Development of an Automated Cyclic Direct Shear Test Apparatus for Determining Strength Parameters for Landslide Slope Stability Analysis and Optimization of Test Method

Abstract

The suitability of strength parameters for stability calculation is very much important in evaluating landslide slope stability. A new cyclic direct shear apparatus which can be brought in the field was designed for the purpose of quick and rational determination of strength parameters. The features of this apparatus are: 1) the apparatus can be brought in the field due to its compactness and light weight, 2) cyclic shear test with any cycle and amount of shear displacement can be performed automatically, 3) since normal force is controlled by high accuracy digital servo motor system, both constant pressure test and constant volume test can easily be performed, and 4) friction force between sliding surface of the specimen and the surfaces of the upper and lower boxes can be measured by the load cells installed inside the shear boxes.Residual strength parameters can be obtained from the cyclic shear test with this apparatus and using intact specimen sampled from the site. Strength parameters corresponding to fully softened state can also be obtained by the specimen which is made by fully remolding the specimen after cyclic shear test and preconsolidating it from the state of slurry. The two sets of strength parameters (cr, φr) for residual state and (cs, φs) for fully softened state, respectively obtained from the tests mentioned above, can be used for the method of determination of design strength parameters proposed by the present authors.Case studies for two sites of landslide proved the suitability of the strength parameters determined from the method based on the experimental data obtained by new designed cyclic direct shear test apparatus.