微型桩预应力锚杆复合土钉作用机制研究
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摘要
随着我国城市化进程的加快,高层、超高层建筑越来越多,基坑开挖深度也越来越深,与此同时我国城市用地日趋紧张,建筑基坑周围环境越来越复杂,使用单一的土钉支护形式已经不能满足基坑变形的要求。因此,设计人员开发了一种在土钉墙的基础上多种支护形式复合使用的支护形式,这类复合土钉支护形式现已成为我国基坑支护的主要发展方向。
将微型桩与锚杆-土钉复合支护结构相结合,弥补了一般锚杆与土钉复合支护结构的许多缺陷和使用上的限制,在深基坑工程中逐步得到了应用。本文首先通过对微型桩预应力锚杆复合土钉支护结构实测数据进行分析,得出了锚杆和土钉在结构中的作用以及它们相互的影响；其次利用FLAC3D软件分别对设置有微型桩和没有微型桩的锚杆复合土钉支护结构进行三维模拟,计算得出两种支护结构在不同开挖工况下土钉和锚杆的轴力变化以及基坑变形特征,最后对微型桩预应力锚杆复合土钉支护进行变参数模拟分析。本文所取得的主要成果包括：
(1)通过对现场实测数据的分析,总结土钉和锚杆在支护结构中的作用及其相互影响。
(2)通过数值模拟方法对比分析两种支护结构的受力和基坑变形规律,得出微型桩支护结构对基坑变形有较强的约束能力,并能明显改善土钉和锚杆的受力状态。
(3)锚杆有效约束锚固层附近土体的位移,从而达到分担土钉受力的作用。通过模拟分析可知,设有锚杆的基坑中,土钉可能在锚杆张拉初期有轴力降低的现象,但是随着基坑的开挖,土体中应力扩散和重分布,最终土钉将主要受到拉力作用。
(4)微型桩间距和桩径的变化对支护结构中土钉和锚杆的受力有明显的影响；土钉长度的变化对土钉自身以及锚杆受力有明显影响,但是对微型桩弯矩影响不大；锚固长度变化对支护结构受力几乎没有影响。
With the accelerated process of urbanization in china, high-level and super-high-rise building is continue to increase, the corresponding excavation depths are deeper and deeper, but at the same time, China's urban land is decreasing, the pit surrounding environment has become increasingly complex, a single soil nailing support form can not meet the requirements of the foundation pit deformation. Therefore, designers have developed a structural form on the basis of soil nail wall, the supporting structure composed by different single support. Such supporting structure has now become the main development direction of China's foundation pit.
The Micro-piles, Anchor and soil nailing compound supporting structure combined to make up for the lots of defect of the ordinary anchor and soil nailing compound supporting structure along with the restrictions on use, so it gradually being applied to deep foundation pit engineering. First, this thesis is base on a foundation pit engineering project in Zhengzhou zone, monitoring the axial force of soil nail and anchor by distributed optical fiber sensor, according to measured date, the role of the change of axial force is discussed. The computation models for micro-pile, pre-stressed anchor plus soil nail supporting system are established using FLAC3D, and a construction process simulation of foundation excavating and support is conducted. Through comparative analysis of two models, the role of the micro-pile in the compound support structure can be drawn. Finally, Micro-piles, Anchor and soil nailing compound supporting structure are analyzed through variable parameter simulation. In this paper the main achievements gained include:
(1) Summary of the soil nail and anchor in the supporting structure and their interaction through the analysis of measured data.
(2) To use numerical simulation methods, comparative and analysis the force and the pit deformation law of two kinds of supporting structure, then we can make a conclusion that mini piles supporting structure has strong ability for constraint deformation, and it also can improve the soil nail and the stress of anchor.
(3) Anchor effective constraint the displacement of the soil near the anchor layer, then it play the role of sharing stress on soil nailing, we know it through the simulation analysis that soil nailing may be has the phenomenon of axial force decrease in the early tension of anchor, however with the excavation of the foundation pit, soil mass stress will diffuse and distribute afresh, finally soil nail will mainly affected by the pull force.
