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Measurements of cutter forces and cutter temperature of boring machine in Äspö Hard Rock Laboratory
Luleå tekniska universitet.
Luleå tekniska universitet.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
2001 (English)Report (Other academic)
Abstract [en]

This report presents both the testing methods used and the testing results obtained for cutter forces and cutter temperature during field boring in Äspö Hard Rock Laboratory. In order to estimate the strains induced by cutter forces in the cutter shaft and choose proper transducers, first a numerical simulation was performed. The simulation results indicated that the cutter forces should be measurable by ordinary strain gauges. Furthermore, an independent three-direction loading system for laboratory calibration was set up to solve force-coupling problems appearing in field measurements. By means of the established measuring system, which was proved successful in the laboratory, the normal forces, tangential forces, and side forces of two button cutters in the boring machine were measured in the field. In addition, the temperature in the shaft of the front cutter was measured. After the measurements of the cutter forces and cutter temperature, rock core samples were taken from the bottom and the wall of the testing borehole. Then the samples were cut, polished, and examined by means of the Scanning Electron Microscope (SEM). After that, the lengths of major cracks induced by the cutters in the rock samples were measured, and an approximate relationship between the length of the medium cracks and the relevant cutter forces was obtained. This relationship was compared with the theoretical relationship established before. Finally, according to the measured results, the cracked zones around the borehole were described. The results show that: (1) there are two kinds of cracked zones: one in the borehole wall and the other in the bottom of the borehole. The depth of the cracked zone in the borehole bottom is much larger than that in the borehole wall because the maximum normal force of the front cutter is always much larger than that of the gauge cutter. (2) Each cracked zone includes a densely cracked zone and all the longest medium cracks caused by mechanical boring. (3) According to the measurements for four rock core samples, the maximum depth of the cracked zone in the borehole bottom is 27.1 mm, and the maximum depth of the densely cracked zone is 2.5-3 mm.

Abstract [sv]

I denna rapport presenteras både testmetoder och resultat från mätning av verktygskrafter och temperatur under fullborrning av schakt i Äspölaboratoriet.För att bedöma deformationer som induceras i axlarna på verktygen (cutters) och för rätt val av kraftgivare genomfördes numeriska beräkningar. Dessa visade att vanliga trådtöjningsgivare kunde användas. Ett system med oberoende belastning i tre riktningar för kalibrering i laboratorium av kraftgivare monterades för att lösa problemet med koppling mellan givare under fältmätningen. Med hjälp av det därpå utvecklade mätsystemet, som testades i laboratorium, mättes normalkraft, tangentiell kraft och sidokraft på två verktyg i fält. Dessutom mättes temperaturen i axeln på ett av verktygen i fronten på borrhuvudet. Efter mätning av verktygskrafter och temperatur, uttogs borrkärnor från botten och väggar på det schakt som borrats. Proverna sågades, polerades och undersöktes i svepelektronmikroskop. Längden på sprickor som uppstått under verktygen mättes och ett approximativt samband mellan längden på mediansprickor och relevanta verktygskrafter kunde skapas. Detta samband jämfördes med teoretiska samband som etablerats tidigare. Slutligen kunde, utgående från de erhållna resultaten, den spruckna zonen omkring schaktet beskrivas. Resultaten visar att: (1) två olika sprickzoner kan utskiljas: en i väggarna och en i botten på schaktet. Djupet på den uppspruckna zonen i botten är mycket större än i väggarna på schaktet beroende på att den maximala normalkraften på verktyg riktat framåt (front cutter) alltid är mycket högre än på verktyget mot väggen (gauge cutter). (2) Varje sprickzon inkluderar dels en kraftigt uppsprucken zon dels glest liggande, långa mediansprickor. (3) Från mätningen av fyra bergprover har maximala djupet på mediansprickor i schaktbotten uppmätts till 27,1 mm och maximala djupet på den kraftigt uppspruckna zonen till 2,5-3,0 mm.

Place, publisher, year, edition, pages
Stockholm: Svensk kärnbränslehantering AB , 2001. , 95 p.
Series
Technical report / Svensk kärnbränslehantering AB, ISSN 1404-0344 ; TR-01-34
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-25404Local ID: f0c79370-9cb0-11db-8975-000ea68e967bOAI: oai:DiVA.org:ltu-25404DiVA: diva2:998456
Note
Godkänd; 2001; 20070105 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

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