A simplified excavation chamber pressure model for EPBM tunneling

This paper presents a simplified excavation chamber pressure model for earth pressure balance shield tunnel boring machine (EPBM) tunneling in granular soils, capable of predicting chamber pressure response during both excavation and standstill periods. Two physical processes, (1) compressible material flow, and (2) chamber fluid seepage, are modeled. The chamber pressure model is physics-based and is built upon chamber muck mass conservation. The model assumes muck behavior to be pressure-dependent and quasi-static. Given recorded EPBM operations, including advance rate, chamber additive injection rates and screw conveyor rotation speed, the model can predict the chamber pressure fluctuation with good accuracy, both during excavation and standstill periods. A case study using tunneling project data is included, where the model’s capability to simulate chamber pressure evolution during excavation of a single ring and multiple consecutive rings is demonstrated

TBM pressure models: observations, theory and practice

Mechanized tunnelling in soft ground has evolved significantly over the last 20 years. However, the interaction between the tunnel boring machine (TBM) and the ground is often understood through idealized concepts, focused mostly on the machine actions in detriment of the reactions from the ground. These concepts cannot be used to explain several mechanisms that have been observed during the construction of mechanized tunnels. Therefore, this paper presents the path from field observations to the theoretical developments to model the TBM-ground interaction more realistically. Some ideas on how these developments can be applied into practice are presented. Finally, a discussion is proposed about how an effective collaboration between academia and industry can alleviate the current concentration of knowledge in the state of practice

Performance Analysis Of Epb-tbm In Difficult Geological Conditions For Kadikoy – Kartal Metro Project

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2011Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2011Zor zemin şartlarında mekanize tünel kazıları sırasında ilk planlama zorluklarına bağlı olarak, projenin yürütülmesi sırasında sık sık sorunlarla karşılaşılmaktadır. Bu problemlerden bir tanesi de tünel açma makinesinin (TBM) performansının tahminindeki belirsizliklerdir. Bu çalışmada zor zemin şartlarının pasa basınçlı (EPB) TBM‟in performansına etkilerinin araştırılması amaçlanmıştır. Bu amaçla Anadoluray tarafından yürütülen Kadıköy Kartal Metro Projesi inşaatının Hasanpaşa Kavşağı Otosan arazisi arasında kalan 500 metrelik bölümü çalışma alanı olarak belirlenmiştir. Arazi çalışmalarında öncelikle bölgenin jeolojisi ve tünel güzergâhının fiziksel durumu detaylı olarak araştırılıp TBM ile tünel kazısında sorun yaratacak bölgeler tespit edilmiştir. Stabilite problemleri yaşanabilecek bölgeler için TBM karşıt ayna basıncı hesaplamaları yapılmıştır. Güzergâhtan geçiş sırasında karşılaşılan problemler kaydedilmiştir ve TBM veri toplama sisteminde kaydedilen raporlar incelenip her bir ring için ölçülen tork, baskı (itme) kuvveti, net kazı hızı ve tünel aynasına gelen arazi basınçları irdelenmiştir. Yapılan incelemeler sonucunda karşılaşılan problemlerin ve TBM performansını etkileyen parametrelerin başında jeolojik koşulların geldiği tespit edilmiştir. Elde edilen bulgular çerçevesinde zor zemin şartlarında TBM performansının düştüğü görülmüş ve bunun nedenlerinin başlıca kaya ile zeminin karışık olduğu tünel aynası koşulları, dayk-anakaya dokanak zonları, stabilite problemleri ve aşırı keski tüketimine bağlı duraklamalar olduğu tespit edilmiştir.Many problems are encountered during the mechanical excavation of the tunnels due to the difficulties in the preplanning phase of the project. One of these problems is that uncertainties on the prediction of performance of tunnel boring machines (TBM). The main purpose of this study is to analyze the effects of difficult ground conditions on an earth pressure balance (EPB) TBM. For this purpose, the alignment between Hasanpasa Crossroad – Otosan Land, around 500 m, of Kartal–Kadikoy Metro Project constructed by Anadoluray Joint Venture was selected as investigation area. The problematic locations and geological conditions were first defined. Face pressures were estimated for the areas where stability problems were expected. The problems encountered during the excavation were observed and recorded. Operational torque and thrust requirements, instantaneous penetration rates and face pressures were analyzed based on the data recorded by the TBM data logging system. Studies indicated that the most important parameter affecting the performance of the EPB-TBM was the geological conditions. Performance of the EPB-TBM decreased due to difficult ground conditions and the main reasons for that was rock-soil mixed face, main rock-dyke contact zones, face stability problems and stoppages due to excessive disc cutter consumption and replacement.Yüksek LisansM.Sc

A simulation-based software to support the real-time operational parameters selection of tunnel boring machines

