【作者】 汪海滨；

【导师】 高波；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2006， 博士

【摘要】 带预应力岩锚的隧道式复合锚碇作为悬索桥锚固系统的一种新的结构型式,具有重力式、隧道式锚碇所不具备的优点,其结构受力更合理,安全性更可靠,工程造价低,保护生态环境,实现可持续发展,拓宽了隧道式锚碇的应用范围和工程条件,提高了悬索桥的竞争力,填补了岩土工程领域中真正意义上充分利用自然宿主介质的强大的自承性的空白,具有较广阔的工程应用前景,经济效益巨大。 受地质条件限制,隧道式锚碇目前还局限应用在节理较少、围岩整体性能完好的地质环境。在节理裂隙发育或破碎岩层的工程边界进行悬索桥带预应力岩锚的隧道式复合锚碇工程的设计和施工,其难度和风险极大,国内外的研究基本处于空白。同时,作为系统承载主体之一的预应力岩锚,仅仅作为体系的安全储备考虑是不完善的。设计、施工均以经验类比法为主,没有相关理论作指导,与蓬勃发展的工程实践是极不相称的。 锚碇优化设计能产生巨大的经济效益,改善系统的受力,保证工程的安全可靠性和耐久性。一方面,在确定的荷载条件下,满足静力平衡、变形协调、本构关系以及边界条件时,拓扑参数变化和后部锚索初设预应力变化等对系统稳定性的影响,从而指导和修正设计;另一方面,数值方法虽然能综合考虑岩土材料的不连续性、各向异性、非线性的本构关系以及结构在破坏时呈现的体胀、软化、大变形特性等问题,但却不能为大多数设计者所采用。工程实践中,有时并不要求知道结构物中应力和应变随着外荷载如何变化,而只需求出最终达到塑性流动状态所对应的极限荷载或者结构物的安全系数。寻找能基本反映工程条件的简化计算公式,为工程师们提供一个整体的设计思路和方法。 研究中,通过文献综述和科技查新,论证课题的现状和方向;综合采用理论分析、数值模拟、工艺研究、实验验证(现场模型试验和原位试验)的技术路线。主要内容和成果如下: 1.分析锚固长度,自由长度,注浆性质以及锚注体与围岩接触方式对岩锚极限抗拔力和破坏形态的影响。阐释了锚索的根状效应和围岩应力场分布形态,提出安全储备系数概念。自由长度对围岩有效传递和分散围岩应力有关键作用,和锚固长度共同控制岩锚的破坏形态;在锚碇系统中,和初始预更多还原

