which the seismic
waves travel from the focus (Abrahamson & Shedlock 1997). The ground motion analysis is one of the pivotal tasks
of a geotechnical engineer in seismically active areas. In this paper, a study on ground response analysis at the Park
hotel located in Kolkata city, India is carried out detailed which lies in seismic zone III (IS: 1893, 2002) of the
zonation map of India. It has several active faults in the vicinity. The Peak Ground Acceleration (PGA) of the city
ranges from 0.1g to 0.34g. Amplification has always been a significant parameter for civil engineering structures.
The site amplification factors for the city are found out using the shear wave velocities with which the ground
response can be analyzed.
Mechanisms related to the local soil and rock properties have the capacity to influe... more Mechanisms related to the local soil and rock properties have the capacity to influence ground motions and
inturn regulate damage. Amplification mechanisms control the frequency content of ground motions. The city of Vijayawada
which falls in zone III according to IS 1893:2002 is one of the important and a major business centre in the state of Andhra
Pradesh, India. It is located on the banks of the river Krishna which occupies an area of about 73 km
2
and is located at 16 31’ N
latitude and 80 39’ E longitude. To identify the dominant earth period and study the dynamical behavior of alluvium in the ci ty
of Vijayawada the microtremor survey in 67 sites have been recorded. Microtremor is one of the recent advances i n the
geophysical survey techniques but is quite different from the other methods. The results from the Microtremor survey provide the fundamental basis for the analysis of the response of the ground to earthquake movement. With spectral analysis of microtremor records, predominant frequencies, amplification factors, vulnerability index of the ground can be determined.
Ground Penetration Radar (GPR) has been used to locate the soil characteristics, water table dep... more Ground Penetration Radar (GPR) has been used to locate the soil characteristics, water table depth, depth of
bedrock, buried utilities and cavities below the ground surface. GPR works by sending a tiny pulse of energy into a material
and recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area
make up what is called a scan. Reflections are produced whenever the energy pulse enters into a material with different
electrical conduction properties (dielectric permittivity) from the material it left. The strength, or amplitude, of the reflection is
determined by the contrast in the dielectric constants of the two materials. This means that a pulse which moves from dry san d
to wet sand will produce a very strong, brilliantly visible reflection, w hile one moving from dry sand to limestone will produce
very weak reflections. Materials with a high dielectric are very conductive. Materials with a high dielectric are very
conductive and thus attenuate the signal rapidly. Water saturation dramatically raises the dielectric of a material, so a survey
area should be carefully inspected for signs of water penetration. Radar surveys should never be conducted through standing
water, no matter how shallow. Depth penetration through a material with a high dielectric will not be very good. At Habsiguda and NGRI stations GPR survey has been carried out in an area of 130m x 20m for identifying the utility and other service lines. Excavation was also made to check the efficiency of the survey carried out.
"It is a well established fact that the degree of damage due to an earthquake depends on the d... more "It is a well established fact that the degree of damage due to an earthquake depends on the dynamic properties of soil and on the amplification of seismic waves. Also geologic deposits can amplify strong ground motions depending on the physical conditions. Amplification can be identified by using written
records in different thickness of soils for one or several earthquakes, but the major restraint is the resource limitation i.e., availability of these records is impossible at all times. This limitation can be overcome by recording the microvibrations of the ground. The city of Vijayawada falling in seismic Zone III, according to Indian Seismic code 1893:2002, is one of the important urban centre and a major business centre in the
state of the Andhra Pradesh, India. It is located on the banks of the holy river Krishna which occupies an area of about 73 km2
and is located 16°31’N latitude and 80° 39’E longitude. To estimate the peak frequency of ground and to study on the loose alluvial strata, extensive microtremor testing has been
carried out in Vijayawada at 66 locations to understand the site specific ground response during earthquake shaking. Microtremor technique is one of the recent advances in the geophysical survey techniques but is quite different from the other methods. Analysis has been done at all test sites using
microtremor records and predominant frequency map is generated which reflects the fundamental characteristics of possible site effects. "
