Tunneling Machine Research Articles

Model for Estimation of Time and Cost for Tunnel Projects Based on Risk Evaluation

In the planning and procurement phases of tunnelling projects, numerous decisions have to be made regarding tender price and budget. Many case studies have shown that, in practice, the predicted costs and time schedules are often exceeded. This paper describes a study of the various risk factors in machine tunnelling and their differing impacts on cost and time. It has been concluded from the study that it is important to make a clear distinction between normal cost and time, and the undesirable events that cause exceptional cost and time. Existing decision-aid estimation models consider variation of the risk factors, but do not consider normal cost or time separately from undesirable events. Usually, estimations of project cost and time are made in a deterministic manner, but this does not allow one to consider uncertainty in cost and time variables. However, if the variables are treated probabilistically, the total cost of tunnelling can be expressed as a distribution curve, and a decision can be made on the tunnelling method by comparing the respective cost and time distributions. Based on such decisions, the budget and tender price can be determined separately, both by the client and contractor respectively. To meet the demands placed on decision-making for tender and procurement for currently favoured construction-contracting methods, a new model for estimating tender price and budget has been developed, and is described in this paper. This estimating technique has been applied to a case study of the Grauholz Tunnel. The predictions obtained from the estimation model are shown to be realistic, as the total construction cost and time obtained from the model correspond fairly well to the actual construction cost and time. The separate estimation of normal cost and time and exceptional cost and time contribute to the clarity of the results. The use of the proposed model also shows that the tunnelling method most suitable for the actual geological and hydrogeological conditions can be selected by this method.

Design and development of tunnelling equipment in a model test

Tunnel model test using a small scale tunnelling machine is useful for the simulating tunnelling processes and investigating ground behaviour during tunnel excavation. Advanced mechatronics along with up-to-date machining and control technologies has made it possible to fabricate such machine. These technologies, however, needs to test in a gravity field condition or centrifuge field condition. This paper presents the design concepts of small scale shield tunnelling machine and simulation method for tunnelling processes which could simulate various aspects of tunnelling process and monitor the ground behaviour. Problems of earth pressure acting on the lining of a shield tunnel is focused. This paper presents the simulation method for tunnelling processes and the design method for tunnelling machines with special reference to the problem of earth pressure acting on the lining of a shield tunnel. The paper then introduces and verifies the operation for tunnelling machines in the 1 g field by means of checking the reproducibility of experiment data and their comparison with data in the field. A general view of the model tunnelling machine is shown below. Details of the mechanisms of this machine are described in figure below. Two main tunnelling mechanisms were considered in the development of this machine: (i) The machine provides an overcut in order to model the ground loss that occurs on tunnel installation, (ii) The full face cutting head supports the earth to minimise the ground deformations in front of the tunnel face. It was found that the results of the stress change obtained from model tests using the machine developed in this research fall well within the range of values measured in the field. It is concluded that the results of tunnelling simulation obtained from the model tests using the developed tunnelling machine fall well within the range of values measured in the field. It is recommended that the developed small scale tunnelling machine is useful for the simulating tunnelling processes and investigating ground behaviour during tunnel excavation in experimental work. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Wastewater flow transfer tunnel: design and construction

This paper discusses the design and construction of a 10·5 km long, segmentally lined, flow transfer tunnel. It covers the detailed lining and shaft designs, selection criteria for the tunnelling machines, shaft and tunnel construction methods, and specialist ground treatment. The paper discusses several construction problems encountered with shaft sinking and tunnelling, and describes how these were resolved. Particular note is made of caisson sinking of shafts and the design of the tunnel entry and exit portal eyes. Jet grouting in the varying ground strata around these portals and on other areas of the contract is considered.

Wastewater flow transfer tunnel: design and construction

This paper discusses the design and construction of a 10·5 km long, segmentally lined, flow transfer tunnel. It covers the detailed lining and shaft designs, selection criteria for the tunnelling machines, shaft and tunnel construction methods, and specialist ground treatment. The paper discusses several construction problems encountered with shaft sinking and tunnelling, and describes how these were resolved. Particular note is made of caisson sinking of shafts and the design of the tunnel entry and exit portal eyes. Jet grouting in the varying ground strata around these portals and on other areas of the contract is considered.

