On the efficiency and effectiveness of automatic deep drainage systems during an extreme rainfall event: the Mendatica landslide case study (western Liguria, Italy)

This study presents the employment of automatic deep drainage systems to stabilize the Mendatica landslide, one of the largest relict landslides of western Liguria (north-western Italy). Despite the relict state of activity of the main landslide body, a residual kinematic still affects the sector of accumulation zone over which the small village of Mendatica is located and where sharp reactivations of the movements were frequently recorded after severe rainstorms. The aim of this research is to investigate both the efficiency and effectiveness of Electropneumatic Drains® during an extreme rainstorm based on geotechnical monitoring data. On the one hand, the continuous groundwater level measurements allowed to examine the performance of two alignments of wells equipped with electropneumatic pumps during a severe 5-day rainfall event occurred in November 2016, when cumulative rainfalls equalled approximately 800 mm at Mendatica. On the other hand, the subsurface displacements measured from inclinometers before and after the activation of the two draining diaphragms enabled the evaluation of the influence of the automatic deep drainage on the landslide kinematic. The analysis of the hydraulic response of the two drainage lines reveals that, despite the severity of the recorded rainfall values, the pumping wells efficiently worked during the rainstorm since they successfully controlled the increase of hydraulic heads. Furthermore, the outcomes of this study show that, under severe rain conditions, the presence of the Electropneumatic Drains® has mitigated the magnitude of the landslide displacements preventing the development of rapid accelerations of the slope movements.