In the last 250 years the Aquands (depth-limited and waterlogged-volcanic ash soils) in southern Chile were exposed to an intensive land use change inducing physical degradation of these fragile soils. The aim of this work was to evaluate the effect of cyclic loading on soil structural properties and the resilience capacity after simulating one event of soil waterlogging as usually occurs in the field. In undisturbed soil samples, collected from two horizons (2−5 cm, Hz1 [A₁] and 20−23 cm, Hz2 [B_s1]) of a Duric Histic Placaquand under secondary native forest (sNF) and naturalized grassland (NG), the precompression stress (Pc), deformation and recovery indices derived from cyclic loading tests (20, 80 and 200 kPa) were determined. The air permeability (Ka) and soil volume changes were measured during the entire test. The land use change from sNF to NG increased the rigidity of the pore system due to plastic deformation. However, the cyclic loading provokes changes in the pore system (e.g. increase in bulk density as well as decrease in wide coarse pores, which finally induce a decrease in air permeability: 1.89 to -0.17 log μm² and 1.03 to 0.37 log μm² in Hz1 of aNF and NG, respectively) even at loads lower than Pc highlighting the fragility of the soils. As the applied load increases to levels higher than Pc, the plastic deformation induces an increase in pore water pressure and mechanical strength, affecting the pore network and in turn the air permeability of the soil. After one event of ten days of waterlogging conditions, the resilience capacity of the pore system was low. CT-images show that the soil under sNF recovered apart of the deformed porosity allowing an increase in Ka (0.55 ± 0.15 log μm²) after waterlogging conditions, however, no changes were identified for the soil under NG (final Ka = 0.57 ± 0.26 log μm²). Therefore, both land use change and increasing loads on these fragile soils imply the loss of their resilience capacity generating a further soil settlement.

在过去的250年中，智利南部的Aquands（限深层和涝渍的火山灰土壤）暴露于强烈的土地利用变化之下，导致这些脆弱土壤的物理退化。这项工作的目的是在模拟田间通常发生的土壤浸水事件后，评估循环荷载对土壤结构特性和回弹能力的影响。在未扰动的土壤样本中，从两个水平线（2-5 cm，Hz1 [ A ₁ ]和20-23 cm，Hz2 [B _s1]）在次生原生林（sNF）和天然草地（NG）下的Duric Histic Placaquand，确定了预应力（Pc），变形和恢复指数，这些指数来自循环载荷试验（20、80和200 kPa）。在整个测试过程中测量了透气度（Ka）和土壤体积的变化。由于塑性变形，土地利用从sNF变为NG增加了孔隙系统的刚度。然而，循环加载引发在孔系统的变化（例如，在体积密度增加，以及在宽的粗孔减少，这最终引起透气性的降低：1.89至-0.17日志微米²和1.03〜0.37微米的日志²即使在低于Pc的载荷下，也分别以aNF和NG的Hz1为单位），突出了土壤的脆弱性。当施加的载荷增加到高于Pc的水平时，塑性变形会引起孔隙水压力和机械强度的增加，从而影响孔隙网络，进而影响土壤的透气性。在十天的浸水条件下发生了一次事件后，孔隙系统的回弹能力很低。CT-图像表明，SNF下土壤中回收开变形孔隙率允许在嘉的增加（0.55±0.15对数微米的²渍水条件但是，没有变化NG下确定了土壤，之后）（终嘉= 0.57±0.26登录微米²）。因此，土地使用的变化和这些易碎土壤的负荷增加都意味着其回弹能力的丧失，从而导致进一步的土壤沉降。