黄土塬地区大直径长桩承载性状与优化设计研究

发布时间：2019-03-08 11:25

【摘要】：黄土塬地区桩基问题研究匮乏,依托陇东首栋超高层建筑,在试验桩身上布置混凝土应变计、钢筋应力计,承台底板下和桩端布置土压力盒,对原地基土、单桩基础和单桩承台基础分别进行现场原位载荷试验;利用ANSYS有限元软件对全短桩基、全长桩基及长短桩组合桩基在竖向荷载作用下的筏板沉降变形、地基土应力场与沉降变化进行分析。结果发现:(1)黄土塬场地地基土夹层交互分布、湿陷性不连续,存在由非湿陷性黄土变成湿陷性黄土的可能,桩周土层对桩基内力传递与分布影响显著,桩身出现多个中性点,湿陷性土层下限深度确定更加复杂;(2)各级荷载作用下,桩基Q-S曲线呈缓变型发展,表现为典型的摩擦型桩,桩身内力发挥具有异步性;试验加载至8 000 k N时,桩顶最大沉降为8.15 mm,单桩和单桩承台端阻力分别仅占桩顶荷载的4.8%和2.1%;(3)单桩承台基础中承台底部实测反力呈倒"盆"形分布、边缘应力较大,桩土承台体系的承载性能优于单桩基础;桩基础设计时,可结合经验以承载力和最大允许变形量进行控制,提高桩身线刚度抵抗自身压缩变形,减小桩基上部沉降;(4)长短桩组合桩基础充分利用与发挥了长桩控制沉降的作用与地基土浅层承载的能力,减少了长桩数量,节省了桩基造价,值得进一步深入研究。
[Abstract]:There is a lack of research on pile foundation in Huangtuyuan area. Relying on the first super-high-rise building in East Gansu Province, the concrete strain gauge, reinforced stress gauge, earth pressure box under the bottom plate of the cap and the pile end are arranged on the test pile, and the soil pressure box is arranged under the bottom plate and the pile end of the pile. The in-situ loading tests of single pile foundation and single pile cap foundation are carried out respectively. ANSYS finite element software is used to analyze the settlement deformation of raft, stress field and settlement of soil under vertical load on full-short pile foundation, full-length pile foundation and long-short pile combination pile foundation. The results are as follows: (1) the interaction distribution of soil and interlayer on the loess plateau site, the collapsibility discontinuity, the possibility of changing from non-collapsible loess to collapsible loess, and the influence of soil layer around piles on the internal force transfer and distribution of pile foundation is obvious. There are many neutral points in the pile body, and it is more complicated to determine the lower limit depth of collapsible soil layer. (2) under the action of all kinds of loads, the QS curve of pile foundation develops slowly, which is a typical friction pile, and the internal force of pile body plays an asynchronous role; When the pile top is loaded to 8 000 k N, the maximum settlement of the pile top is 8.15 mm, and the resistance at the end of the pile cap only accounts for 4.8% and 2.1% of the pile top load, respectively. (3) in the single pile cap foundation, the measured reaction force at the bottom of the cap is inverted "basin", and the edge stress is large, and the bearing capacity of the pile-soil cap system is better than that of the single pile foundation. In the design of pile foundation, the bearing capacity and maximum allowable deformation can be controlled according to the experience, so as to improve the linear stiffness of pile body to resist self-compression deformation and reduce the settlement of the upper part of pile foundation. (4) the long-and long-pile composite pile foundation makes full use of the effect of long pile to control settlement and the bearing capacity of shallow soil, reduces the number of long pile and saves the cost of pile foundation, which is worthy of further study.
【作者单位】：兰州理工大学甘肃省土木防灾减灾重点实验室;兰州理工大学西部土木工程防灾减灾教育部工程研究中心;
【基金】：教育部创新团队支持计划项目(2013IRT13068) 甘肃省科技重大专项计划项目(1302FKDA030)~~
【分类号】：TU473.1

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