The occurrence of road damage, such as frost heave and thaw settlement, is highly likely in saline soil subgrades in seasonally frozen areas due to traffic loads and freeze–thaw cycles (FTC). In this regard, a low-temperature dynamic cyclic triaxial test was conducted to investigate the dynamic characteristics of carbonate saline soil under traffic load. The study explores the impact of salt content (SC) and the number of FTC on the backbone curves, the dynamic shear modulus (TDSM), and the damping ratio (TDR) characteristics of saline soil. An improved H-D model was employed to derive the dynamic backbone curve, and TDSM and TDR empirical formulas were established.The study's results show that the backbone curves of saline soil exhibit typical nonlinear and strain-hardening characteristics. Additionally, a higher salt content or more FTC result in a smaller TDSM and a larger TDR of the remodeled saline soil. TDSM shows an inverted “S” shape with an increase in cyclic shear strain, and the decay rate of TDSM increases when the cyclic shear strain is greater than 10-4 and less than 10-3. The decay rate of TDSM decreases and approaches a constant value after the cyclic shear strain exceeds 10-3. The decay of TDSM of low-salt soils (salt content less than 0.5%) mainly occurs in the first six freeze–thaw cycles. In contrast, the decay of TDSM of high-salt soils (salt content more than 0.5%) remains highly dependent on the number of FTC. Furthermore, TDR show an flat “S” shape with an increase of cyclic shear strain. The rate of increase in TDR of low-salt soil decelerates after six FTC, while the rate of increase in TDR of high-salt soil decelerates after nine FTC. Finally, empirical formulas for TDSM and TDR were established by varying the fitting parameters. The results of this study provide a useful reference for engineering projects in regions that encounter seasonal freezing. These findings will assist engineers in the design and construction of structures that can withstand the detrimental effects of traffic loads and FTC.

为探究冻融循环条件下采用粉煤灰改良盐渍土路基的抗剪切性能,选取绥化至大庆高速公路沿线盐渍土样进行不同粉煤灰掺量下的直剪试验研究.结果表明:历经多次冻融循环,盐渍土黏聚力和内摩擦角均出现下降趋势;随着粉煤灰掺量的增加,改良盐渍土的内摩擦角、黏聚力和抗剪强度呈现出先升高后下降的趋势;当粉煤灰掺量为 15%时,盐渍土样的黏聚力、内摩擦角等力学指标均达到最大值.绥大高速公路地区路基修筑过程中,可以在路基土中掺加15%粉煤灰,以提高路基土抗剪强度及抗冻融循环作用的能力.

The freezing and thawing of roadbed soils in seasonal frozen zones can cause uneven settlement and other road problems, which puts road operation at risk. This paper focuses on the rapid construction of expressways and analyzes the effects of using fly ash and cement as modifiers on the physical properties and chemical composition of subgrade soil. The study found that cement admixtures can improve soil mechanical attributes and frost resistance, while also increasing the degree of fly ash hydration. And the freeze-thaw cycle process can enhance the mechanical characteristics of soils with higher cement admixture content. This is due to the development of hydrates in cement fly ash-enhanced soils during freeze?thaw cycles, resulting in a denser interior structure. The use of neural network prediction analysis showed that using ANN4-10-3 to forecast soil mechanical property parameters can produce superior results. Therefore, it is recommended to use cement fly ash-enhanced soil for roadbed construction in seasonal freezing areas, and neural network can be used to predict soil mechanical parameters.

In the course of the construction of deep foundation pits during the winter in seasonally frozen areas, the pit wall soil is often unstable due to frost heave and thawing settlement, which leads to hidden safety hazards in engineering construction. Based on the analysis of the deformation data of a pile-anchor supporting a deep foundation pit in Harbin obtained from monitoring during the winter, the influence of freezing and thawing cycles was investigated. The results show that the horizontal displacement in the middle of the shallow layer of the foundation pit is significantly larger than that on both sides during the freeze–thaw cycles, and the spatial effect becomes noticeable. The stress concentration at the external corner of the foundation pit, coupled with the effects of atmospheric precipitation and freeze–thaw cycles, led to the maximum growth rate of horizontal displacement up to 1.40 mm·day−1. The external corner effect is evident from 1 m in the shallow layer of the pit to the depth H/2 of the foundation pit. The support scheme is generally feasible, and we can appropriately enhance the support of the shallow layer of the foundation pit during the freeze–thaw cycles. For similar projects experiencing freeze–thaw cycles, the safety reserve can be appropriately enhanced when carrying out support design.

