Dynamic Humidification Model Test And Stability Study Of Coarse Grained High Embankment

In the southern part of China,the construction of expressways will inevitably cross the mountainous hills.Coarse-grained soil consists of earth-rock mixture with particle size d=0.075?60 mm particle content(mass ratio)greater than 50%.It has engineering properties such as high porosity,strong water permeability,high compressive strength and high compaction density.A number of subgrades were used for high-filling construction of coarse-grained soil as a filler,forming a large number of coarse-grained soil high embankment projects.However,under the combined influence of long-term vehicle dynamic loads and rainfall factors,rheological phenomena often occur in coarse-grained soil fillings during operation period,which reduces the design life of embankments.In view of this,this paper is based on the National Natural Science Foundation of China:esearch on service performance evolution and state control technology of high coarse-grained soil embankment under dynamic wetting effect(51678073).The dynamic humidification model test of coarse-grained soil high embankment was carried out,and the seepage characteristics of coarse-grained soil high embankment under dynamic humidification were analyzed.According to the test results,the dynamic response and stability evolution of coarse-grained soil high embankment under dynamic humidification were simulated by numerical software.The main conclusions of this paper are as follows:(1)Based on the similarity theory,the similar relationship between the embankment model and the prototype was constructed.The embankment model box,the indoor rainfall spraying device and the vehicle dynamic load simulation device independently designed and manufactured by the independent research and development were used to carry out the dynamic humidification model test of the indoor coarse-grained soil high embankment.It could reflect the seepage characteristics of coarse-grained high embankment under dynamic humidification.(2)The results of dynamic wetting model test show that:Under the action of dynamic wetting,the wetting front first forms on the surface of embankment slope,and gradually extends from the surface of slope to the inside of slope.Under the influence of vehicle dynamic load,the wetting front expands at the top of slope at a small rate and at the foot of slope at a large rate.Under the influence of the evolution law of wetting front,with the increase of rainfall duration,the pore water pressure at monitoring points of embankment slope decreases gradually,the volume water content increases gradually,and the stress before embankment slope increases gradually,and the stress at the surface layer at the foot of the slope increases rapidly.(3)According to the seepage results of dynamic wetting model test,the soil-water characteristic curve of coarse-grained soil was fitted,which made the seepage numerical simulation and dynamic wetting model test combined,and ensured the consistency of seepage characteristics of numerical simulation and dynamic wetting model test,and provided seepage field for stability calculation of high embankment of coarse-grained soil under dynamic wetting.(4)Numerical results of time-varying stability of embankment:When the vehicle load moves to a certain point,the vertical dynamic stress response at this point is most obvious;At the initial stage of load loading,the subgrade soil was mainly elastic strain.With the increase of load loading times,the residual plastic strain gradually accumulated,and the subgrade soil gradually produced larger settlement displacement;The plastic zone of the coarse-grained soil high embankment is first formed at the top and the slope of the embankment.With the gradual increase of the penetrating force,the plastic zone gradually expanded into the interior of the slope to form the penetrating zone.Affected by the evolution law of the embankment wetting front and the penetrating force,the change law of the embankment safety factor in the whole research period is divided into three stages:slow reduction,rapid reduction and slow recovery.