Volume 35, Issue 3 (May 2012)
A Comparative Study on the Shear Behavior of an Interlayer Material Based on Laboratory and In Situ Shear Tests
In order to evaluate the overall stability of the underground powerhouse at the future Baihetan hydropower station in China, the shear strength of a weak intercalation soil in the host rock has been investigated via in situ direct shear and laboratory shear tests. A comparative study was performed based on the two test results. It has been observed that both tests show elastic perfect-plastic behavior. A significant heterogeneity of the samples has been identified under both laboratory and field conditions. The samples’ disturbance seems to be a less important factor than the samples’ variability. The size effect has been evidenced by the friction angle obtained in the laboratory on small samples, which is greater than that obtained in the field on larger samples. The clay fraction has been found to be an important factor; its increase reduces the friction angle and increases the cohesion. Without considering some particular data due to the soil heterogeneity, a negligible effect of the initial degree of saturation has been identified. Comparisons between the results of the field tests and those from the laboratory tests show good consistency in terms of the effects of the clay fraction and the initial degree of saturation, indicating a relatively secondary effect of the sample size and variability.