Abstract Pipe-roofing technology has been widely used to develop larger or more complicated underground spaces in urban cities in Japan. Rapid installation of roof pipes plays an important role in reducing underground construction cost and improving construction safety. Pipe-roofing has been attracting more attention to engineers and is one of the auxiliary construction and temporally support methods with less disturbing surrounding ground. However, ground conditions are very complicated and unknown and also a lot of underground utilities and facilities on the surface have been already constructed in the project sites. Cutting tool wear or failure due to hard rock layer or hard stones such as cobbles and boulders leads to tunneling work stoppage and in some cases, unforeseen obstacles make tunneling stop. This paper describes the recent pipe-roofing technology and the development of a micro-tunnel boring machine (MTBM), considering ground conditions. A newly developed MTBM shows many outstanding features in pipe-roofing under difficult ground conditions. 1. Introduction Our society depends very much on infrastructures such as roads, railroads, gas, electric power, water, sewer system, communication line, and so on. Sewage coverage has already reached 78% in Japan, and the market for constructing the sewage system is saturated especially in urban areas (Matsui et al., 2015). A new trend in this field is urban renewal, utilizing more underground spaces. Required underground spaces are becoming much larger or much more complicated shape. However, underground in urban areas is already congested with many utilities as well as many buildings on the surface. In order to keep ground stability during construction of underground spaces, pipe-roofing technology has been used at the project sites these days. Ground conditions and used construction system play an important role in reducing the construction cost and improving safety. Unfortunately fully understanding the ground conditions is very difficult or impossible in spite of pre-geological survey. Difficult ground conditions, machine troubles, or unexpected obstructions in the ground sometimes stop the tunneling operation. This paper describes the recent pipe-roofing technology and the development of a micro-tunnel boring machine (MTBM) used in pipe-roofing considering ground conditions. 2. Pipe-roofing using a micro-tunnel boring machine (MTBM) Fig. 1 shows an example of pipe-roofing works that before constructing an underpass beneath the existing freeway, a lot of pipes are installed to control surface settlement or ground failure during the underpass construction afterward. After pipe installation, the installed pipes are filled with concrete in order to reinforce the strength of the pipe roof structure. Now, it is recognized that pipe-roofing is one of auxiliary construction and temporally support methods without severe ground settlement or collapsing surrounding ground. Currently, underground spaces such as tunnels, subway stations, pedestrian underpasses etc., in urban areas are larger and more complicated shape and constructed near existing facilities and structures both in the underground and on the ground surface. Therefore, pipe-roofing has been attracting close attention of engineers as a supplementary construction method.

Abstract The paper covers the construction and use of large caverns for temporary and permanent purposes on the example of the 27km long Semmering Base Tunnel in Austria. Semmering Base Tunnel is a twin tube, single-track railway tunnel with numerous cross passages and an underground emergency station with ventilation located approximately at the center of the tunnel system. The construction started in 2014 and is ongoing until 2026. The emergency station, which is located at the toe of two 400 m deep shafts, requires the construction of large permanent caverns with dimensions in the range of 20 by 18 m. The available space in these caverns will also be used during construction for the placement of site installations underground in order to optimize the logistic procedures and avoid disruptions in supply and discharge via the shafts. Intermediate access points are provided by 120 to 200 m deep shafts, which also require the construction of temporary caverns at the shaft bottom for site installations, material storage and transport purposes. In one case even shaft head caverns are carried out as the shafts start underground at the end of a 1.2 km long access tunnel. For the construction in difficult geological conditions complex headings and special support measures using the SEM are applied. Advanced numerical 2D- and 3D-calculations were carried out to verify the adequacy of the designed solutions. The final configuration of the permanent and temporary caverns includes the installation of a drained, secondary lining or a complete backfill in case of the temporary structures. 1. Introduction The content of the paper covers the construction of temporary and permanent caverns at the example of an actual project currently carried out in Austria. The boundary conditions requesting the construction of the caverns such as safety regulations, logistic purposes or overall schedule requirements are addressed. The chosen solutions for the construction of the caverns as well as its configuration for the temporary and the final stage are presented. 2. Project overview Semmering Base Tunnel is located app. 80 km south of Vienna in Austria and is part of the Baltic-Adriatic Railway Corridor, which runs between the Baltic Sea from Gdansk in Poland to the Adriatic Coast near Bologna in Italy (see Figure 1).

Abstract This paper will share the controlled rock blasting experiences in two underground MRT projects in Singapore. Dedicated rock blasting design elements including decoupled charging, suitable spacing/burden, time delay and loading density to promote forward movement of the rock with balanced blasting efficiency and impact to surrounding amenities and buildings are presented. The empirical formulae which was used to predict the blasting induced ground vibration was calibrated against the instrumentation data. Parameters such as the site specific constant and the attenuation coefficients in typical Bukit Timah granite are validated and recommended. Various measures which were implemented to minimize the vibration at nearby structures and mitigate fly rocks within blasting site will be shared and discussed. This includes the traffic management efforts at the heavily plied vehicular and pedestrian movements above the blasting area. Effectiveness of line drilling of relief holes to prevent the blasting induced damage to king post and ERSS are discussed. The appropriate blasting limit in the aspect of peak particle velocity (PPV) for ERSS, king post, decking and surrounding utilities and buildings are suggested. Since no blasting codes and guidelines are currently available in Singapore, the shared data could serve as reference for future projects. 1. Introduction Thomson-East Coast Line (TEL) (Fig. 1), as 6 th MRT line in Singapore, is currently under construction. TEL is 43km long, fully underground and adds 31 underground stations to the existing rail network, including 7 interchange stations, which will link to the existing East-West Line, North-South Line, North-East Line, Circle Line and the Downtown Line. It will run through a combined north-south and east-west corridor, starting from Woodland North to Gardens by the Bay, followed by east coast stretch that will connect commuters in the eastern part of Singapore. The TEL will strengthen the connectivity and resilience of the current rail network by providing alternative travel route for many more commuters on the existing lines. The line will open in five stages from 2019 onwards. When fully open, it is expected to serve about 500,000 commuters daily in initial years, rising to one million commuters daily in long term. Slated to open in 2021, TEL stage 3 (from Mt Pleasant to Gardens by the Bay) expects high rock crop above station formation level in 2 stations located at Bukit Timah formation, i.e. T217 Napier Station and T221 Havelock Station. The estimated rock volumes are 40,000m 3 and 57,000m 3 , respectively. With consideration of the difficulty in breaking and removing the bedrock by any other feasible method, drilling & blasting using high explosives along with the latest electronics blasting system would be the most practical and feasible way to remove the bedrock in the shortest time frame.

