Abstract: The deformation and failure properties of natural soils are influenced by many complex factors, which can be summarized into five aspects. Firstly, the deformation and strength properties of soils vary with the types,levels and paths of stresses.Secondly,it vary with the elastic or plastic strains,which leads to strain hardening or progressive failures.Thirdly,it is influenced by pore pressures,which vary with drainage conditions.Fourthly,it is influanced by the speed of loading,which varies from instantaneous to longterm or vibrational loads.Fifthly,the anisotropic and non-homogeneous properties of soil add complexity to the problem of soil mechanics.Owing to these complexities,it is inevitable that the theoretical computations in most soil mechanics problems can not predict precisely the actual facts.While a designer computes a soil mechanics problem by a certain theory,he should consider also the possible influencences by many other factors which were not acconted by that theory,and add his judgements fo comprehensive analysis to the computeod reaults.