| With the rapid development of national economy and the full implementation of the western development strategy,the large-scale development trend of land in collapsible loess mountainous area is clearly highlighted,and a large number of high-speed railway subgrade projects in collapsible loess area will emerge.The engineering characteristics and stability of this kind of foundation have attracted the attention of scholars and engineering technicians.By systematically summarizing the relevant research results of collapsible loess at home and abroad,this paper studies the key problems such as the engineering characteristics of collapsible loess,the structure of collapsible loess,the deformation and strength characteristics of loess,the dynamic characteristics of collapsible loess,and the treatment of collapsible loess foundation:(1)Summarizing and analyzing the research history and current situation of collapsible loess at home and abroad,the dynamic characteristics of loess and the treatment method of collapsible loess foundation.The soil sample collection points of loess are comprehensively selected,and the indoor compaction test,consolidation test and collapsibility test are carried out.Through the analysis of the test results,we have a deep understanding of the Loess parameters of the collapsible site in Taiyuan area of Datong Taiyuan high speed railway.(2)The experiment of loess dynamic characteristics shows that the dynamic cohesion c_d of loess in Taiyuan decreases with the increase of water content w.Before the plastic limit moisture content,the dynamic cohesion changes rapidly with the moisture content;After the plastic limit moisture content,the dynamic cohesion changes slowly with the moisture content;Dynamic friction angle of loess in Taiyuan Areaφ_d decreases slowly with the increase of water content w,but the change is not great.Therefore,it can be considered that the dynamic friction angle of loess in Taiyuan is hardly affected by water content.Through the study of loess vibration subsidence and deformation,it is found that when the water content is 5%,Taiyuan loess sample has been damaged before reaching the critical dynamic stress of vibration subsidence,which is non vibration Subsidence Loess.It can be further inferred that the Loess in Taiyuan is non vibration collapsible loess when its water content is w≤5%,and vibration collapsible loess when its water content is w>5%.(3)Through finite element numerical simulation,the dynamic response of different treatment measures in the foundation treatment section of Taiyuan station in the collapsible loess section under the action of train vibration load is studied.It is found that the bearing capacity of the reinforced collapsible loess area has been significantly improved.Under the action of train dynamic load,the deformation of collapsible loess foundation fully meets the requirements of train operation.(4)The common engineering treatment measures of collapsible loess foundation are compared and analyzed,combined with the results of finite element numerical simulation,and compared with the dynamic response analysis of collapsible loess.Determine the economic and reasonable treatment method of collapsible loess foundation with good treatment effect. |
