Abstract

It is well known that the mine legacy is a serious concern to present communities. The high risk associated with subsurface voids together with the lack of knowledge of geometric and geomechanical features of former mining areas make abandoned underground mines one of the current challenges for countries with a long mining history. In Italy, no long-term assessment of abandoned mine sites is required by law. In this paper we deal with the case study of Montevecchia mine, a marl mine in northern Italy abandoned in 1958 after a massive collapse. The event affected all mine levels along their middle sections and caused a large sinkhole. We initially performed geological and geophysical investigations to develop a physical model of the site. After that we carried out several numerical simulations to evaluate the stability of tunnels still in place.

Introduction

Abandoned mines represent a serious concern in countries with a long mine history. After being exploited for years, depleted mines are closed and abandoned; so all the monitoring activities cease and also drainage pumps are stopped, letting water flood the caves. The mine undergoes a progressive decline without any control; indeed in Italy long term assessment of abandoned mines is not required. The direct consequence is the presence of a number of closed mines whose extent and condition are unknown; even documentation is usually lost or inaccurate. These mines represent a constant threat to human settlements in terms of water pollution, subsidence and collapses. Due to this critical situation many efforts are posed to limit the hazard due to mines. The paper presents some guidelines to deal with mine through the description of a case study. The study develops through 1. historical data collection 2. geometrical and geotechnical features assessment 3. stability evaluation by numerical models 4. Risk scenarios development. The case study will show difficulties arising during the analysis of an abandoned mine and how is possible to overcome them.

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