Session: 02-01-01 Project Design - Part I

Paper Number: 87107

87107 - Effectiveness of Subsurface Drainage for Mitigation of Landslides Affecting Pipelines 

Landslide can pose a threat to the integrity of new and existing pipelines if they are not mitigated. Improved subsurface drainage of groundwater is the most widely used stabilization strategy for mitigation of landslides affecting pipelines since requiring minimal design and costs and can improve the overall stability. The appropriate design and implementation of this approach could lower the ground water table within the landslide as a primary factor triggering landslide movement by reducing the driving force and increasing the shear strength or resisting force within the landslide mass. Thus, the subsurface drains are conventionally employed in mitigation of most landslides that may threaten pipelines either as a single remedial or for use in conjunction with other measures.
This paper will discuss the role and efficacy of different subsurface drainage system such as curtain drain, subdrain, trench drain in various site conditions and will present design considerations for selection of different subsurface drainage system.  This paper will also present the effectiveness of subsurface drainage systems for improving the slope stabilization in various site conditions.  Site conditions such as location of right of way compared with the boundary of landslide, geometry of landslide, geological condition, ground water level, ground water gradient and its direction, and geometry of subsurface drain system will be discussed for effective design of subsurface drainage system. This paper will explore pre-design investigation consideration for design of such drainage system. The results of a series of two-dimensional limit equilibrium and seepage analyses will be presented to evaluate the effectiveness of different drainage in various site condition. The results of analyses indicated a proper design and implementation of subsurface drainage systems is dependent on the geological condition of the site, ground water level and location of the subsurface drain compared with the boundary of the landslide, and geometry of the site for proper discharge of collected groundwater. A properly-designed subsurface drainage system can improve the stability of landslide by increase the factor of safety of landslide, while deficient drainage system cannot be affective or even adversely affect the overall stability of the landslide and pipeline integrity.

Presenting Author: Mohammad Rashidi Geosyntec

Presenting Author Biography: Dr. Rashidi is a geotechnical engineer with nine years of experience in various aspects of geotechnical engineering, specializing in the design of geohazard mitigation plan; analysis and design of ground improvement systems such as deep soil mixing, shallow and deep foundations, stabilization of subgrade and base soils, and geogrid-reinforced system for a number of oil and gas pipeline projects. He extensively worked on the numerical analysis of large geo-structures including cofferdams, retaining walls, earth and rockfill dams. Dr. Rashidi has also expertise in the design of soil nails systems, slope stability analysis, design of waterproofing and dewatering systems, development and execution of field and laboratory testing programs for development of rock and soil parameters, and design of flexible and rigid pavement foundations. He has published nineteen peer-reviewed papers as a first author in the most prestigious journals and conference proceedings.