With the fact that the main operational parameters of the construction process in mechanized tunneling are currently selected based on monitoring data and engineering experience without exploiting the advantages of computer methods, the focus of this work is to develop a simulation-based real-time assistant system to support the selection of operational parameters. The choice of an appropriate set of these parameters (i.e., the face support pressure, the grouting pressure, and the advance speed) during the operation of tunnel boring machines (TBM) is determined by evaluating different tunneling-induced soil-structure interactions such as the surface settlement, the associated risks on existing structures and the tunnel lining behavior. To evaluate soil-structure behavior, an advanced process-oriented numerical simulation model based on the finite cell method is utilized. To enable the real-time prediction capability of the simulation model for a practical application during the advancement of TBMs, surrogate models based on the Proper Orthogonal Decomposition and Radial Basis Functions (POD-RBF) are adopted. The proposed approach is demonstrated through several synthetic numerical examples inspired by the data of real tunnel projects. The developed methods are integrated into a user-friendly application called SMART to serve as a support platform for tunnel engineers at construction sites. Corresponding to each user adjustment of the input parameters, i.e., each TBM driving scenario, approximately two million outputs of soil-structure interactions are quickly predicted and visualized in seconds, which can provide the site engineers with a rough estimation of the impacts of the chosen scenario on structural responses of the tunnel and above ground structures

3D Modelling of an EPB Tunnel Drive in Mixed Geological Formation

Se simulará, mediante un modelo numérico 3D de elementos finitos, el proceso de excavación y construcción del túnel de la Línea 9 del Metro de Barcelona en el entorno de la zona Franca. Se validará el modelo, reproduciendo los movimientos del terreno, en superficie y en profundidad. Se estudiará la interacción del proceso de excavación con edificios cercanos

Influence of material conditioning on tools wear of EPBS machines using different laboratory test

Underground construction in urban areas that need more efficient transportation systems, energy and water supplies is a very challenging task, due to the complexity of the work itself and because surface disturbances and subsidences require to be minimized. In order to face the challenge and allow the excavation of tunnels even with low overburdens, Earth Pressure Balance Shields (EPBS) technology has been increasingly used in the recent years. EPBS is a type of tunnel boring machine (TBM) with earth pressure support. By transforming the excavated material into a soft paste that has plastic properties to be used as support medium, it is possible to balance the pressure conditions at the tunnel face allowing minimum settlement. In addition, uncontrolled inflow of soil and water into the machine is avoided and tunnelling process becomes more effective. In order to better understand soil behaviour and improve the performance of the EPBS machine, two variables are studied: soil conditioning and tools wear. During excavation with EPB machines the correct soil conditioning is a very important parameter to be controlled. For this reason, it is critical to perform preliminary tests with different conditioning agents in order to determine the most suitable reference dosage for an excavation project. Currently, soil conditioning is evaluated by performing slump tests and plasticity and homogeneity checks of the dough at laboratory scale. There is also the Extraction Test used to evaluate material extraction that is one of the most realistic tests to know the behaviour that soil could develop during excavation process. On the other hand, a very important but still less studied variable is the wear of EPBS metal parts like excavation tools, rotating head, shield and screw conveyor. Wear leads to a reduction in working yield due to the mentioned machine components lose their optimum properties and have to be replaced; consequently, downtime is required in order to execute proper maintenance, which is difficult and dangerous. Many aspects play key roles in the wear process like excavated medium, water content, applied pressure, soil conditioning and type of metal used for machine tools manufacturing. In fact, rocks and soil excavated during EPB work can be composed from any kind of minerals. Hard minerals increase the wear phenomenon that concerns all parts of the machine where there is friction between metallic part and the medium. For this reason, study of wear phenomenon is an extremely important issue for new projects with EPB excavation technology. Therefore, the objective of this work is to study of the influence of soil conditioning on tools wear and the relationship of the main factors associated to this phenomenon. In order to accomplish this goal, about 26150 kg of different soils were studied using 4 different wear test methods. These tests were based on the application of a test methodology already used in the Tunnels and Underground Works Laboratory of Politecnico di Torino and other new methodologies and equipment, developed with the aim of deepening the study of wear taking into account several variables that concern the construction of tunnels. Each methodology implemented has different benefits, limitations and scopes, but provides congruent technical results. Finally, prediction indexes were proposed in order to evaluate tool wear phenomenon and compare the effects of different soil conditioning. As a result, better decisions are made when choosing the ideal conditioning for EPB tunnelling, maximizing projects effectiveness and success

Mechanical behaviour of conditioned material for EPBS tunnelling

The rapid growth of the development of the cities all over the World, brought the necessity of bringing deeper the services and all the activities which are not strictly necessary above the ground like houses. This sudden demand of new tunnels obliged to push the excavation industry towards mechanized methods which allow to avoid settlements on the surface, where other structures and infrastructures are located. In this context EPB shield machines play a crucial role, as with a good control of this technology, a tunnel can be excavated basically everywhere, also below important structures. This implies the perfect knowledge of the geology but especially requires a precise study of the soil conditioning, in order to allow an effective counterpressure to the front. The development of preliminary laboratory tests, which means before the tunnel project starts, allows to assess the best conditioning set for each lithotype which can be encountered during the excavation. These tests are performed at room pressure, nevertheless recently the main goal is to study the conditioned mass at pressure conditions which can be found in an excavating chamber, which might influence the state of the mass itself. The aim of this work is the development of new techniques which can exactly reproduce this state, through the use and modification of techniques proper of the geotechnical engineering (shear and triaxial tests) and the design of new devices able to underline these aspects in detail. The new approach includes, as well as the consideration of a certain pressure condition, also the definition of an undrained condition used for testing, which allows to keep the conditioned mass in its original state for its study