大直径旋挖钻孔灌注桩载荷试验及承载性能仿真分析

发布时间：2018-01-06 23:05

本文关键词：大直径旋挖钻孔灌注桩载荷试验及承载性能仿真分析　出处：《长安大学》2015年硕士论文　论文类型：学位论文

【摘要】：桩基础现已发展成为公路桥梁建设中广泛采用的基础形式,其造价较高通常占桥梁下部结构的1/3以上,因此桩基础在保证安全耐用的同时也要经济合理。通过现场静载试验手段研究单桩极限承载特性进而为桩基设计参数优化提供参考是最常用且直观的方法,然而对于大直径灌注桩,载荷试验往往难以得到其极限承载特性,根据不完全试验数据对其承载特性进行研究有重要的工程意义。本文依托黄延高速扩能工程开展大直径桩轴向载荷试验,运用修正的灰色理论模型和有限元软件结合试验结果对该地区大直径旋挖桩极限承载特性展开预测和分析,主要研究工作如下:(1)参照试验地工区工程桩设计标准,在弱湿陷性黄土地基中进行竖向静载试验,采集室内外试验数据并初步分析,总结该地区大直径旋挖桩承载性状;(2)结合以往载荷试验数据,通过MATLAB实现GM(1,1)预测模型计算,与常用Q-s曲线预测方法对比各自预测精度并分析相对误差和预测原理,选用精度最高的修正GM(1,1)预测模型对本次试验结果进行预测。(3)根据试验实测数据,运用ABAQUS建立三维仿真计算模型并考虑载荷试验中锚桩上拔作用对试桩影响;对比仿真计算结果与现场试验数据,验证仿真计算模型较为合理。(4)研究静载试验中锚桩设置方式对试桩极限承载力判定的影响,根据不同的锚桩布置方案分别建立仿真模型研究对试验结果影响程度最小的锚桩布设方式。(5)对影响单桩极限承载力的桩周土体参数如:变形模量、粘聚力及桩周土体内摩擦角及桩体参数如:桩长、桩径、桩身弹模进行仿真分析,为提高桩基极限承载力的工程手段如:桩端、桩侧后压浆等工艺提出适用范围;对比数值分析结果,对“合理桩长”和“尺寸效应”进行了验证。
[Abstract]:Pile foundation has developed into a widely used foundation form in highway and bridge construction. Its high cost usually accounts for more than 1/3 of the bridge substructure. Therefore, the pile foundation should be economical and reasonable while ensuring safety and durability. It is the most common and intuitive method to study the ultimate bearing characteristics of single pile by static load test in situ and to provide reference for the optimization of design parameters of pile foundation. However, for large diameter cast-in-place piles, it is difficult to obtain their ultimate bearing characteristics by load test. Based on the incomplete test data, it is of great engineering significance to study its bearing characteristics. The axial load test of large diameter pile is carried out based on the Huangyan high-speed capacity expansion project. Using the modified grey theory model and the finite element software combined with the test results, the ultimate bearing characteristics of the large diameter rotary excavated pile in this area are predicted and analyzed. The main research work is as follows: (1) the vertical static load test is carried out in the weak collapsible loess foundation with reference to the design standard of engineering piles in the test site, and the indoor and outdoor test data are collected and analyzed preliminarily. The bearing capacity of large diameter rotary excavated piles in this area is summarized. (2) based on the previous load test data, the calculation of GM-1 / 1) prediction model is realized by MATLAB. Compared with the Q-s curve prediction methods, the relative error and the prediction principle are analyzed. The modified GM(1 with the highest precision is selected. 1) forecasting model is used to predict the test results. (3) according to the measured data of the test, the three-dimensional simulation model is established by using ABAQUS and the influence of uplift action of anchor pile on the test pile is considered in the load test. Comparing the simulation results with the field test data, verify that the simulation calculation model is more reasonable. 4) study the influence of anchoring pile setting mode on the ultimate bearing capacity of test pile in static load test. According to different layout schemes of anchor pile, simulation models were established to study the influence of anchor pile layout mode on the ultimate bearing capacity of single pile, such as deformation modulus. The cohesive force, the internal friction angle of soil around the pile and the parameters of pile body such as pile length, pile diameter and elastic modulus of pile body are simulated and analyzed, so as to improve the ultimate bearing capacity of pile foundation by engineering means such as: pile end. The application range of the technology such as post-grouting on the side of pile is put forward. Compared with the results of numerical analysis, the reasonable pile length and size effect are verified.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U443.15

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