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The excess pore water pressure (EPWP) ratio is one of the contributing factors to the earthquake-induced uplift displacement of underground structures. To investigate its role in the incompletely liquefied soil, a rectangular underground structure buried at different depths in saturated sandy soils with different densities and under different earthquake loadings was analyzed by a numerical method. The results revealed that the uplift response was related to both the EPWP ratio and its duration, as well as the region of the liquefiable soil under the underground structure. The value of the EPWP ratio that triggers uplift fell in a range rather than remaining constant. [ABSTRACT FROM AUTHOR]

The paper discusses the hydrogeological hazard for the underground infrastructures caused by the rise of the groundwater level observed in Milan (Italy). The study is the prosecution of a previous paper (Gattinoni and Scesi, “The groundwater rise in the urban area of Milan (Italy) and its interactions with underground structures and infrastructures” TUST 62(2017): 103–114), that analysed the phenomenon through a deterministic groundwater flow numerical model, pointing out the related potential hazards and the possible mitigation solutions. Starting from the reconstruction of the phenomenon previously obtained, in the present paper the 3D numerical model of the groundwater flow was turned out into a stochastic model in order to assess the hydrogeological hazard (in probabilistic terms) for the underground infrastructures. At this aim, different scenarios of the aquifer system were considered: (1) the probability distribution of the recharge describing the present day conditions; (2) the decrease in the pumping rate of wells expected in the next 15 years; (3) an increase of the regional groundwater table, based on the projection of the rising trend for the next 15 years. Modelling results have pointed out a significant increase in water level by 5 m in the next 15 years, depending on the scenarios taken into account. The water table rise interests mainly the north-western zone of the study area, and it affects the metro tunnels located in the centre of the city. Therefore, some metro tunnels will be flooded (or even submerged) with different occurrence probability. The flooding hazard increases with the increasing depth of the infrastructures, especially in the northern-central zone of the study area. [ABSTRACT FROM AUTHOR]

A highly challenging problem that has been plaguing regulators is the inaccurate collection and sharing of safety risks for underground construction. In order to establish a mechanism that could achieve timely and accurate recognition at the pre-construction stage, Building information model (BIM) is adopted as the risk recognition platform. This paper provides the automated safety risk recognition process based on BIM which is generally composed of three parts. The first part is to build the risk database. By means of knowledge structuralizing, questionnaires, depth interviews and group decision-making, explicit and tacit knowledge source are acquired. The safety risk knowledge source is divided into three categories. SQL database is used to express the safety risk knowledge, and all safety risks are stored in the BIM-cloud. The second part is to analyse the relation between engineering information and safety risks. Risk-related engineering information is extracted from BIM models. Backus–Naur form is used to describe the syntax of languages used in computing. A mapping table of engineering information and safety risks is established. The third part concerns the automated safety risk recognition mechanism in the BIM platform. The safety risk recognition mechanism is expressed as “If e, then h (CF (h, e), λ)”. The confidence level as the link is adopted to reveal the mechanism. Finally, a case about flowing sand risk at the foundation pit bottom is conducted. The reasoning process and recognition results are demonstrated. The paper concludes by summarizing the main scientific contribution and giving direction to future research in this field. [ABSTRACT FROM AUTHOR]

This study proposed a novel methodology that integrates complex network theory and multiple time series to enhance the systematic understanding of the daily settlement behavior in deep excavation. The original time series of ground surface, surrounding buildings, and structure settlement instrumentation data over an excavation time period were measured into a similarity matrix with correlation coefficients. A threshold was then determined and binarized into adjacent matrix to identify the optimal topology and structure of the complex network. The reconstructed settlement network has nodes corresponding to multiple settlement time series individually and edges regarded as nonlinear relationships between them. A deep excavation case study of the metro station project in the Wuhan Metro network, China, was applied to validate the feasibility and potential value of the proposed approach. Results of the topological analysis corroborate a small-world phenomenon with highly compacted interactions and provide the assessment of the significance among multiple settlement time series. This approach, which provides a new way to assess the safety monitoring data in underground construction, can be implemented as a tool for extracting macro- and micro-level decision information from multiple settlement time series in deep excavation from complex system perspectives. [ABSTRACT FROM AUTHOR]

