Underwater Explosion Resistance Performance of an Old Gravity Dam without Good Longitudinal-Joint Connection Integrity: Coupled Acoustic-Structural Analysis.

A gravity dam monolith bounded by the transverse contraction joints on both sides is usually recognized as an independent element in various dynamic analyses. However, in most cases a gravity dam monolith is actually subdivided by longitudinal joints for mass concrete construction requirements. Previous studies of gravity dams subjected to underwater explosion (UNDEX) shock loadings have not dealt with the longitudinal-joint issue in much detail. In this work, a numerical simulation of the dynamic response of an old gravity dam without good longitudinal-joint connection integrity in an UNDEX event is performed. The coupled acoustic-structural analysis procedure with ABAQUS/Explicit is employed. The reliability of the procedure is validated by numerical simulations of two UNDEX impact tests in the literature. Nine calculation cases are considered to compare different responses of the dam with different connection states between monolith sections and underwater detonation depths. The results of this numerical investigation show that the longitudinal joints play an important role in the UNDEX response of the dam. The longitudinal joints greatly weaken the flexural rigidity of the dam and make the dam damaged in a piecemeal manner. This study adds to the rapidly expanding field of the UNDEX resistance performance evaluation of gravity dams by accounting more for the longitudinal-joint issue. The antiterrorism situation worldwide is experiencing constant changes, making the world continually face multiple unstable factors. Dams are easy attack targets for their enormous social and economic values. Among various dam types, gravity dams are commonly recognized to have the best blast resistance performance owing to their monumental body sizes. A gravity dam is routinely divided into several monoliths by transverse joints. Each monolith is then subdivided by longitudinal joints for mass concrete construction requirements. After the completion of a dam monolith, the longitudinal joints should be grouted to ensure the integrity of the monolith. For some dams serving several decades, their longitudinal-joint connection integrity might deteriorate. Such structural integrity losses should lead to blast resistance performance degradation. With this in mind, the authors carried out a series of numerical simulations of an old gravity dam when it is experiencing underwater explosion (UNDEX) shock loadings. Nine cases are considered concerning different longitudinal-joint connection states and UNDEX scenarios. This work clarifies the mechanism that the longitudinal-joint connection failure deteriorates the UNDEX resistance performance of the dam. Great efforts on reinforcing old dams through enhancing their longitudinal-joint connection integrity are thus needed to ensure their adequate blast resistance performance. [ABSTRACT FROM AUTHOR]