A multifunctional testing device for rock fragmentation by combining cut with impact

Mechanical rock fragmentation is widely used in the fields of mineral resources exploitation, geological prospecting, tunnel excavating, civil engineering construction and national defence building, etc. At home and abroad researches on loading ways of rock fragmentation were mainly concentrated on the single static pressure or impacting loading, and the optimum loadings as well. Recent studies on brittle fracture showed that stress impulse can effectively improve the propagation of the crack, and the combination of impact and static pressure can increase the effect of breakage. In order to further understand the feasibility and efficiency of the cutting-impact rock fragmentation technology, a multi-function testing device was developed and its major parameters were analyzed by the authors. Principally the method of fragmenting rock by cutting-impact is putting a cutter on the surface of rock, applied with horizontal cutting force, vertical static pressure and impact load, and then the rock is broken under the combined loading. The multi-function testing device was designed on the basis of the above mentioned principle of rock fragmentation. It includes three parts: the static loading mechanism, the impact mechanism and the cutting mechanism. To carry out impact with different energy, the hammer's mass were designed to eight classes: 16.0, 18.5, 21.0, 23.5, 26.0, 28.5, 31.0 and 33.5 kg. According to the whole structure of the test setting, the largest stroke was chosen to be 300 mm. The low frequency which is adjusted by buncher and f=30-50 min-1 were selected. The device can conduct single breaking rock tests including cutting under horizontally static load as well, fragmentation under impact load and indentation under static load, and combined cutting impact test under the dynamic and static load. Not only can it be applied for single cutter test, but also for multi-cutters or roller cutter test. Granite and concrete samples with different strength were tested on the testing machine by PDC (Polycrystalline Diamond Compact) flat cutters and carbide alloy cutters under different loadings. The results show that the testing parameters are adjustable and the data are reliable. The testing device is a suitable and easy to operate one, and has reasonable structure in laboratory for simulating rock drilling or breaking under the combination of dynamic and static load, and has much value in designing and manufacturing of tunnel machine and mechanized excavators. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Development and practical applications of twin-screw shield method

As Japan's population becomes more concentrated in large cities, the demand for urban facilities and diverse urban functions is resulting in greater congestion underground. Meeting this demand requires the development of a low-cost technology for constructing large-scale facilities at great depths below the surface. The current dominant technology for constructing tunnels in urban areas is the shield method, which includes both the slurry and mud-pressure methods. The latter method is seldom used at depths of 30 m or more below the surface because at such depths, the face of the tunnel is subject to high water pressures, which cause the muck and groundwater to spurt out from the screw conveyor of the shield-tunneling machine. The soil pressures at the tunnel face then become uncontrollable, causing the ground around the tunnels to deform. To solve this problem, Taisei Corp. and Ishikawajima-Harima Heavy Industries Co. Ltd. began researching screw conveyors in 1996 and recently developed the twin-screw (TS) shield method. In the twin-screw shield method, the muck is continuously and stably discharged by automatically controlling the rotational speed of the twin-screw conveyor. This maintains the desired soil pressure at the tunnel face at all depths, no matter how fast or slow the machine is advanced. The two screws are engaged and rotated in opposite directions, creating a mechanical seal zone in the conveyor that prevents muck and groundwater from spurting out from the conveyor. The benefits of this method include the ability: (1) to control the soil pressures at the tunnel face so that the surrounding ground does not deform, (2) to control the muck discharge volume by controlling the rotational speed of the twin-screw conveyor, and (3) to transport the muck from the discharge nozzle to the back of the machine. This method has been applied in two shield-tunneling projects, first for a utility conduit with the overburden of 22 m in cohesive soil, and then for a subway tunnel with the overburden of 8 m in sand and gravel. The success of projects proved the excellence of the method. For both projects, soil pressures at the tunnel face could be kept at a set value by the automatic control of the win-screw conveyor's rotational speed even when the advance speed of the shield tunneling machine was changed. As a result, deformation of the ground around the tunnels could be controlled. Further studies are under way for the measures against the wear of flights and casing of the twin-screw conveyor that is expected in the ground containing much gravel. The authors aim to make the twin-screw shield method into a standard mud pressure shield method by providing the twin-screw conveyor with greater durability through the studies. (A) Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Urban soft ground tunneling in China – experiences from Shanghai and other cities

