Design of sequential excavation method for large span urban tunnels in soft ground – Niayesh tunnel

Modern tunnel design and construction requires appropriate techniques and technologies during all phases of a tunnel project. Selecting a suitable excavation procedure for large span urban tunnel projects in soft ground is a key factor for successful construction of the project. The costs and time for tunnel construction are strongly influenced by the choice of the excavation procedure. This research focuses on the selection of excavation method, excavation sequence and optimum trailing distance between different excavation stages in soft ground urban tunnelling. Considering soft ground condition and the big cross section of the Niayesh urban road tunnel project, sequential excavation method (SEM) was selected for tunnel construction. In this phase, Central Diaphragm (CD) and Side wall Drift (SD) methods were proposed for tunnel construction and appropriate method was selected based on its potential to limit surface settlements. Then, different excavation sequences considering side wall drift method were planned and modelled using three dimensional finite element method and optimal excavation sequence was selected. Finally, the trailing distance between different excavation stages were analysed numerically and the optimal distance with minimum surface settlement was determined.     

Influence of groundwater drawdown on excavation responses – A case history in Bukit Timah granitic residual soils

Performances of a braced cut-and-cover excavation system for mass rapid transit (MRT) stations of the Downtown Line Stage 2 in Singapore are presented. The excavation was carried out in the Bukit Timah granitic (BTG) residual soils and characterized by significant groundwater drawdown, due to dewatering work in complex site conditions, insufficient effective waterproof measures and more permeable soils. A two-dimensional numerical model was developed for back analysis of retaining wall movement and ground surface settlement. Comparisons of these measured excavation responses with the calculated performances were carried out, upon which the numerical simulation procedures were calibrated. In addition, the influences of groundwater drawdown on the wall deflection and ground surface settlement were numerically investigated and summarized. The performances were also compared with some commonly used empirical charts, and the results indicated that these charts are less applicable for cases with significant groundwater drawdowns. It is expected that these general behaviors will provide useful references and insights for future projects involving excavation in BTG residual soils under significant groundwater drawdowns.     

Characterization of the burning behavior and gaseous emissions of pine needles in a cone calorimeter – FTIR apparatus

The paper presents flammability studies related with the combustion of Maritime pine needles (pinus pinaster, representative of Mediterranean vegetation) in a cone calorimeter (CC) under air atmosphere with piloted ignition and self-ignition for different heat fluxes, from 10 to 50 kW m⁻². The Main objective is to measure the yields of the gaseous emissions released during the experiments because one of the major risks during the fire is from the smoke and products of combustion. Identification of exhaust gaseous compounds and concentration measurements have been done by FTIR, NDIR, chemiluminescence and paramagnetism gas analyzers for assessing the fire behavior and identifying the decomposition chemistry. Among the 15 different compounds simultaneously analyzed, the yields of CH₄, CO₂, CO, H₂O, NO and O₂ have been quantified. HCN and light-weight hydrocarbons (C₂H₂, C₂H₄, C₃H₆ and C₃H₈) have been observed at low concentrations.The results show that carbon dioxide and water are the main emissions during the experiments. Also, the carbon balance shows that about 5% of the carbon released as carbon monoxide and hydrocarbon whatever the external heat flux chosen. Moreover, flammability parameters such as Mass Loss, Mass Loss Rate (MLR) and Time to Ignition (t_ig) have been determined for each condition during the experiments. Pine needles is considered often as a thermally thin material. However, the bed of pine needles behaves as a thermally thick material in the conditions tested.     

