Study On The Decay Mechanism Of Soil-geotextile Filter System Under The Action Of Different Factors

Slope drainage pipes with geotextile-wrapped PVC plastic pipes are an important component of underground drainage systems.They are used for deep slope drainage and play a crucial role in maintaining slope stability.However,in practical engineering,mechanical clogging of the geotextile-wrapped pipes due to hydraulic gradients,soil particle content,and changes in the permeability of the anti-filter layer often occurs,which affects the overall safety of slope engineering.To investigate the permeability clogging mechanism of soilgeotextile anti-filter systems under different factors,the gradient ratio(GR)test device in existing standards was improved and supplemented with experimental methods.Permeability tests were conducted under three hydraulic gradients,three soil particle contents,and four geotextile specifications,and the particle transport behavior was further revealed through numerical simulation.The main research work and results of this paper are as follows:(1)The indoor gradient ratio test was used to analyze the influencing factors of the antifilter system.The permeability of the soil-geotextile anti-filter system was inversely proportional to the soil particle content and geotextile unit area mass,and directly proportional to the hydraulic gradient.Compared with the effect of hydraulic gradient,soil particle content had a greater clogging effect on the anti-filter system,with a decrease in permeability coefficient of more than 30%.However,the hydraulic gradient was more likely to change the structure of the anti-filter system,affecting the trend of GR value changes.Further analysis showed that when the hydraulic gradient was small,selecting a geotextile with a larger pore size could increase the permeability of the anti-filter layer and reduce the degree of clogging,while under large hydraulic heads,the stability of the anti-filter layer could be improved by reducing the pore size of the geotextile.(2)The quantitative study of particle transport was conducted using the secondary screening test.It was found that when the hydraulic gradient was small,the geotextile and adjacent soil layers had the highest soil particle content,which was 10% higher than the initial soil sample,while the soil particle content of other soil layers was lower than the initial state.When the hydraulic gradient was large,the soil particle content of layer II-1 was 5% higher than the initial soil sample,and the coarse particle skeleton near the geotextile was further compressed to form a void layer,which formed a natural filter layer in the protected soil layer.The soil far from the geotextile migrated to the "natural filter layer",causing internal clogging of the soil.The improved geotextile clogging test device and secondary screening test can further monitor changes in soil permeability and quantitatively analyze the soil particle content of each layer,which can be used as a method to measure the range and degree of clogging of the soil-geotextile anti-filter system.(3)The particle transport analysis was conducted using discrete element numerical simulation.It was found that the numerical simulation was consistent with the indoor test for the particle transport behavior under different soil particle contents and hydraulic gradients,and could further analyze the permeability clogging of different soil layers.The more soil particle content in the model,the more soil particle content on the geotextile surface,and the more severe the clogging of the soil-geotextile anti-filter system.The larger the hydraulic gradient,the more fine soil particles migrated from the top,and the less severe the clogging of the geotextile.