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1、【精品文档】如有侵权，请联系网站删除，仅供学习与交流混凝土框架梁.精品文档.预应力锚索框架梁在边坡工程中的应用孟飞，杨果林(中南大学土木建筑学院，湖南 长沙 410075)摘 要：对预应力锚索框架梁这一新型支挡结构进行简要介绍，描述了其在国内外边坡工程中的应用情况及主要构造形式，论述了相应的受力分析方法及加固后边坡安全系数的计算方法，分析了其优点及适用情况。结论表明：预应力锚索框架梁是一种适用范围广，加固深度大，工程造价低的新型支挡结构。关键词：预应力锚索框架梁；受力分析；安全系数The Framed Beams with Prestressed Cables Used in Slope En
2、gineeringMENG Fei, YANG Guo-lin(School of Civil Engineering and Architecture of Central South University, Changsha 410075, China)Abstract: A new type of supporting structure named the framed beams with prestressed cables was introduced in this paper. Its application in slope engineering at home and
3、abroad and the main construction styles are described. The stress analysis method and the safety factors of slopes using framed beams with prestressed cables are discussed. Then its advantages and applicable conditions are analyzed. The results show that the framed beams with prestressed cables is a
4、 new type of supporting structure has broad scope of application, large reinforcement depth and low construction cost.Keywords: framed beams with prestressed cables; stress analysis; safety factor1 引 言近年来，伴随着我国经济的发展，水利、矿山、铁路、公路、城市建设迅速开展，在工程建设中形成了大量的人工边坡。现有的边坡加固措施一般分为两种：第一种是减滑工程措施，包括在滑坡上方减重、滑坡下方加重和滑坡
5、后部做排水工程及增设防水护面等；第二种是抗滑支挡加固工程措施，如挡土墙、抗滑桩等。第一种减滑工程措施往往无法使问题得到根治，而第二种抗滑支挡加固措施虽稳定滑坡安全可靠，但也有工程量大、造价高等不可忽视的缺点14。近年来出现的预应力锚索框架梁复合结构，因其经济、绿色而广泛使用于水库边坡、高速公路和铁路的路堑及路基边坡防护中5, 6。预应力锚索框架梁技术是一种采用抗拉强度高的柔性材料锚固于稳定的岩土体内，充分利用和提高岩土自身强度和自稳能力来加固不稳定岩土体的工程措施。如图1所示，它由框架、锚索和墙后土体组成，属于轻型挡土结构7。锚索的外端与框架梁相连接，内端锚固在土体中，框架梁所受的土压力通过锚
6、头传至钢拉杆，再由拉杆周边砂浆握裹力传递至锚固区的稳定地层中，从而利用地层深处的锚固力维持边坡的稳定性。在预应力锚索框架梁支护结构中，锚索在一定的锚固区域内形成压应力带，通过框架挡墙及挡土板形成压力面，改善土体的力学性能，变传统支护结构的被动支护为充分利用土体本身自稳能力的主动支护，有效地控制了坡体的位移8, 9。图1 预应力锚索框架梁结构示意图Fig. 1 Schematic diagram of the structure of framed beams with prestressed cables2 预应力锚索框架梁的发展概述预应力锚索加固边坡时，若应用在完整的硬岩岩体上，通过面积较小
7、的锚墩即可将锚固力向被加固岩体内传递；当被加固的坡面较软弱破碎时，则必须加大锚墩的面积以满足锚墩下地基承载力要求10。随着预应力锚固护坡技术在软弱坡体加固中不断得到应用，与之相适应得结构形式也得到了相应的改进和发展。在上世纪90年代日本较早地应用了PC(Pretressing Concrete)框架锚固法和Q&S(Quick & Strong)框架工法11。上世纪90年代初我国逐渐开始应用现浇式的预应力锚索地梁和预应力锚索框架梁。2.1 PC框架锚固工法此工法是由预制预应力混凝土框架和灌浆锚索组成。它将传统的现浇多菱锥台式锚墩结构改为预制预应力混凝土构件。PC框架锚固工法有较为完善的设计施工规
8、范，实现了标准化及系列化，在日本的许多重要工程中得到了应用。工厂加工的预制预应力混凝土强度高，无裂缝，有良好的耐久性，不需在现场养护，可靠性高、施工速度快。预制构件结构尺寸较统一，外形美观，框格内可种植草本植物恢复生态，与环境相协调，符合环境保护要求。这是PC框架锚固工法的主要优点。2.2 Q&S框架工法该法将预先在工厂加工组装好的矩形钢筋笼框，按矩形或菱形铺置于边坡上，然后在钢筋笼上喷射混凝土。因在陡倾的斜面现场编制钢筋笼和浇筑混凝土相对困难，并且相当费时，在工厂批量生产出组装好箍筋的折叠型框架，运送到现场打开即可使用。因此，该工法具有现场施工性能、构造和强度上较显著的优越性。PC框架锚固工
