A quality control method for shotcrete strength by pneumatic pin penetration test

Shotcrete is applied as a significant support element in tunneling because of its rapid strength development by adding accelerators. Thus the investigation of real shotcrete strength of tunnel lining is required for stabilization of excavation surfaces. Therefore, a pin penetration test using air pressure as the penetrating energy is proposed as a simple in situ test method. In this method, the penetration depth is used as an indication. Because of the close relationships between the penetration depth and wide range of compressive strength obtained from laboratory and field tests, the new testing method is considered effective for shotcrete. In addition, the application of this simple in situ test enables strength control to be undertaken with short intervals and to identify nonuniformity of the lining caused by accelerator dosage.