Thinking about building a underground shelter. I am finding conflicting information on the lateral strength of cinder-block walls filled with cement and reinforced with re-bar. If there are any structural engineers out there I could use some help. I don't want these walls moving in laterally when the structure is back filled and covered. I want to go down at least eight feet, I would prefer 16 but I need to find out what exactly is down there before I start digging.