Title : Undrained capacity of laterally loaded underground walls subjected to horizontal load and moment

Page : PP.75-83

Author(s) : Suraparb Keawsawasvong and Boonchai Ukritchon

Keyword : Finite element, embedded walls, combined loading, plane strain.

Abstract : 

In engineering practice, underground walls, such as concrete diaphragm walls, are conventionally employed for constructions of deep excavations, basements, underpasses, cut-and-cover tunnels, etc. These walls may be subjected to combined horizontal load (H) and moment (M) that arise from external forces to support a permanent superstructure or a temporary platform of deep excavations. A new numerical solution of undrained capacity of laterally loaded walls under static conditions of combined horizontal load and moment is presented, which can be applied for predicting laterally loaded capacity of an underground wall with a sufficient horizontal length. The 2D plane strain finite element analysis is employed to determine the limit load of this problem. Dimensional parameters of the problem include undrained shear strength (su) of clay layer, unit weight of soil, and embedded length of wall (L). The embedded wall is modeled as an elastic material without failure consideration, while the clay is modeled as the Tresca material in an undrained condition. Results are summarized in the form of failure envelope of dimensionless variables as horizontal load factor and moment factor as a function of overburden factor. Associated failure mechanisms corresponding to dimensionless variables are also presented in the paper. It was found that for the case of no tension, the undrained lateral capacity of purely horizontal load ranges from 1.1 to 2.0 while that of pure moment ranges from 0.7 to 1.3. In addition, the failure envelope of walls subjected to combined horizontal load and moment has the form of rotated ellipse with distortion at both ends. The size of failure envelope is controlled by the overburden pressure factor. The increase of the overburden pressure factor results in the increase of size of failure envelope until it converges to that of the full tension case, whose the failure envelope is unaffected by the overburden pressure factor.

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