Bibliometric analysis of research challenges and trends in urban underground space

The utilization and development of urban underground space play a crucial role in optimizing the layout of civic architecture and enhancing the urban ecological environment,which contributes toward increasing the overall carrying capacity and promoting sustainable development in megacities.To delve into the research progress of urban underground space,knowledge maps were created using the information visualization software VOSviewer.The literature was systematically extracted from three prominent databases,namely,Web of Science,Scopus,and China National Knowledge Infrastructure.According to the bibliometric analysis of the co-citation and core words co-occurrence,the trends and challenges of research on urban underground space were identified.As highlighted by the results obtained,it still remains highly challenging to achieve interdisciplinary collaboration in urban underground space research;the research trends of urban underground space consist of collaborative planning and whole life cycle sustainable development,multisource geological data informatization and resource evaluation,infrastructure design optimization,and intelligent construction.The knowledge map,drawn using bibliometric methods,offers a quantitative analysis of literature retrieval across various levels.It is recognized as an essential tool for exploring and identifying challenges and trends in urban underground space.

Critical rainfall intensity for safe evacuation from underground spaces with flood prevention measures

Underground space in urban areas has been expanding rapidly during recent decades, and so has the incidence of fatal accidents and extensive damage to facilities resulting from underground flooding. To evaluate the safe evacuation potential of individual underground spaces in flood-prone urban areas, the hydraulic effects of flood prevention measures, e.g., stacked flashboards or sandbags and elevated steps, were incorporated in a proposed formula for estimating the depth of inundation of an underground floor. A mathematical expression of the critical rainfall intensity for safe evacuation from underground space was established and then evaluated for two types of underground spaces, an underground shopping mall and a building basement. The results show that the critical rainfall intensity for any individual underground space can be determined easily using the proposed analytical or graphical solution. However, traditional underground flood prevention measures cannot improve safety if people refuse to evacuate immediately once water intrudes into the underground space.

Influence of underground space development mode on the groundwater flow field in Xiong’an new area

The degree and scale of underground space development are growing with the continuous advancement of urbanization in China.The lack of research on the change of the groundwater flow field before and after the development of underground space has led to various problems in the process of underground space development and operation.This paper took the key development zone of the Xiong’an New Area as the study area,and used the Groundwater modeling system software(GMS)to analyse the influence on the groundwater flow field under the point,line,and surface development modes.The main results showed that the underground space development would lead to the expansion and deepening of the cone of depression in the aquifer.The groundwater level on the upstream face of the underground structure would rise,while the water level on the downstream face would drop.The“line”concurrent development has the least impact on the groundwater flow field,and the maximum rise of water level on the upstream side of the underground structure is expected to be approximately 3.05 m.The“surface”development has the greatest impact on the groundwater flow field,and the maximum rise of water level is expected to be 7.17 m.

Development of urban underground space in coastal cities in China:A review

The development of urban underground space is a critical way to alleviate the lack of urban resources,and improve environmental conditions as well as residents'quality of life,which has important practical significance.As the most densely populated and economically developed areas,coastal cities face many challenges in underground space development owing to their unique environmental geological conditions.This study examined the current situation of underground space development,academic research,technology application,evaluation methods,planning,and legislation in coastal cities in China.On this basis,it analyzed the future development trends,and presented reasonable suggestions for the critical scientific and technical problems faced by the development of underground space in coastal cities.The key suggestions are as follows:it is necessary to define and clarify the critical geological issues,distributions,and hazards that affect underground space development and major engineering construction in coastal cities;the land-sea integrated detection technology for sea crossing bridges and submarine tunnels needs to be studied;in evaluating the suitability of underground space in coastal cities,the land and sea area evaluation factors should be integrated;and the evaluation system of landsea integration needs to be established.

An experimental study on fire characteristics of urban complex underground space based on BIM

Compared with the space on the ground,if there is a fire in the urban complex underground space,the loss will be greatly harmful.In addition,the complex underground space is usually connected with other large space areas and densely populated.Once a fire occurs in the complex underground space,it will cause huge property losses and casualties.In order to reduce the risk of fire,it is necessary to deeply understand the development rules and characteristics of fire in the complex underground space of the city.This article has mainly carried on the following work:(I)A particularly complex model of the multi‐storey subway station was built.On this basis,three groups of comparative experiments were conducted to study the effects of fire power,fire location and smoke control system on fire development,and the conclusion that fire location is the most important factor for fire development was obtained;(II)In order to explore the entire space fire and the local space fire,CFD(Computational Fluid Dynamics)is used to build a large‐size fire model and a small‐size fire model respectively;(III)Multiple detector data as temperature slices were built,and it is expected to make full use of the simulation data to deduce the important index of fire location in the early stage of fire.All of the works in this paper will provide reference experimental data for the prevention and firefighting of a sudden fire in the complex underground space.

