報告書番号

381010

タイトル（和文）

礫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 SEDIMENTARY ROCK MASS AROUND THE UNDERGROUND CAVERN DURING THE EXCAVATION WORK

概要 （図表や脚注は「報告書全文」に掲載しております）

節理の少い礫岩の岩盤内に高さ５０ｍ、幅２７ｍ、奥行き１１６ｍの揚水発電所用の地下空洞が掘削された。空洞周辺で実施された計測の結果を予測解析の結果ならびに他の地点の計測結果と比較し、当地点の空洞掘削時の挙動の特徴について検討した。空洞側壁岩盤の変位に従って増大する天井アーチのコンクリート覆工内応力の各地点の実測結果を比較し、つぎのことが明らかになった。（１）堆積岩の岩盤内空洞の覆工内応力の実測値は、火成岩の空洞の実測値の１／２～１／３である。（２）同種岩盤内空洞で比較すると、覆工内応力は空洞の奥行きの長さに従って大きくなる。当地点で計測された覆工内応力、岩盤変位ともこれまでの計測結果のなかでも最小である。これは、周辺の岩盤が節理の少い礫岩であるためと考えられる。従って、空洞の設計に際しては空洞周辺の岩種と節理の性状を重視する必要があると考えられる。

概要 （英文）

THE UNDERGROUND CAVERN FOR PUMPED STORAGE POWER STATION WAS EXCAVATED IN MASSIVE CONGLOMERATE ROCK MASS.THIS REPORTDESCRIBES MECHANICAL BEHAVIOUR AROUND THE CAVERN BY THE RESULTS OF MEASUREMENTS PERFORMED IN THE COURSE OF EXCAVATION WORK.VALUES OF ALL KINDS OF MEASUREMENTS OBTAINED IN THIS SITE,SUCH AS DISPLACEMENT IN ROCK MASS,STRESSES IN CONCRETE LINING OF ARCH VAUET ETC.WERE VERY SMALL AS COMPARED WITH THOSE WHICH HAD BEEN MEASURED IN OTHER SITES OF UNDERGROUND POWER STATION.THE AUTHORS INVESTIGATED THE FACTORS,WHICH AFFECTED MEASURED VALUES BY THE COMPARISON OF STRESSESS IN ARCH CONCRETE LININGS OF MANY SITE.THE FOLLOWINGS WERE DISCLOSED:(1)STRESS IN ARCH LINING IS CAUSED MAINLY BY DIPLACEMENTS OF SIDE WALLS OF A CAVERN.(2)VALUES OF STRESSES,OBTAINED IN SEDIMENTARY ROCK SITES,ARE SMALLER THAN THOSE IN IGNEOUSROCK SITES. THE RATIO BETWEEN THESE VALUES IS ABOUT 1:2 OR 1:3.(3)IN THE SAME KIND ROCK SITE,VALUES OF STRESS DEPEND ON EXTENT OF THE SIDE WALL.(4)CORRELATIVITIES OF DEFORMABILITY OF ROCK MASS OBTAINED BY IN-SITUTEST OR INITIAL GROUND STRESS TO STRESSIN LINING ARE NOT CLEAR.FROM THESE RESULTS MENSIONED ABOVE,IT IS CONCLUDED THAT DISPLACEMENTS OF SIDE WALLS ARE CAUSED BY OPENNINGS OF JOINTS IN ROCK MASS MAINLY, AND DISPLACEMENT CAUSED BY ELASTIC STRAIN OF ROCK MATERIAL IS NOT SO LARGE.IN THIS SITE,ROCK MASS CONSIST OF MARSRVE CONGLOMERATE AND HAS FEW JOINTS,THEREFORE MEASURED VALUES OF DISPLACEMENTS IN SIDE WALLS AND STRESSES IN LINING ARE VERY SMALL.THESE RESULTS ARE USEFUL TO DESIGN OF A CAVERN FROM NOW ON.

報告者

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