The contact and bonding of soil particles are affected by the fine particle content of silty sand and the freeze-thaw cycle effects in the seasonal frozen zone, which are reflected as the dynamic characteristics of silty sand from the macroscopic point of view. The dynamic stress, dynamic shear modulus, dynamic shear modulus ratio, and damping ratio of Songhua River silt with different contents of fine soil particle (less than 0.075 mm) after repeated freeze-thaw cycles were studied respectively using a low-temperature dynamic triaxial test system and were compared with those of quartz sand. In order to approach the real test results, a piecewise equation was used to solve for the dynamic parameters. The results show that repeated freeze-thaw cycles have a great influence on reducing the dynamic stress, the dynamic shear modulus, and the dynamic shear modulus ratio, while they increase the damping ratio. For a given fine particle content and number of freeze-thaw cycles, the dynamic stress, dynamic shear modulus, and damping ratio of the Songhua River silt with fine particles are larger than those of quartz sand when the dynamic strain reaches 0.2%, and the difference gradually decreases as the number of freeze-thaw cycles increases. The dynamic shear modulus of the Songhua River silt with fine grains decreases more slowly with increasing dynamic strain than that of quartz sand. Therefore, a normalized empirical model was established to describe the relationship between the dynamic shear modulus ratio, the damping ratio, and the dynamic strain. This model is suitable for Songhua River silt with different fine particle contents and numbers of freeze-thaw cycles, and it provides good prediction results. Furthermore, the evolution of the model parameters with the experimental conditions was analyzed, and the limit value of the fine particle content was determined to be 10%. After repeated freezing and thawing, the influence of the fine particle content on parameters a and c weakened. The regression relationship between the model parameters and the test conditions can be described by a binary quadratic equation. It is suggested that the soil parameters should be used for the dynamic response analysis of Songhua River silt with fine grains after five freeze-thaw cycles.

We conducted dynamic triaxial tests of undisturbed soil samples under different control parameters using the Global Digital Systems (GDS) dynamic triaxial instrument. We investigated the dynamic and engineering characteristics of undisturbed soil under a freeze-thaw cycle. When the dynamic load amplitude and the number of freeze-thaw cycles were adjusted, we explored the cumulative plastic strain, dynamic elastic modulus, and dynamic strength of undisturbed soil, and we then proposed appropriate fitting formulae to compute the cumulative plastic strain, dynamic elastic modulus, and dynamic strength. The findings revealed that as the number of freeze-thaw cycles increased, the cumulative plastic strain grew, the dynamic strength progressively fell, and the dynamic elastic modulus dropped first, but then increased. The critical physical and dynamic features of soil changed dramatically during one to six freeze-thaw cycles. This study’s suggested formula for the average growth ratio can directly reflect the cumulative plastic strain fluctuation of soil throughout freeze-thaw cycles. The formula has a good fitting effect on undisturbed soil, according to the test findings, and the accumulative plastic strain, dynamic elastic modulus, and dynamic strength may be computed within a specified range. The findings of this study contribute to a better understanding of the effect of the freeze-thaw cycle on the dynamic characteristics of undisturbed silty clay, as well as a theoretical foundation for the design and construction of silty clay highway subgrade in seasonally frozen regions as well as the dynamic analysis of vehicle simulation in seasonally frozen regions.

为探究冻融循环作用对粉煤灰加固路基土力学性能影响,对冻融循环次数、含水率、粉煤灰掺量不同的盐渍土开展无侧限抗压试验和三轴剪切试验,研究冻融循环后土体的应力-应变曲线、无侧限抗压强度、黏聚力和内摩擦角的变化情况.使用Design-Expert 8.0软件,研究冻融循环次数、粉煤灰掺量、含水率及各因素交互作用对盐渍土力学性质影响的显著性程度.结果表明:多次冻融循环后,盐渍土无侧限抗压强度、黏聚力和内摩擦角均有下降,经历1～7次冻融循环时,土体各力学参数下降速率较快;随着粉煤灰掺量的增加,盐渍土的内摩擦角、黏聚力、无侧限抗压强度和抗剪强度呈现出先升高后下降的变化趋势.基于显著性分析理论,冻融循环次数与含水率的交互作用对盐渍土无侧限抗压强度和黏聚力的影响较为显著,粉煤灰掺量与冻融循环次数的交互作用仅对无侧限抗压强度影响较为显著.为提高路基土强度及抗冻融的能力,加快粉煤灰综合利用进度,根据软件和公式模拟结果,推荐在路基土中依据质量比掺加15％粉煤灰,并将经历7次冻融循环后压实盐渍土的力学指标作为工程设计参考值.

