In this paper, five empirical formulae developed for bridge design are introduced, and each term of each formula is discussed in detail. A 5,000DWT bulk carrier is modeled by commercial finite element software Ls-Dyna. Then, calculated results of the five formulae are compared with numerical results for several ship-rigid wall impact scenarios, in which Pedersen formula and TB formula (the formula in “Fundamental code for the design of railway bridge and culvert”) are selected to be further discussed because both of them include factors relevant to the deformation of the impact ship during the collision. Finally, the elastic deformation coefficients in TB formula used before are found to be too large, and the kinetic energy reduction factor is not a constant value as specified, but a function relevant with the initial kinetic energy. What's more, the values of energy absorbed by deformation in Pedersen formula are being discussed and modified.
As the accelerated development of the maritime trade and an increasing number of river and sea crossing bridges, ship-bridge impact accidents have been constantly happening everywhere in the world, of which the consequences can be disastrous, e.g. personal casualty, environmental pollution and the loss of property. For decades, there are countless ship-bridge impact accidents. In 1980, the Sunshine Skyway Bridge across Tampa Bay in Florida, the United States collapsed after being hit by M/V Summit/Venture Bulk Carrier, resulting in 35 death and great financial loss: the ship valued 1.3 million dollars while the bridge valued 2.5 million dollars. In 2002, a Russian cargo ship fully loaded with fuel ran into a bridge when navigating across Neva River for some mechanical problems, leading to oil spills harmfully to the environment. In China, the first recorded ship-bridge impact accident occurred in Wuhan Yangtze River Bridge in 1959, since when there has been almost 300 collision accidents along the main line of Yangtze River. In these incidents, some just caused a little damage to the bridge pier, while some led to bridge collapse, ship capsizing and serious personal casualty.
ABSTRACT: Providing efficient support system which prevents failures and deformations is one of the most important issues during tunnel construction especially in weak grounds. When conventional support systems such as rock bolts, shotcrete, wire mesh, steel frames and lattice girders cannot provide sufficient support for tunnels, using pre-reinforcement systems becomes necessary in addition to main support systems. Pre-reinforcement of weak ground is done before the excavation or ahead of advancing the tunnel. This will provide a safe and effective operation. Pipe roofing umbrella arch pre-reinforcement method is one of the conventional pre-reinforcement systems that can be implemented in tunnels, caverns and other infrastructures construction. Detailed 3D numerical simulations are useful tools to obtain a better understanding of the performance of a pre-reinforcement system. In this paper, sectional excavation of tunnel No.10 of the Ghazvin-Rasht Railroad is simulated with FLAC3D code by using pipe roofing pre-reinforcement method, side bolts and pipes, and initial support system. The results of numerical simulations are analyzed by using tunnel support interaction charts. Considering all technical parameters, pipes with 4 in diameter, 15 cm spacing and 5 degree installation angle is selected as the most appropriate pipe roofing method for this tunnel.
Tunneling in soft or weak ground may encounter many operational and safety problems. Under these conditions extra attention and field investigations will be required. When rock mass cannot be self-supporting, or when conventional support systems such as rock bolt, shotcrete, wire mesh, steel frame or lattice girder cannot provide sufficient support for a tunnel, using secondary support systems or pre-reinforcing become necessary. Furthermore, in urban areas shallow tunnels are often constructed adjacent to existing structures such as buildings, streets and railways (Funatsu et al., 2008). The possibility of tunnel induced displacements and subsidence that can damage the existing structures is very high. In order to minimize effects of tunneling on existing structures, engineers should pay special attention to ground displacements. Therefore, using efficient and proper support system is necessary with considerations of the project requirements and constraints such as amounts of settlements and displacements. Often, it is required to use secondary support systems or pre-reinforcing in addition to primary support system in order to ensure a safe working place during the tunnel excavation. It is obvious that if effective support system is not installed at proper time and place, tunnel will collapse and may cause extensive damage, resulting financial and human loss in the project.
Kheradi, Hamayoon (Nagoya Institute of Technology) | Guanlin, Ye (Shanghai Jiaotong University) | Nishi, Haruki (Nagoya Institute of Technology) | Oka, Ryosuke (Nagoya Institute of Technology) | Zhang, Feng (Nagoya Institute of Technology)
The collapse of Daikai station in the Kobe subway system during the 1995 Hyogoken-Nanbu earthquake exhibited that underground structures are at high risk of earthquake with shallow overburden. Though researches have been done on this issue, it is still necessary to investigate further the mechanical behavior of underground structure during an earthquake and corresponding efficient seismic enhancement. In this paper, in order to find an optimum ground-improvement pattern for rectangular-shaped box culvert constructed in soft ground that does not meet the present seismic requirement, numerical tests with nonlinear 3D dynamic FEM are conducted. Different patterns of the ground improvement for the rectangular-shaped box culvert constructed with cut-and-cover method are investigated to find out an optimum pattern that can reduce the impact of earthquake in the most effective way. In the numerical tests the structure of Daikai station is considered as box culvert. Additionally, in the 2D/3D dynamic finite element analysis, the ground is Toyoura sand, typical clean sand, and its nonlinear mechanical behavior is described by Cyclic Mobility model. Validity of the proposed numerical method is firstly confirmed with 1g shaking table test and then numerical tests are conducted to find out the optimum pattern for the ground improvement.
