Design of equipment for dynamic burden measurements

• The flowability of the caved rock masses in the sublevel caving (SLC) mining method is of greatimportance. During the blasting process of a SLC-ring, the caved rock mass in front of the ring iscompacted. As a result of this compaction, the mechanical properties of the fractured rock masseschange, for example void ratio, angle of internal friction and structure of the compacted material.The changed mechanical properties of caved rock mass and recent blasted material can influencethe mobility of the material, which could result in blockage of the flow path of the material.The identification of the involved mechanisms in this process can be done after a series of testsin different scales. However, there is no available equipment for dynamic measurements duringblasting, ie velocity and displacement of the burden and in the caved masses. This study focuses onthe development and laboratory evaluation of a measuring system that can be installed in a borehole.The first trial was carried out in a pillar, where two blastholes had been drilled (9.5 m) parallel withthe drift and two measuring holes (16.5 m) were perpendicular to the drift. Two measuring systemswere installed in the measuring holes. Some preliminary tests were carried out to find suitableinitiation procedures for the emulsion explosive. Applicability and robustness of the developedmeasuring system were also evaluated. In addition to these tests, an expandable cement mixture wasdeveloped to firmly anchor the measuring systems in the boreholes. The measuring system consistsof an anchor, armoured cable in a pulling tube and a protective case. The anchor is equipped withuniaxial and triaxial accelerometers. A potentiometric measuring system for displacement up to 2 mis installed at the end of the pulling tube and connected to an extendable spiral cable. All sensorsare connected to a data acquisition system (DAS). Both measuring systems have their own DAS toacquire data in case of failure of one of the systems. The measuring system was tested in laboratoryconditions with impact velocity up to 10 m/s. It was proven to be functional and gave reliable results.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Annan samhällsbyggnadsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Other Civil Engineering (hsv//eng)

Keyword

Gruv- och Berganläggningsteknik

Mining and Rock Engineering

Publication and Content Type

ref (subject category)

kon (subject category)