Erol Yilmaz

The effect of desliming by sedimentation on paste backfill performance

Abstract One of the most important characteristics of a backfill material is the particle size distribution. In this paper, the authors have focused the effect of deslimed mill tailings on paste backfill performance at a copper–zinc mine in northeast Turkey. The use of sedimentation methods to deslime has a widespread utilisation and regarded as a true fractional size analysis practice. The common laboratory method of beaker decantation was used for desliming in order to determine the optimum particle size distribution. For studying the beaker decantation, two mine tailings, namely tailings samples A and B are used which have particles 52 and 54 wt.% finer than 20 μm, respectively. The fines content (−20 μm) of each tailing were reduced to 15, 20, 25 and 30 wt.% via desliming. Deslimed tailings then were tested to investigate the relationship between particle size and strength gain. It was found that strength ranges of the deslimed tailings were from 12% to 52% higher than as-received mill tailings.

Assessment of the Modified CUAPS Apparatus to Estimate In Situ Properties of Cemented Paste Backfill

This paper evaluates some improvements in the design of a laboratory apparatus called curing under applied pressure system (CUAPS) designed to estimate in situ properties of cemented paste backfill (CPB). This apparatus is effective in conducting the following tests on samples during curing: (i) One-dimensional consolidation test with or without pore water pressure (PWP) measurement, (ii) PWP dissipation test, (iii) saturated hydraulic conductivity (permeability) test, and (iv) curing under constant or variable vertical pressure. Unconfined compression tests can be also performed on consolidated CPB samples after each of these tests. The modified CUAPS apparatus is assessed in this paper. Preliminary results are promising and validate the functionality of the CUAPS apparatus, which will contribute to the knowledge on consolidation behaviour of in situ CPB material.

Stope depth effect on field behaviour and performance of cemented paste backfills

Abstract Cemented paste backfill (CPB) has been extensively used as a popular mine fill system for underground mining operations. Understanding the CPB’s in situ properties as an element of ground support is indeed really important for developing a well-organised mine design in terms of costs and security. In this paper, a comprehensive experimental work was conducted to better understand the effect of stope depth on in situ behaviour and performance of CPB having three different binding agents (ordinary Portland cement alone, slag-based cement and fly ash-based cement) over different curing times. A stope depth of 0 (it replicates the stope’s top), 5, 10, 15 and 20 m (it replicates the stope’s bottom) were virtually simulated by using an improved laboratory set-up, escorting with conventional plastic moulds. Results show that the highest compressive strength is obtained from CPB having slag-based cement. The strength of CPB increases with increasing stope depth mainly due to resulting improved geotechnical properties, such as reduced water content, degree of saturation and porosity as well as increased specific surface area retained at the bottom of a simulated stope. Geochemical testing shows that sulphate SO4−2 and calcium Ca contents increase with increasing curing time and reduce with increasing stope depth. As a critical point, a number of experimental relationships considered typically for different curing times, overburden pressure, arching stress and binder contents within CPB material were expressed and discussed.

Cayeli Paste Backfill System and Operations

This chapter presents an overview of the Cayeli paste backfill system and operations. Cemented paste backfill (CPB) has been in use at the mine since 1999 and is a critical component of the underground mining operations. Since start up, more than 3.5 million m3 of CPB has been successfully placed into the mined-out underground stopes. Cemented stope pillars have proven to be stable and allow 100% extraction of secondary stopes. Cayeli has well established procedures, a good quality assurance/ quality control program, efficient plant maintenance, and ongoing continuous improvement program to better assess methods of improving the performance and reducing the CPB costs. All aspects including mining methods, paste fill plant, reticulation system, and backfill strategy and applications are given in this chapter.

Introduction to Paste Tailings Management

This chapter focuses on problem statement about mining tailings treatment and management. It also gives the key definitions of two tailings management methods: cemented paste backfill (CPB) and surface paste disposal SPD. Paste technology is widely considered as an emerging technique to assess mining wastes in an environmentally sound way. Sulphidic tailings mixed with cements and water are often defined as CPB and used to re-fill mined stopes, resulting in a maximum extraction rate from an underground ore deposit. In addition, SPD promises an attractive technology and viable solutions for tailings treatment. The water come from tailings is recovered and can be used repeatedly while the requirement of constructing the big tailings dams at surface can be minimized using paste technology. These new techniques have been explained in detail in this chapter from the industrial application point of view.

Design and Characterization of Underground Paste Backfill

This chapter describes the design and characterization of cemented paste backfill considered for re-filling underground mined-out stopes. The mixture design and optimization of CPB are based on laboratory- and paste plant-scale testing. The uniaxial compressive strength of paste backfill material is universally accepted as one of the most important design parameters. The other design parameters are material characterization, dewatering and rheological properties. To reach the real strength response of a paste-filled stope based on an optimal stability design, it is vital to assess the intrinsic (paste ingredients) and extrinsic factors (field placement and curing conditions) which affects the CPB’s performance. This chapter deals an overview of underground paste backfilling, including paste ingredients, backfill plant operations, mixture preparation, backfill reticulation system, paste placement and curing conditions, barricade construction and monitoring, and quality control testing.

Cemented Paste Backfill Pressure Monitoring and Field Testing

This chapter covers a brief statement of the pressure monitoring and field testing of cemented paste backfill used in the Cayeli mine. Two stopes were instrumented at different locations. The total, pore pressures and temperature of paste backfill during and after stope filling were monitored for both in-stope and barricade. To assess the overall structural stability of CPB as regional and local support, the strength development of paste-backfilled stopes is measured by core samples. The backfill’s field performance is of great importance in designing an efficient and more completive paste backfill. The CPB design is mostly based on the laboratory results but forever undervalue the events occurring at underground paste-filled stopes. This section gives more details on field behavior and characteristic of paste backfill.