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1 ITA - AITES WORLD TUNNEL CONGRESS April 2018 Dubai International Convention & Exhibition Centre, UAE POSTER PAPER PROCEEDINGS

2 Effect of Soil Conditioning on Performance of an EPB TBM: from Laboratory to Mahmutbey- Mecidiyekoy Metro Tunnels in Istanbul Hanifi Copur1,*, Emre Avunduk1, Deniz Tumac1, Cemal Balci1, Nuh Bilgin1, Aydin Shaterpour Mamaghani1, Sahand Tolouei1, Gökhan Erkuş2, Sinan Acun2, Ugur Ates1 1,* Istanbul Technical University, Mining Eng. Dept., Istanbul, Turkey, itu.edu.tr 2 Gulermak-Kolin-Kalyon Mahmutbey-Mecidiyekoy Metro Construction JV, Istanbul, Turkey ABSTRACT The basic purpose of this study supported by the Scientific and Technological Research Council of Turkey (TUBITAK, Project No: 213M487) is to analyze the effects of soil conditioning on the field performance of an EPB TBM used for excavation of the Mahmutbey-Mecidiyekoy metro tunnels having a total length of around 18.5 km (double tube) in Istanbul. Soil samples were obtained during the excavation of Kazim Karabekir Station in where the silty sand lithological unit of Gungoren Formation was dominant. Natural water content, specific gravity, grain size distribution (sieve + hydrometer), consistency limits (liquid limit and plastic limit of only the fines) of the silty sand sample were determined to characterize the sample in the laboratory. Mixing (with power measurement), cone penetrometer, vane shear and flow table tests were performed to find out optimum soil conditioning parameters for the mixture of soil and foam at natural water content (17%), Foam Concentration Ratio (CF) of 3% and Foam Expansion Ratio (FER) of 16 by varying Foam Injection Ratio (FIR) between 5% and 30%. The laboratory studies indicated that optimum conditioning of the sample were obtained at FIR of 20-25%. Then, the field performance of the EPB TBM working in closed mode (instantaneous penetration rate, cutterhead torque, and TBM thrust force) was recorded, observed and analyzed for the rings between 790 and 920. It was seen that the average CF of 1.5%, FER of 18 and FIR of between 50-75% was the conditioning parameters preferred in the field (half of the CF and 2-3 times the FIR defined on the laboratory). It was determined that there were good and strong relationships between the field excavation performance (penetration rate and TBM thrust force) and FIR and FER values applied in the field. Any relationship between the cutterhead torque and FIR and FER could not be detected. Keywords: EPB TBM, Soil conditioning, Excavation performance, Optimization. 1. INTRODUCTION The excavation performance of EPB TBMs depends on effectiveness of soil / muck conditioning performed by injecting special foams (air + water + foaming agents) to the different parts of excavation chamber. Performance may be unexpectedly very low, encountering many stoppages and delays increasing the costs, resulting in ground deformations giving harm to the buildings and environment. Therefore, selection, design and predicting the performance of these machines become very important in terms of feasibility, planning and project economics. Proper design / optimization of the soil conditioning according to the formation to be excavated affects directly the excavation performance of these machines. 1

