Smart monitoring system for risk management in the underground space

This paper presents a smart monitoring system for risk management in the underground space. This space has a major role in cities, but it suffers from high vulnerability to hazards such as fire, flood and accidents. The paper provides analysis of the vulnerability of the underground space and shows how a smart monitoring system of human presence, indoor conditions, underground space access and equipment performances with advanced data analysis could help in improving the risk management in this space

Development of a 3D modeling algorithm for tunnel deformation monitoring based on terrestrial laser scanning

Deformation monitoring is vital for tunnel engineering. Traditional monitoring techniques measure only a few data points, which is insufficient to understand the deformation of the entire tunnel. Terrestrial Laser Scanning (TLS) is a newly developed technique that can collect thousands of data points in a few minutes, with promising applications to tunnel deformation monitoring. The raw point cloud collected from TLS cannot display tunnel deformation; therefore, a new 3D modeling algorithm was developed for this purpose. The 3D modeling algorithm includes modules for preprocessing the point cloud, extracting the tunnel axis, performing coordinate transformations, performing noise reduction and generating the 3D model. Measurement results from TLS were compared to the results of total station and numerical simulation, confirming the reliability of TLS for tunnel deformation monitoring. Finally, a case study of the Shanghai West Changjiang Road tunnel is introduced, where TLS was applied to measure shield tunnel deformation over multiple sections. Settlement, segment dislocation and cross section convergence were measured and visualized using the proposed 3D modeling algorithm. Keywords: Terrestrial laser scanning, Tunnel, Deformation monitoring, Point cloud, 3D modelin

Role of Internet of Things (IoT) and Crowdsourcing in Smart City Projects

International audienceThis paper presents and discusses the role of the Internet of Things (IoT) and crowdsourcing in constructing smart cities. The literature review shows an important and increasing concern of the scientific community for these three issues and their association as support for urban development. Based on an extensive literature review, the paper first presents the smart city concept, emphasizing smart city architecture and the role of data in smart city solutions. The second part presents the Internet of Things, focusing on IoT technology, the use of IoT in smart city applications, and security. Finally, the paper presents crowdsourcing with particular attention to mobile crowdsourcing and its role in smart cities. The paper shows that IoT and crowdsourcing have a crucial role in two fundamental layers of smart city applications, namely, the data collection and services layers. Since these two layers ensure the connection between the physical and digital worlds, they constitute the central pillars of smart city projects. The literature review also shows that the smart city development still requires stronger cooperation between the smart city technology-centered research, mainly based on the IoT, and the smart city citizens-centered research, mainly based on crowdsourcing. This cooperation could beneficiate in recent developments in the field of crowdsensing that combines IoT and crowdsourcing

GPR data processing methods based on machine learning algorithm to detect the backfill grouting of shield tunnel

Shield tunnel method is currently the most important method for tunnel excavation in soft soil areas. With the construction and operation of a large number of tunnels in China, a certain degree of structural disease have appeared in the tunnels. How to control the settlements of tunnels and take corresponding measures to ensure the safety of operations has attracted great attention from design and operation management departments. In this chapter, FDTD numerical simulation of backfill grouting by GPR is performed. The GPR images of grouting layers with different thicknesses of 400MHz antenna and 900MHz antenna were simulated respectively, and the theory of integrated learning XGBoost is established. The XGBoost model was trained with numerical modeling data to obtain classification models of grouting layers of different thicknesses under 400 MHz and 900 MHz GPR, and the results showed that the GPR data could be classified and pattern recognized well under this circumstanc

The Tunnel Structural Mode Frequency Characteristics Identification and Analysis Based on a Modified Stochastic Subspace Identification Method