Characteristics and mechanisms of large deformation in the Zhegu mountain tunnel on the Sichuan–Tibet highway

The Zhegu mountain tunnel is a typical long, deep-buried highway tunnel at a high altitude, subjected to low temperatures and high geostress. The tunnel is excavated in carbon phyllite and slate at depths of up to 1000 m below ground, which has resulted in extreme deformation, especially in a depth of 3 m from the tunnel perimeter. The maximum deformation was monitored to be 60 cm, with a maximum deformation speed of 39.3 mm/day. In addition, it took 60–120 days to complete 90% of the deformation. The deformation of the Zhegu mountain tunnel is characterized by serious subsidence of the arch, squeezing outwards of sidewalls, buckling failure of sidewalls and local collapse. The swelling of soft rock is found not to be a main factor of large deformation in the subject tunnel. Three mechanisms of large deformation are derived based on the characteristics and geological conditions, which are plastic flow of soft rock, shear sliding of wedges, and bending of thin-layered soft rock.     

Influence of acid rain on slope instability mechanism—a case study in Sichuan provincial highway,China

Bulletin of Engineering Geology and the Environment - Acid rain has important influences on the physical and mechanical properties of rock as a result of mineral conversion and dissolution of...     

Influence of the strip–backfill interaction model in the analysis of the behavior of a mechanically stabilized earth wall

To improve the modeling of friction between the ground and reinforcing inclusions, such as steel strips in reinforced earth walls, a specific type of finite element was introduced in the CESAR-LCPC finite element code. Simulations were carried out, in which these elements were used in combination with a linear elastic-perfectly plastic model to describe the interaction between the ground and the inclusions. With this simple interaction model, however, it was not possible to reproduce the observed behavior of a full-scale, experimental wall or the results of pull-out tests carried out on the same wall under the same set of parameters. Therefore, two more complex models were introduced for the soil–inclusion interaction, which led to a much better agreement between the numerical results and the experimental observations.     

Quantifying the relationship between aggregate GDP and construction value added in a small petroleum rich economy – a case study of Trinidad and Tobago

The relationship between gross domestic product and the output of the construction industry is quantified, using as a case study the economy of Trinidad and Tobago (T&T). A historical perspective is used in order that anomalies can be set within the context of the relevant time and circumstances. Because the economy of Trinidad and Tobago is highly dependent on oil and gas revenues, the relationships between construction value added, GDP and oil and gas industry parameters are also included. In nearly all instances there are positive relationships between the parameters examined, and values for the various correlation coefficients have been obtained. An examination of causal factors obtained from a cumulative experience analysis also establishes that the direction of causality runs from the changes in GDP to the increase in construction value added, both at the aggregate level and at the per capita level. A similar positive relationship and direction of temporal causality is apparent between oil and gas revenues (and prices) and construction value added. These relationships are untypical, as smaller developing economies that do not have oil resources would be expected to show negative correlations for these relationships.     

Study of correlation between specific energy of cutting and physical properties of rock and prediction of excavation rate for lignite mines in Çayırhan area,Turkey

Bulletin of Engineering Geology and the Environment - Laboratory specific energy (SE) is a reliable indicator to evaluate the rock cuttability and efficiency for mechanical excavation in mining and...     

The RUB Tunneling Device – A newly developed test method to analyze and determine the wear of excavation tools in soils

The efficiency of a tunneling project is mainly associated with the abrasivity of the acting soil and the wear resistance of the cutting tools. Heavy wear can dull the cutting tool, which negatively affects the penetration rate and therefore the efficiency of a tunneling process. Completely worn tools with a short service life have to be replaced by newer ones. This circumstance results in unplanned machine shutdowns and higher maintenance costs. It is thus of high economic as well as technical interest to obtain a deeper understanding of soil/cutting tool interactions during tunneling. To meet this challenge, a large number of different testing devices to estimate the abrasivity of soils have been developed within the last two decades. An innovative and promising experimental setup is presented in this work. A horizontal implementation offers the possibility of simulating a tunneling process as well as the tribological system of a TBM tool. The interactions between all system components can be mapped and analyzed in detail. This method offers a unique setup, which allows wear prediction of TBM tools in a homogeneous soil with project-specific parameters (soil composition/condition, soil mechanics, tool material and machine/tunneling data).     

