A pumped-storage hydroelectric plant located near the village of Solarino, in the province of Siracusa, (Italy), is in an advanced planning stage by ENEL's Design and Construction Department of Venice.

The scheme of the plant involves the excavation of machine and transformer halls inside Mts Climiti mass, which consists of limestone and calcarenite rocks of the Miocene, belonging to the Palazzolo formation.

The area involved in power house excavation includes, from the top to the bottom: medium-grained, slightly cemented whitish biocalcarenites, vuggy-limestones with lateral transitions to calcareous breccia and, more deeply, fine and medium- -grained, cemented, white-yellowish calcarenites (Fig. 1). During the feasibility study, many investigations were carried out in situ, for the structural and mechanical characterization of the rock mass, and at laboratory for defining physical and mechanical properties of the various lithotypes. Laboratory analysis has mainly been developed on the lithotype which will be involved in the powerhouse excavation, that is, on the soft biocalcarenite. Investigations emphasized the importance of textural and structural properties of the rock on the mechanical behaviour, and, especially, a decay process of the mechanical characteristics of water-saturated rock at increasing times.

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Surface surveys and photo interpretation indicate that the area is at least concerned with two fault systems, in E-W and N-S direction, respectively. At the powerhouse site, the rock is only involved in the first system of faults, whose planes are characterized by dip α= 80° – 85° and dip-direction β = 190° – 210°. There are, in particular, two zones of tectonic disturbance, which are about 170 m apart, the innermost one. being about 15 m thick (Fig. 1). The rock mass between the two faults is subdivided into tabular blocks by "closed" and "wide spacing" XX type joints, subparallel to the main faults. The oriented structure of the mass is also defined by subhorizontal "closed" layer joints. To classify the various lithotypes of which Mts Climiti mass are composed, somewhat interesting were the results of laboratory simple determinations performed on integral sample: dry density (pd), sonic velocity (V) and point-load index (Is). A close functional link of linear type, characterized by high values of correlation coefficients, was indeed observed, within a wide range o'! physical parameters, between (pd) and (V) (Fig. 2) and between (Pd) and (Is) (Fig. 3). In particular, as regards the rock involved in the excavation, values 3 of (Pd) included between 1.8 and 2.0 t/m3 were determined. Relevant values of V are included between 3100 and 3900 m/s and values of I, between 0.7 and 1.5 MFa. This lithotype has been studied in detail, both as regards textural and mechanical aspects. The study of thin sections made it possible to classify the rock as biocalcarenite, that is, a lithotype which was formed by heaping up organic remains(complete or broken micro- and macrofossils)and fragments of pre-existing calcitic rocks. The depositing had most likely occurred quite softly, and this resulted in a very great porosity of the deposit itself.

(Figure in full paper)

(Figure in full paper)

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