祁连山南北麓明长城夯土抗剪强度指标与分维值相关关系

夯土是具有明显时代、地域、工艺和取材属性的土体，其抗剪性能评价和参数获取是干旱、半干旱地区夯土遗址稳定性评价和控制领域所面临的基础性问题。选取了分布于祁连山南北两麓的我国规模最大的线性遗址明长城18处段落的原状夯土作为研究样本，在建造地点、年代和工艺调查的基础上，采用直接剪切试验、土-水特征曲线测试、颗粒分析试验、相关与回归拟合分析对夯土抗剪强度指标、孔隙和颗粒特征及其联系进行了系统的研究。研究结果表明：18处不同属地夯土依据黏聚力和内摩擦角的取值大小可划分为抗剪性能弱型和抗剪性能强型，颗粒及孔隙的组成与分布具有良好分形特征；黏聚力和内摩擦角值与粒度分维值和孔隙分维值存在量化对应关系，以分维值为变量建立数学模型预测的抗剪强度指标与实测值的误差不超过7.5%，为有效获取抗剪参数和评价抗剪性能提供了新途径。

Correlation between shear strength index and fractal dimension of the rammed earth sampled from Ming Great Wall on the foot of Qilian Mountains

Rammed earth is a kind of soil with obvious characteristics of time, region, technology and materials, and its shear performance evaluation and parameter acquisition are foundation in the field of stability evaluation and control of rammed earth sites in arid and semi-arid regions. Therefore, in this study, the original rammed earth at 18 sites of the most widely distributed and the largest linear rammed-earth build (Great Wall of Ming Dynasty) in China, located in the north and south of the Qilian Mountains, has been selected as the research object, and direct shear test, soil water characteristic curve test, particle analysis, correlation and regression analyses of the rammed earth shear strength index, porosity and particle characteristics and its connection to the research of the system has been used. The results show that the rammed earth in the 18 sites can be divided into weak type and strong type in shear performance according to cohesion and internal friction angle; the composition and distribution of the particles and pores have good fractal characteristics. There are quantitative relationships between cohesion or internal friction angle and the pore fractal dimension or the fractal dimension. The error between the shear strength index of establishing mathematical model for the fractal dimension value and the measured value is no more than 3.1%, which provides a new way for obtaining effective shear parameters and evaluating shear performance.