Karaganda State Technical University, Karaganda, Kazakhstan:

F. K. Nizametdinov, Professor, Doctor of Engineering Sciences, niz36@mail.ru
N. F. Nizametdinov, Associate Professor, Candidate of Engineering Sciences
R. F. Nizametdinov, Associate Professor, Candidate of Engineering Sciences
A. O. Oralbai, Doctoral Student

The current trend in open pit mineral mining is the increased recovery of nonferrous metals by heap leaching of oxidized ore on the shallow horizons. This article presents the case-study of Aktogai open pit copper mine having the project depth to 500 m. To implement heap leaching, ore stockpiling is carried out on ground surface, on a weak clayey and slightly sloped bottom, by layers 12–15 m high. The proposed instrumental monitoring procedure for the stockpiles in the heap leaching area uses a pillar of improved design, arranged below the depth of freezing and outside the potential displacement zone for the installation of an electronic tacheometer and check points with optical reflectors, stiffly bound with the ore stockpile using concrete. The high-precision geodetic measurements allow surveying in a single vertical plane using the check points arranged in the profile cross-section in the area of heap leaching. The values of displacements are determined both in vertical and horizontal planes of the ore stockpile. It is found that the stockpile body undergoes continuous compaction due to the permanent addition of new layers. The deformation mechanism of the stockpile is governed by the continuous stress, which is proved by the displacement values of the check points. In the middle of the stockpile, continuous compaction takes place at a rate up to 7.07 mm/day, while at the slope bottom of the stockpile, slight horizontal displacements toward the support pillar are observed at a rate to 4.90 mm/day. According to the current guidance procedures, such rates of displacement are not hazardous for the production process, as the threshold is 10 mm/day, but continuous instrumental monitoring of the ore stockpile stability in the heap leaching areas is required to reveal maximum allowable displacements and prevent landsliding.

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