The gas outburst potential is typically high when roadways uncover the gassy coal seams associated with outburst hazards. This paper describes the complex stress and displacement evolution that occurs in roadway tunnelling through coal seams under different original stress conditions, which is helpful for better understanding how the stress leads to an outburst accident, and proposing some relevant control measures. The stress concentration is primarily resulted from the strength difference between coal and rock, and the abutment stress increases gradually as the forward residual rock thickness decreases when the roadway excavation enters a coal seam from rock stratum. When the abutment stress is sufficiently high, the forward residual rock will suddenly be broken after the next cycle, and the stress will decrease rapidly to release elastic energy and generate new fractures. Meanwhile, the coal and rock in front of the heading face will move rapidly towards the free space. Therefore, an outburst accident may occur immediately when the gas pressure in front of the heading face is high enough. Once the outburst accident is triggered, the gas expansion energy and elastic energy distant from the heading face will contribute to developing the accident. The stress perpendicular to the roadway is the primary factor causing such outbursts. The abutment stress concentration will be higher when the maximum original stress is perpendicular to the roadway, which will increase the outburst potential. Therefore, it is suggested that arranging roadways parallel to the maximum original stress, if possible, can also reduce the outburst threat. Outbursts are triggered by the elastic energy near the heading face and developed by the gas expansion energy and elastic energy distant from the heading face. In this study, the method of “strong-weak” coupling circle-layers was proposed to reduce the outburst hazard when roadways excavated through gassy coal seams. This method was proven to be valid by the comparative experiment. The weak circle can be realized by boreholes and hydraulic cutting. It could not only reduce the elastic energy near the heading face but also prevent the distant energy from contributing to the outburst accident. In addition, the strong circle can be made by injecting water slurry and applying anchors. It could help to reduce the strength difference between coal and rock, thereby decreasing the local stress concentration, resisting the residual outburst energy near the heading face, and preventing the outburst from being triggered. The “strong-weak” coupling structure was successfully applied in Bailongshan coal mine when uncovering the #7,8 coal seam. This structure can effectively promote gas drainage, reduce the coal and gas outburst risk. As a result, the mining efficiency improves a lot, and the uncovering time greatly decreases from the expected 2 years to 5 months. [ABSTRACT FROM AUTHOR]

During the construction process of the Pipe-roof Pre-construction Method (PPM), the main excavation is executed under the protection of a previously created and reliable structure, which ensures safety in construction. Moreover, PPM does not affect the road traffic, generally does not require the moving of underground pipelines, and does not cause excessive surface settlement. The Xinleyizhi Station of the Shenyang subway system is a single arch long-span structure in poor geological conditions and with a complex surrounding environment and strict requirements for construction period. After considering the problems and potential solutions, PPM was used to build this station. In order to ensure safety in construction, the whole construction process was closely monitored. The surface settlement monitoring results are studied in this paper, and the causes of settlement are analyzed. According to the field measurement, the most serious settlement occurred in the layer 1–7 pipe jacking. Because of repeated disturbance and ‘shielding effect’ in pipe jacking, soil displacement mode changes, and traditional Peck formula is no longer applicable. Modified Peck formula is proposed to predict settlement caused by pipe jacking, and the specific method of taking parameters values in modified Peck formula is given. Compared to the measured transverse surface settlement curve in monitoring, it is shown that the prediction results are in good agreement with the measured results. [ABSTRACT FROM AUTHOR]

This paper proposes an Internet-of-Things-based (IoT-based) safety barrier warning system to achieve a safer underground construction site. A focus of this paper is to establish a hazard energy monitoring system and use IoT to generate early warnings and alarms as dynamical safety barriers for hazard energy on underground construction sites. To ensure the performance of the proposed system, the hazard energies and their coupling mechanisms was analyzed to provide safety barrier strategies and scenarios for avoiding unsafe behaviors and unsafe status of construction equipment and workers' environment. The IoT technologies, such as meter-level of RFID-based location and tracking technology, centimeter-level of ultrasonic detection technology, and infrared access technology and so on, were developed in three-tier network architecture to help workers change their risky behaviors and avoid accidents on the changing construction site. The implementation in Yangtze River-crossing Metro Tunnel Construction site has shown the safety performance was improved and the occurrence of accident caused by hazard energy on site could be prevented. [ABSTRACT FROM AUTHOR]

