Abstract: This article aims to investigate whether coal mining ubder the Cretaceous and Jurassic porous sandstone aquifers causes settlement of the upper aquifers due to dewatering. Triaxial compression drainage tests on four kinds of particle grades of porous sandstones are conducted under different conditions i.e. fixed axial pressure, variable confined pressure and pore pressure. The axial deformation characteristics of samples with the decrease of pore pressure are attained, from which formulas are derived for the settlement of lower part of aquifer with a certain thickness due to dewatering. The results show that: (1) The decrease of pore pressure in sandstone will produce the nonlinear axial shrinkage deformation; and the greater particle grades of sandstones, the greater axial strain induces. (2) The axial deformation only relates to initial pore pressure u0 and pore pressure gradient ?u but does not depend on confining pressure σ3, and the greater ?u or u0, the greater axial deformation will be produced as u0 or ?u is constant. (3) The proposed dewatering settlement formulas of sandstones aquifers can be used in calculating the dewatering settlement with a variety of sandstones; so a new method for calculating the drainage settlement for sandstone aquifer within a certain range is provided.

Key words: porous sandstone, compression drainage, pore pressure, axial deformation, aquifer, dewatering, settlement