Kameichiro Nakagawa

The hydrogeology of granitic rocks in deep boreholes used for compressed air storage

Abstract The compressed air energy storage(CAES) is a much-awaited new system for load leveling power supply. An economical system must be developed, preventing leakage of stored air (with pressures of more than 20 atm) using groundwater pressure surrounding an unlined cavern in hard rock. The air tightness of the rock around the cavern must be confirmed. In this study, the hydrogeology of the test site was examined prior to field air tightness tests in the borehole. The results indicate that, when evaluating the hydrogeology of the test site related to the air tightness of rocks, it is necessary to understand the geological structure and fracture characteristics of the site. This is done by means of a field survey, investigations and tests in and between the boreholes, and the examination of the distribution of permeability and pore water pressures.

QUALITY EVALUATION OF DEEP CONGLOMERATE CORE SAMPLES BASED ON LABORATORY TESTS

地下構造物を大深度礫岩に建設する際には, 礫の影響によりコアの強度および剛性が原位置岩盤よりも過大に評価されたり, 逆に, サンプリングによる乱れの影響によって, 原位置岩盤よりも過小に評価されることが想定される. そこで, 深度600mのボーリングコアを用いた大深度礫岩の室内試験を実施し, 礫岩コアの品質評価を行った. その結果, 礫岩コアの品質に影響を与えるサンプリングによる乱れには, 礫分含有率と方解石含有率の2つが複雑に関与しており, 特に, 方解石含有率が小さく礫分含有率が小さいほど, 礫岩コアがサンプリングによる乱れの影響を受けやすいことがわかった.

In-situ study of fluid flow through the discontinuities by liquid tracer test

Abstract Fluid flows in rock masses are controlled by networks that are formed by fractures. Thus, survey and estimation methods for the flow paths has being desired to be established. A liquid tracer test and its transport diffusion simulation are performed to estimate fracture networks at the vicinity of rock mass chamber. Potassium iodide is used as tracer which shows low adsorption. The intensity of the tracer is quantified in laboratory after a series of site tests. It is ensured that discontinuities are main flow paths in terms of quantified intensity of the tracer. Permeability of rock mass, disturbed zone, discontinuities including fractures and contacts between rock mass and concrete must be considered to estimate the fluid path in numerical analysis. The range of the velocity of the flow is about from 0.5 to 5.0 cm/sec.