Application of rock mass classification methods for slope stability design in open pit of Otso Gold Oy (Laivan Kaivos)

Abstract. Rock Mass Classification systems are used in the mining industry to classify rock types based on their physical and mechanical properties. It is one of the basic requirements on which the development of the mine will be based. Previous geotechnical studies at the Otso Gold Laivan Mine employed the Rock Mass Quality Index (Q-system), Goelogical Strength Index (GSI), Mining Rock Mass Rating (M-RMR) and later Rock Quality Designation Index (RQD) to determine the quality of rocks at the mine for mine planning, designs, and development, including slope stability analysis and design. However, these were done at a time there was less or no pit development. This study aims to classify unexposed sections of the mine Rock Mass Rating (RMR) and perform a Slope Mass Ratings for the stability of rock slopes in the south pit of the mine. RMR results will be used to compare with previously used classification systems. Three slopes are selected for stability analysis. Field measurements and observations were conducted to obtain data for rock classification and kinematic analysis. Kinematic analysis with the information on rock quality and stability of slopes from calculated RMR and SMR, will be used to perform a slope stability analysis on the present slopes and for consideration in future development of the pit. This study will also suggest slope specifications for further development based on present performances of the slopes

Application of rock mass classification methods for slope stability design in open pit of Otso Gold Oy (Laivan Kaivos)

Rock Mass Classification systems are used in the mining industry to classify rock types based on their physical and mechanical properties. It is one of the basic requirements on which the development of the mine will be based. Previous geotechnical studies at the Otso Gold Laivan Mine employed the Rock Mass Quality Index (Q-system), Goelogical Strength Index (GSI), Mining Rock Mass Rating (M-RMR) and later Rock Quality Designation Index (RQD) to determine the quality of rocks at the mine for mine planning, designs, and development, including slope stability analysis and design. However, these were done at a time there was less or no pit development. This study aims to classify unexposed sections of the mine Rock Mass Rating (RMR) and perform a Slope Mass Ratings for the stability of rock slopes in the south pit of the mine. RMR results will be used to compare with previously used classification systems. Three slopes are selected for stability analysis. Field measurements and observations were conducted to obtain data for rock classification and kinematic analysis. Kinematic analysis with the information on rock quality and stability of slopes from calculated RMR and SMR, will be used to perform a slope stability analysis on the present slopes and for consideration in future development of the pit. This study will also suggest slope specifications for further development based on present performances of the slopes

The reliability of rock mass classification systems as underground excavation support design tools

This thesis examines the reliability of rock mass classification systems available for underground excavation support design. These methods are sometimes preferred to rational methods of support design particularly if detailed information required for the latter mentioned methods is lacking. The classification approach requires no analysis of any specific failure mechanisms or the forces required to stabilise unstable rocks, yet, the support measures thus designed are considered to deal with all possible failure mechanisms in a rock mass.Amongst the several rock mass classification methods developed for application in underground excavation engineering, two have stood out. These are known as rock mass rating (RMR) and tunnelling quality index (Q), introduced by Bieniawski (1973) and Barton et al. (1974), respectively. Over the years, the two methods have been revised and updated so as to improve their reliability as support design tools, yet the two methods are know to have limitations and their reliability has long been a subject of considerable debate. Nevertheless, attempts to assess their reliability in a systematic manner have been limited. Further, some practitioners in the field of rock engineering continue to use these methods as the sole methods of support design for underground rock excavations. The objective of thesis, therefore, is to contribute to a better understanding of the reliability of the two classification methods.This study considered that the reliability of the RMR and Q methods can be assessed by comparing their support predictions with those derived by other applicable methods and also with the actual support installed. Such an assessment can best be carried out during excavation of an underground opening because representative data can be collected by direct observation of the as-excavated ground conditions and monitoring the performance of the support installed. In this context, the geotechnical data obtained during the construction of several case tunnels were reviewed and the two classification methods were applied. The effectiveness of their support predictions was then evaluated against the potential failures that can be predicted by some of the applicable rational methods. Since the rock masses intersected in the case tunnels are jointed, mostly the structurally controlled failure modes were analysed. The support measures predicted by the two methods were compared with each other and with the actual support installed in the case tunnels. Further, the RMR and Q vales assigned to the case tunnels were correlated to observe any relationship between the two.The study showed that the RMR and Q predicted support measures are not always compatible. In some circumstances, the two methods can either overestimate or under estimate support requirements

