Key protection techniques adopted and analysis of influence on adjacent buildings due to the Bund Tunnel construction

The Bund Tunnel is 14.27 m in diameter. It is the first application of super diameter earth pressure balanced shield (EPBS) in China. There are many historical buildings along the construction line, and the minimum horizontal distance from the building to the tunnel side varies from 1.7 m to 30 m. Considering the importance of these historical buildings and the complicated construction processes, it is essential to adopt effective protection techniques to ensure safety during the tunnel construction. Three kinds of protection techniques are presented in this paper. Firstly, underground cut-off wall built by bored piles is used to separate the buildings and tunnel when the minimum horizontal distance from the building to the tunnel side is less than 5 m. Secondly, the grouting reinforcement technique is adopted when the minimum clear distance is between 5 m and 10 m. Finally, if the minimum clear distance is larger than 10 m, the optimized construction parameters are selected to reduce the influence induced by the EPBS excavation. The deformations of some typical buildings are monitored. The results of this project will be a useful reference for similar future projects.     

Bidirectional construction process mechanics for tunnels in dipping layered formation

The geological conditions surrounding the Tianpingshan Tunnel of the Gui-Guang railway in Guizhou Province are very complex. To study the mechanical regularity of the Tianpingshan Tunnel during construction process, a 3-D physical model was carried out based on the conditions of the section located between 372.335 km and 372.435 km (DK372 + 335 ∼ DK372 + 435) of the tunnel. The 3-D physical model was conducted to clarify the effect of the dipping formation and bidirectional excavation on the tunnel deformation. The results of the crown settlements, floor heave and radial displacement of the equivalent sections in the physical model were analyzed. In the physical model the results of the model test show that in the section located at 25 cm the crown settlements are much smaller than those in the section of 175 cm. And the floor heave in the section located at 25 cm is larger than that located at 175 cm. Furthermore, the radial displacement in horizontal direction is found to be much larger than that in vertical direction in the section located at 25 cm. However, the variation characteristics of radial displacement in the section located at 175 cm are reverse to that in the section located at 25 cm. The numerical study and the field measurements were compared with the model test to demonstrate the effectiveness and accuracy of the results of the numerical study.     

Environmental driving forces of urban growth and development: An emergy-based assessment of the city of Rome,Italy

Large urban systems can be considered as the final point of convergence of resources, environmental services and human activities from rural settlements to villages to towns to small and big cities. The emergy synthesis method is applied in order to capture the complexity of urban systems from the point of view of the larger scale, the geobiosphere, where resources come from. Emergy is the total available energy of one kind (usually solar) directly or indirectly used up to drive a system or a process. It can be considered as a measure of a system's demand for environmental support. The population of Rome is 4.43% of total Italian population, with an emergy use of about 4% of total emergy supporting the Italian economy. Emergy use per capita is 5.50E+16 seJ/year, compared to an average value for Italy of 3.60E+16 seJ/year. An empower density of 1.09E+14 seJ/m²/year was calculated for Rome, much higher than for average Italy, 6.86E+12 seJ/m²/year. Finally, the emergy/GDP, an indirect measure of economic performance of the system, is 2.43E+12 seJ/€ for Rome compared to 1.64E+12 seJ/€ for Italy, suggesting that in an urban system (generally characterized by a larger fraction of tertiary activities) the required environmental support for the generation of economic results is much higher than for the whole economic system. Finally, comparison of above performance indicators with similar studies published by other authors (Taipei, San Juan and Macao) points out that Rome has the highest annual emergy per capita (suggesting higher potential standard of living).     

Ground response of closely spaced twin tunnels constructed in heavily overconsolidated soils

As part of the City of Edmonton’s light rail transit expansion, twin 6.5 m diameter oval shaped tunnels were constructed using conventional tunnelling methods. The geology of the site consists predominately of a hard, fissured cohesive till unit. The tunnel face construction was sequenced as top header, bench and invert excavations. At its narrowest, the pillar separating the twin tunnels was less than 1.5 m across or 0.23 tunnel diameters. Typically, the minimum pillar spacing required to reduce the interaction between twin, side by side tunnels is one tunnel diameter. Because the tunnel construction was within an urban environment, there was considerable concern with ground loss and excessive surface settlements. This study demonstrates that within similar materials, a pillar width of 0.5 tunnel diameters sufficiently reduces the tunnel interactions and minimize the risk of damage to nearby structures.     