(4) Miniature pile spacing and the variation of pile diameter significant impact on the soil nail in the supporting structure and the anchor's stress; The variation of soil nail length has obvious influence on soil nail itself and anchor's stress, but failed to mini piles bending moment. The variation of anchor length almost no influence on the stress of supporting structure.
将微型桩与锚杆-土钉复合支护结构相结合,弥补了一般锚杆与土钉复合支护结构的许多缺陷和使用上的限制,在深基坑工程中逐步得到了应用。本文首先通过对微型桩预应力锚杆复合土钉支护结构实测数据进行分析,得出了锚杆和土钉在结构中的作用以及它们相互的影响；其次利用FLAC3D软件分别对设置有微型桩和没有微型桩的锚杆复合土钉支护结构进行三维模拟,计算得出两种支护结构在不同开挖工况下土钉和锚杆的轴力变化以及基坑变形特征,最后对微型桩预应力锚杆复合土钉支护进行变参数模拟分析。本文所取得的主要成果包括：
(1)通过对现场实测数据的分析,总结土钉和锚杆在支护结构中的作用及其相互影响。
(2)通过数值模拟方法对比分析两种支护结构的受力和基坑变形规律,得出微型桩支护结构对基坑变形有较强的约束能力,并能明显改善土钉和锚杆的受力状态。
(3)锚杆有效约束锚固层附近土体的位移,从而达到分担土钉受力的作用。通过模拟分析可知,设有锚杆的基坑中,土钉可能在锚杆张拉初期有轴力降低的现象,但是随着基坑的开挖,土体中应力扩散和重分布,最终土钉将主要受到拉力作用。
(4)微型桩间距和桩径的变化对支护结构中土钉和锚杆的受力有明显的影响；土钉长度的变化对土钉自身以及锚杆受力有明显影响,但是对微型桩弯矩影响不大；锚固长度变化对支护结构受力几乎没有影响。
With the accelerated process of urbanization in china, high-level and super-high-rise building is continue to increase, the corresponding excavation depths are deeper and deeper, but at the same time, China's urban land is decreasing, the pit surrounding environment has become increasingly complex, a single soil nailing support form can not meet the requirements of the foundation pit deformation. Therefore, designers have developed a structural form on the basis of soil nail wall, the supporting structure composed by different single support. Such supporting structure has now become the main development direction of China's foundation pit.
The Micro-piles, Anchor and soil nailing compound supporting structure combined to make up for the lots of defect of the ordinary anchor and soil nailing compound supporting structure along with the restrictions on use, so it gradually being applied to deep foundation pit engineering. First, this thesis is base on a foundation pit engineering project in Zhengzhou zone, monitoring the axial force of soil nail and anchor by distributed optical fiber sensor, according to measured date, the role of the change of axial force is discussed. The computation models for micro-pile, pre-stressed anchor plus soil nail supporting system are established using FLAC3D, and a construction process simulation of foundation excavating and support is conducted. Through comparative analysis of two models, the role of the micro-pile in the compound support structure can be drawn. Finally, Micro-piles, Anchor and soil nailing compound supporting structure are analyzed through variable parameter simulation. In this paper the main achievements gained include:
(1) Summary of the soil nail and anchor in the supporting structure and their interaction through the analysis of measured data.
(2) To use numerical simulation methods, comparative and analysis the force and the pit deformation law of two kinds of supporting structure, then we can make a conclusion that mini piles supporting structure has strong ability for constraint deformation, and it also can improve the soil nail and the stress of anchor.
(3) Anchor effective constraint the displacement of the soil near the anchor layer, then it play the role of sharing stress on soil nailing, we know it through the simulation analysis that soil nailing may be has the phenomenon of axial force decrease in the early tension of anchor, however with the excavation of the foundation pit, soil mass stress will diffuse and distribute afresh, finally soil nail will mainly affected by the pull force.
