Comparison of Conventional Incremental Load and Constant Rate of Strain Consolidation Test Results for Red Clay of Addis Ababa
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Date
2016-11
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Addis Ababa University
Abstract
The conventional incremental loading consolidation tests are carried out for determining
consolidation parameters. Due to the longer duration taken for the conventional incremental
loading (CIL) consolidation tests, nowadays constant rate of strain consolidation (CRSC) tests
are also used to study the consolidation behavior of clayey soils. The results of conventional
incremental loading (CIL) consolidation tests and constant rate of strain consolidation (CRSC)
tests for undisturbed red clay soil samples from 3 boreholes in Addis Ababa, Ethiopia, have
been presented, compared and discussed. The main parameters investigated are
compression index (Cc), pre-consolidation pressure (σ'p) and coefficient of consolidation (Cv).
For undisturbed red clay of Addis Ababa, e – log σ'v curve of CRSC test is more non-linear than
that of CIL test. Considering the slope (Cc) of e – log σ'v curve just after pre-consolidation
pressure (σ'ρ), CRSC test resulted in a larger Cc and σ'p value than CIL test for Kolfe and Rufa’el
soil samples. But for Addisu Gebeya CRSC test, values are smaller than CIL test. To get
comparable result the strain rate should be increased. The values of the coefficient of
consolidation (Cv) from CIL and CRSC tests are comparable after the pre-consolidation stress.
The excess pore pressures produced during the CRSC test show condition of CRSC test in
which Cv values are acceptable and compatible with conventional consolidation test. The
steady state condition is achieved when the Cv values from drained and undrained face of
CRSC test converge with the Cv value from conventional (CIL) consolidation test. The time
required to complete a CIL consolidation test in this study was 12 days. Whereas CRSC tests
required an average of 1.8 days, consider only loading stage.
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Geotechnical Engineering