关键词： dynamic resilient modulus   freeze–thaw cycles   dynamic load   dynamic triaxial test   prediction model  

摘要： Although the dynamic properties of subgrade soils in seasonally frozen areas have already been studied, few researchers have considered the influence of shallow groundwater during the freeze–thaw(F–T) cycles. So a multifunctional F–T cycle system was developed to imitate the groundwater recharge in the subgrade during the freezing process and a large number of dynamic triaxial experiments were conducted after the F–T cycles. Some significant factors including the F–T cycle number, compaction degree, confining pressure, cyclic deviator stress, loading frequency, and water content were investigated for the resilient modulus of soils. The experimental results indicated that the dynamic resilient modulus of the subgrade was negatively correlated with the cyclic deviator stress, F–T cycle number, and initial water content, whereas the degree of compaction, confining pressure, and loading frequency could enhance the resilient modulus. Furthermore, a modified model considering the F–T cycle number and stress state was established to predict the dynamic resilient modulus. The calculated results of this modified model were very close to the experimental results. Consequently, calculation of the resilient modulus for F–T cycles considering the dynamic load was appropriate. This study provides reference for research focusing on F–T cycles with groundwater supply and the dynamic resilient moduli of subgrade soils in seasonally frozen areas.

关键词： 冻融循环   玄武岩纤维   水泥土   力学性质  

摘要： 为了研究冻融循环作用下土的性质对纤维水泥土力学性质的影响,以玄武岩纤维和水泥为加固材料,选取两种不同类型土体制作成试件进行无侧限抗压强度试验和冻融循环试验。通过研究发现,玄武岩纤维的加入未必能提高水泥土的强度,土体的性质是影响水泥土无侧限抗压强度的主要因素之一。冻融循环作用下土的性质对水泥土力学性质及破坏状态具有重要的影响。随着冻融循环次数的增加,水泥土的无侧限抗压强度逐渐减低,而纤维的添加可以有效降低水泥土强度损失,提高水泥土抵抗冻融循环的能力。研究结果可为冻融循环作用下玄武岩纤维水泥土力学机理的研究提供一定的理论基础,可为纤维水泥土在季节性冻土区的应用提供一定的借鉴和参考。

关键词： 冻融循环   强度折减法   简化Bishop法   安全系数  

摘要： 为研究冻融循环作用对土质边坡稳定性的影响,利用强度折减法,通过大型有限元软件ABAQUS计算获得边坡的稳定安全系数,与简化Bishop法获得的理论安全系数进行比较,并以特征部位位移发生突变作为破坏判据,研究了坡度和冻融循环次数对边坡稳定性的影响。结果表明:采用有限元中边坡整体失稳的三种判据得到的安全系数相差不大,且与简化Bishop法得到的理论解误差很小;当坡度一定时,边坡的安全系数随冻融循环次数增加逐渐降低,并最终趋于稳定;当冻融循环次数一定时,边坡安全系数随坡角的减小而增大,即边坡越平缓,安全系数越大,边坡稳定性越好,可为边坡稳定性影响因素的探究提供参考。

关键词： 保温混凝土   冻融循环   黏结滑移   本构关系模型  

摘要： 冻融循环作用下,钢筋与混凝土之间的黏结锚固性能遭到破坏,而钢筋与混凝土之间的黏结滑移本构关系模型能够综合反映两者间的黏结锚固性能。通过中心拉拔试验,研究了冻融循环作用下钢筋与玻化微珠保温混凝土(TIC)黏结锚固性能的退化规律,测定了试件的黏结滑移曲线,并与普通混凝土(NC)对比分析。研究结果表明:冻融循环次数增大,钢筋与TIC试件黏结锚固作用减弱,极限黏结强度减小,峰值滑移增大,与NC试件变化规律一致;相同冻融循环次数后,TIC试件的极限黏结强度大于NC试件,且其峰值滑移小于NC试件;冻融循环200次后,TIC试件破坏形式为拔出破坏,而NC试件为劈裂破坏。进一步基于试验研究,提出了冻融循环作用前后钢筋与玻化微珠保温混凝土黏结滑移本构关系模型,该模型与试验结果吻合较好,对于玻化微珠保温混凝土材料在工程实践中的应用和相应规范的完善具有参考价值。

关键词： Lignin  

摘要： The strength of silty soil in the Yellow River flood area is low caused by poor grain composition and other features. In order to improve the strength of silty soil in the Yellow River flood area, the lignin is used to reinforce the silty soil. The relationship between the unconfined compression strength of silty soil and the mixing amount of lignin, the number of freezing and thawing cycles and curing period are analyzed. The unconfined compression strength test and freezing and thawing test are carried out on soil reinforced by lignin with a certain moisture content. The experimental results show that the lignin can improve the unconfined compression strength of silty soil. Under a certain number of freezing and thawing cycles, the unconfined compression strength of lignin-improved soil increases at first and then decreases with the increase of lignin proportion. The unconfined compression strength of silty soil is greatest when the mixing amount of lignin is 5%. When the amount of lignin is constant, the unconfined compression strength of reinforced soil increases with curing period. When the mixing amount of lignin is 5%, the strength of lignin-improved soil at 28 days is 1.77 times stronger than at 7 days. As the number of freezing and thawing cycles increases, the unconfined compression strength of lignin-improved soil decreases. Under the same number of freeze-thaw cycles, the reduction of unconfined compression strength in lignin-improved soil is less than that of plain soil, demonstrating that the durability of lignin-improved soil is better than that of plain soil. Based on SEM analysis, it can be clearly shown that lignin can effectively fill the pores between soil particles to improve the strength of soil. However, it does not gradually increase with the increase of mixture amount, and an optimal amount of admixture exists. © 2020, Science Press. All right reserved.

