中英文对照外文翻译
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英文：
Roadheader applications in mining and tunneling
industries
ABSTRACT
Roadheaders offer a unique capability and flexibility for the excavation of soft to medium strength rock formations, therefore, are widely used in underground mining and tunneling operations. A critical issue in successful roadheader application is the ability to develop accurate and reliable estimates of machine production capacity and the associated bit costs. This paper presents and discusses the recent work completed at the Earth Mechanics Institute of Colorado School of Mines on the use of historical data for use as a performance predictor model. The model is based on extensive field data collected from different roadheader operations in a wide variety of geologic formations. The paper also discusses the
development of this database and the resultant empirical performance prediction equations derived to estimate roadheader cutting rates and bit consumption. INTRODUCTION
The more widespread use of the mechanical excavation systems is a trend set by increasing pressure on the mining and civil construction industries to move away from the conventional drill and blast methods to improve productivity and reduce costs. The additional benefits of mechanical mining include significantly improved safety, reduced ground support requirements and fewer personnel. These advantages coupled with recent enhancements in machine performance and reliability have resulted in mechanical miners taking a larger share of the rock excavation market.
Roadheaders are the most widely used underground partial-face excavation machines for soft to medium strength rocks, particularly for sedimentary rocks. They are used for both development and production in soft rock mining industry (i.e. main haulage drifts, roadways, cross-cuts, etc.) particularly in coal, industrial minerals and evaporitic rocks. In civil construction, they find extensive use for excavation of tunnels (railway, roadway, sewer, diversion tunnels, etc.) in soft ground conditions, as well as for enlargement and rehabilitation of various underground structures. Their ability to excavate almost any profile opening also makes them very attractive to those mining and civil construction projects where various opening sizes and profiles need to be constructed.
In addition to their high mobility and versatility, roadheaders are generally low capital cost systems compared to the most other mechanical excavators. Because of higher cutting power density due to a smaller cutting drum, they offer the capability to excavate rocks harder and more abrasive than their counterparts, such as the continuous miners and the borers. ROADHEADERS IN LAST 50 YEARS
Roadheaders were first developed for mechanical excavation of coal in the early 50s. Today, their application areas have expanded beyond coal mining as a result of continual performance increases brought about by new technological developments and design improvements. The major improvements achieved in the last 50 years consist of steadily increased machine weight, size and cutterhead power, improved design of boom, muck pick up and loading system, more efficient
cutterhead design, metallurgical developments in cutting bits, advances in hydraulic and electrical systems, and more widespread use of automation and remote control features. All these have led to drastic enhancements in machine cutting capabilities, system availability and the service life.
Machine weights have reached up to 120 tons providing more stable and stiffer (less vibration, less maintenance) platforms from which higher thrust forces can be generated for attacking harder rock formations. . The cutterhead power has increased significantly, approaching 500 kW to allow for higher
torque capacities. Modern machines have the ability to cut cross-sections over 100m2 from a stationary point. Computer aided cutterhead lacing design has developed to a stage to enable the design of optimal bit layout to achieve the maximum efficiency in the rock and geologic conditions to be encountered. The cutting bits have evolved from simple chisel to robust conical bits. The muck collection and transport systems have also undergone major improvements, increasing attainable production rates. The loading apron can now be manufactured as an extendible piece providing for more mobility and flexibility. The machines can be equipped with rock bolting and automatic dust suppression equipment to enhance the safety of personnel working at the heading. They can also be fitted with laser-guided alignment control systems, computer profile controlling and remote control systems allowing for reduced operator sensitivity coupled with increased efficiency and productivity. Figure-1 shows a picture of a modern transverse type roadheader with telescopic boom and bolting system.
extensive翻译Mobility, flexibility and the selective mining capability constitute some of the most important application advantages of roadheaders leading to cost effective operations. Mobility means easy relocation from one face to another to meet the daily development and production requirements of a mine. Flexibility allows for quick changes in operational conditions such as
Figure-1: A Transverse Cutterhead Roadheader (Courtesy of Voest Alpine) different opening profiles (horse-shoe, rectangular, etc.), cross-sectional sizes, gradients (up to 20, sometimes 30 degrees), and the turning radius (can make an almost 90 degree turn). Selectivity refers to the ability to excavate different parts of a mixed face where the ore can be mined separately to reduce dilution and to minimize waste handling, both contributing to improved productivity. Since roadheaders are partial-face machines, the face is accessible, and therefore, cutters can be inspected and changed easily, and the roof support can be installed very close to the face. In addition to these, high production rates in favorable ground conditions, improved safety, reduced ground support and ventilation requirements, all
resulting in reduced excavation costs are the other important advantages of roadheaders.
The hard rock cutting ability of roadheaders is the most important limiting factor affecting their applications. This is mostly due to the high wear experienced by drag bits in hard, abrasive rocks. The present day, heavy-duty roadheaders can economically cut most rock formations up to 100 MPa (~14,500 psi) uniaxial compressive strength (UCS) and rocks up to 160 MPa (~23,000 psi) UCS if favorable jointing or bedding is present with low RQD numbers. Increasing frequency of joints or other rock weaknesses make the rock excavation easier as the machine simply pulls or rips out the blocks instead of cutting them. If the rock is very abrasive, or the pick consumption rate is more than 1-pick/m3, then roadheader excavation usually becomes uneconomical due to frequent bit changes coupled with increased machine vibrations and maintenance costs.
A significant amount of effort has been placed over the years on increasing the ability of roadheaders to cut hard rock. Most of these efforts have focused on structural changes in the machines, such as increased weight, stiffer frames and more cutterhead power. Extensive field trials of these machines showed that the cutting tool is still the weakest point in hard rock excavation. Unless a drastic improvement is achieved in bit life, the true hard rock cutting is still beyond the realm of possibility with roadheaders. The Earth Mechanics Institute(EMI) of the Colorado School of Mines has been developin
g a new cutter technology, the Mini-Disc Cutter, to implement the hard rock cutting ability of disc cutters on roadheaders, as well as other types of mechanical excavators (Ozdemir et al, 1995). The full-scale laboratory tests with a standard transverse cutterhead showed that MiniDisc Cutters could increase the ability of the roadheaders for hard rock excavation while providing for lesser cutter change and maintenance stoppages. This new cutting technology holds great promise for application on roadheaders to extend their capability into economical excavation of hard rocks. In addition, using the mini-disc cutters, a drum miner concept has been developed by EMI for application to hard rock mine development. A picture of the drum miner during full-scale laboratory testing is shown in Figure-2.
Figure-2: Drum Miner Cutterhead
FIELD PERFORMANCE DATABASE
Performance prediction is an important factor for successful roadheader application. This deals generally with machine selection, production rate and bit cost estimation. Successful

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