Kaustav Chatterjee

A Comparative Study on Shear Strength of Soil Using Geogrid and Geotextiles

Failure of retaining walls, roads and collapse of soil have led geotechnical engineers to use reinforced soil to increase its strength. When the soil is unconfined and subjected to compressive stress, tensile stress are developed in the other direction. However if internal reinforcement layers are provided, frictional force is mobilized along the surfaces of the reinforcement layers and strength of the soil is considerably increased. It is a common practice among geotechnical engineers to use geosynthetics for soil reinforcement in various construction works. The major products of geosynthetics includes geotextiles, geogrid and geomembranes. Geogrids are used as reinforcement layers in retaining walls, embankments, road bases and below rail tracks. Geotextiles are used to separate different geomaterials and acts as filtration material to retain the soil particles. In the present study soil is collected from the bed of Solani River in Roorkee, India and soil classification is carried out on the unreinforced soil. Direct shear test is performed on unreinforced soil specimen and soil reinforced with geogrid and geotextiles (woven and non-woven) for different magnitudes of normal stress. It is observed that the shear strength parameters for geogrid reinforced soil are higher than that reinforced using geotextiles. Moreover, soil reinforced using non-woven geotextile is observed to have higher shear strength parameter than woven type. Hence the utility of geotextiles and geogrids as significant soil reinforcement materials to improve the shear strength parameters of unreinforced soil is highlighted in the present study.

Cost benefit analysis of smart grid: A case study from India

Cost Benefit Analysis (CBA) is an important financial analytical tool which gives an insight to the viability and feasibility of a project. With the growing prominence of the smart grids, various smart grid pilot projects are supported by the Ministry of Power, India. These projects should be evaluated by performing the CBA. The profitability indicators used to evaluate a project is the Net Present Value (NPV), Internal Rate of Return (IRR), Benefits to Cost Ratio (B/C) and the Payback Period (PB). Advanced Metering Infrastructure (AMI) is the backbone of the smart grid and is the largest cost component of the total cost. This paper focuses on the deployment of AMI for two scenarios. In scenario A, smart meters are deployed for all the customers on 1000 feeders and in scenario B, only the customers whose monthly consumption is greater than 200 units are considered for the deployment. This is an extended case study of the India Smart Grid Forum (ISGF). The pecuniary value of the costs and the benefits are considered by consulting various utilities. Only the monetary values of the benefits and the costs are obtained from the base case. In this paper three sub-cases are created in each scenario by choosing different percentages of the loan being taken to check the worst-case feasibility of the project. CBA is performed for both the scenarios. Subsequently, financial analyses done for both the cases are reported and discussed. The results identify the threshold values of loan. The sensitivity analysis show that project is viable and profitable up to reduction of benefit by 20% with no changes in the cost.

Seismic Analysis of Soil Slopes Using FLAC2D and Modified Newmark Approach

Case study on the stability of an actual soil slope, comprising of an embankment with two canal bunds at the top, have been conducted for three different stages of construction. The analyses have been implemented with different foundation soils in different seismic zones. The results of the pseudo-static analyses have been plotted in the form of variation of factor of safety with horizontal seismic acceleration coefficient (kh). Dynamic analyses have been carried out by plotting the response spectrum curves and selecting the 1995 Kobe and 2001 Bhuj earthquake motions as the input ground motions. The results obtained from numerical analyses using finite difference based software FLAC2D have been compared with developed and modified Newmarks (1965) method. Efficiency of FLAC2D to provide reliable numerical solutions for seismic slope stability analyses for practical design has been established.