Underground structures, such as subway facilities, lifelines, warehouses, and so on, consist of the major parts of the infrastructure of modern society and play an important role in its development. In the design of some of underground structures like Daikai station, it was considered that underground structures are in minimum seismic risk in comparison to the aboveground structures. The collapse of Daikai station in the Kobe subway system during the 1995 Hyogoken-Nanbu earthquake exhibited that underground structures are also at high risk of earthquake especially those are constructed in soft ground with thin overburden. According to Hashash et al., 2001, “The Daikai station design in 1962 did not include specific seismic provisions”. Thereafter, the failure of the Bola tunnel in 1999 Turkey earthquake and failure of gas and water pipelines in 1999 Chi-Chi earthquake in Taiwan clarified that proper consideration of earthquake load in the design of underground structures is also important.
Greenwood, W. (University of Michigan) | Zekkos, D. (University of Michigan) | Lynch, J. (University of Michigan) | Bateman, J. (University of Michigan) | Clark, M. K. (University of Michigan) | Chamlagain, D. (Tribhuvan University)
Unmanned aerial vehicles (UAV) have the potential to become powerful site reconnaissance and data collection tools for in geoengineering. UAVs are expected to become particularly useful in geomechanics applications such as rock mass characterization, landslide imaging, and failure analysis, as part of post-disaster reconnaissance, or conventional engineering practice. A low-cost quadrotor UAV has been used as a data acquisition platform for optical imagery at a number of sites affected by the 2015 Gorkha earthquake in Nepal. The UAV collected images of landslides that would normally be very difficult, or expensive to access. Two example landslides are presented in this contribution. Structure-from-motion photogrammetry was used to generate 3-D point clouds and meshes for each site. These models were geometrically scaled using field survey measurements and used as the primary component of a landslide rock characterization scheme. 3-D models were also used to define landslide post-failure geometry. Models were used to delineate the orientation of 3-D features in the rock structure such as fractures, bedding, foliation, and stratigraphy. Multiple failure modes, including wedge failures, were also identified from 3-D models. The results of this study demonstrate the capabilities of UAVs as a tool for characterization and data collection at rock sites.
The popularity of unmanned aerial vehicles (UAV), or drones, has increased in recent years. UAVs have been used to collect optical imagery related to many engineering applications (Lin et al., 2015; Gillins et al., 2016; among others). Most commonly, the collected imagery is only used for qualitative assessments. Recent efforts have been made to introduce more quantitative assessments (Ellenberg et al., 2014; Hugenholtz et al., 2015), however, more advancements are needed to fully exploit the collected data. The increasing prevalence of UAVs along with rapidly advancing technology, presents a tremendous opportunity for UAV platforms to become powerful data collection tools in geoengineering. New technologies coupled with established imaging methods allow for low-cost UAV platforms to be useful for many geomechanics applications.
In bedrock construction projects such as dams and tunnels, it is important to have a detailed grasp of the geological structure at the project site and to perform planning and construction appropriate to the situation. To that end, in recent years there have been investigations of various construction information modeling (CIM) management methods that realize 3D modeling of the presumed geological situation and the results of actual geographic observations. This paper describes the creation of a construction site support system for geological risk, in particular issues related to geological information CIM management system development, system content, and application to actual tunnel and dam excavation projects.
In bedrock construction projects such as dams and tunnels, it is important to have a detailed grasp of the geological situation at the project site and to perform planning and construction appropriate to the situation. To that end, geological surveys and geophysical surveys are performed at the investigation and design stages to evaluate geological distribution and engineering characteristics at the planned site, and dam foundations and tunnel falsework are designed based on the results. However, at the investigative and design stages there tend to be cost limits as well as limits to the precision of the above-described geological investigations and geophysical investigations, making it difficult to obtain a detailed understanding of the geological situation over a wide area at this stage.
To address these issues, actual excavation and tunnel faces are evaluated during construction to confirm details of the geological situation directly, and to evaluate any differences from the expected situation. Depending on the results, it is important that additional engineering measures be considered and construction plans and designs reevaluated accordingly.
