| Crack Survey Technique for Concrete Linings
Correctly comprehending the extent of cracking is an inevitable item for planning tunnel repairs. JH has developed a system to monitor crack propagation through time using a concrete lining inspection vehicle which travels at 50km/hr using argon laser radiation and continuously reading the amount of reflection to accurately understand the status of cracking, and causing no restrictions to traffic. In addition, by carrying out the crack inspection survey at 50km/hr, an inspection technique using a CCD digital video camera has also been developed
Inspection Technique for Back Face Lining Cavities
For tunnels not constructed using shotcrete and rockbolts,and through such as the corrosion of sheet pile linings, the washing away of ground etc. can cause cavities to form on the back face of linings, which can have a detrimental effect on the long-term durability of the tunnel, and so it is necessary to have an efficient method to inspect for such cavities. JH is currently developing a system whereby high-speed rotary percussion drills acting on the concrete lining can have real time mechanical data measurements collected on the drill hole speed, impact pressure and rotation pressure, thus enabling the lining thickness, scale of cavities and the relative strength of the concrete and the ground condition to be understood. Furthermore, the holes made during the inspection can be used as injection holes for grouting works following the inspection.
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