# Suitability Evaluation of Urban Underground Space Development: A Case Study of Qingdao City
## 1 Introduction
Findings from the experiments indicate a robust correlation between population density and per capita GDP with the intensity of underground space development. [PERSON] et al. [4] concluded, based on an analysis of factors influencing urban underground space development, that commercial land prices, economic location, economic development status, geological conditions, and compatibility with urban planning are the five main influencing factors of underground space development. [PERSON] et al. [19], taking Wuhan's Yangtze River New Town as a case study, suggested that urbanization indicators closely linked to urban planning and socio-economic conditions play significant roles in determining the intensity of urban underground space development. The selection of appropriate methods and models for evaluating urban underground space suitability is crucial, and it should be based on a comprehensive consideration of specific evaluation purposes, data availability, and research objects. [PERSON] et al. [20] developed an Analytic Hierarchy Process-based model for evaluating suitability, considering engineering geological conditions. [PERSON] et al. [21], in their study of underground station construction, conducted a comprehensive analysis using neural network algorithms and subsequently developed a suitability evaluation model for underground stations. [PERSON] et al. [22], in an effort to boost the precision of suitability assessment outcomes, proposed a TOPSIS system for evaluating the suitability of underground space development, leveraging the grey relational model. [PERSON] et al. [23]. employed fuzzy comprehensive evaluation methods to assess the construction risks of a proposed subway station in Ningbo, China. [PERSON] [24] proposed an indicator system and analytical process for assessing urban un derground space development, employing mathematical techniques like the Worst Case Scenario method and the Exclusion method. This methodology has been implemented in the evaluation of urban underground space development in cities such as Tongren, China. [PERSON] et al. (2018) applied the Analytic Hierarchy Process (AHP) to create a suitability assessment model for urban underground space development in Nantong, China. This allowed for a thorough evaluation of the feasibility, value, and quality of utilizing underground space resources. [PERSON] et al. (2018) quantitatively analyzed the compatibility between surface and underground spaces in Shenzhen, China, and employed an enhanced Artificial Intervention Genetic Algorithm to construct an evaluation model for underground space development, aiming to achieve optimal two-dimensional planning solutions. [PERSON] et al. (2018) employed a Bayesian Network model as a decision support tool, and researchers assessed the suitability of underground space development in Changsha, China. They also established a corresponding spatial database to streamline the assessment process. [PERSON] et al. (2018) put forward a suitability evaluation framework based on three-dimensional geological data. This framework integrates geological data with 3D technology and has been implemented in the geological suitability assessment of underground space development in Qianjiang New Town, Hangzhou, China. In summary, urban planning is a very complex issue that needs to collect data on the functions of the city's underground space, such as some underground structures. These existing underground structure data can be used to properly verify the evaluation results and provide some guidance, such as those used by [PERSON] et al. (2018), where a comprehensive approach to the feasibility of underground space development was proposed. On the other hand, many scholars, such as [PERSON] et al. (2018), [PERSON] et al. (2018), [PERSON] et al. (2018), [PERSON] et al. (2018), and [PERSON] et al. (2018), have taken another approach when evaluating the suitability of urban underground space development.