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Mechanism of Stone Columns for Mitigation of Liquefaction

2026-05-04T12:43:32Z

Title: Mechanism of Stone Columns for Mitigation of Liquefaction Authors: Singh, Anchal Kumar Abstract: Stone columns have been used as an effective technique for improving the engineering behavior of soft clayey grounds and loose silt deposits. The soil improvement via stone columns is achieved by accelerating the consolidation of weak soil due to shortened drainage paths, increasing the load-carrying capacity, and settlement reduction due to the inclusion of stronger granular material. In the present study, two-dimensional numerical analysis was used to assess the effectiveness of stone columns and their improvement mechanisms, in mitigating liquefaction. A case study from 29 March 1999 Chamoli Earthquake was used as a basis of the research with the finite element software package PLAXIS 2D CONNECT Edition V21.00. The main improvement mechanisms of stone columns – densification, drainage, and reinforcement and their individual effects on the improved ground have been investigated. Generally, it is found that considering the densification and drainage effects in the analysis improved the performance of the stone columns, while the reinforcement effect made only a small difference.

LANDSLIDE SUSCEPTIBILITY ASSESSMENT OF CHENAB VALLEY AREA

2026-05-04T12:43:23Z

Title: LANDSLIDE SUSCEPTIBILITY ASSESSMENT OF CHENAB VALLEY AREA Authors: Gupta, Ankit Abstract: The purpose of this dissertation work is to produce a reliable Landslide Susceptibility Mapping (LSM) using Frequency Ratio (FR) and Certainty Factor (CF) models with the aid of ArcGIS software for the Chenab Valley, J&K, India. Remote Sensing (RS) and Geographical Information System (GIS) are powerful tools for assessing landslide hazards and are being used extensively in landslide research for many years. In this study area, about 365 landslides have occurred. These landslide sites can be seen on satellite images and also on Google Earth. Information on many of these landslides is also available on the GSI portal. A landslide inventory map had prepared mainly based on landslide occurrence of the study area. Then, 256 (70 %) landslides were randomly selected for modelling, and the remaining 109 (30 %) landslides were used for the model validation. To produce a landslide susceptibility map using FR & CF models, 13 prominent landslide contributing factors were selected based on hydro-geomorphological characteristics. These landslide contributing factors are the slope, aspect, altitude, geology, distance to lineament, distance to fault, distance to road, distance to drainage, Topographic Wetness Index (TWI), rainfall, curvature, Normalized Difference Vegetation Index (NDVI) and earthquake. These factors were mapped with the aid of ArcGIS software and classified into significant classes using the natural break (Jenks) method. After that, the landslide susceptibility maps had prepared using landslide contributing factors based on the FR and CF models. Based on these maps, the area was further classified into five significant classes, i.e., very low, low, moderate, high, and very high categories based on the severity of landslides. The FR & CF model results showed that approximately 5.9 % & 12.89 % of the study area fell into the very high zone of landslide. The landslide susceptibility maps can be helpful to select a site, predict future landslide chances, and mitigate landslide hazards in the study area. Finally, the accuracy of the landslide susceptibility maps developed from the two models were validated using Area Under the Curve (AUC) analysis. The validation showed that the successor rate curve accuracy of the two models was 89.80 % for the FR and 90.12 % for the CF. The prediction rate curve accuracy of the two models was 88.80 % for the FR model and 88.43 % for the CF model. As per the results, both models showed an approximately similar level of accuracy.

Estimation of Quality Factor of Coda Waves (QC) in Meghalaya Region

2026-05-04T12:43:15Z

Title: Estimation of Quality Factor of Coda Waves (QC) in Meghalaya Region Authors: Balana, Arvind Abstract: The earthquake recorded in the form of a seismogram is a combination of source, path, and site. To know the seismic hazard of a region it is necessary to know each of these factors. In the present thesis, the path/medium characteristic of the Meghalaya region has been studied by estimating the quality factor of coda waves (Qc) using local earthquakes. This report also includes the literature reviews on the estimation of the quality factor of coda waves which have been carried out in the region by various researchers along with the importance and objectives of coda Q as medium characteristics as well as earthquake precursory parameter over other parameters. Attenuation of seismic waves is described by the dimensionless quantity called quality factor ‘Q’ (Knopoff, 1964), which expresses the decay of wave amplitude during its propagation in the medium. It is a combination of both intrinsic attenuations, the loss of elastic energy to heat or another form of energy, and scattering, which is deflection and/or mode conversion of elastic energy due to heterogeneities in the transmitting medium. In the present study, Qc estimates have been obtained by analyzing coda waves of 126 seismograms from 21 local earthquakes recorded in the Meghalaya Himalaya recorded digitally in the region during January-August 2018. For this purpose, the coda waves in a seismogram has been analyzed at seven central frequencies using the single backscattering model. The earthquakes have their epicentral distances within 100 km, focal depths up to 42.7 km with 3.0

Title of Dissertation Seismic Slope Stability of Embankment Dam

2026-05-04T12:41:56Z

Title: Title of Dissertation Seismic Slope Stability of Embankment Dam Authors: Varun, Deepika Abstract: Slope stability is an important concern in the creation of artificial slope & natural slope the necessary criterion for stability analysis is the factor of safety counter to sliding which should be always greater than or equal to one for the slope to be safe. This is true when the slope the slope experiences elastic deformation only. But in case of a strong earthquake motion, the deformation of slope may exceed elastic limit and hence stable displacements can take place. In that case factor of safety as stability measure becomes of no importance and magnitude of the stable displacements turn into measure for calculate approximately the overall stability of the slope. The purpose of the dissertation is to find out the factor of safety of the given Embankment dam slope i.e. Tehri Dam under static and dynamic loading (earthquake) condition using Finite Element Method. This study also involves analysis of the slope stability by Pseudo-Static Process. The probability of permanent displacement of the slope because of three earthquake motions is analysed in this study. The earthquake records considered for this purpose are: Chamoli earthquake 1999, Uttarkashi earthquake 1991,Nepal earthquake 2015.