Keywords

1 Introduction

At present, the scale and mileage of tunnel construction in China have become the world’s largest, but compared with other non-underground projects, the probability of tunnel safety accidents and quality accidents is higher, and the consequences are serious [1]. Although the construction technology and level of tunnel structure have been improved year by year, due to the influence and restriction of various factors such as geological, topographic and hydrological characteristics, tunnel engineering may suffer from water leakage, deformation, structural crack and other diseases during operation and service [2], which greatly reduces the quality and service life of the tunnel, has a great impact on society and traffic, and even threatens the safety of life and property.

Many scholars at home and abroad have studied the early warning and prediction of tunnel engineering. Such as Zhang Junru [3] developed the tunnel health monitoring and intelligent information management evaluation system, and put forward the new development trend of tunnel intelligent monitoring technology and information management system. Based on Java language and Access system, Fang Yu [4] developed a tunnel construction monitoring data analysis and management system. Frank et al. [5] proposed the problems and solutions of wireless monitoring in tunnel and other fields. TSUNO et al. [6] introduced a tunnel monitoring method based on wireless sensor network. ALBAM et al. [7] introduced a tunnel section analysis method based on rapid measurement of digital image displacement. Frank et al. [5] proposed the problems and solutions of wireless monitoring in tunnel and other fields. Bennett et al. [8] carried out continuous deformation monitoring research on tunnel structure based on wireless sensor network.

In view of the current situation of tunnel structure and operation and maintenance requirements, considering the problems of tunnel structure cost input, technical status and service life, this paper proposes a multi-dimensional monitoring and early warning system for tunnel operation safety based on the working status and disease characteristics of the tunnel during operation. The dynamic changes of the working status and disease characteristics of the key parts of the tunnel are monitored and analyzed, and the technical status of the tunnel structure is dynamically controlled in real time. The potential tunnel operation diseases are identified and judged accurately and in advance, so as to avoid the structural damage of the tunnel caused by “small danger and big risk “and” small disease and big disease. “In order to improve the durability and prolong the service life of the tunnel structure, the development trend of the tunnel structure disease is perceived in advance and the early warning is carried out in time, so as to serve the early warning and scientific decision-making of the tunnel danger, provide scientific data support for the tunnel design and preventive maintenance, and promote the progress and development of the tunnel structure material design technology.

2 Multidimensional Monitoring and Early Warning Technology

Traditional monitoring methods rely on a large number of manual participation, and the degree of automation participation is not enough. The safety monitoring and evaluation technology of tunnel structure has the problems of time-consuming and low accuracy, and the treatment methods of tunnel diseases mostly stay on the surface treatment of tunnel structure, ignoring the pre-perception and prediction of tunnel structure diseases. Multi-dimensional monitoring and early warning technology is based on a series of monitoring methods such as multiple monitoring sensors + three-dimensional laser scanning + tilt photography combined with BIM model, which is a comprehensive and full-life cycle comprehensive intelligent monitoring and early warning technology integrating structural monitoring, condition assessment and safety early warning. Compared with the traditional monitoring methods, multi-dimensional monitoring and early warning technology can dynamically control the technical status of tunnel structure in real time, accurately identify and judge the potential tunnel operation diseases in advance, pre-perceive and predict the development trend of tunnel structure diseases and give early warning in time. It can significantly improve the durability of tunnel structure and prolong its service life, and has a wide application prospect.

3 Research on Design of Monitoring and Early Warning System

3.1 General System Design

Based on the current situation of tunnel structure and operation and maintenance requirements, a multi-dimensional monitoring and early warning system for tunnel safety is designed by comprehensively considering the cost input, technical status and service life of tunnel structure. It can control the working state and disease changes of tunnel in real time, improve the durability of tunnel structure and prolong the service life, and provide scientific data support for tunnel risk early warning and scientific decision-making, as well as tunnel design and preventive maintenance. The multi-dimensional monitoring and early warning system of tunnel safety is composed of multi-dimensional monitoring unit, monitoring data acquisition and transmission unit and monitoring data platform. The multi-dimensional monitoring unit is composed of multi-dimensional monitoring sensor + three-dimensional laser scanning + oblique photography + BIM model. The multi-dimensional monitoring unit is arranged in the key monitoring section of the tunnel, and the monitoring data acquisition and transmission unit is connected with the monitoring data platform respectively to intelligently monitor the dynamic changes of the working status and disease characteristics of the key parts of the tunnel in real time and give early warning in time.

3.2 System Unit Design

The multi-dimensional monitoring unit is composed of multiple monitoring sensors + 3D laser scanning + oblique photography + BIM model. According to the engineering characteristics of the tunnel structure, the GNSS displacement monitoring system, crack meter, strain gauge and other multi-dimensional monitoring sensors are arranged in the uphill slope of the tunnel portal and the end wall of the tunnel portal. Based on the three-dimensional point cloud data obtained by 3D laser scanning and the panoramic aerial photography data of the tunnel structure obtained by oblique photography, combined with the BIM model, the multi-dimensional monitoring model of the tunnel structure is constructed to intelligently monitor the dynamic changes of the working state and disease characteristics of the key parts of the tunnel. The monitoring data acquisition and transmission unit is a data acquisition control box that transmits the monitoring data obtained by the safety monitoring unit to the safety monitoring data platform through the communication transmission module. The data acquisition control box and the communication transmission module are jointly arranged with the multi-monitoring unit. The monitoring data platform through the data interface server, data application server and data analysis server, the tunnel structure monitoring data storage, data screening, display management, emergency plan processing and intelligent early warning analysis.

