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某跨海大桥穿越区域土质较差,软弱土层较厚,为了确定桥梁桩基的承载力和周围各土层的侧摩阻力,在现场进行了一根试桩的自平衡测试。试验桩基桩长55m,桩径为1.50m,荷载箱埋设于桩底以上5m位置,桩端持力层为黏土粉砂岩。为了获得桩身不同截面位置的轴力,在桩身不同位置埋设了钢筋计。根据现场钢筋计测试数据,如果采用常刚度来计算桩身轴力,则会出现荷载大于荷载箱加载值,这明显不符合实际。所以根据不同加载等级,轴力计算时采用合理的变刚度原则。桩身刚度随着加载等级变化而变化,是应变的函数。然后通过等效转换方法将自平衡测试结果等效转换为常规的桩顶荷载位移曲线。
A cross-sea bridge through the region of poor soil quality, thick soil layer thick, in order to determine the bearing capacity of the bridge pile foundation and the surrounding soil friction, the self-balance test of a test pile in the field. The pile length of the test pile is 55m, the pile diameter is 1.50m, the load box is buried 5m above the bottom of the pile, and the bearing layer at the pile end is clay siltstone. In order to obtain the axial force of different sections of the pile body, steel bars are buried in different positions of the pile body. According to the on-site steel bar test data, if the constant stiffness is used to calculate the axial force of the pile, the load will be greater than the load value of the load box, which is obviously not in conformity with the actual situation. Therefore, according to different loading levels, the calculation of axial force using a reasonable principle of variable stiffness. Pile stiffness changes with the load level changes, is a function of strain. Then the equivalent self-balance test results are converted into the conventional pile-top load-displacement curve by the equivalent conversion method.