報告書番号

U98032

タイトル（和文）

堆積岩における水封式圧縮空気貯蔵のための地質工学的評価 -－古第三紀礫岩におけるボーリングによる調査研究－-

タイトル（英文）

Geotechnical evaluation for the compressed air energy storage in submerged sedimentary rock : geological investigation of Palaeogene conglomerate with a bore hole－

概要 （図表や脚注は「報告書全文」に掲載しております）

水封式圧縮空気貯蔵のための貯槽周辺岩盤には空洞の安定性および水封機能を確保できる強度・変形性，透水性が，貯槽周辺には水封機能に必要な圧力を与える地下水圧分布が要求され，地下深部の岩盤性状や水理地質構造の解明が重要となる。この観点から，礫岩を主体とした古第三紀の堆積岩について600mの深部ボ－リングにより地質調査を行った。調査地点の礫岩は方解石を多く含むと硬質で良好な岩盤となり，方解石の含有量が部層すなわち堆積サイクルの下部で多い場合が認められる。速度検層による弾性波速度は，堆積サイクル内の岩相変化や方解石の含有量に影響される。また方解石の多い砂岩～礫岩や頁岩からなる難透水層の下部を境とする間隙水圧分布の変化から，難透水層下部の上・下位の地下水ポテンシャルが異なると推定される。このように礫岩特有の堆積学的および鉱物学的特性と地質構造との関連より，地質工学的評価が可能であることが判った。

概要 （英文）

The excavated storage caverns for the compressed air energy storage (CAES) system proposed by us are unlined and air leakage from the caverns are prevented by surrounding underground water. In this case it is necessary for the rock mass around the storage caverns to have the mechanical properties and the properties of deformation which keep the caverns stable, and to have the permeability which keeps the air tightness of the caverns. And then it is necessary for underground water pressure around the storage caverns to keep the air tightness of the caverns. In geological survey it is important to clarify the hydrogeological structures and engineering properties of the rock mass in the deep part. From these points, a series of preliminary investigations was carried out by drilling a bore hole of 600 meters depth in the Palaeogene sedimentary rock, which is mainly consist of conglomerate, in this investigated site. As calcite is abundant in the matrix of conglomerate in this site, rock mass is hard and good. And the contents of calcite are abundant in the lower part of some of the members, that is, the cycles of sedimentation.The values of elastic wave velocity obtained with the geophysical logging in the drilled hole are influenced by the changes of the rock facies in the cycle of sedimentation and the contents of calcite in the matrix. When calcite is abundant, velocity is high and sedimentary rock is hard. The property of the distribution of underground water pressures below the lower part of impermeable layers composed of sandstone and conglomerate abundantly containing calcite and composed of shale is differ from the one above the lower part of these impermeable layers. The potential of underground water below the lower part of these impermeable layer is lower than the one above the lower part of these layers. From these results, it is surely feasible to have a geotechnical evaluation for CAES in consideration of the relation between sedimentary, mineralogical characteristic and geological structure.

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