Behaviour of joints containing clay infill under constant normal stiffness, with and without bolting

The shear behaviour of bolted and non-bolted joints containing infill material was studied under the constant normal stiffness condition. More than 40 sawtooth-shaped samples having an asperity angle of 18·5° were tested. The shear behaviour of bolted and non-bolted joints containing infill material, up to 7·5 mm in thickness, was studied under various initial normal stress levels between 0·13 and 3·25 MPa, at a constant strain rate of 0·5 mm/min and a constant stiffness of 8·5 kN/mm. Significant reduction in shear strength was observed when the joint contained a layer of clay infill of 1·5 mm. Bolting contributed to increasing the strength and stiffness of the joint composite, except at large normal stress levels and at high infill thickness. The dilation and overall friction angle for bolted and non-bolted joints were also compared along with stress profiles. At high infill thickness, the shear behaviour under both constant normal load (CNL) and constant normal stiffness (CNS) conditions was found to be similar for both bolted and non-bolted joints, while at low infill thickness the CNL strength envelope plotted significantly above the CNS envelope.