祁连山麓18处明长城段落夯土的渗透性能

Permeability of rammed earth in 18 sites of the Ming Great Wall section at the foot of the Qilian Mountains

以分布于祁连山南北麓18处具有相同区域、时代、工艺和取材特征的明长城段落夯土为研究对象,通过变水头渗透试验、颗粒分析试验、基质吸力试验及扫描电子显微镜试验,在细观及微观尺度下开展夯土渗透性能及影响因素的研究.结果表明,祁连山南北麓18处明长城段落夯土的饱和渗透系数(k_(20))=3.89×10^(-6)~6.97×10^(-5) cm/s,根据k_(20)划分为弱透水型和微透水型.通过对夯土微观结构观察和分析,发现其微观结构与表现出的渗透性能有良好的对应关系,其中具有粒状-镶嵌-接触结构的12处夯土为弱透水型夯土,具有粒状-镶嵌-胶结结构的6处夯土为微透水型夯土.通过对k_(20)和颗粒与孔隙的指标进行相关性分析及回归分析,发现k_(20)与粒度分维值和孔隙分维值存在良好的相关性,其函数关系分别服从指数和线性法则.

The study took the rammed earth of the Ming Great Wall section at 18 sites in the south and north of the Qilian Mountains as the study objects, which were built in the same period via the same building technology and possessing the same material characteristics. Based on the falling head permeability test, particle analysis test, matrix suction test and scanning electron microscope test, the research on the permeability of rammed earth and its influencing factors were carried out on the mesoscopic and microcosmic scale. The results showed that the saturated permeability coefficients of rammed earth in the section of the Ming Great Wall at 18 sites on the south and north slopes of the Qilian Mountains were distributed in the range of 3.89×10^(-6)-6.97×10^(-5) cm/s, and according to the difference in saturatedpermeability coefficients, it was divided into two types: weakly permeable and micro-permeable;through the observation and analysis of the microstructure, it was found that the microstructure had a good corresponding relationship with the displayed permeability;of them, 12 rammed earth sites with a granularinlaid-contact structure were of weakly permeable rammed soil, and 6 with granular-inlaid-cement structure were of micro-permeable rammed soil. Through a correlation analysis and regression analysis of the saturated permeability coefficient and the indicators of particles and pores, it was found that the saturated permeability coefficient had a good correlation with the value of the particle size fractal dimension and the value of pore fractal dimension, and its functional relationship obeyed the exponential and linear laws.