3 Conditioning of soil or muck should provide for a homogeneous, pulpy and plastic muck with low internal friction and permeability (Thewes, 2007a,b,c; Peila et al., 2007, Avunduk et al., 2017a,b). Proper soil conditioning would enable higher penetration rate with lower torque and power requirement, lower clogging, transportation and stability problems, lower abrasive wear on metal parts of TBMs (Jancsecz et al., 1999; Langmaack, 2000, Thewes et al., 2010, 2012). Efnarc (European Federation of National Associations Representing Producers and Applicators of Specialist Building Products for Concrete) provided some suggestions on soil conditioning by laboratory testing and stated that these suggestions might not work for some soils (Efnarc, 2005). The soil conditioning design suggestions based on size distribution of soils given by some authors (Langmaack, 2007; Budach and Thewes, 2015) are also considered as insufficient (Thewes and Budach, 2010; Thewes et al., 2012; Budach and Thewes, 2015). The basic problem of the conditioning tests performed in laboratory is that the soil and the foam are mixed in the atmospheric pressure. This does not characterize the real behavior of foams under face pressure (Thewes et al., 2012; Mooney et al., 2016). However, the tests enable basic understanding of feasibility, processes and interactions during soil conditioning for EPB TBM tunneling operations (Galli and Thewes, 2016; Avunduk et al. 2017a,b). The basic purpose of this study is to analyze the effects of soil conditioning on the field performance of an EPB TBM used for excavation of the Mahmutbey- Mecidiyekoy metro tunnels having a total length of around 18.5 km (double tube) in Istanbul. Soil samples were obtained during the excavation of Kazim Karabekir Station in where the silty sand lithological unit of the Gungoren Formation was dominant. The natural water content, specific gravity, size distribution (sieve + hydrometer), consistency limits (liquid limit and plastic limit of only the fines) of the silty sand sample were determined to characterize the soil sample in laboratory. Mixing (with power measurement), cone penetrometer, vane shear and flow table tests were performed to find out optimum soil conditioning parameters for the mixture of the soil and foam at natural water content (17%), 3% Foam Concentration Ratio (CF) and Foam Expansion Ratio (FER) of 16 by varying the Foam Injection Ratio (FIR) between 5% and 30%. Then, the field performance of the EPB TBM (instantaneous penetration rate, cutterhead torque, TBM thrust force) working in closed mode was recorded, observed and analyzed for the rings between 790 and 920. Finally, performance of the EPB TBM was correlated with the soil conditioning parameters applied in the field. 2. MAHMUTBEY-MECIDIYEKOY METRO TUNNELS Mahmutbey-Mecidiyekoy Metro Project includes 18.5 x 2 km (double tube) tunnels. Gulermak-Kolin-Kalyon Metro Construction JV was the contractor and constructed the line by both TBMs and conventional (sequential) tunneling method. The job owner is Istanbul Metropolitan Municipality. Almost half of the alignment was excavated by three EPB TBMs, having different brands. 2 The metro line constructed in a highly populated part of Istanbul includes 15 stations. Excavation of the line started in Nisan 2014 and has already been completed in August Mecidiyekoy-Kabatas extension of the line (~5 km) has already been under construction by another contractor company. The alignment passing through the provinces of Sisli Kagithane Eyup Gaziosmanpasa Esenler - Bagcilar is seen in Figure 1.

4 The tunnels were lined with segment rings of 6 pieces, having a thickness of 30 cm, inner diameter of 5.70 m, outer diameter of 6.30 m and length of 1.40 m. The void / annulus between the segments and the ground were filled with grout injection. The excavated material was transported to the surface by a belt conveyor. Working pattern was 7 days/week, 2 shifts/day and 12 hours/shift. The soil samples used in this study were taken from the Kazim Karabekir Station. Field measurements of the EPB TBM performance were between the rings 790 and 920 (between Kazim Karabekir and Yenimahalle Stations). Some of the technical features of the EPB TBM used for excavation of the alignment between Kazim Karabekir and Yenimahalle Stations is presented in Table 1. A photograph of the EPB TBM is given in Figure 2. The general geology of the studied alignment consists mainly of Pliocene aged Gungoren Formation including red-brown and micaceous gravels, sands, clays and silts. The underground water table was below the tunnel axis in the studied area. The soil sample taken from the site for this study was silty sand. Figure 1. Alignment of the Mahmutbey-Mecidiyekoy Metro line Table 1. Some of the technical features of the EPB TBM 3

