Numerical modelling of rock-burst loading for use in rock support design at Codelco’s New Mine Level Project

Abstract

The New Mine Level Project is a 130 000 tonnes per day (tpd) panel caving project set to start in 2017. The high stresses, complex structural setting and high mining rates present major challenges in terms of seismicity management and rockburst hazard reduction. This paper is a case study of the calculation of the energy requirements needed to design a dynamic support system for this operation. This analysis starts with the estimation of the seismic source, forecast through the use of numerical modelling and verified with observed past data; later peak particle velocity (PPV) is calculated at the drifts using a PPV attenuation model and an amplification factor is used near the excavations. The amount of fractured rock around the drifts that could be ejected by a seismic event is calculated through numerical modelling. With the ejection velocity estimated from PPVs, energy demand is obtained. All the values resulting from numerical analysis were compared to historical data of similar mine sectors. As the results show that the methodology used in this paper agrees well with previously observed rockburst episodes, it was used to calculate the yielding support of this new deep mine project.

Evaluation of rockburst energy capacity for the design of rock support systems for different tunnel geometries at El Teniente copper mine

“…Then, the energetic demand is divided by the acting perimeter to obtain the energy demand, which is multiplied by FS = 1.5 to finally estimate the energy capacity. The results for yielded rock mass in Table V are below the range between 20 and 40 t/m reported as loose, overbreak, or damaged rock by Jarufe and Vasquez (2014) for the units NMLP, RENO, and Esmeralda.…”

“…It is clear that the YZ-PPV estimation is much closer to the energy capacity value currently adopted. Moreover, there is evidence from rockburst back-analysis that for the NMLP at El Teniente the energy demand causing most of the damage is less than 50 kJ/m 2 , and that higher values are usually related to weak zones due to geometric singularities (Jarufe and Vasquez, 2014).…”

“…El Teniente is actually a group of production units, comprising Diablo Regimiento, Esmeralda, Dacita, Reservas Norte (RENO), Pipa Norte, Sur Andes Pipa, Pilar Norte, and Teniente Sur. A new and deeper extension of the current extraction levels at 1880 m is called the New Mine Level project (NMLP), which is a panel caving project around 1.2 km below ground surface (Jarufe and Vasquez, 2014). At El Teniente, mining at great depths, in addition to high regional tectonic forces combined with particular geological (e.g.…”

“…Kaiser, Tannant, and McCrete, 1996), it is important to verify these approaches. For instance, Jarufe and Vasquez (2014) presented procedures for the determination of the energy demand to be adopted in the dynamic support design at the NMLP. They carried out numerical analyses to calculate contours of a strength factor around a horseshoe excavation to define zones of fractured rock due to seismic events.…”

Peak particle velocity as an indicator of dynamic load exerted on the support of underground workings

“…• measurement of ground motion in underground workings in deep mines, especially in the near field ( Butler and van Aswegen, 1993;McGarr et al, 1991;Dubiński and Mutke, 1996;Kaiser et al, 2005;Mutke, 2002Mutke, , 2008 • measurement of load on the support during natural dynamic phenomena (Szweda, 2003;Masny and Prusek, 2012;Jarufe and Vasquez, 2014;Kaiser and Cai, 2013) • measurement of PPV and of load on the roof support during blast experiments (Kidybiński, 1986;Tannant et al, 1992;Stjern and Myrvang, 1998;Hagan et al, 2001;Ansell, 2004;Malmgren and Nordlund, 2006;Masny, 2006;Hadjigeorgiou and Potvin, 2008;Heal, 2010) The most important conclusions of these articles in terms of our study are as follow. Butler and van Aswegen (1993) presented some data, for the gold mines in South Africa, indicating that the peak particle velocity (PPV) in the near field can exceed the value of 10 m/s (probably related to the ejection velocity of rock).…”