Underground Space Environment Research Articles

Lessons Learned from the COVID-19 Pandemic: A Multigroup Structural Equation Modelling of Underground Space Environment and Users’ Health

Due to the inherent limitations of underground spaces, such as the lack of natural ventilation and sunlight, underground space users tend to face more health risks compared with their aboveground counterparts. However, little is known about how the underground environment, users’ health, and their associations were impacted by the outbreak of the pandemic. In this study, we investigated and compared the impacts of the general underground environment on regular users’ physical and psychological health before and after the pandemic. To achieve this aim, the data from 525 surveys were collected from eleven underground sites, followed by an objective field measurement study conducted at five underground sites in Hong Kong pre- and post-outbreak of the pandemic. The multigroup structural equation modelling results indicated that: (i) surprisingly, the users’ satisfaction towards almost all underground environment factors, including greenery, connectivity with the aboveground environment, thermal comfort, ventilation, indoor air quality, acoustic comfort, and lighting, excluding wayfinding, were significantly higher in the post-outbreak period; (ii) the users’ health, both physical and psychological, was significantly better in the post-outbreak period; (iii) the impacts of visual comfort on the users’ physical and psychological health were significantly greater in the post-outbreak period (critical difference ratio (|CDR|) > 1.96); (iv) the impacts of wayfinding, greenery, and acoustic and thermal comfort on the users’ physical or psychological health were significant only in the pre-outbreak period (|CDR| > 1.96); (v) the impacts of connectivity on the users’ physical and psychological health were significant in both the pre- and post-outbreak periods (|CDR| < 1.96). The findings were further cross-validated using the objective measurement results. With an increasing need to develop healthy underground spaces, the study contributes to the development, design, and management of the underground environment to enhance the users’ health in the post-outbreak era.

Long-Term Urban Epidemic and Disaster Resilience: The Planning and Assessment of a Comprehensive Underground Resilience Core

This study utilizes the enclosed and stable environment of underground space for long-term sustainable planning for urban epidemics and disasters. Owing to the COVID-19 epidemic, cities require long-term epidemic–disaster management. Therefore, this study proposed a strategy for integrating multiple functions to plan a comprehensive Underground Resilience Core (URC). A planning and assessment methods of URC were proposed. With this methodology, epidemic- and disaster- URCs were integrated to construct a comprehensive-URC in underground spaces. The results show: (1) Epidemic-resilient URCs adopting a joint progressive approach with designated hospitals can rapidly suppress an epidemic outbreak. (2) The regularity of the morphology of underground spaces determines the area of the URC. Bar-shaped underground spaces have the potential for planning disaster-URCs. (3) The URC planning efficiency ranking is as follows: Bar shapes lead overall, T shapes are second under seismic resilience, and Cross shapes are second under epidemic resilience. (4) The potential analysis of planning a comprehensive-URC in the underground parking in Chinese cities showed that the recovery time can be advanced from 29% to 39% and the comprehensive resilience can be improved by 37.63%. The results of this study can serve as sustainable urban planning strategies and assessment tools for long-term epidemic–disaster management.

A Study on the Soundscape of Underground Commercial Space in Lu'an City and Hefei City, China.

Soundscape is an important part and one of the main factors of the underground space environment. Field surveys were conducted to evaluate the soundscape of underground commercial spaces and to compare it with the soundscape of the above-ground commercial spaces between two cities (Lu'an City and Hefei City) in China, consequently presenting the construction strategy of the soundscape of underground commercial spaces in urban areas. The results showed that the sound in the shopping center, which people found comfortable, was at the lower to intermediate level. The main sounds that people perceived as "general" sounds were environmental sounds such as music, the humming of the air conditioning, people talking, walking, and the hawking of the stores. Nevertheless, "very comfortable" sounds were background music and the sound of live performances, which were indicated in the majority of people's opinions on evaluating a comfortable feeling, thus reflecting the impact of the sound of mall music on people's cognitive psychology. Therefore, it is necessary to control the volume of environmental noise at a certain level so that people's health is not adversely affected. It also helps shoppers to feel more comfortable psychologically and physiologically.

Research on the Interaction between the Pile and Shield Machine in the Process of Cutting a Reinforced Concrete Pile Foundation

As the urban underground space environment gets more complex, the cases of shield machines encountering and cutting through piles are becoming more common. The interaction between the cutter head and pile foundation directly affects the tunneling performance of the shield machine and the safety of the existing structure. To study the interaction between the pile and the shield machine, a calculation model of the interaction force is established. A field test of cutting two piles was conducted and the rationality of the model is verified by comparing the calculation results with field test data. The model is applied in the project of a shield machine cutting bridge piles in Harbin Metro Line 3, China. The shield operation parameters are predicted and compared with field test results. Besides, the impacts of cutting surface width and eccentric distance on interaction force are discussed. The study shows that there is a significant interaction between the cutter head and the piles when the shield machine cuts reinforced concrete piles, which causes obvious changes in the shield operation parameters and shield performance. The number of tools that are inside the cutting area has a significant effect on the additional torque. The additional torque fluctuates with the rotation of cutter head and increases with the increase of the number of tools. The number of these tools is determined by factors such as the layout of tools in the cutter head, cutting surface width and eccentric distance, which influence the position of each tool relative to the cutting area. As the cutting distance increase, the additional torque of the cutter head shows a trend of first increasing and then decreasing and reaches the maximum value when the cutting distance reaches the radius of the pile. Besides, the additional force and additional moment of the cutter head increase with the increase of the cutting surface width. The impacts of eccentric distance on additional force and additional moment are complicated. The results in this paper can provide reference for similar engineering.

