Abstract

The article studies the fatures of stress distribution around the mining excavations under different tectonic loads on the case study of the Zhdanovskoe copper-nickel ore deposit, Murmansk region, Russia. The deposit is located in the Arctic zone on the Russia-Norway state boundary and is excavated by the Severny underground mine using simultaneously the sublevel caving and the open stoping methods. The combination of these mining methods in the same area affects the geomechanical conditions; moreover, the highest level of stresses is identified between the opposing excavation fronts. The deepening of mining increases the geodynamic risks caused by the stress state in the rock mass. In this regard, the study of the Zhdanovskoe deposit rock mass stress state and its transformation due to the mining progress is urgent. To address the issues a numerical geomechanical 3D model was created. To specify the correct boundary conditions, the results of the in-situ measurements were compared to visual observation results. To achieve the most accurate result, the direction and ratio of the tectonic loads were varied and the results were analyzed. The authors have analysed the modelling results in the form of the stresses and deformations distribution in the area around the excavations under different directions of tectonic loads. Based on this analysis, the authors have substantiated a relevant variant of direction of tectonic forces relatively the ore body strike. The results have been applied to forecast the changes in perspective stress-strain state during the mining progress.

Introduction

The Zhdanovskoe deposit is located on the eastern flank of the Pechenga ore field, which is located in the northeastern part of the Kola Peninsula, Russia (figure 1). The location of the Zhdanovskoe deposit is shown in figure 1. The deposit was explored in the early 20th century, and its commercial development bedding plane began in the 1960s [1]. The deposit includes several ore bodies: Tsentralnoe, Zapadnoe, Yugo-Zapadnoe-1 Yugo-Zapadnoe-2, Vostochnoe and Yugo-Vostochnoe ore bodies (Eremenko 2010) ( figure 2). All the ore bodies are bedded plane shaped with the average dip angle is about 50°. The Tsentralnoe ore body is the largest in terms of reserves. Initially, the Zhdanovskoe deposit was exploited by open-pit mining, but in 2010, the transition to underground mining started [2]. The Zhdanovskoe deposit is currently fully mined by the Severny underground mine of the Kola MMC.

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