Abstract This paper presents construction method and monitoring program for the stability for the existing Ekeberg tunnels in connection with the construction of the Follobanen tunnel - a new high-speed railway tunnel. When crossing the Ekeberg tunnels, the Follobanen tunnels are just few meters below. The construction of the Follobanen is approved with three conditions that (1) No negative effect to the stability of the Ekeberg tunnels, (2) The traffic flow in the Ekeberg tunnel must be maintained at all time, and (3) Any risk of instability in the existing tunnel must be detected beforehand to make necessary precaution actions. In order to deal with the challenges, SINTEF has developed a comprehensive procedure, combining continuous rock stress measurements and displacement measurements with 2-D and 3-D numerical modelling. Continued rock stress measurements and rock stress change monitoring are actively used together with numerical model to monitor the stability situation in Ekeberg tunnel. This is to make sure that any risk of instability in the existing tunnel can be detected beforehand to make necessary precaution actions. This paper is extended version of the one presented in November 2017, in Norwegian conference - Rock Blasting Conference, Oslo, Norway. 1. Introduction This paper is an extended version of a paper published in Rock Blasting Conference in Oslo, Norway - a national conference (Trinh & Holmøy, 2017). Bane NOR (Norwegian National Rail Administration) has decided to construct the Follobanen Project - with new railway tunnels close to the existing Ekeberg road tunnels in Oslo area in Norway, connecting Oslo and Ski. The Ekeberg tunnels have diameter around 11.5 m, and the Follobanen tunnels about 9.5 m diameter. The Follobanen Project comprises a 22km long twin-tube-tunnel to be excavated mainly with tunnel boring machines (TBM), but also by drill & blast and drill & split. The drill & blast and drill & split tunnel section is in the first part of the Follobanen tunnels, near Oslo Central Station, and where the Follobanen tunnels go under the Ekeberg tunnels. The main construction phase commenced in 2015, and it is scheduled for completion in the end of 2021.

Abstract The high-speed railway between Beijing and Zhangjiakou in China that is a very famous project all around the world is now under construction. Badaling station is at the middle of this railway line and is designed as an underground station. The transition zone between the running tunnel to Zhangjiakou direction and Badaling station has a large span cross section with a dimension of up to 30 meters. Meanwhile, this large cross section also goes through the fault fracture zone. As a result, the supporting scheme and stability of the surrounding rock as well as seismic safety are the main concern about this major project. In this paper a 3-D rock-tunnel dynamic interaction finite element modeling is carried out to analyze the construction stage and seismic performance of the large span tunnel cross section. Numerical results have demonstrated the rationality of support system and revealed the seismic performance of the large span cross section. 1. Introduction The new Badaling Tunnel is located between Changping Nankou Town and Badaling Town in Yanqing County. The world's deepest and largest high-speed train station (Badaling underground station) which will be an important part of the 12km long tunnel between Beijing and Zhangjiakou will be 102m deep with a floor area of about 36000 m 2 . Starting section of the transition section of the station in Beijing directions is DK67+653 and that in Zhangjiakou direction is DK68+285. This tunnel station comprises of three different sized cross sections namely: small distance spaced section, large-span and triple arch section. The transition zone towards Zhangjiakou direction spans through a fault fracture zone which makes it vulnerable to seismic activity and needs to be investigated. Figure 1 shows the plan of the station. Based on the prevailing geological conditions, seismic effects and station structure details form the comprehensive geological survey report, it is necessary to analyze the overall seismic performance of the Badaling underground station. The transition tunnel is of a maximum net width and height about 30.83m and 17.57m, respectively, with a height - span ratio of 0.57. The Zhangjiakou direction transition section passes through a fault fracture zone and is the focus of this investigation. The plan of this transition section is shown in figure 2. The surrounding rock is graded 3–5 and the Norwegian method is adopted for the excavation. Initial support system against the rock includes shotcrete, prestressed cables and prestressed anchors.

Abstract This project is named ‘Marmaray’ which is a rail transport project in Istanbul, Turkey. The name ‘Marmaray’ comes from combining the name of the Sea of Marmara, which lies just south of the project site, with ‘-ray’, the Turkish word for rails. It is an undersea railway tunnel passing under the Bosphorus Strait. Existing suburban railways of approximately 76 kilometers are to be modernized. Tunnels and stations in 13.6km length of this project have been constructed by immersed-, shield- and mountain- tunneling methods together with a cut-and-cover technique. Construction had started in 2004 and the tunnels and stations have become in service since October 29, 2013. In this paper, the construction of an underground railway station (Sirkeci Station) in an urban area consisting of neighboring large-scale tunnels and shafts by means of NATM is reported. Sirkeci Station has two ventilation shafts (about 510m 2 in cross-sectional area) at both ends (west and east side) of the station. The shafts are connected with two platform tunnels (about 190m2 in cross-sectional area). Each shaft is neighbored to the platform tunnels at a minimum interval of about 1m. First of all, the west shaft was excavated and supported with steel rings, columns and additional shotcrete in order to reduce the influence of four openings at the shaft and neighboring tunnels excavation. Prior to the east shaft excavation, the tunnels were excavated and supported by reinforced-concrete primary lining. Subsequently, the shaft adjacent to the tunnels was excavated. Lastly, the shaft and platform tunnels were connected with additional supports such as additional shotcrete, forepiling, etc. Before the influencing events, three-dimensional excavation analyses were carried out in order to decide the specification of the additional supports. Through the analyses, the support behaviors due to the events were predicted. During the excavation, the monitoring results were compared with the prediction. To ensure the stability of structures and ground around the shafts and tunnels, observational construction management is indispensable. The measured results that were within the allowable limits successfully proved the stability of the complex structures of the underground station.

