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1、英文文献Roadheader applications in mining and tunneling industriesH. Copur1, L. Ozdemir2, and J. Rostami31Graduate Student, 2 Director and Professor, and 3 Assistant ProfessorEarth Mechanics Institute, Colorado School of Mines, Golden, Colorado, 80401ABSTRACT Roadheaders offer a unique capability and fl

2、exibility 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 a

3、ssociated 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 operati

4、ons 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 syst

5、ems 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 re

6、quirements 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

7、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 extensi

8、ve 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 civ

9、il 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

10、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 h

11、ave 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 boo

12、m, 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 capabilitie

13、s, 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 signific

14、antly, 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

15、 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 exte

16、ndible 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 controlli

17、ng 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.Mobility, flexibility and the selective mining capability constitute som

18、e 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 Figu

19、re-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

20、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 th

21、e 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 h

22、ard 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 ps

23、i) 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 cutt

24、ing 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 ye

25、ars 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 poin

26、t 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 developing a new cutter technology, the Mini-Disc Cutter,

27、 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

28、 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

29、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 CutterheadFIELD PERFORMANCE DATABASE Performance prediction is an important factor for successful roadheader application. Th

30、is deals generally with machine selection, production rate and bit cost estimation. Successful application of roadheader technology to any mining operation dictates that accurate and reliable estimates are developed for attainable production rates and the accompanying bit costs. In addition, it is o

31、f crucial importance that the bit design and cutterhead layout is optimized for the rock conditions to be encountered during excavation. Performance prediction encompasses the assessment of instantaneous cutting rates, bit consumption rates and machine utilization for different geological units. The

32、 instantaneous cutting rate (ICR) is the production rate during actual cutting time, (tons or m3 / cutting hour). Pick consumption rate refers to the number of picks changed per unit volume or weight of rock excavated, (picks / m3 or ton). Machine utilization is the percentage of time used for excav

33、ation during the project Table-I: Classification of the Information in the DatabaseINFORMATION GROUPDETAILSGeneral InformationType/purpose of excavation (roadway, railway, sewer, mining gallery, etc.), contractor, owner, consultant, location, starting and completion date, etc.Roadheader InformationM

34、anufacturer, condition of the roadheader (new, refurbished, direct reuse), specifications of roadheader, machine weight, cutterhead power and diameter, bit number and type, ancillary equipment (automatic profile control, water sprays, grippers, etc.)Technical and Operational InformationExcavation le

35、ngth, depth, and gradients, dimensions of excavation profile, operator experience, cutting sequence at the face, daily and weekly mining hours, muck evacuation system, ground support system, etc.Rock Mass Information For Each Rock ZoneGeological origin, number and character of geological zones, hydr

36、ogeological conditions, rock mass classifications, RQD, bedding properties, joint set properties (orientation, spacing, roughness, filling, etc.)Intact Rock Information For Each Rock ZoneRock cuttability properties, uniaxial and tensile strength, elasticity modulus, surface hardness, texture (porosi

37、ty, mineral / quartz content & grain sizes, microfractures, etc.), abrasivity properties, etc.Performance Records For Each Rock ZoneCutting rates, bit and holder consumption, roadheader utilization and availability, energy consumption, average and best advance rates (shiftly/daily/weekly/monthly), m

38、ajor obstructions to excavation operation, downtime analysis (roadheader related stoppages, backup system stoppages, ground and support stoppages, etc.)The Earth Mechanics Institute of the Colorado School of Mines jointly with the Mining Department of the Istanbul Technical University has establishe

39、d an extensive database related to the field performance of roadheaders with the objective of developing empirical models for accurate and reliable performance predictions. The database contains field data from numerous mining and civil construction projects worldwide and includes a variety of roadh

40、eaders and different geotechnical conditions.The empirical performance prediction methods are principally based on the past experience and the statistical interpretation of the previously recorded case histories. To obtain the required field data in an usable and meaningful format, a data collection

41、 sheet was prepared and sent to major contractors, owners, consultants, and roadheader manufacturers. In addition, data was gathered from available literature on roadheader performance and through actual visits to job sites. This data collection effort is continuing.The database includes six categor

42、ies of information, as shown in Table-I. The geological parameters in the database consist generally of rock mass and intact rock properties. The most important and pertinent rock mass properties contained in the database include Rock Quality Designation (RQD), bedding thickness, strike and dip of j

43、oint sets and hydrological conditions. The intact rock properties are uniaxial compressive strength, tensile strength, quartz content, texture and abrasivity. The rock formations are divided into separate zones to minimize the variations in the machine performance data to provide for more accurate a

44、nalysis. This also simplifies the classification of the properties for each zone and the analysis of the field performance data. The major roadheader parameters included are the machine type (crawler mounted, shielded), machine weight, cutterhead type (axial, transverse), cutterhead power, cutterhea

45、d-lacing design, boom type (single, double, telescopic, articulated), and the ancillary equipment (i.e.grippers, automatic profiling, laser guidance, bit cooling and dust suppression by water jets, etc.). The operational parameters generally affect the performance of the excavator through machine ut

46、ilization. The most important operational parameters include ground support, back up system (transportation, utility lines, power supply, surveying, etc.), ground treatment (water drainage, grouting, freezing, etc.), labor (availability and quality), and organization of the project (management, shif

47、t hours, material supply, etc.).CONCLUSIONS The evaluation and analysis of the data compiled in the roadheader field performance database has successfully yielded a set of equations which can be used to predict the instantaneous cutting rate (ICR) and the bit consumption rate(BCR) for roadheaders. A

48、 good relationship was found to exist between these two parameters and the machine power (P), weight (W) and the rock compressive strength (UCS). Equations were developed for these parameters as a function of P, W and UCS. These equations were found mainly applicable to soft rocks of evaporatic orig

49、in. The current analysis is being extended to include harder rocks with or without joints to make the equations more universal. In jointed rock, the RQD value will be utilized as a measure of rock mass characteristics from a roadheader cuttability viewpoint. It is believed that these efforts will lead to the formulation of an accurate roadheader performance prediction model which can be used in different rock types where the roadheaders are economically applicable.中文译文掘进机在采矿和隧道