(4) Miniature pile spacing and the variation of pile diameter significant impact on the soil nail in the supporting structure and the anchor's stress; The variation of soil nail length has obvious influence on soil nail itself and anchor's stress, but failed to mini piles bending moment. The variation of anchor length almost no influence on the stress of supporting structure.
引文
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[2]闫莫明,徐祯祥,苏自约.岩土锚固技术的新发展[C].见：中国岩土锚固工程协会,第九次全国岩土锚固学术研究会议论文集,北京：人民交通出版社,2000.10
[3]闫莫明,徐祯祥,苏自约.岩土锚固技术手册[M].北京：人民交通出版社,2004
[4]中华人民共和国建设部.JGJ120-99.建筑基坑支护技术规程.[S].北京：中国建筑工业出版社,1999
[5]陈肇元,崔京浩.土钉支护在基坑工程中的应用[M].北京：中国建筑工业出版社,2000.
[6]高大钊,陈忠汉,程丽萍.深基坑工程[M].北京：机械工业出版社,1999
[7]Schlosser, F. Soil Nailing in France-Research and Practice, Transportation Research Record 1330, Transportation Research board, Washington, D.C.,1992
[8]R, J. Bridle. Soil Nailing-Analysis and Design, Ground Engineering, SeP.1989
[9]D.A. Baker, Soil Nailing in Weathered Keuper Marl-A Case Study, Ground Engineering, Jan. /Feb.1994
[10]Schlosser, F. Behvaior and Design of Soil Nailing, Proc. of Symposium on Recent Developments in Ground Improvement Techniques, Bangkok, No.29,1982
[11]Kim, J. S., Kim, J., Y,& Lee, s. r. Analysis of soil-Nailed Earth Slope by Discrete Element Method. Computers and Geotechnics,1997,20(1)
[12]Mauricio Ehrlichh, Marcio, S. S. Almeida Parametric numerical analyses of soil nailing system. In:Ochiai, Yasufuku&Ojniine, eds. Earth Reinforcement. Balk- eman, Rotterdam, 1996
[13]黄运飞.土钉墙技术发展中的几个问题[J].建筑技术(z),1998
[14]Juran, I.&Elias, V. Ground Anchors and Soil Nails in Retaining Structures[M]. Foundation Engineering Handbook, Chapter 26, Fang.H.Y.(Ed), Van Nostrad Beinhold Pub,1991: 868-906
[15]陈叶青.(复合)土钉支护作用原理及稳定性分析研究(博士后研究工作报告).清华大学土木系,北京,2000：6-7
[16]李象范,徐水根.复合型土钉挡墙的研究[J].上海地质.1999,3：1-11
[17]李象范,何之民,徐水根.流砂地层中复合土钉墙的受力及变形性状[J].上海地质.1999,3：16-27
[18]李象范.上海地区基坑工程中的复合土钉支护技术[J].建筑施工.2001,6：363-369
[19]杨志银,张俊,王凯旭.复合土钉墙技术的研究及应用[J].岩土工程学报,2005,27(2)：153-156.
[20]杨志银,蔡巧灵,陈伟华等.复合土钉墙模式研究及土钉应力的监测试验[J].建筑施工.2001,6：427-43
[21]郭院成,秦会来,黄广华等.复合土钉支护工程施工过程中的土压力分析[J].河南科学,2004,22(6)：812-814
[22]郭院成,秦会来,刘战.工作状态下土钉受力变形计算模型的建立[J].河南科学,2005,23(6)：832-834
[23]秦会来,郭院成.水泥土桩复合土钉水平位移简化计算[J].岩土力学,2007,28(9)：1923-1926
[24]郭院成,童怀峰,秦会来.受限的桩锚与土钉联合支护结构的计算模式[J].郑州大学学报(工学版),2004,25(3)：52-55
[25]郭院成,杨庆,黄光华等.桩锚与土钉联合支护结构的优化选型[J].河南科学,2004,22(3)：35-38
[26]郭院成,秦会来,王立明.桩锚与土钉联合支护就够中的土压力分配模式[J].郑州大学学报(工学版),2004,25(3)：52-55
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