上海新城建设研究

新城是大城市城镇体系的重要组成部分,新城建设有助于疏散大城市人口和产业,缓解＂大城市病＂。在新一轮上海城市总体规划中,新城作为郊区建设的重点,其地位正日益凸显。利用六普人口数据,探讨上海人口增长和新城人口集聚态势;通过新城实地调研,掌握新城建设发展现状及存在问题;结合人口发展与新城建设,提出相关对策建议以推动未来新城的进一步发展。     

我国新城规划建设中的交通问题思考

目前我国新城发展面临的主要交通问题表现在新城与中心城之间的交通联系多以过境高速公路为主,不收费的快速路连接和大运量快速公共交通方式建设滞后,新城之间、新城与城市其他重要功能区之间的交通连接不足,新城开发缺乏与快速公共交通体系节点的整合等。借鉴巴黎新城和美国华盛顿特区阿灵顿县的经验,在分析新城交通需求特征基础上,研究提出交通问题的4方面建议交通建设与新城开发在时机上要相互呼应;新城与中心城、新城与新城的交通联系方式;新城交通与土地的联合开发;适时建设新城绿色交通。     

Millau viaduct geotechnical studies and foundations

The Millau viaduct over the Tarn River is an exceptional bridge considering the height under the deck and the 2.5 km total length. Each of the seven high piers is founded on a thick raft setting on four large piles of 5 m in diameter and 10–15 m deep. The ground schematically consists of limestone in the north and of marls in the south. As the bridge is very sensitive to foundation settlements, the concessionary company decided to use the observational method for controlling the displacements and if necessary stabilize the foundations. The measurements show that the movements have remained small and admissible, particularly in terms of the rotations. The settlements have not occurred continuously under the load, but by steps.     

The problem of human response to blast induced vibrations in tunnel construction and mitigation of vibration effects using cautious blasting in half-face blasting rounds

Blast induced ground vibrations generated by explosives in tunnel construction may cause structural damages in or close to urban areas. Therefore, the aim in blasting must be to suppress the vibration effects and mitigate the possible hazard on structures. But the psychological character of human response to vibrations involves highly subjective attitudes about what kind of environment is “acceptable” even if no structural damage is occurred. Therefore, we utilize the method of cautious blasting for half-faces that is environmentally friendly, and easy to utilize for tunnel construction. Small charges in this method are detonated sequentially to produce minimum side effects. This method is tested in a tunnel construction in Istanbul with numerous experimental shots. In these experiments, the duration and also quantity of explosives are carefully controlled. Regarding human response, better results are obtained with short durations (about 300 ms) compared to long durations (9000 or 480 ms). The quantity of maximum co-operating explosive charge decreases from 3.088 to 1.744 kg while the vibration levels defined as peak particle velocity (PPV) become more tolerable around 300 ms shot durations.     

Effect of adverse geological condition on TBM operation in Ghomroud tunnel conveyance project

With the planned length of 36 km, Ghomroud tunnel is one of the longest tunnels under construction in central Iran. About half or 18 km of this tunnel was excavated by a double shield TBM. Several adverse geological conditions encountered, consisting of ground squeezing and face collapse, hindering TBM performance, and caused several TBM stoppages and jamming. This paper presents the impact of ground conditions on machine performance based on the information obtained from field observations and geotechnical site investigations. As built geological conditions are described while the method and results of tunnel convergence measurements and their impacts on tunneling operation is examined. Based on the detail study of the available geological information and tunnel convergence measurements, it was evident that the existence of weak structures in rock mass resulted in high rate of the convergence, which was the dominant factor in the TBM jamming. Since it was not possible to make observation and measurements of geological parameters when working in a lined tunnel built by a shielded machine, an attempt was made to correlate TBM operational parameters and ground convergence. The preliminary result of the analysis has indicated a good correlation among machine’s operational parameters and tunnel convergence. If the system is fully developed, these parameters can be used as an indicator of the potential for high rates of convergence. An early warning on ground convergence is essential for taking precautionary measures to avoid TBM from getting jammed by squeezing ground.     

