高寒盐沼泽区干湿-冻融循环下桥梁桩基腐蚀损伤与承载特性  

Corrosion damage and bearing characteristics of bridge pile foundations under dry-wet-freeze-thaw cycles in alpine salt marsh areas

作　　者：冯忠居[1] 霍建维 胡海波[2] 李铁 姚贤华 徐占慧 王富春[1] 刘宁 FENG Zhong-ju;HUO Jian-wei;HU Hai-bo;LI Tie;YAO Xian-hua;XU Zhan-hui;WANG Fu-chun;LIU Ning(School of Highway,Chang'an University,Xi'an 710064,Shaanxi,China;Research Center of Coastal and Urban Geotechnical Engineering,Zhejiang University,Hangzhou 310058,Zhejiang,China;School of Civil Engineering and Communication,North China University of Water Resources and Electric Power,Zhengzhou 450011,Hen'an,China;Highway Survey and Design Institute of Qinghai Province,Xining 810008,Qinghai,China)

机构地区：[1]长安大学公路学院,陕西西安710064 [2]浙江大学滨海和城市岩土工程研究中心,浙江杭州310058 [3]华北水利水电大学土木与交通学院,河南郑州450011 [4]青海省公路科研勘测设计院,青海西宁810008

出　　处：《交通运输工程学报》2020年第6期135-147,共13页Journal of Traffic and Transportation Engineering

基　　金：国家自然科学基金项目(51708040);青海省交通科技攻关项目(2014-07);海南省交通科技项目(HNZXY2015-045R)。

摘　　要：为探明青海地区桥梁桩基在干湿-冻融循环条件下的腐蚀损伤特性,依托德香高速公路工程,在现场埋设钢筋和混凝土试件进行干湿-冻融循环1年,采用室内试验将混凝土试件进行干湿-冻融循环225次,对比分析了不同位置和不同循环时间条件下混凝土质量、抗侵蚀系数、相对动弹性模量、抗压强度、微观机理以及钢筋锈蚀率的变化规律;采用数值仿真分析了未防护桩基20年内承载力变化规律,并提出了高寒盐沼泽区桥梁桩基防护措施。研究结果表明:随着试件埋设深度的增加,现场桩基混凝土试件的抗侵蚀系数相关度增大,最大值为0.93;随着时间的增加,桩基混凝土试件的抗压强度最大损失率为38.20%,埋深0.25 m处钢筋的面积锈蚀率最大,为91%;表面涂抹环氧树脂可以有效减少钢筋锈蚀率,桩基混凝土试件与钢筋的质量变化不明显;干湿-冻融循环225次时,桩基混凝土试件的边角处出现脱落,四周出现裂纹,但质量变化较小,相对动弹性模量降低了39.10%,抗侵蚀系数降低到0.51,混凝土的抗压强度损失率为65.88%,其内部因出现Friedel盐等膨胀性物质而趋于破坏;随着剥落厚度和腐蚀深度的增加,前8年桩基的承载力基本不变,8年后其承载力逐步降低,若不进行维护,第20年桩基承载力降低34.45%;建议在桩基服役8年后,要进行重点防护。To explore the corrosion damage characteristics of bridge pile foundation in Qinghai area under dry-wet-freeze-thaw cycles, relying on the Dexiang Expressway Project, the reinforcement and concrete specimens were embedded in the field to subjected to freeze-thaw cycles for one year. The laboratory test was used to conduct the dry-wet-freeze-thaw cycles on concrete specimens for 225 times. The variation rules of concrete mass, anti-erosion coefficient, relative dynamic elastic modulus, compressive strength, micro-mechanism and reinforcement corrosion rate at different positions and different cycle times were compared and analyzed. The numerical simulation was conducted to analyze the bearing capacity change rule of unprotected pile foundation over 20 years, and protection measurements for bridge pile foundations in alpine salt marsh areas were proposed. Research result shows that as the embedment depth increases, the correlation degree of anti-erosion coefficient of pile foundation concrete specimens in the field increases, and the maximum value is 0.93. As time increases, the maximum compressive strength loss rate of pile foundation concrete specimens is 38.20%. The areal corrosion rate of reinforcement at the depth of 0.25 m is the largest, and the value is 91%. Coating epoxy resin on the surface can effectively reduce the corrosion rate of reinforcement, The mass changes of pile foundation concrete specimen and reinforcement are not obvious. In the 225 th dry-wet-freeze-thaw cycles, the corner of pile foundation concrete specimen falls off and cracks appear around, but the mass change is small. The relative dynamic elastic modulus reduces by 39.10%, the anti-erosion coefficient reduces to 0.51, the compressive strength loss rate of concrete is 65.88%. Failare nearly occurs in the interior because of the presence of Friedel salt and other expansive substances. As the spalling thickness and corrosion depth increase, the bearing capacity of pile foundation in the first eight years remains essentially unchanged. Af

关 键 词：桥梁工程 桩基 现场试验 室内试验 数值仿真 干湿-冻融循环 腐蚀损伤 承载特性 

分 类 号：U443.15[建筑科学—桥梁与隧道工程]