The Influences Of Moisture Migration On The Mechanical Properties Of The Subgrade Soil

The road embankment moisture occurs migration in the service period due to the change of climatic conditions, it is easy to lead the humidity variation inside the embankment state.thereby affecting the road performance and there will be serious diseases like partial settlement?embankment frost boil and other embankment diseases. The moisture migration induce embankment performance degradation in service is a important change which we must be faced about the construction, operation and maintenance durability embankment. For this problem, this study combined with the existing experimental data in the literature, and used the methods of laboratory testing and theoretical analysis to explore the evaluation of embankment equilibrium moisture content caused by climatic conditions, the differences between compaction and modulus of subgrade soil in compaction control and the influence of moisture migration dry and wet path on embankment compacted soil.The main contents and conclusions were drawn as follows:(1) Analyzed the measured data of moisture content from existing literature, explore compacted soil embankment equilibrium moisture content variation with climatic conditions; and discussed the relationship between precipitation?evaporation and embankment equilibrium moisture content; Consider the impact of climate change in the season, this study use monthly precipitation/monthly evaporation as the basic calculation factor to get the relationship between monthly precipitation/monthly evaporation and embankment equilibrium moisture content, and give a experience formula based correction climate index to evaluate the subgrade soil equilibrium moisture, and using the measured data in the literature to verify the reasonableness of the empirical formula.(2) Combined measured results of shear modulus with compacted soil moisture content in literatures and complement experimental data, this study investigate the effect of moisture content and the degree of compaction on the compacted soil shear modulus, and determine the difference intrinsic link between moisture content corresponding to maximum degree of compaction and optimum moisture content corresponding to the maximum shear modulus. There is a critical compaction between subgrade soil shear modulus increases with and compaction at high moisture content, moisture content corresponding to peak shear modulus is slightly less than the optimum moisture content corresponding to maximum dry density. Compacted soil shear modulus increases first and then decreases with the increasing of consistency. The higher the clay content of the soil, the more suitable for compaction in a dry state.(3) Based on different initial moisture content of wet and dry processes and experiences of different samples of unsaturated soil moisture constant moisture content triaxial test data. The influences of the factors including the moisture content, drying or wetting process, confining pressure and void ratio, on the soil shear modulus were analyzed. There is a good exponential relationship between shear modulus and sample water content. For samples with the same moisture content, shear modulus values in descending order as follows:a sample with the drying process, a sample without wetting and drying process and a sample preparation through wetting. when the compaction of subgrade soil in the wet side of compaction curve, it is effective to reduce the performance degradation of subgrade soil when moisture migration during embankment service period.