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08:50-09:10 A Model to Predict the Performance of EPB-TBMs in a Complex Geology in Istanbul N. Bilgin, Istanbul Technical University; M. Namli, Medeniyet University and H. Copur, C. Balci, A. Shaterpour Mamaghani, Istanbul Technical University It is expected that more than 10 Billion USD will be spent in Istanbul in coming years on tunnel boring especially with EPB-TBMs. However the geology of Istanbul is very complex. Geologic formations changing from Paleozoic to Cenozoic ages cause tremendous problems due to frequently changed rock formations and andesite and diabase dykes. This paper summarizes a universal model to predict the performance of EPB-TBMs which is created upon the data base collected from several projects. The model is based ﬁrst on predicting ﬁeld speciﬁc energy and power consumed of TBMs using geo-mechanical properties of the excavated material and TBM diameter. Later net production rate is calculated using ﬁeld speciﬁc energy and power consumed by TBM. A methodology to predict machine utilization factor permits to calculate daily advance rates. The validity of the model is tested using the data obtained from two recent metro tunnel projects.
22 – 28 APRIL | MOSCONE CENTER | WTC2016 09:10-09:30 Pressure Distribution along the TBM Body in EPB Tunneling B. Hagan, E. Alavi, G. Frank and M.A. DiPonio, JayDee Contractors, Inc and L. Mori and M. Mooney, Colorado School of Mines The data from EPB cells located inside the pressurized chamber of EPB TBMs and also the data from the pressure sensors in grout lines are quite important in controlling the EPB operation. However, there have always been questions in regards to pressure distribution along the shield body. Could the pressure distribution data be used to come up with potential locations for ground loss? Does the overcut region, the space between the shield body and the maximum cut diameter, consist of broken material or EPB muck, or does that region consist primarily of void space? During free air interventions, how does pressure distribute along the TBM body?
To address these questions, one of the two EPB TBMs used in the Northgate Link Light Rail project in Seattle, WA is equipped with EPB cells in front and rear body to monitor the pressure distribution along the TBM body in addition to the standard 6 EPB cells located inside the cutterhead chamber and pressure sensors located at the grout lines. This paper discusses the results of this study and weighs on the valuable data that can be collected by using the shield pressure sensors.
09:30-09:50 Analysis of Effect of Waterhead on Stability of Excavation Face of Slurry Balanced Shield Z. Yang, Qingdao University of Technology; Q. Liu, West Coast Railway Transportation Co, Ltd and M. Zhang and X. Guan, Qingdao University of Technology In slurry balanced shield tunneling, how to ensure the safety of construction and to reduce the inﬂuence on the environment has arisen wide attention of scholars both at home and abroad. But now it is still in the stage of experience as to the instability mechanism of the slurry shield tunneling excavation and its stability analysis. Based on the large-diameter model tests and FLAC 3D, the effect of the different waterhead (non-water, 0.9m and 1.1m) on stability of excavation face of slurry balanced shield is investigated, and the stability mechanics is proposed. The results show that: waterhead heights play an important role on excavation face instability features of slurry balanced shield in sandy stratum, Regarding the different waterhead heights, the development mode of the excavation face instability features can be divided into non-water mode, lower-waterhead mode and higher-waterhead mode; soil arching is existed in the process of excavation face instability, the settlement of ground lags behind excavation face failure, the soil arching will block or eliminate the effects of ground settlement; excess pore water pressure need to be considered besides earth pressure and hydrostatic pressure when the supporting force is calculated.
WTC2016 | SAN FRANCISCO CALIFORNIA, USA WEDNESDAY 27 APRIL 09:50-10:10 Shield Tunnelling in Pure Sands – Merging the Application Fields of EPB and Slurry Shield Technology U. Maidl and M. Comulada, Maidl Tunnelconsultants and A. Mahfuz Monteiro, C. Henrique Turolla Maia and J. Claudio Di Dio Pierri, Constructora Norberto Odebrecht, Brazil Pure sands are typically the domain of slurry shields due to their high permeability and their granular characteristics. On the other hand, the Earth Pressure Balanced (EPB) shield machine technology has advanced in recent years with improved conditioning agents and shield machines that are equipped with slurry injection facilities and alternative mucking methods. These new EPB machines have steadily increased the range of application of the EPB technology. The contribution discusses the capacities and operational features of hybrid EPB vs. slurry shield technology in pure sands. At the example of the Metro Line 4 in Rio de Janeiro (Brazil), the contribution shows that EPB tunneling in pure sands is possible and it is compared with a state-of-the-art slurry shield project as the KASIG project in Karlsruhe (Germany). Furthermore, the control of the support pressure by means of foam conditioning and slurry injection in conjunction with a close, real-time monitoring of machine parameters is discussed.
