Faculty Publications
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Item Liquefaction hazard mapping of Chennai, India using SPT data(2011) Anbazhagan, P.; Basavaraj, S.; Premalatha, K.V.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. © 2011 CAFET-INNOVA technical society. All right reserved.Item Modeling duration of lateral shifts in mixed traffic conditions(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2018) Asaithambi, G.; Joseph, J.Traffic on urban roads in developing countries is characterized by wide mix of vehicles with loose lane discipline, which results in parallel movement of vehicles in the same lane. Hence, vehicles not only interact longitudinally with the vehicles ahead but also laterally with vehicles to the sides. Lateral movements have a significant impact on the characteristics of traffic flow and therefore are of great importance in microscopic traffic simulation models. Existing simulation models for mixed traffic conditions model lateral shifts (lateral movements) as an instantaneous process but neglects detailed modeling. However, the duration for lateral shifts is generally in the range of 0.5-15 s. The omission of lateral shift duration from simulation models may have a significant impact on simulation outputs. Also, different vehicle types may have different lateral shift durations due to variations in their physical and operational characteristics. This paper attempts to develop a vehicle-specific lateral shift duration model by considering different explanatory variables such as direction of lateral shift, available space gaps, speeds of subject vehicle and surrounding vehicles, vehicle types, and clearance. The models were estimated using trajectory data collected during medium-flow conditions from an urban arterial in Chennai city, India. The findings from this study have direct implications on modeling lateral shifts in microscopic traffic simulations to be developed specifically for mixed traffic conditions. © 2018 American Society of Civil Engineers.