1、PDF外文：http:/ 中文 6340 字 出处： Journal of Cleaner Production, 2006, 14(12): 1168-1175 英文原文 Geotechnical considerations in mine backfilling in Australia N. Sivakugan a,*,R.M. Rankine b, K.J. Rankine a, K.S. Rankine a a School of Engineering, James Cook University, Townsville 4811, Australia b
2、 Cannington Mine, BHP Billiton, P.O. Box 5874, Townsville 4810, Australia Abstract :Mine backfilling can play a significant role in the overall operation of a mine operation. In the Australian mining industry, where safety is a prime consideration, hydraulic systems are the most common backfills dep
3、loyed.Many accidents reported at hydraulic fill mines worldwide have mainly been attributed to a lack of understanding of their behaviour and barricade bricks.This paper describes the findings from an extensive laboratory test programme carried out in Australia on more than 20 different hydraulic fi
4、lls and several barricade bricks. A limited description of paste backfills is also provided, and the usefulness of numerical modelling as an investigative tool is highlighted. Keywords: Hydraulic fills； Mining； Backfills； Paste fills； Geotechnical 1 Introduction In the mining industry, when un
5、derground ore bodies are extracted, very large voids are created, which must be backfilled. The backfilling strategies deployed often make use of the waste rock or tailings that are considered by-products of the mining operation. This is an effective means of tailing disposal because it negates the
6、need for constructing large tailing dams at the surface. The backfilling of underground voids also improves local and regional stability, enabling safer and more efficient mining of the surrounding areas. The need for backfilling is a major issue in Australia, where 10 million cubic metres of underg
7、round voids are generated annually as a result of mining 1. There are two basic types of backfilling strategies. The first, uncemented backfilling, does not make use of binding agents such as cement, and their characteristics can be studied using soil mechanics theories. A typical example of u
8、ncemented backfilling is the use of hydraulic fills that are placed in the form of slurry into the underground voids. The second category, cemented backfilling, makes use of a small percentage of binder such as Portland cement or a blend of Portland cement with another pozzolan such as fly ash, gyps
9、um or blast furnace slag. The purpose of this paper is to analyse the findings from an extensive laboratory test programme carried out in Australia on hydraulic fills and several barricade bricks. Hydraulic fills are uncemented techniques, and are one of the most widely used backfilling strate
10、gies in Australia. More than 20 different hydraulic fills, representing a wide range of mines in Australia, were studied at James Cook University (JCU). The grain sizer distributions for all of these fills lie within a narrow band as shown in Fig. 1. Along with them, the grain size distribution curv
11、es for a paste fill and a cemented hydraulic fill are also shown. It can be seen that the cemented hydraulic fill falls within the same band as the hydraulic fill. The addition of a very small percentage of cement has a limited effect on grain size distribution. Paste fills generally have a mu
12、ch larger fine fraction than hydraulic fills or cemented hydraulic fills, but have negligible colloidal fraction finer than 2 m. Fig. 1. Typical grain size distribution curves for hydraulic fills,cemented hydraulic fills and paste fills. 2 Hydraulic backfills Hydraulic fills are simply silty
13、sands or sandy silts without clay fraction, and are classified as ML or SM under the Unified Soil Classification System. The clay fraction is removed through a process known as desliming, whereby the entire fill material is circulated through hydrocyclones and the fine fraction is removed and then s
14、ent to the tailings dam. The remaining hydraulic fill fraction is reticulated in the form of slurry through pipelines to underground voids. Over the past decade there has been a steady increase in the solid content of the hydraulic fill slurry placed in mines in an attempt to reduce the quanti
15、ty of water that must be drained and increase the proportion of solids. The challenge posed by a high solid content is that it becomes difficult to transport the slurry through the pipelines due to rheological considerations. Currently, solid contents of 75-80% are common, although even at 75% solid
16、 content, assuming a specific gravity of 3.00 for the solid grains, 50% of slurry volume is water. Therefore, there is opportunity for a substantial amount of water to be drained from the hydraulic fill stope. To contain the fill, the horizontal access drives created during mining are generall
17、y blocked by barricades constructed from specially made porous bricks (Fig. 2). Fig. 2. An idealised stope with two sublevel drains. The access drives, which are made large enough to permit the entry of machinery during mining, are blocked by the barricades during filling. The drives are ofte
18、n located at more than one level. Initially, the drives located at upper levels act as exit points for the decanted water, and also serve as drains when the hydraulic fill rises in the stope. 2.1 Drainage considerations Drainage is the most important issue that must be considered when designin
19、g hydraulic fill stopes. There have been several accidents (namely, trapped miners and machinery) worldwide caused by wet hydraulic fill rushing through horizontal access drives. Several reasons, including poor quality barricade bricks, liquefaction, and piping within the hydraulic fill are attribut
20、ed to such failures 2. Therefore, permeability of the hydraulic fill in the stope is a critical parameter in the design； continuous effort is made during mining to ensure that it is kept above a threshold limit in the vicinity of 100 mm/h 3. Larger permeability leads to quicker removal of water from
21、 the stope, thus improving the stability of the fill contained within the stope. Permeability tests for mine fills and barricade bricks are discussed by Rankine et al. 4. The constant head and falling head permeability tests carried out on the hydraulic fill samples give permeability values in the r
22、ange of 7-35 mm/h. In spite of having permeability values much less than the 100 mm threshold suggested by Herget and De Korompay 3, each of these hydraulic fills has performed satisfactorily. Anecdotal evidences and back calculations using the measured flow in the mine stopes suggest that the permeability of the hydraulic fill in the mine is often larger than what is measured in the laboratory under controlled conditions. Kuganathan5 and Brady and