With the rapid development of underground engineering in China, the heavy structural maintenance work followed is expected to be a great challenge in the future. The development also provides a promising application prospect for the newly developed vibration-based health assessment and monitoring methods. However, the fact that tunnels are embedded in soil makes collecting and identifying the vibration characteristics more difficult, especially for the online monitoring. In this paper, a new identification method that combines the natural excitation technique (NExT) and stochastic subspace identification (SSI) method is developed. The new method is compared with the traditional SSI method, and mode frequency analysis is made based on a series of field tests carried out at the subway and power tunnel. It is found that both stability and efficiency of the mode frequency identification have been greatly improved, and it more suitable for online monitoring. Meanwhile, a mathematical model is used to analyze the original mode characteristics and the influence of soil coupling. The results are also compared with the field tests results by using the NExT-SSI method, and some recommendations are also made for how to choose the vibration modals for vibration-based monitoring in the tunnel

Experimental Study of the Behavior of Rectangular Excavations Supported by a Pipe Roof

This paper presents an experimental investigation of the role of pipe-roofs in the improvement of the stability of rectangular excavations constructed using pipe-roof technology. This technology is suitable for the construction of underground passages in crowded areas subjected to high requirements concerning soil settlement and stability during excavation construction. The design of a rectangular pipe-roof excavation required an understanding of the interaction between the soil, the pipe-roof and the excavation. This interaction is complex and plays an important role in the features of the pipe roof excavation. This paper presents a series of 1g physical experimental tests conducted in dry sand soil with an advanced monitoring system, which allows tracking of the soil settlement, the pipe deformation and the soil pressure. Analysis of these tests shows the effective role of the pipe-roof in reducing both the soil settlement and the soil pressure on the excavation. It also shows the influence of pipes on the deformation mechanism of the soil and its evolution from low deformation to the instability phase

Vibration Characteristics of Underground Structure and Surrounding Soil Underneath High Speed Railway Based on Field Vibration Tests

A series of field vibration tests were carried out at an underground metro station underneath the high speed railway by installing accelerometers both on the side wall of the metro station and in the surrounding soil. Within the frequency domain of 0–200 Hz, the attenuation, transmission, and frequency response properties of vibration for both the underground structure and the surrounding soil were analyzed and compared. The attenuation index is found to be decreased with the increase of underground structure stiffness. The existence of damping and coupling effect of the surrounding soil, as well as the interference of axle spectrum from excitation sources, makes it very challenging to separate the frequency response characteristics of structures from soil at FFT (Fast Fourier Transform) spectrum. The combined NExT (Natural Excitation Technique) and HHT (Hilbert–Huang Transform) method are thus used to study the waveforms and propagation velocities of vibration waves in underground structure and surrounding soil. The wave types and their speeds are determined and used for evaluating the structural elastic modulus. Compared with the attenuation index or natural frequency, wave velocity is easier to be recognized, is sensitive to the change of the structural stiffness, and requires limited number of sensors in the field. Based on the properties of the vibration characteristics studied in this work, the wave velocity based method is recommended for the health monitoring of underground structures

Deep Learning Model for Shield Tunneling Advance Rate Prediction in Mixed Ground Condition Considering Past Operations

International audienc

Use of Smart Technology to Improve Management of Utility Tunnels

This paper presents a smart solution for the utility tunnel, which allows hosting a wide range of water and energy utilities in an accessible underground space. It is well known that utility tunnels offer major advantages such as the possibility to inspect, maintain, and easily extend urban utilities without excavation, thereby eliminating disturbances related to urban excavation such as traffic jams, noise, pollution, and pavement degradation. However, despite these advantages, the effective development of this facility remains below expectations, because of serious challenges related to the security and governance of this “shared space”. The solution presented in this paper is based on discussions with experts and companies involved in the design, construction, and management of utility tunnels, as well as on the authors’ experiences in the design and implementation of smart solutions for urban utilities. The paper firstly presents the major challenges of utility tunnels and then discusses how theb smart technology could help in coping with these challenges. The paper presents the architecture of this solution, as well as the main layers of monitoring, information system data analysis, and system control. It also presents the methodology to be followed for the implementation of this smart solution. Finally, the paper discusses two major issues for utility tunnels: fire risk and risk assessment. The paper shows that the use of smart technology allows developing a comprehensive digital solution, which uses advanced monitoring system to collect real-time data about the tunnel environment and functioning. These data can be easily shared by authorized staffs. Analysis of these data allows improving the utility tunnel security and performances