42 research outputs found
Stability analysis of an active marble quarry by DEM modelling
No full textThe marble quarry herein considered is located in the Apuan Alps (Italy), at the base of a deep gully cut by vertical walls, reaching a height of 180 m. The rock mass is cut across by different discontinuity sets, whose spacing is generally wide. The various sets significantly differ in persistency and thus affect the overall strength. In this paper the stability of a plane section of a typical steep face is studied by the Distinct Element Method. The stress-strain behaviour of the discontinuities is represented by the Barton-Bandis model and the presence of rock bridges is explicitly accounted for. The influence of different lengths of rock bridges and spacings on the overall stability was investigated by means of sensitivity analyses. Three different indexes were adopted to synthetically represent the severity of the stress state in the successive stages of excavation. Comparison among such parameters highlights similar trends as the excavation advances, thus indicating that the three indexes generally provide a “measure” of stability. The quarry faces exhibit a very limited amount of displacement and stability is obtained in each of the excavation steps
Analisi delle condizioni di sicurezza di una cava in esercizio con modelli del discontinuo. Memorie Gruppo Naz. Ing. Geotec
No full textAnalisi delle condizioni di sicurezza di una cava in esercizio con modelli del discontinuo
No full textEmpirical and numerical analysis of the blast - induced structural damage in rock tunnels
No full textOne of the main hazards in rock tunneling by using the drill and blast method is the damage of the nearby pre-existing underground structures due to ground vibrations generated by the explosion. A simplified empirical approach is commonly adopted for the assessment of blast - induced structural damage, based on the peak particle velocity (PPV) and related empirical threshold values. A more sophisticated approach consists in numerical analysis of rock – sup-port interaction under the dynamic load induced by blasting. This allows evaluate ground vibrations and internal forces inside the underground structures. Both approaches are applied in the present paper for evaluating the feasibility of a drill and blast tunnel excavation in the vicinity of a pre-existing tunnel. Based on the presented results, it is possible to conclude that the simplified empirical approach significantly overestimates the risk of the blast - induced structural damage compare to the numerical stress analyses
Analysis of convergence data and 3D numerical modelling of tunnels excavated in fine-grained soils
No full textThis paper focuses on the convergence measurements of twin motorway tunnels under excavation in a Pliocene formation in the South of Italy. The tunnels are driven full face, with a cross-section of 120 m(2), by means of a conventional excavation method, up to a maximum depth of 120 m. The primary lining is an open arch made up of shotcrete and steel sets; the definitive lining consists of concrete cast in three different stages. Convergence measurements were analyzed on the basis of the curve-fitting technique proposed by Sulem et al. (1987). Then, the influence on tunnel deformation of overburden and lining construction sequence is investigated. Finally, the role of the primary and final linings in reducing tunnel convergence is investigated by means of a three-dimensional stress-strain analysis, performed with FLAC3D code
Design issues for compressed air energy storage in sealed underground cavities
No full textAbstractCompressed air energy storage (CAES) systems represent a new technology for storing very large amount of energy. A peculiarity of the systems is that gas must be stored under a high pressure (p = 10–30 MPa). A lined rock cavern (LRC) in the form of a tunnel or shaft can be used within this pressure range. The rock mass surrounding the opening resists the internal pressure and the lining ensures gas tightness. The present paper investigates the key aspects of technical feasibility of shallow LRC tunnels or shafts under a wide range of geotechnical conditions. Results show that the safety with respect to uplift failure of the rock mass is a necessary but not a sufficient condition for assessing feasibility. The deformation of the rock mass should also be kept sufficiently small to preserve the integrity of the lining and, especially, its tightness. If the rock is not sufficiently stiff, buckling or fatigue failure of the steel lining becomes more decisive when evaluating the feasible operating air pressure. The design of the concrete plug that seals the compressed air stored in the container is another demanding task. Numerical analyses indicate that in most cases, the stability of the rock mass under the plug loading is not a decisive factor for plug design
Uplift Resistance of Strip Anchors in Cohesive Frictional Mediums of Limited Tensile Strength
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