Criteria of acceptance for constant rate of strain consolidation test for cohesive soil

Abstract

Constant rate of strain (CRS) consolidation test is a new method of consolidation testing in Malaysia. Although it had been widely used as an alternative for standard consolidation test in other countries such as Sweden and the USA, there is still no standard equipment for it. The selection of the suitable strain rate for the CRS test is still a major hurdle for the geotechnical engineers. The CRS consolidation test has some advantages over the standard consolidation test where the time needed for the test is reduced from two weeks to few hours and the ability to apply high effective pressure at larger sample size. Various guidelines and criteria of acceptance for the CRS consolidation test had been introduced by many researchers. The aim of this research is to establish new criteria of acceptance for the CRS consolidation test. A new developed CRS equipment has been designed and named Rapid Consolidation Equipment (RACE). The equipment was developed using the concept of continuous consolidation test procedure. The criteria of acceptance for the CRS test were based on the normalized strain rate, ß introduced by Lee (1981) and the ratio of excess pore pressure to applied pressure, (ua/ sv ). It was also established that the maximum ß to achieve acceptable data is 0.1. The research showed that the minimum value for the ß and ua/ sv are 0.005 and 0.01 respectively. Another criterion of acceptance for the CRS test which takes into account the clay fraction (CF) effects was also introduced. The clay fraction is used to modify the normalized strain rate ß, into ß/CF. Results show that for soil with clay fraction more than 50%, the maximum ß / CF is 0.001. The maximum ß / CF for soil with CF lower than 50% is 0.008.