Model Test And Numerical Simulation Of Earth Pressure With EPS Boards Load-Reducing For The High Fill Open Cut Tunnel

With the development strategy of the western region and the accelerated process of urbanization,the demand for urban construction land is increasing,and the land resources are becoming more and more valuable.In construction on the Loess mainly western mountainous cities and regions,in order to meet the needs of the development of integrated transport hub and urban planning,inevitably will be a lot of mountain cut to fill out the ditch,it will appear more and more high backfill construction of open cut tunnel.And the research on high fill structure of soil stress and unloading is mainly pipe culvert structure,few studies of open cut tunnel structure of soil stress and unloading.Therefore,the research on high backfill soil pressure distribution of open cut tunnel structure and unloading principle and influence factors becomes more theoretical value and practical significance.This paper systematically studies the laws and influence factors of EPS board unloading high filling open cut tunnel.The earth pressure variation of high filling open cut tunnel of different characteristics EPS boards unloaded obtained b y the indoor model test.And combined with the finite element numerical simulation,the mechanism and influencing factors of the unloading of EPS boards are analyzed.The main conclusions are as follows:(1)When filling height is low,with the filling height increases,the density of the EPS board is smaller,and the roof of earth pressure unloading rate is higher.But with the increase of the filling height,the low density of EPS board s quickly hardening,can’t continue to deformation,but high density EPS boards still have the deformation of the surplus amount,can continue to deformation,and continue to play the role of unloading.With the increase of filling height,the thickness of EPS boards is large,the smaller the vertical earth pressure.But it is not favorable on the unloading without limit to increase the thickness of EPS boards.Only when the EPS boards yield,its effectiveness can be fully reflected.Therefore,the density and thickness of the EPS boards should be selected according to the he ight of the fill and the unloading of the target.(2)The finite element calculation results are in agreement with the experimental results.To prove the feasibility and accuracy of method of finite element numerical simulation of high embankment EPS boards unloading tunnel.The stress cloud images can be seen clearly,After the EPS boards unloading,the inner and outer columns form a significant "soil arch effect".The soil pressure of the inner soil column is transferred to the outer soil column and the slope through the soil arch,and the purpose of the unloading is achieved.(3)The influence factors of EPS boards unloading high fill open cut tunnel,the distribution of soil pressure is closely related to the form of open tunnel structure;The cohesion of filler property has little effect on the soil pressure,and the increase of internal friction angle will lead to the decrease of soil pressure;Laying EPS boards between the span of open cut tunnel more reasonable and effective;Different fill height corresponding to the best EPS boards laying position is different.Therefore,it should be based on the height of the soil to select the appropriate EPS boards laying location;In a certain range,the decrease of the foundation stiffness of open cut tunnel and the increase of compression modulus of lateral fill will lead to decrease the earth pressure coefficient.Therefore,the appropriate reduction of foundation stiffness of open cut tunnel and increasing lateral fill compression modulus can relieve the earth pressure concentration of open cut tunnel.