A creature that is moved by someone else than themselves does not cause Attacks of Opportunity. When being forced to move through solid objects, e.g. through a wall, they take 1d6 damage for each square of movement they would need to make. The solid object breaks if 10 + sq of forced movement equals or beats the strength of the object, and the character is thrown through the object and continues until their forced movement is depleted.

Example: The fighter Torm is being pushed by a Hurricane spell against a wooden wall 1 sq away from him. The spell would push him for 10 sq. He hits the wall and takes 9d6 damage. The wall is made of wood, so it only has 14 strength and breaks. Torm crashes through the wall and 5 sq further. He is now 6 sq from his starting position away. In the wooden wall there is a hole roughly Torms size (1 sq, 2 sq high).

 

Crashing into another creature stops you movement, but means both of you take half the damage of 1d6 times the remaining squares.