| description abstract | In the past several years, the high frequency of cave-in failures of urban roadways has posed a serious threat to the safety of traffic, pedestrians, and existing structures and facilities in China, and they have often led to fatalities, injuries, and significant economic losses. First, this study collates 379 cases to characterize roadway cave-in failures. Then the major causes associated with these events are classified, which includes damage and defects on preexisting underground structures and facilities, washout and erosion of roadway subgrade by seepage water, underground construction, loose subgrade, excessive lateral wall movement and through-wall leaking of deep excavations adjacent to roadways, and rapid decline in water table levels. Then four enormously influential failure cases are described as typical examples. Finally, the primary characteristics of the cave-in failures are discussed, including their temporal and spatial distributions, sizes, and morphologies, as well as the number of casualties and injuries involved. This review concludes that it is of paramount importance to inspect healthy conditions of aging underground structures and pipelines and to adopt or develop reliable measures to check unseen loose zones, voids, and cavities underneath urban roadways, in particular those adjacent to construction sites, with erodible subsurface conditions, or frequently subject to disturbing forces (seepage flow and vibration). | |