10:10-10:40 Break 10:40-11:00 Study of Wear in Conditioned Granular Soil by Using a New Test Device C. Oñate Salazar, D. Martinelli, C. Todaro and D. Peila, DIATI and A. Boscaro, UTT, Mapei SpA The wear phenomenon in TBM machines is not a simple issue, as many parameters are playing an important role on the consumption of the tools during a tunnel excavation. The action of the wear due to the contact with the soil can occur on the excavation tools, on the cutterhead, in the excavating chamber and on the screw conveyor. The test developed at the Laboratory “Tunnelling and Underground Space Center” of the Politecnico di Torino is aimed to reproduce the interaction between the tools and the excavated material, simulating the excavation conditions in terms of soil conditioning and water content. The test, which is not standardized, is studied to evaluate the wear in a global point of view. The present work starts by testing the inﬂuence of the use of chemical agents during the conditioning phase on the drop of the wear phenomenon, in terms of metal weight loss.
22 – 28 APRIL | MOSCONE CENTER | WTC2016 11:00-11:20
Earth Pressure Balance TBM Soil Conditioning:
It’s About the Pressure M. Mooney, Y. Wu, L. Mori and R. Bearce, Colorado School of Mines, and M. Cha, Texas A&M University Proper soil conditioning is critical for effective earth pressure balance (EPB) TBM tunneling. The formation soil at the cutterhead must be transformed into a highly compressible, low shear strength and low permeability paste within the excavation chamber to allow optimal EPB performance. This behavior must be maintained for a certain residency time. The vast majority of published studies on conditioned soil behavior have been performed under atmospheric conditions; however, the desired soil behavior must occur under chamber pressures that can reach 5-7 bar.
The inﬂuence of pressure on conditioned soil is signiﬁcant and is dramatically different than behavior under atmospheric pressure. This paper illustrates how pressure inﬂuences conditioned soil behavior and how atmospheric test results must be viewed in the context of expected chamber pressures. The inﬂuence of pressure on bubble-soil interaction (including with time) is shown through digital image analysis. The compressibility, shear strength, and abrasivity of conditioned soil under pressure is presented and explained in terms of density, soil and air compressibility and porosity.
11:20-11:40 Performance Optimization in Clogging Soils through Process Controlling U. Maidl, M. Comulada and J. Stascheit, Maidl Tunnelconsultants Cohesive soils are notorious for causing clogging of the cutter head and the excavation chamber of tunnel boring machines (TBMs). While clogging leads to a drastic reduction in excavation performance, it further induces higher wear of tools and other parts of the cutter head and may even prevent a controlled support of the tunnel face and, thus, lead to face collapse and excess settlements or sinkholes.
Employing well-balanced soil conditioning techniques, the clogging tendency can be signiﬁcantly reduced. The monitoring and control of soil conditioning as well as the timely detection of potential clogging tendencies require a close monitoring of all relevant machine parameters and measurements. To this end, a reliable and powerful Process Controlling software that gathers all machine and process-related information is a prerequisite for successful mitigation of clogging-induced problems. The remainder of this contribution is organized as follows: First, a brief introduction to the Process Controlling system PROCON is given. Afterwards, the mechanisms and mitigation techniques of clogging are discussed. Finally, an example is given how Process Controlling has been employed to soil conditioning in a tunneling project with highly clogging soils.
