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World Tunnel Congress 2008 - Underground Facilities for Better Environment and Safety - India

The selection of a TBM using full scale laboratory tests and comparison of measured and predicted performance values in Istanbul Kozyatagi-Kadikoy metro tunnels

Nuh Bilgin, Hanifi Copur, Cemal Balci & Deniz Tumac Istanbul Technical University, Mining Engineering Department, Turkey Mustafa Akgul & Ali Yuksel Anadoluray Joint Venture, Turkey

SYNOPSIS This study is about the determination of some design parameters and performance prediction of tunnel boring machines (TBM) using full-scale rock cutting test in the main rock formations encountered in Kadikoy-Kartal Metro Tunnels. The rock samples having minimum sizes of 1.0 x 0.5 x 0.7 m are obtained from four different formations along the tunnel line. The rock samples are subjected to full scale laboratory cutting tests with different depth of cut and cutter spacing values using a 13 inch (330 mm) CCS disc cutter. Cutter forces, i.e., thrust force, rolling force, and specific energy values in kWh/m3 are recorded for each cut. All the performance data i.e. advance rate, machine thrust, torque and some other parameters are recorded carefully during the tunnel excavation and the actual values are compared with the predicted values. It is concluded that the water, geological discontinuities and dyke inclusions affect the TBM performance tremendously.

1. INTRODUCTON

Istanbul is a very fast developing city with more than 14 millions of population. Tunneling activities like metro, sewerage and water tunnels are increasing tremendously and at the end of 2008 it is planned that around 20 TBMs with different diameters will be working in the city. The total cost of the current tunneling projects is calculated to be around 10 Billion USA Dollars. The geology of Istanbul is complex for tunneling projects due to tectonic activities, faults, dacite and andesite dykes and several joint sets causing many serious problems during tunnel excavation. However, a great effort is spent by the authors of this paper to collect data concerning the performance of mechanized excavation systems related to geology and rock mass properties in order to have guidelines for the future tunnel projects. The results of the research carried out for Kadikoy-Kartal Metro line are evaluated in this respect. This paper is concerned about full scale cutting tests in laboratory in order to define the design

parameters and predict performance of tunnel boring machines to be used in Kadikoy-Kartal Metro Tunnels. The general alignment of the metro tunnels is given in Figure 1.

2. GEOLOGY OF THE TUNNEL AREA, PHYSICAL AND MECHANICAL PROPERTIES OF THE ROCK SAMPLES SUBJECTED TO ROCK CUTTING TESTS

Sedimentary rock formations of Triassic and Tertiary ages are found in the area. Four different block samples representing the rock formations to be excavated with TBM and having average sizes of 1 x 0.5 x 0.7 m are used for rock cutting experiments. 29.9 % of total tunnel length is planned to be excavated in Kartal Formation (limestone), 29.7 % in Kurtkoy Formation (arcose), 17.5 % in Doloyaba Formation (limestone), 13.6 % in Trakya Formation (greywacke, alternated sandstone, mudstone and siltstone (Yuksel et al., 2005).[1]

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Standard physical and mechanical tests are carried out on core samples of NX size. Test results are summarized in Table 1.

3. FULL SCALE ROCK CUTTING TESTS

3.1 Description of full scale cutting rig

The full scale cutting rig established in the laboratories of ITU Mining Engineering Department and used in the experiments is given in Figure 2. The box accommodating the rock samples up to 1.0 x 0.5 x 0.7 m can be moved horizontally to adjust cutter spacing and depth of cut is adjusted

by a hydraulic cylinder. The aluminum dynamometer equipped with strain gauges has a capacity of 50 tons of thrust force (Bilgin et al., 1999).[2] The following parameters used in evaluating disc cutting performance are illustrated in Figure 3. S : Cutter Spacing, cm d : Cutter Penetration, cm FR : Mean Rolling Force, kgf FN : Mean Thrust Force, kgf FR : Maximum Rolling Force, kgf FN : Maximum Thrust Force, kgf SE : Specific Energy, kWh/m3

