averaging

Dear All,

Could somebody indicate me some literature about the topic "2D
approximation of heterogeneous 3D media"?

In particular I am interested to address following issues:

1) Under which conditions averaging thermal conductivity and young
modulus (or more general, mechanical behaviour) on multiple 2D crossections of an heterogeneous "random"
material can be a good approximation for the behaviour of the real 3D
microstructure