火山岩坡残积土地区暴雨滑坡泥石流的形成机理

暴雨条件诱发的浅层坡残积土质斜坡破坏的机理受控于土体在低有效围压条件下的应力应变特性。1993年11月4～5日，香港大屿山地区特大局部性暴雨导致在120km²范围内产生自然滑坡泥石流800余处，且绝大多数发生于火山岩风化坡残积土地区。本文对火山岩风化坡残积土开展了室内偏压固结不排水剪和偏压固结常剪应力排水剪试验，揭示了该类土的应力应变特性；在此基础上，分析了暴雨滑坡泥石流的形成机理和过程。

MECHANISM FOR RAINSTORM INDUCED SOIL SLIDE DEBRIS FLOWS IN AREA WITH VOLCANIC ROCK DERIVED SOILS

On November 4～5,1993, Lantau Island with an area of 120 km² which is the larg est outlying island of Hong Kong Territory experienced an extremely severe loca lized rainstorm, which resulted in over 800 soil slide debris flows on the natu ral terrain there. The majority of the soil slides debris flows occurred in are a with volcanic rock derived residual soil and colluvium. Triaxial tests, incl uding compression tests anisotropically consolidated undrained and drained, und isturbed volcanic rock derived soil specimens at constant shear stress, were pe rformed to investigate the stress strain behaviors of the soil. The test result s are interpreted to suggest that soil slide debris flow initiation occurs as a two stage process which consists of an initial dilation failure under drain co nditions followed by undrained failure as a result of strain softening.