Behavior of noncircular tunnels excavated in stratified rock masses – Case of underground coal mines

The amount of tunnels excavated along stratified/sedimentary rock masses in Quangninh coal mine area,Vietnam, is gradually increasing. Rock mass in Quangninh is characterized by beddings between rock layers. The behavior of stratified rock masses surrounding the tunnels depends on both the intact rock and the beddings between rock layers. The main characteristics of stratified rock masses that need to be considered are their heterogeneity and anisotropy. Depending on the dip angle of rock layers, movements and failure zones developed surrounding the tunnels can be asymmetrical over the vertical axis of tunnel. This asymmetry causes adverse behaviors of the tunnel structures. The objective of this study is to highlight convergences and yielded zones developed in rock masses surrounding noncircular tunnels in Quangninh coal mine area using a finite element method. The presence of bedding joints is explicitly simulated. The numerical results indicated that with the increase in dip angle of bedding joints, the stress asymmetry over the tunnel vertical axis increases. It gradually leads to an asymmetry of the failure zone surrounding the tunnel. An increase of rock mass quality means a decrease of rock mass sensitivity to the discontinuities. In addition,a dip angle of the bedding joints of approximately 45° could be considered as the critical angle at which the rock mass mechanism changes between sliding and bending.     

Key technologies and risk management of deep tunnel construction at Jinping Ⅱ hydropower station

The four diversion tunnels at Jinping Ⅱ hydropower station represent the deepest underground project yet conducted in China, with an overburden depth of 1500-2000 m and a maximum depth of 2525 m.The tunnel structure was subjected to a maximum external water pressure of 10.22 MPa and the maximum single-point groundwater inflow of 7.3 m~3/s. The success of the project construction was related to numerous challenging issues such as the stability of the rock mass surrounding the deep tunnels, strong rockburst prevention and control, and the treatment of high-pressure, large-volume groundwater infiltration. During the construction period, a series of new technologies was developed for the purpose of risk control in the deep tunnel project. Nondestructive sampling and in-situ measurement technologies were employed to fully characterize the formation and development of excavation damaged zones(EDZs), and to evaluate the mechanical behaviors of deep rocks. The time effect of marble fracture propagation, the brittleeductileeplastic transition of marble, and the temporal development of rock mass fracture and damage induced by high geostress were characterized. The safe construction of deep tunnels was achieved under a high risk of strong rockburst using active measures, a support system comprised of lining, grouting, and external water pressure reduction techniques that addressed the coupled effect of high geostress, high external water pressure, and a comprehensive early-warning system. A complete set of technologies for the treatment of high-pressure and large-volume groundwater infiltration was developed. Monitoring results indicated that the Jinping II hydropower station has been generally stable since it was put into operation in 2014.     

India and alternative sources of energy – a review

India should rely on its abundant renewable energy sources to not only facilitate steady and high economic growth but also enable it to meet its commitment to reduce pollution up to 35% less than the 2005 level. On this platform It can expect financial and technological support from the world community.     

Experiences and lessons from the use of TBM in the Himalaya – A review

Tunnel boring machine (TBM), with its many advanced features, is being regularly planned now for the excavation of long tunnels in the difficult geology of the Himalayan region. The experience, so far, with the TBMs in three tunnels of Himalayas in India has not been encouraging. However, efforts are being made to overcome the problems and make the TBM a successful venture in the difficult grounds of Himalaya in India. The recent successful completion of 14.75 km long TBM portion of head race tunnel in Kishanganga hydroelectric project in J&K state has shown that the TBM can be used in the Himalayan tunnels as well.In the paper the experiences of TBM in four Himalayan tunnels are briefly highlighted. In case of Tapovan-Vishnugad head race tunnel, the variation of ground in terms of difficulty in managing the TBM thrust and penetration rate has also been highlighted. At the end, some issues have been presented which seems to be important for the success of TBM in the difficult grounds.     

A hierarchy of measures for infrastructure resilience – learning from post-disaster reconstruction in Christchurch,New Zealand

Recent research into the concept of resilience has shown that it helps key players in urban development to assess and set priorities for resistance and recovery for disaster risk management. However, a competing issue within post-disaster recovery is managing the trade-offs between quickly restoring infrastructure services versus taking time to consider and consult on alternative options. Through an examination of the post-earthquake reconstruction in Christchurch, New Zealand, this paper considers infrastructure resilience by using a hierarchy of measures. This hierarchy shows how infrastructure resilience needs to be considered as a series of interventions in response to different levels of damage. It elucidates the varying nature of resilience measures, the decision-making processes required to implement them and constraints, chiefly in funding, that prevent wider application of such measures. This is an important consideration for defining and acting upon the opportunity for change created by a disaster. Furthermore, a broader examination of resilience in disaster risk management highlights that clarification is needed over what constitutes an appropriate response for community involvement in post-disaster infrastructure reconstruction.     