SYNOPSYS: In recent years, the most densely populated cities in the world have accelerated effort in developing underground space as a mode of transportation for eco-friendly and sustainable cities. However, it appears to become more difficult to use underground space in metropolitan cities due to existing underground structures. Consequently, it leads to development of underground space beneath existing underground structures and the underground structures become multi-layered vertically. Considering the fact, this case study aims to introduce the design and construction methodology of the largest tunnel station in Seoul, which has been constructed 15cm under the existing subway line 3 and the superannuated underground shopping complex within highly-congested area. To overcome the obstacles incurred by the site condition, for instance, neighboring construction, civil petition and severe traffic jam during the construction, the combined method of the TRcM(Tubular Roof construction Method) and the CAM(Cellular Arch Method) has been created and applied. Although this construction project was considered as the most difficult project ever in the history of the Korea's subway construction, the subway station has been constructed successfully without any damages on the adjacent structures and has launched from July 2009. 1. INTRODUCTION Seoul, the most populous city in Korea, has the population density of 16,582 people per square kilometer in 2009. Until the 1990s, Seoul had experienced rapid economic growth as well as population concentration, and decided to promote the development of underground space. The utilization had been focused on the shallow depth underground space by using the cut and cover method which was relatively easier and less intricate to apply. As a result, the most of shallow-depth underground space in urban areas has already been utilized for transportation, electric power, communication, water supply and sewer networks. Nowadays, these existing underground structures are considered as one of the major obstacles in development of underground space. Consequently, the cases of tunneling work under existing underground structures have been increasing rapidly. 2. PROJECT OVERVIEW The stage 1 of the new Subway line 9 has launched in July 2009 to ease the traffic flow between the west and the east part of the Seoul and to promote the use of underground space as a mode of transportation for the development of eco-friendly and sustainable cities by reducing air pollution and economic cost of traffic congestion. The stage 2 and stage 3 of subway line 9 will be completed in 2013 and in 2015, respectively. The stage 1 of subway line 9 starts from Gimpo Intl. Airport and ends in the Gangnam Area, the most urbanized area in the Seoul. The total length of the subway line 9 is 25.5 km and it has 25 stations. The 913 project of the stage 1 is composed of two subway stations (922 and 923 subway station) and the 1.78km of subway lines as shown in figure 1. The 923 subway station of the 913 project, which is named the Banpo(Express Bus Terminal) station, is located in the center of the life culture and transportation.

ABSTRACT: Behaviour of underground structures subjected to dynamic loading is different from the surface structures. Underground openings in rock mass generally do not suffer as much damage as the surface structures during major earthquakes (M < 7), particularly if they are located at a depth of more than 20m and there is no fault zone or weak zone in the neighborhood. Considering the ground acceleration of dynamic loading, a pseudo-static approach for estimating the dynamic support pressure in tunnels has been suggested in the paper. Rock mass quality in seismic areas (Seismic) proposed by Barton (1984) has also been correlated with the coefficient of peak acceleration. Higher the ground acceleration or blast loading more shall be the overburden for an underground opening to be safe. 1. INTRODUCTION Underground structures are an integral part of infra structural development programme. These are used for a wide range of applications, including subways and railways, material storage and sewage and water transport. Underground facilities built in areas subject to earthquake activity must withstand both seismic and static loading. Underground structures have features that make their seismic behaviour distinct from most surface structures, notably their complete enclosures in soil or rock and their significant length (i.e. tunnels) (Hashish et al, 2001). In general, underground structures have a lower rate of damage than surface structures. Experience suggests that there is no cause for worry for tunnel stability because of earthquakes in rock masses below 20m from ground surface, except in the active fault zones or weak zones. Nevertheless, some underground structures have experienced significant damage in large earthquakes (M>7), including 1995 Kobe, 1999 Chi-Chi, 2004 Cheese, 2005 Kashmir and 2008 Henchman earthquakes (Hashish et al, 2001 and Aidan et al, 2010). Hence to make the underground infrastructures safe from seismic and other dynamic forces like heavy blast loading, it is necessary to carryout a dynamic analysis of an underground structure. This is all the more essential when it comes to accommodate human activities. For studying the effect of dynamic loading on underground structures, a pseudo-static approach is presented in the paper. Before this general observations on the seismic performance of underground structures as reported by Hashish et al. (2001) are given. 2. PERFORMANCE OF UNDERGROUND FACILITIES Following are the general observations pertaining to dynamic performance of underground structures (Hashish et al, 2001). Underground structures suffer appreciably less damage than surface structures. Reported damage decreases with increasing overburden depth. Deep tunnels seem to be safer and less vulnerable to earthquake shaking than are shallow tunnels. Underground facilities constructed in soils can be expected to suffer more damage compared to openings constructed in competent rock. Lined and grouted tunnels are safer than unlined tunnels in rock. Shaking damage can be reduced by stabilizing the ground around the tunnel and by improving the bond strength between the lining and the surrounding ground through grouting. Improving the tunnel lining by placing thicker and stiffer sections without stabilizing surrounding poor ground may result in excess seismic forces in the lining.

