裝配圖胡軍雄,裝配,胡軍雄 Correlation of TBM and drilling machine performances with rock brittleness S. Kahraman, Geological Engineering Department, University of Nide, 51100 Nide, Turkey Received 3 May 2001;? accepted 19 November 2001.? Available online 18 December 2001. Referred to by: Corrigendum to: “Correlation of TBM and drilling machine performances with rock brittleness” [Eng. Geol. 65 (2002) 269–283], Engineering Geology,?Volume 67, Issues 3-4,?January 2003,?Page 405 S. Kahraman SummaryPlus | Full Text + Links | PDF (35 K) Abstract The correlations between three different methods of measuring brittleness and both drillability and borability were statistically investigated using the raw data obtained from the experimental works of different researchers. Strong exponential relationships between the penetration rates of tunnel boring machine (TBM) and the brittleness of B1 (the ratio of compressive strength to tensile strength) and B2 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength) were found. There is no correlation between the penetration rates of the diamond drilling tool and the brittleness values. Strong exponential correlations exist between the penetration rates of rotary drills and the brittleness of B1 and B2. However, no correlation between the penetration rate of rotary drills and the brittleness of B3 (the product of percentage of fines in impact strength test and compressive strength) was found. The penetration rate of percussive drills does not exhibit a correlation with the brittleness of B1 and B2, but the penetration rate of percussive drills is strongly correlated with the brittleness of B3. It was concluded that each method of measuring brittleness has its usage in rock excavation depending on practical utility. Author Keywords: Rock brittleness; TBMs; Rotary drills; Percussive drills Article Outline 1. Introduction 2. Brittleness 3. Evaluation of some experimental data 3.1. Tunnel boring 3.2. Diamond drilling 3.3. Rotary drilling 3.4. Percussive drilling 4. Correlations among the three different methods of measuring brittleness 5. Conclusions References 1. Introduction Rotary and percussion drilling equipment is widely used in rock excavation. Tunnel boring machines (TBMs) are ubiquitous in civil engineering applications. Having some prior knowledge of the potential performance of the selected rock drilling equipment or boring machines is very important in rock excavation projects for the planning and the cost estimation purposes. Drillability and borability can be predicted from a combination of machine characteristics and rock properties. Uniaxial compressive strength is the most widely used parameter for predicting the performance of tunnelling machines and drilling rigs (Paone; Paone; Paone; Barendsen; Fowel; Brown; Poole; Aleman; Hughes; Karpuz; Bilgin and Kahraman). In addition, a wide range of empirical tests has been used to predict the performance of drilling or boring machines. Among these are: Schmidt hammer, Taber abrasion, point load, cone indenter, Shore hardness, drilling rate index (DRI) and coefficient of rock strength (CRS) (McFeat; Howarth; Nilsen and Li). Recently, rock mass classification systems, such as Q-system and RMR-system, have been used for the estimation of TBM performance (Alber and Barton). Evans and Pomeroy (1966) theoretically showed that impact energy of a cutter pick is inversely proportional to brittleness. Singh (1986) indicated that cuttability, penetrability and Protodyakonov strength index of coal strongly depended on the brittleness of coal. Singh (1987) showed that a directly proportional relationship existed between in situ specific energy and brittleness of three Utah coals. G?ktan (1991) stated that the brittleness concept might not be a representative measure of rock cutting-specific energy consumption. Brittleness is one of the most important mechanical properties of rocks. However, there is no available published material on the relationship between brittleness and both drillability and borability. In this study, the correlations between brittleness and both drillability and borability were analyzed using the raw data obtained from the experimental works of different researchers. Rock properties and performance data obtained from the different researchers were listed in the respective tables. The calculation of brittleness values and generation of the plots were performed by the author. 2. Brittleness Morley (1944) and Hetényi (1966) defined brittleness as the lack of ductility. Materials such as cast iron and many rocks usually terminating by fracture at or only slightly beyond the yield stress have been defined as brittle by Obert and Duvall (1967). Ramsay (1967) defines brittleness as follows: when the internal cohesion of rocks is broken, the rocks are said to be brittle. The definition of brittleness as a mechanical property varies from author to author. However, it may be stated that with higher brittleness the following facts are observed (Hucka and Das, 1974): ? low values of elongation, ? fracture failure, ? formation of fines, ? higher ratio of compressive to tensile strength, ? higher resilience, ? higher angle of internal friction, and ? formation of cracks in indentation. Different definitions of brittleness have been summarised and discussed by Hucka and Das (1974). The three equations used in this study are as follows: (1) (2) B3=qσc (3) where, B1, B2 and B3 equals brittleness, σc is uniaxial compressive strength, σt is tensile strength, and q is the percentage of fines formed in Protodyakonov (1963) impact test. 3. Evaluation of some experimental data 3.1. Tunnel boring Howarth et al. (1986) reported the performance