关键词： 钢筋混凝土梁   再生粗骨料混凝土   冻融循环   静力试验   受弯性能  

摘要： 为了研究冻融循环对再生粗骨料混凝土梁受弯性能的影响,首先通过冻融循环试验研究不同冻融循环次数对再生粗骨料混凝土质量损失率、立方体抗压强度和相对动态弹性模量的影响;然后对经历不同冻融循环次数(0、25、50、75)的再生粗骨料混凝土梁进行受弯性能试验,研究了试件的破坏形态、开裂荷载和极限荷载、混凝土和钢筋应变、跨中挠度等。结果表明:冻融循环次数由0增加到25次时,再生混凝土的质量呈增加趋势,冻融循环超过25次后,再生混凝土的质量呈不断减小的趋势;抗压强度和相对动态弹性模量随着冻融循环次数的增加而减小;再生混凝土梁的开裂荷载和极限荷载随冻融循环次数的增加而减小;再生混凝土梁的极限挠度随冻融循环次数的增加呈现出不断减小的趋势。

关键词： 模型计算   试验观测   理论误差分析   冻融循环试验   河道堤防   混凝土应力分布  

摘要： 结合冻融循环观测试验,采用模型计算方法探讨冬季低温条件下河道堤防混凝土的应力分布。结果表明:模型计算值和试验监测值之间的总体相关系数高于0. 6,可用来计算其应力分布。当冻融循环次数增加到最大值后,混凝土应力呈现纵向指数变化,应力变化逐步趋于稳定,存在明显变化的临界点。研究结果对于北方河道堤防混凝土力学分析具有重要的参考价值。

关键词： 气泡混合土   冻融循环   强度损失   质量损失   纤维  

摘要： 为解决冻土地区普通路基由于保温性能差导致的路基病害问题,采用保温隔热性能好的气泡混合土作为路基填料,可起到保护冻土、减少病害的作用。为探讨气泡混合土的抗冻性能,选取了不同容重的气泡混合土试件进行冻融循环试验研究,研究气泡混合土质量及强度损失规律,从而获知气泡混合土的容重对其抗冻性能的影响;进而,向气泡混合土试件中掺入玻璃纤维,探讨其对气泡混合土抗冻性能的增强作用。结果表明:气泡混合土的抗冻性能随着容重的增大而提高,表现为容重越大,所能经受的冻融循环次数越多,抗压强度和质量损失率越低;容重为800kg/m^3的气泡混合土试件经过15次冻融循环后抗压强度迅速降低,经过100次冻融循环后,试件的质量损失达到9.2%;而容重为1 200kg/m^3的气泡混合土试件在经过50次冻融循环后,抗压强度才开始明显降低,经过100次冻融循环后,试件的质量损失只有4.5%。玻璃纤维能显著提高气泡混合土的抗冻性能,其抗压强度损失率和质量损失率明显较未掺纤维的普通气泡混合土要小,且抗压强度和质量损失的速率明显降低;不同容重的气泡混合土试件掺入纤维后,经过50次冻融循环后,试件的抗压强度损失减少50%以上,质量损失减少40%以上。

关键词： 钢筋混凝土柱   冻融循环   拟静力试验   轴压比   抗震性能  

摘要： 为研究冻融环境下钢筋混凝土柱的抗震性能,采用人工气候实验室对6根依据GB 50011-2010《建筑抗震设计规范》所设计的框架柱进行了冻融循环试验,并观察了该冻融循环下材料层面和构件层面的冻融损伤发展过程。通过拟静力加载试验,分析了不同冻融循环次数和轴压比对试件破坏形态、滞回曲线、承载能力、变形能力和耗能能力等的影响。结果表明:随着冻融循环次数的增加,试件均发生以弯曲变形为主的弯剪破坏,承载力和耗能能力均有不同程度的退化,延性呈现先增后降的变化;当冻融循环次数相同时,随着轴压比的增大,试件破坏形态由大偏心受压破坏转为小偏心受压破坏,试件承载力和耗能能力均呈先增大后减小的趋势,延性逐渐减小。

关键词： 纤维水泥土   冻融循环   劈裂抗拉试验   双曲线模型  

摘要： 对素水泥土及玄武岩纤维水泥土进行了冻融循环作用前后的无侧限抗压、劈裂抗拉试验,探讨并对比了冻融循环次数、养护龄期、水灰比、纤维掺量等因素对两种水泥土力学性能的影响规律。结果表明:掺入玄武岩纤维后水泥土的冻融强度损失率降低;水泥土的冻融强度损失率随水灰比的增大而增大,随龄期的增大而减小;冻融后水泥土的无侧限抗压强度、劈裂抗拉强度与其受到的冻融循环次数之间的关系可用双曲线拟合;水泥土的劈裂抗拉强度与无侧限抗压强度的比值在14%~17%之间。