黑方台马兰黄土固结条件下孔隙变化特征

摘要

The frequent occurring landslides and more than 3m subsidence at Hefangtai are caused by long-term irrigation in Linxia city,Gansu province.This paper analyzes the microstructure nature of the loess collected from top and bottom of Heifangtai.The consolidation test with increasing water content and mercury intrusion porosimetry are conducted on the loess samples in this paper.The loess at the top of the platform is characterized by loose particle,packing with bigger porosity.The clay content is lower.The loess at the bottom of the platform,however, processes relatively tight arrangement of the particles with less porosity, and higher clay content.In the consolidation test,the void ratio falls sharply.The microstructure strength of the loess reduces suddenly or loss when 21%water content.This abrupt change in bottom loess does not occur,which indicates relatedly weak water sensitivity.The pore diameter compression interval of the top loess is >1 00μm.The 5~20μm.The compression interval of the bottom loess is >1 00μm and 1~1 0μm.However,the volume of the pore,<0.1μm,increases as the water content increases.%甘肃临夏地区的黑方台由于长期的农业灌溉导致台缘滑坡频发，整个台面普遍下沉3m以上。文章通过原状黄土的增湿固结实验、压汞试验和环境扫描电镜等对黑方台顶部和底部的原状黄土进行孔隙特征的分析。黑方台顶部黄土颗粒排列极为疏松、孔隙较大、黏土含量较低。底部黄土排列较为紧密，具有一定的孔隙，黏土含量较高。顶部黄土在固结实验中，21％含水量的黄土发生孔隙比突降，黄土的微观结构强度此时迅速减小或丧失。然而底部黄土没有发生明显的突变，水敏性不强。利用压汞试验确定了黑方台顶部黄土的孔隙主要压缩区间为孔径大于100μm、孔径5～20μm之间；底部黄土的孔隙主要压缩区间为孔径大于100μm、孔径1～10μm之间。而且孔径小于0.1μm的孔隙随含水量的升高具有增加的趋势。