Punktlasttestning av olika bergartstyper i Kiirunavaaras liggvägg
Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
The degree project is the final part of the education for Bachelor of Science with major natural resources engineering. The program is focused on geology and the final project, 15 credits, will be related to the topic. In the spring of 2012 representatives from LKAB proposed to base the thesis on documenting the strength of rocks from Kiirunavaara footwall, using point load strength tests. Previous investigations of the strength of rocks in Kiirunavaara have mainly been done by uniaxial compressive strength measurements.The strength of the rocks in Kiirunavaara needs to be studied when underground mining proceeds deeper in the crust and the requirements of safety is ever increasing. Sublevel caving is used for mining the Kiirunavaara ore and facilities for conveying, roads, crushers, etc. are located on the footwall side of the ore, which requires stability and sustainable designs. The footwall consists of relatively massive rocks of trachytic to trachyandesitic composition, with varying textural features and mineralogical compositions. Previous strength investigations of the rocks have been made, but these should be complemented by more comprehensive studies, especially low-strength rocks more carefully documented. The aim of the study was to examine the strength of various geologically well-defined rocks in Kiirunavaara footwall by using the point load strength index. The study also intended to examine whether the method of point load testing on irregular lumps could be used to obtain reliable rock strength results.The Point Load Strength Test is a simple test that can be performed with portable equipment, conducted in the field to quickly assess the strength of rock samples. It can also be performed on irregular samples which require minimal preparation. Other tests for examining the uniaxial compressive strength are often time consuming and expensive. Point load testing may therefore be a simple, less expensive method to estimate the rock strength for a large number of rocks, also applicable in the field.The study is based on 138 irregularly shaped rock samples, all tested by point load testing. Sampling of the footwall rock took place at levels of about 900-1500 meters (LKAB's local coordinate system), from north to south, all along the approximately 4 kilometer long Kiirunavaara ore body. The samples were divided into eight groups, mainly according to the geological variations. Macroscopic characters where documented. 21 samples were also examined by transmitted-light optical microscopy. The results show large strength variations between the rock groups. The corrected point load strength index varied in total from 0.92 MPa to 17.56 MPa, with an avarage of 8.97±3.28 MPa. Highest average value where obtained for unaltered syenite porphyry, 12.46±1.97 MPa, and the lowest for chlorite- and clay altered syenite, 3.15± 0.71 MPa. The avarage values of the other groups ranged from 7.93±1.85 MPa to 9.87±2.03 MPa. The methodology of point load testing was evaluated by statistically analyzing the size correction, as this is an important parameter for the result. The results were also compared with previous uniaxial compressive strength tests made on Kiirunavaara rocks, where similar variations in the results were observed.
Place, publisher, year, edition, pages
2013. , 107 p.
Life Earth Science
Bio- och geovetenskaper, Punktlasttest, Kiirunavaara, hållfasthet, bergarter, irregular lumps, point load strength index, mikroskopering, liggvägg, enaxiella tryckhållfasthet, geologi, oregelbundna prov, rock strength, uniaxial compressive strength, geology, the point load strength test, punktlasttestning, storlekskorrigering
IdentifiersURN: urn:nbn:se:ltu:diva-43355Local ID: 13cc911c-7049-4af7-aeed-b8bea2f9c76eOAI: oai:DiVA.org:ltu-43355DiVA: diva2:1016586
Subject / course
Student thesis, at least 15 credits
Natural Resources Engineering, bachelor's level
Validerat; 20130203 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved