STRUCTURAL SAFETY ASSESSMENT OF MULLARDOCH DAM USING AN ADVANCED NONLINEAR FINITE ELEMENT ANALYSIS TECHNIQUE

Mullardoch Dam is a concrete gravity dam constructed in 1951 and situated in Glen Cannich, west of Inverness, Scotland. While a series of comprehensive analytical studies has been undertaken in the past in order to investigate the performance of the dam under probable maximum flood (PMF), thermal and dynamic load scenarios, none has considered the effects of material nonlinearity. This paper examines the nonlinear response of the dam under PMF conditions utilizing a plane strain finite element model of the dam body and its foundation. The study considers the possibility of fracturing of concrete, rock and their interface, as well as the propagation of water within discrete cracks. Uncertainties in material properties are taken into account by means of a parametric study of the principal variables associated with nonlinear material behaviour. The effect of variation in concrete mass, rock mass, concrete-to-concrete interface and concrete-to-rock interface material properties is investigated using lower bound, best and upper bound estimates. The finite element model consists of eight-node quadrilateral and three-node isoparametric interface elements. The concrete and foundation rock are associated with individual nonlinear materials based on the total-strain rotating crack model. Bi-material and construction joint interfaces are associated with a discrete cohesive crack model. The results indicate that the effect of material nonlinearity plays a significant role in determining the stress distribution within the dam and its foundation, and therefore in identifying the extent of cracking under quasi-static loading. In particular, it is revealed that while cracking is initiated at the heel area and subsequently extends into the foundation rock following a curved or near-vertical trajectory, the dam is capable of withstanding the imposed loading scenario without undergoing structural collapse.