根键桩抗拔位移场分布特征及荷载传递模型探究  

Research on visual model test of displacement distribute characteristics and load transfer model of root pile during uplifting

作　　者：张吉禄 黄雪峰[1,2] 韦林辉 周俊鹏 袁俊 王学明 ZHANG Jilu;HUANG Xuefeng;WEI Linhui;ZHOU Junpeng;YUAN Jun;WANG Xueming(School of Civil Engineering,Lanzhou University of Technology,Lanzhou 730050,China;School of Civil Engineering,Chongqing Jiaotong University,Chongqing 400074,China;Department of Military Installations Engineering,Army Logistical University of PLA,Chongqing 401311,China;Northwest Electric Power Design Institute Co.,Ltd.,China Power Engineering Consulting Group,Xi’an 710075,China)

机构地区：[1]兰州理工大学土木工程学院,甘肃兰州730050 [2]重庆交通大学土木工程学院,重庆400074 [3]陆军勤务学院军事设施工程系,重庆401311 [4]中国电力工程顾问集团西北电力设计院有限公司,陕西西安710075

出　　处：《煤炭学报》2020年第10期3435-3445,共11页Journal of China Coal Society

基　　金：重庆市研究生创新基金资助项目(CYB18126)。

摘　　要：为探究根键桩抗拔承载特性,基于PIV技术(粒子图像测速技术)与透明土组成的桩土变形可视化试验系统,对上拔荷载作用下同尺寸根键桩、扩底桩以及等截面桩进行非介入式模型试验。测得各桩荷载-位移曲线并对桩周土体位移场变化情况进行实时采集,通过对不同时刻各桩桩周土体位移场等值线图不同色阶部分像素点进行统计,实现对位移场发展规律以及土体塑性变形区域的精确对比,并进一步结合现有透明土三轴试验成果提出适用于小尺寸透明土模型试验桩土侧阻力计算模型,结果表明:试验条件下,虽然同尺寸扩底桩承载力更高,但是在中低荷载时,多层根键桩表现出对基础位移更好的控制能力,更适用于对位移有严格要求的建筑基础;根键的设置存在优化问题,为保证土体以及根键承载力的充分发挥,初步建议根键纵向间距以(4~6)L为宜(L为根键外伸长度);当根键层数较少时,根键对荷载扩散作用不明显,土体位移场范围相比等截面桩甚至出现小幅降低,而随着根键层数的增多,桩周土体位移场范围也随之显著扩大,在试验条件下,4层根键所带动的土体位移场面积约为扩底桩的113%,而塑性区面积仅为扩底桩的58%,根键桩承载能力提升潜力要优于扩底桩;极限荷载下,各桩桩周土体位移场均为“倒三角形”分布,且与水平面夹角均为(45°+φ/2);基于现有透明土研究成果所得桩土侧阻力计算模型能够在一定程度上反映基础荷载传递规律,由计算分析得,根键与扩大头的设置分别使土体极限承载力提高了1.27与1.18倍,变截面的设置使土体承载力得到了更大程度发挥,且深度效应对根键法向阻力影响远小于侧摩阻力。In order to explore the uplift bearing characteristics of the roots pile,the non-intrusive test was used to measure the roots pile,the belled pile and the equal section pile which had same size with the deformation visualization system consisting of PIV(particle image velocimetry)technology and transparent soil.The test measured the Q-S curves of each pile and collected the images of change in the displacement field around the pile in real time.Based on the above images,the area of pixels with different color scales in the contour map of displacement field was calculated and compared to make the precise comparison of displacement field and plastic region of soil come true.At last,the test inferred the calculation model of soil side resistance of small-scale transparent soil model test pile with the support of the existing triaxial test results of transparent soil.The result shows that under the test condition,although the bearing capacity of the belled pile with the same size to the roots pile is higher,the roots pile with multi-layer shows a better control ability to the foundation displacement under the middle and low load,and it is more suitable for the building foundation with strict requirements on the displacement.There are optimization problems in the setting of root key.In order to ensure the full play of the bearing capacity of soil and root key,the space between two layers of roots should install at 4~6L(L is the length of roots).When the number of layers of roots is small,the effect of roots on load diffusion is not obvious,and the range of soil displacement field is even slightly lower than that of equal section pile.With the increase of the number of layers of roots,the range of soil displacement field around pile is also significantly expanded.Under the test conditions,the area of soil displacement field driven by the roots pile with 4 layers of roots is about 113%of that belled pile,while the area of plastic area is only 58%of belled pile.The improvement potential of the bearing capacity of the roo

关 键 词：根键桩 位移场 抗拔极限承载力 PIV技术 透明土 

分 类 号：TU473.1[建筑科学—结构工程]