"Site effects play a major role in the seismic ground motion and have been ascertained by many se... more "Site effects play a major role in the seismic ground motion and have been ascertained by many seismologists and earthquake engineers. Traditionally, direct waves were used for the site effect study (Gutenberg, 1957; Borcherdt, 1970)but later it has been realized that the source, path and site characterization are the important parameters that affect earthquake ground motion. Local site effects can cause considerable modification of seismic amplitudes. Depending on the ground characteristics, the ground shaking is influenced, which may result in the amplification (causing resonance) or attenuation. Nonlinear amplification at sediments sites appears to be more pervasive than seismologists used to think (Aki et.al., 1991). Spectral amplification factor is a parameter which can be used to find out theses effects. Site effect is also an important parameter in microzonation study. The information about the local site effects is useful in the simulation of strong ground motions and hence, the results of the site response studies are one of the most important inputs for seismic hazard assessment of a region. In this research paper, Vijayawada city which falls in zone III (IS 1893: 2002) has been considered for the site response study. It is the 34th largest town in India (population wise), and the 3rd largest town in Andhra Pradesh. The shear wave velocities and bulk density are used to estimate the average spectral amplification factor. Amplified site response at the
soft soil sites are obtained using the input shear wave velocities"
Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes, w... more Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes, which insists on the necessity for carrying out seismic hazard analysis and microzonation studies for different regions of the country. Even though the zoning of the country has been done it offers a very vague idea of the earthquake hazard in any particular region due to the lack of database in India with regard to the earthquakes prior to historical period. Detailed geotechnical site characterization is an important task in the seismic hazard analysis for finding out the response of soils below, under cyclic /dynamic loads. In this paper, Vijayawada city which falls in zone III (IS 1893: 2002) has been considered for the detailed study. It is the 34th largest town in India (population wise), and the 3rd largest town in Andhra Pradesh. Using the borehole data collected from different sources, 2 dimensional soil profiles are developed.The predominant soil in the northern, eastern, western and southern part of the city has been identified. Using this geotechnical data, the locations that are prone to liquefaction hazard can also be identified.
Experience from past earthquakes has demonstrated the vulnerability of structures to seismically ... more Experience from past earthquakes has demonstrated the vulnerability of structures to seismically induced ground deformation. During earthquake, soil can fail due to liquefaction with devastating effect such as landslides, lateral spreading, or large ground settlement. The phenomenon of liquefaction of soil had been observed for many years, but was brought to the attention of engineers after Niigata (1964) Alaska earthquakes (1964). Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world (Borcherdt R.D 1991; Dobry R, 1981). During the Bhuj earthquake, India on 26th January 2001 (M=7.7) lot of damages had been occurred due to liquefaction and other ground failures (Rao and Mohanty, 2001). In this paper, a preliminary liquefaction hazard assessment was carried out using the available SPT data. From these investigations it was observed that a vast majority of liquefaction occurrences were associated with sandy soils and silty clays of low plasticity.
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Papers by Akhila Manne
Understanding behavior of such materials under cyclic loading is intricate. Traditionally, continuum
principles are employed to study the deformation of soil by geotechnical engineers. But, discontinuous
nature of soil is required to be considered to understand micro features such as anisotropy, dilatancy,
shear localization etc. Also the strength loss when subjected to cyclic loading is affected by particle size,
shape and its distribution. In this paper 3D discrete element modeling of cyclic triaxial test was carried
out with respect to different particle size distribution and void ratios under drained condition. This study
evaluates the dependence of shear modulus on particle distribution.
simulating them. Simulation of complex phenomena such as liquefaction of soil requires the understanding of
mechanism rather than the basis for the cause. Numerical simulations are capable of providing a comprehensible
basis for such complex phenomena. In this study, it has been attempted to understand the behavior of granular soils
under cyclic loading by 3D modeling of cyclic triaxial test. Nonlinear behavior of soil can be best embodied by
Discrete Element Modeling (DEM) as it considers soil as discrete assembly of particles. So, using DEM cyclic
triaxial testing has been modeled in undrained condition for an assemblage of random spherical particles of equal
and different sizes. From the analysis it has been identified that at a constant confining pressure and loading,
uniformly graded sample has a greater resistance to failure during cyclic loading than non-uniform distribution. The
outcome of the study is useful to understand liquefaction phenomena.
