EFFECT OF FREEZING AND THAWING ON RESILIENT MODULUS OF A GRANULAR SOIL EXHIBITING NONLINEAR BEHAVIOR

Abstract

Freeze-thaw cycles experienced in areas of seasonal frost can cause wide variations in the supporting capacity of subgrade materials. The U.S. Army Cold Regions Research and Engineering Laboratory is currently engaged in a program to assess these variations in a number of soils used in roadway and airfield construction. The complete testing and analysis procedure for one of these test soils is presented. The procedure uses a layered elastic analysis to link laboratory and field test results. The component materials of experimental road and airfield sections are evaluated in laboratory repeated-load triaxial tests, and the resilient characteristics are determined as a function of imposed stresses, soil moisture tension, dry density, and temperature. Repeated-plate-bearing and falling-weight-deflectometer tests yield surface deflection basins for the test sections at various times throughout the year. Temperature and soil moisture tension are continuously monitored in the field so that the layers of the test section can be characterized at the time the surface deflections are evaluated. The laboratory results have been verified by using statistical models of material behavior to generate various soil-layer properties commensurate with the prevailing conditons of a given field test. An elastic analysis performed by using the layer properties thus obtained and a surface deflection basin measured in the field test have shown, in general, good agreement. A technique is discussed whereby a single soil specimen is tested several times to determine the resilient properties at various levels of soil moisture tension. The computer analysis is discussed, and actual and calculated deflection basins for several points in time are presented. (Author)