1、PDF外文：http:/ Abstract The factors affecting the performance of 90 kW-shielded roadheader is investigated in detail in a tunnel excavated for NuhCement Factory. The first part of the tunnel is horizontal and the second part is inclined with 9_ and excavated uphill. Tunnel passes through a form
2、ation of the Upper Cretaceous age with nodular marl, carbonated claystone, thin and thick laminated limestone. Water ingress changes from 0 to 11 l/min. In six different zones it is found that the rock compressive strength changed from 20 to 45 MPa, tensile strength from 1 to 4 MPa, specific energy
3、from 11 to 16 MJ/m3, plastic limit from 15% to 29%, liquid limit from 27% to 43% and water absorption from 4% to 18% in volume. Detailed in situ observations show that in dry zones for the same rock strength the inclination of the tunnel and the strata help to increase the instantaneous cutting rate
4、 from 10 to 25 solid bank m3/cutting hour. The effect of water on cutting rate is dramatic. In the zones where the plastic limit and the amount of Al2O3 is low, instantaneous cutting rate increases from 34 to 50 solid bank m3/ cutting hour with increasing water content from 3.5 to 11 l/min. However,
5、 in the strata having high water absorption characteristic and high amount of Al2O3, cutting rate decreases considerably due to the sticky mud, causing problem to the cutterhead. Excavation, muck loading and support works are performed separately due to safety concerns in the wet and inclined sectio
6、ns which reduced the machine utilization time from 38% to 8%. The information gathered is believed to form a sound basis in contributing the performance prediction of roadheaders in difficult ground conditions. _ 2004 Elsevier Ltd. All rights reserved. Keywords: Tunnel excavation； Roadheader p
7、erformance prediction； Core cutting test； Specific energy 1. Introduction The application of roadheaders in difficult ground conditions, in recent years, has increased considerably in both civil and mining engineering fields. The prediction of instantaneous (net) cutting rate and machine
8、 utilization time, determining daily advance rates, plays an important role in the time scheduling of the tunneling projects, hence, in determining the economy of tunnel excavation. Although many roadheader performance prediction models were published in the past, the published data on difficu
9、lt ground conditions such as the effects of tunnel inclination, water ingress, excessive fracture zones, etc. on daily advance rates were quite scarce. Sandbak (1985) and Douglas (1985) used a rock classification system to explain the changes of roadheader advance rates at San Manuel Copper Mine in
10、an inclined drift at an 11% grade. They concluded that for a performance prediction model, engineering aspects of the roadheaders had to be also incorporated with the geomechanical factors. Field data on roadheader machine performance in inclined tunnels were also published by Unrug and Whitse
11、ll (1984) for a 14_ slope in Pyro Coal Mine, by Navin et al. (1985) at 13_ and 15_ inclines in oil shale mine and by Livingstone and Dorricott (1995) in Ballarat East Gold Mine. The majority of performance prediction models were developed for horizontal tunnels. Bilgin (1983) developed a model based
12、 on specific energy obtained from drilling rate of a percussive drill. Models for widely jointed rock formations were described by Schneider (1988), Thuro and Plinninger (1998, 1999), Gehring (1989, 1997), Dun et al. (1997) and Uehigashi et al. (1987). They reported that for a given cutting po
13、wer, cutting rates of roadheaders decreased dramatically with increasing values of rock compressive strength. Copur et al. (1997, 1998) stated that if the power and the weight of the roadheaders were considered together, in addition to rock compressive strength, the cutting rate predictions were mor
14、e realistic. Another concept of predicting machine instantaneous cutting rate was to use specific energy described as the energy spent to excavate a unit volume of rock material. Farmer and Garrity (1987) and Poole (1987) showed that for a given power of roadheader, excavation rate in solid bank m3/
15、cutting hour might be predicted using specific energy values given as in the following equation, where SE is the specific energy, rc is the rock compressive strength and E is the rock elastic modulus. Widely accepted rock classification and assessment for the performance estimation of roadhea
16、ders is based on the specific energy found from core cutting tests (McFeat-Smith and Fowell, 1977, 1979； Fowell and Johnson, 1982； Fowell et al., 1994). Detailed laboratory and in situ investigations carried out by McFeat-Smith and Fowell (1977, 1979) showed that there was a close relationship betwe
17、en specific energy values obtained from core cutting tests and cutting rates for medium and heavy weight roadheaders separately. They reported also that tool consumption might be predicted from weight loss of cutter used in core cutting test. Rock cuttability classification based on core cutti
18、ng test is usually criticized as that the effect of rock discontinuities are not reflected in performance prediction. Bilgin et al. (1988, 1990, 1996, 1997) developed a performance equation based on rock compressive strength and rock quality designation as given below where ICR is the instant
19、aneous cutting rate in solid bank m3/cutting hour, P is the power of cutting head in hp, RMCI is the rock mass cuttability index, rc is the uniaxial compressive strength in MPa and RQD is the rock quality designation in percent. Dun et al. (1997) compared the models described by Bilgin et al. (1988,
20、 1990) and McFeat-Smith and Fowell (1977, 1979) in a research work carried out at Kumbalda Mine where a Voest Alpine AM75 roadheader was utilized. Two distinct groups of data were evident. The data grouped around Bilgin line was strongly influenced by the jointing and weakness zones present in rock
21、mass. The other group of data on the line produced by McFeat-Smith and Fowell corresponded to areas where less jointing and fewer weakness zones were present. One of the most accepted method to predict the cutting rate of any excavating machine is to use, cutting power, specific energy obtaine
22、d from full scale cutting tests and energy transfer ratio from the cutting head to the rock formation as in the following equation (Rostami et al., 1994； Rostami and Ozdemir, 1996) where ICR is th instantaneous production rate in solid bank m3/cutting hour, P is the cutting power of themechani
23、cal miner in kW, SEopt is the optimum specific energy in kWh/m3 and k is energy transfer coefficient depending on the mechanical miner utilized. Rostami et al. (1994) strongly emphasized that the predicted value of cutting rate was more realistic if specific energy value in equation was obtained fro
24、m full-scale linear cutting tests in optimum conditions using real life cutters. Rostami et al. (1994) pointed out that k changed between 0.45 and 0.55 for roadheaders and from 0.85 to 0.90 for TBMs. Bilgin et al. (2000) showed in their experimental and numerical studies that performance of mechanical miners was affected upto a certain degree by the earth and/or overburden pressure and stress. Copur et al. (2001) showed that specific energy obtained from full-scale linear cutting tests in optimum cutting conditions was highly correlated to rock uniaxial compressive strength and Brazilian