Critical velocity and smoke back-layering length are two of the determining parameters to the fire risk assessment of subway tunnel. These two parameters of a sloping subway tunnel with train blockage were investigated both experimentally and numerically in this paper. To address the influences of slope, the slopes of 0, 3, 6, 9, 12, 15% in downhill subway tunnel were studied and the height ( H) of the tunnel was replaced by the inclined tunnel height ( $$ H/\cos \theta $$ ). The train model with a dimension of 2 m (length) × 0.3 m (width) × 0.38 m (height) was also chosen in simulations and experiments for the tunnel blockage. Thenceforward, 30 reduced-scale experimental and 150 numerical scenarios were analyzed to predict the critical velocity and smoke back-layering length in various sloping subway tunnels. Six different heat release rates including 5.58, 11.17, 16.67, 22.35, 27.94, and 33.52 kW were considered in the experiments and five different heat release rates including 2.79, 5.58, 8.38, 11.17 and 16.67 kW were considered in the simulations. Based on the comparison in the horizontal tunnel, numerical results were quite consistent with the experiments. The results showed that train blockage influenced the smoke back-layering length, and the critical velocity increases with the tunnel slope. Finally, empirical models were developed to predict the critical velocity and smoke back-layering length in a sloping subway tunnel with train blockage. [ABSTRACT FROM AUTHOR]

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With nearly 10 years of large-scale construction of Shanghai subway network, the drive of expo 2010, and also the pressing needs of space extension for urban regeneration and modernization, the exploitation of underground space in Shanghai has been greatly advanced. By the end of 2015, the total volume of underground space in Shanghai had reached 65 million square meters, and the per capita possession of the area of underground space is nearly 3.0 square meters. In the meanwhile, the safety issues during the use of underground space facilities are also increasingly prominent, not only because of the internal closure features that easily cause and spread disasters, but also the safety management and disaster prevention hardware that hide great danger. These problems have already been the important restriction factor in the comprehensive utilization of underground space resource in Shanghai. The authors and their team began to undertake the government-sponsored research projects of underground space safety issues in 2008, and by combining the literature research and empirical research during the following several years, the team made site surveys of more than 100 underground architectures in use. On the basis of this, the team used experts experience analysis and bowknot analysis methods to identify the causes and risks of the disasters and accidents, therefore refined and summed up the underground space safety evaluation index system. In order to achieve the quantitative evaluation, the team also made the evaluation criteria system according to the current law and technical standards, and used the AHP methods to build the weight system, and finally established the whole underground space safety evaluation system. The system has already been used for trial evaluation practice of several underground projects in Shanghai and provided effective basis for the improvement of the disaster control facilities and safety management of these projects. [ABSTRACT FROM AUTHOR]

The creation of sustainable infrastructure is increasingly being provided in underground facilities. In terms of construction and maintenance, this leads to greater challenges for construction, transport and energy-provider companies. This also applies for emergency services organisations as well as to ensure the safety for the users of the infrastructure. The project 'Research@ZaB - Zentrum am Berg' will establish an underground facility for research and development, education and training purposes. On the one hand, the centre should meet the requirements of public institutions; on the other hand it represents a 'development factory' for private companies as well as concerned universities. Untertägige Anlagen sind substanzielle Elemente der innerstädtischen sowie überregionalen Infrastruktur und des Energiewesens. Die Schaffung zukunftsfähiger Infrastrukturen erfolgt zunehmend in unterirdischen Anlagen, was gleichzeitig zu größeren Herausforderungen für die Bau-, Verkehrs- und Energieunternehmen, aber auch die Einsatzorganisationen hinsichtlich der Herstellung, der Erhaltung und Wartung sowie der Gewährleistung der Sicherheit für die Nutzer der Infrastrukturen führt. Mit dem Projekt 'Research@ZaB - Zentrum am Berg' wird eine für den Hohlraumbau fehlende Untertage-Einrichtung zu Forschungs-, Entwicklungs-, Schulungs- und Trainingszwecken errichtet, die einerseits die Anforderungen der öffentlichen Institutionen erfüllen soll, aber gleichzeitig eine 'Weiterentwicklungsfabrik' für private Unternehmen und für die zuständigen Universitäten darstellt. [ABSTRACT FROM AUTHOR]