5 3. EXPERIMENTAL PROCEDURES Figure 2. A photograph of the EPB TBM The soil sample were obtained from the excavations of Kazim Karabekir Station in the tunnel axis level. The natural water content, specific gravity, size distribution (sieve + hydrometer), consistency limits (liquid limit and plastic limit of only the fines) of the silty sand sample were determined to characterize the soil samples in the laboratory. Mixing (with power measurement), cone penetrometer, vane shear and flow table tests were performed to find out optimum soil conditioning parameters for the mixture of the soil and foam at natural water content (17%), Foam Concentration Ratio (CF) of 3% and Foam Expansion Ratio (FER) of 16 by varying the Foam Injection Ratio (FIR) between 5% and 30% with 5% incremental steps. Foaming agent used in the tests was the same as the one used in the field. The foam was generated in the soil conditioning laboratory of the Istanbul Technical University by using a typical laboratory scale granular filled type foam generator. The foam was applied as soon as possible it was generated to keep its basic time dependent stability properties as suggested by Thewes et al. (2012). The testing procedures and standards for characterizing the soil sample are: the natural water content (ASTM D ), specific gravity (ASTM D ), particle size distribution by means of sieve analysis (ASTM D ) for samples having grain size greater than 75 μm and hydrometer methods (ASTM D ) for samples having grain size smaller than 75 μm (No. 200 Sieve), and consistency (Atterberg) limits (liquid limit by BS and plastic limit by ASTM D E1). 4 The testing procedures and standards for characterizing the soil and foam mixtures are mixing test with power measurement (Efnarc, 2005), fall cone penetration (BS ), vane shear strength (ASTM D2573M-15), and Flow table (DIN EN 1015-

6 3). The soil class was determined based on the unified soil classification system (ASTM D ). 4. EXPERIMENTAL RESULTS The results of the sieve analysis and hydrometer tests indicated that the sample contained 87% of sand, 10% of silt and remaining clay and gravel (Figure 3). According to unified soil classification it was determined as silty sand. However, it should be stated that there was also interbedded sandy silt along the studied alignment (61% silt and 31% sand). All of the conditioning tests were performed on the silty sand sample, since it was more difficult to excavate silty sand than sandy silt with an EPB TBM. Figure 3. Particle size distribution of the silty sand sample The natural water content of the sample was determined as 17%. The liquid limit of the fines of the sample was determined as 27.3% and its plastic limit was 0%. The specific gravity was determined as 1.90 g/cm3. The characterization tests for the soil and foam mixture were performed at natural water content (17%), CF of 3% and FER of 16 with varying FIR values. The results of the mixing tests are presented in Figure 4. As seen, the net power consumption drops to a certain minimum at 20% of FIR and levels off beyond this. The mixing tests were also indicated that there was no clogging / adhesion (of the sample) to the blade of the testing device, of which one would not expect any clogging / adhesion problem in the field. The results of the fall cone penetration tests are summarized in Figure 5. As seen, the optimum consistency, which requires 20 mm of cone penetration, was obtained at 20% of FIR. 5

7 Figure 4. Variation of power consumption with FIR during mixing tests Figure 5. Variation of fall cone penetration with FIR The results of the flow table tests are summarized in Figure 6. As seen, the optimum consistency, which requires 13 to 14 cm of flow diameter was obtained between 20 to 25% of FIR. The results of the vane shear tests are summarized in Figure 7. As seen, the shear strength of the sample dropped to none at 20% of FIR. The experimental results indicated that the silty sand could be easily excavated at 20 to 25% of FIR, 3% of CF and 16 of FER by using the foaming agent used by the contractor company. Some photographs taken during experiments are seen in Figure 8. 6

8 Figure 6. Variation of excess flow diameter (in flow table test) with FIR Figure 7. Variation of vane shear strength with FIR Figure 8. Sample photographs taken during conditioning tests 5. FIELD PERFORMANCE AND ITS RELATIONSHIPS WITH FIR AND FER The field performance of the EPB TBM between the rings 790 and 920 along the tunnel alignment between the Kazim Karabekir and Yenimahalle Stations was obtained from the TBM data logger, and the excavation in this section was observed closely in the field. The applied conditioning parameters were average FER of 18 (15 to 24) and FIR of 50 to 100% (mainly 50 to 75%) at CF of 1.0 to 1.5%. The average face pressure applied was 2 to 3 bar along the studies rings. The CF values applied by the contractor representatives were almost half to one third of the suggested by the 7

