ANALYSIS OF EFFECT OF AQUIFER DEFORMATION DUE TO GROUNDWATER WITHDRAWAL AND PREVENTING MEASURES OF LAND SUBSIDENCE

摘要

The land subsidence and the construction foundation subsidence caused by groundwater withdrawal from deep foundations are the environmental disaster problems in city construction. It must be considered that the confined aquifer system responds to fluid withdrawal as a dynamic unit whose elemental volumes are compressed due to not only a decrease in porosity but also to a horizontal and vertical displacement. When the deformation effect of unit body upon seepage flow field is considered, the effect of unit body displacement upon seepage flow equation and the effect of deformation upon permeability coefficients must also be taken into account. The seepage flow equation in considering unit body displacement, water body expansion and aquifer compression is deduced via the analysis of land subsidence mechanism caused by groundwater pumping. The theoretical calculation equation for the effect of aquifer deformation upon the coefficient of permeability is established via the analysis of the coefficient of permeability. Also, the effect with and without considering the unit body displacements upon the seepage flow field is analyzed via the real examples. Such controlling measures and schemes as the methods of asymmetrical well laying-out, small discharge with slow withdrawal, etc., so as to reduce land subsidence in the vicinity of wells are suggested via the real example analysis and scheme contrasts, and at the same time, the application ranges, advantage and disadvantage of various measures are analyzed in this paper.