水泥土中GFRP筋的界面黏结特性试验研究
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摘要
加筋水泥土桩锚支护技术广泛应用于边坡与基坑工程的加固,而常用的钢筋等金属材料筋体在富水及高腐蚀性的环境中往往会面临锈蚀的风险.玻璃纤维增强塑料筋(GFRP筋)因其抗拉强度高、抗腐蚀性强等特点将成为金属材料筋体的重要替代.为揭示GFRP筋-水泥土界面的黏结特性,通过12组不同配比下水泥土的无侧限抗压强度试验以及对应水泥土中GFRP筋的单元体中心拉拔试验,获得了GFRP筋-水泥土界面黏结滑移曲线,并进一步得到了界面黏结强度与水泥掺入比及土体含水量的相关关系.基于界面黏结滑移曲线的形态特征,对GFRP筋-水泥土界面的承载过程及机理进行了分析.研究结果表明:GFRP筋-水泥土界面黏结强度随土体含水量的增大而降低,随水泥掺入比的增大而升高;GFRP筋-水泥土界面极限黏结强度与筋体周围水泥土的无侧限抗压强度呈明显的线性关系;界面黏结滑移曲线可分为弹性段、软化段、残余上升段、残余下降段4个阶段,各阶段分界点对应的界面黏结强度与界面极限黏结强度间存在不同的比例关系,可引入强度折减系数进行刻画.本文研究揭示了GFRP筋在水泥土中的黏结强度发挥机理,建立了基于水泥土配比的界面黏结强度预测模型,为GFRP筋加筋水泥土技术的工程应用提供了理论依据.
Reinforced cemented soil piled or anchored structures are extensively used in slope stabilization and excavation support. However, the conventionally used metal reinforcement usually faces corrosion risk in the environment with rich water and corrosive substances. Owing to its characteristics such as high tensile strength and corrosion resistance, glass fiber reinforced polymer(GFRP) tendon tends to be a competitive alternative to metal reinforcement. To reveal the interface bond behavior of GFRP tendon embedded in cemented soils, 12 groups of tests, including uniaxial compression tests on cemented soil specimens and element pull-out tests on GFRP tendon reinforced cemented soil specimens, were conducted with varying cemented soil dosages. Moreover, the bond–slip curves for pull-out specimens, together with the correlation associating the interface bond strength with the cement and moisture contents, were obtained. On the basis of the characteristics of bond–slip curves, the bond mobilization process and mechanism of the interface between GFRP tendon and cemented soil were analyzed. Research results indicate that the interface bond strength decreased with the increase in moisture content but increased with the increase in cement content. The ultimate interface bond strength tended to be linearly correlated with the uniaxial compressive strength of cemented soil near the tendons. The bond–slip curve was characterized by four consecutive stages, i.e., elastic, strain-softening, residual-ascending, and residual-descending stages. The interface bond strengths corresponding to the demarcation points of various stages were correlated with the ultimate interface bond strength in different proportions, which can be characterized by reduction factors. The research in this paper uncovers the mobilizing mechanism of bond strength of GFRP tendons embedded in cemented soils and establishes a prediction model for the interface bond strength based on cemented soil dosage, providing theoretical reference for engineering applications of GFRP tendons reinforced cemented soil structures.