Against this background, there have been various investigations of a method called “construction information modeling” (CIM) in recent years (Figs. 1 and 2)1). Specifically, the geological situation as predicted from preliminary surveys is represented as a 3D model, and construction planning performed based on detailed verification of the distribution of ground defects so that appropriate measures can be employed. During construction phases, the results of geological observations of tunnel and excavation faces are added to the 3D model, thereby achieving more sophisticated and efficient construction results and aiding in reevaluations of construction plans and designs according to the situation at hand.
This paper will provide an overview of mechanized tunnel boring methods implemented at major alpine railway tunnel construction projects in the past years. A focus will be on the Amsteg/Erstfeld Lot (Gotthard Base Tunnel in Switzerland) and the Koralmtunnel Lot 2 in Austria. The lots were both driven through crystalline geological formations using open-gripper hard rock TBM’s at Amsteg/Erstfeld and hard rock double-shield TBM’s at KAT2. The difficult ground conditions for both drives will be described as well as solutions for mitigating these difficulties. The performance of the different machine concepts in the encountered ground conditions will be compared and illustrated. Another challenging aspect of handling difficult and frequently varying ground conditions is the contract execution during these trouble areas.
Since the 1990’s the European Union, Switzerland, and member countries have made large investments in the railway infrastructure for areas which lie in the heavily mountainous alpine region. The goal is to reduce the transport costs and, in addition, the increasing pollutant emissions from transport trucks by transferring the traffic flow from the roads to the rails.
2 Different Mining Concepts
The above-mentioned projects were successful with regard to the type of tunneling, be it conventional or mechanized, as well as overcoming the challenges of ground conditions, associated support processes during construction and the construction sequence.
Mechanized tunneling (TBM) is applied generally to longer tunnels with homogeneous geologies, whereas drill-and-blast (conventional) is better suited for varying geological conditions or otherwise in TBM start areas, caverns, cross-passages, accesses, and connecting structures.
At shallow depth, in situ stress can affect significantly the behavior of the rock mass around excavations, but stress measurements are usually subjected to high levels of uncertainty. This is the case at the Odenplan railway station in Stockholm where unexpected large values of displacements were recorded during the excavation. A sensitivity analysis of in situ stress in this area is thus required. As the rock mass is highly discontinuous, discrete modeling using 3DEC software is performed with three different in situ stress cases estimated from measurements. The results show that joint slip and rock mass dilatancy explain the large displacements and heaving of the ground and that a continuum approach is not reliable for this study. A comparison between the displacements from numerical modeling and those measured in situ provides indication on the range of in situ stress to be used in the future for this area.
Underground constructions in urban areas constitute an important part of the infrastructure needed for society. Being at shallow depth, their potential impact on the environment and surrounding structures can be significant. Particularly in Scandinavia, where horizontal stresses are high, performing excavations at shallow depth in brittle hard rock, combined with irregular surface topology and open fractures, can lead to large deformations and upheaving of the ground. The estimation of in situ stress is required in order to study the behavior of the rock mass around such excavations and limit its potential deformation. However, data concerning in situ stress field is usually associated with high uncertainties particularly at shallow depth where it is affected by the topography of the rock surface, near-surface weathering, exfoliation joints… Additionally, stress measurements are performed at specific points and are usually subjected to high scatter. It is therefore important to complement these measurements with back analysis at a larger scale (Kaiser et al. 2000), in order to gain insight into the in situ stress field in a specific area.
This study deals with a preliminary back analysis of in situ stress in the Stockholm area using displacement measurements performed during the excavation of Odenplan station, which is part of the Citybanan, a railway tunnel under construction by Trafikverket. Around this station, in situ overcoring stress measurements have been performed (Perman & Sjöberg 2007) and present a considerable scatter. It is also important to note that the rock mass surrounding Odenplan station is highly discontinuous. Available data from mapping shows that open fractures are unusually persistent especially those with a dip angle from 50 to 70 degrees. During the excavation of the railway tunnel, large displacements were recorded in the area where the tunnel crosses under the surface subway track. Measurements in extensometers installed between the surface and the tunnel (up to 10 mm of extension) suggest heaving of the surface rock at some locations. Such amplitudes of displacements were not accounted for during the design. Thus, a precise analysis is required to explain the phenomena observed. The access at the Odenplan station to a wide set of data (rock mass and joint properties, joint geometry, deformation and stress measurements) makes it a unique opportunity to perform a sensitivity analysis of in situ stress for the first time in this area.
A bored 13.4 m diameter highway tunnel being constructed across the Istanbul Strait in Istanbul, Turkey under a maximum 12 bars of water pressure required a deep excavation on the Asian side of the waterway for launching the tunnel boring machine and initiating NATM tunnels on the opposite end of the excavation. The excavation is up to 38.2 m deep and 173.7 m long in very poor quality sedimentary rock consisting of siltstone/mudstone and sandstone. The selection of design rock parameters considered not only data from site explorations, but previous excavation experience in Istanbul. During initial excavation stages, unexpectedly high lateral movements of the anchored support walls were measured. Using the monitoring data, a back-analysis of the excavation support system was performed to determine revised design rock parameters. The support system was modified by adding additional levels of anchors, and the excavation was successfully completed December 2013.
