With the development of society and economy

the range of the engineering problems that soil mechanics has to deal with is increasing; and these problems also become more and more complicated due to the interaction between soils and environments. In order to deal with these problems

the classical soil mechanics is required to be generalized and developed in depth and scope to incorporate the effects of new phenomena and new variables on soil behaviours. Based on a historical review of the development of soil mechanics

it is suggested that the classical soil mechanics faces three challenges: (1) lack of a unified

rational and theoretical framework of soil mechanics; (2) the knowledge and understanding of unsaturated soil behaviours is insufficient; (3) lack of a unified

rational and theoretical framework for multifield coupling problems of soils under multiple environmental actions. Finally

some problems beyond the scope of the classical soil mechanics are discussed.