This paper introduces the different kinds of urban soft ground tunnels in China built by shield method, immersed tube method and pipe jacking method. Although the history of urban soft ground tunneling is only around 40 years in China, enormous tunnels were built together with great progress especially since last decades. A lot of experiences and lessons gained from practices are not only valuable to Chinese tunnel engineers but also to tunneling industry in the world. In this paper we focus on the tunnel activities in Shanghai. Some significant technical features are highlighted. The most of the road tunnels in China were built by mining method. The modern tunneling methods like shield tunneling method or immersed tunneling method were only used in the cities where the ground is composed of soils. Up to now, the road tunnels built by the shield method are only found in Shanghai, and the immersed tube tunnels exist in three cities, named Shanghai, Guangzhou and Ningbo. Some project details and technical challenges are presented in this paper. As for MRT tunnels, there are about 210 km length of MRT tunnels in operation in mainland of China. MRT systems are being in operation only in four cities, while another 16 MRT lines are under construction or planning now. We focus on the planning, design and construction of MRT tunnels in Shanghai. Details of project and shield tunnelling machine are given in this paper. There are also other types of tunnels constructed or under construction by shield method or pipe jacking in China. With the development of our building infrastructure in the new century, the construction of different types of TBM projects and immersed tube tunnel projects are booming. We are looking forward to more innovative tunneling technologies to be employed in China. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Recent experience in automatic tail void grouting with soft ground tunnel boring machines

When tunnelling is carried out using a shield machine and a segmental lining, the shield machine is made slightly larger than the lining. This difference in size is necessary to allow the lining to be erected within the protection of the tailskin of the shield. A gap around the lining is also necessary to provide sufficient 'rattling' room, to allow the shield to be steered around curves without the lining and tailskin coming into contact. Grouting of the tail void is essential to ensure an even distribution of pressure around the lining, and to minimise settlement. It is demonstrated, based on field data from Singapore, that surface settlements can be controlled more effectively by utilising pipes laid along the tailskin, than by using conventional grouting through the tunnel lining. This method of grouting is now widely adopted on modern tunnelling machines. Modern tunneling machines are capable of rapid rates of advance; on the Cairo Metro, Phase 2, advance rates of up to 34.5 m per day were achieved. Field measurements in the Netherlands have shown that the rings are subject to significant uplift (flotation) forces while the grout is fluid. If the grout cannot hold the rings in place, then the rings will move during shoving, leading to steps, lips and ring damage. To achieve a good finished product it is therefore necessary to ensure that the grout is capable of holding the rings in place against the flotation forces exerted by the grout itself. In addition, for production reasons, the grout used should be slow setting and pumpable for a long duration after mixing. For cost reasons, the grout should be designed to make the maximum use of the cheapest locally available materials. Meeting all of these requirements is not easy. The grout mixes used on four recent tunnelling projects are outlined. The four projects are: the Cairo Metro, Phase2 (Egypt), the North East Line (Singapore), a sewer tunnel in Florida (USA) and the Groene Hart tunnel (Netherlands). For the Cairo Metro and the Groene Hart tunnel, mortar grouts, without cement, have been used for general tunnelling. In Florida a kaolin/cement grout was developed to deal with particular problems. In Singapore both accelerated cement grouts and cement/sand mortars were used. Based on the experience on the four projects, and research work done as part of the 'Eupalinos' project in France, mortar grouts are only effective if the mix is carefully designed to provide a mortar with the appropriate rheology to resist the flotation forces on the ring. For the Groene Hart tunnel a performance specification has been developed, together with specific testing requirements for the grout. Both the performance specifications and the testing requirements are outlined. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

The Quench Protection System for the LHC Test String 2

The large hadron collider (LHC) string program has focused over the years the efforts of many teams that have tested and validated their systems under operating conditions close to the final ones in the LHC machine tunnel and underground areas. During the various phases while commissioning or performing dedicated experiments, the quench protection system (QPS) has been tested and improved. A large variety of designs of the QPS equipment have been validated. The experience gained, especially concerning both the commissioning and the interaction with systems working within close interfaces (interlocks, powering, controls), is a valuable expertise to undertake the LHC challenge. In the LHC, the QPS will be the only system monitoring and protecting the superconducting elements: the integrity of all the superconducting magnets, bus bars and high-T/sub c/ superconducting current leads will depend on its reliable operation. A description of the system installed in String 2 will be given together with the principal similarities and differences with respect to the equipment planned for installation in the LHC. The key experimental results will be explained.