Physiological condition monitoring of construction workers

Monitoring of workers' physiological conditions can potentially enhance construction workforce productivity, safety, and well-being. Recently, Physiological Status Monitors (PSMs) were validated as an accurate technology to assess physiological conditions during typical sport science and medicine testing procedures (e.g., treadmill and cycle ergometer protocols). However, sport science and medicine testing procedures cannot simulate routine construction worker movements in a comprehensive manner. Thus, this paper investigated the validity of two PSMs by comparing their measurements with gold standard laboratory instruments' measurements at rest and during dynamic activities resembling construction workforce's routine activities. Two physiological parameters such as heart rate and breathing rate were considered. Ten apparently healthy subjects participated in the study. One of the PSMs proved to be a viable technology in assessing construction workers' heart rate (correlation coefficient ≥ 0.74; percentage of differences within ± 11 bpm ≥ 84.8%).     

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.     

Experimental study on thermal behavior of a building structure using rubberized exterior-walls

Addition of scrap-tire pieces into cementitious composites improves their thermal insulation performance. Development of such construction materials with lower thermal transmittance reusing these wastes is a challenging issue since it provides a combined solution for today's energy saving and environmental pollution concerns. In favor of this, recent European Union directives have brought quiet strict limits to reduce energy consumption and landfill disposal of solid wastes. A model room whose exteriors are fully made with scrap-tire added concrete is built here to increase its thermal protection. A standard/conventional room at identical dimensions but surrounded by ordinary concretes is also built to examine influence of scrap tire addition on room's thermal protection. Long-term thermal behaviors of these two rooms are investigated and compared under real atmospheric environments. Their indoor temperatures reveal that addition of scrap tire pieces lowers both indoor temperature variations and the effect of outdoor conditions. As an example, mean values of yearly thermal time lag are found to be 3.28 and 2.96 h, respectively for the rooms built with and without using scrap tire pieces, corresponding to nearly 11% improvement in thermal protection. Results in overall verify that scrap tire addition improves thermal protection of the room and it is a cost effective solution for people with low income and/or individuals living in rural areas.     

Design and construction recommendations to improve impermeability in rainscreen walls built with natural stone coverings

In current European construction, the building model of stone coverings detached from the building support is being increasingly used. These coverings remain joined to the rest of the façade only by certain anchorage points, leaving thus a cavity between the stone panels and the inner support. This is the model that best adapts to the actual concept of heterogeneous façade, with high performance qualities and predictable behaviour.Walls designed to achieve a high degree of air pressure equalization between the inner cavity and the exterior, obtaining considerable benefits, are known as Pressure Equalized Rainscreen (PER) walls. Existing design guidelines on these walls are mainly qualitative and referred to a theoretical continuous wall, with few references to real construction methods or discontinuities of the façade.Behaviour of PER walls, when built with stone panels of medium thickness (30–40 mm) and open horizontal and vertical joints, is analysed in this study, based on the climate in the city of Valencia (Spain). Although panels of 12–20 mm thickness are often used in many countries, the Spanish Technological Standards recommend using panels of at least 30–40 mm in this type of façades, being thus this thickness the most common in Spain. The aim of the study is to understand rainscreen wall performance in this case, with regard to water coming into contact with the façade, and thus propose several design and construction recommendations to improve impermeability in crucial points of the façade.     

