STRESS-STRAIN BEHAVIOR OF RECONSTITUTED ILLITIC CLAY AT DIFFERENT TEMPERATURES

Tests on specimens of reconstituted illitic clay have examined the inf luence of temperature on the mechanical behaviour of clay soils. The p rogram involved consolidation to effective confining pressures up to 1 .5 MPa, heating to 100 degrees C, and tests on normally consolidated a nd overconsolidated specimens with OCR=2. The tests included isotropic consolidation, undrained triaxial compression with pore water pressur e measurement, drained tests along controlled stress paths to investig ate yielding behaviour, and undrained tests which involved heating and measurement of the resulting induced pore water pressures. The large strain strength envelope is independent of temperature. However, peak undrained strengths increase with temperature because smaller pore wat er pressures are generated during shearing. An important contribution from the study is a series of results for the yielding of illitic clay at three different temperatures. For the first time, there is clear e vidence of yield loci decreasing in size with increasing temperature. An associated how rule can be assumed without serious error. The resul ts contribute to the confirmation of a thermal elastic-plastic soil mo del developed by the authors from cam clay following the addition of a small number of extra assumptions. Depending on the initial stress st ate, heating under undrained conditions may produce shear failure. (C) 1997 Elsevier Science B.V.