Abstract
The ground air flow induced by atmospheric pressure fluctuations is known as the barometric pumping. In most diluvial uplands of Japan, ground air flows mainly through permeable layer between upper surface aquiclude and lower ground water table. Consequently, vertical flow of ground air to atmosphere is impeded and ground air flows horizontally. However, any study about horizontal and two-dimensional ground air flow has not been proposed yet. In this paper, we regarded permeable layers in diluvial upland as rectangles and showed the analytical solution (the periodic steady state solution) for ground air pressure fluctuation in the rectangular homogeneous porous medium induced by the trigonometric atmospheric pressure fluctuation on condition that ground air flows two-dimensionally and horizontally.
The calculations using the analytical solution show that the ground air flow in the rectangle approximately are regarded as one-dimensional flow (round-trip movement) toward the closest point on the boundary and the rectangle is divided into the regions in which ground air flows toward the long side and the short side. The max length of the ground air pressure propagation path in the rectangle is half-length of the short side. We showed the finite element method to calculate ground air pressure fluctuation in permeable layers of which shapes are complicated. To verify the possibility of decreasing necessary memory of computer in the calculation, we investigated applicability to use the finite element method in the small polygon that is cut from the large polygon. In case that the small polygon is cut at appropriate position, it is possible to calculate ground air pressure fluctuations by using the small polygon.
