Measurement of Suction in a Marine Clay as an Indicator of Sample Disturbance

This paper describes a test program that investigated the potential of residual porewater pressure, or suction, to be a quick and nondestructive measure of sample disturbance. A portable 35 mm diameter suction probe, consisting of a high air-entry porous ceramic stone and pressure transducer capable of direct suction measurements on soil samples, was developed for this study. The suction probe was used at a test site located in Newbury, Massachusetts where a layer of low to medium plasticity Boston Blue Clay (BBC) exists. Six Sherbrooke block samples and several 76 mm split spoon samples were collected. Consolidation tests were conducted on all samples to assess sample quality based on volumetric strain methods. The high quality Sherbrooke block samples had much higher suctions than the poor quality split spoon samples. The results suggest that the suction probe could be a practical tool for making assessments of sample quality in the field immediately after sample collection and during selection for laboratory consolidation and strength testing.