Development Of Urban Underground Space Research Articles

Generating Topologically Consistent BIM Models of Utility Tunnels from Point Clouds.

The development and utilization of urban underground space is an important way to solve the "great urban disease". As one of the most important types of urban underground foundations, utility tunnels have become increasingly popular in municipal construction. The investigation of utility tunnels is a general task and three-dimensional laser scanning technology has played a significant role in surveying and data acquisition. However, three-dimensional laser scanning technology suffers from noise and occlusion in narrow congested utility tunnel spaces, and the acquired point clouds are imperfect; hence, errors and redundancies are introduced in the extracted geometric elements. The topology of reconstructed BIM objects cannot be ensured. Therefore, in this study, a hierarchical segmentation method for point clouds and a topology reconstruction method for building information model (BIM) objects in utility tunnels are proposed. The point cloud is segmented into facades, planes, and pipelines hierarchically. An improved mean-shift algorithm is proposed to extract wall line features and a local symmetry-based medial axis extraction algorithm is proposed to extract pipelines from point clouds. A topology reconstruction method that searches for the neighbor information of wall and pipeline centerlines and establishes collinear, perpendicular, and intersecting situations is used to reconstruct a topologically consistent 3D model of a utility tunnel. An experiment on the Guangzhou's Nansha District dataset successfully reconstructed 24 BIM wall objects and 12 pipelines within the utility tunnel, verifying the efficiency of the method.

Research on Geological Safety Evaluation Index Systems and Methods for Assessing Underground Space in Coastal Bedrock Cities Based on a Back-Propagation Neural Network Comprehensive Evaluation–Analytic Hierarchy Process (BPCE-AHP)

With the rapid development of the economy in China, the scale and quantity of urban underground space development continue to grow rapidly; as such, geological safety problems in urban underground space development and utilization are a research hotspot at present. Therefore, it is important to establish a high-quality evaluation index system and method for assessing the geological safety of urban underground spaces in coastal bedrock. Taking the typical area of Qingdao as an example, this study establishes an effective system for evaluating the geological safety of urban underground space according to the geological background, hydrogeology, engineering geology, and unfavorable geological phenomena in the Hongdao Economic Zone of Qingdao. Then, the method of evaluating the geological safety of urban underground space was studied. Through a comprehensive analysis and comparison of the fuzzy comprehensive evaluation–analytic hierarchy process (FCE-AHP), the grey relation comprehensive evaluation–analytic hierarchy process (GRCE-AHP), the matter-element comprehensive evaluation–analytic hierarchy process (MECE-AHP), and the back-propagation neural network comprehensive evaluation–analytic hierarchy process (BPCE-AHP), it was determined that the back-propagation neural network comprehensive evaluation–analytic hierarchy process (BPCE-AHP) was an ideal method for evaluating the geological safety of underground space in Qingdao’s coastal bedrock area. This method was used to evaluate the geological safety of the study area, and the evaluation results were verified; this further proved the practicability and rationality of the back-propagation neural network comprehensive evaluation–analytic hierarchy process (BPCE-AHP).

An Investment Decision Model for Underground Urban Utility Tunnel Based on MIVES and Real Option Theory from a Sustainable Perspective

Although the importance of urbanization, urban renewal and sustainable development have been increasingly recognized, with the accelerating process of urbanization, the urban above-ground space is no longer sufficient for the process of urbanization, and downward development of the city has become inevitable. Underground Urban Utility Tunnel (UUUT) is an effective measure to promote the sustainable development of urban underground space (UUS). However, decision makers still cannot fully consider the economic, social, environmental and technological factors, as well as the future risks of the project and the value of flexibility in management. In this paper, an investment decision model for UUUT is proposed that combines the Integrated Value Model for Sustainable Assessment (MIVES) and the real option theory, which comprehensively considers the social, economic, environmental and technological impacts, and assists the government in carrying out the investment decision analysis of UUUT from a sustainability perspective by applying the real option theory to the economic evaluation process. The primary process of this study can be divided into four steps. (1) establishment of the investment decision index system for UUUT; (2) determination of the quantitative criteria for each indicator; (3) calculation of the feasibility of UUUT; and (4) a case study to demonstrate the feasibility of the proposed model, as well as the achieved results. The proposed investment decision model can be used as an auxiliary tool in the early planning stage of UUUT, and also for the comparison and selection of different options for UUUT.