A Comparison between Industry’s and Academia’s Perceptions of a Career in Construction Education

It is well documented that real-world experience is essential in teaching the applied sciences. However, it has also been shown that faculty positions are being filled with candidates with strong research agendas but less industry experience. The aim of this study is to understand what industry’s perception of a career in academia is like and compare it to the perceptions of those actually in the profession. This is viewed as a needed first step in attracting more industry practitioners into construction education. The study surveys practitioners and faculty on how satisfying a career in CM academia is at meeting 16 factors identified as important to overall job satisfaction. The responses of both groups were compared to evaluate where industry’s perceptions did not align with those of faculty. The study also compared the workplace attributes that industry indicated they valued most and what faculty indicated a career in education provided. The study found that a terminal degree, interest in research and publishing, interest in teaching, and salary were the greatest barriers for industry practitioners to enter CM academia. The comparison of work place priority and barriers to entry was used to provide potential strategies to encourage more industry practitioners into CM education.     

Deformation and failure of a tunnel in the restraining bend of a strike–slip fault zone: an example from Hengshan Mountain,Shanxi Province,China

Bulletin of Engineering Geology and the Environment - The Yanmenguan Tunnel runs through Hengshan Mountain in Shanxi Province, China. The mountain is mainly composed of metamorphic rock cut by a...     

Rudolf Schwarz and the speech of the land – grammar as a political device in postwar Germany

The paper examines the connection of language and urban form in the work of the German architect and urban planner Rudolf Schwarz. Schwarz, who is credited with having exerted major influence on the protagonists of modern architecture such as Mies van der Rohe, was one of the most famous architects in postwar Germany and the author of the 1950 plan for the rebuilding of Cologne's destroyed inner city. From the 1950s onwards, Cologne's once dense mediaeval nucleus was restructured by a network of six-lane thoroughfares and various sequences of scattered concrete blocks. This redesign, as radically modern as it may seem, was closely tied to Schwarz's traditionalist conception of language. His linguistic arguments were influenced by a century-long tradition among conservative German intellectuals, who strove for a deeper and unmediated understanding of the world through verbal communication. Claiming an intrinsic relationship between the structure of German grammar and of the phenomena it captures, they believed in the ‘rootedness’ of their nation in its geographic environment through language. In that respect, Schwarz's conception and use of language – which was in many ways exemplary for German city planners in the postwar era – laid the groundwork for the modernist transformation of the city and thus for a dilemma that haunted German urban planning in the decades that followed.     

Environmental values and attitudes among farmers in China – a case study in the watershed of Yuqiao reservoir of Tianjin Municipality,China

Failure to curb water pollution in China brings to the fore the issue of environmental values and attitudes among Chinese farmers. Applying the New Ecological Paradigm Scale this study finds that the pro-environmental value of New Ecological Paradigm (NEP) Worldview has a stronger standing among the studied Chinese farmers than the Dominant Social Paradigm (DSP) Worldview.     

Sediment size and deposition characteristics in Malaysian urban concrete drains – a case study of Kuching City

This paper highlights the results of sediment size characteristics and deposition analysis on 24 sediment samples from urban concrete drains in Kuching City. Further sampling from surrounding urban towns outside Kuching City and Penang were done for comparison. Samples were collected randomly from three land-use types (residential, commercial and industrial). Sieve analysis results had shown that most of the total samples collected (51 out of 57) were predominantly sand, followed by gravel; while silt and clay were the minor components. Unimodal characteristics were observed in 46 samples while 11 samples showed bimodal characteristics. Of the total 46 unimodal samples, 39 showed non-uniform distribution with tendency to skew to the right. Due to this, the mode grain size with characteristic diameter d₄₅ is suggested as a much better representative size than the conventional median size d₅₀. Factors affecting sediment deposition characteristics in urban drains are also discussed.     

Correlations of in situ modulus of deformation with elastic modulus of intact core specimens and RMR values of andesitic rocks: a case study of the İzmir subway line

Bulletin of Engineering Geology and the Environment - The main purpose of this paper is to obtain the rock mass rating (RMR) from different methods considering either the elastic modulus of intact...     