9、法和Q&S框架锚固工法在我国一直没有得到推广，这主要是由于日本施工的自动化、机械化和工厂化水平高，而我国相对较低。且日本的交通运输发达，将工厂生产的成品运到施工现场非常方便，但是我国的交通不方便，特别是在山区进行的工程建设。另外我国山区面积较多，工程规模较大，边坡高度大，采用此工法造价高，这也不利于推广应用。2.3 现浇式预应力锚索框架梁结合我国工程技术发展水平及具体条件，从上世纪90年代开始，我国开始大量应用现浇式预应力锚索框架梁结构。1994年铁道科学研究院将这一结构应用于深圳市罗沙公路西岭山边坡的加固中，随后在深圳市罗芳山庄边坡治理、黄贝岭坡体滑坡、蛇口月亮湾别墅等边坡加固和滑坡治理中得
10、到了广泛应用12。随着我国交通建设的逐渐发展，边坡病害问题尤为突出，预应力锚索框架在边坡的治理中发挥了越来越重要的作用。2000年，铁道科学研究院将这一结构成功应用在高陡边坡的加固中13，如图2所示。京珠高速公路粤境南段K150左侧边坡总高度30余米，边坡岩土体大多为中强风化呈砂土状的泥岩夹粉砂岩，一级边坡局部还夹灰岩，原设计方案在一级平台设锚索抗滑桩，桩长20 m，悬臂10 m，桩自路基面以上7 m高度范围内铺浆砌片石挡墙，上部3 m高度范围内设挡土板。按原设计施工对边坡扰动较大，工期长，造价高。后将一级边坡加固形式改为多排预应力锚索框架结构，坡率为1：0.3，缩短了工期，降低了造价。图2
11、预应力锚索框架梁边坡加固效果图Fig. 2 Slopes reinforced with framed beams with prestressed cables3 预应力锚索框架梁结构受力分析现浇混凝土框架梁与预应力锚索复合结构属于一种主动抗滑结构。锚索的预应力作用同时通过框架梁传递到坡面上，坡体受压产生抗滑力，达到稳定滑坡的目的。现浇混凝土框架梁与预应力锚索复合结构不同于预应力锚索单独作用，现浇混凝土框架梁除了护坡作用外，还有比锚墩更大的接触面积，且整体刚度强。这就使得坡面受力均匀，基底压力减小，在地基承载力较小的滑坡治理工程中也可应用14。该方法适用于整体稳定性差、前沿坡面须防护的中小型
12、松散介质边坡治理，尤其是进一步削坡条件受限的边坡治理工程，广泛应用于铁路、公路、库区的松散堆积体滑坡治理。图3 预应力锚索框架梁复合结构受力简图Fig. 3 Force diagram of framed beams with prestressed cables现浇钢筋混凝土框架梁与预应力锚索复合结构受力简图如图3所示。以平面破坏边坡为例，不考虑地下水的影响，沿边坡走向取单位宽度，根据极限平衡原理，加锚固力后边坡的安全系数计算表达式为15, 16：式中：Fs为边坡的安全系数；c为滑动面的粘聚力；为滑动面摩擦角；W为滑块自重；L为滑动面长度；T为作用于滑体的锚固力，；为滑动面倾角；p为锚索与水
13、平面的夹角。可求得边坡稳定性安全系数达到许用值Fs时所需施加的锚固力为：根据锚索的水平间隔及锚索排数计算单根锚索的设计锚固力Td为：式中：m为锚索排数；d为锚索水平间隔。4 预应力锚索框架梁优点及适用范围4.1 预应力锚索框架梁加固边坡的优点(1) 预应力锚索框架梁可有效进行坡面防护和高边坡病害防治预应力锚索框架梁较好的将高边坡病害防治与坡面柔性防护有机地结合，既达到防治高边坡病害目的又能美化环境，实现了自然和工程和谐统一。通过给边坡体内稳定的岩体中锚固大吨位预应力锚索并施加的预应力，能抵抗边坡体深层破坏、变形。由于土拱效应，贴于坡面的钢筋混凝土框架对边坡体表层岩土起到框箍作用，限制了表层岩土
14、受破坏和变形。在框架内进行植被防护既能防治水流对坡面冲刷，又能预防坡面岩土风化剥落、形成落石等小型坡面变形，还可以达到美化自然环境的效果。(2) 合理的结构受力能够更直接有效地控制边坡病害的深层破坏支挡结构加固设计时往往针对边坡病害的深层破坏力来采取措施。如何抵抗此破坏力，重力式挡墙依靠的是墙体自重及其产生的基底摩阻力和墙前被动土压力；抗滑桩则依靠锚固段的桩周侧向抗力，或者是能提供上压力的桩侧土的被动土压力与主动上压力差来克服；而锚索框架依靠的是锚固于稳定岩和土体的高强度低松弛钢绞线来拉紧坡面的钢筋混凝土框架，利用它提供与边坡破坏力相反方向的抗力来克服破坏。锚索预应力还能够控制因人工开挖边坡形
15、成的松弛区发展，主动限制边坡变形并为其提供支挡作用力，如图4所示。因此，相比较而言锚索框架的工程效果更好，更经济。图4 预应力锚索框架梁深层加固效果图Fig. 4 The large reinforcement depth of framed beams with prestressed cables(3) 边坡岩土体受力状态的改善边坡病害的主要特征是坡体临空面破坏和变形。抗滑挡墙及抗滑桩结构，都是利用坡体变形（或变位）作用在结构上使其产生反力来抵抗边坡变形破坏力的，如果边坡体没有变形就不会对结构物产生反力。这一变形过程中边坡岩体会进一步松弛，原来岩体中各种软弱结构面会由密闭变为逐渐张开，容易
16、受到地表水和地下水的软化作用，因此在支挡结构施工结束后产生变形破坏的力还会增加。预应力锚索框架梁由于施加了预应力，可替代或部分替代因开挖坡体所失去的侧向支撑力，使边坡体处于或趋向于三向受压的状态，因而限制边坡扰动区的发展，提高坡体稳定性和边坡岩体的镶嵌作用，减缓或阻止了边坡病害条件的逐步恶化。(4) 边坡开挖量小可减少对自然的破坏自然山坡陡峻时采用高陡预应力锚索框架梁可减小边坡的开挖高度，不但能大幅减少对原始青山绿地的破坏，而且能减小或防止大面积开挖引起的各种边坡病害，预应力锚索框架梁更加适用于自然坡较陡地段的高堑坡加固。(5) 施工技术风险低、简便易行运用预应力锚索框架梁来加固高边坡或防治高
