Quick Undrained Shear Strength Test comparison on London Clay

Abstract

Shear strength of a soil is required to overcome problems involving earth pressure, bearing capacity of foundation, landslide, subsidence and the stability of slopes in cut or fills. London clay has a complex natural formation which also contributed problems to the researchers, developer’s engineers and contractors in construction and infrastructural development. most researchers conducted experiment and investigation on shear strength of London clay using direct shear box test and simple shear test but only a few discovered the behaviour of it under quick undrained shear condition. The aim of this paper is to determine unconsolidated undrained shear strength properties of a remoulded London clay specimen for comparison purposes. four different soil specimen were obtained from four trial test boreholes at a depth in the range of 14-23m. Macroscale analysis was carried out including Atterberg limits, moisture content test and determination of shear strength parameters through triaxial compression testing. The result revealed that the natural water content, liquid limit and plastic limit has a mean value of 25.52, 69.5 and 23.81%. However, the sample has an apparent cohesion and internal angle of resistance are in the range of 149.3- 763.92kN/m² and 0 – 16^oc respectively. The average apparent cohesion and the plasticity values of the sample are very high and it is an indication that a good correlation exists between the two values. There is no increment in moisture content level throughout the test, this is an indication that the specimen was properly sealed with the membrane during the testing. The triaxial compression results have shown that the stress failure envelopes are not horizontal, and for this reason the average cohesion is taken with a zero angle of shearing resistance. Correlation between the apparent cohesion and that of the liquid limit and moisture content was carried out and the results have yielded a very good correlation except the one from borehole depth 17 m, this could probably be attributed to the lithology of the London clay.