黄土-泥岩接触面滑坡滑带土力学特征研究

Study of the mechanical characteristics of slip zone soils sampled from loess-mudstone interface

滑带土是滑坡形成过程中形成的一层结构性较差的土体,是滑坡的重要组成部分。其物理力学性质、微观结构与滑坡的形成以及后期运动特征密切相关。黄土-泥岩接触面滑坡是按照滑坡地质成因划分的一种上层黄土、下层泥岩的具有"双层异质"结构的滑坡。此类滑坡由于在滑动中具有缓动低速的特点,往往早期不易被发现,发现时已造成了严重的危害。采用GDS三轴仪对天水地区花南村滑坡、半山村滑坡和咀头村滑坡三个黄土-泥岩接触面滑坡的滑带土力学性质进行研究,结合滑带土微观结构特征,分析黄土-泥岩接触面滑坡滑带土的力学变化特征及其变形内在机理。研究发现:滑带土中大量存在被黏土颗粒包裹的大颗粒,这些大颗粒在滑带土变形过程中经历错位、滑移等过程后,大颗粒进一步滑移受到黏土质限制,导致黄土-泥岩接触面滑坡滑带土在宏观上表现出应变硬化的典型特征。此外,剪切中孔隙水压力无法及时消散也是此类滑坡变形的重要特征之一。应变硬化造成滑带土在滑动中强度未出现残余值而导致滑坡处于持续运动中,能量的释放方式属于缓慢释放型。因此该类滑坡滑动具有缓动低速的特性。

Slip zone soil,an important part of landslide,is a layer of soil which has weak structure,of which the physical and mechanical properties and the microstructure are closely related to the development of landslide and the followed motion features.The loess-mudstone interface landslide is classified according to the geological origin,of which the upper part is loess while the underlying one is mudstone.This kind of landslide is difficult to be noticed in early stage due to the features of gentle movement with low velocity.So when it caught the attention,it had resulted in serious harm.In this thesis,the GDS triaxial apparatus was used to research the mechanical properties of the slip zone soils which were sampled from Huanancun landslide,Banshancun landslide and Zuitoucun Landslide.The change characteristics of the mechanical properties were analyzed in combination with microstructure features.The research results show that there are larger particles wrapped by clay in the slip zone.These larger particles suffer dislocation and slippage during the deformation of slip zone soil.Meanwhile,they would be restricted by the ambient clay.As a result,in the slip zone soil shows typical macroscopic characteristics of strain hardening.Besides,another important feature of this kind landslide is that the pore water pressure cannot dissipate timely.Strain hardening makes the slip zone soil remain in continuous movement without significant residual strength,and the energy is releasing gradually.These reasons makes this kind of landslide moves gently with low velocity.