【Abstract】 As a kind of new stnicture form of anchorage system of suspension bridge, tunnel anchorage compound with prestressed anchorage cable possess inavailability advantage of tunnel anchorage: reasonable structure stress distribution, reliable safety, low construction, ecological condition conservancy, realizing sustainable development, enlarging field of application and engineering condition of tunnel anchorage, increasing competitive power of suspension bridge, filling up the blank that made the most of nature host dielectric powerful self-supporting in deed meaning, foreground engineering practice and great economic benefit.Limited by geologic conditions, application of tunnel anchorage was localized in geologic environment of intact rock with less joint at presen. It was difficult and worst risk that tunnel anchorage compound with prestressed anchorage cable was designed and constructed in engineering boundary condition with abundant joint fissure or break ground, the research was blank both domestic and abroad. At the same time, as one of the system bearing main body, it was not perfect only considering the prestressed anchor cable as safety margin of system.. It was incommensurate with the engineering practice that design and construction gave priority to empirical analogism method because of no related theory guide.Anchorage optimum design can generate enormous eonomic benefits, improve system stress, ensure engineering safety reliability and endurance. On the one hand, under definitive condition of load, satisfy static equilibrium, compatibility of deformation, constitutive law as well as boundary condition, system stability affected by topological parameter and initial stress of back anchorage cable change, thereby supervise and modify design;On the other hand, numerical method can’t be adopt by majority designer although it can comprehensively consider discontinuity, anisotropy, nonlinear constitutive law and characteristic cubic of expansion, soften, large deformation, etc. of rock and soil matter, while structure was destroyed. Sometimes in engineering practice, how stress and strain of structure change with external load didn’t be demand, only ultimately critical load or structure safety factor corresponding to plastic flow state need to be find out, itprovides a simplified calculation and an overall design thought for engineers that look for a simplified calculation formulae reflect basic engineering condition.Research state and prospect were argumented by literature overview and science and technology originality innovation approval;Theoretical analysis, numerical simulation, processing study, experimental verification (field model test and in-shu test) were synthetical adopt in research methodology. Primary coverage and achievements as follows:1. The ultimate anti-pulling capacity and failure mode affected by anchor-length, free-length, grouting quality and interface mode between grout-cable and rock mass were analyzed. Stress distribution modality in rock mass and root effect was illustrated The concept of safety storage coefficient was put forwardFree-length has key effect to effectively transfer and disperse stress to wall rock;The failure mode of anchor cable is controlled by free and anchor length;Contribution value and occasion of anchor cable is determined by its free-length and initial stress while they share the load together with anchorage system. Strands stubble or grout-cable- pour slippage were mostly two kind of single anchor cable destroy model, integral reversed cone failure of rock mass wont occur. Failure of anchorage cable was progressive: bearing capacity won’t loss at once following destroy occuring before, higher peak instead under a certainty condition of loading until limiting destructive system. Domino offect occurs while the prestressed anchor cable group is destroyed2. Inclination, length, clamping angle of anchorage, interface roughness concentration and bonding capacity of interface ,etc. affect the displacement of anchorage and repose stability of rock mass. It indicates by multiplex load contrastive analysis, that anti-pulling capacity increase depend on effective projected area (axial direction projection component along main cable) of anchorage-wall rock interface increasing, gravity anchorage resist three-dimensional load depend on base friction, mat anti-slippage capacity increase mostly depend on anchorage volume gain;compound tunnel anchorage transfer and leveling foci stress, confine displacement by dip-holdup effect of tunnel anchorage and counterforce of prestressed anchor cable, spread systemic bearing depth and sphere. inclination of anchorage should be controlled in the field;Axial length L presence critical value, clamping angle of anchorage dominated displacement, and length influenced and "disturb " stress distribution on interface. The application of compound tunnelanchorage should be restricted at certain range and geologic conditioa3. Clip-holdup effect of rock mass and anti-pulling effect of anchorage cable system were self-balanceable, while they participate withstanding the load applied on tunnel anchorage system. Intial stress value of anchorage cable determined resource(carrying capacity that can be manoeuvred from rock mass) distribution: oversize initial stress generates unprofitable distortion and secondary stress in rock mass;undersize initial stress only generates reinforced effect and it was of no service to system stress redistributioa Initial stress of anchor cable ought to be controlled at the range of [(0.75~0.85)x0.75^k], thereby, value and occasion contributed by anchor cable will correspond with anchorage. If anchorage occur axial displacement corresponding with external load acting direction, the negative direction displacement and distortion of the anchorage must be overcame result in rock anchor stretching phase first of all.While initial stress was less, the anchorage cable stress enhanced only after rock mass clip-holdup being overcame.4. Based on field test results for compound tunnel anchorage system of suspension bridge, the failure model and failure condition are analyzed. The equilibrium equation of the anchorage system is established based on limit theorem. According to the actual construction technology and design scheme, the anchorage-rock mass interface is generalized into four types of mechanics model, and the failure criterion is correspondingly presented based on rock mass joint mechanics theorem and test achievements. The meaning and option method of subentry coefficient in simplified formula for bearing capacity estimation are discussed. The simplified formula for calculation of bearing capacity of anchorage was validated by practical engineering case. The proposed method provides a simplified calculation and an overall design thought for engineers.It’s key core which leads theory harvest in a position to engineering practice by marriaging rock mechanics and engineering, both serving and supervising construction practice, and looking forward to provide rationale and guide for optimum design and construction of compound tunnel anchorage used in mutable landform and geology environment <.更多还原