17、边坡病害，应遵循自上而下开挖一级加固一级的顺序施工，上一级锚索初张拉后再开挖和加固下一级边坡，对每一级边坡还可分层、分段施工。这样可大幅减小边坡施工对边坡体的扰动，避免了施工不当引起的边坡病害，这点也是重力式抗滑挡墙难以企及的。这种结构的主体受力构件为高强度低松弛的钢绞线，可节省材料，使结构轻便。由于可灵活运用分级、分层、分段开挖措施，同一边坡体上可展开几个施工工作面，从而缩短工期。4.2 预应力锚索框架梁加固方法的适用条件边坡病害整治工程在设计时需要进行场地的工程地质勘察，详细了解和分析病害发生的原因和条件，然后再有针对性地选用综合工程措施，才能取得期望的良好效果。预应力锚索虽然有以上优点，
18、但由于框架梁的护坡机理及预应力锚索的锚固机理，预应力锚索框架梁结构仍有一定的适用范围，实际应用过程中应注意以下原则：(1) 预应力锚索框架梁作为一种轻型支挡结构可适应一定规模的各种地层岩性的边坡病害整治工程的要求。它适用于高陡度土质、石质的不同规模边坡崩塌、滑坡、坍塌等人工及自然病害，还有各种表层、坡面病害的防护，但对错落型边坡病害并不适用。(2) 预应力锚索框架梁依靠高强度低松弛的钢绞线产生的拉力来克服坡体破坏力，因此场地工程地质条件能否提供稳定的锚固体，以及所能提供的锚固力大小，是判断该项工程是否适用需要考虑的要点之一。锚固段不应设置在淤泥质土、有机质土和液限WL50%的土层以及相对密度D
19、r0.3的土层中，对钢筋、水泥有腐蚀性特别是强腐蚀性的地层不应采用，一旦采用应进行严格的防腐处理。(3) 预应力锚索框架梁的间距与断面尺寸要适应坡体岩土的特性。钢筋混凝土框架梁对边坡岩土要起到框箍作用，必须使框架整体刚度与边坡岩体的刚度相匹配，还要考虑到基底的承载力。通常边坡岩体越坚硬、密实、完整则其刚度越大，抗变形能力就越强，框架的间距可以变大，钢筋混凝土梁的截面尺寸可减小。(4) 预应力锚索框架梁作为一种空间结构适合设置于多级挖方边坡上。框架竖肋底部适宜放置在较稳固的基岩、土层上，除去框架后竖肋埋深较大（据经验不小于4.0 m）的前平台宽度者，才可在设计中考虑框架埋入段的岩土抗滑作用；因为
20、预应力锚索作用限制了被动土压力的形成条件，所以无法按被动土压力考虑支挡结构所受荷载（建议按静止土压力设计），并且要考虑抗滑作用力。在下一级边坡的设计中必须按相反方向将上级边坡的土压力设计值加于支挡结构上。出现下列情况则不宜采用预应力锚索框架梁：边坡表层岩土松散、软弱、潮湿的土层；施工不能成形开挖或没有自稳能力的土层。5 研究展望目前，预应力锚索框架梁的理论研究仍存在许多问题，主要包括：预应力锚索框架梁的适用条件有待于深入的分析和研究；锚索受力研究还处在初期阶段，没有完全掌握锚固段上剪应力的分布特点；框架梁的受力模式和设计计算方法尚不完善、不成熟。几十年来，国内外大量的学者和工程技术人员从理论和
21、工程实践的角度对其进行了分析研究，但是到目前为止，还没有形成一套比较成熟完善的理论。目前预应力锚索框架梁的设计理论和施工技术在不断的发展和创新，主要的研究动态表现在以下几个方面：(1) 预应力锚索框架梁的数值模拟研究，主要是利用有限元、边界元等数值分析方法对预应力锚索框架梁进行空间与时间效应、应力场、结构与土协同工作等方面的分析与研究。(2) 预应力锚索框架梁与其它支护结构类型的复合支护技术的应用研究，主要表现在多种支护结构形式在边坡工程设计与施工中的联合应用。(3) 预应力锚索框架梁变形控制、预测及稳定性研究，主要借助计算机技术、人工智能、优化方法、位移反分析、非确定性数学等研究框架锚索的变
22、形、稳定性及安全性。参考文献(References)：1 李宁, 张平, 李国玉. 岩质边坡预应力锚固的设计原则与方法探讨J. 岩石力学与工程学报, 2004, 23(17): 2972-2976.2 孙宁波. 混凝土框架与框格梁锚固技术及其应用J. 中国地质灾害与防治学报, 1999, 10(4): 91-93.3 程少荣, 王冬珍. 格构锚固技术及其在滑坡整治中的应用J. 人民长江, 1997, 28(6): 26-27.4 胡凌云, 刘金兴, 张德军. 深圳老虎坳滑坡治理工程J.西部探矿工程, 1999, 11(3): 105-108.5 黄晓华. 公路边坡病害治理的轻型支挡结构J. 重
23、庆交通学院学报, 1999, 18(3): 90-94.6 Gendy A S. Effective modeling of beams with shear deformations on elastic foundationJ. Structural Engineering and Mechanics, 1999, 8(6): 607-622.7 胡时友. 框格护坡技术的新进展J. 西部探矿工程. 1997, 11(4): 111-114.8 刘杰. 安徽铜黄高速公路A匝道高边坡岩体变形问题及支护措施有效性分析D. 成都: 成都理工大学, 2006.9 周陶. 滑坡治理中现浇钢筋砼格构梁与
24、预应力锚索复合结构研究D. 北京: 中国地质大学(北京), 2006.10 张永防, 王秉勇. 用锚杆框架护坡加固南昆线膨胀土边坡的研究J. 铁道工程学报, 2000, (3): 92-95.11 王恭先. 滑坡防治工程措施的国内外现状J. 中国地质灾害与防治学报, 1998, 9(1): 1-9.12 殷跃平. 中国滑坡防治工程理论与实践J. 水文地质工程地质, 1998, (1): 5-9.13 李海光. 新型支挡结构设计与工程实例M. 北京: 人民交通出版社, 2004.14 杨明. 路堑土质边坡加固中预应力锚索框架的内力计算J. 岩石力学与工程学报, 2002, 21(9): 1383
