标题： 土壤蠕动由环境条件的周期性变化促进 显示英文标题

标题： Soil creep facilitated by cyclic variations of environmental conditions

摘要： 斜坡地形往往会随时间向下蠕动，即使其坡度低于名义上的休止角。 这种行为可能源于环境条件的周期性变化，例如温度和湿度的日变化或季节性波动。 我们通过考虑一种非热屈服应力材料在施加应力低于临界屈服应力值$\sigma_c$的情况下来研究这一过程。 通常，在这种情况下，材料完全不会流动。 然而，在系统参数的周期性时间变化下，每个周期后可以留下一定量的不可逆变形，并且可以诱发整个系统的长期稳态流动。 在我们的模型中，我们循环内部弹性相互作用的强度，以模拟实际土壤中环境条件的周期性变化的影响。 我们发现，当从下方接近$\sigma_c$时，每周期的变形量会增加，并且当从上方达到$\sigma_0<\sigma_c$这一新的临界应力时，变形量会减少甚至消失。 有趣的是，$\sigma_0$在疲劳损伤传播的背景下起着类似于耐久极限的作用。 尽管模型很简单，但我们的结果为次临界地貌演化提供了新的视角，对长期内山坡的蠕动以及失控滑坡的前兆具有重要意义。 显示英文摘要

摘要： Sloped terrains tend to creep downward over time, even when their slope is below the nominal angle of repose. This behavior can result from periodic variations in environmental conditions, such as daily or seasonal fluctuations in temperature and humidity. We study this process by considering a model of an athermal yield stress material under an applied stress lower than the critical yield stress value $\sigma_c$. Normally, in such a situation the material does not flow at all. However, under cyclic temporal variation of system parameters a finite amount of irreversible deformation can remain after each cycle, and a long term steady-state flow of the whole system can be induced. In our model, we cycle the strength of internal elastic interactions to mimic the effect of cyclic variation of environmental conditions in the real soils. We find that the amount of deformation per cycle increases if $\sigma_c$ is approached from below, and it decreases and even vanishes at a novel critical stress $\sigma_0<\sigma_c$ when this, in turn, is reached from above. Interestingly, $\sigma_0$ plays a role similar to the endurance limit in the context of fatigue damage propagation. Despite the model's simplicity, our results offer a fresh perspective on subcritical landform evolution, with implications for the creep of hill slopes over long periods and the precursors to runaway landslides.