Reinforced cemented soil piled or anchored structures are extensively used in slope stabilization and excavation support. However, the conventionally used metal reinforcement usually faces corrosion risk in the environment with rich water and corrosive substances. Owing to its characteristics such as high tensile strength and corrosion resistance, glass fiber reinforced polymer(GFRP) tendon tends to be a competitive alternative to metal reinforcement. To reveal the interface bond behavior of GFRP tendon embedded in cemented soils, 12 groups of tests, including uniaxial compression tests on cemented soil specimens and element pull-out tests on GFRP tendon reinforced cemented soil specimens, were conducted with varying cemented soil dosages. Moreover, the bond–slip curves for pull-out specimens, together with the correlation associating the interface bond strength with the cement and moisture contents, were obtained. On the basis of the characteristics of bond–slip curves, the bond mobilization process and mechanism of the interface between GFRP tendon and cemented soil were analyzed. Research results indicate that the interface bond strength decreased with the increase in moisture content but increased with the increase in cement content. The ultimate interface bond strength tended to be linearly correlated with the uniaxial compressive strength of cemented soil near the tendons. The bond–slip curve was characterized by four consecutive stages, i.e., elastic, strain-softening, residual-ascending, and residual-descending stages. The interface bond strengths corresponding to the demarcation points of various stages were correlated with the ultimate interface bond strength in different proportions, which can be characterized by reduction factors. The research in this paper uncovers the mobilizing mechanism of bond strength of GFRP tendons embedded in cemented soils and establishes a prediction model for the interface bond strength based on cemented soil dosage, providing theoretical reference for engineering applications of GFRP tendons reinforced cemented soil structures.
引文
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[12]刘干斌,沈学毅,苏舟,等.搅拌水泥土锚杆抗拔变形试验改进研究[J].岩土力学,2011,32(S1):78-82.Liu Ganbin,Shen Xueyi,Su Zhou,et al.Improvement test of uplift resistance and deformation of cementsoil mixing anchor[J].Rock and Soil Mechanics,2011,32(S1):78-82(in Chinese).
[13]于宁,朱合华,梁仁旺.插钢筋水泥土力学性能的试验研究[J].土木工程学报,2004,37(11):78-84.Yu Ning,Zhu Hehua,Liang Renwang.Experimental study on mechanical properties of reinforced cementedsoil[J].China Civil Engineering Journal,2004,37(11):78-84(in Chinese).
[14]Horpibulsuk S,Miura N,Nagaraj T S.Assessment of strength development in cement-admixed high water content clay with Abrams’law as a basis[J].Géotechnique,2003,53(4):439-444.
[15]Chew S H,Kamruzzaman A H M,Lee F H.Physicochemical and engineering behavior of cement treated clays[J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(7):696-706.
[16]?hnberg H.Strength of Stabilized Soils-A Laboratory Study on Clays and Organic Soils Stabilized with Different Types of Binder[D].Sweden:Lund University,2006.
[17]陈昌富,梁冠亭,汤宇,等.锚杆锚固体与土体界面特性室内测试新方法[J].岩土工程学报,2015,37(6):1115-1122.Chen Changfu,Liang Guanting,Tang Yu,et al.Anchoring solid-soil interface behavior using a novel laboratory testing technique[J].Chinese Journal of Geotechical Engineering,2015,37(6):1115-1122(in Chinese).
[2]马郧,徐光黎.SMW+水泥土桩锚结构在基坑工程中的应用-以武汉长江Ⅰ级阶地基坑工程为例[J].地下空间与工程学报,2013,9(4):934-938,964.Ma Yun,Xu Guangli.Application of SMW and pile anchor retaining structure in a soft soil excavation pit[J].Chinese Journal of Underground Space and Engineering,2013,9(4):934-938,964(in Chinese).
[3]北京交通大学隧道与岩土工程研究所.加筋水泥土桩锚支护技术规程(CECS147)[S].北京:中国计划出版社,2016.Institute of Tunnel and Geotechnical Engineering,Beijing Jiaotong University.Technical Specification for Retaining and Protection with Reinforced Cement Soil Piles and Anchors(CECS147)[S].Beijing:China Planning Press,2016.
[4]高丹盈,朱海堂,谢晶晶.纤维增强塑料筋锚杆及其应用[J].岩石力学与工程学报,2004,23(13):2205-2210.Gao Danying,Zhu Haitang,Xie Jingjing.Applications of fiber reinforced plastic(FRP)bolts[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(13):2205-2210(in Chinese).
[5]薛伟辰.非金属锚杆界面黏结强度试验研究[J].岩土工程学报,2005,27(2):206-209.Xue Weichen.Experimental studies on interface bond strength of non-metallic anchors[J].Chinese Journal of Geotechnical Engineering,2005,27(2):206-209(in Chinese).
