The influence of contact area on the deformation of chalk

Chalk rock masses contain natural discontinuities that are largely parallel and perpendicular to the ground surface. In terms of foundation loading. i t is the normal deformation of the horizontal discontinuities, which are of particular interest. This paper considers the influence of discontinuity c ontact area on the deformation behaviour of chalk. A suite of unconfined co mpressive strength tests is described, which comprises an intact specimen a nd five discontinuous specimens. The contact area at the discontinuity rang es from 57% of the initial cross-sectional area of the specimen to 17% cont act area. The deformation processes are modelled analytically and the exper imental results are compared with the predicted values. The experimental re sults show excellent agreement with the proposed model and identify a criti cal contact area, between 44% and 51%, which determines the mode of deforma tion behaviour.