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The development of urban underground space (UUS) is an important approach to the sustainable development of modern cities. This means that assessing potential demand differences in undeveloped UUS can inform the areas that need to be prioritized for development in urban planning and development. The recent emergence of geospatial big data provides fine-grained support for capturing changes in the development of various urban subjects. However, to date, research applying geospatial big data to UUS assessment has been limited. In this study, UUS evaluation indicators were constructed using geospatial Big Data, and the weights of the indicators driving the existing UUS demand were determined based on the Geodetector model, avoiding the drawbacks of human subjective influence and the lack of reference of general methods. It also combined the linear weighting method to quantify the UUS demand in undeveloped areas within the grid based on the attribute values and weights of each indicator and used the magnitude of the resulting demand values to provide a grid-scale judgment of priority areas for future underground space development. Taking the Qiantang District of Hangzhou, China, as an example, it was verified that the high-demand areas are consistent with the existing UUS distribution, indicating that the UUS demand evaluation model based on geospatial big data established in this study is feasible and accurate, and in this way, new high-demand areas were circled in the undeveloped areas as a direction for future urban underground development. [ABSTRACT FROM AUTHOR]

The high-speed rail (HSR) network in China has expanded rapidly, significantly reducing transportation costs and improving accessibility. However, scholars are concerned about whether HSRs further centralize resources and intensify regional polarization. This paper studies the role of HSR in the process of urban development and regional integration in the Yangtze River Delta (YRD). We use two indicators (overall connectivity and weighted centrality) to examine the impacts of HSR connection on spatial redistribution, and we adopt a difference-in-differences (DID) analysis to investigate the effects of HSR on local economic development. The results show that HSR operation enormously improves the overall connectivity of urban networks in the YRD. However, it also exacerbates the disequilibrium of urban centrality, forming a hierarchical spatial structure with Shanghai, Nanjing and Hangzhou as hubs. HSR connections also impede local economic growth in peripheral areas. Moreover, the results confirm the existence of a dynamic time-lagged effect on local economic growth, and the heterogeneous impact of HSR also aggravates regional economic disparities. This paper highlights the effects of HSR on the development of cities and regions, and suggests that government should exert greater efforts to reduce the negative effects of the development of HSR. [ABSTRACT FROM AUTHOR]

• Framework of UUS geological suitability evaluation in 3D (3D-UGSE) is proposed. • Implicit method enables fast automatic generation of underground geological bodies. • 3D spatial analysis methods extract more evaluation factors via data integration. • 3D-UGSE framework gives more evaluation results and enhances down-depth resolution. Geological suitability evaluation for urban underground space (UUS) is essential for effective UUS utilisation and exploitation risk reduction. However, previous research was hampered by limited availability of 3D technology. The 2D data-based evaluation process has led to information loss among underground data, whilst evaluation results without 3D attributes would also impede accurate analysis and further application. This study presents a novel UUS geological suitability evaluation (3D-UGSE) framework, which accounts for the characteristics of 3D data and other practical requirements. The framework integrates a large amount of available geoscientific data with 3D technology, and contains five steps: (1) data collection and integration; (2) 3D geological model construction using implicit 3D geological modelling method with multi-source geological data; (3) 3D evaluation index system creation, considering local geological conditions based on the available data; (4) 3D thematic map production from the 3D geological models, using 3D spatial analysis methods; (5) 3D geological suitability map production, integrating all the 3D thematic maps using comprehensive evaluation methods. To evaluate this approach, we took the Qianjiang Newtown in Hangzhou (eastern China) as an example and assessed the UUS geological suitability in three dimensions. The results show that the 3D-UGSE framework can effectively integrate 2D and 3D geological information, give more reasonable and informative evaluation results, and enhance the depth resolution of the results. This approach can provide more useful information for the planning, sustainable development, and utilisation of urban underground space. [ABSTRACT FROM AUTHOR]