報告書番号

381014

タイトル（和文）

片岩における大規模空洞掘削時の岩盤挙動

タイトル（英文）

BEHAVIOUR OF SCHISTY ROCK MASS AROUND THE UNDERGROUND CAVERN DURING EXCAVATION WORKS

概要 （図表や脚注は「報告書全文」に掲載しております）

ほぼ水平な片理を持つ片岩の岩盤内に，高さ４７ｍ，幅２６ｍ，長さ９８ｍの揚水発電所用地下空洞が掘削された。掘削時に実施された計測結果を予測解析の結果ならびに他地点の計測結果と比較し，空洞掘削における片理の影響を調べた。得られた知見はつぎのようである。（１）空洞上部岩盤の鉛直変位は他地点とほぼ同じであり，水平方向に発達している片理の影響は顕著ではない。（２）側壁岩盤の水平変位に従って増大する天井アーチのコンクリート覆工の応力は，他の堆積岩の地点と同程度で，火成岩地点の１／２～１／３である。（３）計測断面，鉄管路側と放水路側等位置による計測値のバラツキが少い。以上のことから，均質な片岩における空洞掘削時の変位は，大きくないことが明らかになった。以上の検討の結果は，今後の同種岩盤内地下空洞の設計に役立つものと考えられる。

概要 （英文）

THE UNDERGROUND CAVERN FOR PUMP STORAGE POWER STATION WAS EXCAVATED IN BLACK SCHISTY ROCK MASS. THE DIP OF SCHIST PLANE AT THIS SITE IS NEARLY HORIZONTAL. THIS REPORT DESCRIBES THE FEATURE OF MECHNICAL BEHAVIOUR AROUND THE CAVERN BY THE RESULTS OF MEASUREMENTS PERFORMED IN THE COURSE OF EXCAVATION WORK. BY THE EXAMINATION OF RESULTS OF MEASUREMENTS, THE FOLLOWINGS ARE DISCLOSED: (1) COMPARED WITHTHE VALUES OF OTHER SITES, VERTICAL DISPLACEMENTS OF ROCK MASS AT THE TOP OF THE CAVERN VAULT ARE NOT SO LARGE, IT MEANS THAT EXISTENCE OF SCHIST PLANE IS NOT EFFECTIVE. (2) STRESSES IN THE CONCRETE LINING OF ARCH VAULT, WHICH ARE CAUSED MAINLY BY DISPLACEMENTS OF SIDE-WALLS OF A CAVERN, AND VALUES OF WHICH OBTAINED BY MEASUREMENT IN THIS SITE ARE SMALLER THAN VALUES OBTAINED IN OTHER IGNEOUS ROCK SITES, AND ARE NEARLY EQUAL TO VALUES IN OTHER SEDIMENTARY ROCK SITES. (3) THERE ARE FEW DIFFERENCES AMONG THE VALUES MEASURED AT VARIOUS CROSS SECTIONS OR BOTH SIDESOF CAVERN, BECAUSE ROCK MASS IN THIS SITES IS HOMOGENEOUS. FROM THESE RESULTS MENTIONED ABOVE, IT IS CONCLUDED THAT BEHAVIOUR OF SCHISTY ROCKMASS AROUND A CAVERN DURING EXCAVATION IS SIMILAR TO THAT OF SEDIMENTARY ROCK MASS AND EXCAVATION WORKS CAN BE CARRIED OUT STABLY.

報告者

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