The paper presents a numerical study of the elastic response of laterally loaded rock sockets. Sockets are loaded at the top with transverse forces and bending moments and the corresponding displacements and rotations are calculated. 3D finite element analyses are carried out to investigate the effects of shaft length, relative stiffness of socket to rockmass and the ratio of the applied moment to shear force. The rockmass is assumed to be linearly elastic, as rock sockets rarely reach the rockmass strength. However, socket-ground interface elements are used along the periphery and at the socket base in order to simulate separation and lift-up effects on the response. The results of the analyses are compiled in semi-empirical dimensionless relationships giving the socket stiffness in terms of the important parameters. The produced results showsignificant differences compared to the results of numerical analyses reported by Carter & Kulhawy (1992) where separation and lift-up effects were not included.

1 Introduction

Rigid sockets are nowadays an effective foundation type of structures founded with tall piers. The specific foundation undertakes significant horizontal loads and bending moments, thus it undergoes considerable horizontal displacement and rotation on its head.

Two different approaches are met in common engineering practice for the estimation of the aforementioned socket head deformation. One approach involves the subgrade reaction methods, including numerous methodologies of p-y curves for rock that serve the presence of non-linear, horizontal springs along the socket (Reese 1997, Gabr et al. 2002). On the other hand stands the elastic continuum theory, which treats the rigid socket as an equivalent spring with three independent degrees of freedom for the prescribed loading conditions (Douglas & Davis 1964, Carter & Kulhawy 1992).

The scope of the present paper is the evaluation of the socket head deformation predictions proposed by the most recent methodology of the latter approach. Furthermore it is attempted to derive corresponding closed-form equations through 3D finite element analyses, taking into account the frictional behavior and the possible separation between the laterally loaded rock socket and the surrounding rockmass.

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