常武地区竹节桩应用相关问题分析及对策

Analysis and Countermeasures of Problems Related to Applicationof Nodular Piles in Changzhou Wujin Areas

竹节桩侧壁设置有凸肋,理论上比同截面管桩有更大的桩土摩阻力。文章针对某办公楼项目中采用竹节桩时,工程桩检测时单桩承载力只有估算值80%左右的情况展开分析,并与邻近项目数据及规范要求作了对比。由于常武地区工程对竹节桩的应用经验不足,勘察报告中提供的预制桩参数偏高,因而未能实现理论上的异形截面的摩阻力增大效应,基础设计时的单桩承载力取值应以设计前进行的静载荷试验结果为准;竹节桩沉桩过程对桩周土体扰动程度较大,土体固结时间相对较长,需要比现行规范更长的休止期;相同桩顶荷载下竹节桩沉降大于相对应的管桩,对需要严格控制沉降的项目,需慎重采用;在常规工期下,对以粉土为主的项目,竖向抗压侧阻力截面影响系数β_(c)取0.8左右为宜。

The side wall of the nodular pile is provided with convex ribs,which theoretically has greaterpile-soil friction resistance than the pipe pile with the same section.Analysis is conducted regarding the situation in which the bearing capacity of the single pile is only about 80%of the estimated value when the nodular pile is used in an office building project,and then comparison with the data of adjacent projects and the requirements of specifications is conducted.Due to the lack of experience in the application of nodular piles in the local project,the parameters of precast piles provided in the survey report are on the high side,thus the theoretically increasing effect of friction resistance of special-shaped sections is not realized in practice,and the bearing capacity of the single pile in the foundation design should be subject to the static load test results before the design.The pile sinking process of the nodular pile has a great disturbance to the soil around the pile,thus the consolidation time of the soil is relatively long,which requires a longer period of rest than the current specifications.Under the same pile top load,the settlement of the nodular pile is greater than that of the corresponding pipe pile,thus,for the projects that need to strictly control the settlement,the nodular pile should be carefully adopted.During the conventional construction period,for the projects mainly involving silt,it s proper to take 0.8 or so as the influence coefficient β_(c) of the vertical compressive side resistance section.