DefinePK

Abstract

In the modern world of science and technology, rapid growth has escalated the need for specific and appropriate techniques so that construction activities ensure comprehensive solutions to each and every problem faced by the construction industry. It is in this respect a study of suffusion has been taken up. A study of collapse of dams, erosion of embankments and damages to buildings due to earthquakes lead us to conclude that suffusion has played a major role in all the above setbacks. Suffusion occurs due to voids and uneven particles in soils leading to seepage force causing damages. This requires analysis of geometric criteria of the soil and hydraulics that causes suffusion. This project attempts at assessment of susceptibility to suffusion through geometric criteria. To have deeper insight and finer evaluation, five different soil samples were analyzed using different methodologies proposed by nine authors. While six methodologies have confirmed that all the samples are suffusive, three methodologies have shown variations and out of these three, Burenkova’s methodology is widely used for assessment. Unfortunately this methodology was found to give unsafe results. Wan and Fell (2008) refined Burenkova method and even this refined method was found to give unsafe results. Therefore attempts have been made to refine Burenkova method. Taking up 101 gradations from other studies and 5 from current study, a broader analysis has been done and improved limits have been suggested. Different models have been proposed for widely-graded and gap-graded soils. New models have been proposed based on two ideas. The first idea is that the d90/d60 value should increase as d90/d15 value increases. Second idea is that at lower values of d90/d15 the stable zone will be small and as the d90/d15 increases stable zone also increases. Among the five models proposed for widely-graded soils, model 2 is found to be most appropriate and among four models proposed for gap-graded soils, model 1 is found to be most appropriate. Along with refinement of Burenkova’s method, the authors also propose a new better method for finding susceptibility of soils to suffusion. The authors use division between D and d5 for the same. D represents higher diameter at gap location for gap graded soils or higher diameter corresponding to highest value of division between two successive diameters with a difference of 10% (first division alone be for a difference of 5%, between d10 and d5). d5 is the representative of fine grains while D is the representative of voids. D/d5 value less than 4 corresponds to stable soils while greater than 6 corresponds to unstable soils and between 4 to 6 indicates transition zone.