Diffusion of water across surfaces generally involves motion on an uneven and vibrating but otherwise stationary substrate. Based on molecular dynamics simulations, we study the diffusion behavior of water nanodroplets on the compressed phosphorene at different temperatures. The compression is applied in three different ways: equal biaxial compression, uniaxial compression along armchair and zigzag directions As the compressive strain increases, the diffusion coefficients are first reduced and then increased in all three cases at T = 300 K. When the compressive strain exceeds 1.6%, the diffusion coefficient grows the fastest for the case of equal biaxial com- pression. As the temperature increases, two different modes are observed at the lower strain level <= 1.4%) and relatively higher strain level >= 1.4%). In the regime of lower level of strain, the diffusion coefficient exhibits an oscillating trend as the temperature increases. In the regime of higher level of strain, the diffusion coefficient increases linearly as the temperature increases. The fastest diffusion occurs under the equal biaxial compressive loading at the strain level of 2.4% and temperature T = 340 K. The different diffusion behaviors of water nanodroplets are found to be related to the surface morphologies of phosphorene under compression, as well as friction coefficient and diffusion energy barrier of water molecules. Our results show that compressive deformation of phosphorene and temperature are important to control the dynamics of water molecules on the phosphorene. The phenomena reported here enrich the knowledge of molecular mechanisms for nanofluidic systems, and may inspire more applications with phosphorene and other 2D materials.

针对刚性基底上不可压缩弹性薄膜的轴对称球形压痕问题,采用了一种基于Kerr模型的简单解析求解方法.在该方法中,薄膜上表面的接触压强与位移为线性微分关系.之后利用贝蒂互等定理,求解了该问题的高阶渐近解,推导了接触力、压痕深度和接触半径之间的显式关系.当忽略高阶项时,得出的高阶渐近解与现有研究中的低阶解相同.此外还建立了有限元模型来验证渐近解的精度.结果显示,与已有的低阶渐近解相比,高阶渐近解与现有的数值计算结果和有限元分析结果吻合得更好.

An analytical laminate model was newly proposed to predict the ultimate strengths of two-dimensional tri-axial braided composites under in-plane loadings. The composite was modeled as a laminate possessing four plies. Among these four plies, there were three plies consisting of unidirectional fibers along with surrounding matrix and one ply containing only matrix. A progressive ply failure analysis was performed. A series of experiments were conducted. The present model was verified experimentally by using our and other researchers' data. Moreover, we compared this model's results with the numerical ones obtained by us. The results show that the present model has the potential to predict the effective elastic properties and ultimate strengths of two-dimensional tri-axial braided composites. Finally, the effect of the braid angle on the mechanical properties of a two-dimensional tri-axial braided composite was explored based on the mentioned model.

指出了页岩的力学特性对于页岩气开采中的钻井,压裂施工有着重要的影响.以重庆石柱的页岩为研究对象,用岩芯切割机对页岩样品进行处理,通过单轴实验对页岩抗压强度进行测试、通过三轴实验对页岩破坏规律进行了测试.实验结果表明:随着围压的增加,页岩的杨氏模量和泊松比也不断增加.同时基于brittle cracking模型,利用实验得到的页岩基本参数进行了数值模拟,得出页岩是偏向脆性材料,能很好地使用这种脆性开裂模型.这些研究可对页岩气的开采提供重要参数支撑

针对科卡金矿的边坡失稳,应用有限元软件对边坡建立了三维有限元模型.之后结合强度折减法,求解了边坡的稳定安全系数,得出了危险坡面的位置以及滑体形状,为边坡加固提供了理论基础以及数据支持.

The internal stress field of an inhomogeneous or homogeneous inclusion in an infinite elastic plane under uniform stress-free eigenstrains is studied. The study is restricted to the inclusion shapes defined by the polynomial mapping functions mapping the exterior of the inclusion onto the exterior of a unit circle. The inclusion shapes, giving a polynomial internal stress field, are determined for three types of inclusions, i.e., an inhomogeneous inclusion with an elastic modulus different from the surrounding matrix,an inhomogeneous inclusion with the same shear modulus but a different Poisson’s ratio from the surrounding matrix, and a homogeneous inclusion with the same elastic modulus as the surrounding matrix. Examples are presented, and several specific conclusions are achieved for the relation between the degree of the polynomial internal stress field and the degree of the mapping function defining the inclusion shape.