Intelligent Oxygen-Enriched and “Sterilized” Underground Gyms: Background, Dilemmas and Pathways

The in-depth integration of healthy China with national fitness and the hope to achieve the long-term goal of “leading Sports Nation” by 2035, can’t be realized without gyms where people do physical exercise. The international academic community recognizes that the 21st century is the golden time for sustainable and quality development. Taking a national perspective, authors of this paper studied the feasibility of building underground gyms in China through the approach of interdisciplinary research, as well as its dilemmas and pathways, and found out that quality development of underground space can effectively address challenges for large cities in China by increasing the resilience of urban area, and give full engage to underground capacity in striving for the goal of carbon peak and carbon neutrality. Underground gyms can also be incorporated into resident’s 15-min fitness circle, satisfying people’s needs of doing exercise at any time and in an easily-accessible place. However, China’s underground area development has been hindered by unclear property rights, chaotic action and utilization, and relatively backward laws and regulations. Moreover, building underground gyms still has to solve many problems such as poor air quality, severe sweat smell, and excessive bacteria and viruses. It is suggested that the capable authorities shall first clarify laws and regulations over place compound utilization, property rights and fire protection to facilitate the process of building underground gyms;encourage fitness practitioners to explore underground areas as gyms, and transfer their ground business to underground;then produce an intelligent and systematic solution of air quality improvement featuring oxygen-enrichment and “sterilization” with integration, a variety of instruments to monitor air quality of indoor gyms in real-time, to realize automatic control and management, and truly create worry-free and oxygen-enriched underground gyms with no sweat smell and no fear of bacteria and viruses.

Design Strategy of Underground Space of Urban Rail Transit Complex Based on Integration Concept

With the accelerated development and utilization of urban underground space,the underground space design of complex based on rail transit has attracted much attention.By sorting out the integration concept and constructing the logical framework of integrated design,the integrated design strategy is proposed from the aspects of function,transportation,space and environment on the urban scale,and the evaluation points of integrated design effect are put forward from the aspects of accessibility,coordination,openness and symbolism.

Planning and construction of Xiong’an New Area(city of over 5 million people):Contributions of China’s geologists and urban geology

China established Xiong’an New Area in Hebei Province in 2017,which is planned to accommodate about 5 million people,aiming to relieve Beijing City of the functions non-essential to its role as China’s capital and to expedite the coordinated development of the Beijing-Tianjin-Hebei region.From 2017 to 2021,the China Geological Survey(CGS)took the lead in multi-factor urban geological surveys involving space,resources,environments,and disasters according to the general requirements of“global vision,international standards,distinctive Chinese features,and future-oriented goals”in Xiong’an New Area,identifying the engineering geologic conditions and geologic environmental challenges of this area.The achievements also include a 3D engineering geological structure model for the whole area,along with“one city proper and five clusters”,insights into the ecology and the background endowment of natural resources like land,geothermal resources,groundwater,and wetland of the area before engineering construction,a comprehensive monitoring network of resources and environments in the area,and the“Transparent Xiong’an”geological information platform that is open,shared,dynamically updated,and three-dimensionally visualized.China’s geologists and urban geology have played a significant role in the urban planning and construction of Xiong’an New Area,providing whole-process geological solutions for urban planning,construction,operation and management.The future urban construction of Xiong’an New Area will necessitate the theoretical and technical support of earth system science(ESS)from various aspects,and the purpose is to enhance the resilience of the new type of city and to provide support for the green,low-carbon,and sustainable development of this area.

Evaluation of urban underground space resources using a negative list method: Taking Xi'an City as an example in China

Utilization of urban underground space has become a vital approach to alleviate the strain on urban land resources,and to optimize the structure and pattem of the city.It is also very important to improve the city environment,build livable city and increase the capacity of the city.Based on the analysis of existing evaluation methods and their problems,a method for evaluating underground space resources based on a negative list of adverse factors affecting underground space development is proposed,to be primarily used in urban planning stages.A list of the adverse factors is established,including limiting factors,constraining factors and influencing factors.Taking Xi'an as an example,using a geographical information system platform,a negative list of adverse factors for the underground space resources in Xi'an City are evaluated,and preventive measures are proposed.Natural resources,exploitable resources,and the potential growth of exploitable underground space resources are evaluated.Underground space assessment in the different development stages of the city,collaborative utilization and safety evaluation for multiple subsurface resources,environmental impact and assessment,as well as evaluation methods based on big data and intelligent optimization algorithms are all discussed with the aim of serving city planning and construction.

