黏性土底床中桩基底部吸力试验研究  

Experimental study on suction force beneath the pile foundation in cohesive soil beds

作　　者：于徽[1] 王闻恺 YU Hui;WANG Wenkai(China Waterborne Transport Research Institute,Beijing 100088,China)

机构地区：[1]交通运输部水运科学研究院,北京100088

出　　处：《海洋工程》2020年第2期73-82,共10页The Ocean Engineering

摘　　要：海洋工程结构物桩基/基础在水下黏性土底床中上拔时,其底部会产生负压,由于负压产生的吸力可一定程度上影响桩基的抗拔力,而对于该力的变化特性目前尚不明确。因此,开展对海工结构物桩基在黏性土底床中上拔时底部吸力的研究具有十分重要的现实意义。通过物理试验,测量了模型桩在黏性土底床垂直上拔过程中底部腔体形态、压力以及拉力的变化情况,分析了上拔速度和埋深比对桩体底部压力的影响。研究结果表明:在黏性土底床中,桩基底部负压吸力对抗拔力有一定影响;桩基上拔时,底部会产生孔隙水腔体,在负压作用下,腔体不断被周围土体回填,使腔体大小保持相对稳定;相同埋深条件下,桩基底部负压随上拔速度增加而增大,但当上拔速度增大到一定值后,其影响不再明显;相同上拔速度情况下,桩基所受负压随埋深的增加而增大。最后提出了计算桩基垂向上拔时底部最大吸力的经验公式,并对公式进行验证。Generally,in underwater cohesive beds,suction force due to negative pressure will develop beneath the marine engineering structures’pile foundation during pullout.However,the dynamic characteristic of the suction force is still ambiguous.Therefore,it is of great practical significance to study the suction force beneath the pile foundation in the cohesive beds during pullout.In this study,the cavity shape,the pressure and the pullout force were evaluated during pullout.The effects of the pullout speed and the embedment depth of the pile foundation on the suction force were analyzed,respectively.The experimental results show that the suction force has a certain impact on the pullout capacity;pore water cavity will be formed at the bottom of pile foundation during pullout,the cavity is continuously backfilled by the surrounding soil owing to the negative pressure,so that the size of the cavity remains relatively stable;under the same embedment depth,the negative pressure initially increases with increasing pullout speed until the pullout speed exceeds a critical value and its influence is no longer obvious;under the same pullout speed,a deeper embedment depth leads to a higher negative pressure.Finally,an empirical formula for calculating the maximum suction force of pile foundation is proposed.The formula has good calculation accuracy.

关 键 词：海工结构物 桩基 黏性土底床 吸力 抗拔力 

分 类 号：P751[交通运输工程—港口、海岸及近海工程]