Study On The Soil-arching Evolution Pattern And Earth Pressure Theory Of Rigid Load-shedding Culvert

In this paper,the rigid load-shedding culvert（LSC）underneath the embankment fill is taken as research object.Not only the rigid LSC structure can reduce more vertical earth pressure on the LSC crown,but decrease the horizontal earth pressure on the LSC sidewalls.However,when the reasonable thickness of EPS recognized by existing research is installed on the crown of the rigid LSC,the soil arching evolution pattern of embankment fill above the crown of the rigid LSC has not been investigated.Moreover,in the existing calculation theory of the vertical earth pressure on the culvert crown,the linearly elastic-perfectly plastic model is closer to the shear stress-strain model of embankment fill on the slip surface above the crown of the rigid LSC is not considered.In view of the above two shortcomings,the soil-arching evolution pattern and earth pressure calculation of the rigid LSC were investigated in the text.Firstly,based on the reasonable thickness of EPS recognized by existing research was installed on the crown of rigid LSC,the soil-arching shape and the variation of vertical earth pressure on the crown of rigid LSC under different load shedding hole（LSH）width/load shedding block（LSB）width（D/w）ratios were investigated.Numerical simulation found that the differential settlementΔS the between embankment fill over LSH and the embankment fill over LSB is the main factor controlling the soil-arching shape of embankment fill above the crown of the rigid LSC,and vertical earth pressure on the the crown of rigid LSC increases with the increasing D/w ratio.Secondly,according to the settlement model test of similar soil culvert with aluminium bar,the soil-arching evolution patterns above the crown of rigid LSC under different D/w ratios were investigated.When the D/w=1,tower-shaped soil-arching evolution stage appears in embankment fill above the LSC crown.Moreover,when the slip surface in embankment fill above the LSC crown is in vertical state under the condition of the D/w=1、2、3,the relative differential settlementΔS/D to be greater than 0.07、0.08、0.09,respectively.Finally,according to the limit equilibrium method for bulk materials,considering the fact that the linearly elastic-perfectly plastic model is closer to the shear stress-strain model of embankment fill on the slip surface,this paper proposed an analytical method to calculate the vertical earth pressure on the crown of the LSC underneath the embankment fill.It can determine the corresponding position on the slip surface when the shear stress of the embankment fill on the slip surface just reaches the limit value.The calculation examples are presented and compared with the numerical results of FLAC^2D,which demonstrates that the difference between the proposed analytical and the numerical results is less than 10%.The results show that as the internal friction angle of embankment fill,the height of load shedding block（LSB）and the ratio of elastic modulus of the embankment fill to elastic modulus of the compressible material layer（E_f/E_s）increase,the vertical earth pressure on the crown of the LSC decreases.The phenomenon is because the shear stress of the embankment fill on the slip surface over the LSC crown mostly reaches the limit value,such that the most of loads of the central fill mass overburden the LSH surface are transferred to the adjacent fill masses.