Interaction of matric suction and net stress on a highly pressure grouted soil-cement interface

Nowadays, grouting pressure is considered as an important issue as it provides better interface strength than gravity grouting in case of cast in situ soil-cement grout interface, like soil-nail and soil-pile interface. In the present study, a series of interface direct shear tests is performed on highly pressure grouted soil-cement interface under different matric suctions and net stresses. The experimental results indicate that grouting pressure, matric suction and overburden stress have interactional significant influence on the interface behaviour of soil-cement interface. The shear strength increases with net stress at both saturated and unsaturated conditions for pressure grouted soil-cement interface. Similar to soil, the interface shear strength envelopes for a given suction are approximately linear. The apparent interface friction angle and adhesion intercept increase with matric suction. As compared with gravity grouted interface, the apparent interface friction angle decreases for higher pressure grouting at different matric suctions. Also, the strength of highly pressure grouted interface is greater at lower suction range, but lower at higher suction range.