purposes. As seismic waves propagate from bedrock to the ground, their characteristics are site
specific due to the heterogeneity of substrata. Source, path and site effects are prime parameters
that affect ground response. Many destructive earthquakes that occurred in the past (e.g. Bhuj 2001,
Bingol 2003, Kashmir 2005, Haiti 2010, Tohoku 2011, Van 2011 and Yunnan 2012) clearly illustrate
the effects of local soils on damage severity and pattern. The Indian sub-continent has more than
400 major faults that influence seismic activity and India has experienced several devastating
earthquakes (Assam 1897 (M58?7), Kangra 1905 (M58?6), Bihar-Nepal 1934 (M58?4), AssamTibet 1950 (M58?7), Latur 1993 (M56?4), Chamoli 1999 (M56?8), Bhuj 2001 (M57?6) and Sikkim
2011 (M56?9)). The state of Andhra Pradesh is located in the central part of peninsular India (zones II and III according to Indian seismic code) and has a record of earthquakes along the coast. This study considered Vijayawada (zone III), the third largest city in the state. Microtremor surveys were carried
out at 75 different locations in the Vijayawada urban area and analysis was carried out using the Nakamura technique. Dynamic characterisation was carried out by considering the shape of the response curve, horizontal to vertical (H/V) amplitude, predominant frequency and the characteristic
soil profile at all the test sites. Based on this detailed analysis, a classification is proposed and a predominant frequency map of the study area was developed. It was found that areas in the north eastern and south eastern parts of the city, with silty and clayey sand formations, have comparatively high predominant frequencies (>4 Hz). The northern and western parts of the city, with high silty clay and silty sand, are characterised by moderate frequency values (2–4 Hz). Low (,2 Hz) values of predominant frequencies were observed at a few locations. The H/V amplitudes are high (2–3) in the eastern and western regions.
the surface. The parameters that need to be defined in order to estimate the ground response during an earthquake
are mainly dependent on the earthquake magnitude, local geology, surface topography, fault mechanism, the length
of the propagation path between the source and site, and dynamic properties of the soil through which the seismic
waves travel from the focus (Abrahamson & Shedlock 1997). The ground motion analysis is one of the pivotal tasks
of a geotechnical engineer in seismically active areas. In this paper, a study on ground response analysis at the Park
hotel located in Kolkata city, India is carried out detailed which lies in seismic zone III (IS: 1893, 2002) of the
zonation map of India. It has several active faults in the vicinity. The Peak Ground Acceleration (PGA) of the city
ranges from 0.1g to 0.34g. Amplification has always been a significant parameter for civil engineering structures.
The site amplification factors for the city are found out using the shear wave velocities with which the ground
response can be analyzed.
inturn regulate damage. Amplification mechanisms control the frequency content of ground motions. The city of Vijayawada
which falls in zone III according to IS 1893:2002 is one of the important and a major business centre in the state of Andhra
Pradesh, India. It is located on the banks of the river Krishna which occupies an area of about 73 km
2
and is located at 16 31’ N
latitude and 80 39’ E longitude. To identify the dominant earth period and study the dynamical behavior of alluvium in the ci ty
of Vijayawada the microtremor survey in 67 sites have been recorded. Microtremor is one of the recent advances i n the
geophysical survey techniques but is quite different from the other methods. The results from the Microtremor survey provide the fundamental basis for the analysis of the response of the ground to earthquake movement. With spectral analysis of microtremor records, predominant frequencies, amplification factors, vulnerability index of the ground can be determined.
bedrock, buried utilities and cavities below the ground surface. GPR works by sending a tiny pulse of energy into a material
and recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area
make up what is called a scan. Reflections are produced whenever the energy pulse enters into a material with different
electrical conduction properties (dielectric permittivity) from the material it left. The strength, or amplitude, of the reflection is
determined by the contrast in the dielectric constants of the two materials. This means that a pulse which moves from dry san d
to wet sand will produce a very strong, brilliantly visible reflection, w hile one moving from dry sand to limestone will produce
very weak reflections. Materials with a high dielectric are very conductive. Materials with a high dielectric are very
conductive and thus attenuate the signal rapidly. Water saturation dramatically raises the dielectric of a material, so a survey
area should be carefully inspected for signs of water penetration. Radar surveys should never be conducted through standing
water, no matter how shallow. Depth penetration through a material with a high dielectric will not be very good. At Habsiguda and NGRI stations GPR survey has been carried out in an area of 130m x 20m for identifying the utility and other service lines. Excavation was also made to check the efficiency of the survey carried out.