25、-1386.15 许英姿, 唐辉明. 滑坡治理中格构锚固结构的解析解分析J. 地质科技情报, 2002, 21(3): 89-93.16 Arai K., Tagyo K. Determination of noncircular slope giving the minimum factor of safety In slope stability analysisJ. Soils and Foundations, 1997, 25(1): 43-51.（英文版 ） easily blame, to prevent the broken window effect. Supervise th
26、e leading cadres to play an exemplary role, take the lead in the strict implementation of the and , lead to safeguard the solemnity and authority of the party discipline, ensure that the party discipline and the laws and regulations for implementation in place. Throughout the discipline in the daily
27、 supervision and management, strengthen supervision and inspection, from the thorough investigation of violations of discipline behavior. Strengthen to key areas, key departments and key projects as well as the masses reflect the concentration of the units and departments for supervision. - strength
28、ening supervision, discipline inspection and supervision of cadres to set an example for compliance with the and is a man must be hexyl, blacksmith needs its own hardware. Discipline inspection organs as the executor of the party discipline, and supervisor of the defenders, for its supervision must
29、be more strictly, discipline inspection and supervision of cadres to firmly establish the awareness of Party Constitution, sense of discipline and rules consciousness, politics loyalty, sense obey. Action speak Ji Ordinance to set an example of the regulations of the rule of law, strengthen supervis
30、ion and accept the supervision of the firmness and consciousness, do comply with and . To firmly establish the discipline must first be disciplined, the supervisor will be subject to the supervision of concept, and consciously safeguard and implement party compasses party, take the lead in practicin
31、g three strict real strict, so loyal, clean, play. To be good at learning, the Constitution and the as morality, politics and brought to fruition; to implement , do not want to, dare not, not with disciplinary ruler to supervision; to discipline a ruler, often the control inspection, and consciously
32、 in the ideological red line to draw the row Ming Good accumulation is indeed the bottom line, so that the heart has fear, said to have quit, the line has ended. Attached: indifferent to heart, calmly to the table in our life, there are many unpredictable things will happen, some good, some bad thin
