在土力学课程中融入思政元素是落实高等教育"立德树人"这一根本任务的重要途径.现阶段土力学课程思政尚处于探索阶段,对思政的理解和重要性有待提升.从分析现阶段土力学课程思政存在的问题出发,结合学科和专业特点,制定课程育人目标,从先进人物事迹、专业术语、自然和生活现象、经典工程案例中发掘和提炼各类思政元素,以问题导入开展课程思政的教学实践.在思政过程中,应加强对教师思政能力和学生实践创新能力的培养.实践表明,课程思政有助于培养学生求真务实、团结协作、开拓创新、追求卓越的工匠精神及卓越工程师优秀品质.

月球基地建设是当前各国月球探测与开发计划的核心目标之一,受限于地月运输成本高昂,以月壤作为基材研发各类建筑材料是目前最为经济合理的方案.发展月壤基构件成型技术和纤维制造技术,研发月壤基纤维增强复合材料,有望为月球基地建设提供原材料保证.月壤基纤维可结合3D打印技术制备各种壤工织物,如:壤工格栅、壤工布以及壤工袋等.针对目前所提出的月球基地设计构思,讨论月球基地建设中可能遇到的工程问题,基于加筋原理提出了相应的壤工结构物形式.最后,系统总结了壤基材料加筋月壤技术应用于月球基地建设时需突破的技术挑战和面临的关键科学问题.该文研究对原位利用月球资源、开展月球基地建设具有重要意义.

新一轮科技革命和产业变革对工程教育的改革与发展提出了新的挑战,新工科正是对这一挑战和要求的积极回应,在实践教育过程中培养大学生的工程创新能力是土木工程专业新工科建设的重点.以武汉大学为例,针对目前普遍存在的重理论和轻实践、不重视创新能力培养的现状,探索土力学课程的实践教学改革.构建第一课堂、第二课堂和课堂外实践教学的"三课堂"协同育人体系,提出"三课堂"的具体建设内容,探讨构建实践教学体系的关键问题,介绍具体保障措施和教学改革经验与效果.

随着城市地铁建设快速发展,地铁车站基坑的变形要求越来越严格,基坑土层设计参数的选择面临着极大挑战.利用思维进化算法(MEC)优化BP神经网络的初始权值和阈值,结合有限元数值模拟,提出基于基坑水平位移的土层参数反演分析方法.采用文献算例对该方法进行验证,并与不同反演方法进行对比.研究结果表明:1)MEC-BP神经网络对多工况水平位移的反演分析结果与文献结果基本一致,验证了该方法的有效性和实用性;2)MEC-BP神经网络的收敛速度快于遗传神经网络(GA-BP),其反演结果优于常规BP神经网络、GA-BP方法和修正高斯-牛顿法(G-N);3)采用标量误差函数Ferr进行寻优,可以提高MEC-BP法水平位移反演分析结果的稳定性和准确性.

Researching the mechanical properties and failure mechanism of rock-bolt interface is of great signifi-cance since sliding between bolt and rock is a major failure form of anchorage system. With the microscopic bond model proposed by one of the authors previously, the pull-out test of rock bolts was simulated using discrete elementmethod (DEM). The complete load-displacement curves, the distribution of axial force and the interfacial shearstress were investigated, respectively. Furthermore, the microscopic failure mechanism of bolt-rock interface wasanalyzed according to the type and fabric of broken bonds. Research results are concluded as follows: 1) the simulatedload-displacement curves were consistent with those from laboratory tests; 2) with the increase of anchorlength, peak load value increased while average cohesive strength of anchor interface decreased; 3) progressivefailure occurred in the anchor interface after pull load reached peak; 4) on macroscopic level, the failure of anchoredsegment exhibited as interface sliding; whereas on microscopic level, the failure manifested as the tensilefailure of bonds near interface and the propagation of micro-cracks along the direction of axial force.

随着城市建设的迅速发展,基坑环境对变形要求越来越严格.小应变土体硬化模型(HS-Small)能考虑在小应变条件下土体刚度呈非线性变化的特征,逐渐成为城市深基坑数值模拟常用的本构模型之一.推广应用该模型的关键是如何确定不同土体的模型参数.针对武汉地区天然老黏性土,利用高压固结仪和GCTS动三轴仪进行了固结试验、三轴剪切试验和小幅值动三轴试验研究,分别获得了压缩指标、强度参数和小应变刚度.在此基础上,应用PLAXIS软件模拟了三轴固结不排水剪切试验,通过与实测曲线对比进一步修正了HS-Small模型参数.结果表明,HS-Small模型可以较好模拟天然老黏性土峰前应力应变关系,采用低幅值动三轴试验获得小应变刚度是一种值得推广的实用方法.

