Experimental And Simulation Study Of Seepage Behavior In Porous Permeable Bricks

Permeable bricks are of typical porous media in green architecture fields. They are also of relatively good air and water permeability and environmental friendly material. Just like other porous materials, the fluid immigration in porous brick is greatly affected by pore structure. Therefore, it is necessary to link physical process on pore-scale and average properties on macro-scale together.In this thesis, by means of X-ray CT technology, experimental tests and computer simulation technology, some experimental and simulation works on the porous bricks’ pore characteristics, permeability performance and the relation between microstructure and macroscopic percolation are conducted.Firstly, the pore structure characters and permeable performance of three types of porous bricks including pervious concrete, ceramic bricks and clay bricks are analyzed. Some results are given as follows:(1) The pores in pervious concrete mainly is micropore and macropore. There are a lot of micropores and they tend to be isolated. Fluids can’t flow through such pores when water seepage in porous media. Macropores with good connectivity provide the main channel. Generally speaking, the pervious concrete is of high permeability and the permeability coefficient is in the range of 0.01-0.06cm/s.(2) Ceramic bricks have high porosity and high connectivity, and the permeability is about 0.01cm/s.(3) The pores in clay brick with small diameter is of poor connectivity which results in good water retention and poor permeability. Clay brick is not suitable as permeable pavements in practical applications.Secondly, the effects of the stability of seepage are analyzed. The seepage in pervious concrete is stable and not affected by gas adsorption. Moreover, transitory sulfate attack won’t influence channel in concrete materials. Ceramic bricks and clay bricks are both sintered bricks which have good chemical stability. However, pores in sintered bricks are very small. Dissolved gas in water is easier to be adsorbed, thereby inducing flow passage jamming.Regularly packed media and stochastic model are established to conduct micro-scale seepage simulation. A study on percolation mechanism in response to single pressure gradient was conducted. Through the parametric analysis, it is found that in regularly packed porous media the effect of packing form on permeability, to some extent, can be neglected with comparison to those of size and void ratio. The technical route of “construction algorithm”, “processing image”, “numerical solving” and “results analysis” for stochastic models are established. Numerical analysis is conducted to estimate the effect of random pore structure characteristics on the permeability. Finally, an acceptable model is presented to predict the permeability of pervious concrete and ceramic bricks, although it is still not suitable for clay bricks.