薄壁筒桩在滩涂土地区荷载传递特性现场试验研究

IN-SITU EXPERIMENTAL STUDY OF LOAD TRANSFER PROPERTIES OF THIN-WALL TUBULAR PILE IN TIDAL SOIL AREA

目前,国内外缺乏通过现场试验对薄壁筒桩荷载传递特性方面的研究,关于筒桩加固滩涂土地基的研究也较少。以温州浅滩一期半岛起步区首期1#地块为工程背景,进行现场荷载试验,以现场实测数据分析筒桩荷载传递特性。研究结果表明:在最大荷载作用下,较长的筒桩表现为端承摩擦型桩,桩侧摩阻力比约为75%,较短的筒桩表现为纯摩擦型桩,通过增加桩长、桩径可以提高筒桩竖向承载力;该类地区适合建5层以内工业厂房;桩身轴力自上向下逐渐发挥,桩身上部与下部土层摩阻力异步发挥;当上部土层达到极限侧摩阻力时,随着荷载的增加,出现侧阻软化现象,内侧摩阻力沿桩身自下向上逐渐发挥,为外侧摩阻力的20%～25%。采用簿壁筒桩加固滩涂土地基时,应考虑土芯内侧摩阻力对承载力的贡献。

At present, few in-situ experiments have been conducted on thin-wall tubular piles about load transfer properties, and few studies have been reported about thin-wall tubular piles in tidal soil foundation treatment. Hence, based on the region #1 of the first-period peninsula in Wenzhou tidal land, in-situ static load tests were performed on thin-wall tubular piles. According to test data, load transfer properties were analyzed. The results indicate that about 75% of the load at pile head is shared by the outer frictional resistance, and the long piles work as end-bearing frictional piles under the maximum load while the short piles work as pure frictional piles. In order to increase bearing capacity, thin-wall tubular pile can be lengthened and widened appropriately. Industrial workshops within 5 floors can be built in this area. The axial force decreases with the increasing depth, and the outer frictional resistances of upper and lower soils work asynchronously. With the increase of load, side resistance softening happens when the frictional resistance of upper soil is up to the ultimate value. The inner frictional resistance is generated from the end of pile and it is about 20% - 25% of the outer frictional resistance. When the thin-wall tubular piles are applied to reinforcement of tidal soil foundation, the contribution of inner frictional resistance of soil to bearing capacity should be taken into account.