The use of geosynthetics to mitigate frost heave in soils.

摘要

A capillary barrier is a layer of coarse, porous material placed in soil above the water table to prevent unsaturated water flow across the layer. Capillary barriers reduce frost heave in soils and pavement systems when they are located between the water table and the freezing front. Due their large pore sizes, geotextiles and geocomposites are capillary barrier candidates. The objectives of this research were to determine (1) the range of soil and thermal conditions under which geosynthetic capillary barriers can reduce frost heave, and (2) geosynthetic properties required for capillary barrier performance. Based on estimates of heat flux in the field and freezing test results, capillary barriers should be beneficial in most cold regions. The frost heave of soil specimens with and without geosynthetic capillary barriers was examined through freezing tests of frost-susceptible soils.; Theory, capillary rise, and water retention tests showed that moist geotextiles that contain soil fines take on and transmit water more easily than geotextiles as received from the manufacturer; this was verified by freezing tests. However, moist geocomposites containing soil fines effectively cut off frost heave in highly frost-susceptible soil when the soil above the capillary barrier was 75% saturated or less, but they did not work when the soil above them was more than 80% saturated. The geocomposites consisted of combinations of two different geotextiles and two different nets, and the results were not product dependent. Filtration tests verified that the geotextiles used as filters on the geocomposite performed adequately as filters in a frost-susceptible soil.; Geocomposites are recommended for further study as capillary barriers in pavements. Future work should study the performance of geocomposites subjected to a variety of conditions, including two- and/or three-dimensional freezing and infiltration of water from above. Soil water retention functions and the unsaturated hydraulic conductivities of geocomposites should be determined; this information could be used in existing models to determine the influence of capillary barriers on the frost heave of pavements.