粒度组成对红黏土干缩裂隙影响

Influence of Particle Size Composition on Desiccation Cracks of Red Clay

为了探讨粒度组成对红黏土干缩裂隙发育的影响,从而给红黏土地区的工程建设及减灾防灾提供理论依据。通过室内干燥试验,研究了粒度组成对昆明呈贡红黏土饱和泥浆样的水分蒸发、干缩裂隙的形成和演化、表面干缩裂隙结构形态的影响。结果表明:(1)蒸发曲线分为4个阶段,常速率阶段是最重要阶段;(2)常速率阶段历时随粒径减小而增长,随粒径分布范围变大而减短;(3)蒸发速率与粒径、粒径分布范围的关系不明显;(4)干缩裂隙形成与演化过程分为5个阶段,受粒度组成影响最显著的是裂隙形成阶段;(5)粒度组成影响裂隙形成阶段历时、不同等级裂隙先后衍生关系、开裂曲线的分段性、裂隙网络结构和土块分布;(6)天然粒组样的干缩裂隙产生向上卷曲现象;(7)粒径分布范围越大,分布非均匀性越强,表面裂隙率越大,而粒径的影响不明显;(8)表面裂隙的分形维数随粒径减小而减小。综上,粒径分布范围和分布非均匀性显著影响红黏土的水分蒸发过程,干缩裂隙的形成和演化,表面干缩裂隙结构形态。

The effects of particle size composition on the development of desiccation cracks in red clay were studied.This study can provide a theoretical basis for engineering construction and disaster prevention in red clay areas.Through laboratory drying tests on saturated mud samples,the effects of particle size composition on the water evaporation,the formation and evolution of desiccation cracks,and the surface desiccation cracks structure morphology of red clay were investigated.The results show that:(1)the evaporation curves can be divided into four stages,and the constant rate stage is the most essential stage of the evaporation curves;(2)the decrease of particle size reduces the constant stage duration;(3)the increased spread of particle size distribution also reduces the duration of the constant rate stage;(4)there is no obvious relationship between evaporation rate and particle size,particle size distribution;(5)the formation and evolution of drying shrinkage cracks can be divided into five stages,and the most significant stage is the stage of desiccation crack formation;(6)particle size composition affects the duration of desiccation crack formation,derivative relationship of different grade desiccation cracks,segmentation of cracking curve,fracture network structure and soil block distribution;desiccation crack of natural grain specimens produces upward curl phenomenon;(7)particle size composition affects segmentation of cracking curve as well;the larger the particle size distribution spread,the stronger distribution non-uniformity of the desiccation cracks of red clay is,and the more significant surface crack rate is,the more significant no effect on the particle size is;(8)particle size composition affects the surface desiccation crack structure morphology and clod distribution on the surface of specimens;the decrease of particle size reduces the fractal dimension of surface cracks.Therefore,it can be concluded that particle size distribution and distribution non-uniformity deeply affect the process of water evaporation,formation and evolution of desiccation cracks,and the surface desiccation crack structure morphology of red clay.These research results can provide reference for reducing the disasters and taking precautions against the calamities to help the construction of the red clay soil area.