含水率对不同状态红黏土抗剪强度的影响研究

Effect of Water Content on the Shear Strength of Red Clay in Different Plasticity

本文以云南省红河州个旧至元阳高速工程项目为依托,研究含水率对不同状态红黏土抗剪强度的影响。试验统计了坚硬、硬塑、可塑和软塑四种状态的红黏土试样分别25件、25件、17件和12件,并进行直剪试验。根据最小二乘法原理,将不同状态红黏土的黏聚力、摩擦角与含水率进行回归分析,并对试验数据进行综合分析。研究结果表明:坚硬、硬塑、可塑及软塑含水率分别小于34%、34%、41%及35%时,随着含水率的增加,黏聚力分别以2.0、1.01、0.456及0.235的斜率减小,当大于此界限含水率后,黏聚力减小速度减缓,逐渐趋于收敛;随着含水率的增加,硬塑→坚硬→可塑→软塑红黏土的内摩擦角下降速度逐渐变小,对含水率的敏感程度也逐渐减小,其中软塑状红黏土的内摩擦角随着含水率的变化几乎不变;不同状态红黏土相邻一级的黏聚力差值推荐取值10~15 kPa,内摩擦角差值推荐取值1.8~2.5°。

Using the expressway stretching from Gejiu to Yuanyang in Honghe Prefecture of Yunnan Province,the effect of water content on the shear strength of red clay in different plasticity was studied. The direct shear test was conducted on red clay specimens of different plasticity: hard( 25 pcs),hard plastic( 25 pcs),plastic( 17 pcs) and soft plastic( 12 pcs). According to least squares analysis,the relationship between cohesion,friction angle and moisture of red clay in different states was analyzed using regression method along with a comprehensive study of the experimental data. The results show that: when water ratios in four states of red clay are less than 34 percent( hard),34 percent( hard plastic),41 percent( plastic) and 35 percent( soft plastic),cohesion is reduced by the slope of 2.0,1.01,0.456 and 0.235 respectively with the increase of water content. The cohesion reduction slows down and finally converges when the moisture level is greater than the boundary moisture. With the increase of water content,two changes occur.First,the internal friction angle decreases at a decreasing rate in hard,hard plastic,plastic and soft plastic. And second,the sensitivity to moisture decreases. However,with the change of moisture,the friction angle of soft plastic red clay remains almost unchanged. The recommended value of the cohesion difference between adjacent levels of red clay in different plasticity is 10 ~ 15 k Pa,and the recommended value of the friction angle difference is 1.8 ~ 2.5°.