Figure 1. Tunnel route of Kadikoy Kartal metro line

Table 1. Physical and mechanical properties of the rocks

Physical and Mechanical Properties

Kurtkoy Formation (Arcose)

Kartal Formation

(Limestone)

Doloyaba Formation

(Limestone)

Trakya Formation (Siltstone)

Uniaxial Comp. Strength (MPa SD) 34.1 10.3 65.6 6.7 119.9 19.0 82.6 8.6

Tensile Strength (MPa SD) 4.2 0.8 7.4 2.0 7.5 1.7 5.4 2.3

Static Poisson Ratio 0.26 0.35 0.36 - Static Elastic Modulus (GPa SD) 6.4 1.5 12.6 15.5 0.9 -

Dynamic Elastic Modulus (GPa SD) 70.1 12.0 77.3 2.0 100.0 15.7 88.7 4.2

Cerchar Abrasivity 2.0 1.5 1.5 1.0 Schmidt Hammer Hardness (N-24SD) 39.0 5.0 40.0 57.0 3.0 -

Specific Gravity (gr/cm3) 2.68 2.62 2.70 2.70

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3.2 Experimental procedure and the results

A constant cross section disc having a diameter of 13 inches and a width of 1.2 cm is used in rock cutting experiments. The cutter spacing is kept as 7 and 8 cm throughout the experiments. The experiments are realized in unrelieved mode where there is not any interaction between the cutters and in relieved mode where there is interaction between cutters. The relieved and unrelieved modes are explained in Figure 4 and the cutting results are summarized in Figures 5 and 6 and Table 2.

Figure 2. General and schematic view of full scale linear cutting rig

Figure 3. Design parameters of disc cutters

Figure 4. The effect of (cutter spacing / cutter penetration) ratio on the specific energy and chip formation

Figure 5. The relationships between penetration, thrust force, rolling force and specific energy values for cutting limestone (Kartal Formation) in unrelieved mode

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Figure 6. The relationships between spacing/ penetration ratio, thrust force, rolling force and specific energy values for cutting limestone (Kartal Formation) in relieved mode

Table 2. Summary of rock cutting tests in relieved mode in four different formation

Rock Formation Optimum (S/d) Ratio

SE (kWh/m3)

Kurtkoy (Arcose) 13 5.0-5.5

Kartal (Limestone)

10 3.5-4.0

Doloyoba (Limestone)

23 7.0-7.5

Trakya (Siltstone) 11 6.0-7.0

4. DETERMINATION OF TBM CUTTER HEAD DESIGN PARAMETERS AND ESTIMATION OF TBM PERFORMANCE

4.1 Cutter spacing, number of discs, cutter head rotational speed

Cutter spacing / cutter penetration ratio is a fundamental parameter in efficient cutting process. There is always a minimum specific energy value for this ratio for a specific rock formation. However, for specific reasons machine manufacturers prefer usually taking cutter spacing between 7 and 8 cm, in this case the most important point comes to operate the TBM in optimum penetration conditions. Number of cutters (NC) in a TBM may be calculated using the Equation (1):

GAUGE

TBMC NS

DN +=2

(1)

where,

DTBM : TBM cutter head diameter (mm)

S : Cuter spacing (mm)

NGAUGE : Number of gauge cutters.

Rotational speed of the cutter head (RPM) may be calculated using Equation (2):

TBMD

VRPM = (2) where, V : Acceptable cutter speed, in most cases for gauge cutters the limit speed is taken as 150 m/min for a disc having a diameter of 432 mm. If DTBM = 6.57 m, NGAUGE = 3 and V = 120 m/min are taken, number of disc cutters are found to be 44 and maximum cutter head rotational speed is found to be 6 rpm.