A Comprehensive Study of the Suitability of Urban Underground Spaces for Connection Development: A Case Study of the Erhai Lake Basin, China

Urban underground space (UUS) involves multiple stakeholders whose concerns span the entire life cycle of underground space. The government pays more attention to the social benefits of UUS to the region, developers pay more attention to the economic benefits brought by the development of UUS, and users pay more attention to the comfort level of UUS operation. This study used the analytic Hierarchy Process (AHP), government, developers, and users to construct a comprehensive evaluation index system of underground space development needs. Different from previous studies, considering the need for future connectivity development in the UUS circle, this paper proposes to comprehensively consider the impact of connectivity development on regional suitability through coupled AHP and cellular automata (CA). The results show that about 102.67 km2 (13.03%) underground area of Erhai Lake Basin is suitable for underground space development. Compared with the traditional evaluation method, the evaluation result of about 31.41 km2 (3.99%) area was improved, and the fragmentation problem between blocks was improved. This method is of great value to the comprehensive development of UUS in the Erhai Lake Basin and is helping to improve future underground space planning.

Using digital technologies to plan and manage the pipelines network in city

AbstractPromoting the intelligent level of urban pipelines network planning and management is an important way to improve the rational development and utilisation of urban underground space and ensure the safe operation of urban infrastructure systems. The research on using the rapid and visual expression technology of 3D pipelines network model data, which has the functions of techno‐economic indexes calculation and automatic comparison of underground pipeline construction projects, effectively avoids possible errors in manual calculation and comparison and improves the efficiency and accuracy of the digital declaration process for project planning. In the 3D Geographic Information Systems (GIS) platform environment, this research help to develop many analysis and approval functions based on the data of the underground pipelines network model and the integrated pipes gallery Building Information Modelling, such as evaluating the compliance, feasibility and scientific of the planning scheme of the underground pipeline construction project, comparing the completion data with the data approved by the administrative departments of the project, evaluating the consistency of them and judging the compliance of the project completion data. The application results of some actual projects cases show that this research can improve the efficiency of planning declaration and approval analysis.

Evaluation of the Development Potential of Urban Underground Space Using Set Pair Analysis and the Comprehensive Weight Method

Recently, a series of urban diseases have seriously impacted the development of large and medium cities. The development of urban underground space (UUS) is widely regarded as an effective solution. Due to the irreversibility of underground space resources, it is important to formulate scientific and reasonable development planning based on evaluation of the development potential of urban underground space (DPUUS). In this work, from the perspective of society, economy, and environment, an evaluation model of the DPUUS was established, and nine indexes were selected, including population density, vehicle possessive quantity per 100 capita, policy support, GDP per capita, GDP per km2, land price, geographical position, geological conditions, and natural disasters. The comprehensive weight method (CWM) combined with subjective and objective weights was used to determine the final weight of the evaluation index. Set pair analysis (SPA) and the credible degree recognition criterion (CDRC) were applied to determine the DPUUS grade of each city, which can provide a new idea for DPUUS.

A Review of Efficient and Low-Carbon Pile Technologies for Extra-Thick Soft Strata

With the development of urban underground space and increased infrastructure functions, both the scale of engineering construction and engineering difficulties have increased globally. In the construction of structures in soft strata, especially in coastal areas, the limited bearing capacity of the foundations poses a significant challenge. The composite pile technologies employing an organic combination of the rigid pile andthe flexible column can enable efficient soft ground treatment. In light of prominent global environmental issues, low-carbon energy-saving curing technologies have been rapidly developed for application in geotechnical engineering. This paper discusses progress in research on the mechanical properties of the efficient and low-carbon pile technologies, including the stiffened deep mixing (SDM) column, squeezed branch pile, pre-bored grouting plated nodular (PGPN) pile, precast cement pile reinforced by cemented soil with a variable section (PCCV), and carbonized composite pile (CCP). In addition, it reviews the technical characteristics and recent progress of feasible low-carbon energy-efficient curing technologies. The paper also proposes future directions for theoretical research and technological development of low-carbon pile technologies. The key contribution of this review is to provide insights into efficient and low-carbon pile technologies. In addition, the findings from the study of the pile technologies used in extra-thick soft strata also provide industry practitioners with a comprehensive guide regarding the specific applications and mechanical performance of the pile technologies, which can serve as a stepping stone to facilitate the technological development of the underground space industry.