33、gs, we cannot control is powerless to stop, but with time, you will find in life sometimes turns out to be not good, some bad things finally turned out to be a good thing, but then we muddy however did not know, this is the life teach us things. 1, life can be complex, can also be simple. Want simpl
34、e life of precipitation, to have enough time to reflect, to make Become more perfect. Life is the most important thing is not to win, but the struggle; not to have conquered, but to have fought well. 2, the plain is the background of life. Live a plain life, give up on themselves is not a coward, bu
35、t the wise answers; not disillusioned after the heart, such as ashes, but experience the storm after the enlightenment; not unrewarding perfunctorily, but calm attitude of life of unrestrained self-confidence. Plain living, there is no noise noisy, no earthly troubles, more did not fill in the disco
36、ntent of desire, some just a calm, a calm. 3, memory of heart will not good things to erase the, life is a When no movie, pain is a beginning, the struggle is a kind of process, death is a kind of ending. Give up this giving up is the helpless, do not give up the abandoned, do not give up this givin
37、g up is ignorance, do not give up should not give up is persistent. 4, a thing figured is heaven, think impassability is hell. Since the living, to live better. Sometimes we because of too narrow-minded, too care around the chores and penny wise and pound foolish, not worth the candle. Some things t
38、o attract trouble and worry, completely depends on how we look at and deal with it. Dont always take everything back to things, and dont get into a blind alley, dont want to face, dont be narrow-minded. Poke to care, is a kind of open-minded, a free and easy. 5, I am not afraid of others behind me a
39、 knife, I afraid to look back and see stab me, is my intention to treat people; I am not afraid of the truth to tell the best friend, Im afraid he turned to it as a joke to tell dont 6, when we are in a positive frame of mind, you will find many good things; and when we are in a negative state of mi
40、nd, you will find many depressed things; life happy and worry, all is you of life attitude, optimistic, good luck; loss of sink, Eritrea company. When you are in adversity, may wish to change a point of view to think everything over to the good Think, because good mentality decided the fate of the!
41、7, people are tired, rest; heart tired, calm. Grow up, mature, this society read. Tired and sad, squat down, to their a hug. Because the world no one can sympathize with you, have mercy on you. You cry, tears is your own; you pain, no one can understand. Then you only tears to smile. 8, each people
