Journal Articles
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Item Stability analysis of dike to impound freshwater in brackish water estuarine environment(Bentham Science Publishers P.O. Box 294 Bussum 1400 AG, 2020) Krishnan, A.; Kolathayar, S.This paper presents the stability analysis of a dike proposed to impound the river flood waters within an estuary near the west coast of south India. The proposed dike will be located within Ashtamudi Lake, the second largest lake in the state of Kerala, India, separating fresh water from brackish water. Constructing a dike at Munro Island portion of Ashtamudi, which is about 9.23 km from Arabian Sea coast, can meet the water demands of the region as well as prevent the sinking of Island during high tide. The river dike is designed to construct artificially as rock filled structures. The stratigraphy in the top 2 m consists of clayey mud underlined by fine to medium sand up to 6 m followed by alternate layers of clay and sand up the investigated depth of 15 m. In this paper, the stability of the dike located in an estuarine environment has been investigated and the factor of safety values have been determined with varying water level conditions and varying properties of the underlying soil. A detailed parametric study using RocScience software is presented, considering all the design conditions. The expected settlement of the dike is estimated considering the soil profile at the location both manually as well as using software Geo5. Both were in good agreement and the maximum possible settlement was found to be less than half a meter. © 2020.Item Evaluation of liquefaction potential of soil at a power plant site in Chittagong, Bangladesh(IGI Global journaleditor@igi-global.com, 2020) Sengupta, S.; Kolathayar, S.This study presents an evaluation of liquefaction potential for combined cycle power plant site located in the Chittagong district, Bangladesh, using standard penetration test blow counts (SPT-N values). The peak ground acceleration (PGA) values at a bedrock level were estimated deterministically using both linear and point source models as well as different ground motion prediction equations (GMPEs). The surface level hazard was estimated using amplification factors for the soil conditions present and the response spectrum at the center of the plant site was plotted. The liquefaction potential for the site was arrived at by using the SPT-N values of 33 boreholes in the site and at every 3-meter interval from the ground level to a depth of 30 meters. The results from the LPI contours at successive depths indicate that in the majority of the borehole locations, the soil up to 15 meters depth had a significant hazard of liquefaction. These findings from the present study can prove to be crucial from the structural point of view, for any future construction activities in the area. © © 2020, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited.Item Comparative study on bearing capacity of bottom ash-stabilized soil mixed with natural and synthetic fibers(ASTM International service@astm.org, 2020) Prasannan, S.; Kolathayar, S.; Sharma, A.K.This article assesses the strength behavior of bottom ash (BA)-stabilized soil mixed with different fibers through a series of laboratory tests. Optimum BA and fiber percentage were obtained by small scale lab tests like compaction tests and unconfined compressive strength (UCS) tests. From compaction tests with varying proportions of BA (10, 20, 30, and 40 %), the optimum BA content was found to be 30 %. With this optimum BA content, UCS tests were conducted on soil-BA mix with different fibers (coir, areca, sisal, and polyvinyl alcohol) at various percentages (0.5, 1, 1.5, and 2 %) to find the optimum fiber content. A set of model footing tests were done to check the credibility of using fibers as a strengthening material beneath footing to upgrade the engineering properties of soil to make a reasonable subsoil for the foundation. A total of six model footing tests were performed on raw soil, on soil with optimum BA content, and on BA-stabilized soil mixed with different fibers in their optimum percentage (1.5 %). The bearing capacity of unstabilized unreinforced soil was found to increase significantly with the inclusion of fibers. © © 2020 by ASTM InternationalItem Performance of Footing on Clay Bed Reinforced with Coir Cell Networks(American Society of Civil Engineers (ASCE) onlinejls@asce.org 1801 Alexander Bell DriveGEO Reston VA 20191 Alabama, 2020) Kolathayar, S.; Narasimhan, S.; Kamaludeen, R.; Sitharam, T.G.Geocells are three-dimensional polymeric hexagonal pockets that provide lateral confinement to the soil, thereby increasing the bearing capacity of the soil bed. This paper briefly reviews past studies on geocell reinforcement of soil and presents a new product, cells made out of natural coir fiber, as an alternative to commercially available high-density polyethylene (HDPE) geocells. A series of model plate load tests were conducted on unreinforced soil and on soil reinforced with coir geocells to understand the soil reinforcement mechanism. It was observed that with the introduction of coir geocells, the load-bearing capacity of the soil bed increased up to three times and a significant reduction in the settlement was observed in the underlying weak soil bed. The study also presents a comparative performance evaluation of the natural coir cell-reinforced soil with conventional HDPE geocell-reinforced soil. Further, this paper analytically demonstrates the influence of the lateral resistance effect and vertical load dispersion effect incorporated by coir cells in strengthening the soil bed. © 2020 American Society of Civil Engineers.Item Performance Evaluation of Coir Geocells as Soil Retention System Under Dry and Wet Conditions(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2020) Chitrachedu, R.K.; Kolathayar, S.In the present study, coir is used to fabricate geocells and to construct model retaining walls for application in sloppy regions to retain the soil. The performance of coir geocells under dry and wet conditions during rainfall were evaluated by conducting laboratory model tests. The study presents horizontal and vertical deformation against surcharge load for different scenarios of reinforcement using geocells. A comparison was made between the performance of unreinforced slope, high-density polyethylene geocell retaining wall and coir geocell retaining wall to evaluate the potential of coir geocell over synthetic geocell as reinforcement. The