ABSTRACT: In most of the metropolitan cities, the need of metro railways is of vital importance which is increasing day by day. Hence there is need for excavation of tunnels for track laying as well as construction of underground railway stations, wherein precaution regarding the various aspects such as ventilation, air conditioning and fire safety is inevitable. The purpose of this paper is to study the aspects like ventilation, air conditioning and fire safety of tunnels for roads and metro railways in particular and to formulate provisional checklist for preliminary design purpose. The methodology adopted for the work includes analysis of various existing design criteria for the same. The checklist is divided into different major areas such as ventilation, air-conditioning and fire safety. An attempt is also made to formulate the design for discharge volume of ventilation in which tunnels under construction are considered. The work presented is one of the important aspects for the tunnel designer and contractor from execution and safety point of view. The work helps in planning the preliminary design parameters related to above aspects with the help of checklist that can be used as reference for the tunnel projects in general. 1. INTRODUCTION To gain access to the central area of the city, the sub-way remains the most viable alternative. So, invariably tunnels have to be constructed to meet the demand of increasing traffic load. Operating tunnels and subway systems has demonstrated that safety has to be planned and enforced as a high-priority policy in order to ensure that emergency situations can be managed properly and with minimal damage or loss. An appropriate emergency ventilation system is a main component of the emergency plan, recognizing that prevention is much better than dealing with the consequences of fire accidents. [1] Vehicle fires in road and rail tunnels are recognized to represent an immediate and extreme danger to the patrons of those systems. Unlike workers in the mining and civil construction industries, the general public are neither trained nor equipped to fight fires or to evacuate under deteriorating smoke conditions. The study of the UNECE (United Nations Economic Commission for Europe) entitled "Risk Analysis of Accidents in Tunnels" analyzed 176 cases of accidents involving trains in tunnels or underground railways. Out of these, 49% cases were involving fire. The result gives emphasis to design the aspects like ventilation and fire safety for effective mitigation of fire hazards. [3] Fire safety in rail and road tunnels is challenging because of the specific features of the tunnel environment such as restricted egress path, lack of approach at the place of fire origin, accumulation of smoke inside the tunnel, etc. Also, the underground stations of the Metro Corridor are to be built in the confined underground space. A large number of passengers occupy concourse and the platform, especially during the peak hours. The platforms and concourse have a limited access from outside and do not have natural ventilation. It is, therefore, essential to provide artificial ventilation in the station areas.

ABSTRACT The demand for efficient new infrastructure systems is increasing and automatically leads to the underground as living space above ground is becoming more and more scarce. This also applies to the mechanical construction of tunnels, which is almost completely carried out in underground thanks to the tailor made tunnelling technology made by Herrenknecht. Mechanized tunnel excavation has entered new dimensions in terms of size, length, geological complexity and depth of underground constructions. It sets the standards regarding safety, profitability and environmental protection – in Traffic Tunnelling projects as well as in the trenchless construction of Utility Tunnels, such as sewer, water, cable tunnels and oil and gas pipelines. Different machine types and working principles have been developed to master the geological and hydrological requirements of tunnelling projects worldwide. This paper gives an overview on state-of-the-art hard rock tunnelling equipment and project possibilities but will also highlight the innovative and current design approaches to overcome the difficult specific project conditions of hard rock projects of today. Reference projects and experiences world wide show the feasibility of tunnel visions and the infrastructure importance for the respective area. 1. Introduction The tunnel projects of today are increasingly constructed in more complex conditions. In soft ground the current challenges are projects in heterogeneous soil conditions, tunnel construction in urban areas with low overburden and conditions with very high ground water pressures above 10 bar. In hard rock the project demands are characterized by long tunnel drives, high overburden and abrasive rock masses such as the conditions faced with the project for the rail crossing of the Alps in Switzerland, the Gotthard Base Tunnel. These high standards on tunnel projects also demand safe and economical tunnelling technology which is provided by mechanized tunnelling. In hard rock tunnelling there are, depending on the rock quality, two groups of hard rock tunnel boring machines. The Gripper TBMs are used in solid rock conditions and the Shielded TBMs (Single or Double Shielded TBMs) are used in stable and unstable rock conditions. The success of each tunnelling system depends on the excavation process, the rock support concept and the mucking system and logistical system of the applied technique. The following chapters give an overview of these hard rock tunnelling systems and will focus on representative project examples. 2. Hard Rock tunnelling systems 2.1. Gripper TBM This machine type is typically used in stable and massive rock conditions with low water ingress. The cutterhead of the Gripper TBMs is a flat face design. It is equipped with disc cutters to suit the rock conditions. Buckets which are arranged at the circumference of the cutterhead are responsible for the removal of excavated 754 material. They are supported by additional backscrapers on the rear side of the cutterhead. In addition to drilling technology, efficient and economical material transport is also a key requirement for successful TBM tunnelling.

Abstract A railway tunnel was designed parallel to an existing 275m long 147 years old tunnel between Jamalpur and Ratanpur section in the state of Bihar in India. The planned horse-shoe shaped tunnel is 7.30m high and wide. The tunnel passes through the jointed quartzites and slates of Precambrian age. Slates are present for 126 m length, whereas quartzites are present for 150 m length of proposed tunnel. Maximum rock cover above the tunnel is about 60m at RD 3495m. The wider section having nitch for trolley refuse is also designed in the tunnel at two locations, one in Quartzite and other in Slates formations. The empirical approach based on the Q-system was used to estimate the support pressures and to design the tunnel supports. Numerical analysis using FLAC3D code has also been carried out. The safe distance of 17m is worked out between the walls of two tunnels. The 20m length of tunnel in portal zone from both ends has been designed with steel rib supports and the rest of the tunnel designed with rock bolt and shotcrete supports. 1. Introduction The existing Sahibganj Loop on the Kiul- Bhagalpur section of the East Central Railway crosses the Jamalpur hills through a tunnel between Jamalpur and Ratanpur Stations. The entire section has double broad gauge (BG) track but through the existing tunnel only single BG track is available. In order to have double track for operating up and down traffic on separate lines through the Jamalpur hills, another tunnel in the close proximity to existing tunnel is envisaged. The existing tunnel of the Ratanpur - Jamalpur section is 275m long aligned in East- West direction. The tunnel was constructed in 1861 and working satisfactorily since then [1]. No major problem and repair/maintenance works have been reported during the use of the tunnel. The D-shaped tunnel has arched roof of radius 3.963m. The height of the tunnel above the rail level is 6.502m whereas the overall height is 7.225m. The tunnel is partially lined with brick masonry. The tunnel passed through two different categories of rocks, viz. quartzites and slates. The quartzites are hard and strong in the tunnel stretches towards the Jamalpur portal whereas the stretches of tunnel towards the Ratanpur portal consist of slates which are comparatively weak and also charged with water. The 113.39m portion of existing tunnel in slates from Ratanpur end, therefore, has been fully lined by brick masonry to protect the tunnel roof and sidewalls. The tunnel in the quartzites, on the other hand, is partly lined at the western side from Jamalpur portal to 32.30m inside the tunnel and the balance 129.61m is unlined. Apart from the brick masonry lining no other primary support was apparently used in the existing tunnel. Slope above portals have been naturally stabilized and the brick masonry lining has been used in the portal area.