Analysis of Engineering Geological Uncertainties Related to Tunnelling in Himalayan Rock Mass Conditions

The need for tunnelling in Nepal, as in the Himalayan region in general, is enormous, particularly for hydropower development. Due to active tectonic movement and dynamic monsoon, the rock mass in the Himalaya is relatively weak and highly deformed, schistose, weathered and altered. Predicting rock mass quality, analyzing stress induced problems, in particular tunnel squeezing, and predicting inflow and leakage often have been found extremely difficult during planning stage. Considerable discrepancies have been found between predicted and actual rock mass conditions, resulting in significant cost and time overrun for most of the tunnelling projects. Finding innovative solutions for quantifying geological uncertainties and assessing risk are therefore key factors for cost effective and optimum future tunnelling through Himalayan rock mass. In this thesis, a probabilistic approach of uncertainty analyses has been introduced to deal with the most important geological uncertainties reflecting Himalayan rock mass conditions. A geological uncertainty analysis model concept based on the software program @Risk has been applied for this purpose. The analyses presented in this thesis are based mainly on four headrace tunnel cases from Nepal; 1) 60 MW Khimti I hydropower project, 2) 144 MW Kaligandaki “A” hydroelectric project, 3) 14 MW Modi Khola hydroelectric project, and 4) 69 MW Middle Marsyangdi hydroelectric project. The first three projects have been completed recently and the fourth one is under construction. The thesis identifies the most crucial aspects of tunnel stability problems (geological uncertainties) by reviewing the engineering geological conditions of the respective cases and the Himalayan geology. It also evaluates the theoretical aspects of the main factors influencing on tunnel stability, reviews the engineering geological conditions, the extent of pre-construction phase engineering geological investigations, evaluates the deviation between predicted and actual rock mass conditions, and describes the laboratory testing that has been carried out for the respective cases. Probabilistic approaches that have been applied in the field of engineering geology in past and the basic theory on statistical analyses are briefly discussed. Main emphasis is then placed on the descriptions of useful probability distribution functions (pdf), the @Risk statistical analysis tool, the applied uncertainty analysis model concept and @Risk analysis for the respective tunnel cases. The uncertainty analyses include rock mass quality evaluation based on the Q-system of rock mass classification for Khimti and Modi Khola headrace tunnels, tunnel squeezing based on Hoek and Marinos approach for Kaligandaki and Middle Marsyangdi headrace tunnels, and finally analysis of water leakage from the Khimti headrace tunnel. The degree of correlation between simulated results achieved by the @Risk model and values actually measured in the tunnel is discussed and the sensitiveness and effect of variations in the value of each input parameter and sensitivity of equations and methods used to analyze geological uncertainties are evaluated. It is concluded that the proposed uncertainty analysis approach gives very promising results and has a great potential for analyzing tunnel projects in the Himalayan rock mass conditions, but more cases are needed for conforming the reliability of the methodology.dr.ing.dr.ing

Proceedings of the International Workshop on Rock Mass Classification in Underground Mining

The goal of the workshop was to allow leading practitioners of rock mass classification to share their experiences with the technique. The proceedings contain 16 papers from 9 countries. Applications in both hard-rock and coal mining are represented

Theory and Practice of Tunnel Engineering

Tunnel construction is expensive when compared to the construction of other engineering structures. As such, there is always the need to develop more sophisticated and effective methods of construction. There are many long and large tunnels with various purposes in the world, especially for highways, railways, water conveyance, and energy production. Tunnels can be designed effectively by means of two and three-dimensional numerical models. Ground–structure interaction is one of the significant factors acting on economic and safe design. This book presents recent data on tunnel engineering to improve the theory and practice of the construction of underground structures. It provides an overview of tunneling technology and includes chapters that address analytical and numerical methods for rock load estimation and design support systems and advances in measurement systems for underground structures. The book discusses the empirical, analytical, and numerical methods of tunneling practice worldwide