Research On Design Method And Key Parameters Of Water-preserving Subgrade Structure In Rich Water Deep Soft Soil Area

The problem of large deformation and settlement of deep and thick soft soil foundation with rich water is still a common engineering problem in the process of road construction and operation.Although the development of soft soil foundation treatment technology allows the settlement of soft foundation to be controlled to a certain extent,the settlement control of deep soft soil foundation has not yet achieved the desired effect,the destruction of bridges and culvert junctions caused by road settlement in deep soft soil areas and the accumulation of water on urban roads are still problems to be solved urgently in road construction..In order to reduce and control the settlement of roads with rich water and deep soft soil,this paper proposes a design method for water-retaining roadbed structures.Using a combination of literature research,basic experiment and numerical simulation,the influence of each key parameter of the waterretaining subgrade structure layer is analyzed,and the water pressure of the water supply layer and the setting effect of recharge wells in the design were analyzed and discussed,and the mechanism of reducing the road settlement on the deep and thick soft soil by replenishing water to the foundation to maintain the moisture content of the soft soil was systematically studied.The main research content and results are as follows.Firstly,a literature survey was carried out on the current deep soft soil foundation treatment methods at home and abroad and the application of foundation recharge technology in engineering.And this paper summarizes and analyzes the road settlement mechanism and groundwater seepage related theories on deep and thick soft soil foundations,combining with the fact that the road settlement in the wet season is relatively small in the soft base area,the settlement is obvious in the dry season,and a design method of water-conserving roadbed structure is proposed.Secondly,based on the design concept of water-retaining subgrade structure,the laboratory experiment study of uniaxial creep compression under seepage conditions was carried out.Through the analysis of the soft soil moisture content,settlement,and pressure change laws under different axial pressures and external hydraulic loads,it is obtained that under the external hydraulic load,the water content of the upper soil body of the silty soft soil has increased,and the settlement has been reduced.The test results provide basic experimental support for the design of the water-retaining roadbed structure.Thirdly,The numerical simulation method is used to study the influence of the key parameters of the water-retaining subgrade structure on the settlement of the subgrade.Numerical simulation calculations of influencing factors such as the water pressure application method of the water supply layer of the water-retaining roadbed design structure,the width and depth of the two sides of the aquifer,the spacing and length of sand wells,and the weight of embankment filling are carried out.Focus on the analysis of the settlement of road structure,soft soil foundation and soil moisture content with time and space under the conditions of constant water pressure and variable water pressure of the water supply layer,the difference in the mechanism of settling of the upper embankment and the lower foundation by the setting of the water supply layer’s water pressure is obtained,and the corresponding external water head height when the foundation settlement mitigation effect is the best is given.The setting of sand wells will increase the settlement rate of the foundation in the early stage,but it has the effect of supplementing water to the foundation in the later stage,which can slow down the settlement of the roadbed;changes in the width of the aquifer and the depth of burial on both sides have little effect on mitigating road settlement;the use of lightweight embankment filler under the condition of water supply layer can greatly reduce the relative settlement between the road surface and the ground.Finally,numerical simulation analysis of the effect of recharge wells in deep soft soil foundations on reducing roadbed settlement was carried out,and the influence of factors such as the setting method of recharge wells,recharge flow rate and buried depth on foundation settlement,effective stress and changes in seepage field are discussed.