It can be done, it all depends on the material your liners are made of. You can't just use a tube of silicone. Assuming you are using EPDM liners, you'll need the proper seam tape and adhesive. The liners have to be cleaned thoroughly (a solvent like alcohol can be used). They need to be overlapped by the suggested amount, adhesive applied, seam taped, a roller used with even pressure, flipped over, then adhesive (if the overlap wasn't fully covered), seam taped and roller again. Basically a double seam. You need to be careful as not to have any creases or stretching.
If it's not EPDM, you'll have to research that particular product. If the seaming products are not compatible with your liners, there will likely be failure.
I personally would not chance it, but that's me. The way I look at it is the fact that a liner is the very base of your project. Everything is built up from there. Plants, stones, waterfalls, fish, etc. If your liner fails, not only is it very difficult to locate a leak, but if you have to replace the liner, you will need to tear everything out.
Try and replace a liner in the dead of a Pennsylvania Winter. I experienced that. I had to add 300 gallons every week until Spring came. Not fun...
