The Sensitivity Analysis Of Water Level Amplitude’s Action Effects On The Underground Frame Construction

Mountain river is entrenched before urbanization,but after that,there exists Large elevation difference between the natural river and the neighboring area.Based on the multi-goals of the flood control、water ecolog and so on,this paper puts forward the plan for the construction of the double channels which is fit for the mountain cities:The upper river in the form of the open channel and The lowwer river in the form of the burried culvert.Among them,the culvert is deeply buried underground in the process of the flat,its mechanical properties and structure design is particularly important due to the difficult maintenance and serious accident consequence.Therefore,it is very important to grasp the structural characteristics of the structure,and it can effectively reduce the rik_s of accident when coansidered in the design phase.The condition of the groundwater enviroment around the culvert will change radically with heavy rainfall because of the terrain and seepage characteristic of the backfilling area,if the soil is hoilding water for a long time,which is to the detriment the structures of this district.Therefore,the water is considered to be discharged into the lower channel through the culvert permeable channel.At this point,the structure will encounter groundwater level changes in this situation.The current specifications usually reduces or uses the maximum possible water level when calculating water loads,however,the stress substance of the culvert is coupling of seepage field and stress field of surrounding soils under the action of co-deformation in this process.Therefore,research on mechanical characteristics of deep buried frame structure under the action of fluid-structure coupling effect which comes from the change of underground water level has an important engineering application value.In this paper,the three dimensional finite element model of the underground frame structures is built based on a practical engineering and the main research content is as follows:(1)Deducing the stress equilibrium equation and the unsteady saturated seepage flow continuity equation which respectively are the control equation of stress field and seepage field on the basic of principle of effective stress and the darcy’s law,and gives the matching definite condition.Getting the coupling mathematical model of porous media soil’s seepage field and stress field according to the influence of the interaction oftwo fields,the finite element matrix format of coupling condition and solving way is also given.Expounding the key points in the establishing process of 3D finite element model,and giving the model parameters rely on the geological exploration report of the engineering example and the corresponding experimental results.(2)Simulating the stratified backfill construction process,which confirmed the stress concentration phenomeno on the top of the culvert,this is the unique form of the load acts on the deep buried framework structure.Simulating the drainage and consolidation process with levels falling,the growth of its effective stress is jointly contributed by the obvious water level drop(Major),the obvious water level drop process,drawdown of culvert’s side water level at the three stage of the overflow of the pore pressure and the stress concentration caused by the settlement difference,at this point,the rate of decline of water is not applicable to measure the trend of internal force change.The process of consolidation and drainage makes the settlement and the internal force increase,and the rik_s of structural damage is correspondingly increased.(3)Backfill materials creat a greatly influenced on the load and internal force response by its property-elastic modulus “ E ” and permeability “ k ”,regardless of the culvert back backfilling,culvert side drainage engineering measures,there is only exist earth-rock mixture and under the role of one parameter,The higher the elastic modulus E_m and the smaller the permeability coefficientK_m of the higher permeability level of the backfilling,the better the structure in the field.On the other hand,Bring in the material of Sand Gravel backfilling of the culvet back,its elastic modulus isE_s and its permeability coefficient isk_s.under the role of multiple parameters,The smallerE_m is,the largerE_s is,K_m is the larger than and close tok_s and the smallerk_s is,the better of the structure.Among them,E_m is more sensitive thanE_s andk_s is more sensitive thanK_m in the same range of variations.In general,the application of corresponding engineering measures in the area of the culvert side’ soil can effectively reduce the magnitude of the load and the internal force,and be more economical and efficient at the same time.