小直径钢管排桩抗滑机理及计算方法研究

发布时间：2018-02-24 02:08

本文关键词： 边坡工程小直径钢管桩排桩抗滑机理计算方法承载力影响因素失效准则　出处：《西南交通大学》2013年博士论文　论文类型：学位论文

【摘要】：小直径钢管排桩作为新型边坡支挡结构,具有施工快捷安全、承载力强、加固见效快、经济效益好等优点。由于缺乏抗滑机理、计算方法等方面的系统研究,严重制约了钢管排桩作为永久支挡结构的推广应用。本文利用工程桩监测试验、原型结构堆载试验、离心机模型试验、理论分析及数值模拟等手段,系统研究了钢管排桩基于桩土相互作用的受力变形规律、抗滑机理、承载力影响因素等内容,提出了力学计算模型和实用设计计算方法,为钢管排桩从应急抢险功能向永久性支挡工程推进提供了基础资料和理论基础。 1.钢管排桩支挡结构抗滑机理主要表现为：1)在钢管排桩空间框架约束下,桩间土体具有强化效应,框架内土体承载能力得到提高；2)排架土体与钢管桩协调变形,通过桩土相互作用传递荷载、形成桩土复合承载结构,大幅提高钢管排桩承载能力；3)桩间土体具有明显的土拱效应,土拱作用具有维持桩间土稳定、传递桩间荷载的作用,并通过约束排架土体,强化了支挡结构承载能力；4)压力注浆增大钢管桩刚度、改善土体性质,增强了桩土复合结构承载能力。 2.通过原型结构堆载极限破坏试验,得出了钢管排桩在试验条件下的水平极限承载能力：厚度为8-12m,以硬黏土、块石土为主的滑坡,采用直径133mm直缝钢管、间排距1.5-1.7m、钢筋砼系梁的钢管排桩进行支挡,三排桩承载力为531kN/m,两排桩承载力为390kN/m；实际应用中为确保支挡工程安全,应采用设计安全系数1.5-2,即三排桩承受水平推力一般不大于350kN/m,两排桩承受水平推力一般不大于260kN/m。 3.通过现场堆载试验、离心机模型试验及数值分析,总结出各相关因子对钢管排桩承载能力影响规律：增加钢管桩排数可增大支挡结构承载能力；桩间距与桩径之比L/d15时,桩间土通过土拱作用维持稳定,同时为避免出现群桩效应,L/d宜≥8；排距与直径之比b/d为6-12时,桩土复合作用发挥最充分,支挡结构支护能力最强,为避免出现群桩效应,b/d宜≥8；强刚度系梁具有协调钢管桩内力、约束土体加强桩土复合承载的作用；桩间土体物理力学性质越好,桩土复合作用发挥越充分,支挡结构抗滑能力越强。 4.小直径钢管排桩在水平荷载作用下,排架内土体与钢管桩协调变形；排架土体通过桩土相互作用将水平荷载q传递至其他排桩,各排桩承受荷载qi分布规律与q致,量值为qi=ξq,对于三排桩,ξ1=0.95,ξ2=0.90,两排桩ξ1=0.94,ξ2=0；小直径钢管排桩骨架结构可假定为承受水平荷载q、桩间土传递荷载qi、桩前土体抗力p(少,z)、锚固段抗力p'(y,z)的平面刚架模型,其中桩前土体抗力p(y,z)采用p-y曲线描述,锚固段抗力p'(y,z)采用线性弹簧模拟。 5.对考虑桩土复合作用的平面刚架计算模型,分别采用弹性地基梁法、p-y曲线法进行内力变形计算,通过与实测资料对比分析,p-y曲线法计算结果与实测值吻合较好,同时该法充分反应了土体弹塑性特征,计算便捷,可作为工程应用推广。 6.根据钢管排桩抗滑机理、计算方法研究成果,提出了支挡结构按承载力和位移控制的失效准则、实用设计计算方法及步骤、适用条件。 7.结合工程实践研究了钢管排桩作为永久结构的接管技术和长效防腐方法：钢管接管技术可采用三截面内衬管搭接式焊接法(己获国家实用新型专利,专利号：ZL201220616390.1)；防腐方法可采用钢管外壁热喷涂锌,结合管外砂浆包裹隔离防腐。通过工程实践应用,上述钢管连接和防腐方法可保障结构可靠性和耐久性。
[Abstract]:As a new type of small diameter steel tubular pile slope retaining structure, the construction is safe and fast, strong bearing capacity, strengthening the advantages of quick effect, good economic benefit and so on. Due to the lack of systematic research on the anti sliding mechanism, calculation methods, seriously restrict the pipe pile as a permanent retaining structure. The popularization and application of the project piling monitoring test prototype structure loading test, centrifuge model test, theoretical analysis and numerical simulation, the system of steel pipe piles based on the soil pile interaction force and deformation, the anti sliding mechanism, bearing capacity factors etc., put forward the mechanical calculation model and practical design method for steel pipe. Pile from emergency rescue function to permanent retaining engineering in advance to provide basic data and theoretical basis.
1. pipe pile retaining structure anti slide mechanism mainly as follows: 1) in pipe pile space frame under the constraint of soil between piles with reinforcement effect, within the framework of soil bearing capacity is improved; 2) bent steel pipe pile soil and coordinated deformation and load transfer through the pile soil interaction, the formation of the pile composite bearing the structure, greatly improve the bearing capacity of steel pipe pile; 3) soil has obvious soil arching effect, soil arching effect can maintain the stability of soil between piles, pile load transfer function, and the constraint frame soil retaining structure, strengthening capacity; 4) increase the stiffness of steel pipe pile pressure grouting and improve the properties of soil, enhance bearing pile composite structure.
