Strength of Gneiss in the Lishan Landslide Slope under Confining Pressure

Abstract

中国華清池(驪山)地すべりの発生機構の一つとして, 岩盤のクリープ運動が考えられている。有力なすべり面と考えられている断層を挟む2種の片麻岩(上盤をLGNA, 下盤をLGNBと呼ぶ)が採取され, 室温で封圧40MPaまでの, 圧縮強度と残留強度が測定された。両者の強度およびその封圧依存性は等しいことが判明した。LGNAは異方的な結状構造が発達し, これに沿った巨視的なクラックが形成されている。一方, LGNBは巨視的には等方的である。これらの結果から, LGNAの方が空隙率が大きいことを考慮すると, 2種の岩盤境界の間隙水圧が大きくなる可能性があり, この境界のすべりが予期されると考えられる。

Two gneisses from the Lishan landslide slope were studied experimentally, for understanding the mechanism of Lishan landslide.These two rocks are situated faced to a possible potential sliding surface, upper bedrock LGNA and lower one LGNB.LGNA has an extensive anisotropic structure of mylonitized foliation, while LGNB is isotropic.The compressive strength and the residual strength of these rocks were measured at room temperature under a confining pressure up to 40 Mpa.Both rocks have the same compressive and residual strengths and the same pressure dependencies.The compressive strength for the LGNA sample with foliation oriented at 30°to the compressive stress direction is close to the residual strength.LGNA has higher porosity thanLGNB.These results suggest that a high pore pressure could be possibly formed in the boundary between these bedrocks and the boundary could form a potential sliding surface.