深基坑双排桩支护结构体系若干问题分析和研究

发布时间：2018-01-28 04:20

本文关键词： 双排桩滑裂面冠梁刚度空间效应影响长度稳定加固　出处：《华南理工大学》2013年博士论文　论文类型：学位论文

【摘要】：双排桩支护结构是近年来兴起的一种新型深基坑支护结构,其侧向刚度大,能有效控制支护结构的变形,而且受力条件和整体稳定性好、施工方便,逐渐成为深基坑支护结构的优选方案之一。国内外学者对双排桩支护结构进行了大量的研究,研究成果对实际工程中的许多方面具有很好的指导意义,但由于双排桩支护结构受力复杂,在一些方面实践先行,理论滞后,从而限制了该种支护结构的发展。目前阶段而言‘,在考虑桩顶冠梁平面外实际刚度计算方面、空间效应冠梁的影响长度方面、不同潜在滑动面安全系数的极限平衡数值积分求解方面、滑动面的分布规律以及基坑加固等方面研究有所欠缺,本文在归纳整理了现有双排桩支护结构体系的国内外研究成果基础上,基于均质粘性土层的地质条件,通过理论推导、分析和数值模拟等方法,对深基坑双排桩支护结构体系研究中存在的上述薄弱环节进行了有益的补充和完善,本文主要开展的研究工作和成果如下： 1.提出了考虑冠梁平面外实际刚度计算双排桩支护结构的内力和变形的理论计算方法,并对比分析冠梁平面外假设无限刚与实际有限刚对桩身内力和位移的影响。该方法基于winkle假定,引入冠梁平面外实际刚度的影响因素,对双排桩支护结构进行理论分析,在此基础上建立各段桩体的挠曲微分方程,然后根据各段桩体端点在几何变形和内力上的连续性关系以及相应的边界条件,采用数学近似方法幂级数求解各段挠曲微分方程,并求导各段挠曲方程的解得出双排桩各点的内力及变形,通过分析冠梁平面外假设无限刚与实际有限刚的计算结果可以得出：1)冠梁的刚度增大可减少前、后排桩的位移,但会增大前、后排桩桩身弯矩；2)冠梁刚度的变化对后排桩桩身弯矩的影响比前排桩稍大；3)冠梁的刚度变化对桩身弯矩的影响幅度和对位移的影响幅度比较接近。该方法与现行假设冠梁无限刚的理论计算方法相比更符合工程实际情况,为考虑冠梁实际刚度求解双排桩的变形和内力提供了一种可行的理论计算方法； 2.对双排桩支护结构进行了三维数值模拟,研究了双排桩支护结构在空间效应下的受力和变形特性,在此基础上,研究了冠梁与支护桩的刚接和铰接连接方式、基坑的长边长度、短边长度、开挖深度、冠梁刚度、土层粘聚力和摩擦角、支护结构排距和桩距等主要设计参数与空间效应冠梁影响长度的关系,通过分析不同参数变化下的冠梁影响长度的规律得出：基坑短边长度、开挖深度和支护结构排距的变化对冠梁影响长度都有较大影响；基坑长边长度、粘聚力、摩擦角、冠梁刚度以及支护结构桩距的变化对冠梁的影响长度影响很小。 3.提出了双排桩支护基坑在不同潜在滑动面的简化整体稳定安全系数积分计算方法,该方法以Bishop法原理为基础,建立适用于深基坑双排桩支护结构稳定分析的简单平面直角坐标系,推导出潜在滑动面经过基坑底部与前排桩交点圆弧等位置的简化整体稳定分析的安全系数积分表达式,并考虑可能出现的主动区、桩间土和被动区加固的情况,完善了安全系数在不同积分区间的积分表达式,然后编制了相应的计算程序计算基坑稳定安全系数,通过计算结果的分析可以得出,滑动面经过基坑底部与前排桩交点圆弧的安全系数为F1,滑动面经过前排桩桩底圆弧的安全系数为F2,滑动面经过后排桩桩底圆弧的安全系数为F3,而F1略大于F2,F2略大于F3,与有限元计算结果进行对比分析,验证了所提出方法的可行性,完善了极限平衡法数值积分求解安全系数在深基坑双排桩支护结构中的应用。 4.对双排桩支护结构的基坑稳定性进行了数值分析,系统研究了基坑稳定安全系数随土层的粘聚力、摩擦角以及支护结构的桩长和排距等设计参数而变化的规律得出：基坑的稳定安全系数随着粘聚力、摩擦角、支护结构桩长和排距的增加而增加,稳定安全系数受粘聚力和摩擦角的影响最大,受支护结构桩长的影响较大,受支护结构排距的影响较小。并且,总结了滑动面的分布特点和规律。 5.对双排桩支护的基坑进行加固分析,系统研究了主动区、桩间土和被动区加固对桩身内力和变形特性的影响后得出：1)对于主动区加固,当加固深度超出基坑深度,加固效果不明显；2)对于被动区加固,加固深度或宽度约为基坑深度的一半时最有效。 6.在以上工作基础上提出进一步开展相关研究工作的建议。
[Abstract]:The double - row pile supporting structure is a new kind of deep foundation pit supporting structure which has arisen in recent years . The lateral rigidity is large , it can effectively control the deformation of the supporting structure , and the stress condition and the whole stability are good , the construction is convenient , and it becomes one of the preferred schemes of deep foundation pit supporting structure . On the basis of summarizing the research results of the existing double - row pile support structure system , this paper makes a useful supplement and improvement to the weak links existing in the research of the double - row pile support structure system of deep foundation pit . The main research work and results are as follows : 1 . The theoretical calculation method for calculating the internal force and deformation of the double - row pile supporting structure considering the actual rigidity outside the plane of the crown beam is put forward , and the influence factors on the internal force and displacement of the pile body are analyzed . Based on the assumption of winkle assumption , the deflection differential equations of the two rows of piles are obtained . 2 . Based on the three - dimensional numerical simulation of the double - row pile supporting structure , the stress and deformation characteristics of the double - row pile supporting structure under the space effect are studied . Based on this , the relationship between the main design parameters of the crown beam and the supporting pile , the length of the long side of the foundation pit , the length of the short side , the depth of excavation , the row spacing of the foundation pit and the influence length of the crown beam are studied . The influence of cohesive force , friction angle , crown beam rigidity and support structure pile spacing on crown beam is very small . 