Experimental study of the effect of submersion time on the strength development of freeze bonds

Freeze bonds have been found to influence the mechanical properties of ice rubble and ridges, and it is therefore important to study the fundamental physical properties affecting these features. The shear strength of freeze bonded ice blocks has been investigated through a series of asymmetric four point bending (AFPB) experiments for different submersion times and initial ice temperatures. Ice blocks were subject to a confinement of 25 kPa and were sheared at an actuator rate of 5 mm/s. Effects of submersion time on shear strength of freeze bonds was investigated by varying the submersion time from 1 min to 14 days, for two initial ice temperatures of -18 degrees C and -10 degrees C. Shear strength values measured are believed to be dominated by two concurrent mechanisms. Thermal bond growth is the first mechanism, where an initial increase in strength with submersion time is observed, reaching a peak after four (4) minutes of submersion time and gradually decreasing to a constant value. Sintering-creep bond development is the second mechanism that significantly influences the bond strength in submersion times longer than 24 h, where the strength increases and eventually asymptotes to the strength of solid ice. An empirical equation which estimates the bond strength as a function of submersion time and initial ice temperature is developed.