Abstract:

In this paper, the mechanical and deformation characteristics of endsuspended piles of deep foundation pit in soilrock composite strata are studied, serving for safer and more economical design of deep foundation pit. Adopting An analytical model of deep foundation pit with suspendedpile retaining wall system in soilrock composite strata is established by twodimensional numerical simulation method. The main study content includes the development process of internal force and deformation of the retaining structure during the excavation and the relationship between the elastic modulus ratio RE, rocksocketed depth t, rockshoulder width b and the force, deformations of the piles. Some conclusions are drawn as follows: (1)The lateral displacement of the piles increases and the position of the maximum lateral displacement of the piles shifts downward as the excavation depth increases, and the maximum downward scope is 17.5% of the thickness of the soil layer. (2) When the foundation pit is excavated to the interface of soil and rock, the internal force of the piles reaches the peak, and the maximum negative bending moment of the piles is reduced by 27.5% due to the excavation of the lower rock layer. (3) When the elastic modulus of the rock layer is between 600 MPa and 4 800 MPa, the optimal design rocksocketed depth is 1.5 m, and the optimal design rock shoulder width is 1.5~2.0 m.

Key words: soilrock composite strata, endsuspended pile, rocksocketed depth, rockshoulder width