Study on Prediction Method of Infrasound Waves for Concrete Structure Destruction in Underground Space

To study the characteristics of infrasonic wave response during the failure process of concrete samples and analyze the feasibility of infrasonic wave prediction for the failure of concrete structures in underground spaces, rock mechanics loading devices and infrasonic wave acquisition devices were used to carry out infrasonic wave test experiments on concrete samples during uniaxial loading. With the help of MATLAB numerical simulation software, the test results are processed and analyzed by constructing band-pass filtering program, wavelet denoising program and time–frequency analysis program. The analysis results show that: there is infrasound wave during the loading process of the concrete sample; During the loading process, the change of infrasonic wave presents stage characteristics, which can be divided into three stages: the initial stage when a certain amount of infrasonic events occur, the middle stage when there are few infrasonic events and the later stage when infrasonic events increase rapidly and reach a peak. These stages respectively correspond to the compaction deformation stage, elastic deformation stage, plastic deformation and later stage of concrete sample deformation, and there is a good corresponding relationship between them. When the concrete sample is damaged by the peak value, the frequency and amplitude of the infrasound wave have abnormal changes. Therefore, in the early stage of the failure of the concrete structure, when the local failure occurs, there is also an abnormal response of infrasonic wave and the failure of the concrete structure can be predicted based on the abnormal change. At the same time, the infrasound wave, as a kind of low-frequency wave, has the advantages of long propagation distance, small attenuation and flexible position arrangement and has stronger adaptability to the complex underground space environment. It is of great significance to improve the accuracy of underground space concrete structure failure prediction.

Greening Design of Urban Semi-underground Space

Urban space greening is of great significance for improving urban underground space environment. At present, the design of urban underground space in China mostly involves the design of underground space. However, very rare research has been conducted on the design of semi-underground space greening to date. Through case study and survey research, this study focuses on the design of domestic semi-underground space, the preliminary semi-underground space greening design scheme, and the concrete implementation process of the semi-underground public space green wall greening design. The current study employs the green wall project in a semi-underground space environment as an example to illustrate the application of greening design in urban semi-underground space, and provide guidance for future ecological design of semiunderground public space.

Oxidative Stress From Exposure to the Underground Space Environment.

There are a growing number of people entering underground spaces. However, underground spaces have unique environmental characteristics, and little is known about their effects on human health. It is crucial to elucidate the effects of the underground space environment on the health of humans and other organisms. This paper reviews the effects of hypoxia, toxic atmospheric particles, and low background radiation in the underground space environment on living organisms from the perspective of oxidative stress. Most studies have revealed that living organisms maintained in underground space environments exhibit obvious oxidative stress, which manifests as changes in oxidants, antioxidant enzyme activity, genetic damage, and even disease status. However, there are few relevant studies, and the pathophysiological mechanisms have not been fully elucidated. There remains an urgent need to focus on the biological effects of other underground environmental factors on humans and other organisms as well as the underlying mechanisms. In addition, based on biological research, exploring means to protect humans and living organisms in underground environments is also essential.

Integrated design for underground space environment control of subway stations with atriums using piston ventilation

In subway stations, the piston effect plays an important role in enhancing ventilation to improve subway environment and reduce energy consumption. However, it may induce negative impacts on environmental health and thermal comfort, i.e. air pollution and strong wind. Traditionally, the architecture and ventilation systems are designed separately, and normal ventilation design follows architectural layout. Actually, the architecture design can have a significant influence on the ventilation performance, e.g. airflow pattern. Therefore, this study aims to integrate the design pattern of the architecture with an appropriate ventilation system. A typical subway station of Nanjing (in China) was considered. A dynamic-mesh based computational fluid dynamics (CFD) method was adopted to simulate ventilation performance in the presence of piston effect. Field measurements were conducted to validate the numerical method. New measures were proposed from the perspectives of architectural design to improve the ventilation effect, including enlarging atrium space, adding atrium vents and funnel-shaped exits, etc. The numerical results show that the optimal architectural design could provide a significant improvement towards the airflow environment and ventilation efficiency while avoiding serious air pollution. The proposed integrated-design pattern could further facilitate the creation of an ‘energy-saving’ and ‘healthy’ underground space environment.