Application of ground penetrating radar in grouting evaluation for shield tunnel construction

Uniformity and quality of the grout behind the lining segments have a great influence on the long-term settlement in shield tunnel construction in soft soil areas. In order to evaluate the effectiveness of the grouting treatment before the tunnel operation, a nondestructive testing method using ground penetrating radar (GPR) was proposed to detect the grout thickness behind the lining segments of metro lines in Shanghai, China. GPR has shown to be a viable approach due to the facts that: (1) the detecting objects (concrete segments, grout and soil) were in the depth of one meter or less; (2) dielectric parameters of all the materials can be obtained from the laboratory; (3) the contrasts in the dielectric properties among these three materials were large enough; (4) only the boundary between the grout and the soil needed to be found since the concrete segments had a known even thickness of 0.35 m. Three GPR frequencies 250 MHz, 500 MHz and 1 GHz were used in the field tests in Shanghai Metro line 9. The results showed that the 250 MHz GPR had a low resolution while the 1 GHz GPR had a shallow detecting depth. Frequency at 500 MHz showed the most promising results. These tests results demonstrated that nondestructive geophysics techniques such as GPR detection can be used to mitigate the risks of long-term ground settlement, a critical issue of shield tunnel construction in soft soil areas such as Shanghai.     

Energy-efficient terrace houses in Sweden: Simulations and measurements

Reducing energy use in buildings is essential to decrease the environmental impact. Outside Gothenburg in Sweden, 20 terrace houses were built according to the passive house standard and completed in 2001. The goal was to show that it is possible to build passive houses in a Scandinavian climate with very low energy use and to normal costs. The houses are the result of a project including research, design, construction, monitoring and evaluation. The passive house standard means that the space heating peak load should not exceed 10 W/m² living area in order to use supply air heating. This requires low transmission and ventilation losses and the building envelope is therefore highly insulated and very airtight. A mechanical ventilation system with approximately 80% heat recovery is used. The electric resistance heating in the supply air is 900 W per living unit. Solar collectors on the roof provide 40% of the energy needed for the domestic hot water. The monitored delivered energy demand is 68 kWh/m² a. Energy simulations show that main differences between predicted and monitored energy performance concern the household electricity and the space heating demand. Total delivered energy is approximately 40% compared with normal standard in Sweden.     

Construction of a large-section long pedestrian underpass using pipe jacking in muddy silty clay: A case study

This paper presents a case study of constructing a large-section long pedestrian underpass using pipe jacking method in Nanjing, China. The underpass, having a width of 7 m and a height of 4.3 m, was jacked 94.5 m in muddy silty clay under a busy roadway with 6.2 m overburden soil, meanwhile it traverses above the existed shield metro tunnels with just 4.5 m from the underpass bottom to tunnel vault. This paper introduced the design and construction schemes of this project in detail. A pre-construction three dimensional numerical simulation was conducted to investigate the responses of the roadway and metro tunnels to pipe jacking construction. Based on the simulation results, the field monitoring program was proposed, and the tunnels deformation and ground settlement were constantly monitored. The field performances of the metro tunnels and roadway were analyzed according to the monitoring data. In the jacking process, the micro-underbreak method was adopted. In order to decrease the tunnels uplift and ground settlement, the actual volume of soil conveyed out from soil chamber to ground surface was kept 95–98% of theoretical soil volume cut by cutter head. In general, this project is completed successfully without taking any additional time and money-consuming deformation control measures. The ground traffic and underneath metro runs well during the whole construction process.     

The effect of using different polymer and cement based materials in pore filling applications on technical parameters of travertine stone