2. the prototype structure load ultimate failure test, the ultimate horizontal pipe pile under the condition of test bearing capacity: thickness of 8-12m, with hard clay, stone soil landslide, with the diameter of 133mm pipe, spacing 1.5-1.7m, steel reinforced concrete beam pile for retaining three. Pile bearing capacity is 531kN/m, two rows of pile bearing capacity is 390kN/m; in order to ensure the safety of retaining engineering in practical application, should adopt the design safety factor of 1.5-2, namely the three row pile under horizontal thrust is generally not more than 350kN/m, two rows of pile under horizontal thrust is generally not more than 260kN/m.
3. through field loading test, model test and numerical analysis of centrifuge, summed up the related factors of pipe pile bearing capacity influence: increasing the row number of steel pipe pile retaining structure can increase the bearing capacity of pile spacing and pile diameter; the ratio of L/d15, the soil arching effect of soil between piles is stable, appear at the same time group in order to avoid the effect of pile, L/d should be equal to or greater than 8; row spacing and diameter ratio of b/d is 6-12, the pile composite function fully, retaining structure supporting ability is the strongest, appear to avoid the pile group effect, b/d should be greater than or equal to 8; the strong stiffness beam has the coordination of steel pipe pile internal force, soil pile strengthening constraints the effect of pile soil composite bearing; physical and mechanical properties of soil as the pile composite role more fully, retaining structure of anti slide ability is stronger.
4. small diameter steel pipe piles under horizontal loads, the soil inside the frame and steel pipe pile deformation; bent soil by soil pile interaction to horizontal load Q transmission to other rows of piles, each pile load distribution of Qi and Q, qi=. Q value, for the three row pile. 0.95. 1=, 2=0.90., two rows of piles. 1=0.94. 2=0; small diameter steel pipe piles can be assumed as a skeleton structure under the horizontal load Q, soil load transfer Qi between piles, pile soil resistance of P (small z), anchorage resistance of p'(y, z) plane frame model. The anterior surface of the pile resistance of P (y, z) by p-y curve description, anchoring force p' (y, z) by using the linear spring element.
5. to consider the interaction of soil pile composite plane frame model, using elastic foundation beam method, p-y curve method to calculate the internal forces and deformation, through analysis and comparison with the field data. The calculation results agree well with the measured values of p-y curve method, while the method fully reflects the elastoplastic characteristics, calculation is convenient, can be used as engineering application.
6., according to the research results of the slide resistance mechanism and calculation method of steel pipe piles, the failure criterion of supporting structure according to the bearing capacity and displacement control is put forward, and the practical design calculation methods and steps, and applicable conditions are put forward.
7. combined with the engineering practice of steel pipe pile as a takeover and anticorrosive method of permanent structure: steel pipe technology can adopt three section liner lap welding method (has won the national utility model patent, patent number: ZL201220616390.1); anticorrosion methods can be made of steel tube thermal spraying zinc binding mortar wrapped isolation tube anticorrosion. Through the application of engineering practice, the steel pipe and anticorrosion method can ensure the reliability and durability of the structure.

【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU473.1

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