The possibility of dynamic failure and deterioration of the sealing capacity of critically stressed rock due to the infiltration of a compressible non-wetting phase fluid is examined through laboratory experiments. Rock samples were regarded as critically stressed under normal faulting conditions, and was set up to mimic the conditions of the cap rock just above a reservoir layer. Two kinds of external stress conditions were applied to the sample, i.e., close to an isotropic stress condition and close to a critical condition for failure. Air in a gas accumulator was infiltrated into the sample from the bottom end. Axial and circumferential strains of the sample and air pressure at the inlet were monitored during the experiment. Experimental results showed that the sample under stress conditions close to the critical condition became more deformable, resulting in failure, while that under a hydrostatic condition did not deform significantly and behaved elastically. An increase in the permeability of the critically stressed sample was also suggested. Understanding an in-situ stress state and considering a possible progressive failure of the cap rock are considered to be important when evaluating sealing capacity.

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人口減少・超高齢化が進む中で、効率化や財政負担の軽減・平準化を主目的としてPFIやPPP等に代表される民間活力の導入がなされて２０数年が経過する。これらの官民連携の取り組みは、これまで主として、官（行政）と民（事業者）の二者による連携に焦点が当てられてきた。一方で公共性を担保するためには、公共サービスの受け手である市民参加の視点を加味することが欠かせない。本研究では、公共性の担保における官の決定権問題と、市民参加（顧客ニーズの把握）の意味を確認し、官民連携事例の事業プロセスを、市民参加の視点を加味して類型化し、分析を行った。

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