9 experimental studies. The FIR values applied by the contractor representatives were almost two to four times the suggested by the experimental studies. Average FER value applied in the field was almost the same with the one used in the experimental scale. The contractor chose lower CF with higher FIR. It is a known fact that the sizes of the foam bubbles are affected by pressure: increased pressure reduces the bubble size (Mooney et al., 2016). However, the effect of bubble size on excavation performance has not been investigated in detail. On the other hand, frequent change of the ground from silty sand to sandy silt might have an effect on the excavation performance and operational characteristics of the conditioning parameters. Any meaningful relationship between FIR and TBM thrust, as well as cutterhead torque, could not be found. The relationship between EPB TBM unit penetration (penetration per revolution of the cutterhead) and FIR is given in Figure 9. As seen, the penetration decreases with the increasing FIR, which is opposed to the practical expectations. This could be explained by the operator behavior such that when the excavation becomes difficult (decreasing penetration), the FIR values are increased to ease the excavation. Avunduk et al. (2017b), Marcheselli and Peron (1995) and Mori et al. (2016) also observed or stated similar results on the face pressured cases. Figure 9. Variation of unit penetration with FIR As an additional study, the data was grouped for each 5% of FIR; for example 50 to 55%, 55 to 60%, etc. The reciprocating average EPB TBM performance values were also evaluated accordingly for each FIR group with respect to the segmental rings. Any significant relationship could not be found between cutterhead torque and FIR, as well as FER, for the grouped data. The relationship between EPB TBM thrust force and FIR is seen in Figure 10. As seen, thrust force increases with increasing FIR, which is opposed to the practical expectations. This also reflexes the operator behavior when the excavation becomes difficult. The relationship between EPB TBM unit penetration and FIR is seen in Figure 11. As seen, unit penetration decreases with increasing FIR, as similar to the one obtained in Figure 9. 8

10 It was also observed that when the excavation becomes difficult, the operator increases also FER to obtain economic benefit on foam consumption (Figure 12). Figure 10. Variation of EPB TBM thrust force with FIR for grouped data Figure 11. Variation of unit penetration with FIR for grouped data Figure 12. Variation of unit penetration with FER for grouped data 7. CONCLUSIONS The optimum conditioning parameters defined based on laboratory experiments performed on the silty sand sample did not match with the operator s preference applied in the field for an effective / easy excavation / without any problems. One 9

11 of the reason for that might be different behavior of the foam under the applied face pressure of around 2 to 3 bar. The other one might be the alternating sandy silt lithological unit. The preferred foam concentration in the field was around ½ to 1/3 of the one tested in the laboratory. The preferred foam injection ratio in the field was around 2 to 3 times of the one determined in the laboratory. The foam expansion ratios were similar in the field and the laboratory. The penetration rate had a good relationship with foam injection ratio; foam injection ratio increased when penetration rate decreased. This was in opposed to the practical expectations, yet it has been a common observation in some other projects throughout the world. TBM thrust requirement had good relationship with foam injection ratio; thrust increased with increasing foam injection ratio. There was no relationship between cutterhead torque and foam injection ratio. ACKNOWLEDGEMENTS This study forms part of the unpublished PhD thesis of Emre Avunduk. The authors are grateful to the Scientific and Technological Research Council of Turkey (TUBITAK) for their valuable support (Project No: 213M487), and the Istanbul Technical University (ITU) Research Foundation (BAPSO Project No: 37793). We also thank the representatives of Gulermak-Kolin-Kalyon Construction JV for permitting us to conduct research in the Mahmutbey-Mecidiyekoy Metro Tunnels. REFERENCES ASTM, D , Standard test methods for amount of material in soils finer than No. 200 (75-μm) sieve. ASTM, D , Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass. ASTM, D , Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System). ASTM, D422 63, Standard Test Method for Particle-Size Analysis of Soils. ASTM, D E1, Standard test methods for liquid limit, plastic limit, and plasticity index of soils. ASTM, D854-14, Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer. Avunduk, E., Tumac, D., Tolouei, S., Copur, H., Balci, C., Bilgin, N., 2017a. Effect of Conditioning on Soil Workability determined by Mini-Slump and Flow Table Tests. In: Proceedings of the World Tunnel Congress 2017, Bergen, Norway. 10 p. Avunduk, E., Copur, H., Tolouei, S., Gumus, U., Altay, U., 2017b. Effect of Adhesion on EPB TBM Performance. In: Proceedings of the World Tunnel Congress 2017, Bergen, Norway. 6 p. BS, , Methods of test for soils for civil engineering purposes. Classification tests. 10

