In situ evaluation of K0 in eastern Canada clays

An approximate value of the horizontal effective stress in an overconsolidated clay deposit is often determined from an estimate of the effective stress ratio, K 0 , using the equation . It is also generally considered that the α parameter is approximately equal to sin . For evaluating K 0 in sensitive clays of eastern Canada, a testing program has been initiated on three different sites representing a large range of overconsolidation ratios. Three different in situ devices were used: the Cambridge self-boring pressuremeter, the flat dilatometer, and hydraulic fracturing. The results show that the different techniques give essentially the same K 0 values. They also give K 0 values larger than those expected, with an α parameter typically between 0.75 and 1.15. Key words : clay, dilatometer, horizontal stress, hydraulic fracturing, in situ tests, self-boring pressuremeter.