Prediction and Control Method for Deformation of Highway Expansive Soil Subgrade

In order to provide reference for design and construction of expansive soil subgrade,methods for deformation calculation,compaction control and stiffness compensation of expansive soil subgrade were studied.One-dimensional swelling tests on three expansive soils were conducted.Based on the test results and moisture equilibrium rule of expansive soil subgrade,a new mathematics model for swelling and a method for deformation calculation of expansive soil subgrade were put forward.For the limitation of routine compaction control method on the expansive soil subgrade,a method for compaction control aimed at the maximum bearing capacity of expansive soil subgrade was proposed.According to the deflection equivalence of elastic double layer and elastic half space,a design method for stiffness compensation of expansive soil subgrade was suggested.The results show that the mathematics model can well reflect the ultimate swelling property and swelling deformation of expansive soil.Water content corresponding to the peak of variation curve of California Bearing Ratio with initial water content is close to naturalwater content of expansive soil and equilibrium water content of expansive soil subgrade.For compact expansive soil subgrade at this water content,the swelling of subgrade can be well controlled and the enough bearing capacity can be ensured.The stuffiness of expansive soil subgrade can be effectively increased to meet the requirement of pavement by filling nonexpansive soil in a certain thickness on the top of expansive soil subgrade.