ABSTRACT In order to mitigate the damage of tunnels caused by fault rupturing, a new lining system is proposed. This lining system is comprised of double-layers; the inner layer is a smoothing layer to disperse localized deformations and the outer layer is an absorption layer to accommodate large fault dislocations. Furthermore, a multi-shell mortar is developed as suitable materials for the outer absorption layer characterized with high rigidity before yielding and high compressibility after yielding. An attempt is also made to evaluate the damage of a typical railway tunnel subjected to fault rupturing. The computed results demonstrate that the proposed method is effective for fault displacements of less than a meter. 1. Introduction Japan is located in the middle of the most seismically active zones on the earth with more than 2,000 active faults being formed in a small archipelago of about 38km2 [1]. As some mountain tunnels are unavoidably sited across these active faults, there are potential risks of severe damages by fault rupturing at the tunnelfault intersections. Therefore, it is necessary to take appropriate countermeasures for mitigation of these fault rupture hazards on mountain tunnels. Among various ideas for mitigation of fault rupture hazards [2], Figure 1 shows one of the most promising and effective countermeasures for mountain tunnels [3]. The double-layer lining system is installed for some distances from the tunnel-fault intersection to prevent localized breakage or severe dislocations while allowing widely distributed continuous bending deformations. The outer layer is a special material with high stiffness before yielding to support the tunnel until the outbreak of relevant earthquake and also with high compressibility after yielding to absorb and accommodate large fault dislocations. On the other hand, the inner layer is reinforced concrete with high flexural strength to prevent localized breakage and with high bending stiffness to smooth and disperse the fault dislocations. Furthermore, expansion joints and lubrication layer may be installed to reduce axial forces mobilized along the tunnel when the length of the tunnel is changed by faulting. In this study, a special material of multi-shell mortar is proposed for the outer layer [4]. Furthermore, an attempt is made to calculate the deformations of the tunnel equipped with this double-layer lining system. 2. Multi-shell Mortar A multi-shell mortar is a mixture of ordinary mortar and a large number of voids capsulated by thin rigid husks. This material exhibits high rigidity under low loads until its voids start to fail. For the loads higher than this yield load, however, it tends to compress significantly with little load increments. 2.1. Uniaxial Compression Test on Multi-shell Mortar Since the multi-shell mortar is designed to be used for the outer layer in the double-layer tunnel lining system for mountain tunnels, it is sandwiched between the inner layer of reinforced concrete and the surrounding rock masses. In the process of fault rupturing, the outer layer is subject to large compression by reducing its thickness to accommodate large fault dislocations.

ABSTRACT The 57 km long Gotthard Base Tunnel is the core of the new railway link through the Alps. It consists of two parallel single-track tubes, shafts, galleries and two multifunction stations in the Sedrun and Faido section with emergency stations and tunnel crossovers. This paper deals with the design challenges of the multifunction station Faido which consists of an extremely complicated combination of main tunnels, galleries and caverns in a very difficult geology with several fault zones. Some caverns and the crossovers cut the main tunnels in an acute angle. At some intersection points critical areas with minimal pillar widths are created. The article describes several evaluations which were carried out to ensure the stability of the rock pillars. 1. Introduction Today's steadily growing traffic volumes call for new, high-capacity transportation facilities. Switzerland's New Alpine Transversal (NEAT) will provide a high-speed rail link for passenger and freight trains passing through the Alps between northern and southern Europe. It will enable much of the traffic to be shifted from road to rail. One of two NEAT lines is the Gotthard axis including the Gotthard Base Tunnel (GBT) in the east. The Gotthard Base Tunnel's length of 57 km makes it the world's longest railway tunnel. As a flat railway with gradients no greater than 10‰, the line will be used by passenger trains traveling at top speeds of 200 to 250 km/h and by heavy freight trains. The initial preparatory work for the GBT started in 1996; the tunnel is scheduled to be opened in the year 2015. The GBT consists of two parallel single-track tunnel tubes which are connected by cross passages every 312 m. Of the total 153.5 km of tunnels, shafts and galleries (Fig. 1), 113 km or 74 % was completed by July 2008. To shorten the construction time and also for ventilation purposes, the GBT is divided into five construction sections (Erstfeld, Amsteg, Sedrun, Faido and Bodio). The tunnel is being driven simultaneously from both portals (Erstfeld in the north, Bodio in the south) and from three intermediate points of attack (access tunnels at Amsteg and Faido and a shaft at Sedrun). The Sedrun und Faido sections each include a multifunction station (MFS). These stations contain four trumpet-shaped tunnel branch-off structures including two tunnel crossovers These stations consist of train switches to the other tube as well as emergency train stops that are linked with a side gallery. In an emergency case during the operating phase, the passengers can be evacuated through these side galleries. 2. The Multifunction Station Faido,Layout and Geology 2.1. Layout The Multifunction Station (MFS) Faido lies at the end of an access tunnel within the construction lot Faido.