The research study was intended to investigate the potential use of geothermal energy power plants in subsurface infrastructure such as tunnels and active or closed mines. The aims of the study was to examine the geological and geothermal conditions of a tunnel and a mine to survey the drilling technologies and necessary infrastructures for the drilling of deep boreholes as well as to determine rock, operating and process parameters and safety aspects in case of subsurface structures. The results are given in an evaluation matrix, which assembles the collected data and describes the specific boundary conditions of the tunnel projects and the mine as well as the risks of project Implementation. Das Forschungsprojekt untersuchte das Nutzungspotenzial von Tiefengeothermiekraftwerken für untertägige Infrastrukturen wie Tunnelbauwerke und aktive oder auch stillgelegte Bergbaustrukturen. Ziel des Projekts war, die geologischen und geothermischen Standortbedingungen an einem ausgewählten Tunnelbauwerk und einer aktiven untertägigen Bergbauanlage zu überprüfen, die Bohrtechnologien und die Bereitstellung der notwendigen Infrastrukturen zum Abteufen von Tiefenbohrungen zu erheben und auch Gebirgs-, Betriebs- und Prozessparameter und Sicherheitsaspekte zu erfassen, die sich im Spezialfall von Untertageanlagen ergeben. Die Ergebnisse fanden Eingang in eine Bewertungsmatrix, die sich aus den erhobenen Daten, welche die konkreten Randbedingungen der Projekte aufzeigen, sowie die Risiken einer Projektumsetzung beschreiben. [ABSTRACT FROM AUTHOR]

A leaking water pipe bursting high pressure water jet in the soil will create slurry erosion which will eventually erode the adjacent natural gas pipe, thus causing its failure. The standard 300 mm safety distance used to place natural gas pipe away from water pipeline facilities needs to be reviewed to consider accidental damage and provide safety cushion to the natural gas pipe. This paper presents a study on underground natural gas pipeline safety distance via experimental and numerical approaches. The pressure-distance characteristic curve obtained from this experimental study showed that the pressure was inversely proportional to the square of the separation distance. Experimental testing using water-to-water pipeline system environment was used to represent the worst case environment, and could be used as a guide to estimate appropriate safety distance. Dynamic pressures obtained from the experimental measurement and simulation prediction mutually agreed along the high-pressure water jetting path. From the experimental and simulation exercises, zero effect distance for water-to-water medium was obtained at an estimated horizontal distance at a minimum of 1500 mm, while for the water-to-sand medium, the distance was estimated at a minimum of 1200 mm. [ABSTRACT FROM AUTHOR]

Abstract: At present, underground urban metro construction accidents in China are rising with the rapid growth of urbanization and infrastructure investment. Real-time safety and risk management during urban metro construction has become extremely important but is very difficult, time-consuming and unreliable due to the lack of information and experienced managers. This paper presents the development and application of a web-based system for safety risk early warning in urban metro construction. A hybrid data fusion model based on multisource information (monitoring measurements, calculated predictions, and visual inspections) is employed to imitate human experts to give safety risk assessment and early warnings automatically. In addition, it has significantly improved information collection, sharing and communication by establishing a collaborative platform instead of traditional manual management. The system has been successfully applied to several metro construction projects and has perfected the safety management performance in the cities of Wuhan, Shenyang, Zhengzhou and Kunming in China. [Copyright &y& Elsevier]

Abstract: Safety accidents occur frequently in underground metro construction due to its complexity. These accidents cause huge losses because most metro construction is located in the center of very congested cities. Therefore, safety management is a priority in the metro construction industry. This paper proposes an approach for safety management using visualization technology. Safety is integrated with the construction management process throughout the project life cycle. Information from the design phase about construction components and scheduling has been gathered to formulate a 4 dimensional (4D) model. Before construction begins, a rule-based tool analyzes this combined information, automatically detects potentially unsafe activities and conditions and provides instructions for correction. More importantly, actual site monitoring data are continuously compared to the 4D model during the construction process. Therefore, the safety status of related components can be continuously visualized in the system as conditions change and potential safety risks evolve. This paper presents a prototype which was developed and verified with a case study of a real project. The results show that the proposed approach can be a tool of collaboration, virtual analysis and prediction for designers, site project managers, safety engineers and other participants. With real-time safety status visualized, it can detect safety risks before and during the construction process and then provide preventive measures. Thus, timely decisions can be made to avoid accidents. This contributes to the success of safety management in the metro construction industry. [Copyright &y& Elsevier]

