Field investigations of negative friction forces in thawing soils

Conclusions

• 1. The negative friction forces can be estimated by calculation with the use of the Shvedov-Bingham equation of deformation of a viscoplastic body on the basis of the results of pull-out testing of an experimental foundation with preliminary thawing of the frozen ground around this foundation.

• 2. The negative friction forces exceed the ultimate shear strength of the thawed soil on the skin surface of the foundation and depend on the rate of mutual movement of the thawing soil and foundation.

• 3. In connection with the decrease in the rate of thawing of permafrost under a structure with the course of time and the increase of the depth of thawing, the effect of negative friction forces should be checked for the most unfavorable combination of these parameters.

• 4. The minimum values of the negative friction forces obtained in experiments for conditions of the movement of the thawing front parallel to the axis of the pile or support exceed by a factor of 2–3 their value set by the standards [1, 2].