Gelgard—A new fire retardant for air and ground attack

Viscous water and gels have been proven to be more effective on forest fires than plain water. In 1963 and 1964, a new member of this family of fire retardants was tested. The authors describe the properties and characteristics of the compound, report the results of laboratory and field tests, and compare its effectiveness to that of plain water and other viscosity agents.     

How can authorities support urban consolidation centres? A review of the accompanying measures

Freight transport affects urban welfare primarily through congestion and emissions. An urban consolidation centre is regarded as a solution that can reduce those negative impacts of freight vehicles on the city. However, previous experience has demonstrated the challenge that these centres face in being self-sustaining. Given their positive effects on the city, authorities have supported these logistics schemes with different types of accompanying measures. In order to bring to practitioners an overview of these measures, the paper presents the results of a literature review where the different measures are classified according to their financial support, their regulatory support and their indirect regulatory support.     

Geotextiles for unpaved roads—A review of design procedures

Fabrics have been successfully used for unpaved roads on very soft subgrade for some time, usually fulfilling one or more of the basic functions of separation, filtration, drainage and reinforcement. A number of structural design procedures have recently been developed which mostly rely on the fabric controlling subgrade failure mode, improving surface load distribution and providing membrane support. The results of some of these procedures are compared for particular soil and fabric properties and traffic conditions; and design charts based on Apple computer programs are presented. Several of the design methods appear to give equally reasonable results; but it is pointed out that fabrics should also be selected based on expected construction survivability and workability and that careful management of construction activities is vital for successful use of fabrics in unpaved roads.     

Smart partition system – A room level support system for integrating smart technologies into existing buildings

We proposed a support system called the “Smart Partition System” for infill elements that integrate smart technologies according to the Open Building principles. The design requirements were collected from design practitioners. These design requirements consisted of both architectural and information subsystems. The Smart Partition System was composed of the following multiple levels of smartness: the foundation/core level with an embedded design knowledge in the support system and the utility level with a modular infill that integrate smart technologies. We constructed functional prototypes to demonstrate the feasibility of our proposed support system and some of the possibilities of the smart infill elements. Furthermore, the prototypes were evaluated by design practitioners. We compared our approach with current practices of smart building developments, and we also discussed some future prospects.     

Applications of additive manufacturing in the construction industry – A forward-looking review

Additive manufacturing (AM), also known as 3D printing, fabricates components in a layerwise fashion directly from a digital file. Many of the early applications of AM technologies have been in the aerospace, automotive, and healthcare industries. Building on the advances in AM in these industries, there are several experimental applications of AM in the construction sector. Early investigations suggest that use of AM technologies for construction have the potential to decrease labor costs, reduce material waste, and create customized complex geometries that are difficult to achieve using conventional construction techniques. However, these initial investigations do not cover the full range of potential applications for construction or exploit the rapidly maturing AM technologies for a variety of material types. This paper provides an up-to-date review of AM as it relates to the construction industry, identifies the trend of AM processes and materials being used, and discusses related methods of implementing AM and potential advancements in applications of AM. Examples of potential advancements include use of multi-materials (e.g., use of high-performance materials only in areas where they are needed), in-situ repair in locations that are difficult or dangerous for humans to access, disaster relief construction in areas with limited construction workforce and material resources, structural and non-structural elements with optimized topologies, and customized parts of high value. AM's future in the construction industry is promising, but interdisciplinary research is still needed to provide new materials, new processes, faster printing, quality assurance, and data on mechanical properties before AM can realize its full potential in infrastructure construction.     

Housing and Resilience – When,for Whom and for What? A Critical Agenda

ABSTRACT

As a concept resilience is proving remarkably…resilient. It has become a keyword used to describe the contemporary urban and environmental condition. However, unlike that other prolific keyword “sustainability”, it lacks both the ethical intent (if not practice) and international agreement of the Brundtland Report directive to seek to balance economic, social and environmental outcomes for the benefit of future generations. Resilience, like concepts such as flexibility, efficiency or social capital, can be highly politicized and often mean very different things to different people. Herein lies both the potential and pitfalls of such a term, especially when it has become such a powerful signifier for how best to respond to the conditions inherent in our climate of change. Within housing research scholarship and practice, the concept is both ubiquitous and under-theorized. This special issue seeks to draw critical attention to the use of the concept. Key questions for housing include: Resilience in housing how, when, for whom and for what?     

Prediction and prevention of rockburst in metal mines——A case study of Sanshandao gold mine

Rockburst is a kind of artificial earthquake induced by human activities,such as mining excavations.The mechanism of rockburst induced by mining disturbance is revealed in terms of energy in this context.For understanding the rockburst mechanism,two necessary conditions for the occurrence of rockburst are presented:(1)the rock mass has the capability to store huge amount of energy and possesses a strong bumping-prone characteristic when damaged;and(2)the geological conditions in the mining area have favorable geo-stress environments that can form high-stress concentration area and accumulate huge energy.These two conditions are also the basic criteria for prediction of rockburst.In view of energy analysis,it is observed that artificial and natural earthquakes have similar regularities in many aspects,such as the relationship between the energy value and burst magnitude.By using the relationship between energy and magnitude of natural earthquake,rockburst is predicted by disturbance energy analysis.A practical example is illustrated using the above-mentioned theorem and technique to predict rockburst in a gold mine in China.Finally,the prevention and control techniques of rockburst are also provided based on the knowledge of the rockburst mechanism.     

