筒桩桩—网复合地基沉降计算研究
发布时间：2018-08-04 19:02
【摘要】：筒桩桩承式加筋复合地基是一种新型的地基处理工程技术,具有施工便捷、用料省、承载力高、施工周期短等优点。在深厚软土地区的工程建设中,由于沉降过大,特别是不均匀沉降引起的工程事故时有发生。而目前对于桩承式复合地基在荷载作用下的沉降计算仍多采用常规算法,无法区分桩顶与桩间土体的沉降差异。对地基内部在荷载作用下应力场和位移场的分布情况研究较少,实测资料更少,复合地基沉降计算理论仍远远落后于工程实践的需要,还有待于继续的发展。 针对筒桩桩网复合地基,本文首先依据Mindlin解推导了筒桩桩端均布阻力,桩外侧线性分布侧阻力和桩内侧指数型分布内摩阻力产生的附加应力的计算公式,从而可以达到对弹性地基内部任意点的附加应力计算求解；详细讨论了桩身阻力分布形式变化、桩身荷载分配变化和中性点位置变化对桩周地基内附加应力场的影响；比较了不同桩型截面情况下桩身阻力产生的附加应力系数的变化。 本文着重分析了桩承式加筋复合地基中“土拱效应”和“拉膜效应”的发挥情况,推导了其在三角形布桩情况下的相关理论公式进而得到桩土荷载分担比的计算方法；讨论了路堤填料的郎肯被动土压力系数和桩帽宽度与桩间距之比等参数的变化对路堤桩体荷载分担比的影响。 结合以Boussinesq解求得桩土地基内部由桩间土荷载所产生的附加应力情况,提出了筒桩复合地基沉降计算的M-B联合算法；将本方法得到的结果与广东某一高速公路工程的现场试验情况相对比,并结合有限元分析情况,证明了本文提出方法的可行性和正确性,对实际工程有一定借鉴作用。 最后,本文通过Abaqus软件对新型的四角形筒桩竖向受荷进行有限元模拟,分析了带肋异形薄壁筒桩特有的荷载传递规律,主要表现为外伸肋侧垂直于径向的面摩阻力发挥要快于肋侧旁面和圆周处。同时详细讨论外伸肋部长度和宽度变化对承载能力的影响,结果表明,肋长对竖向承载力影响显著,肋宽对其影响较小。对已有的筒桩承载力计算公式上进行了修正,提出了带肋异形筒桩的极限承载力计算公式,为今后在工程中的应用提供参考。
[Abstract]:Cylindrical pile bearing reinforced composite foundation is a new type of foundation treatment engineering technology, which has the advantages of convenient construction, low material consumption, high bearing capacity, short construction period and so on. In the engineering construction of deep soft soil area, engineering accidents caused by excessive settlement, especially uneven settlement, occur from time to time. At present, the settlement calculation of pile-supported composite foundation under load is mostly based on conventional algorithm, which can not distinguish the settlement difference between pile top and pile soil. The distribution of stress field and displacement field in the foundation under load is less studied and the measured data are less. The settlement calculation theory of composite foundation is still far behind the need of engineering practice and needs to be further developed. According to the Mindlin solution, the formulas for calculating the additional stresses caused by the uniform resistance at the end of the pile, the lateral resistance on the outer side of the pile and the internal friction of the inner exponential distribution of the pile are derived in this paper. So the additional stress of any point in the elastic foundation can be calculated and solved, and the influence of the variation of resistance distribution, load distribution and the position of neutral point on the additional stress field around the pile foundation is discussed in detail. The variation of the additional stress coefficient caused by the resistance of the pile with different cross-sections is compared. In this paper, the "soil arch effect" and "pull film effect" in pile-bearing reinforced composite foundation are analyzed emphatically, and the relevant theoretical formulas in the case of triangular pile placement are deduced, and the calculation method of load-sharing ratio of pile and soil is obtained. The influence of the parameters such as the Rankine passive earth pressure coefficient and the ratio of pile cap width to pile spacing on the load-sharing ratio of embankment pile is discussed. Combined with the Boussinesq solution to obtain the additional stress caused by the soil load between piles, the M-B joint algorithm for settlement calculation of the composite foundation is put forward. The results obtained by this method are compared with the field test results of a highway project in Guangdong Province, and combined with the finite element analysis, the feasibility and correctness of the proposed method are proved, which can be used for reference in practical engineering. Finally, this paper simulates the vertical load of a new type of tetragonal cylindrical pile by using Abaqus software, and analyzes the characteristic law of load transfer of thin-walled cylindrical pile with ribs. The surface friction at the lateral side of the rib is faster than that on the side of the rib and the circumference. At the same time, the influence of the length and width of the rib on the bearing capacity is discussed in detail. The results show that the rib length has a significant effect on the vertical bearing capacity, and the rib width has little effect on the bearing capacity. The existing formulas for calculating the bearing capacity of cylindrical piles are modified, and the formulas for calculating the ultimate bearing capacity of cylindrical piles with ribs are put forward, which provides a reference for the application in engineering in the future.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU470
本文编号：2164826
[Abstract]:Cylindrical pile bearing reinforced composite foundation is a new type of foundation treatment engineering technology, which has the advantages of convenient construction, low material consumption, high bearing capacity, short construction period and so on. In the engineering construction of deep soft soil area, engineering accidents caused by excessive settlement, especially uneven settlement, occur from time to time. At present, the settlement calculation of pile-supported composite foundation under load is mostly based on conventional algorithm, which can not distinguish the settlement difference between pile top and pile soil. The distribution of stress field and displacement field in the foundation under load is less studied and the measured data are less. The settlement calculation theory of composite foundation is still far behind the need of engineering practice and needs to be further developed. According to the Mindlin solution, the formulas for calculating the additional stresses caused by the uniform resistance at the end of the pile, the lateral resistance on the outer side of the pile and the internal friction of the inner exponential distribution of the pile are derived in this paper. So the additional stress of any point in the elastic foundation can be calculated and solved, and the influence of the variation of resistance distribution, load distribution and the position of neutral point on the additional stress field around the pile foundation is discussed in detail. The variation of the additional stress coefficient caused by the resistance of the pile with different cross-sections is compared. In this paper, the "soil arch effect" and "pull film effect" in pile-bearing reinforced composite foundation are analyzed emphatically, and the relevant theoretical formulas in the case of triangular pile placement are deduced, and the calculation method of load-sharing ratio of pile and soil is obtained. The influence of the parameters such as the Rankine passive earth pressure coefficient and the ratio of pile cap width to pile spacing on the load-sharing ratio of embankment pile is discussed. Combined with the Boussinesq solution to obtain the additional stress caused by the soil load between piles, the M-B joint algorithm for settlement calculation of the composite foundation is put forward. The results obtained by this method are compared with the field test results of a highway project in Guangdong Province, and combined with the finite element analysis, the feasibility and correctness of the proposed method are proved, which can be used for reference in practical engineering. Finally, this paper simulates the vertical load of a new type of tetragonal cylindrical pile by using Abaqus software, and analyzes the characteristic law of load transfer of thin-walled cylindrical pile with ribs. The surface friction at the lateral side of the rib is faster than that on the side of the rib and the circumference. At the same time, the influence of the length and width of the rib on the bearing capacity is discussed in detail. The results show that the rib length has a significant effect on the vertical bearing capacity, and the rib width has little effect on the bearing capacity. The existing formulas for calculating the bearing capacity of cylindrical piles are modified, and the formulas for calculating the ultimate bearing capacity of cylindrical piles with ribs are put forward, which provides a reference for the application in engineering in the future.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU470
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