characteristics of a model TBM in six sedimentary rock types. The model TBM had an overall diameter of 106 mm and was fitted with six tungsten carbide-tipped square-faced drag bits of dimensions 9.5×9.5 mm and a spacing between adjacent cutters of 7.5 mm. Penetration rates, rock properties and calculated brittleness values are given in Table 1. Table 1. The test data of Model TBM (Howarth et al., 1986) and calculated brittleness values Thrust: 3.16 kN, rpm: 14. The performance characteristics of the model TBM were analysed using the method of least squares regression. The equation of the best-fit line, the 95% confidence limits and the correlation coefficients (r) were determined for each regression. Penetration rates were correlated with the brittleness values. The plots of the penetration rates as a function of the brittleness values are shown in Fig. 1. It is seen that there are exponential relationships between the penetration rates and the brittleness of B1 and B2. (11K) Fig. 1. Penetration rate vs. brittleness for the model TBM (the graphs were plotted by the author using the data in Table 1). 3.2. Diamond drilling Clark (1979) reported the drilling performances of impregnated diamond bits tested on seven rock types in the laboratory and on 21 rock types in the field (Table 2 and Table 3). Laboratory drilling experiments were carried out with AX size bits with a medium hard matrix. The drill rig was an electrohydraulic diamond drill with instrumentation for measuring thrust, rotary speed and torque. Field drilling experiments were performed with a trailer-mounted diamond drill machine equipped with hydraulic thrust. Table 2. The laboratory test data of impregnated diamond bits (Clark, 1979) and calculated brittleness values Thrust: 4.54 kN, rpm: 1000. Table 3. The field test data of impregnated diamond bits (Clark, 1979) and calculated brittleness values Thrust: 4.54 kN, rpm: 600. Howarth (1987) reported the performance characteristics of a diamond drilling tool in crystalline and sedimentary rock types. The type of diamond drilling tool used was a thin-walled impregnated bit with water flushing. The impregnated bit had an outer diameter of 31.9 mm and an internal diameter of 28.1 mm. Drilling data, rock characteristics and calculated brittleness values are given in Table 4. Table 4. The laboratory test data of impregnated diamond bits (Howarth, 1987) and calculated brittleness values Thrust: 770 N, rpm: 750, water pressure: 552 kPa, water flow rate: 2 l/min. The data in Table 2, Table 3 and Table 4 were analysed using the least square regression method. Penetration rates vs. the brittleness values are plotted and it is seen that there is no correlation between the penetration rates and the brittleness values (Fig. 2, Fig. 3 and Fig. 4). (7K) Fig. 2. Penetration rate vs. brittleness for impregnated diamond bits tested in the laboratory (the graphs were plotted by the author using the data in Table 2). (8K) Fig. 3. Penetration rate vs. brittleness for impregnated diamond bits tested in the field (the graphs were plotted by the author using the data in Table 3). (8K) Fig. 4. Penetration rate vs. brittleness for impregnated diamond bits tested in the laboratory (the graphs were plotted by the author using the data in Table 4). 3.3. Rotary drilling Bilgin et al. (1993) and Kahraman (1999) measured the drilling performance of rotary blast hole drills in the open pit mines of Turkish Coal Enterprises and determined the physical and mechanical properties of the rocks drilled. Impact strength tests were carried out with the device designed by Evans and Pomeroy (1966). Performance results, rock properties and calculated brittleness values are given in Table 5. Table 5. The field test data of rotary drills (Bilgin and Kahraman) and calculated brittleness values Bit: 251 mm WC tri-cone bit, thrust: 50–59 kN, rpm: 118–120. Using the method of least squares regression, the penetration rates of rotary drills were correlated with the brittleness values. Exponential relationships between the penetration rates and the brittleness of B1 and B2 were found (Fig. 5a,b). There is no correlation between the penetration rate and the brittleness of B3 (Fig. 5c). (16K) Fig. 5. Penetration rate vs. brittleness for rotary drills observed in the field (the graphs were plotted by the author using the data in Table 5). 3.4. Percussive drilling Howarth et al. (1986) carried out percussion drilling tests on 10 sedimentary and crystalline rocks. The percussion drilling tool was a simple wedge indenter (tungsten carbide insert) located on the end of a drill steel that was driven by an Atlas Copco RH571 compressed air-powered percussion drill with water flushing. Penetration rates, rock properties and calculated brittleness values are given in Table 6. Table 6. The laboratory test data of percussion drilling (Howarth, 1987) and calculated brittleness values Thrust: 441 N, air pressure: 450 kPa. Selim and Bruce (1970) reported the penetration data of percussive drills determined from nine rocks drilled in the laboratory. Two drills were used in the experiments. The drill included in this study was a 6.67-cm bore jackleg type. The drill was backstroke rifle-bar-rotation machine and bit diameter was confined to 3.81-cm cross bits. Penetration rates, rock properties and calculated brittleness values are given in Table 7. Table 7. The laboratory test data of percussion drilling (Selim and Bruce, 1970) and calculated brittleness values Operating pressure: 632.7 kPa, feed pressure: 492 kPa. Schmidt (1972) reported the performance characteristics of two percussive drills mounted on a truck in 25 rock types. The drill included in this study