ABSTRACT: Within the city or Stuttgart (Germany) a number or railway and highway tunnels have been constructed in horizontal layered mudstones. limestones and lime-sandstones of the Lower Jurassic (Black Jurassic/Lias a). One example is the Osterfeld tunnel atthe eastern highway ring in Stuttgart-Vaihingen, which undercrosses residential buildings and a railway line with low overburden. The stability of the construction stages and small deformations have been achieved. By an advancing vault excavation w ith a curved tempo- rary invert supported by shotcrete. For the same reasons the round lengths were kept short and an advancing pipe umbrella was installed in the area of the railway crossing where the overburden amounted to on I) 5–6 rn. As part of the design three-dimensional finite elementstability analyses have been carried out. The results of these analyses were a valuable tool for the design and compared well with theresults of monitoring. 1. INTRODUCTION The Osterfeld tunnel undercrosses residential areas as well as thetracks of the Gaubahn and the S-Bahn. Especially at the railwaycrossing the overburden is low. During the heading of the tunnelunderneath the railway lines the railway traffic could not be interrupted.In this area, therefore, special measures for the support ofthe tunnel were required. Special attention was required. becausethe road tunnel is located in mudstone layers of the Lias a. which are Subjectedto high horizontal stresses. 2. STRUCTURE The Osterfeld tunnel. Which has been excavated by means of theNATM is approx. 400 m long and pan of the cast an ring around Vaihingen. a suburb of the city of Stuttgart. 3. GROUND AND GROUND-WATER CONDITIONS During the design phase for the new by-pass road, an extensive program for the exploration of the subsoil and ground-water conditions was carried out. In this program besides the sinking of core drillings, the investigation of soil, roek and water samples, water level measurements. combined extensometer and inclinometermeasurements as well as in-situ stress measurements were carriedout. 4. FUNDAMENTALS OF THE DESIGN Because of the small overburden. the high horizontal stresses and the low shear strength of the bedding planes in the Lias a. in which the tunnel is located. special problems concerning the stability of the tunnel arise. 5. STABILITY ANALYSIS FOR THE STAGES OF CONSTRUCTION The stability analyses for the stages of construction were carried out by the finite clement method for vertical slabs (sec Wittke, 2000). In the Lias a additional to the stresses due to dead weight horizontal stresses ~crll varying from 0.5 to 1.5 MPa - depending on the location of the considered computation section - were simulated, Additional analyses without consideration of increased horizontal stresses were also carried out. In the two first steps of the analysis the in-situ stare of stress due to dead weight and also the additional horizontal stresses in the Lias a are calculated.

ABSTRACT: To case traffic congestion Seoul Metropolitan Government formulated the 2nd Phase of Seoul Subway Construction Project in 1989. The project called for the construction of 160km of subway which included addition of 4 more subway lines and extension of 3 existing subway lines in addition to the existing 118km of subway. As a final stage of the project subway line 6 is under construction. The line 6 is 36.1 km-Iong route. The line was opened by the end of 2000. With the completion of the line Seoul \~II.1 have 278km of subway network and the transport shared by subway will be increased from 25% in 1992 to 50% in 2002. In ad dition to Seoul subway project, the cases of underground space utilization such as energy storage, food storage, high-speed railway and underground car parking area arc also described in this paper. In Korea many large-scale structures have been constructed since1970s. This paper is a brief description of the current large- scale underground projects in Korea. some of which have been completed already. 1. INTRODUCTION I~ Scout, Subway Construction Project except for the depot main line arc underground and major construction methods were cutand cover and tunnelling, As a tunnelling method New Austrian Tunnelling Method (NATM) was adapted. the line was opened In the end of 2000. With the completion of the line Seoul has 2~8~111 of subway network and the transport shared by subway w,\Ilncrease from 25% in 1992 to 50% in 2002. therefore, was weathered rocks or weathered soils. Substantiallengths of tunnels are being constructed and designed running through the alluvial deposits as well. In Korea many large-scale Structures have been constructed since 1970s, Technical experiencesaccumulated in the areas of underground rock engineering have. made it possible 10 undertake large-scale projects with do- ~estlc technology, This is a brief representation of large tunnellingand underground storage projects in Korea. some of whicharc still in progress. 2. CURRENT SITUATION OF TUNNELING AND UNDERGROUND STORAGE PROJECTS 2.1 Underground oil find gas storage projects According 10 Korea's stockpiling program, the construction of oil storage facilities began in the late 1970s and the first large ~nderground caverns for storing crude oil were built in 1985. hree additional facilities for underground LPG storage con- :~1Ibuted to ~ccomplishing the goal of st?ckpiling of crude oil for e 60-day s consumption III 1988 1he rapid Increase m oi! cOI~s.lIl11ption, however, required more construction of storage facilities, in order to maintain the stockpiling amount correspo. nding to the 60-day's consumption. Fable I lists the storage cavern in operation or under con str~ c~ion in Korea. K-I. U-2 and L-I have the extensions of pre eXlstlllg facilities. AS shown in Table I. the first underground ~torage facility, which can store 231.000kl of refined oil. was 1I11~ In a granitic rock mass in the vicinity of caul. The crosssectIonal dimension is 15m × 20m with the total length of 1,262m. The construction was started in 1975 and was completed III 1982.

