人工冻融软黏土微观孔隙变化及分形特性分析

为探讨软黏土融沉及压缩特性的微观机理,以宁波地区软黏土为研究对象,采用冻融、压缩和压汞试验,对冻融和压缩前后的软黏土微观孔隙分布及变化进行了研究。取原状土、融土、压缩原状土、压缩融土4种土样分别进行压汞试验,提出孔径划分方法,结合分形理论对冻融软黏土微观孔隙变化进行分析,研究了软黏土的孔隙分布特征,并采用容量维数对孔体积分布和孔表面积分布进行计算,分析了冻融及压缩前后颗粒接触及孔隙变化。研究结果表明:软黏土冻融后孔体积和孔表面积均增大;原状土和融土压缩后孔体积和孔表面积均减小,软黏土的孔体积和孔表面积80%以上分布于微孔和超微孔中;软黏土冻融及压缩前后孔体积和孔表面积存在分形特性。

Micro pore change and fractal characteristics of artificial freeze thaw soft clay

In order to investigate the microscopic mechanism of thawing collapse and compression characteristics of soft clay, the thawing collapse tests, compression tests and mercury intrusion porosimetry (MIP) are adopted to study microscopic pore distribution and change of soft clay in Ningbo area during the period before and after freezing, thawing and compression. A method for pore diameter division of four kinds of soil samples is proposed, including undisturbed soil, melted soil, compressed undisturbed soil and compressed thawing soil. Through scanning electron microscopy and mercury intrusion tests, the microstructural changes of freeze-thaw soft clay are analyzed according to the fractal theory of mercury. The characteristics of pore diameter distribution of soft clay are investigated, and the pore volume and area distribution are calculated by the capacity dimension. The results show that the pore volume and area of soft clay both increase after melting. The pore volume and area of undisturbed soil and thawing soil both decrease after compression, and more than 80% of pore volume and area of soft clay are distributed in the micro pores and ultra-micro pores. Besides, fractal characteristics exist in the pore volume and area.