A Fundamental Study on the Control of Ground and Groundwater by Intrusion of Compressed Air

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The research aims at the development of the technical guides to control ground and groundwater by compressed air intrusion, by which we could expect the improvement of ground strength against liquefaction and control the groundwater level lowered by compressed air intrusion. For the above purpose we carried out the study of three subjects :(1) Air infiltration test through soil column and effective air bubbles :It is found out that the critical air gradient can be expressed by ic=Gs /(I+e)corresponding to Terzaghi's method in case of hydraulic seepage. On the contrary, pore water has an inclination of making its distribution uniform caused by intrusion of compressed air, which is examined by theory as well as experiment. And also, water seeping or boiling near soil surface is found in state of highly saturated soil.(2) Study of the structure of soil pore :Considering the influence of pore size distribution on infiltration of air and water, we measure and estimate such soil properties a … More s pore and particulate diameter, specific surface of soil particles, and so on. As a result, it is impresively found'out that the proposed 'mean pore diameter' is very effective to estimate the permeability of both water and air, and to evaluate the randomness of soils which is an important factor to decide the air intrusion zone. Second, the pore size distribution of soil measured can be well utilised to estimate the moisture holding characteristics.(3) Behavior of compressed air intruded from a tunnel in the two-dimensional model ground :Investigated is the effectiveness of compressed air especially from such view as how the surrounding water level can be controlled by the formed unsaturated zone. It is found out that there is an unique relationship between air pressure and rate of discharge for the tunnel itself, and that the lowering of water level by compressed air is not so much recognized as to the extent of the expectation, owing to the slight spacial difference of permeability of soil. To make up the inferiority, a complementary technique of 'control plate method' is examined to concentrate the air in very close zone, which shows the sign of air concentration improvement. Less