The Eurasia Tunnel Project is part of a new 14.6-km road link between Kazlicesme on the European side of the Istanbul Strait and Goztepe on the Asian side (Figure 1). The project helps address Istanbul's increasing traffic problems and greatly reduces the travel time across the Istanbul Strait by avoiding the need to use either a ferry or one of the city’s perimeter bridges. The project includes a 3.4-km two-deck tunnel beneath the seabed at the southern end of the Istanbul Strait (also known as the Bosphorus) constructed with a tunnel boring machine (TBM), 2 km of NATM tunnels, and 1 km of cut-andcover tunnel structures. The project also provides roadway improvements for the approaches to the tunnel. The tunnel is designed for passenger vehicles and small trucks with a limited vertical clearance of 3.0 m. The east and west bound roadways are stacked within the 13.2-m outside diameter tunnel. The Republic of Turkey, Ministry of Transport, Maritime Affairs and Communications formulated the project technical specifications. Figure 2 presents a general plan and profile for the Eurasia Tunnel Project. The various underground elements of the project are described by Clark et al. (2015).
The pipe roofing method is one of the widely used excavation support techniques for conventional tunneling. It is to install steel (or fiber glass) pipes in a canopy shape around the area to be excavated and then to excavate the soils under the protection of the pipe roof. This paper presents the optimization of the pipe roof design for the Gongbei Port tunnel excavation which represents the largest single tunnel excavation in China. The preliminary design proposed to use a pipe roof consisting of steel pipes with two different diameters which brought serious construability issues. During the construction phase, the contractor optimized the design of the pipe roof by using pipes with a uniform diameter, while adjusting the pipe layouts and optimizing the jacking and receiving plan. The new pipe roof design significantly improves the constructability, as well as reduces the construction cost and shortens the construction duration. The Gongbei Port tunnel construction expands the conventional tunneling technique by using an unprecedented large pipe roofing system along a curved tunnel alignment, and the optimization of the pipe roof design provides valuable case history experience for future projects.
The pipe roofing method is one of the widely used excavation support techniques for conventional tunneling. It is also referred as “Steel Pipe Umbrella” , “Steel Pipe Canopy” , “Umbrella Arch Method” , “Long-Span Steel Pipe Fore-piping” , or “Pipe Roof Umbrella”  in the literature. It is to install steel (or fiber glass) pipes in a canopy shape around the area to be excavated and then to excavate the soils under the protection of the pipe roof. The pipe roofing method was firstly used in Japan in 1982 and then widely used as an excavation support technique for shallowly buried underground excavations . Recent decades have seen many successful case history projects using pipe roof as an excavation support worldwide. The case history experience showed that under the protection of the pipe roof, the disturbance from the excavation to the ground can be significantly reduced and the ground movement can typically be controlled within 2 cm while the deformation of the pipe roof is smaller than 0.5 cm .
In recent years, subway has developed rapidly in many cities of China. However, the environmental problems caused by train vibration load, such as the large settlement of surrounding ground around tunnels, can’t be ignored. The subway tunnels in shanghai mainly lie in the 3rd layer of muddy-silty clay or the 4th layer of muddy clay. These two layers of clay were especially soft and sensitive to vibration load. In this paper, a numerical study on long-time deformation characteristics of soft clay around the tunnel of Shanghai Metro Line 9 under train vibration load was presented. The numerical simulation adopted an elasticplastic constitutive model that can take into account the long-term accumulation of soil deformation and excess pore water pressure under a huge number of cyclic loadings. The simulated results, including long-time displacement of soils around the tunnel, ground surface subsidence, and the variation of excess pore water pressure, were analyzed and discussed. The final settlement of surrounding ground was predicted through analyzing the variation tendency of maximum vertical displacement of soil. By comparing the simulated results and the measured data, it was proved that the simulated results were consistent with the measured data. Therefore, the long-term deformation of soil around subway tunnels under vibration load can be evaluated and predicted by the numerical method presented in this paper.
Metro has become an important part of urban public traffic because of the less occupation of land and space, fast speed and little pollution. Subway effectively eases the pressure on increasingly overloaded urban traffic and expands the available space in the city. According to statistics, the total length of metro lines has reached 1200km in China. In addition, a large number of city’s metro construction projects have been approved. With the rapid development of city rail traffic, a new round of metro construction boom will inevitably be set off. But the environmental problems caused by city rail traffic construction cannot be ignored. Among the problems, environmental impact of vibration induced by metro is particularly significant