Construction of an artificial perched watertable, part 1: Air permeability of soils and aspects of soil failure

The annual precipitation in the Three-river Plain of the People's Republic of China is only 500-600 mm and, besides, the rainfall is uneven; 60-70% of the annual precipitation occurs in July and August and there is almost no rainfall in the winter and spring seasons. Experiments were conducted to form the artificial perched watertable where the runoff caused in summer could preferably be held, by injecting high-pressure air into the soil. A horizontal soil cavity is required, so this paper deals with the determination of the air permeability of soils and the difference in the soil failure mechanisms due to the different air permeabilities. The results show that the air permeability k of 10 m(2) s(-1) MPa-1 defined the situation between the fluidization and the V-shaped soil failure. When the value of k was from 10 to 0.1 m(2) s(-1) MPa-1. the V-shaped soil failure took place and when it was less than 0.1 m 2 s(-1) MPa-1, the soil cavity production took place. In order to produce the soil cavity in the B horizon of the planosol or Cg1 horizon of the meadow soil by air injection, the value of k for these soils should be less than 0.1 m(2) s(-1) MPa-1 and the soil water content of these soils should be more than 30% d.b. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.