[6]罗小勇,唐谢兴,匡亚川,等.GFRP锚杆锚固黏结性能试验研究[J].铁道科学与工程学报,2015,12(3):521-527.Luo Xiaoyong,Tang Xiexing,Kuang Yachuan,et al.Test research on anchorage adhesive property of GFRPanchor bolt[J].Journal of Railway Science and Engineering,2015,12(3):521-527(in Chinese).
[7]郝庆多,王言磊,侯吉林,等.GFRP带肋筋黏结性能试验研究[J].工程力学,2008,25(10):158-165,179.Hao Qingduo,Wang Yanlei,Hou Jilin,et al.Experimental study on bond behavior of GFRP ribbed rebars[J].Engineering Mechanics,2008,25(10):158-165,179(in Chinese).
[8]高丹盈,朱海堂,谢晶晶.纤维增强塑料筋混凝土黏结滑移本构模型[J].工业建筑,2003,33(7):41-43,82.Gao Danying,Zhu Haitang,Xie Jingjing.The constitutive models for bond slip relation between FRP rebars and concrete[J].Industrial Construction,2003,33(7):41-43,82(in Chinese).
[9]Chen C,Zhang G,Zornberg J G,et al.Interface behavior of tensioned bars embedded in cement-soil mixtures[J].Construction and Building Materials,2018,186:840-853.
[10]刘全林,杨有莲.加筋水泥土斜锚桩基坑维护结构的稳定性分析及其应用[J].岩石力学与工程学报,2005,24(S2):5331-5336.Liu Quanlin,Yang Youlian.Stability analysis of inclined anchorage pile for reinforced cement-soil in bracing excavation structure and its application[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(S2):5331-5336(in Chinese).
[11]刘干斌,叶荣华,沈学毅,等.搅拌水泥土锚杆作用机理及基坑支护工程应用[J].岩土工程学报,2010,32(S2):363-366.Liu Ganbin,Ye Ronghua,Shen Xueyi,et al.Mechanism of cement-soil mixing anchor and application in foundation pit support project[J].Chinese Journal of Geotechical Engineering,2010,32(S2):363-366(in Chinese).
[12]刘干斌,沈学毅,苏舟,等.搅拌水泥土锚杆抗拔变形试验改进研究[J].岩土力学,2011,32(S1):78-82.Liu Ganbin,Shen Xueyi,Su Zhou,et al.Improvement test of uplift resistance and deformation of cementsoil mixing anchor[J].Rock and Soil Mechanics,2011,32(S1):78-82(in Chinese).
[13]于宁,朱合华,梁仁旺.插钢筋水泥土力学性能的试验研究[J].土木工程学报,2004,37(11):78-84.Yu Ning,Zhu Hehua,Liang Renwang.Experimental study on mechanical properties of reinforced cementedsoil[J].China Civil Engineering Journal,2004,37(11):78-84(in Chinese).
[14]Horpibulsuk S,Miura N,Nagaraj T S.Assessment of strength development in cement-admixed high water content clay with Abrams’law as a basis[J].Géotechnique,2003,53(4):439-444.
[15]Chew S H,Kamruzzaman A H M,Lee F H.Physicochemical and engineering behavior of cement treated clays[J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(7):696-706.
[16]?hnberg H.Strength of Stabilized Soils-A Laboratory Study on Clays and Organic Soils Stabilized with Different Types of Binder[D].Sweden:Lund University,2006.
[17]陈昌富,梁冠亭,汤宇,等.锚杆锚固体与土体界面特性室内测试新方法[J].岩土工程学报,2015,37(6):1115-1122.Chen Changfu,Liang Guanting,Tang Yu,et al.Anchoring solid-soil interface behavior using a novel laboratory testing technique[J].Chinese Journal of Geotechical Engineering,2015,37(6):1115-1122(in Chinese).