Coupled tank model and flow model for slope seepage flow analysis

Of all the required data on analysis of slope stability, probably pore pressure along the potential sliding planes is the most sensitive variable. The pore pressure changes correspond to water table fluctuation that is mainly associated with two sources of recharge; infiltration and underflow. Seepage flow analysis carried out to estimate slope stability requires an accurate representation both those sources. However, it is common that numerical modeling is performed with underestimated underflow recharge by setting boundary conditions at up and down gradient as fixed head. This simple assumption may leads to inaccurate estimation results particularly for slope with open hydrogeological system. Therefore, a more realistic approach is to set time-dependent pore pressure boundary conditions on both down-and-up gradients. Since the prediction is mainly analyzed based on rainfall pulse, responses of these sides to the rainfall intensity are estimated by applying Tank Model. As a result, coupling of the tank model and numerical flow model can represent the changes of pore pressure due to the rainfall more accurately. This proposed method was implemented for a field problem of slope at Mizusawa-Yamagata, Japan by using a set of observed data in the past occurrence.