ABSTRACT: The present paper points out that the earth-nail is the bolt in soil horizons and the earth-nail-wall can be considered as bolt-shotcrete lining in soil. The ground xcavation is, in fact, such a process of redistributions of stress and seepage filed that is closely followed by the supporting as the excavation advances downwards. Accordingly, there exists a large error if the limit equilibrium method is used in designing. This paper describes the guiding principle of the CSC working method proposed by the author and the mechanical analysis of the earth-nail-wall. It is concluded that the joint support of steel bar-net, shotcrete and earth-bolt, as a complete reinforcing structure is quite effective. It is shown furthermore in the paper that the large deformation theory for the excavation works in soft rocks or in soil ground surface is a valid tool to tackle the problem of engineering art concerned. 1. GENERALIZATION The bolt supporting for reinforcing the ground excavation works originated first in 1960, of which the essential idea is to reinforce the rockmass or soilmass so as to increase their self-supporting ability. Man who simply believes the law of the mechanical behavior of the rockmass or soilmass started excavating and constructing slope works without supports occasionally since ancient times. Not until the 20th century did the bolt supporting come into wide and successful uses and meantime a mass of researchers and engineers conducted thorough studies of the reinforcing mechanism of bolts, reaching the following unanimous knowledge: The compound stucture of rockmass-bolt or soilmass-bolt increases the strength of the mass; The interaction between rockmass (soil mass) and bolts improves the force-bearing state of the mass; The bolting support structure makes use of the time-space effect of rockmass (soil mass) scientifically, thus limiting and controlling the rock or soil media deformation within an allowable range;.. It is more rational to use the nonlinear large deformation theory for studying the mechanical behavior of soft rockmass or soilmass; Unreasonable construction technology will result in the stability failure of an engineering project. It was reported that Frenchman once introduced the earth-bolt to reinforce the cut slope of railways in 1972 and gave it the name of earth-nail. Since then the earth-bolt has been called the earth-nail by some scholars. In fact, both earth-bolt and earth nail are a supporting member under similar definition that belongs to the same attribute, in other words, the definition of the earth-nail is ambiguous, having no clear mark to show the character of itself. Traditionally, by the earth-nail, man means the steel bar that is driven or pressed into the soil mass, there is no other material between the nail and the mass. Some researchers suggest the distinctions between earth bolt and earth-nail as follows: The earth-bolt is usually prestressed but the earth-nail is not; The earth-bolt is subject to forces only within its anchored length but the earth-nail bears forces within the whole length.

ABSTRACT: A tunnel design using numerical analysis relies on the selection of realistic parameters for success. The use of back analysis in tunnel design is important for the determination of parameters in numerical modeling, and for the understanding it brings to numerical modeling. However the process suffers from non-uniqueness, many different combinations of parameters can give an acceptable fit to observations. The technique of predictive analysis offers a solution to the problem of non-uniqueness. In this technique, the observations are matched to the parameter set which maximises or minimises a particular prediction outcome - an example being the maximum settlement above a tunnel. The advantages of using the technique of predictive analysis is demonstrated. Predictive analysis is useful in that the judgement of the predicted outcome is related to the match of the observation points and less emphasis is required on the judgement of parameter values in the rockmass. I. INTRODUCTION The use of numerical modeling is now widespread in geotechnical engineering. The designer can examine new construction methods in ground for which no database of previous construction exists. Practically, the numerical model is limited by lack of knowledge or "true" ground and support properties. There are many ground models available to the modeler, starting with simple elasticity and ranging up to including plasticity or time dependent behavior. The results of the numerical method are very sensitive to input parameters and to the choice of ground model. A sensitivity analysis may be carried out on key input parameters to estimate the likely range of outcomes. Even so, the most important issue is the choice of values for the model input parameters. Nearly all models used in geotechnical analysis require a value of Young's modulus. There are numerous methods for estimating a value. These include: direct tests on pieces of intact core, correlations with RQD, RMR and Q values, use of seismic velocities, and the GSI method of Hoek et al (1995). Engineers usually make a number of estimates for Young's modulus, which are likely to vary from lowest to highest by as much as a factor of 20. The Judgement of experienced professionals in this process for the choice of applicable parameters is a very valuable ingredient, This paper demonstrates a technique for numerical modelling that removes the traditional focus on the model parameters and places it on physical observations and model predictions. Models an their parameters are simply a way to characterise a physical process using mathematics. Whilst it is desirable that the parameters have a physical interpretation this is not essential. Stresses, ground models and input parameters are philosophical concepts - deformation is the physical reality (Burland, 1967). Using the technique outlined in this paper, the designer's judgements are based on observations and model predictions of pilot construction or other large scale tests (eg displacements) rather than preconceived notions suitable values of input parameters. 2. THE VULTURE STREET Y-JUNCTION The South East Transit Project is a $520 million project in Brisbane.

ABSTRACT: The Rossio railway tunnel was built in 1890, about 2600m long, crossing several formations involving limestones, basalts and also sandy and clayey formations. Recently a new tunnel from the Lisbon Metro was executed above and normal to the railway tunnel with a short distance between the lower part of the metro tunnel and the railway one. A reinforcement support system was designed in the Rossio tunnel in order to assure its stability. The reinforced system comprised the use of grouted bolts and shotcrete. A monitoring system was implemented in order to observe the structural effects induced by the construction of the Metro tunnel in the Rossio tunnel. In this communication the construction procedure is analysed as well as the geomechanical tests performed that involved in situ and laboratory tests and the monitoring tests. For the interpretation of the obtained information a complex 3D model was built using the software FLAC3D, permitting the simulation of the sequential excavation scheme used and non-linear behaviour of the rock and soil formations, and the different support systems used. A simplified seismic was also performed in order to evaluate the influence of an earthquake in both underground structures. Some significant results and final considerations are presented. 1. INTRODUCTlON The Rossio tunnel was built in 1890, with a masonry vault composed of bricks, with a thickness of 80cm, and the walls in stone or brick masonry. The tunnel has a length of about 2600m. It is located in Lisbon, inside a hill between the valleys of Avenida da Liberdade and Sao Bento. In the initial stretch, from the Rossio station until km 0.780, it crosses, at a shallow depth, clayey-sandy formations, some of them with significant permeability. In the intermediate stretch, limestones and marls are found, with important flow of water through the discontinuities of the rock mass. In the final stretch, the geological formations comprise basalts, marls and highly fractured limestones (Choffat, 1889; Sousa, 1998). The internal tunnel cross-section was designed with a maximum width of 8m, formed by a circular vault of 4m radius, and maximum height of about 6.5m (Figure 1). The tunnel was constructed according the well-known Belgian method, that considered the following phases (Cabral, 1987): i) excavation of a pilot gallery in the centre of the upper part of the section; ii) lateral enlargements of the upper part; iii) construction of the brick masonry vault, and subsequent filling of the void between the ground and the vault with stones; iv) excavation of the lower central section and subsequent lateral enlargements; and v) execution of the walls in stone or bricks in case of lower. The use of this construction methodology was one of the main reasons for the settlements and ground movements, as well as the occurrence of voids between the masonry and the ground. Recently, the Rotunda-Rate line of the Lisbon Metro was constructed, starting at the Rotunda II station, followed by the Braancamp and the Herculano runnels and ending at the Rato underground station.