records in different thickness of soils for one or several earthquakes, but the major restraint is the resource limitation i.e., availability of these records is impossible at all times. This limitation can be overcome by recording the microvibrations of the ground. The city of Vijayawada falling in seismic Zone III, according to Indian Seismic code 1893:2002, is one of the important urban centre and a major business centre in the
state of the Andhra Pradesh, India. It is located on the banks of the holy river Krishna which occupies an area of about 73 km2
and is located 16°31’N latitude and 80° 39’E longitude. To estimate the peak frequency of ground and to study on the loose alluvial strata, extensive microtremor testing has been
carried out in Vijayawada at 66 locations to understand the site specific ground response during earthquake shaking. Microtremor technique is one of the recent advances in the geophysical survey techniques but is quite different from the other methods. Analysis has been done at all test sites using
microtremor records and predominant frequency map is generated which reflects the fundamental characteristics of possible site effects. "
soft soil sites are obtained using the input shear wave velocities"
Understanding behavior of such materials under cyclic loading is intricate. Traditionally, continuum
principles are employed to study the deformation of soil by geotechnical engineers. But, discontinuous
nature of soil is required to be considered to understand micro features such as anisotropy, dilatancy,
shear localization etc. Also the strength loss when subjected to cyclic loading is affected by particle size,
shape and its distribution. In this paper 3D discrete element modeling of cyclic triaxial test was carried
out with respect to different particle size distribution and void ratios under drained condition. This study
evaluates the dependence of shear modulus on particle distribution.
simulating them. Simulation of complex phenomena such as liquefaction of soil requires the understanding of
mechanism rather than the basis for the cause. Numerical simulations are capable of providing a comprehensible
basis for such complex phenomena. In this study, it has been attempted to understand the behavior of granular soils
under cyclic loading by 3D modeling of cyclic triaxial test. Nonlinear behavior of soil can be best embodied by
Discrete Element Modeling (DEM) as it considers soil as discrete assembly of particles. So, using DEM cyclic
triaxial testing has been modeled in undrained condition for an assemblage of random spherical particles of equal
and different sizes. From the analysis it has been identified that at a constant confining pressure and loading,
uniformly graded sample has a greater resistance to failure during cyclic loading than non-uniform distribution. The
outcome of the study is useful to understand liquefaction phenomena.
purposes. As seismic waves propagate from bedrock to the ground, their characteristics are site
specific due to the heterogeneity of substrata. Source, path and site effects are prime parameters
that affect ground response. Many destructive earthquakes that occurred in the past (e.g. Bhuj 2001,
Bingol 2003, Kashmir 2005, Haiti 2010, Tohoku 2011, Van 2011 and Yunnan 2012) clearly illustrate
the effects of local soils on damage severity and pattern. The Indian sub-continent has more than
400 major faults that influence seismic activity and India has experienced several devastating
earthquakes (Assam 1897 (M58?7), Kangra 1905 (M58?6), Bihar-Nepal 1934 (M58?4), AssamTibet 1950 (M58?7), Latur 1993 (M56?4), Chamoli 1999 (M56?8), Bhuj 2001 (M57?6) and Sikkim
2011 (M56?9)). The state of Andhra Pradesh is located in the central part of peninsular India (zones II and III according to Indian seismic code) and has a record of earthquakes along the coast. This study considered Vijayawada (zone III), the third largest city in the state. Microtremor surveys were carried
out at 75 different locations in the Vijayawada urban area and analysis was carried out using the Nakamura technique. Dynamic characterisation was carried out by considering the shape of the response curve, horizontal to vertical (H/V) amplitude, predominant frequency and the characteristic
soil profile at all the test sites. Based on this detailed analysis, a classification is proposed and a predominant frequency map of the study area was developed. It was found that areas in the north eastern and south eastern parts of the city, with silty and clayey sand formations, have comparatively high predominant frequencies (>4 Hz). The northern and western parts of the city, with high silty clay and silty sand, are characterised by moderate frequency values (2–4 Hz). Low (,2 Hz) values of predominant frequencies were observed at a few locations. The H/V amplitudes are high (2–3) in the eastern and western regions.
