Papers by Narayan Marasini
International Journal of Physical Modelling in Geotechnics, Sep 1, 2015
During large earthquakes, soil liquefaction has repeatedly damaged many buildings with shallow fo... more During large earthquakes, soil liquefaction has repeatedly damaged many buildings with shallow foundations. Many researchers have continuously worked to develop more reliable countermeasure techniques apposite to the foundation soils of existing buildings. However, most countermeasure techniques available in the current practice are either too expensive or applicable only to new construction sites. Lowering the degree of saturation by artificially injecting air is a newly developed, innovative technique that significantly improves the liquefaction strength of soil. This paper describes a series of centrifuge tests for evaluating the effectiveness of this technique by applying it to the foundation soil underlying shallow foundations of relatively light structures, such as residential buildings. Models of saturated medium dense sand beds with shallow foundations were shaken in a centrifuge. Except for benchmark models, air was injected into the soil in-flight before the shaking event, which lowered the degree of saturation of the soil in the desaturated zone from 100% before air injection to approximately 85%. The test results show that air injection effectively reduced both foundation settlement and pore pressures generated below the foundation.
Soils and Foundations, 2015
Nepal was hit by the M7.8 Gorkha earthquake on April 25, 2015, which was the largest earthquake i... more Nepal was hit by the M7.8 Gorkha earthquake on April 25, 2015, which was the largest earthquake in Nepal's history since 1934. The recent report presented by the Government of Nepal indicates that the recorded death toll has reached about 8800. Following the earthquake, the Japanese Geotechnical Society (JGS), Asian Technical Committee of ISSMGE on Geotechnical Natural Hazards (ATC3), Japan Society of Civil Engineers (JSCE) and Japan Association for Earthquake Engineering (JAEE) decided to jointly dispatch a survey team to Nepal to conduct a reconnaissance survey of the major damage caused by the earthquake. This report summarizes the results of the survey of the geotechnical and structural damage in the Kathmandu valley, which were observed by the survey sub-team between May 1 and 8, 2015. Geotechnical and geological characteristics of a deep soil profile up to 600 m and a shallow profile up to 30 m are also described with the help of the database system established by Bhandary et al. (2012). In order to study the correlation between building damage ratios and the predominant period of ground vibration, a partial exhaustive type survey was conducted along NS line where microtremor measurements had been previously conducted in 2008. The predominant period of ground vibration was short at the ridge of the valley and long at its center, ranging from 1.2 to 4.5 s. A total of 532 buildings were assessed and more than 90% were classified as "No damage" or "Negligible to slight Damage" (Grade 0 and Grade 1), whereas only 5% of buildings were assessed as "Substantial to heavy damage" to "Destruction" (Grade 3 to Grade 5). Five locations were identified where the soil had liquefied. Liquefaction-induced damage to structures at these locations was not found, except at Nepal Engineering College where minor settlement of the college building was observed. During the 1934 earthquake, foundation liquefaction was observed in Tundhikhel area, but in the 2015 earthquake no evidence of liquefaction was detected in this area. The Kathmandu-Bhaktapur Road of Araniko Highway was heavily damaged in the Lokanthali area. The subsidence of soft soils and their lateral spreading in this area may have exacerbated the damage to this road.
Evaluation of liquefaction potential of soils using empirical relations based on field in-situ te... more Evaluation of liquefaction potential of soils using empirical relations based on field in-situ test data is a common practice in liquefaction study. In this study, Standard Penetration Test (SPT) data were used to examine the liquefaction potential of the Kathmandu Valley. In total 66 SPT data among the collected 102 from 33 locations were used for the analysis. The factor of safety against liquefaction (F L ) was calculated and found less than unity (F L <1) in 48 locations, which indicates the high probability of occurrence of liquefaction during the predicted scenario earthquake of magnitude 8 with peak ground acceleration 300gal. Similarly, mineralogical composition and physical index of field soil were compared to the commercially available sand and found more comparable with Toyoura sand. Two Centrifuge models in which one is saturated foundation soil model (Case1) and the other is desaturated foundation soil model by air injection (Case2) using the Toyoura sand were prepar...
International Journal of Disaster Risk Reduction
International Journal of Landslide and Environment, May 28, 2014
Soils and Foundations, 2015
International Journal of Physical Modelling in Geotechnics, 2015
Computer Methods and Recent Advances in Geomechanics, 2014
Soils and Foundations, 2015
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Papers by Narayan Marasini