【作者】 聂珊利；

【导师】 张远芳； 李传镔；

【作者基本信息】 新疆农业大学 ， 水利水电工程， 2010， 硕士

【摘要】 如何正确计算和确定单桩竖向承载力,尤其是单桩竖向极限承载力,是桩基工程设计中的一项重要内容,目前确定单桩竖向极限承载力的方法很多,但在工程应用中都或多或少地存在着一定的问题。对摩擦桩来说,其竖向承载力主要由桩侧摩阻力来承担,由于在摩擦桩受力过程中,其Q ? s曲线呈缓变型,随着位移的增大,其侧摩阻力渐渐趋于定值最后达到极限, Q ? s曲线没有明显的拐点。在达到极限的过程中,侧摩阻力逐渐增大,达到最大时桩周土处于极限平衡状态,也即桩周土体达到破坏,在此过程中桩和桩周土之间的力学性状发生了“突然变化”。因此,本文尝试将尖点突变理论引入到摩擦桩竖向极限承载力的计算中,推导出摩擦桩单桩竖向极限承载力的计算公式,将其运用于实际工程中,并与静荷载实验结果对比,初步得到以下几点结论。极限荷载对应的极限位移s 0可以运用双曲线法的拟合结果推求出来,将其运用于突变理论的计算公式中,可以得到基于尖点突变理论的摩擦单桩竖向承载力值。临界失稳点位移值s*可由极限位移值s 0求出, s 0越大,s*也越大。当桩周土存在多层较为密实的粗粒土时,运用尖点突变理论计算公式对单桩竖向承载力进行分析时,得到的结果与静载荷试验有较大的偏离,这时需要根据工程实践对公式进行修正。从工程实践出发,给出了对尖点突变理论计算公式的修正系数ξ,此时桩的承载力当摩擦桩置于软土地基中时,运用尖点突变理论的计算公式对其承载力进行分析可以得到较好的结果。更多还原

【Abstract】 As the important content of the devise, how to calculate and confirm the vertical bearing capacity of single pile, especially the utmost vertical bearing capacity of single pile is very important. There are a number of methods to confirm the vertical bearing capacity of single pile, but issues appeared when used in engineering adhibitions more or less. The ultimate bearing capacity of friction pile be undertaken by the friction force around pile and the Q ? scurve assume to be a slowly model. The friction force around pile tend towards to be a fixed value with the aumentation of the displacement and attain to the utmost finally. There is no distinct inflexion in Q ? s curve. The soil around piles ttain the utmost equation predicament when the friction force attain to the largest. The mechanics character of piles and the soil around piles transformed abruptly. Based on the cusp catastrophe theory, the calculating formula of the vertical ultimate bearing capacity of friction pile is deduced in this paper. Then use the formula in engineering examples and compared with the practical results, we can get some conclusions.The utmost placement s 0 can be ascertained by the result of hyperbola, and we can get the vertical bearing capacity of friction piles based on the cusp catastrophe theory.The placement of critical point s * can be found by the utmost placement s 0,when s 0 get larger and larger, s * changes with s 0 and get larger and larger either.The results of cusp catastrophe formula departure biggish by the load test when multilayer close-grained thick soil around the piles. We must amend the formula bases the engineering adhibitions. Amend modulus are found according to the engineering adhibitions,and then the formula of vertical bearing capacity of single pile is: (1)22We can get good results when use the formula in flexible land which show that the formula could be used in such engineering adhibitions.更多还原