黏性土中开口与闭口模型管桩受力性状试验研究

为研究开口和闭口试桩在黏性土体静力沉桩过程中荷载传递规律及承载性能的差异性，采用桩身开槽预埋增敏微型光纤光栅传感器的方法，针对黏性地基土，开展两组不同桩端形式模型试桩承载性能对比试验，测得沉桩过程中压桩力、桩端阻力、桩侧摩阻力及桩身轴力发展变化规律。结果表明：光纤光栅传感器可实时监测沉桩过程中桩身受力状态；开口和闭口模型管桩的压桩力、桩端阻力等荷载均随着沉桩深度的增加呈增长趋势，而不同贯入深度下的桩身轴力却逐渐递减；黏性土中的静力压桩、开口管桩和闭口管桩的桩端阻力占比均超过50%；在桩侧摩阻力发挥上，双壁开口模型管桩外管是内管的3倍。当开口管桩贯入深度达到最大值90 cm时，土塞高度稳定在33 cm，此时，桩侧单位侧摩阻力的分布呈下大上小的形式。

Experimental study on bearing behavior of open and closed model pipe piles in cohesive soil

In order to study the load transfer pattern and the bearing capacity difference between the open test pile and the closed test pile in the static pile sinking process in the cohesive soil, the method of pre-embedded sensitized micro-fiber grating sensor is adopted in this paper. In the foundation soil, a comparison test of the bearing capacity of the test piles in different pile end models was carried out. The variation of pile force, pile end resistance, pile side friction resistance and pile axial force was measured. The testing results show that the fiber Bragg grating sensor can monitor the pile body stress state in the pile sinking process in real time; the pile bearing capacity and pile end resistance of the open and closed model pipe piles all increase with pile depth, with differentmagnitudes. The axial force of the pile under the depth is gradually decreasing; the ratio of the pile end resistance of the open pipe pile and the closed pipe pile is more than 50%; the double-walled open-ended model pipe pile is used for the pile side friction resistance, of which the outer tube is 3 times as much as the inner tube.. When the penetration depth of the open pipe pile reaches a maximum of 90 cm, the height of the soil plug is stable at 33 cm. Consequently, the distribution of the side frictional resistance of the pile side increase from the top to the bottom.