Recommended strategies for assessing and managing groundwater dewatering during subsurface construction in sediments adjacent to large river systems: examples from Wuhan in China

摘要

Using the principles of Quaternary geology and geomorphology, this study analyzed the genetic types, composition, lithofacies and spatial distribution of Quaternary deposits in the first terrace sediments adjacent to the Yangtze River in Wuhan. These sediments exhibit a typical binary structural sedimentation rhythm, where sedimentary particles in the same sediment are sequenced progressively fine downstream with river flow which also has obvious grading regularity that affects the engineering properties of these materials. A transverse cross-section outwards from the river channel indicates that the lower sand layer thickness decreases, while the thickness of the upper soft and interlayered sediments progressively increases with distance from the channel. The permeability of the aquifers increases monotonically with depth and the permeability coefficient is anisotropic. From upstream to downstream, the anisotropy coefficient increases significantly and this factor needs to be considered when designing a dewatering system. The main geotechnical engineering problems caused by underground water during the excavation of underground space in sediments adjacent to large river systems are put forward, and the corresponding countermeasures are also recommended.