Purpose. To study features of the displacement of enclosing strata for pilot testing of a new method of protection in the mine "Shcheglovskaya-glubokaya". Methodology. The methodological basis of the work is a comprehensive approach that includes a series of preliminary laboratory tests on physical models using the method of equivalent materials. A new method of ensuring the stability of development working through the use of rigid constructions with countervailing cavities. During the industrial test the method of field observations, proposed by members of Donetsk National Technical University has been used for recording of the spatial displacement of the tunnel contour in time. On the base of registered data the graphs of shifting of floor and ceiling of the tunnel were constructed for workings protected by means of usual methods and those where the new protection method had been tested, taking into account the distance to the stope. We have analyzed the rate of displacement of rocks enclosing the working, and constructed the cross sections of the workings in the reference grid at the distance of 50, 100 and 150 m from the stope. It is possible to establish the relative value of reduction of the displacement floor and ceiling of the tunnel protected by means of the proposed method in comparison with old methods. In the course of industrial tests the destruction of semi-blocks of support structures appeared. Therefore, it was held the next stage of research on measuring the pressure on support structures. Also, at this stage the material strength certificate for semi-blocks was drawn up. As a result, conclusions about ways of improvement of the proposed method for implementation in the mine "Shcheglovskaya- glubokaya" have been made. The solution consists in using more durable material for semi-blocks. Findings. In general, industrial tests were completed with positive results. Since the displacement of rocks of the floor in the tested section reduced by 30-40% compared with the control section and the displacement of the ceiling increased by 7%. The increase of ceiling displacement was caused by the insufficient strength of the material of semi-blocks. Originality. Provided that the ratio of the width of the cavity and the width of the protective structures is 1:1 and the ratio of the depth protective structure to its width is 2:1 the swelling in the working and the provocation of blowup in the fixing space were reduced. Practical value. An addition to the certificate on control and fixing the roof has been made and this allowed reducing the displacement of floor by 30-40%, with the expected economic effect of 238 UAH / m. [ABSTRACT FROM AUTHOR]

Abstract: Construction of underground structures (e.g., subway lines, railways and highway tunnels) is inherently hazardous, posing risks to both workers and machinery at the site and to surrounding buildings. The presence of groundwater may increase these risks. We develop a general probabilistic risk assessment (PRA) framework to quantify risks driven by groundwater to the safety of underground constructions. The proposed approach is fully compatible with standard PRA practices, employing well-developed risk analysis tools based on the fault tree analysis method. The novelty and computational challenges of the proposed approach stem from the reliance on a combination of approaches including extracting information from databases, solving stochastic differential equations, or relying on expert judgment to compute probabilities of basic events. The general framework is presented in a case study and used to estimate and minimize risks at a construction site of an underground station for a new subway line in the Barcelona metropolitan area. [Copyright &y& Elsevier]

Based on the geometric analysis of the relationship between the stress state at a point and the yield surface defined in the principal stress space, a coefficient ω is set up as an estimation index to describe the stress-induced yield risk. After yield, the equivalent plastic shear strains is usually used to characterize the failure degree (FD) of the material and adopted here as an index of the damage degree for the surrounding rock masses. Then, a unified variable combining ω and FD, named failure approaching index (FAI), is constructed to estimate the stability of rock mass which may be at different deformation stages. The formulas of FAI are derived for some popular yield criteria in geomechanics. Details for such development are addressed in the paper. Its rationality is verified by numerical simulation and comparative analysis of the conventional triaxial compression tests and typical tunnel projects. In addition, the method for applying FAI to the stability estimation of surrounding rock mass is proposed. As examples, the stability of the underground powerhouse, access tunnels and headrace tunnels at the Jinping II hydropower station are estimated by making use of the method we presented. The results indicate that not only is the index rational in mechanics, but the theory also has good expansibility, and the estimation methods are simple and practical as well. It is easier for field engineers to analyze and understand the numerical results. [ABSTRACT FROM AUTHOR]

The article presents an evaluation method for gathering displacement data in tunnelling. It states that displacement data are important in observational method particularly in adjusting construction method to the actual ground behavior and it serves a foundation for safety management. It mentions that evaluation method involves the introduction of a coordinate system and identification of the monitoring point position at the tunnel perimeter. It says that the whole displacement characteristic of a monitoring section can be assessed in a simple manner through a scatter plot of both displacement tendencies. It adds that the evaluation method allows the comparison of the displacement characteristic during representative normal behaviour in the actual circumstances.

The article discusses the construction of the ZaB-Zentrum am Berg, a research, development and seminar centre, in Erzberg, Syria, Austria. It mentions the move of the Austrian engineers in crafting a method that has significantly improved tunnel building. The consideration of the safety of the construction of underground facilities is also highlighted.

Reports that underground subways, malls, parking lots and public utilities are becoming more common in the world's biggest cities as a way of accommodating increasing populations. Claim by experts that the underground structures are not being designed to adequately resist the effects of natural disasters; Dangers posed to underground structures by fire and by floods,if the area cannot be sealed off and compartmentalized.