【作者】 何云勇；

【导师】 马建林；

【作者基本信息】 西南交通大学 ， 岩土工程， 2012， 硕士

【摘要】 小直径钢管排桩这一新型环保边坡支挡结构具有加固见效快、横向承载力较强、施工快捷安全、经济效益好等优点。由于缺乏其支挡抗滑机理、桩土作用、计算方法等方面研究,严重制约了作为永久支挡结构的应用。本文利用理论分析、试验验证和数值分析等手段,主要研究了小直径钢管排桩的抗滑机理、实用设计计算方法和承载力影响因素,得出了以下研究成果：1.小直径钢管排桩加固边(滑)坡的抗滑作用机理表现为：一是钢管桩骨架体系具有优良的抗剪、抗拉、抗压性能可抵御较大推力,并约束桩间岩土体,使其体处于三向应力状态,土体强度得到了较大提高；二是刚度较大的钢筋混凝土系梁具有较好协调、传递内力作用,“强梁弱桩”的组合结构与桩前土体共同发挥较强支挡能力；三是高压注浆对钢管桩桩体、桩周土体固化增强。2.根据小直径钢管排桩的受力特点,给出了考虑桩土相互作用空间效应的平面刚架分析模型,基于Winkler弹性地基梁理论,推导了桩身内力变形计算公式；由桩间“抗剪切土体”的溜出检算,得出了钢管桩合理桩间距的计算公式；给出了小直径钢管排桩按抗拔和受弯曲条件确定锚固深度的计算方法；在此基础上,提出了小直径钢管排桩十五步设计法。3.桩间距与桩径之比L/d在5～15变化时,排桩的抗滑能力不断下降,L/d=15时桩间土已发生溜出破坏。经过不同桩间距排桩内力变形的对比分析,并结合大量实际工程经验：对于非软塑-流塑状粘性土、混合土,建议L/d取5～12即桩间距取1～2m,桩土相互作用能较好的发挥抗滑能力。4.当钢管排桩后推力较小时,钢管桩内力变形随排间距增大变化微弱,随着荷载增大,内力变形随钢管桩排间距增大表现出先增大后减小的规律,排间距在1m～2m即b/d为6～12时,与其它排间距相比,桩土复合体发挥的抗滑力增大。因此,考虑忽略排间的群桩效应,建议b/d取值为8～12即1～2m。5.锚固段长度对钢管排桩的水平位移影响较小,而对锚固段的内力影响较大,随着锚固段长度增大,桩体锚固段内力逐渐减小。当h/l在1/4～1/3变化时,排桩受力较为合理,建议钢管排桩锚固长度控制在1/4～1/3。6.桩间岩土层物理力学参数黏聚力c、内摩擦角φ、压缩模量E对桩岩土复合体的抗滑能力影响较大,随着c、φ、E增大,桩前抗力增大,土拱效应也越明显,相应的排桩提供抗滑力增大,其中桩周土体压缩模量E影响最为明显。更多还原

【Abstract】 Small diameter steel pipe row-pile is a new type of environmental slope retaining structure which has advantages of fast retaining effect, strong horizontal bearing capacity, quick and safe construction and good economical benefits. Due to lacking researches of anti-sliding mechanism, pile-soil acting mechanism and calculation method etc, it is severely restricted to be a permanent retaining structure. Making use of theoretical analysis, calculation proof and numeral analysis etc, the anti-sliding mechanism, practical design and calculation method and factors relevant to bearing capacity are studied in this article, the results are as follows:1. The mechanism of small diameter steel pipe row piles register as:firstly, the steel row-pile skeleton system has excellent properties of shearing resistance, tensile resistance and compressive resistance etc, which could withstand a comparatively large thrust and restrict rock and soil mass among piles into a triaxial state of stress which comparatively increases the soil strength sharply; secondly, the concrete coupling beams with strong stiffness have good coordination and transfer effect of internal forces, the combination of "strong beams and weak piles" and the soil body in front of the row-piles have a comparatively strong resistance effect; finally, high pressure grouting solidify the piles and soil, which makes them stronger.2. According to forcing characteristics of small diameter steel pipe row-pile, plane rigid frame model considering pile-soil three-dimensional effect is put forward. Based on Winkler beam on elastic foundation theory, deformation computation formula of pile internal force is derived; reasonable pile spacing is obtained from "anti-shearing soil body" sneak out calculation; the anchorage depth calculation method is derived from row-pile anti-plucking and anti-bending factors; on the basis of those formula, fifteen-step design method of small diameter steel pipe row-pile is raised.3. when the ratio between pile spacing and pile diameter L/d is5-15, the row-pile anti-sliding capacity is declining, when L/d=15, soil among row-pile is sneaking out. Through row-pile internal force and deformation comparative analysis of different row spacing combined with mass engineering projects experiences:for non-soft plastic to fluid plastic cohesive soil, composite soil, the value of L/d is suggested5~12, that is pile spacing is1-2m, pile-soil could bring comparatively good anti-sliding capacity.4. When the thrust behind row-piles is comparatively small, the variance of pile internal force and deformation is very small along the increase of pile spacing, but along the increase of load, the internal force and deformation represents from increase to decrease along the increase of pile spacing, when pile spacing is1~2m, that is b/d is6-12, compared with other row spacing, pile-soil composite body display a larger anti-sliding. So, considering the group pile effect ignoring row spacing, the value b/d is suggested8-12, that is1~2m.5. The row-pile horizontal displacement is influenced comparatively small by anchorage depth, yet, the row-pile internal force of anchorage section is influenced comparatively large by anchorage depth, the internal force decreases along the increases of anchorage depth. When h/l varies from1/4-1/3, the internal force of row-pile is much reasonable, it is suggested that anchorage depth should be controlled into1/4-1-3.6. The anti-sliding capacity is largely influence by cohesion c, internal friction angle φ, modulus of compression E, along with the increase of c, φ, E, the resisting force in front of row-pile is increasing, the soil anchoring effect is more obvious, correspondingly, the row-pile resisting force is increasing, among c, φ, E, E is the most obvious effective factor.更多还原