was a standard drifter having a bore diameter of 6.67 cm. Bit type was H-thread carbide and bit diameter was 5.08 cm. Penetration rates, rock properties and calculated brittleness values are given in Table 8. Table 8. The field test data of percussion drilling (Schmidt, 1972) and calculated brittleness values Operating pressure: 703 kPa. Kahraman (1999) measured the drilling performance of hydraulic top hammer drills in open pits, motorway sites and quarries and determined the physical and mechanical properties of the rocks drilled. Impact strength tests were carried out with the device designed by Evans and Pomeroy (1966). Performance results, rock properties and calculated brittleness values are given in Table 9. Table 9. The field test data of percussion drilling (Kahraman, 1999) and calculated brittleness values Bit diameter: 76 mm, rock drill power: 14–15.5 kW, bpm: 3000–3600, pulldown pressure: 60–70 bar, blow pressure: 100–120 bar, rotational pressure: 60–65 bar. The data in Table 6, Table 7, Table 8 and Table 9 were evaluated using regression analysis. As it is seen in Fig. 6, Fig. 7, Fig. 8 and Fig. 9, there is no correlation between the penetration rate and the brittleness of B1 and B2. However, the penetration rate is strongly related with the brittleness of B3. The relation between the penetration rate and the brittleness of B3 follows a power function (Fig. 9c). (9K) Fig. 6. Penetration rate vs. brittleness for percussive drills tested in the laboratory (the graphs were plotted by the author using the data in Table 6). (9K) Fig. 7. Penetration rate vs. brittleness for percussive drills tested in the laboratory (the graphs were plotted by the author using the data in Table 7). (10K) Fig. 8. Penetration rate vs. brittleness for percussive drills tested in the field (the graphs were plotted by the author using the data in Table 8). (15K) Fig. 9. Penetration rate vs. brittleness for percussive drills observed in the field (the graphs were plotted by the author using the data in Table 9). 4. Correlations among the three different methods of measuring brittleness To see whether a method of measuring brittleness differs from the other methods, the data in Table 1, Table 2, Table 3, Table 4, Table 5, Table 6, Table 7, Table 8 and Table 9 were analysed using the least square regression method. It was seen that there is a strong logarithmic relationship between the brittleness of B1 and B2. Fig. 10 was given as an example. As seen in the examples of Fig. 11 and Fig. 12, there is no correlation between the brittleness of B3 and the brittleness of both B1 and B2. Consequently, it can be said that the brittleness of B3 is different from the brittleness of both B1 and B2. This is probably because the method of measuring brittleness of B3 is different from that of the brittleness of both B1 and B2. Moreover, Hucka and Das (1974) stated that there is no uniformity in different formulation of brittleness. (5K) Fig. 10. The correlation between the brittleness of B1 and B2 (the graph was plotted by the author using the data in Table 8). (3K) Fig. 11. The correlation between the brittleness of B1 and B3 (the graph was plotted by the author using the data in Table 5). (4K) Fig. 12. The correlation between the brittleness of B2 and B3 (the graph was plotted by the author using the data in Table 5). 5. Conclusions Brittleness, defined differently by different authors, is an important mechanical property of rocks, but the correlations between the brittleness and both drillability and borability have not been clearly explained yet. The relationships between three different methods of brittleness and both drillability and borability were statistically examined using the raw data obtained from the experimental works of different researchers. There are strong exponential relationships between the penetration rates of TBM and the brittleness of B1 and B2. There is no correlation between the penetration rates of diamond drilling tool and the brittleness values. Exponential relationships with high correlation coefficients between the penetration rates of rotary drills and the brittleness of B1 and B2 were found. However, no correlation between the penetration rate of rotary drills and the brittleness of B3 was found. There is no correlation between the penetration rate of percussive drills and the brittleness of B1 and B2, but the penetration rate of percussive drills is strongly related with the brittleness of B3. Besides, the brittleness of B3 is different from the brittleness of both B1 and B2. The lack of correlation between the penetration rate of rotary drills and the brittleness of B3 is probably due to the fact that the brittleness of B3 is obtained from the impact test. Similarly, the absence of correlation between the penetration rate of percussive drills and the brittleness of B1 and B2 is probably due to the fact that the brittleness of B1 and B2 is obtained from compressive and tensile strengths. That the rock-breaking process in rotary drilling is different from that in percussive drilling explains better this situation. Percussion is the dominant factor in percussive drilling, whereas thrust and crushing are the dominant factors in rotary drilling. It can be concluded that there is no uniformity in different formulations of brittleness. Each should be used separately in rock excavation, depending on practical utility. Brittleness, which is a combined property, is one of the most important properties of rocks. Knowing the degree of the brittleness of rock would lead to an improved excavation technology. Thus, further research is necessary in this area. 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