Study On Soil Arching Effect And Influencing Factors For High Fill Open-Cut Tunnel Based On Particle Flow Method

The northwestern in China is located on the high altitude area of loess.With the development of the economy in the northwest region and the implementation of the One Belt One Road Strategy of the country in recent years,the road network construction in the northwest region has been continuously improved.The main measure for crossing these barriers through these areas is to cut mountains and fill trenches.As a result,the use of high-filled loess and open-cut tunnel has become more widespread.At present,there are few researches on high-fill loess and open-cut tunnel,which mainly focus on scale model tests in the laboratory and numerical simulations with finite element software.However,these are based on the analysis of continuum theory.In fact,loess is a kind of granular mixture media materials that possesses Physical properties of non-continuous,the use of finite element software based on continuum theory is inconsistent with reality in this research.For this reason,the article carries on the numerical simulation with the software particle flow code,the analysis related conclusions are as follows:(1)Use biaxial tests to calibrate the parameters,and establish a particle assemble model to continuously adjust the contact parameters between the particles so that they have the same or similar mechanical response same as the macroscopic physical parameters.By this way it can obtain the microscopic parameters between the particles.The parameters is appropriate for the model for the high-fill loess open-cut tunnel model.(2)Based on the numerical granular flow model of the high-fill loess open-cut Tunnel,the change law of the earth pressure and the vertical displacement of the particles above the open-cut tunnel is analyzed;the grain size,porosity,and the cross-sectional shape of the open-cut tunnel are discussed.The influence of earth pressure and vertical displacement of loess particles.The results of the study indicate that the soil arching effect does not occur at the top of the open-cut tunnel with high slope-filled loess,and the simulation value of earth pressure at the top of the open-cut tunnel is greater than the theoretical calculation value.Compared to the loess particle size and the soil porosity,The shape of the open-cut tunnel has a great influence on earth pressure at the top of the open-cut tunnel.(3)Through different numerical models of granular flow in loess-filled open-cut tunnel with different forms of slopes,the formation and change process of soil arching and the change law of vertical pressure and particle displacement at the top of open-cut cunnel were analyzed,and loess characters,cross-sectional shape of open-cut tunnel,Influence of Slope Angle and slot width ratio on soil arching effect.The results show that there are many factors affecting the soil arching effect,and the formation and location of soil arches under different influencing factors are also not the same,and the impact on the top earth pressure of open-cut Tunnel is also different.Among the above-mentioned influencing factors,the cross-sectional shape of open-cut tunnel,slope angle and groove width ratio have the most significant effect on the soil arching effect in open-cut tunnel.(4)By comparing the pressure transfer of high-fill loess and open-pit soil under sloped and non-sloped conditions,the results show that the addition of slopes is conducive to the generation of soil arches near open-cut tunnel,which can effectively share the top earth pressure of open-cut tunnel due to the effect of soil arching.The pressure causes the top earth pressure of the open-cut tunnel to be less than the theoretical calculation.