Does homeowners insurance coverage damage to swimming pool liner from the chemicals added?

No. This sounds like a manufacturer or maintenance issue. Something is wrong with the pool itself or with the way it was installed as the earth behind pool walls has washed away making it loose support and fail. For a homeowners policy to pay for damages the damage must be the fault of a covered cause. I can't see how the damage you are describing could be from a coverer cause. Homeowners insurance is not made to cover maintenance issues or manufacturer defects. First I would contact whoever installed the pool. If it has been past the warranty period I would check with a professional to see what the cause of the damage is first.