Yep, I had heavy rains between the dig/rebar and shotcrete, which caused several cave-ins during our build. Our contract didn't have any specifics, and the PB stepped up and fixed it at no additional cost. It took them about a half day with a crew of about 5 or 6 to dig out all of the cave-ins and reset the rebar chairs, etc. We were already in the water table by a few feet with our dig, so they had already dug out a sump pit, and had a pump installed to keep any significant water from pooling in the hole. After the cave-ins, they also dusted everything in the general vicinity of the cave-ins with Quickcrete to provide additional strength until shotcrete was installed. If I had to guess, they probably used 10-12 bags. That seemed to work well, as we had rain that continued for several days afterwards, and didn't have any more cave-ins. They also used thin plywood sheeting over the larger voids, as Aqua-holics suggested, which provide a strong enough backdrop when they did the shotcrete. After the shotcrete was in and had cured, they removed the plywood and backfilled the voids with dirt.