Charts are used extensively in slope practical application to meet the need of quick assessment of rock slope design. However, Charts for estimating the shear strength of the rock mass of a slope are considerably limited. In this paper, based on the Hoek-Brown (HB) criterion which is widely used in rock slope engineering, we present charts which can be used to estimate the Mohr-Coulomb (MC) parameters angle of friction phi and cohesion c for given slopes. In order to present the proposed charts, we firstly present the derivation of the theoretical relationships between the MC parameters and sigma(ci)/(gamma H) which is termed the strength ratio (SR). It is found that the values of c/sigma(ci) and phi of a slope depend only on the magnitude of SR, regardless of the magnitude of the individual parameters sigma(ci) (uniaxial compressive strength), gamma (unit weight) and H (slope height). Based on the relationships between the MC parameters and SR, charts are plotted to show the relations between the MC parameters and HB parameters. Using the proposed charts can make a rapid estimation of shear strength of rock masses directly from the HB parameters, slope geometry and rock mass properties for a given slope.

Safe disposal of contaminated tailings is recognized as the single largest environmental challenge facing the mining industry worldwide. Because suitable land for a new tailings pond is becoming rare and expensive, more and more mine operators tend to heighten the existing tailings dams to improve their storage capacity. However, this could lead to a decrease in the stability of the tailings dams. Based on comprehensive geotechnical investigations of a tailings dam in China, this paper presents a successful case study on heightening an existing tailings dam and extending its operational lifetime using a new drainage technique named the upward bending drain pipes system. The proposed system has 60 upward bending drain pipes arranged in the dam wall. The drain pipes are designed with combinations of slots and holes. With this arrangement, seepage on the hole surfaces changes to seepage on the slot surface, which increases the seepage capability by about 20 times compared with traditional drain systems. Based on a dam stability analysis, it is found that the value of the factor of safety of the dam can be improved around 20 % after slope drainage at an elevation of 2015 m. By using the proposed drainage system, the height of the tailings dam of this mine can be increased from 45 m (elevation 2015 m) up to 60 m (elevation 2030 m), which will increase by 8 million cubic meters the wet tailings storage and will satisfy mine operation for 5 years.

蠕变行为广泛地存在于岩石类材料中,并对岩体的稳定性有着重要的影响.因此,对岩石类材料的蠕变行为进行深入的研究是很有必要的.为了更好地揭示岩石的蠕变机制,结合分数微积分理论,建立了一个考虑损伤的蠕变模型.通过推导元件的蠕变方程,得到了整个模型的蠕变本构方程;并基于广义塑性力学理论对此方程进行了三维应力状态下的扩展.结合一系列的煤岩、泥岩和盐岩三轴蠕变实验,对此模型进行了验证.将此新模型的验证结果和西原正夫模型进行了对比研究.结果表明,此模型能够更好地模拟岩石蠕变的全过程,尤其是加速蠕变.

指出了岩石穿透斜裂纹在单轴压缩条件下,可将斜裂纹转化为Ⅱ型裂纹扩展问题.裂纹扩展主要有张拉破坏和剪切破坏两种类型,诸多实验表明裂纹的初始角度对裂纹的扩展特征有显著的影响.运用最大周向拉应力准则求得的理论起裂角与时的起裂角较为吻合,并且扩展的趋势也十分符合,表明为张拉破坏.但该准则不符合时的扩展情况,通过摩尔库伦准则得到的理论起裂角能较好的吻合.裂纹起裂模式受初始裂纹角影响,大角度表现为张拉破裂,小角度表现为剪切破裂.

对岩盐进行了单轴和三轴蠕变试验研究,试验中考虑轴压和围压对蠕变的影响.试验结果表明,随着围压的增大,盐岩的抗压强度增大;岩盐蠕变存在一定的应力阈值,低于此阈值不会发生明显蠕变现象;当围压一定时,轴压越大,岩盐完成蠕变三个阶段需要的时间越短,稳定蠕变率越大,达到破坏时变形越大;通过记录岩盐破坏过程的声发射现象,发现在应力峰值阶段声发射现象最强烈,声发射现象反映了岩盐的微观裂纹破坏.

Based on the analysis of the deformation field caused by elliptic crack embedded in infinite isotropic elastic matrix, the additional compliance tensor induced by a single opening/closed elliptic microcrack in a representative volume element and its growth is deduced, respectively. Considering the deformation of microcracks system, a macro-micro damage model for brittle rocks under arbitrary loadings is obtained by making use of statistical mechanics and a probability density function. The effect of elliptic ratio on material damage is investigated, and it is shown that the material damage increases with elliptic ratio, and the dependence of material damage on elliptic ratio increases with loading force. The tests of uniaxial tension for concrete and uniaxial compression for granite are simulated by this model, and good agreement is achieved between the calculated and experimental results.

基于无限大体深埋平片状椭圆形裂纹的变形场及其扩展条件,分别推导了脆性岩石材料内部具有任意空间取向的单个张开型或闭合型椭圆形微裂纹及其扩展引起的附加柔度张量；考虑微裂纹系统对材料变形的影响,引入了概率密度函数,得到了任意应力状态下脆性岩石材料的宏细观损伤模型；分析了椭圆形微裂纹的短长轴比率对材料损伤的影响.计算结果显示:材料损伤随着短长轴比率的增大而增大,短长轴比率对材料损伤的影响会随着载荷的增大而提高.将本文模型应用于混凝土的单轴拉伸和花岗岩的单轴压缩,结果表明本文模型能够对实验现象给予很好地解释.

