Capacity of Cutting Caisson Foundations in Clay-over-Sand under General Loadings
In addition to the vertical load generated by the upper structure of the bridge,the cutting caisson foundation of the bridge will also bear the lateral loads caused by train braking,lateral swing and centrifugal force.The existing specifications mainly focus on whether the vertical bearing capacity of the cutting caisson foundation meets the bearing capacity of the ground,without considering the composite bearing capacity of the cutting caisson foundation in the three-dimensional space.In view of the typical soil layer conditions applicable to the cutting caisson foundation,the one-way and composite bearing characteristics of the circular cutting caisson foundation in the upper clay and lower sand layer are studied by using the finite element method.The influence of the strength of the overlying clay layer and the length-diameter ratio of the cutting caisson foundation on the one-way bearing capacity and composite bearing capacity of the foundation is analyzed.The results show that due to the influence of the overlying clay,the bearing capacity of the excavated shaft foundation is reduced to different degrees compared with the sandy soil foundation,and this reduction effect increases with the increase of the thickness of the clay layer above the shaft end,with the most obvious reduction in the horizontal bearing capacity.Based on the numerical calculation results,the envelope surface expression of the bearing capacity of the circular caisson foundation in the upper clay and lower sand strata is established.The practical calculation formula of the characteristic parameters of the envelope surface varying with the length-diameter ratio of circular cutting caisson foundation and the vertical load level is proposed.
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