The polyurethane grout, SealGuard II, was needed to mine forward in this tunnel. The tunnel was in a fault zone, and all the voids were to be filled with concrete. However, when injected, the concrete leaked out of the face. To contain the concrete, polyurethane grout was injected to provide a buffer. SealGuard II reacts is about 3 seconds and produces a rigid foam (900 PSI compression strength). With the concrete contained in its intended location, advancing was able to commence. SealGuard II is manufactured by SealGuard, Inc. and the grouting was performed by Sub-Technical, Inc.
