Numerical analysis of the underground mine of Moncalvo

In this report we discuss characteristics of a quarry in locality of Gessi, Moncalvo municipality at Asti province and Monferatto region. This region is located in the north-easter part of the central hill of Piedmont, and extend to the orographic side of the Po river . Many quarries for the extraction of gypsum are located in the hills of the Monferrato area (central eastern Piedmont). In this area we discuss and analyse a quarry close to the village of Moncalvo, Asti Province Quarry is made of cenozoic cedementary deposits (Eocene and upper Messinian) of marine origin. In lower monferato that formed at Messinian age, we had a formation of Karstic sinkhole opening, that was detected within a inrush in a digging tunnel in feb 2005. This event highlighted that the lower monferrato could be under effect of sink hole hazard. This karstisity could lead to unstability of our mine at some zones. So far some areas of the quarry has been exploited however, activity in some part has been ceased and are unauthurized to exploit due to the karstisity and stability problem. For the excavation of this area initial authorization was issued according to L.R. 69/78 of ten-year duration, within twenty year expansion of the the global mining project for which it comes submitted at the same time for the Province of Asti. on the first year ancillary works and completions of the authorized areas to be excavated were realized and In the subsequent period the expansion of extractable areas , divided into a series of subsequent phases were performed. Until now, several authorization for environment compatibility, excavation of area and its expansion is garanted. For cultivation of the mine, rooms and diaphragm method is applied and the excavation is realized by roadheader machines and material is loaded by dumping trucks. The excavated tunnel geometry is defined with curve sides and, flat roof and floor with dimension of approximately 6*6 meters which is intervened by diaphragms of 13 meter thicknesss. So far, the project is authorized and performed in 3 levels, and each level is interconnected by ramps at beginning and end of the tunnels. Rock type is divided in: Macrocrystal, Microcrystal gypsyum and Marl. Level zero is imbeded at a zone of Microcrystal gypsum with 10 to 30 meters thickness and other 2 levels in dipper layers with almost the same thickness are made of Macrocystal gypsym. These strata are interbedded by marly strata with average dipe of 10 degree in direction of N 60 E at upper and lower side side of each tunnel. Level zero and level 2 is still expanded and Level 1 was exhausted becuase of inrush of water at 2005. To maximize the exploition of the mine, considering safety of the quarry,by now possibility of enlargement of quarry and excavation of 3rd floor is being investigated though this floor has some karstic and possible geo structural problem. Various analysis are performed by different companies each working on various task to obtain correspoding data. As for geotechnical investigations, analysis of core specimen were taken from various sections of quarry and analysis has been conducted by Gdtest s.r.l. also geostratigraphical studies of the mine has been performed by Geotecno s.r.l In this studying using the data obtained on site, we will disuss possibility of expansion of the mine and implementation of new phase, considering numerical analysis of the site. Numerical analysis used in this site was perfomed using plaxir and flac however, in this study flac analysis will be discussed in