4 Application Research of System

4.1 Project Overview

A tunnel is a separated tunnel. The right line of the tunnel is 812 m long and the left line is 760 m long. The stratum in the tunnel area is mainly the third stratum of the Indosinian period. The main structures are the Nading fault and the Nalang-Datong fault, which are non-new active faults and have little influence on the engineering geological stability of the tunnel area. The surface water in the tunnel area is mainly gully water, and there are gullies at the entrance and exit of the tunnel. The gullies have a great influence on the tunnel. The groundwater in the tunnel area is mainly pore water and bedrock fissure water in the Quaternary overburden. The tunnel layout is shown in Fig. 1.

Fig. 1.
figure 1

Site layout of a tunnel

Full size image

4.2 Monitoring Site Arrangement

The design concept of a tunnel is “people-oriented, safety first, and overall safety in the whole life cycle.” Considering the functions of highway tunnels, driving safety, natural environment and other factors, taking into account the requirements of construction and later tunnel structure operation, based on the multi-element monitoring sensor, the whole life cycle health monitoring is mainly carried out for the parameters such as secondary lining concrete stress, secondary lining crack, vault subsidence and peripheral convergence. Based on the three-dimensional point cloud data obtained by three-dimensional laser scanning and the panoramic aerial photography data of tunnel structure obtained by oblique photography. Combined with BIM model, a multi-dimensional monitoring model of tunnel structure is constructed to intelligently monitor the dynamic changes of working status and disease characteristics of key parts of tunnel. The layout diagram of the monitoring points of the tunnel monitoring section, the overall design diagram of the tunnel health monitoring, and the on-site installation diagram of the tunnel multi-sensor are shown in Fig. 2, 3 and 4.

Fig. 2.
figure 2

The schematic diagram of measuring point layout of tunnel monitoring section

Full size image
Fig. 3.
figure 3

Overall design diagram of tunnel health monitoring

Full size image
Fig. 4.
figure 4

Tunnel multi-sensor on-site installation diagram

Full size image

4.3 Monitoring and Early Warning Platform

The multi-dimensional monitoring and early warning platform for tunnel safety can query, browse, manage and analyze the monitoring data obtained by all multi-monitoring sensors and the three-dimensional point cloud data obtained by three-dimensional laser scanning in real time. Based on the tunnel BIM model, the monitoring layout of multiple monitoring equipment can be queried and displayed in real time. Based on the three-dimensional point cloud data obtained by three-dimensional laser scanning, all tunnel deformation monitoring data can be consulted and displayed in real time, and the analysis and research of tunnel deformation monitoring data can be carried out. Based on a series of monitoring methods such as multiple monitoring sensors + three-dimensional laser scanning + BIM model, the tunnel safety multi-dimensional monitoring and early warning system is an all-round and full-life cycle comprehensive intelligent monitoring and early warning system integrating structural monitoring, condition assessment and safety early warning.The BIM model diagram of the tunnel outside, the sensor of the tunnel monitoring section and the BIM model of the acquisition chassis are shown in Fig. 5, 6. The three-dimensional point cloud data map of the tunnel and the tunnel deformation monitoring data map based on the tunnel safety multi-dimensional monitoring and early warning system are shown in Fig. 7, 8.

Fig. 5.
figure 5

BIM model diagram outside the tunnel

Full size image
Fig. 6.
figure 6

Tunnel monitoring section sensor and acquisition chassis BIM model diagram

Full size image
Fig. 7.
figure 7

Tunnel three-dimensional point cloud data map

Full size image
Fig. 8.
figure 8

Tunnel deformation monitoring data map based on tunnel safety multidimensional monitoring and early warning system

Full size image

5 Conclusion and Suggestion

In this paper, the tunnel engineering project has a large one-time investment, long construction period, potential safety hazards, and structural cracks and deformation may occur during the operation period. The multi-dimensional monitoring and early warning system for tunnel safety is designed and applied. Compared with the traditional monitoring technology, the multi-dimensional monitoring and early warning technology is a comprehensive intelligent monitoring and early warning system for the full life cycle of the structure monitoring, condition assessment and safety warning. The system can query and display the monitoring and layout of multiple monitoring equipment in real time, query and manage all monitoring data in real time, control the technical status of tunnel structure in real time, identify and judge the potential tunnel operation diseases accurately and in advance, perceive and predict the development trend of tunnel structure diseases in advance and give early warning in time. It can significantly improve the durability of tunnel structure, prolong the service life, provide scientific decision-making services for tunnel danger warning and scientific decision-making, provide scientific data support for tunnel design and preventive maintenance, and promote the progress and development of tunnel structure material design technologyQ2.