Research on the Directionality of Difference Frequency Sound Field Based on Circular Ultrasonic Array

In a closed environment of underground space, noise pollution is serious, and sound waves are required to have strong directionality, providing people with a relatively independent and quiet working space. In order to obtain a high directivity sound source, a method combining difference frequency sound field with the circular array of transducers is proposed. Firstly, the advantage and disadvantage of the sound field generated by difference frequency mode and the sound field radiated by direct vibration in conventional mode are demonstrated. Secondly, based on the principle of sound field radiation, the directivity function of differential frequency sound field of circular piston transducer with multi-circumference arrays is derived. Finally, the influence parameters of directivity of differential frequency sound field are determined by three-dimensional and two-dimensional directivity diagrams, which can provide reference for the design of acoustic directional transducer array.

A Framework for Assessment of the Influence of China’s Urban Underground Space Developments on the Urban Microclimate

The paper aims to establish the framework for linking underground space projects and the urban microclimate, in order to construct an interdisciplinary research framework. Based on the combination of underground space, urban form and the urban microclimate, the impacts of underground space on urban microclimate factors above ground and underground are summarized and the internal mechanism is investigated. The above ground factor refers to the impact of a new urban form induced by the underground space planning on the urban microclimate. The underground factor refers to the impact of the control of the internal environment of underground space on the ground environment. This study mainly addresses two aspects. Firstly, to identify the influencing factors of urban underground space microclimate and define the research entry point and classify the indicator of the external space environment; secondly, to address the key issues of the research areas and their influence on the urban underground space project and the urban microclimate in the current phase and establish the direction of future research. The microclimate case of the Nanjing underground planning is provided to preliminarily analyze how underground space development improves the urban microclimate. By the comparative analysis of microclimate parameters, air quality parameters, and outdoor thermal environment parameters (Mean Radiant Temperature, MRT), the influences and benefits of underground space projects on the urban microclimate is quantitatively explored.

Rampway 설치 석회석 광산내 환기 현황 및 열환경 분석 사례연구

As more diesel engines have been employed in underground limestone mines with large cross section, underground space environment is worsened by diesel exhausts and heat flow. This paper aims for the ultimate goal to optimize the work place environment through assuring the optimal required ventilation rate based on the analysis of the airflow, diesel exhaust gas concentrations and the effects of mechanization and deepening working face on temperature and humidity. Due to the insufficient capacity of the main exhaust fan and poor airway management, stagnant airflows were observed at various locations, while the flow direction was reversed instantly with passing diesel equipment and the flow reversal was also made by the seasonal variation of the outside surface weather. During the loading operation, CO concentration measurements were found to be frequently higher than the threshold limit of 50 ppm, and most of the measurements during drilling and loading operations shows even more serious levels surpassing the permissible limit of 3 ppm. The actual ventilation quantity was considerably less than the required quantity estimated by the mine health and safety law, and this shortage problem was less serious in colder winter showing more effectiveness of the natural ventilation.

Method of Study on Drilling Parameter of Strata Obtained by Photoelectric Encoder

According to complex geological environment of underground space，drilling parameters were obtained based on the research of drilling process. As a sensor for collecting the date of drilling parameter, photoelectric encoder was chosen to combine field test. The change curve of drilling depth with torque in different strata was collected successfully by using photoelectric encoder and can reflect the change of torque during drilling. It is found that there are different response characteristics in different strata, but these response characteristics show the certain orderliness.

The urban underground space environment and human performance

The development of modern science and technology has been accompanied by a great migration of people to the cities. This population influx has, in turn, magnified urban problems related to population, environment, traffic, land and energy. Scientific and technical workers engaged in studying the best means of solving these problems have found that a good deal of knowledge can be gained from the exploitation and use of underground space. It has been proven through practice that the comprehensive exploitation and utilization of three-dimensional urban space—surface, underground and sky—can cure a number of urban problems. This paper presents the authors' research and conclusions in the field of underground space use in Shanghai (P.R.C.), addressing characteristics of the underground space environment and the effects of this environment on human psychology, physiology, work efficiency and health. Le développement de la science et des technologies a été accompagné par une grande migration de la population vers les villes. Cet influx de population a, à son tour, accru les problèmes urbains liés à la population, à l'environnement, au traffic, au sol et à l'énergie. Des techniciens et des scientifiques qui étudient ces problèmes ont trouvé qu'il existe de grandes possibilités dans l'exploitation et l'utilisation de l'espace sous terre. L'expérience a été déja prouvé qu'une utilisation et une exploitation approfondies de l'espace urbain sous terrain peut aider à résoudre beaucoup de problèmes d'urbanisation. Cet article présente la recherche des auteurs et les conclusions pour l'utilisation de l'espace sous terrain de Shanghai (R.P.C.) en ce qui concerne les caractéristiques de l'environnment sous terre et les effets de cet environnement sur la psychologie humaine, l'efficacité au travail et la santé.