Opinion on a Reliable Rock Engineering ToolBox for Mining Industry

engineering in computer tool-numerical in 2D or 3D in order engineering for decision making. engineering parameters development and of stress, strain, and displacement for stability analyses. vibration and seismicity related to mining process, and so on…. Information provided from numerical models source of information making decision a I trust the information from model?” In complete toolbox rather than numerical model for appropriately to to that question. a engineering to The is a combination of three tools”, modelling”, and monitoring”. the for the methodology.


Stress measurements by SINTEF
Since the late 1960ies we have developed equipment for in-situ rock stress measurements. This also includes equipment for long-term monitoring of rock stresses. The present applied techniques are: A.
Self-developed and highly improved versions of the originally South African CSIR 2-D Doorstopper B.

C. Self-developed hydraulic fracturing equipment
These methods have been continuously improved through extensive research and application over the last 50 years. The described techniques have been used widely in various projects, including mining industry, hydropower, oil and gas storage, and infrastructures in many countries around the world. Our reference list comprises 150 locations in18 countries. As each client or location may represent a number of measuring sites, the total number of sites/measuring holes are in the order of 330, corresponding to approximately 3000 single measurements.

Stress monitoring by SINTEF
SINTEF/NTNU has developed a special version of the "door-stopper" for long term monitoring purposes which appear to behave stable. During drilling of the hole, standard doorstopper measurements are taken at selected intervals to obtain the initial stresses. The last measurement is taken as close as possible to the selected depth of the monitoring doorstopper, and this value is taken as initial value for the monitoring equipment After installation of the door-stopper, strain change in the rock can be recorded, and the correspondent stress

TRIPOD: Combination of stress measurement-numerical modelling-site monitoring
Over the time, SINTEF develops a toolbox to deal with rock engineering challenges at different levels. The tool is a combination of three components "Investigation tools-Numerical modelling-Monitoring". Our investigation tools are including stress measurement, laboratory tests, and geological mapping. Stress measurements were carried out before and during construction phase of the project. The measurements included both 2-D and 3-D in relevant locations close to the concerned area. Laboratory tests for obtaining intact rock mechanics properties were carried out in connection with the stress measurements. Geological mapping was carried out to obtain the rock mass characteristics and conditions of the site [1]. The investigations provide inputs for the numerical model. Based on these inputs, a reliable numerical model can be established to provide information for further evaluation and decision-making. To increase the reliability of the model even further, it is then followed, verified, and improved along the way by communicating with monitoring equipment. Any discrepancy between the model and in-situ observation or monitoring data must be studied carefully in order to detect the pitfalls and possible improvement. A recommended working model for combining stress measurement, laboratory, numerical modelling, and monitoring is shown in Figure 2.

TRIPOD for development of the iron ore production at rana gruber, Norway
The Rana Gruber is an iron mine in the North of Norway, 30km east of Mo i Rana. The mine is located in a foliated gneiss host rock, and the ore body is about 70m wide and more than 300m deep. Different mining methods have been used, including open pit mining and sublevel stopping. Since 2009, the production has changed gradually to sublevel caving creating considerations in rock mechanic aspects. The TRIPOD was extensively used in this mine for almost last 10 years. The toolbox was considered as an important tool to assist the planning team during both planning and implementation of the mining method change at the mine. More than 18 stress measurements have been done over the years since 1977. Sixteen long-term-door-stoppers (LTDM) were installed at Copyright © Eivind Grøv AMMS.MS.ID.000599. 4(5).2020 critical locations to monitor the stress development in the rock mass during mining progress. The development and component of the LTDM was presented in Trinh et al. [2]. Two extensometers were installed to monitor the displacement at the footwall of the mine. Comprehensive 2D and 3D numerical models (Figure 3) were established to study the existing condition and to test different mining alternatives. With a meticulous follow-up program, the data from the monitoring equipment was used for model calibration and verification. The model was improved and become a reliable tool for planning and operation of the mine.