重复插拔桩引发粉质海床扰动效应研究

自升式钻井平台的插桩和拔桩过程会严重扰动天然海床，形成安全隐患。借助室内物理模型试验模拟了粉质海床中自升式平台的插拔桩过程，并将物理模型试验结果与现场CPT重复贯入测试结果进行了对比分析，从定性和定量角度探讨了单次和重复插拔桩引起的粉质海床扰动效应。研究表明:相比初次插拔桩，二次插拔桩形成桩坑的几何尺寸有所增大；二次插桩较初次插桩引起的超孔压有所下降，最大降幅可达35%；重复插拔桩引发的海床扰动度随距桩靴中心水平距离的增大基本呈线性减小趋势，中间层位土体的扰动度相对浅表层和深层土体更大；相较初次插桩，二次插桩桩端阻力有所减小，但桩端最终峰值阻力却稍有增大，二者的起拔力则比较接近；室内重复插拔桩物理模型试验桩端阻力发展趋势与现场CPT重复贯入探头阻力监测结果吻合较好。

Study on the disturbance effect of silty seabed caused by repeated spudcan penetration and extraction

The spudcan penetration and extraction processes of the jack-up drilling rig will seriously disturb the natural seabed. In the present study, the penetration and extraction processes of the jack-up platform in silty seabed were modeled with the help of an indoor physical model experiment, and comparison was made between the model findings and the field CPT repeated penetration results. Based on this, the disturbance effect of silty seabed caused by a single and repeated penetration and extraction of pile was discussed from a qualitative and quantitative perspective, respectively. The results show that compared with the initial spudcan penetration and extraction process, the geometric size of the pile pit caused by the second process was expanded to some extent; the excess pore water pressure caused by the second penetration of pile was lower than that created during the first pile penetration, and the maximum drop could reach 35%; the disturbance degree of seabed caused by the repeated penetration and extraction of pile generally decreased linearly with the increase of the horizontal distance from the center of the pile, and the soil at the middle layer was disturbed more seriously than shallow and deep soils; in comparison with the initial penetration, the tip resistance of pile during the second penetration reduced to some extent, while the corresponding final peak tip resistance was increased, together with the relatively close pulling forces between them; and the development trend of the pile tip resistance monitored from the indoor physical model experiment showed good consistency with the field CPT repeated penetration test results.