Investigation of induced radioactivity in the CERN Large Electron Positron collider for its decommissioning

The future installation of the Large Hadron Collider in the tunnel formerly housing the Large Electron Positron collider (LEP) required the dismantling of the latter after 11-year operation. As required by the French legislation, an extensive theoretical study was conducted before decommissioning to establish the possible activation paths both in the accelerator and in the four experiments (L3, ALEPH, OPAL and DELPHI) installed around the ring. The aim was to define which areas may contain activated material and which ones would be completely free of activation. The four major sources of activation in LEP, i.e., distributed and localized beam losses, synchrotron radiation and the super-conducting RF cavities, were investigated. Conversion coefficients from unit lost beam power to induced specific activity were established for a number of materials. A similar study was conducted for the four experiments, evaluating the four potential sources of induced radioactivity, namely e +e − annihilation events, two-photon events, e +e − Bhabha scattering events and beam-related radiation, i.e., synchrotron radiation and off-momentum beam particles. Decommissioning started early in 2001 and was completed by February 2002. Every single piece removed from the machine tunnel and experimental areas was double-checked for induced radioactivity, with complementary gamma-spectrometry measurements performed on samples of the various materials. The measurements have to a large extent confirmed the predictions. The overall intent of this paper is to provide data and computational guidelines for assessing induced radioactivity in high-energy electron accelerators, which could be of use in future decommissioning.

Mechanical splice of grid carbon fibre-reinforced polymer reinforcement and steel plate

A new shield-cuttable tunnel wall system has been developed. This system enables a shield tunnelling machine to break in or break out by directly cutting the launch or arrival part of the concrete wall of a vertical shaft with its cutter bits without performing prior ground improvement works and manual demolition. When this system is applied to a column-type diaphragm wall, H-shaped steel piles used as the reinforcement in the wall should be replaced by bit-cuttable mixed-in-place mortar piles reinforced with carbon fibre reinforced polymer (CFRP). In order to connect the grid CFRP reinforcement and the flange of H-shaped steel, a specially designed mechanical splice has been developed. Tension tests of the mechanical splices were carried out to investigate their mechanical behaviour. The mechanical splice was applied to the newest subway tunnel in Tokyo.

Groundwater and geotechnical aspects of deep excavations in Hong Kong

Consideration of groundwater is a key element in almost every construction project. The design of deep excavations for basements or underground railway station concourses below the water table require that the water pressures are taken into account. Whilst these can be considered to be hydrostatic in soil, the decreasing permeability of rock with depth and the fact that groundwater flow is invariably along discrete fractures means that the water pressure is unlikely to be hydrostatic at depth. Groundwater control for deep excavations can be achieved by a number of methods such as grouting, pumping or structural walls or a combination of these. For tunnelling projects grouting is extensively used, but the development of sophisticated tunnelling machines has led in many cases to the demise of compressed air as a means of groundwater control.

Technical note: Vibration measurement and modal analysis of boom type tunneller

The vibrations of an AM50 boom tunnelling machine have been measured in real time when cutting a man-made and a real coal bed. The vibration characteristics were similar in these working conditions, i.e. the man-made coal bed can be used as a realistic simulation of real cutting conditions. A modal model of the machine was then established and the intrinsic vibration characteristics were investigated by experimental modal analysis. Vibration response simulations under a set of measured load spectra and structural dynamics modification were also carried out using structural analysis software. The results not only facilitate the structural dynamics modification of the AM50 tunneller but also provide a foundation for optimising the design of new types of tunnelling machine.

Expert System for Applicability of Tunnel Boring Machines in Japan

¶This paper outlines the development of a new expert system for assessing the applicability of tunnel boring machine (TBM) tunneling in Japan. Although a great deal of research on TBMs has been published, and the applicability of TBMs has been discussed, considerable differences in opinion still exist between authors. In this paper, we review previous studies and outline the present situation with particular focus on disc-cutter TBMs. Based on the knowledge acquired, we present an expert system for the applicability of TBMs, for use in pre-feasibility studies. Originally, we planned to construct the expert system on the basis of unified knowledge or rules without contradictions. However, it was found after several attempts that it is very difficult to unify knowledge because opinions vary considerably and TBMs are under continuous development. As a result, the expert system was divided into three stages. In stage A, the fulfillment of fundamental requirements is checked. Stage B is a simple expert system consisting of a minimal set of suitable rules as judged by the authors. Stage C incorporates the opinions of various other experts and the over-simplified and omitted points in stage B. The system is applied to 18 tunnels in Japan, and while the results provided by the expert system can certainly be improved, the method for accumulating knowledge and rules makes the system simple and easy to use, with very large scope for improvement and expansion.

SEU tests performed on the digital communication system for LHC cryogenic instrumentation

The future LHC particle accelerator will use a large number of cryogenic sensors and actuators, most of which are located inside the machine tunnel and therefore in a radiation environment. These elements will communicate through a fieldbus. This paper reports the irradiation study carried out on WorldFIP fieldbus communication system. A digital communication system based on WorldFIP fieldbus protocol has been implemented and single event effects and total ionizing dose radiation tests have been performed on it.

