双排桩支护结构的数值分析与现场试验研究

发布时间：2018-01-03 09:38

本文关键词：双排桩支护结构的数值分析与现场试验研究　出处：《太原理工大学》2013年博士论文　论文类型：学位论文

【摘要】：随着我国经济的迅速发展和城市化进程的加快,高层、超高层建筑、城市地铁隧道项目大量的建设,都遇到一个共同的问题：深基坑的设计及施工问题,如基坑支护、降水、开挖等等。特别是,近年来有关基坑土方坍塌的事故频频发生,给人民的生命及财产安全造成巨大的影响。因此,如何解决好城市建设项目中的基坑支护及环境效应问题成为岩土工程的热点与难点,技术安全、经济合理的基坑支护结构体系是基坑工程的主要发展方向及研究重点。双排桩支护结构由于具有整体刚度大、侧向位移小、不需要设置支撑、施工方便、速度快、不需要工作面等优点,目前广泛应用于边坡加固、边坡抗滑、基坑支护等工程中。但是,双排桩的作用机理及受力特征目前还不清楚,双排桩的设计理论不成熟,主要依靠工程经验。本文在总结前人研究的基础上,以数值模拟与现场试验为研究手段,理论分析方法与工程实践相结合,全面研究双排桩支护结构的要素设计和复合式双排桩的受力及变形特征,研究双排桩的作用机理、探讨土压力的分配规律、分析支护结构的内力及变形规律、对比不同支护方案下的安全性、经济性,为双排桩支护结构的广泛应用及优化设计提供理论支持与工程经验。本文的主要研究内容如下： 1.回顾总结双排桩支护结构的理论计算方法,对比总结各自的特点及应用范围。 2.采用FLAC3D数值法模拟双排桩结构的受力状态,研究双排桩支护结构的要素设计,包括：桩距、排距、直径、长度、连梁截面及刚度、基坑深度、土体抗剪强度指标等,寻求双排桩设计最优参数。 3.采用FLAC3D数值法模拟复合式双排桩支护结构的受力特征,研究不同复合方案下支护结构的内力及变形规律,分析基坑工程的安全系数,并将研究成果应用于太原市平阳景苑的深基坑支护工程中。 4.将理论研究应用于实践工程中,详细阐述了平阳景苑深基坑支护工程的设计思路、支护选型、模拟计算、方案比选,并最终确定支护方案,为该地区同类基坑工程支护设计提供借鉴。 5.针对平阳景苑的深基坑支护工程进行现场试验研究,编制详细的试验方案,分析研究了土层的侧向位移、桩体的内力及位移、地表的沉降及位移、锚索拉力、地下水变化、周围建筑物沉降等,并与计算结果对比。 6.采用不同三轴试验方案,重点研究了土体抗剪强度指标对支护结构受力的影响,并将不同试验方案下测定的指标值带回计算模型中,将计算结果与实测值进行比较。通过上述内容的研究,本文在以下方面取定一些研究成果： 1.研究结果表明,双排桩支护结构的内力及变形特征明显区别于单排桩,最大位移不是发生在桩顶,而是桩顶下2-4m,弯矩曲线出现反弯点,正负最大弯矩差值在减小,受力更加合理。对比结果表明,在桩数相同的条件下,采用双排桩支护结构可以明显减少位移,使结构受力更加合理。 2.首次全面分析了双排桩支护结构要素设计变化对双排桩的影响,并得出最佳设计参数：排距4～6d(d为支护桩直径),桩距2-4d,桩长1.5～2倍基坑深度,深度在10m以内采用双排桩支护比较合理,连梁必须具有足够刚度,才能发挥其协调的作用。 3.研究发现,土体抗剪强度指标c,(?)值是影响支护结构内力及变形的最重要两个因素。计算结果显示,c,(?)值变化与支护桩最大水平位移呈双曲线关系,这是本文研究的一大亮点。 4.首次将复合式双排桩支护结构引入太原地区,工程实践表明是成功的,并节约造价约3000万元,为该地区同类支护工程提供借鉴。 5.对比分析不同复合方案下双排桩支护结构的受力特点,全面研究不同组合方案的内力及变形规律。研究结果显示,设置锚索、支撑可以明显改善双排桩的受力,限制侧向位移。而同样条件下,设置支撑的支护效果优于锚索,增加锚索或支撑的排数,支护结构的内力及变形没有明显改善,最佳的锚索或支撑的排数为2排。否则的话,前排桩成为主要受力构件,整个体系类似于拉锚结构,发挥不出后排桩的作用,这是本文研究的又一亮点。 6.关于锚索的作用点位置在本文中也作了重点研究,结果显示：最佳位置是冠梁处,双排桩结构受力最合理。 7.现场试验显示,深基坑存在显著的空间效应,中间桩体侧向变形大于端部桩体,位移曲线呈“中间大、两头小”的鼓肚状。 8.对比分析多样单级加荷和单样多级加荷三轴剪切试验测定c,(?)值,研究结果显示,单样多级加荷下测定的c,(?)值偏大,内力及变形值的计算结果与实测结果更接近。查阅文献,还没有找到类似的研究。
[Abstract]:With the rapid development of China ' s economy and the acceleration of urbanization , a common problem is encountered : the design and construction of deep foundation pit , such as foundation pit support , precipitation , excavation , etc . The double - row pile supporting structure has the advantages of large integral rigidity , small lateral displacement , no need of setting support , convenient construction , high speed , no need of working face and the like , and is widely applied to the engineering of slope reinforcement , slope anti - sliding , foundation pit support and the like . 1 . The theoretical calculation method of double - row pile supporting structure is summarized , and the characteristics and application range are summarized . 2 . Using FLAC3D numerical method to simulate the stress state of double - row pile structure , the element design of double - row pile supporting structure is studied , including pile spacing , distance , diameter , length , cross - section of connecting beam and rigidity , foundation pit depth , soil shear strength index and so on , and seek the optimal parameters of double - row pile design . 3 . Using FLAC3D numerical method to simulate the stress characteristics of the composite double - row pile support structure , the internal force and deformation law of the support structure under different composite schemes are studied , the safety factor of the foundation pit engineering is analyzed , and the research results are applied to the deep foundation pit support project of Pingyangjing Yuan in Taiyuan City . 4 . The theory research is applied to the practical engineering , and the design thinking , the supporting type selection , the simulation calculation and the scheme selection of the supporting project of the deep foundation pit in Pingyangjing Court are described in detail , and the supporting scheme is finally determined , which provides reference for the support design of the similar foundation pit in the area . 