Influence Mechanism Of High Backfill Area On Underground Structure During Construction

As a mountainous country in China,with the development of urbanization,buildings built on mountains are becoming more and more common.However,the amount of backfilling in mountainous buildings affected by topography is large.Under the requirements of schedule cost,one side of the underground structure is often affected by large unbalanced earth pressure,especially for projects with post-settlement pouring zones,The impact is more obvious.In recent years,there have been many cases of structural quality accidents caused by the construction of high-filled areas,but there has not been enough research on this to guide actual projects.Therefore,this paper used the ABAQUS software to study the distribution of high fill pressure of the structure with post-poured zone based on actual engineering modeling.At the same time,the working conditions and component sizes are changed to further explore the impact on the structure.Finally,the factors affecting the high fill are sorted out.Draw the following conclusions:(1)In view of the backfilling conditions of high-filled areas in mountainous areas,the simplified model of the traditional two-dimensional retaining wall can’t be accurately studied.Therefore,this paper uses ABAQUS software to simulate in two stages,first determine the distribution law of the earth pressure on the structure of the high filling area,and then change the working conditions and the size of the structural members for further analysis.(2)Relying on the construction of models in mountainous areas to analyze the distribution of earth pressure on the structure of high-fill areas.The results show that when the joints are fixed,the earth pressure is affected by the deformation of the structure in two concentrated processes,and from the mid-span of the outer wall,there is a void phenomenon that has nothing to do with the soil and the load,so that the earth pressure is distributed symmetrically in the horizontal direction and concentrated in the vertical direction.The law.When the constraints on the Y side or the inner side of the node X are respectively released,although the structural stress and deformation are different,the earth pressure distribution law remains the same.(3)Combining with the law of earth pressure distribution in high-filled areas,further research is carried out by changing the constraint conditions of working conditions and the size of components.The results show that for different working conditions,frame joint constraints and foundation bottom constraints affect the displacement mode of the outer wall and the overall stress distribution of the structure respectively;increasing the fill height under the same working condition has no effect on the base slip distribution,but it makes the displacement distribution More concentrated;compared with backfilling and then unloading directly to the unloading height,the foundation slip is improved,but the effect decreases with the increase of depth.For different component sizes,when the thickness of the raft foundation is increased in a certain range,the displacement amplitude in the X direction of the structure,the foundation slip and the first principal stress peak value are all reduced,and the stress concentration between the structural layers is effectively reduced;the increase in a certain range The overall displacement of the external wall thickness structure decreases,but it has almost no effect on the foundation slippage.The impact on the stress amplitude is more complicated,and the force on the wall column can be adjusted to improve the stress concentration in the area near the beam column of the external wall.(4)To sort out the influencing factors of backfilling in high-filled areas by summarizing the research results.The results show that the design factors include adjusting the size of the components to coordinate the force and strengthening the retaining properties of the basement outdoor wall;the construction factors include the quality of concrete pouring at key locations,reasonable backfilling techniques and closing the settlement zone in advance.