为了研究化学侵蚀对裂隙岩体的影响,将天然花岗岩加工成板状样,用水刀预制单裂缝,然后将其浸泡在化学溶液中并施加竖向荷载,经过预定时间后进行单轴压缩试验.通过比较浸泡前、后试样质量和力学性质的变化,研究了溶液浓度、pH值、应力水平和浸泡时间等因素的影响.研究结果表明:封闭溶液条件下,试样的质量损失微小但力学性质劣化明显;经化学溶液浸泡后,试样压缩变形有从脆性向延性转变的趋势;酸性环境下的起裂应力、峰值强度和弹性模量最低,碱性环境次之,中性环境最大;随着浓度、应力水平及浸泡时间增加,起裂应力变化波动性较大,而峰值强度和弹性模量均单调减小.

The old clay in Wuhan is a kind of hard plastic clay with excellent structure,over-consolidation and developed joint fissures.The dimensional high-pressure consolidation test, unconfined compression test and conventional triaxial test were performed on undisturbed soil samples to evaluate the structure characteristics of soils.The undisturbed samples used in these tests were obtained from a foundation excavation of Hanyang.Then the triaxial test on remoulded samples was also conducted.Comparing the results of undisturbed samples with remoulded samples under the same condition,the results showed that the cohesion of remoulded samples were significantly lower than the undisturbed soil.In addition, undisturbed samples were generally in the form of strain softening and the remoulded samples for strain hardening during the triaxial shearing process.When the undisturbed samples consolidated under low confining pressure, the pore-water pressure was negative at later stage, which showed an obvious dilatancy phenomenon.

SummaryAs a result of deposition process and particle characteristics, granular materials can be inherently anisotropic. Many researchers have strongly suggested that the inherent anisotropy is the main reason for the deformation non‐coaxiality of granular materials. However, their relationships are not unanimous because of the limited understanding of the non‐coaxial micro‐mechanism. In this study, we investigated the influence of inherent anisotropy on the non‐coaxial angle using the discrete element method. Firstly, we developed a new discrete element method approach using rough elliptic particles and proposed a novel method to produce anisotropic specimens. Secondly, the effects of initial specimen density and particle characteristics, such as particle aspect ratio Am, rolling resistance coefficient β, and bedding plane orientation δ, were examined by a series of biaxial tests and rotational principal axes tests. Findings from the numerical simulations are summarized as follows: (1) the peak internal friction angle ϕp and the non‐coaxial angle i both increase with the initial density, Am and β, and they both increase initially and then decrease with δ in the range of 0–90°; (2) among the particle characteristics, the influence of Am is the most significant; and (3) for anisotropic specimens, the non‐coaxial angle can be calculated using the double slip and rotation rate model. Then, an empirical formula was proposed based on the simulation results to depict the relationship between the non‐coaxial angle and the particle characteristics. Finally, the particle‐scale mechanism of non‐coaxiality for granular materials was discussed from the perspective of energy dissipation. Copyright © 2016 John Wiley & Sons, Ltd.

Natural loess with large voids and weakly bonded structures is widespread in the arid areas of the world, particularly northwestern China. Recent experimental studies have shown that the mechanical behavior of natural loess is stress path dependent. In practice, soils influenced by the construction of earthen structures may undergo various complex stress paths that are very different from the conventional stress paths commonly considered in geolaboratory experiments. Because of the limitations of current technologies, real stress paths are difficult to obtain from field tests or physical modeling. This study focused on the deformation behavior of natural loess from Jingyang, China, under the stress paths around a shield tunnel. First, the stress paths around a shield tunnel were determined from the numerical data obtained at different positions in a distinct-element simulation of shield tunnel excavation in sand (for simplicity) and by using a novel method referred to as the equivalent stress ratio method. Second, a set of undrained triaxial tests were conducted using the conventional and complex stress paths. The experimental results demonstrate that the deformation characteristics of the loess are different at different positions around the shield tunnel, and the largest deformation appears in the lateral zone (0 degrees). This indicates that the lateral zone is the key zone to be controlled during shield tunneling. In addition, the relationship between the stress increments and the strain increments varies with the stress path. In a complete unloading path, the behavior of natural loess is largely elastic and linear. On the contrary, in a complete loading path or semiloading path, the behavior is largely inelastic and nonlinear, and this behavior is associated with the stress state and recent stress history. These results are valuable in establishing the constitutive relationships for natural loess under complex stress paths and may be useful for the construction of shield tunnels in loess areas. (C) 2017 American Society of Civil Engineers.

