ABSTRACT
Pipelines across subaqueous slopes, even gently inclined, may be affected by the occurrence of landslides: in some cases these latter can cause even the interruption of the lifeline itself. Therefore, the design of buried pipelines should require the analysis of the soil-structure interaction phenomenon, even when the soil flows along the slope. For this purpose a small scale pipeline model was built in the laboratory, and a series of numerical simulations by means of distinct elements was performed.
The experimental set-up consists of a box which is filled with sand and water. A uniform vertical water flow is imposed in order to reproduce the occurrence of liquefaction. The effects of a landslide are simulated by horizontally pulling a rigid tube in the direction perpendicular to its axis (plane strain conditions). The drag force is measured, as well as the deformation pattern is qualitatively observed. Several experiments were performed, in which the diameter and the depth of the tube were changed. The experimental results show that the drag force is mainly a function of tube depth, depth-diameter ratio, and seepage conditions.
The results of the numerical simulations (PFC code) match the experiments very closely, if a proper calibration of the micromechanical parameters, which will be discussed in the text, is made. In addition, DEM simulations allow to interpret from a micromechanical point of view some aspects of the experiments, providing useful information about the failure mechanisms and the force transfer within the soil.
