摘要
某主跨为97.6 m的下承式系杆拱桥桥墩设置在黄河大堤外侧的淤背区,由于其内堆载土的逐年抬升使得桩基础受到负摩阻力作用。为准确把握负摩阻力的受力机理以及对桩身承载能力的影响,分别采用公路和铁路桩基础设计规范中的计算方法,并结合有限元方法,计算了有无套筒条件和不同堆载土高度条件下桩基的受力特性,研究了负摩阻力的受力机理和分布特性,获得了桩身在负摩阻力影响下的轴力。计算结果表明:填土前,桩身最大轴力在桩顶以下15 m深度处;施加填土荷载后,桩身轴力增加60.2%,最大轴力位置在桩顶以下50 m深度处。钢套筒虽然能减小其范围内桩基最大负摩阻力的75%~78%,但由于桩基中性点下移和钢套筒范围外负摩阻力的增大,桩基的最大轴力值仅减小5%,整个桩基的沉降量相差最大为2%。由以上结果可知,钢套筒无法有效提升负摩阻力影响下的桩基承载力,因此提高桩身材料强度是提升其承载力的可行方案。
The piers of a underpass rod-tied arch bridge with a main span of 97.6m are located in the silting area outside the Yellow River levee.The pile foundation is subjected to negative friction resistance due to the annual uplift of the piled soil in the bridge.In order to accurately grasp the stress mechanism of negative skin friction resistance as well as its influence on the bearing capacity of the pile body,the calculation method of pile foundation design in highway specification and railway specification are used respectively to calculate the presence of the sleeve conditions and different stack height of soil under the condition of the stress characteristics of pile foundation in combination with the finite element method,study the stress mechanism and distribution characteristics of negative skin friction resistance,and obtain the axial force of pile under the influence of negative friction resistance.The calculation results show that the maximum axial force of the pile is found 15 m below the pile top before filling.After applying soil filling load,the axial force of the pile increases by 60.2%,and the maximum axial force is located 50 meters below the pile top.Although the steel sleeve can reduce 75%~78% of the maximum negative friction resistance of pile foundation within its range,the maximum axial force of pile foundation only decreases by 5% due to the downward shift of the neutral point of pile foundation and the increase of negative friction resistance outside the steel sleeve range,and the maximum settlement difference of the whole pile foundation is 2%.According to the results,the steel sleeve cannot effectively improve the bearing capacity of pile foundation under the influence of negative friction resistance,and improving the pile material strength proves to be a feasible solution to raise its bearing capacity.
作者
魏宇
WEI Yu(China Railway Engineering Consulting and Design Group Co.,Ltd.,Beijing 100055,China)
出处
《铁道标准设计》
北大核心
2023年第4期67-72,共6页
Railway Standard Design
基金
中国铁路总公司科技研究开发计划项目(2017G006-H)
中国中铁股份有限公司科技开发计划项目(2017-重大-3)。
关键词
铁路桥墩
桩基础
桩周负摩阻力
桩基中性点
有限元法
填土荷载
钢套筒
railway pier
pile foundation
negative friction around pile
zero-point of pile
finite element method
fill load
steel sleeve