Mechanical performance of a prefabricated subway station structure constructed by twin closely-spaced rectangular pipe-jacking boxes

Traditional open-cut and cast-in-place construction methods for subway stations result in significant social and environmental problems, failing to meet green construction and sustainable development requirements. The pipe-jacking method could solve these problems, with the advantages of mechanised trenchless construction and prefabrication. Based on the engineering project of the Shasan station of Shenzhen Rail Transit Line No. 12 in China, a novel structure scheme of the subway station constructed by the pipe jacking method are discussed, including structure segmentation, joint design, longitudinal connections, waterproofing, and construction procedures. Subsequently, the specimens were tested under twice the values of the designed loads to obtain the bending resistance and shear resistance characteristics of the joint. Moreover, a simplified solid element section-spring model for mimicking the behaviour of the joint was established and validated by the test results. The mechanical performance of the station structure was investigated using three-dimensional finite element analyses by incorporating a simplified joint model. The results indicate that the structure deformation and stress meet the code requirements, demonstrating the applicability of the novel structure scheme. The research provides a practical solution for the trenchless construction of prefabricated subway stations, contributing to sustainable development of urban underground space.

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

AbstractThe 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 land‐sea integration needs to be established.

Causal effect of metro operation on regional resident mobility considering zone-based trip time reliability

The full use of underground space is recognized as a necessary means to improve the accessibility of residents and change the spatial distribution of urban population. The dividends generated by the metro operation will increase as the increases in the number of residents attracted to the zone. However, when the number of residents within the zone exceeds a certain threshold, travel accessibility may be reduced by exceeding the optimal service capacity of the metro, which leads to a decline in the per capita dividend. This paper uses the zone-based trip time reliability (TTR) to represent travel accessibility, and describes the interaction between the zone-based TTR and regional resident mobility. A generalized boosted method based Rubin causal model with longitudinal data was adopted to investigate the impacts of the improvement of zone-based TTR by metro operation on regional resident mobility. Then, an approximate BPR function was established to represent the feedback impact of regional resident mobility on zone-based TTR. Five typical areas considering population, average age, income level and land value are proposed to recognize the resident spatial re-segmentation rule. The results show that the metro operation has a significant impact on the regional resident mobility. And the improvement of zone-based TTR by metro operation is more attractive for resident relocation in Mixed and Stable areas than in Vibrant and Siphonic areas under the similar location distance. This paper intends to indicate the trade-off between zone-based trip time reliability (TTR) and regional resident mobility, and provide a reference for the development and utilization of urban underground space.

Impact of subway shield tunnel construction on deformation of existing utility tunnel

In recent years, the development of urban underground space in China, especially the construction and operation of subway tunnels, has greatly relieved the pressure of urban traffic. Due to the imperfect planning of urban facility, many subway tunnels have to be built under the existing utility tunnels (pipe galleries). Nevertheless, shield construction of subway tunnel has a great adverse impact on the deformation and safety of the existing pipe gallery. Therefore, this paper takes Xi’an Metro Line 2 as an example, and studies the safety depth for subway tunnel shield construction under different regional conditions in Xi’an through numerical simulation. The results show that the deformation of the existing pipe gallery and its influence range decrease with the rising buried depth of the double-line subway tunnel when the soil properties are good. For example, in the loess tableland area, when the buried depth of the subway tunnel is greater than 12 m, the settlement deformation of the pipe gallery basically meets the control standard. When the soil properties are poor or the soil properties vary greatly, the subway tunnel excavation has a great impact on the safety of the pipe gallery. For example, in the first-level alluvial fan area with sand layer, when the buried depth of the subway tunnel is less than 24 m and more than 12 m, the deformation standard cannot be satisfied. In addition, in the first-level alluvial fan area with sand layer, the lower soil layer should be treated or the construction parameters should be optimized before the excavation of subway tunnel. The research results can provide reference for similar engineering construction.

Variable-Weight Suitability Evaluation of Underground Space Development Considering Socioeconomic Factors

The suitability evaluation of urban underground space (UUS) development can aid in making the planning, construction, and operation management of underground spaces more scientific, orderly and systematic. Taking the starting area of Changjiang New Town as an example, this study considered socioeconomic factors as a crucial cost indicator in the suitability evaluation index system of underground space development, and 15 evaluation factors affecting underground space utilization were selected in combination with geological environment conditions. The subjective weights of each evaluation factor were calculated using the analytic hierarchy process (AHP), and variable-weight theory was introduced to calculate the comprehensive variable weights. The comprehensive variable weights were modified, taking socioeconomic factors into consideration, so as to quantitatively evaluate the development suitability of underground space in the research area. A comparison between the evaluation results of the constant-weight and variable-weight methods showed that the latter can correct the efficaciously determined subjective weight using the AHP and make the evaluation result more scientific and reasonable. A comprehensive consideration of the impact of socioeconomic factors on development costs and benefits made the evaluation results more instructive. The evaluation results showed that the area with the best suitability for underground space development in the study area accounted for approximately 18.6%, and the second-best suitable area accounts for approximately 60.8%. Hence, the development prospect of the study area is good.

