Reports from Swebrec
For access to the report contact: Professor Daniel Johansson, Director of Swebrec
3D mapping of sublevel caving (SLC) blast rings
- flow disturbances in the LKAB Kiruna mine
The 3D image acquisition system has proven to be a valuable tool in increasing the understanding of SLC breakage and flow by revealing and quantifying hitherto inaccessible information about openings and hang-ups. With 30 surveyed SLC ring blasts in openings there is now a reasonably large data for a comprehensive analysis of the blast results. The scaling up of SLC rings during adaption to the ore contact closest to the hanging wall constitutes a difficult blasting situation.
Burden movement while blasting under constraints
– Tests with new gauges in block 9, 741 m level, Kiruna mine
This study is a continuation of the confined drift wall blasting tests at block 12, 691 m level (Wimmer & Ouchterlony, 2011). The report summarizes the development of a system to measure burden movement. This system could be installed from behind the production rings in sublevel caving (SLC).
Study of burden movement in confined drift wall blasting tests
- Block 12, 691 m level, Kiruna mine
The present report summarizes tests of various techniques developed to study the burden movement in confined drift wall blasting. In the future these methods should be transferred and implemented in fullscale blasting of production rings. This work is part of the Hjalmar Lundbohm Research Centre (HLRC) project “Improved breakage and flow in sublevel caving (SLC)”.
Gravity flow of broken rock in sublevel caving (SLC)
– State-of-the-art
This report surveys the state-of-the art of gravity flow in sublevel caving (SLC). The principles of SLC operations are firstly explained as well as factors influencing gravity flow behaviour of blasted and caved rock.Thereafter, flow of broken rock is highlighted from a modelling perspective. The traditional ellipsoid approach and its later modifications are firstly reviewed. Common modern modelling approaches are surveyed. Small- and full-scale experimental studies are presented in detail with respect to their actual performance and outcomes.
2D image analysis using WipFrag software compared with actual sieving data of Kiruna
- Magnetite loaded from a drawpoint
The objective of this study is to compare actual fragmentation data from a full-scale test sieving campaign with images evaluated by using the granulometry analysis software WipFrag.
The input data is summarized as follows:
- 6 individual samples taken at an SLC draw point at 7.5 % extraction rate;
- Images from buckets (underground) and piles spread and re-mixed (on the surface);
- Image resolution 640 x 480 and 1600 x 1200 pixels;
- Manual delineation and automatic net delineation using LKAB`s standard parameters.
To quantify the results of the WipFrag evaluation its derived percentile sizes (x25, x50, xc, x75 and x90) were compared with the percentiles from full-scale sieving for the respective sample.
The fragment size distribution of Kiruna magnetite loaded from a draw point
Evaluation and analysis of a full-scale test
The objective of this investigation was to find out whether the Kiruna magnetite behaves like waste rock from a blasting point of view. Our main conclusion is that the magnetite qualitatively behaves like waste rock from a blasting point of view. To do this we conducted a full-scale study of the fragmentation characteristics for blasted magnetite ore from the SLC operation in Kiruna. For comparison we had access to model scale blasting data, laboratory scale crushing and milling data, and historical full-scale data from the mine, albeit when the scale of the SLC levels was much smaller than at the time of the investigation.
Tunnel blast design for minimizing of the damage zone
- A guidance document for SKB and Posiva
The question of an existing continuous Excavation Damage Zone (EDZ) is very important for Posiva and SKB. Is it possible to use drilling and blasting in the planned repository for spent nuclear fuel?
Could fractures from blasting form a continuous EDZ? Posiva and SKB have both recently carried out special tunnel projects to in more detail study different drilling and charging methods and how they affect the damage zone. In the planning of the tunnels and during the tunnel operations results from previous research at Swebrec was used. The purpose of this study is to make a guidance document primarily for design aspects and to some extent the quality issues that are important for minimizing the blast damage in a tunnel contour. The purpose of the report is not to deliver perfect solutions but to contribute to making Posiva and SKB become clients.
Fragmentation in production rounds and mill throughput in the Aitik mine
- A summary of development projects 2002-2009
This report summarizes R&D work made at the Boliden Mineral Aitik mine in cooperation with Swebrec.
Aitik has been driven by the goal to increase the throughput in the primary mills. This was done in the in-house projects M2M and G5 Optimized blasting. Swebrec has supported this by developing new knowledge about the blasting and crushing in associated projects.
Swebrec has conducted special studies on three rounds: no. 4141-2, 5153 and 5162 with different combinations of normal and high specific charge in the parts. We have focused on a better description of the blast fragmentation by combining measurements with Split Desktop with lab-sieving of muckpile samples for the different parts. For round 5162 the material was followed through the crusher.
Evaluation of two layers cylinder tests: Experiments and FEM simulation
An experimental study regarding a model material’s ability to absorb energy during blasting has been carried out.
The tests were performed using copper pipes with a wall thickness of 5,0 mm and an inner diameter of 100 mm. An inner layer of mortar was cured inside the copper pipes, reducing the inner diameter to 44,5 mm. The plastic explosive NSP 711 was used for the tests, which from our viewpoint is considered to detonate ideally. The displacements of the copper pipe were registered at several locations during the tests.
