Xiaokun Hou & Sai K. Vanapalli

Numerical analysis of water migration in an unsaturated slope subjected to different irrigation conditions

Xiaokun Hou & Sai K. Vanapalli Department of Civil Engineering, University of Ottawa 161 Louis-Pasteur St., Ottawa, Canada Tonglu Li Department of Geological Engineering, Chang’an University Xi’an, Shaanxi, China

ABSTRACT

The stability of slopes in collapsible soils is significantly influenced by both the infiltration of water due to natural rainfall conditions and manmade irrigation activities. Numerous research studies have been conducted to better understand the influence of rainfall activity in collapsible soils from field tests, laboratory column tests and numerical analyses tests. These studies suggest that: (i) the depth of the wetting front is not significantly influenced due to natural rainfall conditions; (ii) several factors that influence the rainfall water infiltration include the temperature, rainfall intensity, saturated coefficient of permeability, the water storage capacity of soil; (iii) a low intensity rainfall that extends for a longer duration is more dangerous for a slope than a high intensity rainfall of a shorter duration. However, recent studies suggest that the groundwater table rise associated with several years of continuous irrigation activities has a significant influence on the stability of slopes in comparison to water infiltration associated with natural rainfalls. There are limited studies in the literature in this direction.

The objective of the present study is directed to estimate the suction profile changes for an unsaturated slope with different gradients with respect to time for different irrigation activities using Geo-studio (SEEP/W). The focus of the paper is to highlight the influence of several years of irrigation activities on the groundwater table and its influence on the hydraulic equilibrium conditions and slope stability failures. In addition, various factors influencing the water migration such as the slope gradient, different soil properties (Ks, SWCC) on the rise of groundwater table are investigated. The summarized study is valuable for the regulators who can use this technique to provide guidelines to alleviate slope stability problems for the owners who resort to irrigation activities for agricultural purposes in collapsible soils deposits.

Key words: collapsible soil, landslides, irrigation, suction profile, groundwater table