In order to control the landslide movements in the vicinity of the small centre of Santa Maria Maddalena in centre-north Italy, SPEA Engineering S.p.A designed a large drainage system for “Autostrade per l’Italia” S.p.A.. The stability problems afflicted also the piles foundations of a viaduct of A1 motorway, where movements are directly linked to the amount of precipitations were discovered.
The studies discovered that the area was affected by the reactivation of a massive "paleofrana" (ancient landslide) deposit area, for which a shear surface was detected at a depth varying from 15 to 40 m.
In order to solve the problem, a complex and modular system of 5.6 m diameter collecting circular shafts. A complex scheme of 50m long radial drains has been foreseen to control the ground water level.
The collecting shafts are then connected each other by 2 or more conduits at the bottom, while the lowest shafts are connected to the nearest watercourse for final discharge of the drained water. The use of directional drilling was imperative because of the high accuracy required, and the length of the boreholes between the shafts or the discharge leg (up to 213 m).
Subjects: Directional Drilling, landslide, shaft, secant piles, drainage, drain, well, large diameter well, main well, discharge point.
Author: Marco Angelici
Publisher: DFI, EFFC