The Stress-Strain Behavior Of Sand-Bentonite Mixtures

Although many researchers agree that filter cake properties influence the performance of completed construction, its behavior is not well understood. Specifically, there is a lack of information about the stress-strain behavior of filter cake. This thesis deals with the stress-strain behavior of sand-bentonite mixture, which consists of the same material as filter cake.Samples are made first by mixing dry bentonite with sand in different proportions, by weight. The percentages of bentonite in the mixture are 10%, 15% and 20% respectively. And then a little water was added to the mixture (about 3% by weight) and mixed thoroughly until the mixture is uniform. The samples are prepared in five layers by tamping in a forming mould. Pure sand and bentonite samples have also been made for comparison.The equipments employed to carry out the tests are a conventional triaxial cell and oedometer. The experimental program consists of five groups of different samples, of which each group has four samples. Both consolidated drained and consolidated undrained triaxial compression tests, isotropic consolidation and 1-D consolidation tests are performed. The stress-strain curves are described in detail. Results of the shear strength parameters indicate that there is no significant difference in strength between the different samples of sand-bentonite mixtures. Whereas the strength of sand-bentonite mixtures is lower than that of sand.The test results are analyzed by FEM program of Modified Cam-Clay model. Results show that Modified Cam-Clay model cannot predict the stress-strain behavior of sand-bentonite mixtures well; rather it can relatively predict the stress-strain behavior of bentonite. Finally, some remarks are made on the behavior of sand-bentonite mixtures.