【作者】 蒋良潍；

【导师】 黄润秋；

【作者基本信息】 成都理工大学 ， 地质工程， 2006， 博士

【摘要】 随着国民经济的飞速发展，工程建设规模越来越大、速度越来越快，出现了日渐增多的斜坡体变形及失稳破坏问题。对松散斜坡体的加固和变形控制措施是此类地质灾害防治工程的研究重点，历来为学术界、工程界所关注，缘其涉及较多岩土工程基本问题，以及岩土工程与地质工程的大量广泛结合。其中，预应力锚索、预应力锚索桩等新型结构是加固松散斜坡体实用、有效的工程措施，在斜坡体整治工程中得到了广泛的应用，然而其理论研究仍远远滞后于工程应用。锚、桩加固作用机理和计算理论的研究，具有较重大的理论和工程意义。本文根据大型松散体滑坡治理中的代表性工程措施类型，以理论推导、数值计算和实例分析等手段，探索了预应力锚索锚固段与岩土体的相互作用与传力机理、外锚结构与松散岩土的相互作用与传力特征、锚索桩与岩土体相互作用机理与计算理论、松散岩土体支挡结构的主动土压力分布模式、松散岩土桩间土拱效应及桩间距计算等锚、桩工程的理论问题。本文的主要研究内容和成果如下：1．针对预应力锚固结构的内锚固段设计理论落后于工程实践的现状，对锚固体与岩土体的侧阻相互作用力学机理及相应侧阻力分布规律计算进行研究。分析了锚固段孔壁侧阻界面全程严格粘结假设的局限性，通过引入侧阻界面力学作用的滑移—软化关系模型，分别以荷载传递法理论分析和基于Mindlin位移解的一维非线性半数值分析，对锚固体侧阻力的单峰分布规律曲线进行了研究。同时，指出了以Mindlin位移解推求锚固段侧阻力分布方法中存在的奇异性问题，从严格数理力学角度探讨了目前侧阻力分布理论推导所具有的近似性，即奇异性的处理将影响计算结果的精准性。2．采用FLAC-3D数值分析简化模型，探索了松散斜坡体坡表上布置锚墩墩排及锚墩—地梁组合结构与岩土体的相互作用力学机理、锚固传力特性的特点和差异：墩间距较小情况下，锚墩墩排的墩间土体最大主应力发生倒拱形偏转(“土拱效应”)，对墩间土体反力具有一定遮拦作用，而锚墩—地梁组合结构对墩下压应力扩散及张拉沉陷的改善程度不大，土拱效应不能出现，地梁承受墩间土体反力。墩间距较大时，墩间土体最大主应力等值线偏转呈马鞍形，成拱作用差，设置地梁效果较好。此外，对锚墩结构与松散岩土体相互作用体现的另一问题，即因施工工期紧迫而采用的锚索钢绞线逐根张拉工序问题进行了研究，建立了分次张拉同时的锚墩沉陷所致锚索预应力损失和钢绞线预应力不均的估算模型。3．针对松散体滑坡常用的锚索桩工程计算，引入嵌入段桩周岩土抗力的双参数力学模型，并考虑结合“虚点法”进行改进以适合更广泛的滑动面处地基系数不为0情形。提出了锚索桩在锚索张拉后的主动支护作用及桩身初始内力计算方法，及正常工作状态的锚索桩计算统一模型和方法。进一步，考虑能反映嵌入段桩周土实际存在的弹—塑性(或非线性弹性)非线性力学特性的p-y曲线，提出了嵌入段非线性p-y曲线模式下的锚索桩计算模型。4．探讨了锚索桩嵌入段刚／弹性桩计算模型的力学统一性，推导了针对锚索桩嵌入段刚／弹性桩的新划分依据，提出桩上锚索存在最佳倾角以及桩身弯矩平衡设计理论具有条件性限制的基本概念，以清晰锚索桩设计计算中的上述重要力学概念。5．支挡结构土压力受填土性质、结构类型、墙体位移、破裂面形态、施工顺序等不易精确掌握的因素的复杂影响，很难正确计算。依据松散岩土体多种刚性半刚性支挡结构的主动土压力分布实测资料(南昆铁路路基工程试验)，归纳了松散或软弱岩土体刚性半刚性支挡结构的主动土压力抛物线分布规律，并提出了方便计算的土压力简化图式。6．针对松散斜坡体常为带一定粘性的岩土体情形，基于抗滑桩桩间岩土的“土拱效应”，利用合理拱轴线与受压极限破裂方位角等几何特性，将土拱的平衡条件和强度条件综合，以常用且易得到的土工参数c，φ，推导了桩间距上下限的计算式，以尽可能少的参数和简洁的表达式，对合理桩间距的的估算提供简便清晰的计算方法。7．结合四川丹巴建设街后山大型松散体滑坡工程实例，分析了滑坡的机理，探索了基于滑坡变形、滑动机理，考虑应力、形变场特征的锚、桩工程布置方法，并对加固松散斜坡体的作用和效果进行了初步探讨。更多还原