已有的不同类型落锤撕裂实验数据表明，高钢级管线钢的单位断裂能和裂尖张开角依赖于断裂速度。本文进一步确定了其依赖关系是由断裂韧性而非试件几何差异所引起，并且定量分析了基于断裂准则所定义的断裂韧性与断裂速度之间的关系。利用所提出的黏结本构法则分别对X80管线钢标准试件和修正试件的落锤撕裂实验进行了三维有限元模拟，并将有限元结果与实验结果进行了对比。结果表明：有限元计算的加载曲线、断裂速度、裂尖张开角与对应的实验结果吻合较好，故本文提出的黏结本构法则能较好地应用于X80管线钢的动态断裂分析；标准试件的断裂韧性高于修正试件的断裂韧性，而标准试件的断裂速度则低于修正试件的断裂速度；七次有限元计算结果都表明断裂韧性随稳态断裂速度的增大而减小，且二者的关系可以由本文提出的自然指数函数进行描述。

Rapid development of China's economy demands for more mineral resources. At the same time, a vast quantity of mine tailings, as the waste byproduct of mining and mineral processing, is being produced in huge proportions. Tailings impoundments play an important role in the practical surface disposal of these large quantities of mining waste. Historically, tailings were relatively small in quantity and had no commercial value, thus little attention was paid to their disposal. The tailings were preferably discharged near the mines and few tailings storage facilities were constructed in mainland China. This situation has significantly changed since 2000, because the Chinese economy is growing rapidly and Chinese regulations and legislation require that tailings disposal systems must be ready before the mining operation begins. Consequently, data up to 2008 shows that more than 12 000 tailings storage facilities have been built in China. This paper reviews the history of tailings disposal in China, discusses three cases of tailings dam failures and explores failure mechanisms, and the procedures commonly used in China for planning, design, construction and management of tailings impoundments. This paper also discusses the current situation, shortcomings and key weaknesses, as well as future development trends for tailings storage facilities in China.

The stability of both natural and cut slopes in mountainous areas is a great challenge to highway constructions and operations. This paper presents a successful case study of stability analyses and protection treatments for high-steep cut soil slopes in an ancient landslide zone which was located at Km12+700 to Km15+000 along the Tehran–Chalus highway. This report has three parts. First, geotechnical investigations of in situ direct shear test, SPT tests and laboratory tests were implemented to get the subsurface profiles and the mechanical properties of the soil mass. Second, finite difference analysis was carried out to evaluate the stability of both the natural and cut slopes. Minimum safety factors and potential failure modes of cut slopes were obtained under both static and dynamic conditions. These results indicated that the ancient landslide could not be reactivated under the present climatic and morphological conditions, but there were some potential shallow failures in some cut soil slopes (failure actually occurred during excavation). Protection treatments and reinforcements were thus necessary. Third, the stability of the cut slopes was re-assessed by simplified Bishop limit equilibrium analysis (using Slide 5.0). Some potential failure zones were designed to be protected by back-anchored concrete retaining wall at the slope toe, rock bolts and frame beams on the slope face and planting grass on the slope face. Numerical analysis indicated that these protection measures could stabilize this remedial slope. These practical experiences may be of benefit for similar highway construction projects.

Taking the Wenzhuang tailings reservoir as project background, through indoor stacking model tests, the change law of saturation line and particle size distribution are obtained. Based on these results, a mathematical model of fluid-solid coupling in porous media is established; and by using the software of ABAQUS, a planar model of finite elements is established; and through finite element analysis, the stress field, deformation field as well as pore water pressure field in the dam are obtained. The results of model test and numerical simulation can provide instructor for the design, construction and safe production of tailings reservoirs.

Making use of irreversible thermodynamics with internal variables and the concept of continuum damage mechanics, an elastic-viscoplastic damage constitutive model is proposed by introducing a generalized time defined in the space of irreversible strain and Newtonian time. It can take into account the anisotropic nature of the micro-defects in rock, such as anisotropic evolution and unilateral effect of damage. It can also take into account the effect of hydrostatic pressure and temperature, and the interaction between irreversible deviatoric and volumetric deformation, for instance, the shear compaction and shear dilatation at different confining pressures and different phases of deformation. The corresponding numerical algorithm is developed, and the creep and damage of claystone are analyzed. The computed results agree well with the experimental observation.

基于不可逆热力学,采用内变量刻划岩石材料的不可逆变形历史,引入四阶损伤张量,建立了盐岩的蠕变损伤本构模型,对盐岩在复杂应力条件下的蠕变行为进行了描述,与实验结果比较表明该模型能较好的描述盐岩不同阶段的蠕变行为及其主要因素对盐岩蠕变特性的影响。