局部冲坑对导管架刚度影响的模型试验

Experimental study on the impact of local scour hole on the stiffness of jacket foundation

采用缩尺4桩导管架风机模型试验研究冲坑对导管架刚度的影响。通过控制导管架基桩冲坑出现顺序及不同冲坑深度模拟冲刷过程,研究静力荷载作用下局部冲坑对导管架基础刚度、内力分配规律的影响以及冲坑分布、冲坑深度、冲坑出现顺序、冲坑坡度对导管架共振频率的影响。结果表明:荷载较小时,1.5 D(D为桩径)深度以内的局部冲坑对导管架静刚度的影响较小,但冲坑对静刚度的影响随荷载增加而逐渐增大;当冲坑深度大于1 D时,导管架共振频率开始出现下降趋势,此时任意基桩再出现更深冲坑都会引起共振频率的较大下降;当局部冲坑深度分别为1.5 D和2D时,风机共振频率分别下降约3.2%和6.3%;当冲坑形状为圆锥形时,保持局部冲坑深度不变,改变冲坑坡度对导管架风机共振频率影响较小。

A scaled 4-pile jacket wind turbine model was used to study the impact of scour holes on the jacket stiffness.The scouring process was simulated by controlling the occurrence sequence of scour holes and different scour depths of jacket foundation and this paper investigated the influence of local scour holes on the distribution of internal forces and stiffness of jacket foundation under static load.The results show that:when the load is small,the influence of local hole within 1.5 D(D is the pile diameter)on the static stiffness of jacket is small;But the impact of scour hole on the static stiffness increases gradually with the increase of load,because with the increase of load,the axial force of the back-row pile gradually shifts from compression to tension,which leads to the stiffness decreaseof the pile.For the resonance frequency of jacket,the study shows that when the depth of the scour hole is greater than 1 D,jacket resonance frequency started to decrease;At this time,any pile with a deeper hole will cause the resonance frequency to drop;When the local scour depth is 1.5 D,the first-order resonance frequency of the wind turbine decreases about 3.2%,while the resonance frequency of the wind turbine decreases by about 6.3%when the scour depth is 2 D.When the shape of scour hole is conical and the depth of local scour is kept unchanged,the change of the scour hole slope will cause a small change in the resonance frequency of jacket wind turbine.