IMPROVING THE ACCURACY OF KENNEY AND LAU METHOD IN ORDER TO ASSESS THE INTERNAL STABILITY OF GRANULAR SOILS

Internal instability normally occurs in widely graded or gap graded soils. To be more specific, it may occur in soils that have a bimodal structure (i.e. the soil has two components, namely, coarse fraction and loose fine fraction). Internal instability occurs when the finer fraction particles can be washed out if their size is less than the size of the constrictions among the coarse fraction particles. A commonly used approach to evaluating the potential for internal instability in soils is that of Kenney and Lau. This method is used to assess the internal stability of cohesionless soils based on the shape of their GSD curves. The main objective of this paper is to propose a modification on Kenney and Lau method to increase the accuracy of this method using the critical particle sizes between the groups of the soils. Major type groups of the soils include; gravel (>4.75mm), sand (0.075-4.75mm) and fines (<0.075mm). The proposed modification was verified with a large number of experimental tests.