Two field test sites were constructed to monitor the behavior ofslab-on-ground foundation models constructed over expansive soils and the change in soil moisture conditions as a function of climate. One site was constructed in a dry climate (amarillo) and the second site in a relatively wet climate (college station); both sites were monitored monthly for 3 years. Immediately following construction ofthe amarillo site, a 3 year drought ended and the subsequent 3 years were much wetter than normal. Because of the increased soil moisture content, the east end moisture cells stopped working, but the psychrometers on the west end of the slab model worked well over the full study period. Similarly, a 1 1/2 year drought at college station ended the month following site installation and the whole site experienced a general heave of the soil surface, including the slab model. The site continued to experience above average rainfall for approximately 24 months, after which a new period of drought began. Duringthe wet period, nearly all of the 84 moisture cells stopped workingbecause soil conditions were too wet, and more and more of the 160 psychrometers failed to yield suction readings as the study period continued. Fewer than 20 of the psychrometers were yielding readings by the end of the second year; however, the number of instruments providing readings had increased to more than 50 during the drought ofthe third year of the study. This paper appears in transportation research record no. 1277, Modern geotechnical methods: instrumentation and vibratory hammers 1990.
Abstract