Thermally-Induced Settlements for Heat Generating Structures on Unsaturated Soils

In assessing the probable settlements of a heat generating structure on unsaturated soil three stress state variables that are of key importance are (a) temperature, (b) net normal stress, and (c) soil suction. Neglect of or substantial error in evaluation of any one of these three variables can result in substantial error in the estimation of thermally induced soil settlement. It is possible to obtain upper bound estimates of the thermally-induced strains by employing a low-cost laboratory test program utilizing ordinary convection drying ovens. However, if the upper bound values of strain and associated settlement are unacceptable, then it is necessary to use unsaturated soils testing equipment capable of measurement and control of soil suction, net normal stress, and temperature. The primary objective of the laboratory testing program is to obtain the best estimate of field response by using undisturbed soil samples and/or compacted fill samples, as appropriate, and subjecting the specimens to field-appropriate unsaturated soil stress state variables. This practice-focused approach for obtaining thermally-induced unsaturated soil settlements is demonstrated through a laboratory testing program applied to a soil profile.