Abstract

Mining is a high risk business and for every modern mining industry, the main aim of its open pit design is to create walls that will be stable for the life of the open pit, which in some cases may extend beyond the closure. As a result, any kind of instability should be manageable and if possible, it should not develop to instabilities. This paper focuses on 300.000 tons instability that began in 2008 and continues until today in Titania. The hazard associated with this instability was a constant threat for the continuation of the production and the safety of people and machinery. In order to manage the hazard in short- and long-term, it was evident that data from different sources should be combined and analyzed. Data from ground-based and satellite SAR were used to delineate the unstable area through a period of 10 years. At the same time advanced implicit modelling techniques were used to integrate borehole and surface structural data in a 3D structural model. This 2 stage workflow, led to a set of preventive and remedial measures that allowed the continuation of the production the last ten years and will ensure the continuation of the production for, at least, other ten years.

Introduction

Titania AS has undertaken an extensive project of identifying the geohazards that could lead to slope instabilities of different scales. The fundamental stage was to compile a 3D structural model of the open pit. Monitoring data from ground-based radars and satellite SAR were used to give a holistic view of the unstable area. Remediation and early warning strategies are commonly based on continuous monitoring of the slope displacement which can give crucial information on the dynamics and evolution of the landslide [1]. Integrating data from different sources is leading to the depiction of the event controlling parameters and the delineation of their effect on the phenomenon’s evolution.

The open pit and its geotechnical conditions
The Tellnes mine

The Tellnes mine is located in south-western Norway, between the towns of Egersund and Flekkefjord in Sokndal municipality. It is an open pit mine, producing ilmenite from an ilmenite-rich norite. As per today, the mine is ca 2700 m long, 700 m wide and has a depth of ca 300 m at the most. Initial bench height of 15 m is used during mining, which is later doubled to 30 m in the final pit design, yielding an overall slope angle between 45 and 55 degrees.

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