以绥满高速卧白施工段湿地路基软土为研究对象,将土样经过不同冻融循环处理后,使用动三轴仪器进行试验,分析该湿地地区的路基软土受冻融作用后,在不同动应力下累积应变随振次的变化规律.结果表明:在加载初期(振次N≤500),累积塑性应变会随着振次的增加而迅速增加,而当振次N≥1000后,其增长速率逐渐减缓且趋于平稳;随着冻融循环次数的增加,累积塑性应变量增大;随着振次的增大,滞回圈越来越瘦小,滞回圈的排布也越来越密集;提出平均增长比,用以表示间隔某几次冻融前后的最终累积塑性应变差值受冻融影响的程度;提出一种新的累积塑性应变拟合模型,缩小了指数模型累积塑性应变随振次变化的程度,该模型更加符合"稳定型"累积塑性应变随振次发展的形态;分析了相关拟合参数随冻融循环、动应力的变化趋势.

为研究寒区饱和含黏粒粉砂的动力学特性,对松花江河漫滩饱和含黏粒粉砂土进行循环三轴试验,分析冻融循环、动应力幅值、有效围压、荷载频率等环境因素对饱和粉砂土动剪切模量与阻尼比的影响.结果表明:冻融循环对饱和粉砂土动剪切模量与阻尼比影响显著,表现为在不同冻融次数区间内两者不单一变化;未冻融饱和粉砂土动剪切模量随动应力幅值、有效围压、荷载频率的增大而增大,而阻尼比随动应力幅值、有效围压、荷载频率的增大而减小.并进一步提出了可预测该种土不同工况下动剪切模量与阻尼比的经验公式.研究成果可以为粉砂土在路基工程中的稳定性与安全性设计提供参考.

利用GDS动态三轴试验系统研究不同细粒含量粉砂土经历多次冻融循环后的动应力、动剪切模量、动剪切模量比和阻尼比变化规律.考虑动态过程中滞回曲线的非对称性,采用分段方程求解动力参数.结果表明,反复冻融循环对降低动应力、动剪切模量和动剪切模量比有很大影响,并使阻尼比增大.对此,建立了描述动剪切模量比、阻尼比与动应变变化关系的归一化经验模型,该模型适用不同的细粒含量和冻融次数条件,能给出良好的预测结果.进一步分析模型参数随试验条件的演化过程,确定细粒含量界限值为10％,且反复冻融后,细粒含量变化对参数a、c的影响减弱.模型参数和试验条件之间的回归关系可通过二元二次方程进行描述.建议在粉砂土动力响应分析中采用冻融循环5次后的土体参数.

为提高粉砂土地基抵抗循环荷载的能力,采用工业废料粉煤灰对粉砂土进行改良实验.选用5种不同配合比的粉煤灰改良饱和粉砂土,对其进行直剪试验、动三轴试验和扫描电子显微镜(scanning electron microscope,SEM)试验,分析了粉煤灰掺入量对饱和改良粉砂土抗剪强度的影响,并将不同粉煤灰掺入量的饱和改良粉砂土的应力应变曲线用Hardin-Drnevich双曲线模型进行拟合,讨论粉煤灰掺入量对拟合参数的影响,随后提出了仅考虑粉煤灰掺入量影响的动弹性模量经验公式和阻尼比经验公式,最后通过SEM试验照片对素土和15％粉煤灰掺入量的改良土的微观结构进行对比.结果表明:在一定限度内,增加粉煤灰的掺入量可以有效提高土体抗剪强度、初始弹性模量,降低阻尼比的增长速度.

To explore the mechanism of the microstructural change in salinized soil under freeze-thaw cycles and the strength characteristics of subgrade salinized soil improved by fly ash, an unconfined compressive test, a triaxial shear test, and a scanning electron microscopy test were carried out using salinized soil samples with different fly ash contents along the Suihua to Daqing expressway in China. The results showed that after several freeze-thaw cycles, the unconfined compressive strength, triaxial shear strength, cohesion, and internal friction angle of saline soil showed a decreasing trend. With an increase in the fly ash content, the internal friction angle, cohesion, unconfined compressive strength, and shear strength of the improved saline soil first increased and then decreased. When the fly ash content was 15%, the mechanical indexes, such as cohesion and the internal friction angle, reached the maximum value. Microscopic test results showed that the freeze-thaw cycle will lead to an increase in the proportion of pores and cracks, an increase in the average pore size, and a loosening of the soil structure. The addition of fly ash can fill the soil pores, improve the microstructure of the soil, increase the cohesive force of the soil particles, and improve the overall strength of the soil. Fly ash (15%) can be added to subgrade soil in the process of subgrade construction in the Suihua-Daqing expressway area to improve the shear strength and the resistance to freezing and thawing cycles. These research results are conducive to promoting the comprehensive utilization of fly ash, improving the utilization rate of resources, and promoting sustainable development, thus providing a reference for the design and construction of saline soil roadbed engineering in seasonal frozen areas and the development and construction of saline land belts in seasonal and winter areas.