FEM simulations were conducted based on the test set up, and the calculated displacements of the copper pipe were compared with the displacements obtained from the tests. The input data for grout and copper in the simulations were adjusted until a fair agreement was obtained between simulation results and test data. The simulations are thereafter used to estimate the transmitted energy to the mortar and the copper pipe.
Determination of the Gurney- and detonation energy for emulsion explosives
- with help of cylinder test
Nine cylinder tests for emulsion explosives in expanding Ø100/110 mm copper tubes are re-ported. The explosive recipe for pure emulsion respectively for blend of ANFO/AN-prills was formulated specifically for Swebrec:s test program.The primary goal was to verify earlier determinations of the explosive energy. In addition, re-cordings from streak camera and data from contact pins was evaluated for copper tubes 350 mm long and Ø60/72 mm filled with FOX12/TNT.
Controlled fragmentation in sublevel caving - first tests
This report describes some tests made in order to examine a number of important factors in sublevel caving.
Among these factors were back-break, influence of a neighbour hole, rock movements in caving and the effect of compacted rock. Measurements of the straightness of the holes were done. The detonation velocity was measured and the four rounds were high speed filmed. The position of the bench front before and after blasting was measured with stereo photogrammetric technique.
Application of borehole geophysics to identify variations in sublevel caving (SLC) debris
– Field tests in drifts filled with ore and waste
The objective of this study is to evaluate the technical feasibility of using geophysical borehole methods to detect magnetite ore residues within caving debris in the sublevel caving mine at Kiruna.
Gravity flow mechanisms are studied with the aim of improving ore recovery and decreasing waste rock dilution. For this purpose a test site which was as realistic as possible was arranged. This test site provides models of different iron ore remains within the caving flow. Alternate heaps of broken waste rock, magnetite ore and a mixture of both containing various boulders were built up in two adjacent drifts. PVC pipes were embedded in the heaps with ends protruding. Geophysical borehole probes were later inserted in the pipes to log events.
Application of time domain reflectometry (TDR) for block and sublevel caving mines
– State-of-the-art and preliminary laboratory shear tests
The Objective of the present report is to summarize the state-of-the-art of the application of time domain reflectometry (TDR) with Regard to its application to block and sublevel caving mines.
A second Objective is to report on preliminary laboratory shear tests in Which a grouted cable was exposed to a controlled shear movement in a plane inclined relative to the cable.
JointMetriX3D Imaging
his report is a guide for the evaluation of three-dimensional images using the analysis program, JointMetriX3D Imaging.
The report complements the report "JointMetriX3D Imaging" by Andreas Gaich (2004) and is a result of our experiences from the analysis of images from a wall of blast 4141-2 in Aitik mine in 2004. The tutorial will make analyzing the program easy to use and is designed to make the evaluation, at best, regardless of the operator.
Monitoring the fragmentation in blast
- 4141-2 in the Aitik mine
This report is a part of the reporting of the Swebrec project “ Model for bench blasting and primary crusher in an opencast mine 2.2”. The project is part of Swebrec’s research program sponsored and by Atlas Copco, Boliden, Dyno Nobel, Kimit, LKAB and Nordkalk. Swebrec belongs to Luleå University of Technology. The project was accomplished in close cooperation with the personnel at Bolden’s Aitik mine, Gällivare where the field test was located.
The goal is to increase the throughput of the mills. To achieve this, there is a need for better geological models and a better description of the blasting in different geological domains. The over all task for Swebrec in this project, is to contribute with new knowledge, to map and document test blasts and monitor fragmentation, for future recommendations on the control of the fragmentation. In this step, Swebrec followed the fragmentation up to the primary crusher. For the time being we have no possibility to trace the ore through the ore storage.
In a preparatory step, an investigation was made to find out if mapping of the front with help of 3- dimensional images would give usable geological information as input data to fragmentation models.
This step is reported in the supplementary report ”Strukturkartering av Salva 4141-2 i Aitikgruvan”.
Determination of the energetic characteristics of commercial explosives
- using the cylinder expansion test technique
The cylinder expansion test technique has been a principal testing technique for the determination of energetics of commercial explosives at Swebrec. The aims of this project are to evaluate the work capacity of commercial explosives, compare the products, judge the addition of Aluminum into ANFO and emulsion explosives, assess the addition of ANFO into emulsion explosives, compare the test results with the underwater test and full-scale results as well as determine the usefulness of the cylinder test in the mining and quarrying industry.
This report presents the comprehensive cylinder expansion tests collected to date. 58 cylinder tests were carried out during the period from January 2002 to January 2005. A total of 11 commercial type explosives have been tested during this period at charge diameters between 40 and 100 mm in copper pipes. The explosives ranged from pure ANFO to pure emulsions and covered the majority of the commercial explosive types used in today’s production blasting operations. In addition to the previous in-house data, 9 more cylinder tests were conducted between August 2005 and November 2005.
The capacity of image analysis to measure fragmentation, an evaluation using Split Desktop®
This report is about the capacity of image analysis to measure fragmentation by blasting.
It is motivated by the need to make the measurements without disturbing production, i.e. in practice without contact. Analysis of digital images with scales has become the most used method. There are several commercial programs. In Swebrec’s project 2.7 The capacity of image analysis to measure fragmentation the program Split Desktop® has been used. This program is suitable for measuring the fragmentation of muckpiles.
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