WTC2016 | SAN FRANCISCO CALIFORNIA, USA WEDNESDAY 27 APRIL 11:40-12:00 Transient Face Support in Slurry Shield Tunneling Due to Different Time Scales for Excavation Sequence of Cutting Tools and Penetration Time of Support Fluid M. Thewes, B. Schoesser And Z. Zizka, Ruhr-University Bochum The support pressure of a slurry shield corresponds to the in situ earth and groundwater pressure to ensure the stability of the tunnel face. The support ﬂuid (bentonite suspension) penetrates from the excavation chamber into the pore space and transfers the support pressure to the granular structure of the soil within this zone. At the same time, the cutting tools rotate periodically with the cutting wheel and remove the penetrated soil up to a certain cutting depth at the face. Shortly after the tool passing the penetration process starts again. Both, the support pressure and the soil excavation, act in the same direction at the tunnel face, but they are subject to different cyclic intervals. This relationship between the time needed for the transient penetration process and the interval of the cyclic passage of the cutting tools at a local point at the face is examined and the impact onto the global face stability is discussed.
12:00-12:20 Assessment of EPB Soil Conditioning on Two TBMs by Using Apparent Density L. Mori and M. Mooney, Colorado School of Mines and E. Alavi, G. Frank and M. DiPonio, JayDee Contractors Inc A study was conducted on the N125 project in Seattle to investigate the use of apparent density as an assessment tool for the effectiveness of soil conditioning. The formation of an air bubble as well as the plugging of cutterhead and excavation chamber can be a result of improper soil conditioning. Both air bubble formation at the top of the excavation chamber and developing plugging issues can be identiﬁed by analyzing the apparent densities in the excavation chamber. In this study, apparent densities less than unity were observed in the upper portion of both northbound and southbound TBMs, suggesting the presence of an air bubble. Apparent densities greater than the in-situ soil density were observed in the lower portion of the excavation chamber.
Particularly high values of apparent density were coincident with clogging observed at multiple locations along the alignment. The combination of less than unity upper chamber apparent density and very high apparent density in the lower portion of the chamber are related, and indicate the inability of the TBM to effectively condition and mix the soil in the chamber.
22 – 28 APRIL | MOSCONE CENTER | WTC2016 Posters (On display in the exhibit hall during exhibit hours. Authors will be at their poster from 13:00-14:00 for discussion.) Microscopic and Experimental Analysis of the Tribological System of TBM-tools J. Küpferle, A. Röttger, W. Theisen and M. Alber, Ruhr-University Bochum Wear of TBM tools has a major inﬂuence on the advance rates of a tunneling progress. Wear-prediction models are based (amongst others) on the abrasivity of the present geology, which is determined with the help of laboratory tests. To evaluate the results from such tests in a reasonable context, in this work the tribological system TBM-tool is considered from the view of materials technology. Therefore, microstructure of different application-oriented materials are presented and discussed in terms of their wear behavior respectively wear-resistance. The signiﬁcant inﬂuence of the tool-materials on the abrasivity of the geology and thus the inﬂuence on wear-prediction models has been pointed out. Furthermore, LCPC-, Cerchar- and nano-scratch-experiments have been performed to conﬁrm the aforementioned statements. The material-dependent wear-mechanisms and their correlation in terms of tunneling have shown that it is mandatory to consider the complete tribological system to estimate the wear of TBM tools.
The Interplay of Face Support Pressure and Soil Permeability on Face Stability in EPB Tunneling P. Sitarenios, D. Litsas and M. Kavvadas, National Technical University of Athens The paper discusses the results of 3D ﬁnite element analyses to investigate the effect of face support pressure and soil permeability on face stability conditions in EPB tunnelling. Two main types of face behavior are identiﬁed: Undrained conditions ahead of the tunnel face, typically occurring in soils with permeability less than about k=5 10-7m/s, are shown to be favourable for face stability;
analyses show that an applied face pressure comparable with the initial hydrostatic pore pressure is sufﬁcient for adequate face stability, even for soils of relatively low strength. Drained or partially conditions, typically occurring in soils with permeability higher than about k=5 10-6m/s, show that face stability is strongly dependent on the effective stress of the muck; the presence of even a small effective stress in the muck is very beneﬁcial for face stability conditions and can be a possible explanation of successful EPB tunnelling through relatively permeable soils.