The usage of marbles as a natural building and facing stone shows a gradually rising trend in civil sector all over the world. Due to natural motion, structure of marbles consists of many cracks and holes during formation of rocks. Cracks and holes in the marbles generally increase the wastage ratio and operating costs during production of marbles. Normally, the color consistency, brightness of the colors, hardness, strength, non-porous smooth surface as a hygienic structure are desired properties in the usage of flooring and facing stones.In this study, application of some pore filling methods in travertine and their effects on technical parameters of the rock structure were experimentally investigated. Although travertine has high porosity and is composed of different sizes of pores in its structure, it has a wide usage area in the construction and facing stone industry. Its processing is very easy and is much cheaper than the other marble types. Two different applications were mainly used for the pore filling process. These methods are polyester filling technique and cement filling technique. The use of cement filling method is widely applied in travertine production. The effects of these methods on the rock structure were analyzed and the most suitable filling technique was determined based on the technical data of rock parameters.In this study, in addition to the effective use of cement as a filler material in a travertine stone, different ratios of polymer admixtures as a Stuff (ST) and Poliacrilamid (PA) were used to evaluate the collapse of the filling material through the pores with optimum setting time. These materials were used as a replacement of the cement and calcite with the ratios of 0.1%, 0.5%, 1.0%, 1.5% and 2.0%. Test samples were prepared in the form of 40 cm × 40 cm × 1.2 cm tiles and different ratios of the mixture of cement, calcite and polymer materials were applied on the rock surface. These samples were analyzed in terms of water absorption, point load index and unit volume weight measurements by using appropriate standards, TS 699 and ISRM. According to test results, it was tried to compare the filled and unfilled material properties and to obtain optimum ST–PA and cement usage ratio with respect to improving polishing quality, physical and technical parameters of rock.     

Design and construction of river crossing tunnel beneath Tachia River,Taiwan

Due to the impact of the 1999 Chi-Chi earthquake (ML = 7.3) and the following typhoon induced heavy rainfalls and floods, the tailrace tunnel of the Kukuan Hydropower Plant was severely blocked and must be realigned and rebuilt. The new tailrace tunnel is 1991 m long with a 140 m section passing underneath the Tachia River, where the shallowest rock cover is 3.5 m. In view of the common phenomenon that weak zone developed along river channel and debris accumulated on river bed, the ground improvement from the surface to the tunnel is difficult. Therefore, a construction shaft, a water sealing pre-grouting plan and a special supporting system were designed to prevent the potential water inflow when tunneling underneath the Tachia River. In the construction phase, adequate excavation cross sections, support elements, auxiliary treatments, and water sealing grouting methods were selected to overcome the difficult ground condition encountered. The experience learned from this successful case can be a valuable reference for the design and construction of similar river crossing tunnels in the future.     

Experimental evaluation of the flexural behavior of corroded P/C beams

Corrosion phenomena and related effects, such as size reduction in both rebars and strands, bond decay at steel–concrete interface, and cracking in the surrounding concrete, are particularly critical in prestressed-concrete members, not only for safety reasons, but also for their huge potential socio-economic effects. As a matter of fact, this technique has been used for the last 50 years in the majority of viaducts and bridges built in many countries like Italy.In order to evaluate the influence of the corrosion on prestressed pretensioned beams, a number of tests has been carried out in the Laboratory of the University of Rome “Tor Vergata”.Nine prestressed beams (section size 200 × 300; total length 3000 mm; clear span 2700 mm) were first subjected to artificial corrosion, to obtain different damage levels, and then were tested in four-point bending.The results clearly show the sizable effects that corrosion has on the ultimate capacity (that is significantly reduced), on the failure mode and on the structural response, that turns from ductile to brittle.     

Durability of masonry systems: A laboratory study

We deal with the textural aspects, porometry and hydric behaviour of combinations of building materials and their durability under attack by salt crystallisation and freezing. We selected 4 types of lime mortar (pure lime mortar, lime mortar + air-entraining agent, lime mortar + pozzolana and lime mortar + air-entraining agent + pozzolana) which were used in combination with either brick or calcarenite stone. Lime mortars were chosen because they are compatible with traditional building materials, including the bricks and calcarenites that were widely used in the historical buildings that make up our architectural heritage. There are more similarities between the pore size ranges in calcarenites and mortars than there are between those in bricks and mortars. In all cases, a fine layer of calcite microcrystals develops at the contact surface between the mortar and the stone or brick. This is produced by the transformation of the portlandite, which concentrates in this area due to capillary moisture migration. This surface may on the one hand represent an obstacle to the flow of water between the different parts of the system formed by these materials, but on the other it may also favour greater adherence between the components, especially in the calcarenite + mortar combination, which proved to be the most resistant to deterioration in the freeze–thaw tests.