An employee was working between two stacks of concrete posts spaced approximately 2 feet apart from one another. Each stack of posts had a total of two 12-foot long concrete posts, with the first stacked on a 4"x4" piece of dunnage. There was another post stacked on top of that with a 5" high piece of dunnage separating the two posts. As the employee was patching the posts, the 4"x4" dunnage on the bottom of the stack gave way and caused the stack to fall forward. The employee was pinned between the front stack of posts and the stack that fell forward. The employee's mid-section (front and back) was pinned for a few minutes until a forklift operator could push the stack off the employee. The employee was hospitalized for contusions to the upper body.