Unified soil theory: There have been two schools of research on shear strength of soils advanced independently 5 decades ago in universities of cambridge(critical state soil mechanics) used for over consolidated (dilate and increase in volume when sheared) and normally consolidated or loose soil(decreae in volume when sheared) , and steady state theory(Harvard) used for soil liquefacton due to earthquake.This theory integrate both under one framework. Steady state theory included addtional criteria like constant velocity which is insignificant.