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

本研究旨在制定压缩空气侵入控制地基和地下水的技术指南，以期提高地基抗液化强度，控制压缩空气侵入引起的地下水位下降。（1）土柱空气入渗试验与有效气泡：发现在水力渗流情况下，临界空气梯度可表示为ic=Gs /（I+e），对应于太沙基法。相反，孔隙水由于压缩空气的侵入而具有使其分布均匀的倾向，这一点从理论和实验上都得到了验证。在高饱和状态下，土壤表层也会出现渗水或沸腾现象。(2)土壤孔隙结构的研究：考虑到孔隙大小分布对空气和水分入渗的影响，我们测量和估计了土壤的这些性质， ...更多信息 结果表明，提出的“平均孔径”对估算水、气的渗透性和评价土的随机性是非常有效的，而随机性是决定空气侵入范围的重要因素。其次，土壤孔隙分布的测量可以很好地利用来估计持水特性。(3)压缩空气从隧道侵入二维模型地面的行为：研究了压缩空气的有效性，特别是从这样的观点，如何通过形成的非饱和带来控制周围的水位。研究发现，由于土的渗透性在空间上的微小差异，空气压力与隧道本身的流量之间存在着独特的关系，压缩空气降低水位的作用并没有得到人们应有的重视。为了弥补这一不足，采用了“控制板法”的辅助技术，使空气集中在很近的区域，显示出空气浓度改善的迹象。少

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