Rainfall is among the most relevant triggering factors of landslides. With the aim of defining a model of the influence of rainfall on deep landslides, this paper presents data of a long-term monitoring of pore water pressures in a clayey earthflow, and the results of many field permeability tests carried out with several procedures. Pore water pressures are being monitored in the Costa della Gaveta slope since 2005. In the last years, new instruments have been installed and permeability tests have been carried out in the stable formation, in the landslide body and in the slip zone. The hydraulic conductivities of the three different zones of the subsoil have been evaluated by two types of field tests: falling head tests (by Casagrande piezometers and test wells), and localized constant head tests (by a permeameter ad hoc designed). The experimental data show that: a) pore water pressures along the slip zone respond to rain more than in the landslide body and in the stable formation, even at about 25 m depth; b) the hydraulic conductivity k_sz of the slip zone is much higher than that of the landslide body, k_l, in turn higher than the hydraulic conductivity of the stable formation, k_f. The numerical 3D modelling of steady-state reference conditions and of transient processes caused by the historical rainfall series shows that the occurrence of k_sz higher than k_l and k_f determines an overall drainage effect which makes the global limit equilibrium safety factor SF greater than that evaluable for other possible conditions. On the other side, even the lowest measured hydraulic conductivity k_sz provides seasonal rain effects on water pressures along the slip surface such to determine significant SF variations in phase with the observed seasonal displacement rates.

降雨是滑坡最相关的触发因素之一。为了定义降雨对深部滑坡的影响模型，本文提供了粘土土流中孔隙水压力的长期监测数据，以及使用多种程序进行的许多现场渗透率测试的结果。正在监测Costa della Gaveta 的孔隙水压力自 2005 年以来，在稳定地层、滑坡体和滑移带中安装了新仪器并进行了渗透性测试。底土三个不同区域的水力传导率已通过两种类型的现场测试进行评估：落水头测试（通过 Casagrande 测压计和测试井）和局部恒定水头测试（通过专门设计的渗透计）。实验数据表明：a)沿滑动带的孔隙水压力比滑坡体和稳定地层更能响应降雨，即使在约 25 m 深度；b)滑移带的水力传导率 k _sz远高于滑坡体的水力传导率k _l，进而高于稳定地层的水力传导率 k _f。稳态参考条件和由历史降雨序列引起的瞬态过程的数值 3D 建模表明，高于 k _l和 k _f的 k _sz的出现决定了整体排水效应，这使得全局极限平衡安全系数 SF 大于可评估其他可能的条件。另一方面，即使测得的最低水力传导率 k _sz也会对沿滑面的水压产生季节性降雨影响，从而确定随观测到的季节性位移速率在相位上的显着 SF 变化。