A Simplified Method for Calculating Vertical Earth Pressure on Rigid Load Shedding Culvert Crown Underneath the Embankment

For calculating the vertical earth pressure on the crown of a load shedding culvert (LSC) underneath the embankment fill, an analytical method is proposed in this paper. 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 method proposed in this paper considers the fact that the linearly elastic-perfectly plastic model is closer to the shear stress-strain model of embankment fill on the slip surface. According to the stress state of the embankment fill on the slip surface, the lateral earth pressure coefficient expression is derived from the geometric relationship of the Mohr's circle, in which the internal friction angle is considered as the independent variable. The stress states of the differential elements of embankment fill over LSC crown are analysed through equilibrium considerations. Thus, the analytical method for calculating the vertical earth pressure on the crown of LSC is obtained. The calculation examples are presented and compared with 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 overburdening the LSH surface are transferred to the adjacent fill masses.