The GPR (Ground Penetrating Radar) conference in Hong Kong year 2016 marked the 30th anniversary of the initial meeting in Tifton, Georgia, USA on 1986. The conference has been being a bi-annual event and has been hosted by sixteen cities from four continents. Throughout these 30 years, researchers and practitioners witnessed the analog paper printout to digital era that enables very efficient collection, processing and 3D imaging of large amount of data required in GPR imaging in infrastructure. GPR has systematically progressed forward from “Locating and Testing” to “Imaging and Diagnosis” with the Holy Grail of ’Seeing the unseen’ becoming a reality. This paper reviews the latest development of the GPR’s primary infrastructure applications, namely buildings, pavements, bridges, tunnel liners, geotechnical and buried utilities. We review both the ability to assess structure as built character and the ability to indicate the state of deterioration. Finally, we outline the path to a more rigorous development in terms of standardization, accreditation, and procurement policy.

A review of Ground Penetrating Radar application in civil engineering: A 30-year journey from Locating and Testing to Imaging and Diagnosis

The non-destructive testing and diagnosis of transport infrastructures is essential because of the need to protect these facilities for mobility, and for economic and social development. The effective and timely assessment of structural health conditions becomes crucial in order to assure the safety of the transportation system and time saver protocols, as well as to reduce excessive repair and maintenance costs. Ground penetrating radar (GPR) is one of the most recommended non-destructive methods for routine subsurface inspections. This paper focuses on the on-site use of GPR applied to transport infrastructures, namely pavements, railways, retaining walls, bridges and tunnels. The methodologies, advantages and disadvantages, along with up-to-date research results on GPR in infrastructure inspection are presented herein. Hence, through the review of the published literature, the potential of using GPR is demonstrated, while the main limitations of the method are discussed and some practical recommendations are made.

A review of GPR application on transport infrastructures: Troubleshooting and best practices

Periodic monitoring of tunnel conditions and deterioration rates is the answer to determining the appropriate schedule of maintenance or rehabilitation activities to remedy structural problems that could lead to rapid deterioration and unexpected tunnel failures. The aggressive environmental conditions in which tunnels exist, as well as the need to keep tunnels open to traffic, make their inspection a challenge. Nondestructive testingmethods that are automated, quantitative, and rapid, and that provide complete coverage compared with conventional visual inspections, could solve this dilemma. This report presents the findings of the Strategic Highway Research Program 2 (SHRP 2) Renewal Project R06G—High-Speed Nondestructive Testing Methods for Mapping Voids, Debonding, Delaminations, Moisture, and Other Defects Behind or Within Tunnel Linings. The study was divided into two phases to (1) establish testing criteria and prioritize the techniques to be developed and evaluated under the project on the basis of tunnel operators’ requirements and (2) conduct the necessary technology development for those techniques recommended. In addition to conducting technology development, the project performed proof-of-concept and field testing. Beyond this report, the deliverables for this project include two products that will be published separately: 1) a user’s manual, which provides information on three NDT technologies for inspection of tunnels; and 2) a brief manual to the analysis software Tunnelcheck, which was developed under this project.

High-Speed Nondestructive Testing Methods for Mapping Voids, Debonding, Delaminations, Moisture and Other Defects Behind or Within Tunnel Linings

A full-face vehicular detection method for a railway tunnel lining and a device aim to avoid collision of ground penetrating radar antennas with an overhead line system and a support of the overhead line system, the detection speed is a normal running speed of a train, the antennas in full-face detection are not interfered with each other, automatic positioning is realized during detection, only ground penetrating radar signals in a tunnel need to be acquired, and a penetrating radar signal processing and analyzing method in tunnel detection is modified. The vehicular device comprises a six-channel high-speed scanning penetrating radar, a positioning portion, a laser ranging portion and data acquisition and processing software. The pulse repetition frequency of the ground penetrating radar is 3MHz, the pulse repetition frequency of each channel is 500kHz, and the scanning rate is 976scan/s. The ground penetrating radar is provided with TEM (transverse electric and magnetic field) short-horn air coupled antennas, each group of antennas realizes a double-transmission and single-receiving function, and the center frequency of the antennas is 300MHz. The ground penetrating radar antennas are mounted outside passenger train connectors, radiation surfaces of the antennas respectively face to an arch crown, arch springing and side walls, and the full-face vehicular detection method and the device are used for automatically detecting to exam the railway tunnel lining.

Full-face vehicular detection method for railway tunnel lining and device

Convolutional networks and transformers for intelligent road tunnel investigations

An innovative vehicle-mounted GPR technique for fast and efficient monitoring of tunnel lining structural conditions

The health status of a railway tunnel should be regularly inspected during its service period for safe operation. The frequency of periodic inspection should be increased when the tunnel has become aged. For the coverage tunnels, health assessment is more essential. Ground penetrating radar (GPR) has been used as a key tunnel health detecting technique; however, so far, such (GPR) techniques are in contact mode. Such methods cannot meet the requirements for tunnel disease prospection and regular inspections across the whole operational network. Therefore, a new method has been developed that uses long-range detection with the train-mounted GPR. It consists of six channels, whose air-launched antenna distance to the sidewall is about 0.93m∼1.5m, and the distance to the vault is 1.7m∼ 2.25m. The scanning rate of each channel is 976 scans/second. When the sampling point interval is 5cm, the maximum test speed can reach up to 175km/hr. With such a speed and air-launched antenna, this system has a big advantage over existing methods. That is, for electrified railways, there is no need for power outages and for inspections to occupy time during maintenance periods. Indeed, they will not interrupt normal railway operation. The running tests with this system have been carried out on the Baoji-Zhongwei and Xiangfan-Chongqing railway lines and very good test results have been obtained.

A train-mounted GPR system for fast and efficient monitoring of tunnel health conditions

Distribution pattern and change prediction of Saposhnikovia divaricata suitable area in China under climate change

The utility model, which belongs to the filed of a railway tunnel inspection technology, provides a full-section vehicle-mounted detection apparatus for a railway tunnel lining The technical problems that can be solved by utilizing the detection apparatus are as follows: collision of an antenna of a ground penetrating radar with an overhead contact system and a support thereof can be avoided and the detection speed is a normal driving speed of a train; all the antennas are not interfered with each other during the full-section detection process; automatic positioning can be realized during the detection process and only signals of ground penetrating radars are collected and recorded in a tunnel; and methods of processing and analyzing of the signals of ground penetrating radars in the tunnel detection are improved The vehicle-mounted detection apparatus comprises a six-channel high-speed scanning ground penetrating radar portion, a positioning portion, a laser ranging portion The pulse repetition frequency of the ground penetrating radar is 3MHz and the pulse repetition frequency of each of the channel is 500 kHz; the scanning rate is 976 scan/s; and each of the antennas is a TEM short-horn air-coupled one, each group of antennas includes two transmitting antenna and one receiving antenna, and the center frequency is 300 MHz The ground penetrating radar antennas are installed outside a train connecting body; and the radiating surfaces of the antennas are respectively pointed at the vault, the arch springs and the side walls The provided apparatus is mainly applied to automatic detection of a railway tunnel lining

Xiyuan Zhang

Papers

An innovative vehicle-mounted GPR technique for fast and efficient monitoring of tunnel lining structural conditions

Full-face vehicular detection method for railway tunnel lining and device

A train-mounted GPR system for fast and efficient monitoring of tunnel health conditions

Distribution pattern and change prediction of Saposhnikovia divaricata suitable area in China under climate change

Full-section vehicle-mounted detection apparatus for railway tunnel lining