Abstract
When calculating of the moisture transport in concrete of such geotechnical structures as a pile or diaphragm wall, contact with soil is forming the special boundary conditions. If the soil is in the full saturated state, then the Darcy’s law should be used to solve the problem, the boundary condition for which is the water pressure. Otherwise, the Bažant- Najjar model is used, for which the boundary condition is the relative humidity of soil environment at a certain temperature. The soil environment temperature is unique characteristic for each construction area. For Moscow region, the weighted arithmetic mean temperature to the depth of 60 m is 7.3°C. It is proposed to calculate the relative humidity of the soil environment according to the Kelvin capillary condensation equation, in which the suction is calculated using the Mualem-van Genuchten hydraulic model from the degree of saturation. Two well- known sets of hydraulic parameters of the Mualem-van Genuchten model, compiled on the HYPRES and the HYDRUS-1D database from the European soil map texture classes and the USDA textural soil classification respectively, were compared with the measurement results for soil samples classified according to Russian the GOST 25100. The experimental data showed a good approximation to the calculation with a set of parameters obtained on the basis of the HYPRES database. At the same time, the solution with the HYDRUS-1D parameter set showed a poor correlation.
Highlights
Electron scanning microscope photographs with 22x and 11000x magnification [1] and numerous experimental studies show that concrete is a capillary-porous body and the moisture transport in it obeys the corresponding mechanisms
If distribution of moisture in concrete is calculated according to the Darcy's law and the groundwater pressure acts on the one hand, such the pressure will be the boundary condition on the side of the soil environment
The following method is proposed for determining the boundary conditions for calculating the moisture transport in concrete of geotechnical structures
Summary
Electron scanning microscope photographs with 22x and 11000x magnification [1] and numerous experimental studies show that concrete is a capillary-porous body and the moisture transport in it obeys the corresponding mechanisms. Richards [14] uses Darcy's law and the corresponding concept of the total head Ht. Bažant and Najjar [15] created a model for conditions of incomplete water saturation, in which moisture to transport under the gradient of pore air relative humidity h. The boundary conditions for the use of these models correspond to the soil environment such geotechnical structures as piles, diaphragm walls, etc., below we will consider only them. The boundary conditions for the model of moisture transport in saturated concrete according to Darcy's law will be water pressure at the contact with structure, and environmental relative humidity for unsaturated concrete under to the Bažant-Najjar model. The boundary conditions at soil contact with the geotechnical structures can be characterized by such parameters as temperature, the pore pressure and the relative humidity of the environment. We tried to formulate approach for the boundary conditions determination
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