Help stop my pet from escaping?

My dog consistantly chews the bottom of the fence and escapes, I put up a metal grate and she tore that off and escaped, I put a wooden board and nailed it and she tore that off, finally put an iron sheet/kick plate at the bottom of the gate, she chewed at that and bent it then escaped. Nothing seems to work, we've also tried the no chew spray, the no stay spray, even putting a full propane tank (about 35-40 lbs) there and she still moves it, she herself is about 30 lbs. Please help me control my dog, other than the escaping she is a fantastic dog.