| The problem of subgrade collapse is widespread in the karst areas of southern China,and has shown a high incidence in recent years,which cause many huge economic losses and casualties.At present,the commonly used treatment method is backfill compaction,but it often collapses again after treatment.Geotextile is laid during the backfill compaction process,and its characteristics of reinforcement and filtering are used to achieve both the symptoms and the cure.However,the load transfer mechanism of geotextiles to control road surface collapse is not yet clear,and the conditions for effectively exerting the load-bearing performance of geotextile-reinforced cushions need to be established,which brings difficulties in the choice of laying range and depth.In this paper,through the analysis of typical characteristics of pavement collapse in karst areas,a generalized model of geotextile treatment for pavement collapse is established.Through model tests,numerical simulation and theoretical analysis,the load transfer mechanism of geotextile reinforced cushion is clarified,and the impact of common factors on governance effectiveness for pavement collapse treatment is evaluated.The research results provide new ideas for the treatment of roadbed collapses in karst areas,and are more suitable for small-scale but frequently repeated road collapses or emergency treatment,which have important scientific significance and application value.The following conclusions of this thesis are achieved:(1)It is feasible to control the collapse of karst subgrade by using geotextile,which not only enhances the self-stability of the filling,but also effectively prevents the upward development of the collapse.Its bearing mechanism mainly includes the soil arching effect and the tensioned membrane effect.The synergy of them causes the load in the collapsed area to be transferred to the stable area,which improves the treatment effect.(2)It can be found from the model test that increasing the anchorage length of the geotextile can improve the ability of the vertical load of the collapsed area to transfer to the surrounding stable area and enhance the ability to control the fill displacement;the soil environment underneath needs to be strengthened no matter how deep the geotextile is buried;when the width of the collapse is large and the thickness of the top fill of the geotextile is relatively small,the vertical deformation of the fill decreases in an "integral" manner,and the increase of the collapse width will greatly increase the difficulty of treatment.The reasonable anchorage length of the geotextile obtained by the test is 1.0 times the collapse width.(3)It can be found from the numerical simulation that the insufficient anchorage length of the reinforced body will lead to excessive pulling out or even being pulled out during the collapse process,and the large vertical deformation of the upper fill;The displacement settlement transferred to the surface can be effectively reduced by increasing the height of the upper fill;increasing the width of the collapse is not conducive to the treatment of the collapse,and increasing the stiffness of the reinforced body helps to control the collapse.According to the numerical calculation results,it is recommended that the reasonable anchorage length of geotextiles to control karst collapse is 0.75 times the collapse width,the buried depth is 3?4m,and the treatment collapse width is below 2.5m.(4)Through the geotextile design method for the treatment of karst subgrade collapse proposed in this thesis,the tensile force at any position of the reinforced body in the collapsed area,the position and value of the maximum tensile force of the reinforced body and the calculated value of the reasonable anchorage length in the anchorage area can be easily obtained.It is found through trial calculations that geotextile is more suitable for the treatment of karst collapses with a collapse width not exceeding 2m. |
PDF Full Text Request