Research On Osmotic Characteristics Of Red Rock Fillings And The Embankment Stability Under The Action Of Seepage

Red mudstone is a special rock. It has some special characteristics, such as low compression strength, softening, disintegration, dilatability and sensitive to the reclamation compaction degree when meeting with water. With the development of national economy, more and more earth structure was constructed on the red soft rock. With the influence of water-physical properties of red rock, some engineering geological problems appeared such as slope slide, subgrade frost boiling, and embankment seepage. The seepage of water is the critical affecting factor on slope stability. With the background of DK180+460-DK180+640 section of freeway from Chengdu to Nanchong, seepage parameters, free face shape and embankment stability under the action of seepage were studied in the paper.According to the permeability test and self-mastery "L" type model test, the coefficients of permeability in horizontal and vertical direction at different degree of compactions were obtained. Based on the Darcy law, calculating formula for the model was deduced. The results showed that the coefficients of permeability in horizontal and vertical direction decreased when the compact degree increased, which validated the feasibility of the model measuring method. In the same compact degree, the coefficient of permeability in horizontal was larger than in vertical, and the ratio of horizontal and vertical was between one and four which showed the anisotropy of red rock filling induced by construction.Some results were received by FLAC numerical analysis as follows. When the media of model was in isotropy condition, the water head and the length of percolation path, and when the media of model was in anisotropy condition, the ratio of horizontal and vertical coefficient had the relationship with the shape of seepage free face and the seeping position in high wall. The coefficients of permeability and porosity just effect the seeping time when seepage achieved a balance. Research on these results was done by model test which validated the reliability calculated by FLAC software.The stability of embankment in DK180+460-DK180+640 section of freeway from Chengdu to Nanchong was calculated in taking the action of seepage into account or not by FLAC numerical analysis. It showed that when taking no account of the action, the factor of safety was 2.15 which in steady state; when taking the action of seepage into account, the factor of safety was 1.19 which in critical state. If considered some external influential factors such as rainstorm, the embankment would damage. So the action of seepage had a great effect on the stability and it should be considered in the design of embankment.