Underground Space Landscape Design of Business Zone B of Shanghai World Expo

Business Zone B of Shanghai World Expo is the dynamic cluster area of well-known enterprise headquarters,and it has created the scheme layout of integrated design above and below ground according to regional planning characteristics and the characteristics of the times.The underground space landscape design of Business Zone B of Shanghai World Expo is a typical case of underground space development in China,and the summary of design strategy is helpful for improving underground space landscape design level in China.The existing problems in landscape design of Business Zone B of Shanghai World Expo are found through fi eld investigation,and the law of underground space landscape design in Business Zone B is summarized.Due to the fact that the development of underground space can not be reversed,the optimization design strategy of underground space landscape,such as strengthening the connectivity of underground space,enriching the sunken square and courtyard,and creating good physical environment of underground space,is put forward to improve the status quo of underground space environment.The construction level of underground space landscape in China has been constantly improving.As long as the urban planning is reasonable and pays attention to the application of integrated design of ground and underground,architectural technology and art combination in underground space environment,the construction of urban underground space landscape will become more ecological,humanized and diversifi ed.

Status Quo and Problems of Underground Space Researches

With the intensifying urbanization and the increasing demands for land resources, urban development is gradually expanding into the underground. Rational development and design of underground space can not only improve use efficiency of land, relieve land use pressure, but also facilitate people's living and improve urban environment. Analysis of the status quo and problems of underground space design researches in China, and the directions of future underground space research and development will contribute to the development and design of underground space. On the basis of reviewing research papers in the past decades, the contents of underground space researches were divided into 10 major categories, the current contents of underground space researches in China and existing problems were analyzed, and it was proposed that the future underground space design researches should be based on traditional research contents and methods, use advanced technologies such as information technology, show the interdisciplinary cooperation, pay attention to human feelings, protection and continuation of cultural context, and adhere to green and sustainable development with consistent innovation and progress.

Exploration and Practice of Underground Space Design Guided by Green Idea in China

With the continuous deterioration of living environment, green building has become the development trend of architecture, however, usage of urban land is saturated with the development of the city. Thus, the development of underground space has attracted more and more attention, and it is of great significance to introduce green idea into the design of underground space in China. This paper is dedicated to research the exploration and development of green idea in design of underground space in China which can be divided into three stages: budding stage, exploration stage and rapid development stage. To realize ecological green space and sustainable development, diversifi ed and systematic development of green idea in design of underground space is an inevitable trend in China.

The characteristics of DC electric field in the whole underground space

The mine direct current method is more and more popular in the practical application.The study of the response characteristics of the underground full space direct current electric field has certain guiding significance for the practical application.In this paper,through numerical simulation,the potential characteristics of different abnormal body distribution are studied,and the potential characteristic curves under various models are summarized.This paper also makes a specific study on the existence of the roadway,and analyzes the influence of the roadway on the characteristics of abnormal body potential.The results show that the potential response curve of DC method can well reflect the position of abnormal body,while the vertical accuracy of electrical method data is reduced when there is tunnel influence.The above research enriches the DC exploration theory of the mine and provides guidance for the DC exploration of the whole underground space.

A Hygienic Survey of the Environment of Underground Space and Buildings

Full utilization of underground space and buildings could have positive economic and social effects. However, the microclimate and air quality must be well controlled so that they are not harmful to human health. This survey indicated that relative humidity is a common hygienic problem in underground space and buildings. Attention should be paid to humidity control and to the strengthening of routine ventilation at the construction stage. Carbon dioxide can be used as a hygiene index of air pollution; the sanitary standard for it in the air of underground buildings is 10%. The hygienic survey shows that the concentration of carbon dioxide is usually below this standard in the environments of underground space and buildings. (c)1989 Academic Press,Inc.

Exploring the frontiers of deep underground sciences and engineering—China Yunlong Lake Laboratory is striving to be the best

This paper introduces the establishment of deep underground infrastructure for science and engineering research.First,the representative deep underground research laboratories and facilities in the world and their functions were summarized and reviewed.Then,the plan and service target of China Yulong Lake Laboratory were proposed for the storage of resources and energy,as well as the sealing of hazardous waste in deep underground space.On this basis,this paper reveals how the facility addresses its key scientific issue on“The law of fluid matter migration in deep underground space”and engineering significance.Finally,the construction progress of the facility components was demonstrated in details.As is hoped,this paper would provide useful reference to the deep underground research community;meanwhile,international collaboration on deep underground research is highly welcome.

