Getting rid of an unconquerable weed I planted

Several years ago I planted a vine (purchased at Wal-Mart for $4 - first mistake I made) in a street-facing bed next to my garage. It was supposed to have beautiful red flowers and climb the side of the garage. It has never flowered, despite being in full sun and being extremely invasive. Two years ago I gave up on it and tried to kill it (pull it all up, baste it with lethal plant killer, etc.). It is indefagitable. Finally last spring, I pulled it out as best I could, covered the bed with old clothes, and hauled new dirt in on top of it. Then I planted a new veggie garden on top. It STILL comes through with a vengance, choking everything I love there. Any ideas how to convince it to give up? Much thanks in advance!