【Abstract】 With further economic growth, the large-scale construction engineering isundergoing rapid growth. There are more and more geological problems, such asdeformation, instabilization, collapsing or sliding of slopes. The reinforcing anddeformation controlling is an emphasis in remediation works for slopes, and theyare paid attention by academia and engineer. Because reinforcing and deformationcontrolling for slopes related to a good deal of geotechnical essential problems,they associated geotechnical engineering and geological engineering extensively.Among the remediation works, prestressed anchor cables, stabilizing piles withprestressed anchor cables are practical and effective measures, which nowadayshave a wide application in many fields. However, the studies on theory of theseworks are delayed greatly than their applications. The mechanism and calculatingtheory of reinforcing and deformation controlling using prestressed anchor cablesor stabilizing piles with prestressed anchor cables are important to theory study andpractical engineering.In this thesis, according to styles of remediation works in large-scale soft orloose bed landslide, by theory study, numerical simulation and practical examplecalculation, some geotechnical essential problems are studied. Such as follows: theinteractional action between soils and anchorage section of pretressed anchorcables, and mechanism of the load-transfer along anchorage section; theinteractional action between soils and outside bearing structures, and mechanism ofthe load-transfer; the interactional action between soils and stabilizing piles withprestressed anchor cables, and their calculating theory; the distribution map formsof active earth pressure on retaining structures in soft or loose soils; soil archingeffect between adjacent piles and their spacing in loose cohesive soils.Major research works and the conclusions are summarized as follows:1. The mechanism of interactional action between soils and anchorage sectionofpretressed anchor cables, and the distribution of lateral shear stress were studied.At first, the limitation of hypothesis of thorough gluing bond between soils andanchorage section in academic analysis is analyzed. Then, based on load transfermethod and one-dimensional semi-mechanical nonlinear model inducted Mindlin’sdisplacement solution of elastic semi-infinite, the distribution of lateral shear stress was studied respectively. Furthermore, the singularity in deducing the lateral shearstress distribution based on Mindlin’s displacement solution was discussed. Themanagement of singularity influenced the precision of calculating result, andprecise theoretical analysis from exact mechanical model can’t be carried out yet.2. Based on the FLAC-3D numerical simulation, the interactional actionbetween soils and outside bearing structures was analyzed. It was compared usinganchor blocks and using anchor block-floor beam combined system. "Soil archingeffect" may present in situation of appropriate block spaces when pre-stress loadapplied, whereas in anchor block-floor beam system, then soil arch did not form.Furthermore, another problem of interactional action between soils and outerreaction structures, the apply procedure of steel strands was discussed, when thetension load were applied one by one to steel strands of prestressed cable inemergency remediation. Based on an elastic compressing model of the subgradeunder anchor block, a model of tension load loosening and their non-uniform wasput forward.3. Based on improved biparameters elastic subgrade reaction model in theembedding section, the active defending effect and primary internal force in pileswas derived. The universal calculation model of normal working state was putforward. Furthermore, adapted to the nonlinear character of subgrade reaction inembedding section, inducted p-y curve of subgrade reaction, calculation model wasestablished.4. There are two mechanical models and respective calculating methods of theembedding section of stabilizing piles with prestressed anchor cables, which werethe rigid pile model and the elastic pile model. By means of mathematical limitanalysis, the mechanical consistency of the two calculating methods was clarified,rigid pile model’s calculating result is just only a special case of elastic pilemodel’s calculating method. Only if calculating depth of pile less than 1.3 ("mmethod") or 0.8 ("K method"), the difference between two models less than 5% andit can be taken to be new dividing criterions. The mechanical effect about dips ofpile’s anchoring cable and the condition of bending moment balance principle indesign were discussed.5. Distribution of earth pressure is an important problem in design anddifficult to calculating for many complex influent elements. According to measuredata of earth pressure on several representative retaining structures of soft or loose soils in Nanning-Kunming railway, theory model of a parabola distribution mapform was induced, amended and advanced. Accordingly, a simplicity map forms ofearth pressure distribution was put forward.6. By means of the analysis of "soil arching effect" between adjacent piles,taking geometrical characteristic of arch line and the fracturing face direction angleof Mohr-Coulomb failure to account, the force-balancing condition and strengthcondition are integrated. Based on Mohr-Coulomb failure criterion, the least handysoil strength parameters that only including cohesion c and internal friction angleφ,according to the relationship between the normal stress and arrow-span ratio, thearch line and spacing between piles are obtained. A concise estimate method to soilarch effect was put forward.7. Based on the practical engineering of Danba large-scale loose bed landslide,the mechanism of slide was analyzed. The effect of remediation works such asprestressed anchor cables and stabilizing piles with prestressed anchor cables wasdiscussed. A arrange method of engineering construction was put forward based onmechanism of slide and deformation characters.更多还原