ABSTRACT:

This paper presents the results of a study on evaluation of liquefaction potential of ground along the alignment of power channel of a hydroelectric power project in the Uttar Pradesh State of India. Results of field Standard Penetration Test (SPT) and laboratory Cyclic Simple Shear Tests were used in the analysis for determining cyclic strength of the soil. SeedÕs Simplified Procedure was employed for evaluation of liquefaction potential. Based on the analysis carried out for different magnitudes of earthquake, it was concluded that the top soil is susceptible to liquefaction due to an earthquake of magnitude of 4.5 or more on Richter scale occurring at a distance of 25 km.

INTRODUCTION

Tanakpur Hydroelectric Project is a run-of-the-river scheme across river Sarda and is located upstream of Banbassa barrage in Uttar Pradesh State of India. The 475m long barrage is located at Tanakpur. A 6387m long power channel takes off on the right bank of Sarda River. Soil investigations carried out for the power channel indicated Standard Penetration Test (SPT) values in the range of 3 to 5 up to a depth of about 3m in a predominantly fine silty sand. This type of soil was suspected to liquefy under earthquakes. A study was, therefore, undertaken to evaluate liquefaction potential of the soil to ascertain the threshold level of earthquake that could trigger liquefaction.

FIELD INVESTIGATION DATA

Field test data supplied by the project was in the form of SPT values obtained by conducting standard penetration tests at six locations on the natural ground along the alignment of power channel. The tests were carried out to different depths at each location. The maximum depth of investigations was 3.7m. The topsoil was found to be weak and the thickness of weak soil varied between 2.2m to 3.7m.

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