4.2 TBM thrust

Optimum disc penetration per revolution of cutter head is calculated as: Optimum S/d = 10, for S = 80 mm, d = 80 / 10, d = 8 mm. Equation (3) is used to estimate total thrust (FT) of the machine for optimum penetration: LNC fFNFT ..= (3) where,

FN : Mean thrust for one disc cutter (kN)

fL : Coefficient for frictional losses

From Figure 6, for 8 mm depth of cut, cutter spacing of 8 cm and for 13 inch disc cutter, mean thrust force is found to be 6500 kgf and for 17 inch disc cutter this value is to be 20% higher, which is 7800 kgf. Thrust force of TBM for optimum penetration may be calculated as Follows:

==

===44

1 t.412kgf 411840 1.2 x 7800 x 44FN

n

i

For maximum TBM thrust force, peak thrust forces should be taken into account.

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==

===44

1 t.248kgf 236808 1.2 x 15600 x 44NF'

n

i

With a safety factor of 2.0, design value of the machine thrust may be taken as 1648 t.

4.3 Cutter head torque and cutting power

The following equations are used to calculate the cutter head torque (T) and the power (P) (Bilgin et. al., 1999) [2]:

4

... LTBMRC fDFNT = (4) where,

T : Cutter head torque, kNm

FR : Mean rolling force for one cutter (kN)

DTBM : Diameter of the cutter head in (m).

TRPMP60

2= (5) where,

P : Cutting power (kW)

T : Torque (kNm)

RPM / 60 : Rotational speed in (revolution per second) From Figure 6, for cutting depth of 8 mm, mean values of FR is found to be 750 kgf for 13 inch disc cutters. For 17 inch disc, this value is predicted to be 20 % higher or FR = 750 x 1.2 = 900 kgf. Hence,

2.14

.44

1

TBMn

iR

DFT ==

= (with frictional losses)

kNm 780kgm 78052 1.2 x 4

6.57 x 90044

1=== =

=

n

iT

However, peak values of rolling forces are 2.4 times higher than mean values, therefore expected peak torque values would be 780 x 2.4 = 1872 kNm. The power in optimum cutting conditions is calculated by taking the mean values of torque.

kW. 0947806062 == P

With 60% of total efficiency,

kW. 8176.0

490 ==P With a safety factor of 1.5, design value of machine cutter head power value may be taken as 1225 kW.

4.4 Net cutting rate and daily advance rate Net cutting rate can be calculated using Equation (6):

optSE

Pk. ICR = (6)

where, ICR : Net cutting rate, m3/h P : Power consumed in optimum conditions,

kW k : 0.8, Energy transfer ratio from cutter head

to tunnel face (Rostami et al.,1994)[3] SEopt = Optimum specific energy, kWh/m3.

/h.m 98kWh/m4.0

kW 4900.8x ICR 33 ==

For daily advance rate, the daily working hour and machine utilization time should be taken into account. An average value of 40 % machine utilization time is assumed for the calculation of daily advance rate. However, this value may go down to 20 % in difficult conditions. For 2 shifts of 10 hours working time for each shift and 20 % of machine utilization time, daily advance rate may be estimated as follows: Daily advance rate = 98 (m3/h) x 2 x 10 (h/day) x 0.2 / 33.9m2 (tunnel face area) = 11.5 m/day.

5. THE COMPARISON OF PREDICTED AND ACTUAL PERFORMANCE

The contractor Anadoluray Joint Venture asked the research group of ITU, Mining Engineering Department to carry out full scale cutting tests prior to ordering two TBM of 6.57 m in diameter. The cutting test results were sent to Herrenknecht

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Company to be considered in the manufacturing process. The machine parameters calculated after the full scale cutting tests and manufacturer design values are compared in Table 3. Herrenknecht TBM no 360 started excavating the tunnel line 2 on the 20th August, 2007 in open mode and the Herrenknecht TBM no 363 started excavating the tunnel 2 on line 1 on the 3rd November, 2007 in open mode. The first machine went through shaft 8 (Figure 7) on the 16th April, 2008 with an average of 11 m/day in very difficult conditions after a small modification on the cutter head.

