| Gravity anchorage,as an important bearing member of long-span suspension bridge,has been developed and applied maturely.In previous projects,gravity anchorage is usually buried deep,and hard bedrock is used as its supporting layer.However,there are few studies on gravity anchorage located on extremely heterogeneous foundation such as soil-rock composite foundation.In this paper,the settlement characteristics and overall stability of gravity anchorage foundation on soil-rock composite foundation are systematically studied based on the engineering background of the Jianshui-side anchorage foundation of Yunnan Honghe Bridge,the main contents and conclusions of this paper are as follows:(1)Based on load transfer method and shear deformation transfer method,the settlement behavior of single pile in soil-rock composite foundation is analyzed,and the calculation method of settlement of single pile is obtained;on this basis,considering the reinforcing and restraining effect in pile group,the settlement behavior of pile group in soil-rock composite foundation is analyzed,and based on the redefined interaction coefficient of two piles,the matrix expression for calculating the settlement of pile groups with variable pile length in soil-rock composite foundation is obtained.(2)Based on Winkler foundation model,the soil-rock composite foundation is regarded as independent vertical loaded springs,and the anchorage foundation is regarded as a rigid body,according to the principle of force balance,the settlement calculation method of anchorage foundation considering pile-soil-rock combined action is obtained.The method is used to calculate the actual engineering case of the Jianshui-side anchorage of Honghe Bridge,the calculation results show that the maximum settlement of the anchorage foundation is 16.7mm,which meets the requirements of the code for settlement.(3)The vertical bearing capacity of soil-rock composite foundation is studied by field foundation load test,the results show that the characteristic value of bearing capacity of soil-rock composite foundation meets the design requirements;the vertical compressive bearing capacity and vertical compressive stiffness of rigid piles are studied by static load test of single pile in site,the results show that the vertical compressive bearing capacity of rigid piles meets the design requirements,and the theoretical calculation values of the vertical compressive stiffness of rigid piles are in good agreement with the measured values of field tests.(4)PLAXIS 3D finite element software is used to simulate the whole process of construction and operation of Jianshui-side anchorage,the following conclusions are drawn:(1)Compared with before foundation treatment,the maximum settlement,non-uniform settlement,horizontal displacement and maximum stress of the foundation are significantly reduced after foundation treatment,which indicates that the rigid pile treatment of the foundation on the weaker side can greatly improve the overall stiffness of the foundation on that side,thereby reducing the settlement and horizontal displacement of the anchorage and improving stability.(2)The safety factor of the anchorage calculated by numerical simulation is 2.8,which is close to the anti-sliding stability factor of the anchorage calculated by the code method. |
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