Analysis of geoenvironmental hazards in urban underground space development in Shanghai

Underground space is becoming increasingly more utilized in the fast urbanization process of Shanghai. However, many geoenvironmental hazards, including land subsidence, slip flow, methane gas, piping, and quicksand, are occurring more frequently, as underground space development enters the state of “big, deep, long, fast, and dense.” In this paper, based on our investigation and studies of construction project cases, we analyze the possible factors causing geoenvironmental hazards and propose corresponding measures for their prevention. From the viewpoint of earth system science, the geoenvironmental hazards are caused by anthropogenic factors coupled with natural factors. Shanghai is built over layers of soft soil that were deposited during the Holocene. The paleogeographical environment of the Holocene produced soft soil with high water content, large void ratio, high sensitivity, thixotropy, low shear strength, and high compressibility; these characteristics lead to a geoenvironment that can be easily disturbed by underground engineering construction. To achieve sustainable development of underground space, a series of prevention and control measures are presented, especially awareness of the need for geoenvironmental protection and risk management should be enhanced, as well as incorporating technology including global positioning system, geographic information system, and synthetic aperture radar interferometry, and information construction in underground development projects.