12 Budach, C., Thewes, M Application ranges of EPB shields in coarse ground based on laboratory. Tunnelling and Underground Space Technology 50: DIN EN , Methods of test for mortar for masonry - Part 3: Determination of consistence of fresh mortar (by flow table). Efnarc, Specification and guidelines for the use of specialist products for mechanized tunnelling (TBM) in soft ground and hard rock. European Federation Dedicated to Specialist Construction Chemicals and Concrete Systems. Galli, M., Thewes, M Rheology of Foam Conditioned Sands in EPB Tunneling. In: Proceedings of the World Tunnel Congress, San Francisco, April. Jancsecz, S., Krause, R., Langmaack, L Advantages of soil conditioning in shield tunneling, experiences of LRTS Izmir. In: Proceedings of the World Tunnel Congress, Oslo, pp Langmaack, L Soil Conditioning. TBM Conference Organized by BASF, Istanbul, February, pp: 7-9. Langmaack, L., Advanced technology of soil conditioning in PB shield tunnelling. In: Proceedings of the North American Tunneling Congress, 16 p. Marcheselli, P., Peron, J.Y Construction of the Passante Ferroviario link in Milano, Lots 3p - 5p -6p - Excavation by large earth pressure balanced shield with chemical foam injection. In: Proceedings of the Rapid Excavation Tunneling Conference, pp Mooney, M., Wu, Y., Mori, L., Bearce, R., Cha, M Earth pressure balance TBM soil conditioning: It's about the pressure. In: Proceedings of the World Tunnel Congress, San Francisco, April. Mori, L., Alavi, E., Baratta, C., Dobbs, T., Sullivan, B., Encapsulated oil additive application in earth pressure balanced (EPB) tunneling A case study. In: Proceedings of the World Tunnel Congress, San Francisco. Peila, D., Oggeri, C., Vinai, C Screw conveyor device for laboratory tests on conditioned soil for EPB tunnelling operations. Journal of Geotechnical and Geoenvironmental Engineering 133 (12), Thewes, M. 2007a. Mechanized urban tunnelling Machine technology. The 3rd Training Course Tunnelling in Urban Area. In: Proceedings of the World Tunnel Congress, Prague, 42 p. Thewes, M. 2007b. TBM tunnelling challenges redefining the state of the art. In: Proceedings of the World Tunnel Congress, Prague. Thewes, M. 2007c. Shield tunnelling technology to mitigate geotechnical risks. In: Proceedings of the 2nd Symposium on Underground Excavations for Transportation, Istanbul Technical University, pp Thewes, M., Budach, C Soil conditioning with foam during EPB tunnelling. Geomechanics and Tunnelling 3 (3)

13 Thewes, M., Budach, C., Beziujen, A Foam conditioning in EPB tunneling. In: Proceedings of the 7th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground, Roma, pp Thewes, M., Budach, C., Galli, M Laboratory tests with various conditioned soils for tunnelling with earth pressure balance shield machines. In: Proceedings of the 4th BASF TBM Conference, London. 12

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