The machine performance data is collected continuously by the contractor with the aid of a data acquisition system. The rock formation in the area is highly fractured Kartal Limestone with dasite and

andesite dykes. RQD values vary between 0 and 80 % with an average value of 21 %. As noted clearly by Dollinger and Raymer (2002) (4) the fractured zones affect tremendously the TBM performance. In most cases, the predicted TBM performance values are highly different than actual performance values which are under investigation in detail to discuss after the completion of the project. However, there are some area with competent rock formation which enables to compare the predicted and the actual TBM performance values. The rings representing these relevant areas and the performance values are presented in Table 4. For comparison, the optimum cutting conditions are considered. As seen in Figure 5, the optimum specific energy is obtained for cutter spacing / penetration ratio of 10. Bearing in mind that the

Table 3. The comparison of the machine parameters calculated after the full scale cutting tests and manufacturer design values

Disc Number

Maximum Thrust (kN)

Maximum Torque (kNm)

Cutter Head Power (kW)

Values calculated after cutting tests

44 1648 t 1872 kNm 1225 kW

Manufacturer design values

38 4257 t at 350 bars

1515 kNm at 5.5 rpm 5200 kNm at 1.6 rpm

4x315 kW

Figure 7. The Herrenknecht TBM-360 breaking through shaft 8

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cutter spacing is chosen as 8 cm, the optimum penetration comes to be 8 mm. For optimum conditions for S = 7 cm and penetration of 7 mm, the optimum thrust force for one disc is found to be 906 kgf. In this case penetration index is 906 / 7 = 1295 kgf/mm. This is a useful index to determine the cuttability characteristics of a rock formation. Bearing in mind that the disc number is 38, the penetration index of TBM in Kartal Formation is estimated to be 38 x 1295 = 49210 kgf/mm or 492

kN/mm. From Table 4, for relevant rings the mean rpm as found to be 2.6 and penetration rate to be 9.4 mm/rev, which makes an average net cutting rate of TBM as 9.4x2.6x3.14x6.57x6.57x10-3x60/4 = 50 m3/h. The predicted and actual values are compared in Table 5. As seen from this table actual and predicted values are very close to each other in competent rock, where the geological discontinuities are not dominant, considering the folding effect of RPM value.

Table 4. TBM-360 performance data in competent rock formation

Ring Number

Measured RPM

Measured Torque (kNm)

Penetration (mm/rev)

Penetration Index (kN/mm)

Advance Rate (mm/min)

54 2.8 1210 9 412 28 98 2.4 1130 10 515 25

246 2.5 2220 10 453 25 254 2.6 1790 8 545 22 279 2.7 1800 9 568 24 284 2.5 1870 9 544 23 287 2.6 1770 9 454 23 289 2.7 1880 8 502 23 307 2.6 1900 10 498 27 308 2.5 1400 10 491 25 340 2.9 2280 10 491 29 344 2.5 2220 9 444 24 347 2.5 1590 10 467 24 348 2.7 1950 9 470 23 349 2.6 1850 9 449 24 393 2.4 1450 10 452 30 453 2.9 2290 10 453 29 463 2.8 2450 10 463 29

Mean Actual Values

2.6+/- 0.15sd

1840+/- 360sd

9.4+/- 0.7sd

485+/- 39sd

25.4+/- 2.4sd

Table 5. Predicted and actual TBM performance values

Penetration Index (FN/d)

(kN/mm)

Torque (kNm)

Net Cutting Rate

(m3/h)

Daily Average Advance Rate at 20% Machine Utilization

Cutting Test Results at Optimum d=8mm for 6 rpm

492

1872

98

11.5 m/day

Actual Values at d=8-10mm for 2.6 rpm

485 1840 50 11-12 m/day

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6. CONCLUSIONS Tunneling activities like metro, sewerage and water tunnels are increasing tremendously in Istanbul. This study is about the determination of some design parameters and performance prediction of tunnel boring machines (TBM) using full-scale rock cutting test in the main rock formations encountered in the metro tunnel projects, Kadikoy-Kartal Metro Tunnels. Full scale cutting tests with disc cutters are performed for this purpose. It is proved that geological discontinuities affect tremendously TBM performance values and only in competent rock formations the laboratory cutting test results are in good agreement with actual values. However, it is proved also that laboratory full scale cutting tests are very useful tool in determining design parameters and performance prediction of a TBM for a specific job.

