The effect of loading duration on consolidation parameters of some tropical soils

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University of Dar es Salaam
Standard consolidation test (BS 1733-5:1990, ASTM D 2435-03) requires that the specimen is stepwise loaded to the predetermined maximum stress, each increment step taking 24 hours. Some of the common tropical soils are relatively very permeable and therefore need shorter time to complete primary consolidation. For such soils a shorter oedometer loading time has been investigated, which may improve the laboratory efficiency. Three types of cohesive soils, namely CLAY of high plasticity (CH) from Mbezi Beach Jogoo, clayey SAND of intermediate plasticity (SCI) from Kunduchi and CLAY of very high plasticity (CV) from UDSM (CoET – near Block P) were sampled, characterized and subjected to different loading schemes in the oedometer test. 6, 12 and 24 hourly loading schemes were adopted for all three samples in one dimensional incremental consolidation test. The square root of time method was used to estimate time for completion of 90% and 100% primary consolidation.For all three soil samples, variation of coefficient of volume compressibility, stiffness modulus, compression index swelling index and recompression index with loading time were determined.Estimated time for 100% primary consolidation was less than 9, 2 and 16 hours for the CH, SCI and CV soil samples respectively. Laboratory determined pre-consolidation pressures were found to decrease with increasing loading duration.A loading scheme of 12 hourly for CH soil, 6 hourly for SCI soil, and 24 hourly for CV soil has been recommended for laboratory testing thus serving time when CH, and SCI or similar soils are to be tested for consolidation.
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effect of loading duration, Consolidation parameters, Tropical soils
Mustafa, F(2012), The effect of loading duration on consolidation parameters of some tropical soils, master dissertation, University of Dar es Salaam (available at)