Why Build a Temple? The Materialization of New Community Ideals in the Demilitarized Islands between China and Taiwan

Since the early twentieth century religion has been seen by the Chinese state and intellectuals as an obstacle to modernization and has thus been devalued. This article points out how this pejorative view of religion has latently persisted in contemporary Taiwan in the formulation of an important policy of community development. The author draws on ethnography from the Mazu Islands, a former frontier military base, to investigate the predicaments and breakthroughs of community projects carried out there, and to show that a sense of community began to emerge only when the local elites recognized the importance of religion and began to participate in building the village temple. By allowing different generations of Mazu people to negotiate their ideas of community, the process of temple construction has transformed their often adversarial social relations. This paper demonstrates that religion, and in particular the process of its materialization, can serve as a basis for the formation of a new community in the twenty-first century.     

Introduction to a special issue: the future of landscape characterisation,and the future character of landscape – between space,time, history,place and nature

Abstract

In any discussion of landscape characterisation the elephant in the room is the question of just what is landscape? Another way of putting this question is to simply ask: ‘How would you characterise landscape?’ What this implies is that there is a certain circularity in landscape characterisation because, through the very act of characterising landscape, one is also defining what one means by landscape. The European Landscape Convention’s definition of landscape as ‘an area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors’ suggests a similar circularity because the character of an area, as it results from the action of natural and/or human factors, is dependent upon human perception, which is presumably also, in addition, one of the human factors acting upon the landscape. This circularity, or ‘circulating reference’, to use Bruno Latour’s term, is fundamental to Denis Cosgrove’s analysis of the origin of the modern concept of landscape as scenic space, and his analysis, we would suggest, helps explain some of the questions raised in this special issue concerning landscape characterisation and the future character of landscape .     

The shift to competitiveness and a new phase of sprawl in the Mediterranean city: Enterprises guiding growth in Messoghia – Athens

Spatial planning frameworks in EU member states have been increasingly supporting the growth prospects of particular metropolitan regions, deemed as regional engines of national economic growth. This paper discusses the shift in spatial planning policies towards territorial competitiveness, focusing on Greece. The country’s commitment to competitiveness was confirmed in the 1990s and was symbolically sealed with the decision to host the 2004 Olympic Games in Athens. Examination focuses on one of the key objectives behind the prioritization of competitiveness-related interventions: investment attraction and the locational traits of new business formation in the eastern Athenian hinterland is explored (1997–2010). The locational traits of startup businesses are analyzed by means of exploratory point pattern analysis on the geocoded enterprises, underscoring a sprawl-like type of growth. The proliferation of divergent modes of state spatial intervention is associated in the literature with an increase in spatial disparities. In areas with underdeveloped land-use planning structures, it is argued, competitiveness pre-occupations unsettle stated planning priorities and ‘revive’ arguments that approach unordered urban expansion as a short-cut to growth.     

Challenges and strategies involved in designing and constructing a 6 km immersed tunnel: A case study of the Hong Kong–Zhuhai–Macao Bridge

A 6 km immersed tunnel of the Hong Kong–Zhuhai–Macao Bridge (HZMB) has been designed and funded. Once completed in 2016, the HZMB Tunnel will break the record of the 5.8 km BART Tunnel in the United States, although it will soon be overtaken by the ∼20 km Fehmarn Tunnel between Denmark and Germany that is to be completed in 2020. Construction of the HZMB Tunnel was started in 2011 and more than ten elements thus far have been installed on the site. This paper presents details about the challenges and solutions for the design and construction of the HZMB Tunnel on a strategic level. Special features of the HZMB Tunnel include a long length of 6 km, a deep water depth of almost 45 m, and a thick backfill of 23 m. Challenges include severe marine environment, strict requirements for waterproofing, construction of sections connecting the tunnel with artificial islands, and tunnel stability after future excavation of fairway trenches. Moreover, the HZMB Tunnel is challenged by possible sand liquefaction in seismic events, conservation of white Chinese dolphin, and waterway dispersion during construction. Details about the strategies are given in order to improve the immersed tunnel design and construction methods.