碎石桩单桩和多桩荷载传递方式的实验研究  

TESTING RESEARCH ON LOAD TRANSFER MODES OF SINGLE AND MULTIPLE GRAVEL PILES

作　　者：马崇武[1] 慕青松[2] 马君伟[2] 花拓[2] 

机构地区：[1]东莞理工学院建筑工程系,广东东莞523808 [2]兰州大学土木工程与力学学院,甘肃兰州730000

出　　处：《岩石力学与工程学报》2008年第S1期3116-3121,共6页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金青年基金项目(10402012);东莞市科研发展专项基金项目(2005D046)

摘　　要：在自行设计加工的二维实验设备上,应用杠杆–砝码加载系统和应力环直接测量桩底压力的方法,研究桩长对碎石桩单桩及多桩(三桩)荷载传递方式的影响。碎石桩材料为白色水磨石子(大理岩),平均粒径0.75cm;桩间土为人工调制的一定含水量的兰州黄土和沙坡头细砂按体积比3∶1混合而成。实验给出了碎石桩的临界桩长效应,即长度小于临界桩长的短桩和大于临界桩长的长桩的荷载传递方式不同,短桩主要靠桩底土体承受顶部荷载,而长桩主要靠桩顶拱结构和桩间土承受顶部荷载,这决定了短桩和长桩不同的破坏模式,即短桩的桩身刺入破坏和长桩的顶端拱结构鼓胀坍塌连带桩间土楔形剪出的破坏。与单桩相比,多桩的顶部压力对其底部压力存在交叉叠加影响,并且多桩及其桩间土之间的相互作用可以有效减小临界桩长,在桩较短时就能使桩顶端的拱结构生成并趋于稳定。研究结果说明,需对短桩和长桩分别建立不同的承载力计算公式。The effect of pile length on the load transfer modes of single and multiple gravel piles is studied using a self-developed two-dimensional experimental apparatus with lever-weight loading systems and directive measurement of pile-bottom pressure by stress ring. In the tests,mechanical-crushed marble stone with an average diameter of 0.75 cm is chosen as the material of gravel piles;and the mixture of manual-disposal Lanzhou loess with certain water contents and Shapotou sand in the volume proportion of 3∶1 is used to be the soil around pile. The test results show that there exists a critical length(more specifically,a critical ratio of pile length to pile diameter). In detail,a majority of top load is borne on the bottom within a short gravel pile under the critical length,but on the top arch within a long one over the critical length,the different load transfer modes result in the different failure modes. The failure of the short gravel pile is induced by the pile plunging into the bottom soil,but the failure of the long one is caused by the shear failure in a triangle region of the lateral soil which induces the swelled failure of the top arch. Additionally,in the case of multiple gravel piles,the top load on each gravel pile can influence the pressure distribution at the bottom of the other piles;the interaction between the piles can accelerate the formation of the top arches,and effectively decrease the critical length consequently. This study indicates that different theoretical formulas should be proposed to calculate the bearing capacity of short and long gravel piles.

关 键 词：桩基工程 碎石桩 颗粒介质 临界桩长 桩周土 拱结构 破坏模式 

分 类 号：TU473.1[建筑科学—结构工程]