Modelling subsidence in the Hanoi city area, Vietnam

A study of land subsidence due to groundwater pumping in the city of Hanoi, Vietnam, was conducted by collecting and analyzing data on the geology, hy drology, soil properties, and observed settlements. The city of Hanoi is un derlain by sediments consisting of organic and inorganic clays, silt, peat, sand, and gravel. The pumping of groundwater causes consolidation of compr essible aquitard layers. The water demand for the city of Hanoi is increasi ng with time. The present total rate of water pumping is 450 000 m(3)/day, and there is a proposal to increase the rate to 751 000 m(3)/day by the yea r 2010. This research program involved the modelling of seepage related to pumping along with a stress-deformation analysis. The effect of surface inf iltration was also modelled. The settlements computed for parts of the city of Hanoi were compared with measurements of settlement in the city area. T he simulation results appear to be in fairly good agreement with the measur ement results. The study showed that subsidence due to groundwater pumping is a serious problem in the city of Hanoi. It is important to continue to m easure settlements and compute possible deformations associated with actual rates of pumping.