Austin Dam, Pennsylvania: The Sliding Failure of a Concrete Gravity Dam

Abstract

The Austin Dam, a concrete gravity structure, failed catastrophically on September 30, 1911, less than 2 years after its construction. Several engineering evaluations of the failure have been made since immediately following the disaster. Engineers involved in the construction of the dam recognized early on that the dam failed by sliding on its rock foundation. The dam was constructed on interbedded sedimentary rock, and its foundation was taken to a depth of approximately 4 ft (1.2 m). Although studies of the orientation of the failed blocks of the dam and other site evidence pointed to a sliding failure, no detailed quantitative studies have been done. Recent test pit excavations showed that the critical interface for sliding was a sandstone/shale contact located at a shallow depth below the base of the dam. Stability analyses based on shear-strength tests of the different interfaces of the foundation (concrete/sandstone, sandstone/sandstone, sandstone/ shale, and shale/shale) showed that the dam was safe against a bearing capacity failure, but unsafe with respect to sliding and overturning. The lowest factor of safety of 0.6 corresponded to the sandstone/shale interface, as stated above. The major factors believed to have contributed to the failure include low shear strength of the foundation materials, inadequate provisions for reducing the uplift pressure, and weak concrete. The project stands as the sixth worst dam failure in U.S. history in terms of loss of life, and this case history provides numerous lessons with regard to dam safety.

A Three-Dimensional Analysis Method for the Stability against Deep Sliding of Concrete Dam on Rock Foundation with Mud Layers

“…(1) During the calculation we can take dam of certain length as object according to the specific geological conditions [4], but not dam of certain width, there can`t exists structural surface along the direction of river with high dip in the calculating unit, if so the calculating unit should be divided again.…”

System reliability analysis of foundation stability of gravity dams considering anisotropic seepage and multiple sliding surfaces

“…According to ICOLD (1974), foundation deficiencies are one of the main causes of failure of gravity dams. For high gravity dams built on rock foundations with discontinuities, such as faults, fissures and joints, the dam monoliths may slide along potential sliding surfaces composed of discontinuities in the foundation together with part of the foundation rock (Martt et al, 2005). The foundation stability is of great concern considering the catastrophic consequences induced by failure of high gravity dams on complicated rock foundations (Petaccia et al, 2016).…”

Research on development characteristics and parameter evaluation of the shear zone in the near-horizontal bedded rock mass

“…Interlayer shear zone is one of the most serious engineering geological problems in these conditions. There have been dozens of dam failures (Martt et al 2005;Alonso et al 2010), such as S. Francis and Austin gravity dam in the USA, Tigra Dam in India, and Vaiont landslide in Italy. Therefore, it is the premise and foundation that analyze and evaluate the stability of dam for fully understanding rock mass engineering geological characteristics of dam foundation, mainly including mechanical parameters of rock mass, weathering degree of rock mass, permeability of rock mass, and spatial distribution of weak zone.…”