Ground conditioning for earth pressure balance machine tunneling

Abstract The objective of this paper is to provide insight to the application of state-of-the-art ground modification technology for Earth Pressure Balance (EPB) soft ground tunneling. The paper reflects data from a wide array of sources including conference proceedings, trade journal articles, manufacturer publications, books and personal experience. The paper first introduces the concept of soft ground tunneling and then discusses the Earth Pressure Balance Tunnel Boring Machine method. The bulk of the paper is spent discussing ground-conditioning agents, particularly foam. Use of, quantities, theory behind them, environmental impact, lab testing, and effects of foams are described. The paper concludes with a brief case study of the Sheppard Subway Twin Tunnels in Toronto, Canada. Attached to the paper is a comprehensive literature search on EPB tunneling, particularly with regards to foam use.

Automatic seismic prediction ahead of the tunnel boring machine

As the world's population grows, with rapid economic expansion, there is an increasing demand for better transport links to improve the mobility of goods and people. As a result more and more tunnels are being built. For example, at the turn of the year 1998/99 more than 200 kilometres of tunnel with a diameter over 1 m were under construction in Germany. About three-quarters of this kilometrage is built for road-or rail-based transportation systems. For economic and safety reasons an increasing portion of tunnels are nowadays drilled by tunnel boring machines (TBM's also called tunnelling machines), particularly in soft ground i.e. less consolidated sediments. For example, 11 TBM's have been employed to bore the 50.5 kilometre Eurotunnel between France and England which mainly passes through Lower Cretaceous chalk and clay. TBMs remove soil and rock from the tunnel face as the cutting wheel rotates and the machine pushes forward, In hard rock traditional drill-and blast still dominates over TBM, but in soft ground most tunnels today are bored by tunnelling machines.

A development in rock cutting technology

This paper describes a novel method of rock cutting — oscillating disc cutting (ODC) — in which the forces acting on the cutting tools, and hence on the excavation machine supporting these tools, are extremely low. Four different techniques are incorporated in the cutting method to achieve this result. The importance of this novel method is that it allows very strong and/or abrasive rock to be machined easily and rapidly without suffering the high rates of tool wear and/or tool failure that are experienced by conventional cutting machines operating in these types of rock. Also the fact that the ODC method requires very low machine reaction forces means that lightweight, and therefore manoeuvrable, mining and tunnelling machines can be employed in the excavation process. In the initial sections of this paper we discuss the physics of the process of rock breakage caused by mechanical cutting tools and the wear and failure mechanisms of these tools. The arguments are given in order to introduce the thinking behind the ODC method.

DESIGN AND CONSTRUCTION OF THE JUBILEE LINE EXTENSION TUNNELS.

The Jubilee Line Extension took the London Underground network for the first time into the difficult waterlogged sands and gravels in the south east of the capital. However, there were very few problems with the now tried-and-tested technology of earth pressure balance tunnelling machines. This paper describes the general specification for the precast concrete, cast iron and sprayed tunnel linings and then highlights some of the many innovations which both designers and contractors introduced on each of the six main tunnelling contracts.

Three-dimensional numerical modelling for TBM tunnelling in consolidated clay

This paper presents a new field to analyze three-dimensional (3-D) coupled linear flow for Tunnel Boring Machine (TBM) tunnelling in saturated porous medium. This is important to control ground deformation and excess pore water pressure due to the process of shield tunnelling in three-dimension and time-dependent. A numerical model to simulate explicitly the behaviour of excess pore water pressure mobilization and its dissipation in time is presented. For the TBM tunnelling techniques, the positive pressure is applied to support the tunnel face and the grouting material is injected to decrease the deformation into the tail void gap behind the shield. Hence, this study is employed on 3-D model to investigate the impact of the most important parameters, which are slurry pressure and grouting pressure. The governing equations are derived in the light of the generalized Biot theory where displacement and excess pore pressure are the primary unknowns. The excavation stages during the advance of the machine in 3-D consolidation analysis is simulated. An isoparametric quadratic solid consolidation elastic soil model is used for this analysis. Results of this study indicate that a realistic modelling of soil behaviour, especially the distribution shape of the excess pore water pressure around the TBM tunnels during the construction stages and its dissipation during the consolidation time can be assessed. Thus, short-term as well as long-term effects of the TBM tunnelling are predicted. The practical importance of this analysis is the optimization of values and quantities of the slurry pressure and grouting pressure required for TBM technology. A design criterion based on this study can be suggested to tunnelling procedure in consolidated clay.