【作者】 向波；

【导师】 马建林；

【作者基本信息】 西南交通大学 ， 岩土工程， 2013， 博士

【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/d<15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。更多还原

【Abstract】 As a new type of slope retaining structure, small diameter steel pipe row-pile has advantages of fast and safe construction, strong bearing capacity, fast retaining effect, and good economical benefits. Due to lacking systematically researches of anti-sliding mechanism and calculation method etc, it is severely restricted to be a permanent retaining structure. Making use of field pile monitoring test, prototype pile loading test, centrifuge model test, theoretical analysis and numeral analysis etc, based on pile-soil interaction, the stress and deformation law, anti-sliding mechanism, factors relevant to bearing capacity of the row-pile were studied systematically, the mechanical computation model and practical design and computational methods were put forward which provided basic data and theoretical foundations for the application of the row-pile from emergency to permanent slope retaining.1. The anti-sliding mechanism of steel pipe row-pile was as follows:1) Under the restriction of row-pile space frame, the soil body was in three-dimension stress state, the stress strengthening effect enhanced the soil between piles;2) The deformation of the soil body in bent frame coordinated with the row-pile, through pile-soil interaction, the load distributed between soil and piles made the soil and piles a composite bearing structure, which improved the bearing capacity of the steel pipe row-pile structure;3) There was clear anchoring effect in soil between piles which sustained the stability of soil between piles, distributed pile loading and reinforced the bearing capacity of retaining structure through restricting soil in bent frame;4) The pressure grouting reinforced the pile stiffness, improved the soil quality, strengthened bearing capacity of the pile-soil composite structure.2. Through field prototype pile loading test, horizontal bearing capacity of the row-pile was obtained. For8-12m thick landslide mainly with hard clay or rubble, the retaining structure was steel pipe row-pile with reinforced connection beam, the diameter of the steel pipe was133mm, the space between piles or rows of piles was1.5-1.7m, the bearing capacity of triple and double rows were respectively531kN/m and390kN/m. For the safety of the retaining structure, the general bearing capacity of triple and double rows of piles were respectively not more than350kN/m and260kN/m.3. Through field pile loading test, centrifuge model test and numeral analysis, the influence rules relevant parameters to bearing capacity of the row-piles:setting more rows of steel pipe row-pile would make the retaining system stronger; when ratio between pile space and pile diameter L/d/15, the soil between piles remained stable because of anchoring effect, meanwhile, group pile effect was avoided, L/d should not be less than8; when ratio between row space and pile diameter b/d is6-12, the pile-soil composite was in perfect effect, the retaining structure was strongest, in order to avoid group pile effect b/d should not less than8; the strong stiff connection beam could coordinate the pile internal force, restrict soil and reinforce pile-soil composite bearing capacity; the better the physical and mechanical property of soil were, the more sufficient the pile-soil composite effect revealed, the stronger the anti-sliding capacity of the retaining structure was.4. Under horizontal loading, the row-pile stress and deformation law based on pile-soil interaction is:the soil and row-pile deformed coordinate in the bent frame with nearly the same value and rule; through pile-soil interaction, the bent frame soil passes the horizontal loading q, which acts on the back row-pile, on to the middle and front row-pile, the load distribution pattern of the middle and front row-pile are the same with the horizontal loading q, the values are respectively q1=ξ1q、q2=ξ2q, for triple row-piles, ξ1=0.95, ξ2=0.90, for double row-piles, ξ1=0.94, ξ2=0; there is relative displacement between piles and soil between piles, through stress adjustment, the soil anchoring effect is clear.5. For plane rigid frame model considering pile-soil composite interaction, beam on elastic foundation method and p-y curve method were adopted respectively to calculate the internal force and deformation, through comparative analysis with field data, the results calculated by p-y curve method coincided with the field data well, meanwhile, the method revealed the soil elastic-plastic characteristic sufficiently, the calculation procedure was easy, which was good for engineering application.6. According to the anti-sliding mechanism and calculation method research results of steel pipe row-pile, the retaining structure failure criterion base on bearing capacity and displacement, the design calculation and procedure were put forward.7. Combined with engineering practice, takeover technology and long-term anticorrosion method of steel pipe row-pile as a permanent structures are studied:steel pipe takeover technology can adopt three section liner lap welding method; anticorrosion method can adopt steel tube outer wall thermal spray zinc, combined with the pipe anti-corrosion mortar wrapped isolation. Through the engineering practice, the steel pipe takeover and anticorrosion methods described above can guarantee the reliability and durability of the structure.更多还原