ACKNOWLEDGEMENT The authors are grateful to the following organization and people without their help this work would be impossible to be realized, Istanbul Technical University the contractor Anadoluray Joint Venture (Yapi Merkezi-Yuksel-Dogu-Yenigun-Belen Co), Istanbul Municipality, IETT, Project Director Mr. Ramih Mustu and the assistance of Turkish Scientific and Technological Organization (TUBITAK). REFERENCES

1. Yuksel, A., Sozak, N.N., Gulle, G., 2005. Engineering Geology report prepered for Kadikoy-Kartal Metro Project: KK-GE-TR-GN-004, Anadoluray Joint Venture, Istanbul.

2. Bilgin, N., Balci, C., Tuncdemir, H., Eskikaya, S., Akgul, M., Algan, M., 1999. The performance prediction of a TBM in TuzlaDragos sewerage tunnel. Proceedings of the World Tunnel Congress on Challenges for the 21st Century. Oslo, pp. 817827.

3. Rostami, J., Ozdemir, L., Neil, D.M., 1994. Performance prediction: a key issue in mechanical hard rock mining. Mining Engineer, November, pp. 1263-1267.

4. Dollinger, G.L., Raymer, J.H., 2002. Rock mass conditions as baseline values for TBM performance evaluation. North American Tunnelling Conference, pp. 3-7.

5. Bilgin, N., Copur, H., Balci, C., Feridunoglu, C., Tumac, D., 2006. Full scale rock cutting tests for TBM performanse prediction for Kadikoy-Kartal metro tunells. ITU Faculty of Mines, Technological Report Prepared for Anadoluray Joint Venture, Istanbul.

BEOGRAPHICAL DETAILS OF THE AUTHORS

Nuh Bilgin graduated in Mining Engineering from the Istanbul Technical University in 1973. He obtained a Ph.D. on mechanical excavation at the University of Newcastle Upon Tyne in 1977. He is currently professor and head of the Mine Mechanization and Technology

Division of the Mining Engineering Department of the Istanbul Technical University.

Hanifi Copur graduated in Mining Engineering from the Istanbul Technical University in 1987. He obtained a Ph.D. on mechanical excavation at the Colorado School of Mines in 1999. He is currently associate professor in the Mine Mechanization and Technology

Division of the Mining Engineering Department of the Istanbul Technical University.

Cemal Balci graduated in Mining Engineering from the Istanbul Technical University in 1993. He obtained a Ph.D. on mechanical excavation at the Istanbul Technical University in 2004. He is currently assistant professor in the Mine Mechanization and Technology

Division of the Mining Engineering Department of the Istanbul Technical University.

Deniz Tumac graduated in Mining Engineering from the Istanbul Technical University in 2001. He obtained a M.Sc. on mechanical excavation at the Istanbul Technical University in 2004. He is currently continuing his Ph.D. studies and research assistant in the Mine

Mechanization and Technology Division of the Mining Engineering Department of the Istanbul Technical University.

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Mustafa Akgul graduated from mechanical engineering Department of Istanbul Technical University. He worked in several underground construction and tunnelling projects. He is expert on mechanical tunnelling and currently responsible mechanical engineer from two TBMs running in

Anadoluray Project. He also teaches in Istanbul University, Mining Engineering Department.

Ali Yuksel graduated from Mining Engineering Department, Istanbul Technical University in 1981. he obtained MSc degree in the same department in 1983. He is a specialist in Geotechnics, an expert on mechanized tunnelling. He is currently working in Anadoluray Joint Venture.