Use of underground space resources when updating urban development

On the basis of taking into account global trends and best practices, the task of integrated urban development of urban underground space with the integral use of its main resources and services (not only spatial, but also other: geoenergy, geomaterials, groundwater) is set. Through the prism of the implementation of this "Deep City" model, national peculiarities are investigated and the current situation regarding the effectiveness of the system and documents of standardization (technical regulation) in relation to such topical formats of urban renewal as a model of integrated development (renovation) of the territory is evaluated. The main Sets of rules (as well as their current draft versions of such documents) that establish or should establish appropriate requirements for the implementation of this segment of urban development activities are identified and analyzed. The analysis was carried out in conjunction with the relevant areas of improvement of legal regulation. The results of the analysis showed the presence of systemic standardization defects (primarily gaps) and identified their causes. On this basis, general proposals are given to eliminate the identified defects, as well as general and specific proposals for the development (revision) of standardization documents. Such recommendations can be useful to the developer, the state customer, the executor of the draft Code of Rules and National Standards, as well as a representative of the expert community.

A system of integrated planning for the implementation strategy of urban underground space development technologies

A system of integrated planning for the implementation strategy of urban underground space development technologies

Study on emergency evacuation in underground urban complexes.

With progressive urbanization and the development and utilization of urban underground space, underground urban complexes (UUCs) have been increasingly used. UUCs have brought much convenience to people's lives. However, due to their enclosed nature and complexity, it has been an urgent issue to avoid (or reduce) casualties and allow rapid and safe evacuation of people during an emergency. In this study, the evacuation simulation software Pathfinder was used. Based on the steering model, the variation of the total evacuation time and pedestrian flow at main exits with different simulated evacuation measures, congestion at key nodes and people's path selection were compared and analyzed. Then, the critical locations in the spatial layout of UUCs that were prone to evacuation bottleneck effects were focused on and determined. The evacuation effectiveness of UUCs in an emergency was studied to investigate the problems of emergency evacuation in UUCs. It is found that in UUCs, the bottleneck effects were likely to occur at stairway entrances and exits as well as supermarket checkout counters and caused severe congestion. These locations should be focused on during emergency evacuation. For key locations prone to evacuation bottlenecks, increasing the width of exits or setting up auxiliary evacuation channels could be an effective measure to improve evacuation efficiency. In addition, formulating rational evacuation rules can be a favorable measure for emergency evacuation. However, during the evacuation, the herd mentality in people has an uncertain (positive or negative) impact on evacuation effectiveness. Setting up diversion walls may improve evacuation efficiency and reduce congestion to a certain extent, while evacuation confusion and chaos are prone to occur after diversion. These findings in this study have significant implications for improving the emergency management of UUCs.

Effects of Hydrostatic Dissolution and Seepage on the Transport and Mechanical Properties of Glauberite

During the development of urban underground space in Chengdu, China, it was found that glauberite rocks in the Guankou formation of the Cretaceous system had extensive dissolution and exerted a serious impact on the safety of the project. At present, research on the transport and mechanical properties of glauberite under hydrostatic conditions in this area is limited. In this paper, the effects of hydrostatic dissolution and seepage on the transport and mechanical properties of glauberite are studied. The results show that the concentration of aqueous solution increases step by step with the increase in the dissolution time of glauberite in still water, indicating that the forward movement of the dissolution front of glauberite rock is not a continuous process and has intermittent characteristics. The dissolution and infiltration of mirabilite seriously deteriorates the physical structure of mirabilite, resulting in a decrease in elastic modulus and an increase in axial deformation, and a decrease in mechanical properties. There are a dissolution layer, dissolution front and undissolved area in the karst infiltration of calcium and mirabilite in the hydrostatic solution, so the mechanism of the calcium and mirabilite karst dissolution process is determined. Because of the dissolution characteristics of mirabilite, underground space development should prevent the uneven settlement of mirabilite, ground collapse, pit and chamber water gushing, corrosive groundwater and other geological problems.