5 . According to the field test research of the deep foundation pit support project of Pingyangjing Court , a detailed test plan is prepared , the lateral displacement of the soil layer , the internal force and displacement of the pile body , the settlement and displacement of the surface , the tension of the anchor cable , the change of groundwater and settlement of the surrounding buildings are analyzed and compared with the calculation results . 6 . Using different three - axis test scheme , the influence of soil shear strength index on the stress of support structure is studied , and the index value measured under different test schemes is brought back to the calculation model , and the calculation result is compared with the measured value . Through the research of the above - mentioned content , this paper takes some research results in the following aspects : 1 . The research results show that the internal force and deformation characteristics of the double - row pile support structure are obviously different from the single - row pile , but the maximum displacement is not taking place at the top of the pile but 2 - 4m at the top of the pile , the difference between the positive and negative maximum bending moment is reduced and the stress is more reasonable . The comparison result shows that the double - row pile supporting structure can obviously reduce the displacement under the same condition of the pile number , so that the stress of the structure is more reasonable . 2 . For the first time , the influence of the design change of double row pile supporting structure on double row piles is analyzed . The best design parameters are as follows : the distance from 4 to 6d ( d is the diameter of the branch pile ) , the pile distance is 2 to 4d , the pile length is 1.5 to 2 times the depth of the foundation pit , the depth is within 10m , the double row pile support is reasonable , and the connecting beam must have sufficient rigidity to play its coordinating role . 3 . It is found that the shear strength index of soil is c , ( ? ) ? The value is the most important factor affecting the internal force and deformation of the supporting structure . The results show that c , ( ? ) There is a hyperbolic relationship between the variation of the value and the maximum horizontal displacement of the supporting pile , which is a highlight of the study . 4 . For the first time , the composite double - row pile supporting structure is introduced into Taiyuan area , the engineering practice shows that it is successful , and the cost is saved by about 30 million yuan , which can be used for reference for similar support projects in the area . 5 . In this paper , the internal force and deformation law of the double - row piles are studied . The results show that the supporting effect is better than that of the anchor cable , the internal force and the deformation of the supporting structure are not improved obviously , and the optimal anchorage cable or the supporting row number is 2 rows . Otherwise , the front row pile becomes the main force - bearing member . Otherwise , the whole system is similar to the pull - down anchor structure , so that the effect of the rear - row pile is not exerted , and this is still another bright spot in this paper . 6 . The point of action of the anchor cable is also studied in this paper . The result shows that the best position is the crown beam , and the stress of the double - row pile is the most reasonable . 7 . On - site test shows that the deep foundation pit has obvious spatial effect , the lateral deformation of the intermediate pile body is larger than that of the end pile body , and the displacement curve is in the form of " middle large , two small " drums . 8 . Comparison and analysis of various single - stage loading and single - sample multi - stage loading triaxial shear tests c , ( ? ) The results show that the c , ( ? ) ? The results show that the results are closer to the measured results than the measured results . A similar study has not been found in the literature .

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

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