塔里木河干流沿岸分布着大量的风积沙,因季节性洪水的冲刷作用,导致河岸出现滑动破坏现象。为深入探究其破坏机理,通过开展室内直剪、压缩、渗透试验,探究在不同含水率、不同干密度条件下风积沙力学特性的变化规律。试验结果表明：(1)直剪试验：随着含水率增加,黏聚力呈先增大后减小的趋势,在最优含水率处达到峰值,变化曲线可以用二次函数来表示,内摩擦角呈线性减小的趋势。随着含水率增加,颗粒表面形成了具有黏滞性的水膜,达到最优含水率后,水膜产生的黏滞性减弱,导致黏聚力呈先增大后减小的趋势；水膜加厚导致颗粒间发生滚动时受到的滑动摩擦力减小。随着干密度增加,黏聚力、内摩擦角均呈线性增大的趋势。随着干密度增加,颗粒间距减小,范德华力增加,黏聚力增大；同时颗粒间接触咬合能力增强,内摩擦角增大。(2)压缩试验：随着含水率增加,压缩系数、回弹模量均呈线性增大的趋势。在同一轴向应力下,随着含水率增加,水膜加厚,颗粒间发生错动位移时所受到的阻力变小,压缩性增大,回弹量也增大。随着干密度增加,压缩系数呈线性减小的趋势,回弹模量呈线性增大的趋势。随着干密度增加,颗粒之间的联系紧密,颗粒之间发生错动位移时受到的阻力增大,土体接触点的弹性变形增加,压缩变形减小,回弹量增大。(3)渗透试验：随着干密度增加,渗透系数呈线性减小的趋势,分布在1×10-4 cm/s与3×10-⁴ cm/s之间,与经验得出的理论值相差2到3个数量级,对传统的理论渗透系数计算公式进行修正,排除因干密度较低造成的误差后,通过试验得到的实测值与计算得出的经验值较为接近,整体可以用一次函数来表示。随着干密度增加,水分子通过土体颗粒之间的孔隙时受到阻力变大,导致其渗透性减弱。研究结果可为塔里木河河岸的治理和维护提供参考。

A large amount of aeolian sand is distributed along the main stream of the Tarim River. Due to the scouring effect of seasonal floods, sliding damage occurs on the river bank. In order to further explore its failure mechanism, the indoor direct shear, compression and penetration tests were carried out to explore the variation law of mechanical properties of aeolian sand under different water content and different dry density conditions. The results show that: (1) Direct shear test: with the increase of water content, the cohesion increases first and then decreases, reaching the peak at the optimal water content. The change curve can be expressed by quadratic function, and the internal friction angle decreases linearly. With the increase of water content, a viscous water film is formed on the surface of the particles. After reaching the optimal water content, the viscosity of the water film is weakened, resulting in a trend of increasing first and then decreasing. The thickening of the water film leads to a decrease in the sliding friction force when the particles roll. With the increase of dry density, the cohesion and internal friction angle increase linearly. With the increase of dry density, the particle spacing decreases, the van der Waals force increases, and the cohesion increases. At the same time, the contact occlusion ability between particles is enhanced, and the internal friction angle is increased. (2) Compression test: With the increase of water content, the compression coefficient and modulus of resilience showed a linear increasing trend. Under the same axial stress, as the water content increases, the water film becomes thicker, the resistance between the particles becomes smaller when the dislocation displacement occurs, the compressibility increases, and the rebound amount increases. With the increase of dry density, the compression coefficient decreases linearly and the rebound modulus increases linearly. With the increase of dry density, the contact between particles is close, the resistance between particles increases when the dislocation displacement occurs, the elastic deformation of the soil contact point increases, the compression deformation decreases, and the rebound amount increases. (3) Permeability test : With the increase of dry density, the permeability coefficient decreases linearly, distributed between 1×10-4 cm / s and 3×10^-4 cm / s, which is 2 to 3 orders of magnitude different from the theoretical value obtained by experience. The traditional theoretical permeability coefficient calculation formula is modified. After eliminating the error caused by the low dry density, the measured value obtained by the test is close to the calculated empirical value, and the whole can be expressed by a linear function. As the dry density increases, the resistance of water molecules passing through the pores between soil particles becomes larger, resulting in a decrease in permeability. The research results can provide reference for the management and maintenance of the Tarim River bank..

TU443

新疆维吾尔自治区杰出青年科学(2022D01E45);2022年自治区重点研发任务专项(2022B03024-3)