ABSTRACT: In this paper, the practice of NATM (New Austrian Tunnelling Method) in Dongfeng tunnel in Suozhou-Huanghuagang railway is introduced in detail, including such aspects as reducing interference to surrounding rock as possible, controlling deformation and loosening of surrounding rock, adjusting support pattern and parameters on time etc. I. INTRODUCTION NATM (New Austrian Tunnelling Method) was firstly put forward by professor L. V. Rabcewicz, an Austrian scholar, in 1950s. It was awarded patent right and formally named in 1963 after theoretical studies and project practice in several countries. Such as Austria, Swede and Italy etc. Then, NATM was quickly developed in underground engineering in Western Europe, Northern Europe, United States and Japan. The main points of NATM are: applying the theory of rock and soil mechanics, maintaining and utilizing self support capability of surrounding rock as a basic point. using bolt and shotcrete as main support means, controlling surrounding rock deformation and loosening. making surrounding rock as a part of tunnel support system and by means of monitoring to guide the design and construction of tunnels and underground engineering. Seven basic points were summed up in "The Guideline of NATM for Railway Tunnel" issued by China Railway Ministry. 2. PROJECT DESCRIPTION Dongfeng tunnel is a double-track railway tunnel. Its inlet and outlet mileages are DK45+683 and DK48+973. The total length of the tunnel is 3290m. It is one of the 4 longest runnels in Suozhou-Huanghuagang railway. The geological structure of the tunnel is very complicated. The tunnel was excavated in the Quaternary Period diluvial formation and marl. The maximum depth of the tunnel is 465m. The construction task with the mileage of DK45+683-DK47+660 (1977m) at the inlet section was taken by the 14 th China Railway Construction Bureau. In this construction section there are 4 different kinds of surrounding rocks: scale 11, scale III, scale IV and scale V, according to China Railway Tunnel Surrounding Rock Classification Method. The scale II surrounding rock has poor stability and it is soft, broken seriously weathered there are, joints, and fissure growth. It is soften and mudded when water exists. In accordance with the requirements of NATM, different construction methods and technical measures were used during construction for different surrounding rock scales to realize safe, quality, economic and effective tunnelling. 3. NEW PRACTICE OF NATM CONSTRUCTION 3.1 Scale IV and V surrounding rock section In general, drilling and blasting method will be used for tunnel excavation in scale IV and V surrounding rock sections. In Dongfeng tunnel, excavation was also carried out by drilling and blasting method in scale IV and V surrounding rock sections, combined with smooth blasting method. But, in real operation, maintaining and utilizing self support capability of surrounding rock was taken as a basic point to reduce interference to surrounding rock as possible. The double excavation method of "advanced Central pilot, reserved smooth blasting layer and smooth blasting for enlargement" was firstly proposed. (1) Central pilot excavation According to the tunnel transverse section size.

ABSTRACT: The dispersed cartridge blasting design, which is a further optimization of the loading structure of chamber blasting is evolved from the concentrated cartridge blasting design.. This paper mainly introduces the basic conditions and character analysis of dispersed cartridge blasting, design and choice of blasting parameters and the excavation procedure as well as the chamber-cutting method in single-track railway construction. 1. THE POSING OF THE ISSUE Chamber loosening blasting has more than one advantages with obvious economic benefits: it is not limited by topographic conditions: it doesn't need large drilling and blasting equipment: and it can be done at several faces at the same time, which helps to increase working speed, shorten construction duration, and lower construction cost, hence it has a wide application in rock blasting of large quantities. For rock excavation in railway construction, except for very hard monolith, chamber blasting is usually adopted for loosening purpose. However, since the road cutting is of a trapezoidal section and the width of excavation for a single-line railway is relatively small (6–8m), concentrated cartridge blasting is usually adopted, leaving a V shaped crater. The shortcoming of such a blasting design is the large charge of the primary explosive and the shaking effect of blasting on the side slopes. In fact, by comparing the actual excavation outline with the designed outline, we find that large quantities of over breaking at the top and under-breaking at the bottom often happens with concentrated cartridge blasting, resulting in a substantial quantity of work for the side slopes, which, on the one hand, has a negative effect on the stability of the side slopes, and on the other hand, will also incur additional cost to the project. To make use of the advantages and overcome the disadvantages of chamber blasting, the key technology is to modify the concentrated charging structure so as to reduce the shaking effect of blasting on the side slopes and improve the shape of the crater to be as similar as possible to the designed road cutting section. 2. HOOSING THE KEY TECHNOLOGY TO BE INVESTIGATED Engineering experiences have proved that, compared with concentrated cartridge blasting, the column-cartridges blasting can more evenly distribute the energy released, reduce the ratio of blocks and excessive crushing, help the inversion of the casting energy, and reduce the influence on the stability of the slopes. There are both difference and similarity between the working process of column-cartridges blasting and concentrated cartridge blasting. The blasting parameters of the former can be derived from the latter and the charge quantity can be calculated according to the concentrated cartridge and then evenly distributed into column cartridges according to the volume to be blasted. So, column-cartridges blasting, if it could be used in road cutting, would be an ideal plan. However, because of the relatively narrow section of excavation, and in order to guarantee the conformity to the designed outline, the one-time excavation depth in a single line railway is usually controlled within 10m.