problems rehabbing an inground vinyl

[baudiom]

I have not been able to find the info I need for this situation. I have a in ground vinyl lined pool. The liner failed and I drained it and ordered the new liner. In to process of cleaning the pool bed, I discovered that what I thought was cement has turned to sand. I tried to patch using a portland cement grout, but it won't adhere to the sand well enough to trust. what is my next step? I really need to get the liner in and the pool filled before Rochester's winter ruins everything. here is a pic of the worst spot where the sand has deteriorated.
That is where the fiberglass side wall meets the slope in the deep end.

I am sure the pool has been patched before. This is the slope from the shallow to deep end showing some patches.:

Any knowledge of what to patch with would be helpful. I am still hoping to put the liner in this weekend.

 

[msumoose]

The portland cement should be mixed with sand. A 5 to 1 sand to cement mix is what I use. Make sure it is masonary sand that is washed. It does not have to be awesomely hard, just there to support weight.