Development of Parameters for Numerical Modeling of Geomechanical Systems "Excavation - rock mass - support"

The airway drift of “Trudovskaya” mine of “DTEK” company was chosen as an object of research because of strong effect of rock pressure and water influence in the excavation. The main forms of rock pressure in the excavation are rock falling from the side and the roof, and intense swelling. The main purpose of numerical simulation is to justify the parameters of the support systems of the excavations, which are exploited in the “Trudovskaya” mine. As a test model was accepted a model which reflects a real situation in the vicinity of excavation

Mechanical characteristics of large-section tunnel in soft rock based on various rock conditions and excavation footages

Taking the V-class surrounding rock section at the entrance and exit about Qianqi Tunnel as an example, the deformation rules as well as mechanics about the tunnel in different rock conditions and excavation footages are compared by numerical calculation, and the suitable excavation footage of the relied engineering is also proposed. The results show that the displacements about surrounding rock are greatly influenced by the excavation footage, namely, the arch settlements, horizontal convergences as well as surface settlement of the tunnel increase significantly with the excavation footage. For the preferred rock condition, the maximum bending moments about the preliminary linings at middle step after excavation occurs in the vault, and its increase amplitude has little correlation with the excavation footage. For the poor surrounding rock, the maximum bending moment is transferred from the vault to the arch waist with the increase of excavation footage, and it is basically manifested as the inner tension of the lining. The relationship between excavation footage and maximum deformation as well as mechanical index of vault is also revealed, respectively. The excavation footage of shallow-buried tunnel sections in V-grade surrounding rock is suggested, that is, 1.8m for the preferred surrounding rock condition and 1.2m for the poor surrounding rock condition

USING NON-BLASTING TECHNOLOGIES FOR DESTRUCTION OF HARD ROCK IN SURFACE MINING

Determination the effective application field of non-blasting technology and technologies for the hard rock preparation for excavation during surface mining

Fracture Mechanics Characterization of an AnisotropicGeomaterial

Argillites are considered worldwide as potential host rock for high level radioactive waste given the low permeability and strong adsorption potential. However, the excavation of the galleries of a repository would produce a disturbed zone around the boundaries rich of new fractures which may enhance the conductivity of the rock along the gallery axis. Several mine-by experiments have been performed in underground rock labs to investi- gate the features of the disturbed zone. In Mont Terri URL (Kanton Jura, Switzerland) the EZ-B experiment was specifically conceived for the measurement of excavation induced fractures around a small chamber. The host rock of the URL is a particularly compact and resistant argillite, known as the Opalinus Clay (OPA) excavated and OPA samples were subjected to fracture mechanics tests at the rock mechanics lab of IGAG-CNR in Torino, Italy. The tests aimed at the understanding aspects of the fracturing process occurring in OPA of Mont Terri, which may be considered a transversely isotropic geomaterial, whose planes of isotropy coincide with the beddin

Lattice modeling of excavation damage in argillaceous clay formations: Influence of deformation and strength anisotropy

This paper presents modeling of mechanical anisotropy in argillaceous rocks using an irregular lattice modeling approach, namely the rigid-body-spring network. To represent the mechanical anisotropy, new schemes are implemented in the modeling framework. The directionality of elastic deformation is resolved by modifying the element formulation with anisotropic elastic properties. The anisotropy of strength and failure characteristics is facilitated by adopting orientation-dependent failure criteria into the failure model. The verification of the improved modeling procedures is performed against theoretical model predictions for unconfined compression tests with various bedding orientations. Furthermore, excavation damage and fracturing processes in rock formations are simulated for different geomechanical configurations, such as rock anisotropy and tectonic heterogeneity. The simulated excavation damage characteristics are realistic and comparable with the actual field observation at a tunnel located in an argillaceous clay formation. The simulation results provide insights into the excavation damage zone phenomena with an explicit representation of fracturing processes

Convergence-confinement curve analysis of excavation stress and strain resulting from blast-induced damage

Using the convergence-confinement curves methodology, we analysed excavation behaviour for a range of rock masses of different geotechnical qualities, taking into account blast-induced damage. The novelty of the research is (i) we include blast-induced damage to the rock mass in ground reaction curve construction, and (ii) we analyse results for 54 rock mass and rock geotechnical quality scenarios. The research, an application of a previously developed methodology (González-Cao et al., 2013), provides practical guidelines for the preliminary design phase for an excavation resulting from blasting. Our main conclusions are (i) that rock mass quality has a greater bearing on the plastic radius and excavation maximum displacement than blast-induced damage, and (ii) that the plastic radius and maximum displacement around an excavation increase with the level of blast-induced damage, most especially for poor quality rock masses. This would justify the need to limit blast-induced damage in poor quality rock masses.Ministerio de Economía y Competitividad | Ref. BIA2014-53368

Reliability and Assessment Techniques on Ground Excavation

Planning and assessment on the excavation of the brittle materials (soil or rock) can be done by using the machinery and/or explosives. The reliability assessment has been proposed to predict the failure of ground during excavation process. The stability planning on cutting soil (rock) face by machinery can be compared between the deterministic and the statistical method. The risk of using explosives for rock excavation has to concern on the damage and environmental impacts after blasting events

Empirical correlations between rock cutting parameters and excavated rock surface rebound hardness

In field excavation, cutting tools operate on rock surfaces damaged from previous tool pass, yet, average intact rock properties are often used in field project estimations. This can result in overestimation of excavation time and cost. The ability to accurately correlate the damaged rock properties to the excavation parameters means more reliable estimates of project completion time and costs, and hence improved the application of mechanical excavation technology to a wider range of civil and mining industries. The purpose of this research was to better understand the relationship between rock cutting parameters and the excavated rock surface hardness during mechanical excavation. To do this, Roubidoux sandstone was subjected to linear cutting experiments using a radial drag pick at different cut spacing to depth of cut (s/d) ratios and the resultant forces and chips were analyzed. The rebound hardness of the excavated rock surface was subsequently measured using a rock-type Schmidt hammer. Results and subsequent analysis indicated that the wide variability of Roubidoux sandstone coupled with the complex process of rock cutting prevented a clear determination of the relationship between the cutting forces and the excavated rock surface hardness. 2D stereonet models of the resultant force orientation data and estimates of the tool path deviation indicated that the cutting tool experienced significant deflection during cutting. Finally, it was found that cutting geometry and excavated rock surface hardness contributed significantly to variations in the specific cutting energy --Abstract, page iii