Modeling occupancy and behavior for better building design and operation—A critical review

People spend more than 90% of their life time in buildings, which makes occupant behavior one of the leading influences of energy consumption in buildings. Occupancy and occupant behavior, which refer to human presence inside buildings and their active interactions with various building system such as lighting, heating, cooling, ventilation, window blinds, and plugs, attract great attention of research with regard to better building design and operation. Due to the stochastic nature of occupant behavior, prior occupancy models vary dramatically in terms of data sampling, spatial and temporal resolution. This paper provides a comprehensive review of the current modeling efforts of occupant behavior, summarizes occupancy models for various applications including building energy performance analysis, building architectural and engineering design, intelligent building operations and building safety design, and presents challenges and areas where future research could be undertaken. In addition, modeling requirement for different applications is analyzed. Furthermore, a few commonly used statistical and data mining models are presented. The purpose of this paper is to provide a modeling reference for future researchers so that a proper method or model can be selected for a specific research purpose.     

Acidic attack of cement-based materials—a review Part 2. Factors of rate of acidic attack and protective measures

This paper shows that both the aggressivity of an acidic environment and acidic resistance of cement based materials are of a complex nature. Both depend on several conditioning factors. Therefore, the evaluation of the aggressivity of the environment only on the concentration of the aggressive species is entirely unsatisfactory and incorrect. On the other hand, even the evaluation of the acidic resistance on the cement used is inadequate. Therefore, further factors should be taken into consideration, conditions like the action of the aggressive medium on cement based material and the processing factors, e.g. w/c used, curing mode and others, conditioning the resistance of cement based materials. The various possibilies of protecting cement-based materials are considered. These are based on the optimal choice of the composition of the mixture, its consolidation and curing, aimed at ensuring maximal density and minimal permeability of the hardened material. A further possibility represents the application of surface coatings. The most effective way seems to be the preparation of materials on binders of new generation ensuring the compatibility with the acidic environment.     

Performance and emission characteristics of homogeneous charge compression ignition engine – a review

Homogeneous charge compression ignition (HCCI) engine uses a relatively new mode of combustion technology. In principle, there is no spark plug or injector to assist the combustion process, and the combustion starts at multiple spots once the mixture has reached its auto-ignition temperature. The challenges over the operation of HCCI-mode engines are the difficulties of controlling the auto-ignition of the mixture, operating range, homogeneous charge preparation, cold start, controlling knock and emissions of unburned hydrocarbon (UHC) and carbon monoxide (CO), which needed to be overcome to achieve successful operation of HCCI-mode engine. This paper reviews the working principle of HCCI-mode engine and analyse the knocking in the HCCI combustion. And it also reviews the impact of homogeneous charge on HCCI combustion parameters, such as heat-release rate and maximum pressure. Furthermore, it reviews the performance and emission characteristics of HCCI engine. For each of these parameters, the theories are discussed about successful operation of HCCI engine with comparative evaluation of performance and emission reported in the literature.     

The control of surface water runoff from new development – UK national ‘policy’ in need of review?

With regard to current practice in the UK for the control of runoff from new development, there appears to be a lack of appreciation by regulatory authorities of the true consequences of a policy of widespread flow attenuation. If over-zealously applied, this form of flood control may prove counter productive. A blanket policy of attenuation over a period of many years in disregard of sub-catchment interactions may actually be leading to increases in flood-damage costs in downstream areas. There is a need for sensible co-ordinated national policy, and this paper identifies a number of key principles that might represent best practice.     

Tests and analysis of mechanical behaviours of rock bolt components for China’s coal mine roadways

A series of laboratory tests were performed to study the mechanical behaviours of newly developed high strength rock bolt components, including rebar, thread, plate, and domed washer. The characteristi...     

Centralized bid evaluation for awarding of construction projects – A case of India government

Reviewing the procedures of contractor selection in government departments in various countries and in the Rural Development Department (RDD) in India, this paper brings out several weaknesses of the current contractor selection procedure. It suggests a centralized contractor evaluation process with the inclusion of three new selection attributes along bid price. The suggested attributes are: (1) time quoted to complete the project, (2) warranty period quoted, and (3) past performance score of the contractor. To solve the resulting multi-objective decision-making problem, the paper proposes a binary goal programming model. When tested with the existing contractor selection procedure for six past projects in RDD, the model yields the same results as those taken by RDD in the past, confirming the credibility of the model. When tested with the suggested procedure, the model yields much superior results.