# Digital Twins' Application for Geotechnical Engineering:
## 2 The Current Situation of Digital Twins in Geotechnical Engineering  
Geotechnical engineering is composed of soil mechanics, rock mechanics, engineering geology, and corresponding engineering and environmental disciplines. It serves different engineering categories, such as construction, water conservancy, hydropower, transportation, railway, aviation airports, water transport, oceans, petroleum, mining, the environment, and the military, and even aerospace and other engineering fields all cannot do without geotechnical engineering [19]. With the rapid advancement of projects such as urban rail transit, underground pipe galleries, high-speed railways, and highways, traditional engineering technologies and management models struggle to meet the needs of modern geotechnical engineering. The refined management and informatization construction of geotechnical engineering have become inevitable, and digital twins have begun to enter the field of geotechnical engineering. The current situation of digital twins in geotechnical engineering in various fields is as follows [20; 21]:  
(1) In the field of urban construction:  
After entering the 21 st century, with the improvement of computing power and the development of big data technology, digital twins gradually expanded to the field of urban management [22]. In the early 21 st century, the concept of smart cities gradually emerged,and various places began to explore how to use information technology to improve urban management efficiency and quality of life. Digital twin technology became an important tool in this trend. By the 2010s, the application of digital twins in cities began to receive wider attention. The virtual model of the city was no longer a static three-dimensional model but a dynamic system integrating multiple technologies, such as sensor data, real-time monitoring, and simulation prediction. At present, the application scenarios of digital twins have relatively mature practical cases in the fields of transportation, parks, urban emergencies, and so on ([PERSON] and others, 2018). The basic technology platform architecture of digital twin cities is shown in Figure 1. Cities such as Singapore and Amsterdam took the lead in realizing the application of digital twins, helping urban managers make better decisions. Exploration of digital twin cities has also been carried out successively in China. For example, [PERSON] et al. (2018) took the Spring Area in Jinan as an example and established a four-dimensional geological environment database and digital twin model based on the theory of digital twins, which can achieve the visualization of three-dimensional geographic and geometric models, water level models, karst models, borehole models, fracture models, geological models, and hydrological models, as well as above-ground buildings, underground structures, municipal pipelines, and subway models. This model can also change over time. [PERSON] (2018) proposed an urban digital twin model based on digital twin technology, which includes five modules--physical city, virtual city, intelligent service, twin data, and virtual-real interaction--and established an urban flood disaster assessment and early warning digital twin system (Figure 2), which helps to realize the functions of automatic monitoring and early warning of urban flood disasters, real-time intelligent command and dispatch, and improving the capabilities of existing cities in flood disaster assessment, early warning system perception, dynamic response, and real-time decision-making. Figure 1: Basic technology platform architecture for digital twin cities (reproduced from the report of iResearch Consulting Institute ([PERSON] and others, 2018)). [PERSON] et al. [25] proposed a digital twin-based framework for smart city energy management, which significantly improves renewable energy integration efficiency and grid stability through real-time data integration and AI-driven simulation optimization.