A study on the anisotropy of surface soils on slopes subjected to freeze-thaw history

在寒冷地区，春季坡面表层土壤往往向下移动。它的移动是由反复的冻融循环引起的。要正确评价边坡稳定性，进行有效的边坡防护工程，就必须了解边坡在循环过程中强度、刚度、渗透性等的变化。顺便说一下，众所周知，反复的冻融循环会在表层土壤中形成冰透镜体。它们平行于地面分布，因此它们在斜坡上平行于剪应力分布。在这项研究中，我们进行了冻胀试验，得到的孔隙比和渗透率的变化，在冻融循环，直接盒剪试验，得到的强度-变形特性的循环，和弯曲元件试验，也得到了剪切波的速度与垂直和水平传播的循环。因此，平行于剪应力方向的冰透镜体的形成对表层土的力学性质有重要影响。

In cold areas, surface soils on slopes often move downward in spring. Its moving caused by repeated freeze-thaw cycles. If we properly evaluate slope stabilities and carry out effective slope protection works, we should understand variations of strengths, stiffnesses, permeabilities, and so on in the cycles. By the way, it is known that repeated freeze-thaw cycles make ice lenses within surface soil. They spread parallel to ground surface so they are arranged parallel to shear stress on the slope. In this study we carried out frost heave tests that obtained changes of the void ratio and permeability in the cycle of freezing and thawing, direct box shear tests that obtained strength-deformation characteristics in the cycles, and the bender element tests that also obtained velocities of shear waves with vertical and horizontal propagation in the cycles. Then we conclude that the formation of ice lenses made parallel to shear stress is important for mechanical properties of surface soils.