roughness and absence of perforations in coir material resisted the movement and failure of the wall for a longer span. The horizontal displacement was more for coir geocell retaining wall compared to wall made of high density polyethylene (HDPE) geocells. This may be due to the interlocking effect in coir HDPE geocell as perforations provide contact between the sand particles. The inexpensive and easily disposable coir can be effectively used as reinforcement in the construction of a retaining wall. © 2020, Springer Nature Switzerland AG.Item Synthesis of Linear JTFA-Based Response Spectra for Structural Response and Seismic Reduction Measures for North-East India(World Scientific, 2020) Devaraj, D.; Ramkrishnan, R.; Prabu, T.; Kolathayar, S.; Sitharam, T.G.North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0-480km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended. © 2020 World Scientific Publishing Company.Item Comparative Study for Performance of Soil Bed Reinforced with Jute and Sisal Geocells as Alternatives to HDPE Geocells(Springer Science and Business Media Deutschland GmbH, 2020) Kolathayar, S.; Sowmya, S.; Priyanka, E.This paper presents the performance of soil bed reinforced with jute and sisal geocells compared to HDPE geocells. The bearing pressure–settlement behaviour of the soil bed reinforced with natural geocells, soil bed reinforced with HDPE geocells and of unreinforced soil bed are discussed. The soil bed reinforced with jute cell and sisal cell showed a uniform increase in the settlement with increase in the applied pressure. The soil reinforced with HDPE geocell, however, showed a sudden rise in the settlement at higher pressure. Sisal mat used for developing the geocell was found to have greater tensile strength, followed by jute mat over HDPE material. Soil reinforced with sisal cells could bear larger stresses at lower strain compared to HDPE geocell. Analytical studies on jute and sisal geocells also were carried out considering the load transfer mechanism of geocell-reinforced soil. © 2020, Springer Nature Switzerland AG.Item Appraisal of Thanneermukkom bund as a coastal reservoir in Kuttanad, Kerala(Taylor and Francis Ltd., 2021) Kolathayar, S.; Amala Krishnan, U.S.; Sitharam, T.G.This paper presents an overview of Thanneermukkom bund with its implications on water security in the region as a freshwater reservoir in the southwest coast of India. The bund was constructed in 1974 to convert southern part of brackish Vembanad Lake into a freshwater reservoir to augment agricultural activities. This paper reviews past studies on the bund and highlights the fact that it is a coastal reservoir though the term coastal reservoir became popular only in the last two decades. The bund divides the Vembanad Lake into a freshwater lake in the south and brackish water lake fed by the ocean in the north. This paper reviews the issues and challenges related to the inefficient operation of the bund and presents possible solutions. The paper proposes to restore this unique coastal reservoir to ensure freshwater supply for drinking and irrigation in the low lands of Kuttanad. © 2021 IAHR and WCCE.Item Near-surface seismic refraction tomography and MASW for site characterization in Phuentsholing, Bhutan Himalaya(Springer Nature, 2021) Sarkar, R.; Kolathayar, S.; Drukpa, D.; Choki, K.; Rai, S.; Tshering, S.T.; Yuden, K.It is essential to understand the soil characteristics of the subsurface layers for any engineering construction. In difficult terrains like hilly areas, conventional methods of investigation are expensive and difficult to conduct. It calls for nondestructive testing methods to get reliable estimates of subsurface properties. In the present study, seismic refraction tomography (SRT) technique and multichannel analysis of surface waves (MASW) methods were carried out along five selected profiles in Phuentsholing region of Bhutan Himalaya. The profile length ranges from 37 to 81.5 m, and depth of imaging down to 10 m. While the SRT data imaged the P-wave velocity (Vp) structures, the MASW imaged the shear wave velocity (Vs) structures. The P-wave images provide a fair knowledge of geological layers, while the MASW images provide S-wave velocity structures (Vs). These results are useful to estimate soil parameters, like the density, Poisson’s ratio, Young’s modulus, shear modulus, N-value and the ultimate bearing capacity. The seismic images reveal the presence of sand, sandy clay, gravels and shale layers below the selected sites. Bhutan Himalayas being seismically vulnerable, the obtained results in terms of shear wave velocity were accustomed to categorize the sites as per NEHRP site classes, and a ground response analysis was performed to determine the reliable amplification factors. From the study, it is suggested that the engineering construction is feasible at all the sites except in one site, where an indication of saturated soil is observed which is vulnerable for liquefaction, and ground needs to be improved before construction at that site. © 2021, The Author(s).Item Probabilistic seismic hazard analysis of North and Central Himalayas using regional ground motion prediction equations(Springer Science and Business Media Deutschland GmbH, 2021) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.Recently developed region-specific GMPEs are used for a comprehensive seismic hazard analysis (SHA) of the North and Central Himalayas (NCH) using a probabilistic approach considering two source models. Vulnerable seismic sources in the areas are identified based on the Seismotectonic Atlas (Dasgupta et al. 2000), published by the Geological Survey of India. An up to date, homogenized and declustered earthquake catalogue is compiled from various sources, with earthquake data since 250 BC, to create a new digitized seismotectonic representation of the region. Regional seismic zones having similar seismicity are recognized based on the Gutenberg-Richter (GR) parameters and the region is delineated into 5 seismic zones. The study area is divided into grids of size 0.05° × 0.05° and the hazard in terms of Peak Ground Acceleration (PGA) at the centre of each grid point is estimated and presented as hazard maps for individual seismic sources, maximum of all sources, and average of both sources. From the current study, it could be concluded that the PGA estimated in the regions is comparatively higher than what is reported in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the region. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.