Study On The Synergistic Mechanism Of The Existing-New Embankment Pile-Slab Wall

With the increasing number of railway construction projects in China year by year,there will be more and more railway reconstruction projects and new construction projects adjacent to existing railway lines.The existing roads and railways can no longer meet the growing development trend,and it is imperative to broaden the reconstruction projects..For the reconstruction of the existing line and the addition of the second line,the actual project is often limited by regional conditions.At this time,the structure of the new and old combined support appears.At present,the research on the mechanism of the combined effect of the new and old support structure is obviously insufficient,especially the existing-The interaction mechanism of new pile-slab joint support.Therefore,in this paper,based on the existing subgrade support structure of the Zhonglan High-speed Railway,the third and fourth line subgrade widening projects were built,and the finite element software was used to carry out numerical simulation.,conclusion as below:(1)Using Midas GTS NX finite element software combined with actual engineering to carry out numerical simulation and analyze the results.The calculation results of the existing pile-plate wall analytical method and the numerical simulation method are basically consistent,which provides guarantee for the subsequent modeling work,and the overall numerical simulation method has a small calculation result,indicating that the analytical method is more conservative,but the design is too safe Will cause a waste of material usage.The flexural bearing capacity of the anchored piles of the existing pile-slab wall is checked,and the actual value is less than the design value,so that further research can be carried out on the premise that the pile body does not reach damage.(2)In this paper,in order to study the action mechanism of the new and old combined support,two working conditions are designed for numerical simulation,namely,the new pile does not contact the existing retaining plate(non-synergy),and the new pile contacts the existing retaining plate(synergy),Under the condition that the new and old combinations work together,the lateral displacement of the top of the retaining wall of the existing pile slab wall,the bending moment and shear force of the pile body of the supporting pile,and the horizontal displacement of the top of the existing retaining plate have been obtained Significant restrictions.At the same time,under the synergistic effect,the load ratio of the new pile to the existing pile is close to 1: 1,and the load of the new pile under non-cooperative working conditions is less than half of the existing pile,which shows that the collaborative work can ensure the existing pile plate The stability of the wall.Under both working conditions,the distribution of the earth pressure on the back of the wall shows a trend of increasing first and then decreasing along the back of the wall.(3)After adding a geogrid to the subgrade,the vertical settlement curve becomes slower and the lateral displacement becomes smaller.The geogrid shares a part of the load above the subgrade,making the vertical stiffness of the newly filled subgrade larger and restricting the top surface of the new filled subgrade Of settlement.The laying width and number of layers of the geogrid have a certain effect on the treatment effect.When the laying number and width of the geogrid increase,the smaller the difference in uneven settlement of the top surface of the subgrade,and the more the number of layers and the width of the laying The settlement curve of the top surface of the subgrade is slower,but from the economic point of view of material consumption,it should be optimized reasonably.