在寒区冻土层季节性退化演变过程和未冻土层存在的情况下,对发生典型冻拔破坏的桩基础进行受力分析,得到季节冻融循环演化过程中各土层桩侧摩阻力的计算公式,并在此基础上,对桩基础抗拔稳定性劣化进行研究,建立寒区深层冻土退化、土体出现未冻土层状况下桩基础发生冻拔破坏的临界承载力数值模型.以工程实例对桩基础的各个土层状况进行分析,在假设土的干容重、冻土的总含水量、地中热流值、冻土的导热系数不变,季节冻融层为强冻胀土条件下,分析桩长范围内各层土厚度随时间的变化以及最大冻深处截面应力随未冻土层厚度与桩长之比的关系,对季节循环演变中土体的冻拔力和桩侧摩阻力进行计算、比较,并对群桩基础的抗冻拔稳定性验算方法进行讨论.研究结果表明:部分多年冻土层退化为未冻土层,将导致桩基础的总抗拔力和临界失稳冻结深度减小.桩侧未冻土层厚度与桩长的比值和临界比值的比较结果可作为桩冻拔稳定性的判断标准.得到的临界承载力模型可以为寒区冻土层演化过程中桩基础稳定性评估提供数值分析依据.

The natural old clay in Wuhan is an overconsolidated stiff clay .It often shows strain-softening under the exca-vating and unloading condition ,which might cause some adverse impacts on deep pits and slopes .However ,its over-con-solidation ,structure and shear properties are not well recognized .In this paper ,first ,a set of high-pressure oedometer tests and undrained triaxial tests were carried out on its saturated undisturbed and remoulded samples ,respectively .Sec-ond ,the undrained triaxial tests of undisturbed samples were numerically simulated with super-loading Cam-clay model . It was founded that the natural old clay could be classified as a strong overconsolidated clay ,and the preconsolidation pressure and the structural strength obtained by two methods were consistent .Under low confining pressure ,the undis-turbed samples obviously present strain softening and shear dilatancy ,and the failure patterns are often influenced by the micro fissures .After the structure collapses ,the natural old clay presents little contraction ,which is different from natu-ral soft soils in the literature .The cohesion values of undisturbed samples are much higher than those of remoulded ones , and their internal frictional angles are very close .The stress-strain curves and pore pressure variation simulated by the su-per-loading Cam-clay model are generally in agreement with the experimental results .

The micro-parameters of parallel bond model could not satisfy the compressive strength and tensile strength simultaneously,this was a problem in the simulation of rocks.A set of uniaxial tension tests and uniaxial compression tests of rocks were simulated to investigate this problem.First,DEM specimens with different porosity ratio and differ-ent nonuniform coefficient were calibrated according to the laboratory test results of Lac du Bonnet granite.Second,the deficiency of the parallel bond model was pointed out and the improved methods were proposed from the perspective of microscopic failure mechanism.The simulation results showed that the microscopic parameters satisfied tension strength was one order of magnitude deviated from the microscopic parameters,which could also satisfy compression strength. Tensile characteristics and shear characteristics were considered in the parallel bond model,while the influence of nor-mal stress on the bond was ignored.This was the reason that the tension-compression strength ratio of rock was different from the experimental result.It was advised to use clumped particle model which could simulate particle breakage or ce-mentation model based on laboratory tests.

Water content plays an active and important role in the performance of the soil freeze–thaw cycle to form frozen soil mechanical properties. Monitoring the freeze–thaw cycle of soil with various types of soil with varied moisture content will provide a direct observation of the properties of soil in cold regions. This paper presents new findings from monitoring the freeze–thaw process of soil using a piezoceramic-based smart aggregate (SA). For comparison, clay soil and medium sand with different moisture contents were used to study the behavior of the soil under the freeze–thaw process. Two SAs were embedded in the soil specimens with a pre-determined distance between them, one as an actuator to generate a stress wave and the other as a sensor to detect the propagated wave. As the propagation of the emitted wave is sensitive to soil status and properties, it is possible to monitor the soil freeze–thaw process by interpreting the SA sensor signal. Based on the attenuation of the energy, a freeze–thaw status indicator was established to describe the freezing–thawing condition. Indicator values of soil specimens with different types and different levels of moisture in freeze–thaw cycles were studied. The test results indicate that the freezing duration in the freezing–thawing process varied for different types of soil and different initial moisture content of the soil. Soil with different particle sizes and moisture content will determine the frozen soil microstructure and its corresponding mechanical properties. Our results illustrate that if soil particle size is bigger, then the signal indicator is stronger; if the moisture content is higher for the same soil, then the signal indicator is stronger. The research presents an innovative method to investigate the freezing–thawing performance of soil and potentially points to a new method to study the variation of soil mechanical properties during the freezing–thawing process, which is a critical problem for infrastructure in cold regions.

