Comparison Of Conventional Incremental Load And Constant Rate Of Strain Consolidation Test Results For Red Clay Of Addis Ababa

The conventional incremental loading consolidation tests are carried out for determiningrnconsolidation parameters. Due to the longer duration taken for the conventional incrementalrnloading (CIL) consolidation tests, nowadays constant rate of strain consolidation (CRSC) testsrnare also used to study the consolidation behavior of clayey soils. The results of conventionalrnincremental loading (CIL) consolidation tests and constant rate of strain consolidation (CRSC)rntests for undisturbed red clay soil samples from 3 boreholes in Addis Ababa, Ethiopia, havernbeen presented, compared and discussed. The main parameters investigated arerncompression index (Cc), pre-consolidation pressure (σ'p) and coefficient of consolidation (Cv).rnFor undisturbed red clay of Addis Ababa, e – log σ'v curve of CRSC test is more non-linear thanrnthat of CIL test. Considering the slope (Cc) of e – log σ'v curve just after pre-consolidationrnpressure (σ'ρ), CRSC test resulted in a larger Cc and σ'p value than CIL test for Kolfe and Rufa’elrnsoil samples. But for Addisu Gebeya CRSC test, values are smaller than CIL test. To getrncomparable result the strain rate should be increased. The values of the coefficient ofrnconsolidation (Cv) from CIL and CRSC tests are comparable after the pre-consolidation stress.rnThe excess pore pressures produced during the CRSC test show condition of CRSC test inrnwhich Cv values are acceptable and compatible with conventional consolidation test. Thernsteady state condition is achieved when the Cv values from drained and undrained face ofrnCRSC test converge with the Cv value from conventional (CIL) consolidation test. The timernrequired to complete a CIL consolidation test in this study was 12 days. Whereas CRSC testsrnrequired an average of 1.8 days, consider only loading stage.

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