为研究饱和粉砂在冻融循环作用下的剪切特性,基于直剪试验,对饱和重塑粉砂在经过不同次数冻融作用后的黏聚力、内摩擦角以及抗剪强度的变化开展研究.研究结果表明:随着冻融次数的增加,饱和粉砂黏聚力,内摩擦角及抗剪强度总体均呈现先波动,后平稳,总体下降的趋势;在现有研究的基础上改进,提出饱和粉砂土抗剪强度随冻融循环变化表达式;在实际工程中,当粉砂含水率不小于12％ 时,进行冻融性质检测循环次数应尽量不小于13次.

考虑热对流和热传导作用,结合Laplace变换和Laplace反演推导基坑土体温度场解析解,并采用Matlab编程求解、分析其温度分布规律.依托哈尔滨某越冬施工的深基坑工程实例,采用有限元数值分析方法,分析冻胀对基坑影响及安全措施控制效果.研究结果表明:基坑暴露在低温环境下的时间越长,土体的冻结深度越深,但冻结深度增加速率随时间逐渐变慢;受冻胀影响基坑围护结构裸露段水平位移增加了11.5％～35.7％,且围护结构角隅位置受冻胀影响最大,冻胀对基坑影响不容忽视;较未设置保温层工况,保温层的设置使围护结构水平位移降低了11.6％～22.6％,保温层隔热效果明显.

需求调查与分析是学术英语教学中的一个重要环节.通过持续性地对土木工程专业研究生学术英语教学过程进行量化调查,并对调查数据进行分析研究,可以明确土木工程专业学术英语的教学导向,进而提升学术英语的教学质量和课堂教学效果,最终达到培养学生学科前沿学术英语水平综合运用能力的教学目标.同时通过分析学生对学术英语课程学习内容的需求,更进一步找到相应对策调动学生学习英语积极性,探索有效培养学术英语应用能力的合理课程设置.

为分析列车荷载作用下有砟轨道的动力响应,文章应用ABAQUS有限元软件建立三维路基基床有限元模型,采用无限元边界条件,分析了路基基床在静轮载5,7.5,10,12.5,15t五种情况下,速度分别为60,80,100km/h条件下的动力响应.有限元分析结果表明:(1)随着列车静轮载的增大,基床表层的竖向位移的幅值会逐渐变大,速度越大,静轮载的增加对竖向位移的增加影响越显著;(2)随着列车速度的增大,基床表层的竖向位移的幅值会逐渐变大,静轮载越大,速度的增加对竖向位移的增加影响越显著;(3)随着动荷载与选取点距离的缩短,选取点的竖向位移开始上下振动并逐渐增大,达到幅值后随着动荷载与选取点距离的增加,选取点的竖向位移逐渐恢复并有上下振动的现象.

以哈尔滨某越冬深基坑工程为实例,该基坑采用土钉墙、支护桩、冠梁、锚杆、桩间挂网喷射混凝土相结合的支护形式,对基坑进行了监测,并对监测数据进行了安全分析.监测结果表明:受土体冻融及降水影响,基坑周边路面沉降及排桩最大水平位移数值较大,但并未影响基坑支护结构的安全.在基坑开挖过程中基坑支护结构较安全.

采用半解析有限元法建立了列车-轨道-地基土相互作用模型,通过线性赫兹关系考虑列车模型与轨道模型之间的动力相互作用,再通过动力平衡将轨道模型与地基土模型进行耦合;随后在轨道不平顺的激励下,计算列车沿线运行产生的地基反力;将此力作为由有限元软件ABAQUS建立的求解轨道沿线环境振动模型的输入,求得列车通过时引起的沿线场地的环境振动;利用北京某城轨线路区间站之间的环境振动观测数据对计算结果进行验证,证明了所建立的计算方法是有效的.这套计算方法具有一定实用价值可用来评估现有线路的环境振动,也可用来规划新修建线路附近场地的环境振动.

结合哈尔滨市某深基坑工程实例,从冻胀期与融化期两方面,监测了季冻区该深基坑桩锚支护体系的安全性,指出深基坑侧向水平位移在冻胀期与融化期均呈现复合式变形趋势,且变形趋势与大气温度变化趋势具有一致性和滞后性.

在桩基础设计过程中,若对桩基负摩阻力考虑不当会引起桩基承载力不足甚至基础破坏等问题.基于国内外对不同地质条件中桩基负摩阻力的研究成果,进一步总结了桩基负摩阻力特性,可为类似桩周土体中桩基负摩阻力的优化设计提供一定参考,也对进一步预防桩基础病害的发生具有重要意义.