the surface. The parameters that need to be defined in order to estimate the ground response during an earthquake
are mainly dependent on the earthquake magnitude, local geology, surface topography, fault mechanism, the length
of the propagation path between the source and site, and dynamic properties of the soil through which the seismic
waves travel from the focus (Abrahamson & Shedlock 1997). The ground motion analysis is one of the pivotal tasks
of a geotechnical engineer in seismically active areas. In this paper, a study on ground response analysis at the Park
hotel located in Kolkata city, India is carried out detailed which lies in seismic zone III (IS: 1893, 2002) of the
zonation map of India. It has several active faults in the vicinity. The Peak Ground Acceleration (PGA) of the city
ranges from 0.1g to 0.34g. Amplification has always been a significant parameter for civil engineering structures.
The site amplification factors for the city are found out using the shear wave velocities with which the ground
response can be analyzed.
inturn regulate damage. Amplification mechanisms control the frequency content of ground motions. The city of Vijayawada
which falls in zone III according to IS 1893:2002 is one of the important and a major business centre in the state of Andhra
Pradesh, India. It is located on the banks of the river Krishna which occupies an area of about 73 km
2
and is located at 16 31’ N
latitude and 80 39’ E longitude. To identify the dominant earth period and study the dynamical behavior of alluvium in the ci ty
of Vijayawada the microtremor survey in 67 sites have been recorded. Microtremor is one of the recent advances i n the
geophysical survey techniques but is quite different from the other methods. The results from the Microtremor survey provide the fundamental basis for the analysis of the response of the ground to earthquake movement. With spectral analysis of microtremor records, predominant frequencies, amplification factors, vulnerability index of the ground can be determined.
bedrock, buried utilities and cavities below the ground surface. GPR works by sending a tiny pulse of energy into a material
and recording the strength and the time required for the return of any reflected signal. A series of pulses over a single area
make up what is called a scan. Reflections are produced whenever the energy pulse enters into a material with different
electrical conduction properties (dielectric permittivity) from the material it left. The strength, or amplitude, of the reflection is
determined by the contrast in the dielectric constants of the two materials. This means that a pulse which moves from dry san d
to wet sand will produce a very strong, brilliantly visible reflection, w hile one moving from dry sand to limestone will produce
very weak reflections. Materials with a high dielectric are very conductive. Materials with a high dielectric are very
conductive and thus attenuate the signal rapidly. Water saturation dramatically raises the dielectric of a material, so a survey
area should be carefully inspected for signs of water penetration. Radar surveys should never be conducted through standing
water, no matter how shallow. Depth penetration through a material with a high dielectric will not be very good. At Habsiguda and NGRI stations GPR survey has been carried out in an area of 130m x 20m for identifying the utility and other service lines. Excavation was also made to check the efficiency of the survey carried out.
records in different thickness of soils for one or several earthquakes, but the major restraint is the resource limitation i.e., availability of these records is impossible at all times. This limitation can be overcome by recording the microvibrations of the ground. The city of Vijayawada falling in seismic Zone III, according to Indian Seismic code 1893:2002, is one of the important urban centre and a major business centre in the
state of the Andhra Pradesh, India. It is located on the banks of the holy river Krishna which occupies an area of about 73 km2
and is located 16°31’N latitude and 80° 39’E longitude. To estimate the peak frequency of ground and to study on the loose alluvial strata, extensive microtremor testing has been
carried out in Vijayawada at 66 locations to understand the site specific ground response during earthquake shaking. Microtremor technique is one of the recent advances in the geophysical survey techniques but is quite different from the other methods. Analysis has been done at all test sites using
microtremor records and predominant frequency map is generated which reflects the fundamental characteristics of possible site effects. "
soft soil sites are obtained using the input shear wave velocities"