Abstract
The creation of tridimensional models that represent the quality and geomechanical characteristics of the rock mass to be excavated can be made by using spatial interpolation techniques. The aim of this research is to improve the safety in underground activities, as well as to spread and popularize the use of spatial interpolation methods to represent both the spatial continuity of the quality of the rock mass and the geomechanical variables through geostatistical methods. This article presents and demonstrates the viability of using Q-System block models estimated from the borehole data for previous classification of the rock mass surrounding the underground excavation and rock support design. The block model for the support design of galleries is justified because it allows to previously forecast the kind and quantity of support necessary for the stability of the excavation, as well as the costs with these devices, besides increasing the safety in the operations. Techniques of indicator kriging and ordinary kriging were used to build the Q-System index block model. The model was validated through the techniques of visual inspection and cross validation. The data used in this study were collected from the geotechnical description of 39 borehole core samples with a total measurement of 4,015 meters in Fazenda Brasileiro Mine, located in the town of Teofilândia, Bahia State, Brazil.
Highlights
The geomechanical characterization and classification are important stages of engineering projects that involve rock excavation either in open pit or underground projects
The tridimensional geomechanical model of the Q-System index was generated according to the calculation using the block models of RQD, joint sets (Jn), Joint roughness number (Jr), and Joint alteration number (Ja)
By analyzing the model generated, it can be observed that Rock Mass Quality (Q-System Index) is distributed in layers following the same orientation of the geological body, which, in this region, is formed by a metasedimentary stratigraphic sequence, called Canto Sequence
Summary
The geomechanical characterization and classification are important stages of engineering projects that involve rock excavation either in open pit or underground projects. These procedures aim to ensure the safety of the activities through methods for defining the quality level of the rock mass, which in turn, will provide resources to define the methods of excavation, dimensions, and structures of support (Brady and Brown, 2004; Hoek, 2006; Zingano, 2002). The design of support systems for underground excavations, in general, are based on empirical techniques which consider the dimensions and the time of use of an excavation, the level of stress and the geomechanical quality of the rock mass to be excavated. The forecast of quantity and cost of the support system in mines in operation are made through the correlation of the average between the measurement of the excavation performed and the quantity of support used in the previous years (Brady and Brown, 2004; Hoek et al, 1995; Li, 2017)
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