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Nirjuli, India

Tiwari V.K.,Junagadh Agricultural University | Pandey K.P.,Indian Institute of Technology Kharagpur | Pranav P.K.,NERIST
Journal of Terramechanics

A variety of methods, ranging from theoretical to empirical, which have been proposed for predicting and measuring soil-vehicle interaction performance are reviewed. A single wheel tyre testing facility at Indian Institute of Technology, Kharagpur, India, was used to check the applicability of the most widely used traction models, for tyres used in Indian soil conditions. Finally, the coefficients of traction prediction equations developed by Brixius [16] were modified to fit traction data obtained from the testing of the tyres in the Indian soil conditions. © 2010 ISTVS. Published by Elsevier Ltd. Source

Maheshwari B.K.,Indian Institute of Technology Roorkee | Singh H.P.,NERIST | Saran S.,Indian Institute of Technology Roorkee
Journal of Geotechnical and Geoenvironmental Engineering

A study on liquefaction resistance of Solani sand reinforced with geogrid sheet, geosynthetic fiber, and natural coir fiber is reported. Tests were carried out on shake table (vibration table) with sand samples prepared at a relative density of 25%, with and without reinforcements. Synthetic geogrid sheets were used in three different combinations of three, four, and five layers. In case of fibers, the percentage of fibers by weight of dry sand were taken as 0.25, 0.50, and 0.75% and mixed randomly with the sand sample. Theliquefaction parameters, such as the maximum pore water pressure (Umax), maximum pore water pressure built-up time, stay time for Umax, and pore water pressure dissipation time were measured corresponding to various levels of accelerations varying from 0.1-0.4 g. Thefrequency of the dynamic load was kept constant at 5 Hz. The liquefaction resistance of sand was evaluated in terms of maximum pore water pressure ratio (ru max). Test results indicated that on inclusion of fibers and geogrid sheets into the sand samples, the ru max decreased. On increasing the fiber content and number of geogrid sheets, ru max decreasedfurther, and this decrease is significant at a small amplitude of excitation. The averageincrease in liquefaction resistance of sand reinforced with synthetic and coir fibers wasfound to be 88 and 91%, respectively, for 0.75% fiber content, whereas for five layers ofgeogrid sheets, this increase was about 31% at 0.1 g acceleration. © 2012 American Society of Civil Engineers. Source

International Journal of Earth Sciences and Engineering

Huge quantities of coal ash produced from thermal power plants are very fine, non-plastic and of low unit weight and are loosely disposed into lagoons or ponds covering an area of several square kilometres. These ashes in ponds, called pond ash are having low load carrying capacity and poor settlement characteristics. This material in their saturated condition may be susceptible to liquefaction during earthquakes. On the other hand the performance of such materials can substantially be improved by applying soil reinforcement techniques and their liquefaction potential can be reduced. Keeping this in view and in order to rehabilitate the abandoned ash ponds, it is therefore necessary to evaluate the liquefaction resistance and settlement susceptibility of pond ashIn the present study, a number of tests were performed on a small Vibration (Shake) Table imparting harmonic excitation of 0.3g amplitude under the frequency of 5 Hz to pond ash samples prepared at relative densities of 20% without and with stone-sand columns at 4d c/c spacing, where d is diameter of stone column. Tests were also conducted on improved pond with various surcharge loads. The liquefaction parameters of pond ash such as maximum excess pore water pressure (Umax), maximum excess pore water pressure built up time (t1), Maximum pore water pressure stay time (t2), complete excess pore pressure dissipation time (t3) were measured with the help of glass tube piezometer and stop watch. The liquefaction resistance of pond ash was evaluated in terms of maximum pore water pressure ratio (rumax = Umax/v') for all the tests. It was observed that the liquefaction resistance of pond ash increases with the inclusion of stone-sand columns. It was also observed that the liquefaction resistance of pond ash further increases when various surcharge loads are applied on the samples of pond ash improved with stone-sand columns Thus there is a significant increase in liquefaction resistance of pond ash due to surcharge loads. © 2013 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved. Source

Singh A.D.,NERIST | Subadar R.,NEHU
AEU - International Journal of Electronics and Communications

An expression for the probability distribution function (PDF) of the signal-to-noise ratio of a selection combining receiver in two-wave with diffuse power fading channel is derived. Using this PDF expression, the capacity for the different adaptive transmission techniques employing selection combining (SC) are obtained. The study presents the effects of the ratio of total dominant signal power to the scattered signal power on the system capacity. The change in the capacity of the system with the diversity order for a SC receiver in the fading channel is also presented. © 2013 Elsevier GmbH. Source

Singh T.J.,NERIST | Samanta S.,NERIST
Materials Today: Proceedings

In recent years, the interest of using the fiber reinforced composites (FRCs) has increased due to its potential for replacing the traditional materials in various applications. Kevlar fiber, due to its unique properties such as higher strength to mass ratio and modulus, has become very popular as reinforcement in composite materials and its application has growth considerably. However, for enhancing its properties in various applications, a proper characterization is very important. Many researches have been conducted in recent years, for characterization of Kevlar fiber and its composites. In this paper, a state-of-the art review of these characterizations is presented. © 2015 Elsevier Ltd. Source

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