How can I maintain a 2 in. (50 mm) thickness of shotcrete in a rock excavated tunnel?
There are many ways of maintaining the thickness of shotcrete. When placing shotcrete over a rough rock excavation, the thickness will vary with more material filling in the voids than covering the high points. Some methods of checking or maintaining the thickness are as follows: stabbing the plastic shotcrete with a depth gauge; preinstalling pins to the desired thickness; and using groundwires or shooting wires that would create an even plane over the length of the wires.
