Proceedings of the Second International Conference on Underground Mining Technology最新文献

{"title":"Large seismic events (M > 0) in the Lappberget orebody, Garpenberg, Sweden: blast or non-blast-related?","authors":"I. Güclü, S. Dineva, S. Mozaffari, A. Nyström","doi":"10.36487/acg_repo/2035_06","DOIUrl":"https://doi.org/10.36487/acg_repo/2035_06","url":null,"abstract":"The definition of large magnitude events for mining-induced seismicity highly depends on the general pattern of seismicity in the underground mine. The seismic system in the underground Garpenberg Mine, located in Sweden, was installed in June 2012. In total, 40,000 events were recorded by the end of 2018 with the largest event of magnitude M 2.3. The large seismic events in Garpenberg Mine are defined as the events with M > 0 and very large events with M > 1. This study is based on data from the Lappberget orebody from 2012 to the end of 2018. \u0000A seismically active zone was defined in the Lappberget orebody on the northeast side with approximately 90% of the seismicity. The larger magnitude events occurred mostly in this zone too. The large events occurred at depth above 1,000 m, and the so-called very large seismic events, above 750 m. The events in the upper levels, above 700 m, are characterised by comparatively lower apparent stress than the events below. \u0000It was found that 24 % of the large seismic events were triggered by production blasts within 24 hours and 150 m. Most of the blast-related large events occurred within two hours after blasting. Only a few large seismic events had intense aftershocks. The aftershock series lasts for around 10 hours and are within 150 m of the main shock. In case of more a complicated situation with blast relation and multiple large events, the aftershock series lasts more than 60 hours. \u0000Based on the observations made here, some simple rules were defined for closing mine areas after large seismic events (so-called re-entry protocol for large seismic events). The reasonable restriction after the large seismic event would be three hours with a 150 m radius from the hypocentre of the large seismic event. The duration might be extended depending on the pattern of the aftershock sequence, especially for the large seismic events that occurred after blasting. In this case, the procedure of re-entry protocol for post-blast sequences must be followed. The obtained information about the relation between the large events and blasting can be used also for the re-entry protocol after blasting.","PeriodicalId":241197,"journal":{"name":"Proceedings of the Second International Conference on Underground Mining Technology","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130883000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Small-scale variations in mining-induced stresses, monitored in a seismically active underground mine","authors":"C. Dahnér, S. Dineva","doi":"10.36487/acg_repo/2035_09","DOIUrl":"https://doi.org/10.36487/acg_repo/2035_09","url":null,"abstract":"Kiirunavaara mine, owned by LKAB, is the largest iron ore underground mine. It is about 4 km long and has been mined with sublevel caving since the late 1950s. The current mining levels in the main orebody are 1079 m and 1108 m. The sublevel height is 29 m and it takes about two years to mine one sublevel in the southern half of the mine. As such, the mining-induced stress changes were regarded to be relatively slow. There are 2700 MW ≥ 0 seismic events recorded on average every year, with the largest event recorded on 18 May 2020 MW 4.3. \u0000Not many rock mechanical monitoring campaigns have been undertaken during the mine’s history, except for a mine-wide seismic system which has been in operation since 2009. In 2013, 3D stress measurements with the Borre stress cell were undertaken at level 1165 m (production area Block 34), with subsequent installation of 3D CSIRO-HI cells for long-term stress change monitoring. The primary purpose of the installation was to measure the changes in the induced stress (magnitude and direction) as the mining progressed downwards. The cell was installed 143 m below the current production level and at the time of the installation, there were indications that the measured stresses were already affected by the mining-induced stresses. At the time, the local stress state within different production areas was defined only by large-scale generic numerical modelling. \u0000Since the installation, large-scale changes in the induced stresses have been recorded. The current study is focussing on the small-scale variations in the induced stresses which can be related to larger seismic events, development, and production blasting for the time period mid-July 2015 to mid-March 2017. Stress changes before, during, and after 15 seismic events with mL ≥ 1.0 were analysed. Clear pattern of stress changes for eight events was found. No stress change was observed during 25 development blasts (distance < 50 m) and 19 closest productions blasts (125–135 m). Cyclic behaviour of the stress changes was observed with increases starting at 6:00 am which is most probably related to the shift/mucking start at this time. The stress change for a sample of data showed a striking similarity to the seismic activity in the area. \u0000The outcome of this work is part of the ongoing project to find patterns/scenarios which will be used for \u0000short-term hazard assessment and closing criteria in the mine. The results can be used also for further studies on seismic event preparation processes and co-seismic stresses and deformations.","PeriodicalId":241197,"journal":{"name":"Proceedings of the Second International Conference on Underground Mining Technology","volume":"128 