Study On Moisture Migrate Mechanism In Granite Eluvial Soil Embankment In Damp-Heat Areas

In the southeast coastal areas of our country，they are with high temperature andmore rain in summer, which causes granite eluvial soil widely distributed. With theconstruction of highway enlarging, granite eluvial soil becomes to be one of the mainpacking. During embankment construction and opening the traffic service period,embankment moisture constantly changes influenced by groundwater, precipitation,evaporation, pavement structure permeability, traffic load and so on, which would makethe humidity of the embankment change, and the degradation of the strength andstiffness of the soil, leading to the subsidence of the embankment, pavement crackingand other road disease. Therefore, it is essential to study the rows of moisture transfer ofembankment, and the influence to engineering characteristics of residual soil fromgranite.Based on the above, taking Fujian as an example, we have carried out a systematicstudies on the engineering characteristics of granite eluvial soil when as embankmentpacking in this paper. Using indoor model experiment combine with numericalsimulation, study the raws of moisture transfer in the embankment with capillaryfunction, rain infiltration and the coupled thermal and moisture effect.It used conventional soil tests, suction tests, level soil column suction unsaturatedpermeability tests to determine the physical properties, the relationship between matrixsuction and water content, water diffusivity, unsaturated hydraulic conductivity, therelationship between saturated hydraulic conductivity and the degree of soil compaction.Improved the calculation formulation of thermal parameters, which considers theparticle composition. Obtained the relationship between the suction strength andsaturation of residual soil from granite in different embankment horizon byconventional triaxial tests.Based on the Richard unsaturated flow equation, have the volumetric watercontent as variables, to draw up one-dimensional finite difference code capillary rise ofwater, and use the indoor increased capillary water column test to verify the program,and simulate the impact of the different degree of compaction, initial water content andtemperature on capillary action, and established the different increased height andvelocity of capillary under different conditions and determine the final embankment height of capillary rise of water under the different degree of compaction and initialwater content of soil.Based on the Richard unsaturated flow equation, have the volumetric watercontent as variables, to draw up the one-dimensional finite difference code, and use theindoor one-dimensional soil column infiltration tests and finite element to verify thethese above procedures; we have the negative pressure head as variable,to draw uptwo-dimensional layered embankment finite difference code (ADI) to simulate themoisture migration of embankment on the condition of different rainfall intensity,rainfall calendar time and pavement structure.Based on the unsteady heat conduction equation, they draw up a one-dimensional,two-dimensional finite difference code (ADI), and compared and verified by soilcolumn experiment. On this basis, considering Fujian’s temperature, solar radiation,wind speed boundary conditions, the two-dimensional finite difference code simulatestemperature distribution and seasonal variation of the granite eluvial soil embankment,and analyze on the different degree of compaction, thermal conductivity, volumespecific heat to affect the characteristics embankment temperature field.Finally, considering the effect of the temperature of water movement parameters,ituses the matlab language programming simulate the moisture of embankment migrationin the coupling conditions including rainfall infiltration and capillary water ascent,temperature and capillary water ascent, temperature、rainfall and capillary water ascent,to obtain the temperature field and the moisture field variation of the granite residualsoil embankment in the environmental impact conditions.