3 . Based on Bishop ' s method principle , the integral expression of safety factor for the stability analysis of double - row pile supporting structure of deep foundation pit is established . The safety factor of the sliding surface passing through the arc of the bottom of the foundation pit and the intersection of the front row piles is F1 , the safety factor of the sliding surface passing through the arc of the bottom of the front row pile is F2 , the safety factor of the sliding surface passing through the bottom arc of the front row pile is F2 , the safety factor of the sliding surface passing through the bottom arc of the front row pile is F2 , the safety factor of the sliding surface passing through the bottom arc of the front row pile is F2 , the safety factor of the sliding surface passing through the bottom arc of the front row pile is F2 , the safety factor of the sliding surface passing through the bottom arc of the front row pile is F1 , the safety factor of the sliding surface passing through the bottom arc of the front row pile pile is F2 , the safety factor of the sliding surface passing through the bottom arc of the front row pile pile is F1 , the safety factor of the sliding surface passing through the bottom circular arc of the front row pile is F1 , the safety factor of the sliding surface passing through the circular arc of the front row pile pile is F1 , the safety factor of the sliding surface passing through the circular arc of the front row pile is slightly larger than F3 , and the application of the safety factor in the double - row pile supporting structure of the deep foundation pit is improved by improving the numerical integral solution safety factor of the limit equilibrium method . 4 . Based on the numerical analysis of the stability of the foundation pit of double row pile supporting structure , it is found that the stability safety factor of the foundation pit increases with the increasing of cohesive force , friction angle and pile length and distance of the supporting structure . The stability safety factor of the foundation pit increases with the increasing of cohesive force , friction angle , length and distance of the support structure . The stability safety factor is affected by the cohesive force and friction angle . 5 . After strengthening and analyzing the foundation pit supporting double - row piles , the influence of active area , pile - to - soil and passive area reinforcement on the internal force and deformation characteristics of pile body is studied . The results show that : 1 ) For the active area reinforcement , when the reinforcement depth exceeds the depth of the foundation pit , the reinforcement effect is not obvious ; 2 ) For the reinforcement of the passive zone , the reinforcement depth or width is about half of the depth of the foundation pit . 6 . On the basis of the above work , a proposal to further carry out the relevant research work is proposed .

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU753

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