Desiccation cracking of clay soil is of critical importance in many applications, such as industrial waste containment, hydraulic barriers, road embankments, and agricultural operations. The factors that influence cracking are known qualitatively, but it is not clear how to predict the initiation and propagation of cracks. This study presents a discrete element approach to modeling desiccation cracking in thin clay layers, considering material property changes. First, an aggregate shrinkage model based on the aggregate structure of clay was proposed, and the drying shrinkage of clay soil was modeled by imposing drying shrinkage kinetics for each aggregate at the micro-scale. Second, the clay soil was represented by an assembly of aggregates linked by bonds, and desiccation cracking of the clay layer was modeled using a three-dimensional discrete element code (PFC3D), with the aid of the embedded programming language FISH. When the clay layer is sufficiently thin, the water content gradient along the section can be neglected; thus, the shrinkage kinetics are the same for all of the grains of clay. In the model based on the discrete element method (DEM), the bond strength and contact stiffness changed during drying. Their changes were determined by matching the simulation results with the experimental data. Third, the DEM approach was validated by reproducing experimental desiccation tests performed on a thin clay layer in a disk shape. The geometric parameters of surface cracks were quantified using image analysis techniques and were compared with experimental observations. Fourth, some factors of influence, such as the sample thickness, the properties of the soil–base interface, micro-mechanical parameters, and shrinkage parameters, were investigated using the DEM model. The results obtained from the DEM analyses were compared with the results of prior research in this field of study. The approach used in this study is very promising for simulating desiccation cracking in thin clay soil because the model captures the initiation and propagation mechanism of desiccation cracks. Although this study was carried out on surface cracking in a thin clay layer, the extension of this methodology is of potential benefit not only for predicting three-dimensional desiccation cracking in real clay liners but also for modeling cracking in other materials with properties that vary with water content or temperature, such as concrete and rock.

Desiccation cracking of soils is of critical importance in many applications, such as industry wastes, hydraulic barriers, road embankments, and agriculture practice. This paper presented a numerical approach for modelling desiccation cracks in a thin clay layer with considering the changes in material properties during drying. Based on the micro-structure theory of clay, the swell and shrinkage behavior of clay could be explained by the swelling and shrinkage of aggregates. Therefore, an aggregates-shrinking model was proposed and its parameters were determined by matching the experimental data in literature. Then, the desiccation cracking of clay in plate shape was modeled by a three-dimensional discrete element code (PFC3D). The results obtained from the proposed numerical model had been compared with the experimental results in literature, which showed that the proposed DEM model can capture the initiation and propagation of cracks in a thin desiccated clay layer.

In nature, desiccation cracks are one of the major factors to cause the progressive failure of clay dams, soil slopes and clay liners. So it is urgent to develop the effective approach to study the mechanism of desiccation cracking. For this sake, a new DEM model based on the shrinkage mechanism of clay soils is developed. In the model, the radius, bond strength and stiffness of the grains are all varied with the water content, and the parameters are determined by matching the experimental data. Then, the initiation and propagation of desiccation cracks in a thin circular clay layer with rough boundaries are simulated using the software of PFC3D. And the geometric parameters of surface cracks are quantified using the image analysis techniques to be compared with the experimental observations. The conclusions are drawn as follows: the simulated cracking mechanism includes the effects of tensile stress and flaws in the sample; the procedure of crack propagation obtained from DEM presents the character of three stages, and the evolution curves of crack parameters are similar to those from laboratory experiments; and the effect laws of the soil-base cohesion on the crack patterns are also in agreement with the results in literatures.

Firstly introduces the static dynamic combined consolidation technology and its characteristics,highlighting the difference from the traditional dynamic compaction technology,then describes the core theory of the technology,illustrates the design and construction features simultaneously.Finally,the design and testing of the Xiamen Jimei Bridge connection project on Gaoqi side(1st and 2nd stages) is introduced,in which saturated hydraulic fill soft soil foundation treatment performed,a reference for similar engineering applications.

通过模型试验,采用风干砂土实测了绕墙底转动(RBT)位移模式下刚性挡墙土台被动土压力的大小,研究了土台土压力的分布规律以及土台宽度对土压力的影响.与Daly M.P.和Powrie W.(2001)提出的多层楔体试算法结果对比表明:土压力实测值接近于计算值,合力作用点高于计算值,在工程中按多层楔体试算法计算砂土台被动土压力是偏于安全的.