钻孔灌注嵌岩桩的长径比和嵌岩比对其承载力的影响研究

发布时间：2018-04-14 09:14

本文选题：嵌岩桩 + 极限承载力　；参考：《兰州交通大学》2017年硕士论文

【摘要】：嵌岩桩基已被广泛应用在高层建筑、桥梁等大型工程中。但由于桩周土体、岩体特性的多样性和桩土、桩岩相互作用的复杂性以及试桩试验耗时耗力、所需费用高、所得数据存在较大的离散性等问题存在,导致桩基现场原位试验很难达到精准的结果。故国内现行规范关于嵌岩桩极限承载力的研究主要利用半理论半经验的公式来计算。依据这一现状,对嵌岩桩的极限承载力进行更深入、更彻底的研究已显得十分必要。本文通过收集、整理180根试桩资料,从中选出典型的38根试桩(30根软岩嵌岩桩和8根硬岩嵌岩桩)作为本文考虑长径比和嵌岩比等因素来推导嵌岩桩极限承载力修正计算公式的依据。通过38根试桩的现场原位测试数据分析计算与有限元数值模拟进行对比研究,推导出考虑长径比和嵌岩比对嵌岩桩极限承载力影响的修正计算公式,本文完成的主要内容如下:(1)通过认真学习国内外嵌岩桩的试验研究和文献资料,归纳总结嵌岩桩的承载机理和荷载传递特性。对嵌岩桩竖向承载力特性及嵌岩桩桩土侧阻力、桩岩侧阻力以及桩端阻力的发挥特性进行分析,讨论了影响嵌岩桩竖向极限承载力的主要因素:嵌岩桩上部桩周土层性质、下部桩周岩石层性质、桩与桩周土的相对位移、桩与嵌岩段岩层的相对位移、桩与桩端岩石相对位移、桩的长径比、嵌岩比和桩底清孔情况等。(2)对比目前国内使用较为广泛的三种地基基础规范,通过认真分析、对比嵌岩桩极限承载力的计算公式,评价了各规范计算方法的差异性及存在的不足之处。(3)通过对本文收集的试桩进行分析汇总,将试桩的嵌岩比、长径比、土层侧阻力分担荷载比、岩层侧阻力分担荷载比、桩端阻力分担荷载比等经过理论分析和数据处理。然后应用数理统计学的曲线拟合法得到软岩嵌岩桩和硬岩嵌岩桩的土层侧阻系数、岩层侧阻系数、端阻系数,并结合现行公路桥规对嵌岩桩极限承载力的计算公式,推导出了修正后的嵌岩桩极限承载力的计算公式。(4)针对本文的修正计算公式,将某实际工程案例资料分别代入到现行公路桥规和经验公式以及本文修正得到的有关嵌岩桩极限承载力的计算公式中,分别得到相应的结果,并相互对比分析,验证本文关于嵌岩桩极限承载力修正计算公式的合理性和可行性。
[Abstract]:Rock-socketed pile foundation has been widely used in high-rise buildings, bridges and other large-scale projects.However, due to the diversity of soil and rock mass characteristics, the complexity of pile-rock interaction, the time-consuming and labor-consuming test of pile test, the high cost and the large dispersion of the obtained data, etc.It is very difficult to achieve accurate results for in-situ test of pile foundation.Therefore, the research on ultimate bearing capacity of rock-socketed piles in current domestic codes is mainly based on the semi-theoretical and semi-empirical formula to calculate the ultimate bearing capacity of rock-socketed piles.According to this situation, it is necessary to study the ultimate bearing capacity of rock-socketed pile.In this paper, 180 test piles are collected and sorted.The typical 38 test piles and 30 soft rock socketed piles and 8 hard rock socketed piles are selected as the basis for deducing the revised formula of ultimate bearing capacity of rock-socketed piles considering the factors such as aspect ratio and rock-socketed ratio.Based on the analysis and calculation of in-situ test data of 38 test piles and the finite element numerical simulation, a modified calculation formula considering the influence of aspect ratio and rock-socketed ratio on ultimate bearing capacity of rock-socketed pile is derived.The main contents of this paper are as follows: (1) by studying the experimental research and literature data of rock-socketed piles at home and abroad, the load-bearing mechanism and load-transfer characteristics of rock-socketed piles are summarized and summarized.The characteristics of vertical bearing capacity of rock-socketed pile and its soil side resistance, pile rock side resistance and pile tip resistance are analyzed. The main factors affecting the vertical ultimate bearing capacity of rock-socketed pile are discussed: the properties of the surrounding soil layer in the upper part of rock-socketed pile.The properties of the rock stratum around the lower pile, the relative displacement of the pile to the surrounding soil, the relative displacement of the rock layer between the pile and the rock-socketed section, the relative displacement of the pile to the rock at the end of the pile, the ratio of length to diameter of the pile,Compared with the three kinds of foundation codes which are widely used in our country at present, through careful analysis, the calculation formula of ultimate bearing capacity of rock-socketed pile is contrasted.This paper evaluates the difference of the calculation methods of various codes and their shortcomings. (3) through the analysis and summary of the test piles collected in this paper, the rock socketed ratio, the aspect diameter ratio, the lateral resistance of the soil layer, the load ratio of the lateral resistance of the rock layer, and the load ratio of the lateral resistance of the rock layer are analyzed and summarized.The load ratio of resistance sharing at the end of the pile is analyzed by theory and data processing.Then the soil lateral resistance coefficient, rock layer lateral resistance coefficient and end resistance coefficient of soft rock socketed pile and hard rock socketed pile are obtained by using the curve fitting method of mathematical statistics, and the calculation formula of ultimate bearing capacity of rock-socketed pile combined with the existing highway and bridge rules is obtained.A modified formula for calculating ultimate bearing capacity of rock-socketed pile is derived.The actual engineering case data are put into the existing highway and bridge rules and empirical formulas respectively, and the calculation formula of ultimate bearing capacity of rock-socketed pile is revised in this paper. The corresponding results are obtained and compared with each other.The rationality and feasibility of the modified formula of ultimate bearing capacity of rock-socketed pile are verified.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U443.15

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