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2 results on '"Shyama Sivan"'

1. A study of the influence of rainfall datasets' spatial resolution on stream simulation in Chaliyar River Basin, India

Author

Silpa Senan, Jobin Thomas, Vamsi Krishna Vema, P. J. Jainet, Sinan Nizar, Shyama Sivan, and K. P. Sudheer

Subjects
chaliyar river basin, imd gridded rainfall, rainfall variability, swat, western ghats, Environmental technology. Sanitary engineering, TD1-1066, Environmental sciences, GE1-350
Abstract

Rainfall is a vital input to model watershed hydrology, and the availability of numerous gridded and point-observed rainfall datasets poses a major challenge to the modellers to choose the appropriate data. This study compares three gridded rainfall datasets (i.e., 1° × 1°, 0.5° × 0.5°, and 0.25° × 0.25°) and point rainfall observations of the India Meteorological Department (IMD) on the simulation of streamflow of a river basin in the southern Western Ghats (India) using the Soil and Water Assessment Tool (SWAT). The results show that the different datasets lead to different optimal model parameter values and consequent water balance components, significantly in groundwater hydrology. The 0.5° × 0.5° and 0.25° × 0.25° datasets result in comparable SWAT model performances (NSE = 0.75 and 0.70, respectively), probably due to the similarity in the rain gauge network density employed for deriving the datasets and also due to the spatial discretization threshold used for sub-watershed delineation. However, the coarser resolution data (1° × 1°) results in poor performance (NSE = 0.21). The study suggests that the choice of rainfall data depends on the spatial resolution of the data and the spatial discretization threshold while compromising the computational requirement vis-à-vis simulation accuracy. HIGHLIGHTS The effects of various IMD gridded rainfall datasets and point rainfall observations on the simulation of streamflow of a river basin of the southern Western Ghats (India) was assessed.; The optimal parameter values for 1° × 1° rainfall data are far deviated from the point observation data.; The 0.25° × 0.25° and 0.5° × 0.5° have better model performances compared to 1° × 1° and point observations.;

Published
2022
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2. Performance evaluation of warm mix asphalt using natural rubber modified bitumen and cashew nut shell liquid

Author

P. S. Sibinesh, Shyama Sivan, Margret Sherin Joseph, C. S. Bindu, and Shithin George

Subjects
050210 logistics & transportation, Materials science, Rut, 05 social sciences, 0211 other engineering and technologies, Compaction, 02 engineering and technology, Fatigue limit, Viscosity, Natural rubber, Mechanics of Materials, Asphalt, visual_art, 021105 building & construction, 0502 economics and business, Dynamic shear rheometer, visual_art.visual_art_medium, Composite material, Rubberized asphalt, Civil and Structural Engineering
Abstract

Warm Mix Asphalt (WMA) is an innovative technology that aims at decreasing the mixing and compaction temperature of asphalt mixtures as compared to the conventional Hot Mix Asphalt (HMA) thereby reducing harmful emissions and fuel consumption. The rubberized asphalt mixtures are found to have better physical and strength properties, but they are compacted at a higher temperature than that of conventional mixes. In this study Cashew Nut Shell Liquid (CNSL), an organic additive, was added from 0.5% to 3 % by weight of the binder at an increment of 0.5 % to modify the bitumen. The optimum content of CNSL to reduce the viscosity was found to be 2% and the viscosity reduction was 44.4 % at 140°C The modified NRMB (Natural Rubber Modified Bitumen) was used to prepare Dense Bituminous Macadam (DBM) and a comparison of volumetric, stability and rutting characteristics of both Natural Rubber modified Hot Mix Asphalt (RHMA) and Natural Rubber modified Warm Mix Asphalt with CNSL additive (RWMA) was made. Storage stability results indicated that there was no phase separation between rubberized bitumen and additive at high temperature and will act as uniform blend at high temperatures. Dynamic Shear Rheometer test results showed that the addition of CNSL to rubberized bitumen increased the values of G*/sinδ and could improve the resistance of asphalt binder against rutting. Stability value of RWMA was 11.5 % higher than that of RHMA and rutting depth was 10.1 % less than that of RHMA. The fatigue strength results obtained from Repeated Load Testing showed that the number of cycles to failure at 20% stress level was 9.04 % more for RWMA than RHMA. All volumetric properties of both RHMA and RWMA were within the limits specified by Ministry of Road Transport and highways (MoRTH) 2013. The statistical analysis authenticates the experimental findings. ANOVA analysis for Marshall Quotient revealed that RWMA had improved compaction characteristics than RHMA and the result for rutting and fatigue strength showed that the additive CSNL and temperature had significant effect on rutting resistance and fatigue life.

Published
2020
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