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United States Department of Agriculture

Agricultural Research Service

Title: Pore Pressure and Bank Stability: the Influence of Matric Suction

Authors
item Simon, Andrew
item Curini, Andrea - UNIVERSITY OF MISSISSIPPI

Submitted to: American Society of Civil Engineers Hydraulic Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 1, 1998
Publication Date: N/A

Interpretive Summary: Erosion of sediment from streambanks is a critical problem in many agricultural watersheds. Research conducted along Goodwin Creek, northern Mississippi, has disclosed the importance of suction in the portion of streambanks that lie above the water table as a means of resisting bank failures. This suction can make up almost all of the shearing resistance of an unsaturated bank during summer months. Infiltration of water from rainfall events causes a loss of suction, reduced bank strength, and increases the likelihood of bank failures. This occurs most commonly after successive, moderate rainfall events when sufficient water has been able to drain into the bank. An improved method of predicting the timing and amount of bank collapse is also presented.

Technical Abstract: Recent field research has disclosed that the loss of matric suction (negative pore pressures) from infiltrating precipitation may be as significant as the development of excess pore pressures in contributing to mass bank instability. Research was conducted in cohesive bank materials along Goodwin Creek, northern Mississippi. Apparent cohesion and friction angle were measured in situ with a borehole shear tester. Matric suction was measured continuously, in situ with a series of pressure-transducer tensiometers. Bank failures are associated with periods following successive, moderate rainfall events which permit sufficient time for water to drain into the bank and reduce matric suction and generate positive pore-water pressures in areas of low permeability. A bank-failure algorithm is used to investigate the role of matric suction for layered river banks.

Last Modified: 12/22/2014
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