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

本研究旨在开发压缩空气侵入控制地面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。为此，我们开展了三个课题的研究：(1)土柱和有效气泡的空气渗透试验：在水力渗流的情况下，临界空气梯度可以用与太沙基方法相对应的ic=Gs/(i+e)来表示。相反，由于压缩空气的侵入，孔隙水具有使其分布均匀的倾向，这一点得到了理论和实验的验证。土壤孔隙结构研究：考虑到土壤孔隙大小分布对空气和水分入渗的影响，我们用…对土壤孔隙结构进行了测量和估算。更多的是S的气孔和颗粒直径、土壤颗粒比表面积等。结果表明，所提出的“平均孔径”对于估算水和空气的渗透性以及评价土体的随机性是非常有效的，而随机性是决定空气侵入带的一个重要因素。第二，测量的土壤孔隙分布可以很好地估计土壤的持水特性。(3)压缩空气从隧道中侵入的行为：研究了压缩空气的有效性，特别是从形成的非饱和带如何控制周围水位的角度进行了研究。结果表明，隧道本身的气压与泄流量之间存在着一种独特的关系，由于土的渗透性在空间上的微小差异，压缩空气降低水位的程度并没有得到人们的重视。为了弥补这一不足，研究了一种配套的“控制板法”技术，将空气集中在非常近的区域，显示出空气浓度提高的迹象。较少

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