42、have youth,Each youth are a story, the life of the world never gets easier, I want what, wish the world all know, as has been the same; now want anything, for fear that others know, or like to lose the same. 9, the heart move, everything in the world is followed by birth, Rangrang, important thing i
43、s often the most difficult to open ones mouth, because words will reduce its importance; to let strangers people care about your life in the good things, the original is not easy 10, do not blame, do not laugh at who, also dont envy who. Like a person is a kind of feeling, not like a person is true.
44、 The truth is easy to explain, I feel Is unspeakable. The best travel life is that you in a strange place found a long lost touched. 11, happy life not in the bustling in, and in the peace of mind; no matter how many grievances, how uncomfortable, and ultimately to heal themselves or their own, othe
45、rs may got you to comfort, but never know your heart is how wanjianchuanxin. 12, maam, like a movie, learn to appreciate, learn to be grateful, learn tolerance, and goodness, helping others. Instead of accusing the society, as into one; and an exception is better to give than to what 13, dont envy h
46、im A sum of, dont lose your life and the life, respectively is: the former is a we experienced cannot escape in a day finally will last minute, while the latter is our persistent, we want to cherish the memory of those people and things. 14, learn to smile, learn to strong, the world you know so man
47、y people, so many people and you are, you cannot change also cant let everyone like you, so also do not want to do. Life is too short to go crazy to love to go to waste, to chase the dream to regret. 15, when temper, a blessing to go. A wounding elegant people, the key is to control their own emotio
48、ns. With the mouth is the most stupid behavior. A control negative emotions than a can take a city more powerful water flow slow, language is expensive. People spent two years of time to learn to speak, but to spend a few years time to shut up. That is a kind of ability, that is a kind of wisdom. 16, life is not perfect, sometimes, growth is not a cry, not an eyeful of tears, there is no trace of emotion, there is no gleam of hope, no desire, no action, no static, there is only one kind of downward sinking feeling, sink A murky? 6? 7? 6? 7 sink?