Analysis of a large-scale landslide affecting an ancient village in Central Italy

摘要

The medieval village of Montelparo is located in a hilly area of Marche Region, in the East of the Apennines chain. It is affected by a large traslational landslide. The landslide body is part of a monocline mostly formed of well stratified sandstones, positioned on a deep-seated clay bedrock. A system of direct faults have favoured the detachment of the sandstone slab sliding on a clayey slip surface and the formation of a well marked graben structure. In the short term the critical hydraulic conditions are similar to the ones occurring in rockslides, where a triangular water pressure diagram operates inside the graben area and a rectangular one acts on the sloping clayey slip surface. An indirect confirmation of this mechanism was provided by the acceleration of the movement in coincidence with a rainfall critical event occurred in December 1999, when significant piezometric peaks were also recorded. According to the mechanism invoked, any increase in water level makes the water thrusts (on the rear of the landslide body and at its base) increase exponentially. Hence the importance of maintaining the water levels permanently low, well below the critical values. The paper besides dealing with the landslide mechanism introduces the main control works designed. They belong to the category of the deep drainage, useful to increase the shear strength on the slip surface.