Analysis of Geotechnical Engineering Safety Technology in Urban Underground Space Construction

With the accelerating pace of urbanization,the development and application of urban underground space has attracted much attention.In the construction of urban underground space,geotechnical engineering safety is the key point for construction.Based on this,this paper analyzes the application of geotechnical engineering safety technology in urban underground space construction,in hope that this analysis can provide a scientific reference for the rational application of geotechnical engineering safety technology as well as the construction and development of urban underground space.

Study on the Current Situation of Urban Integration of Aboveground Space and Underground Space:Under the Background of China’s Land Spatial Planning

Urban underground public space has a synergistic effect with its surrounding urban aboveground functions or facilities,which reflects the complementarity between underground functions and urban functions.The research analyses the degree of integration through the case study of urban aboveground space and underground space in China.The research method of this paper will give different evaluation criteria to public transport and public space and the influencing factors of space integration.The indicators of public transport include the number of subway lines and underground parking spaces.The evaluation standard of public space is the area of underground space and the number of floors of underground space.The subway entrance and exits are selected as the evaluation index for the aboveground and underground transition space.Through the specific analysis of 7 selected cases,it provides arguments for the research.The average rent in the case is taken as the dependent variable.Through the regression model,the influencing factors of the integration of aboveground and underground space are determined.The purpose of the study is to explore the influencing factors of the integration of aboveground space and underground space,and how to optimize the integration of aboveground and underground space.

Uniaxial compressive behaviour of a FRP standing support made of mine wastes

Twenty-seven specimens were tested to investigate the uniaxial compression behaviour of an innovative standing support for underground space applications.The innovative standing support consisted of an external fibre reinforced polymer(FRP)jacket and the infill column made of cementitious grout,tailings and coal wash rejects.Effects of the FRP layers number and water to the cementitious grout(w/g)ratio were evaluated.Test results indicated that lower w/g ratios produced stronger infill columns.With FRP confinement,the standing support demonstrated strain-hardening loading characteristics with a significant improvement in both strength and ductility.The highest strength and strain of the specimens achieved was 58.4 MPa and 11.8%respectively.Compared with the unconfined specimens,the confinement with four FRP layers increased the specimen strength and associated strain up to 3.6 and 27.0 times respectively.A correlation between the compressive strength of the infill material and the ultrasonic pulse velocity was also investigated.Furthermore,a simple design-oriented model was proposed to predict the peak strength and the corresponding strain of the innovative standing support.

Utilizing semantic-level computer vision for fracture trace characterization of hard rock pillars in underground space

This study utilizes a semantic-level computer vision-based detection to characterize fracture traces of hard rock pillars in underground space.The trace images captured by photogrammetry are used to establish the database for training two convolutional neural network(CNN)-based models,i.e.,U-Net(University of Freiburg,Germany)and DeepLabV3+(Google,USA)models.Chain code technology,polyline approximation algorithm,and the circular window scanning approach are combined to quantify the main characteristics of fracture traces on flat and uneven surfaces,including trace length,dip angle,density,and intensity.The extraction results indicate that the CNN-based models have better performances than the edge detection methods-based Canny and Sobel operators for extracting the trace and reducing noise,especially the DeepLabV3+model.Furthermore,the quantization results further prove the reliability of extracting the fracture trace.As a result,a case study with two types of traces(i.e.,on flat and uneven surfaces)demonstrates that the applied semantic-level computer vision detection is an accurate and efficient approach for characterizing the fracture trace of hard rock pillars.

A pilot project of ambient noise tomography on a dense seismic array in Ji'nan urban area

In this study, we conducted ambient noise tomography(ANT), with 33-day data, to investigate the nearsurface shear-velocity structure in downtown Ji’nan, Shandong Province, China. The cross-correlation functions with quiet clear Rayleigh waves are obtained with more symmetrical energy distribution which indicates that strong human activities, such as moving vehicles and municipal engineering construction, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surfacewave tomographic method with period-dependent ray-tracing is used to invert all surface-wave dispersion data in the period band 0.2–1.5 s simultaneously for 3D variations of shear-velocity structure. The study result can help us better understand the local geologic structures, evaluate the distribution and geometry of the fracture-karst media, and assess hazards of the concealed active fault and its effect on the springs in the future.