ANALYSIS OF GEOGRID REINFORCED POND ASH EMBANKMENT USING FINITE ELEMENT METHOD

Abstract

The disposal of enormous quantity of pond ash from thermal power plants has been a major environmental concern over a period of last few decades that encourages civil engineers worldwide to use pond ash extensively to protect the environment and save natural resources. An infrastructure project such as reclamation, highways, water reservoirs, railways etc, require earth material in very large quantity as there is a shortage of good soil in most urban areas. In such situations construction of pond ash embankments with steep slope is worth considering, as the pond ash is freely available material in vicinity of a thermal power plant. In the present work an attempt has been made to use pond ash for construction of road embankment. This will not only solve the problems associated with the disposal of pond ash but will also help to conserve the precious top soil and land required for growing food as well as protecting environmental pollution. A parametric study has been carried out to investigate the effect of inclination of slope, vertical spacing of geogrid reinforcement on reinforced pond ash embankment, and effect of providing pond ash – lime mixed layer on top and side slopes of unreinforced pond ash embankment. The Pond Ash sample was collected from the ash pond site of Rajghat thermal power station, Delhi, soil was collected from DTU campus, Delhi and the lime was procured from the open market in the form of quick lime. This lime was then mixed with pond ash, by weight (= 9%) (Gupta et al, 2013).Further, in the present work an experimental program was carried out to characterize the materials and strength tests were performed to study the behavior of pond ash mixed with lime; the results shows that in the presence of moisture, pond ash chemically reacts with lime at ordinary temperature and forms cementations material which is attributed to the increase in strength of pond ash. Numerical analysis was performed using the FEM based software PHASE2 (Rocscience). Results divulge that use of full length of geogrid covering whole width of embankment increases the critical strength reduction factor (SRF) of embankment at steeper slope inclination. Also, the application of either geogrids layers or pond ash-lime mix layer, results in safer designs in comparison to unreinforced pond ash embankment. In this research a substantial number of parameters were considered to study their effects on the stability of embankment which may prove useful from execution of actual prototypes.