9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115567154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fundamentals for cave back and in-ground monitoring using wireless technology","authors":"A. Aguirre, Jacob Lloyd","doi":"10.36487/acg_repo/2035_11","DOIUrl":"https://doi.org/10.36487/acg_repo/2035_11","url":null,"abstract":"The mining industry is pushing the boundaries in the application of cave mining with challenging ore bodies and ground conditions, production ramp-up, and higher throughput. With this, monitoring technologies need to progress to enable management of the associated geotechnical risks. Alongside recent advancements, wireless in-ground monitoring systems have emerged as a solution for monitoring ground stability and cave propagation in underground mining. Wireless in-ground monitoring can be used in a variety of monitoring scenarios where in-ground data collection is critical, such as cave back monitoring, mineral flow, cavinginduced subsidence and cave interaction with open pits and tailing dams. This paper provides an introduction for the design, installation, and application of a wireless in-ground system, Geo4Sight, and discusses this system’s operation, components, output data, interpretation, the determination of rock mass damage, and application thereof. This publication aims to provide an insight into the Geo4Sight system, and its relationship with ore flow monitoring (Cave Tracker System), highlighting the key aspects to consider for its correct application within the wider scheme of underground monitoring.","PeriodicalId":241197,"journal":{"name":"Proceedings of the Second International Conference on Underground Mining Technology","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128920293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crown pillar extraction with paste underhand stoping","authors":"A. Shiels, D. Sainsbury","doi":"10.36487/acg_repo/2035_08","DOIUrl":"https://doi.org/10.36487/acg_repo/2035_08","url":null,"abstract":"Technical investigations were conducted for extraction of a high-grade crown pillar in the northern 3500 orebody (N3500) at Glencore’s Mount Isa Mines using cemented paste backfill (CPB) underhand stoping. Several stopes have now been successfully extracted, achieving the planned recoveries with minimal dilution. \u0000In addition to standard CPB lab testing, in situ testing was conducted in the area planned for underhand exposure. The objective was to determine the variance between actual and design CPB strengths, to ensure the strengths were suitable for the planned underhand exposure dimensions. The testing results indicated the majority of in situ CPB strengths were higher than the lab cured and design strengths, due to the arching of stresses within the fill mass and curing processes. The strength parameters obtained from the testwork were incorporated in numerical modelling assessments using FLAC3D. Model calibrations were conducted using historical vertical CPB exposures to ensure the adopted methodology and material parameters were suitable. \u0000This paper discusses the methodology and results of the technical investigations, and how the data fed into analyses to assist with safe and efficient extraction of the crown pillar.","PeriodicalId":241197,"journal":{"name":"Proceedings of the Second International Conference on Underground Mining Technology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129398408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the accurate strain measurements for the crack initiation determination","authors":"Mutaz Mahmoud, M. Serati, David J. Williams, V. Nguyen","doi":"10.36487/acg_repo/2035_21","DOIUrl":"https://doi.org/10.36487/acg_repo/2035_21","url":null,"abstract":"Due to the huge demand for natural resources and minerals at a global scale, mining depths have progressively increased over the past decades to 1,000 m and deeper. However, despite many successes, deep mining operations are now facing new challenges never experienced before, including rock spalling and unwanted slabbing failures. This phenomenon is characterised as a sudden explosion-like fracture, which can affect the long-term viability and stability of deep underground mining. According to the literature, the most indicative predictor of the spalling strength at laboratory scale is the determination of the crack initiation point, which is defined as the onset of stress-induced damage in low-porosity rocks after the closure of pre-existing cracks. Hence, many methods have been developed to identify this critical design parameter, based mainly on the measurement of vertical, lateral or volumetric strains. That is, an accurate measurement of strain is deemed critical in determining the onset of the crack initiation threshold in the study of rock failure. Nevertheless, it remains difficult to determine the actual sample deformation in many geotechnical test apparatuses (i.e. multi-stage triaxial, Hoek cell, true triaxial, etc.), in which the measured deformation by linear variable differential transformers (LVDTs) is the cumulative deformation of the load frame itself, the loading platens, and the sample. As a result, relying on these deformation measurements can lead to erroneous estimation of the material’s strain behaviour. This work presents a qualitative study on how to measure the actual sample deformation in a multi-functional true triaxial testing apparatus recently commissioned at the Geotechnical Engineering Centre (GEC) within the School of Civil Engineering at The University of Queensland (Brisbane, Australia).","PeriodicalId":241197,"journal":{"name":"Proceedings of the Second International Conference on Underground Mining Technology","volume":"145 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114755664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}