Research On Anchoring Function Of Geotextile In Controlling Collapse Of Karst Subgrade

In recent years,subgrade collapse in covered karst area has been a high incidence,Its occurrence cycle is short,the collapse process is rapid,and the concealment is high,which is obviously harmful.The existing treatment methods after the collapse of the karst roadbed are mostly backfilling and compaction,which treats the symptoms but not the root cause,which is likely to cause secondary collapse.Geotextiles not only have a reinforcing effect,but also have filter characteristics.When the karst roadbed collapses,laying geotextiles can improve the overall stability of the fill.At the same time,it uses its filter characteristics to ensure that the backfill is permeable and impermeable to reduce soil particles.Through,effectively reduce the possibility of the treatment area collapse again.At present,the research work and engineering application of the turn-up method at the free end of the reinforcement are generally concentrated on slopes,reinforced retaining walls,and pile-supported reinforced embankments.The wrapped-back geotextiles are relatively more effective in treating karst subgrade subsidence.less.In this paper,combined with the actual collapse engineering scale model test,the geotextile free end wrapped-back and non-wrapped-back of the impact on the treatment of karst roadbed collapse was studied,revealing the anchoring mechanism of the geotextile free end wrapped-back,and passed The pull-out test and numerical simulation analyze the influencing factors of the pull-out force when the free end of the geotextile is wrapped-back.The main research work and conclusions are as follows:(1)Through indoor scale model tests,it is found that geotextiles have a good effect in treating the collapse of the covered karst subgrade,which can enhance the overall stability of the subgrade,reduce the displacement of the filling in the collapse area,and prevent the collapse from further expanding.The load-bearing mechanism includes soil arching effect and film pulling effect,and the two work together to transfer part of the load from the upper part of the collapsed area to the stable area;(2)When the geotextile is used to treat the collapse of the covered karst subgrade,the wrapped-back method is used,which is equivalent to better anchoring the free end of the geotextile in the fill,which enhances the interaction between the geotextile and the fill,and improves the performance of the geotextile.Anchor force.The greater the anchoring force,the more difficult it is for the geotextile to be pulled.The anchoring effect further limits the deformation of the geotextile in the collapsed area,thereby preventing the soil above the collapsed area from expanding upward,improving the treatment effect,reducing the laying range,and reducing the treatment cost;(3)The results of the pull-out test show that the pull-out force increases with the increase of the pull-out displacement,and the normal pressure and the tensile strength of the bar have a significant influence on the pull-out force.Under the same flat length,the drawing force when the free end of the geotextile is wrapped-back is significantly higher than that when it is not wrapped-back;(4)The pull-out test model was established using finite element analysis software,and the numerical simulation results were compared with the test results to verify the reliability of the numerical simulation.The numerical simulation results show that the length of geotextile leveling,normal pressure,wrapped-back height of geotextile,wrapped-back length of reverse geotextile,filling parameters,reduction coefficient of strength of reinforced soil interface,etc.will have certain influence on the pulling force of geotextile when the free end is reversed.