Does the scarcity of urban space resources make the quality of underground space planning more sustainable? A case study of 40 urban underground space master plans in China

The international community has reached a consensus on promoting the sustainable development of global cities. As an important and irreversible space resource in a city, the development and utilization of urban underground space should follow the principle of sustainability and emphasize scientific and forward-looking planning. At present, most cities have formulated urban underground space master plans. However, due to the lack of an effective evaluation method, the plan quality is uneven, which directly affects the sustainability of underground space development and utilization. This paper proposes a set of sustainability evaluation framework of underground space planning based on relevant planning standards and plan quality evaluation protocol, and makes a comparative analysis of the 40 urban underground space master plans formulated in China from 2004 to 2020. The research found that the planning documents generally reflected the problem of emphasizing design strategies and engineering technology while neglecting implementation and humanistic care; administrative region, population density, land price and other variables closely related to the scarcity of urban space resources are the main factors affecting the quality of urban underground space planning. The conclusions of this paper can aid planners and researchers to identify the problems and influencing factors of underground space planning related to sustainability, and summarize the methods to improve the quality of underground space planning.

Frequency-Bessel Transform Based Microtremor Survey Method and Its Engineering Application.

The development and utilization of urban underground space depend heavily on an understanding of urban geological conditions. The microtremor survey method is essential in urban geological surveys due to its quickness, convenience, non-destructiveness, and interference resistance. Since only the fundamental dispersion curves of Rayleigh waves can be obtained by utilizing the spatial autocorrelation method, the inversion results have multiple solutions. To improve the accuracy of the microtremor survey, this study employed the frequency-Bessel transform to extract the fundamental and higher modes of dispersion information of Rayleigh waves from the microtremor data array and verified the effectiveness of this method by synthesizing theoretical microtremor signals. Additionally, taking into account the order identification challenges brought on by mode jumps or missing modes in the dispersion curve, this study processed a multi-mode dispersion curve based on the newly proposed inversion objective function coupled with a genetic algorithm to obtain a shallow surface S-wave velocity structure. Compared to the traditional inversion objective function, the new function presented in this study could address mode misidentification more effectively and improved the accuracy of inversion calculations. Finally, the applicability and dependability of the frequency-Bessel-transform-based microtremor survey method were evaluated in a practical engineering case.

Evaluation of spatial performance and supply-demand ratios of urban underground space based on POI data: A case study of Shanghai

Master planning of urban underground space (UUS) is essential to guide orderly utilization of UUS. POI (point of interest) data from online maps provide a new data source for UUS research. This study proposed a simple framework to evaluate UUS development levels based on POI data. Evaluation methods of UUS spatial performance and development demand were established separately and then applied to the calculation of UUS supply-demand ratios of 217 sub-districts in Shanghai. The results showed that Huaihaizhonglu Sub-district achieved both the highest spatial performance and development demand values. The majority of the sub-districts with high or medium high performance values were situated in the central urban area. By comparison, the sub-districts with extremely low spatial performance clustered in the southern suburb and on Chongming Island. By means of Natural Breaks (Jenks) method, the sub-districts of oversupplied and undersupplied UUS development were figured out and then classified into five types to propose corresponding development strategies for future UUS utilization. The evaluation framework and results can give insights for more scientific and rational compilation of UUS master planning, especially for the metropolitan cities with a huge amount of developed UUS.

3D Quality Evaluation of Rock Mass in Urban Underground Space Based on Improved Fuzzy Analytic Hierarchy Process

Urban underground space (UUS) is an important resource to address the shortage of land, save resources and reduce environmental pollution, but it is irreversible. Therefore, it is necessary to evaluate its suitability before development. Rock mass is not only the carrier of UUS utilization, but also a key evaluation index, as it directly affects the evaluation results. Therefore, it is necessary to evaluate the 3D quality of rock mass from the perspective of UUS development. In this paper, a 3D quality evaluation model of rock mass in UUS is established based on an improved fuzzy analytic hierarchy process (IFAHP). Firstly, the subjective weight is calculated by analytic hierarchy process (AHP), and the objective weight is calculated by super-standard multiple method (SSMM). Then a new weight combination method (grey correlation analysis) is adopted. This method organically combines the subjective and objective weights, and the results show that the combined weight is more reasonable. Then the combination weight and fuzzy comprehensive evaluation method are combined with MapGIS to establish a 3D evaluation model. The case analysis shows that the evaluation results of the national standard BQ method are conservative, the traditional fuzzy analytic hierarchy process (TFAHP) is smaller, and the IFAHP is more robust. The case analysis also shows that the 3D evaluation has the advantages of strong intuition, good visualization and high precision, which is better than the traditional 2D evaluation. Moreover, the 3D evaluation model can not only be applied to this case, but also to other projects, and can provide decision-making for the development of UUS.