IMPACT OF PERMEABILITY AND SURFACE CRACKS ON SOIL SLOPES

Abstract

The issue of slope stability is a core concern to geotechnical engineers. Traditional methods of slope analysis have potentially ignored the effects of surface cracks and vegetation. It is also known that higher seasonal rainfall and seepage through surface crack are closely associated with slope failure. In this study two different rainfall intensities are analysed for rainfall induced surface cracked slope failures. Surface cracks can change an existing seepage pattern and increase the soil moisture content into deeper layers at wet season. Therefore, a surface crack is likely to decrease the stability of the soil and increases the tendency of a slope to fail. For slopes with such fractures a parametric study was carried out to investigate the influence of different depths of cracks (10m, 20m, 30m & 40m) at the upper surface and slope surface at different distances from the crest (5m to 35m). The research also analysed the changes of seepage patterns, pore water pressure changes and slope failure surfaces locations due to the surface crack. The analysis was conducted using the computer modelling programs SEEP/ W and SLOPE/ W to model these combined effects with the seepage forces computed within SEEP/W exported to SLOPE/W for slope factor of safety analysis.The influences of vegetation effects on soil slopes are generally classified as two types they are hydrological and mechanical effects. The mechanical effects of the vegetation root are responsible for the physical interaction with the soil structure. The parametric study incorporated the vegetation root mechanical effects in slope stability. Root cohesion has been incorporated with Mohr-Coulomb soil model and it has been applied to the slope stability analysis software tool SLOPE/W to investigate the influence on marginal slopes factor of safety.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Pauleen Lane (Supervisor)