Vol. 5 Issue 1
Year: 2015
Issue: Dec-Feb
Title:Formulation of Transient Uplift Pressure in Cracks of Concrete Gravity Dams
Author Name:K.K.Pandey, N.Kumar and V.Kumar
Synopsis:
Safety guidelines recommend the presence or absence of an assumed static uplift pressure in cracks at damfoundation interface during seismic activity. In recent past, some research work has been done to develop a mathematical model for transient uplift pressure in smooth walled cracks under laminar flow conditions. In this paper, a mathematical model for transient uplift pressures in real cracks under both laminar and turbulent flow regimes are developed. One dimensional continuity and momentum equations have been coupled to derive the governing integral equations of pressure as a function of crack wall motion history and flow regimes (i.e. laminar/turbulent). These equations are supplemented with required number of boundary conditions based on the understanding of hydraulic phenomenon described in the literatures. Model is used to solve the transient uplift pressure in wedge shaped crack of constant length and is validated using the experimental data from literature. A difference (less than 5%)between computed and measured value of uplift pressure occurs at beginning and end of the opening-closing cycle of the crack in comparison to other points of time. These differences may be attributed to violation of some assumptions used in the problem formulation (e.g. vapour pressure at point of saturation may not be zero and two-phase flow may occur in unsaturated portion of the crack) or the possibility of cavitation in unsaturated portion of the crack. However, overall computed pressure variation obtained using present formulations are in good agreement with experimental data from the literature.
Year: 2015
Issue: Dec-Feb
Title:Formulation of Transient Uplift Pressure in Cracks of Concrete Gravity Dams
Author Name:K.K.Pandey, N.Kumar and V.Kumar
Synopsis:
Safety guidelines recommend the presence or absence of an assumed static uplift pressure in cracks at damfoundation interface during seismic activity. In recent past, some research work has been done to develop a mathematical model for transient uplift pressure in smooth walled cracks under laminar flow conditions. In this paper, a mathematical model for transient uplift pressures in real cracks under both laminar and turbulent flow regimes are developed. One dimensional continuity and momentum equations have been coupled to derive the governing integral equations of pressure as a function of crack wall motion history and flow regimes (i.e. laminar/turbulent). These equations are supplemented with required number of boundary conditions based on the understanding of hydraulic phenomenon described in the literatures. Model is used to solve the transient uplift pressure in wedge shaped crack of constant length and is validated using the experimental data from literature. A difference (less than 5%)between computed and measured value of uplift pressure occurs at beginning and end of the opening-closing cycle of the crack in comparison to other points of time. These differences may be attributed to violation of some assumptions used in the problem formulation (e.g. vapour pressure at point of saturation may not be zero and two-phase flow may occur in unsaturated portion of the crack) or the possibility of cavitation in unsaturated portion of the crack. However, overall computed pressure variation obtained using present formulations are in good agreement with experimental data from the literature.
No comments:
Post a Comment