One of concrete slabs in our driveway has risen around 10 cm (4 inches) at the higher end and around 5 cm (2 inches) at the lower end as in the photos below. The slab is around 3 meters (10 feet) wide, 5 meters (16 feet) long, and 10 cm (4 inches) thick. It is also on a slope of about 20 degrees. When we bought the property around four years ago, this has already happened and there was a massive leopard tree around 1.5 meters (5 feet) away from the raised driveway section. We thought the tree was the problem so we removed it and had its stump ground. I also drilled several holes on the remaining stump and injected them with a tree poison diluted with kerosene. However, the driveway concrete slab seems to be still rising, although very slowly.
Were we right by considering that the tree roots had raised the driveway? Can the roots of the tree that we cut still be growing and pushing the concrete up? What would be the most cost-effective way to deal with the problem and prevent any further trouble?