饱和块状混合回填土地基的一维固结分析

用块状渣土置换软弱地基和回填低洼谷地等是处置工程渣土的有效途径。为了分析饱和块状混合回填土地基的固结性状，运用混合物理论建立了其一维固结模型。首先，假定块状土固相和充填土固相之间满足等应变条件，获得了饱和块状混合回填土中各相应变与块状土孔隙变形和充填土孔隙变形的关系式。其次，在小应变条件下，根据自由能势函数方程建立了饱和块状混合回填土的一维线弹性本构方程，再结合达西定律和应力平衡方程获得了一维固结控制方程。再次，利用分离变量法得到一维固结解析解，通过退化本文模型与已有模型进行对比，验证了本文模型的正确性。最后，基于所得解析解，分析了充填土孔隙渗透系数、块状土孔隙渗透系数以及流体交换参数等因素对饱和块状混合回填土地基固结性状的影响。分析结果表明：充填土孔隙渗透系数对饱和块状混合回填土地基整体固结性状起主导作用；在固结初期，块状土超孔压会有一定程度的上升，且3个参数具有相似的作用机理。     

Electric field-assisted synthesis/sintering cerium oxide: 5 wt.% gadolinium oxide

Gadolinium oxide ceramic powders were mixed to cerium oxide ceramic powders, pressed to pellets, and sintered either at 1450 °C or applying 200 V cm⁻¹ electric field at 800 °C, 900 °C and 1000 °C. The structural phases and the microstructure of the sintered pellets were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The formation of substitutional solid solution was followed by monitoring the increase of the electrical conductivity by impedance spectroscopy and X-ray diffraction. The main results show that Joule heating due to the flow through the pellets of the electric current, which was produced by the application of the electric field, allows for promoting partial solid solution as well as partial sintering the ceria-gadolinia pellets. Moreover, grain growth that occurred in the high temperature sintered pellets was inhibited in the electric field-assisted synthesized/sintered pellets, being an alternative technique for producing cerium oxide-gadolinium oxide solid solutions.     

A thermal-aware VM consolidation mechanism with outage avoidance

Efficient energy and temperature management techniques are essential elements for operators of cloud data centers. Dynamic virtual machine (VM) consolidation using live migration techniques presents a great opportunity for cloud service providers to adaptively reduce energy consumption and optimize their resource utilization. In recent studies, power consumption readings of individual physical hosts were chosen as the main monitoring parameters in their allocation policies, whereas very few have considered host temperature, which has shown to have a negative impact on server reliability, as a migration criterion. In this work, a thermal-aware VM consolidation mechanism is proposed for resource allocation optimization and server reliability assurance. We consider the variability in host temperature as a migration criterion to avoid outage incidents via having better VM consolidations. Extensive simulation results obtained from CloudSim show the promising performance of the proposed mechanism in energy saving while reducing the number of server outage incidents due to fluctuations in host temperature.     

分级加载电压下考虑有效电势变化的软黏土电渗固结理论

分级加载电压技术能够有效延长电渗处理的时间,改善地基的处理效果并能有效降低能耗。在利用分级加载电压技术开展电渗试验时,随着土体的排水固结,土体各点的电势会发生明显的变化,这与现有的电渗固结理论假设土体各点电势保持不变有所差异。利用自主设计的电渗试验仪器开展了分级加载电压下的电渗室内试验,分析了电渗过程中土体有效电势变化的规律。基于该规律并结合Esrig固结理论建立了在阳极处不排水、阴极处排水条件下考虑土体有效电势变化的电渗固结理论,得到了分级加载电压条件下考虑土体有效电势变化的超静孔隙水压力和平均固结度的解析表达式。研究表明,在电压分级加载过程中,土体有效电势变化规律表现为随时间先基本保持不变,后呈抛物线状先增后减。通过试验案例验证了考虑土体有效电势变化所求得解析解的合理性,且该数值计算结果相较于Esrig数值计算结果,前者更加接近实测值,该固结方程的建立为后续分级加载电压技术的推广应用提供了理论依据,也为实际工程提供了参考。     

飞灰固结体在沥青混合料中应用研究

通过对新型固结剂固化飞灰生成的固结体研磨成微粉全部或部分替代矿粉作为沥青混合料进行试验探究。试验结果表明,当微粉替代矿粉时,混合料的物理性能、水稳定性及高温稳定性得到了提高,确定了微粉替代矿粉最佳替代率。微粉在沥青混合料中重金属的存在状态采用多级提取的方法进行分析,试验结果进一步证明了微粉中重金属在沥青混合料中的长期稳定性。为焚烧垃圾飞灰固化稳定化和资源化利用提供了一定的理论指导。     

Microstructural evolution and mechanical properties of a β-solidifying γ-TiAl alloy densified by spark plasma sintering

This study deals with the densification of a pre-alloyed Ti–44Al–6Nb–1Mo–0.2Y–0.1B (at.%) powder by spark plasma sintering (SPS). The powder was produced by a plasma rotating electrode process (PREP), and then SPS densified at temperatures between 1200 and 1320 °C. At SPS temperatures below 1240 °C, the α₂-dominated dendritic structure in the PREP powder particles disappeared and the fully dense microstructure mainly consisting of γ and B2 grains formed during SPS, but several original powder particle boundaries (OPBs) still remained. While sintered above 1240 °C, OPBs vanished entirely and an uniform duplex microstructure emerged. Furthermore, fully-lamellar (FL) microstructure with mean colony size smaller than 20 μm was produced via β-homogenization annealing. This FL microstructure renders a good tensile elongation of 1.25% and yield strength of 665 MPa at room temperature. However, instability of α₂/γ lamellar structures was induced by final stabilization annealing, resulting in sharp reduction of both room-temperature ductility and high-temperature strength.     

大新锰矿复杂空区群三维数值模型构建方法及胶结充填治理研究

矿山岩土工程数值分析中研究复杂空区群三维数值模型构建方法对空区治理具有现实意义。为精确分析矿山地下工程围岩移动和应力变化规律，特别是不同采矿方法形成的复杂空区的稳定性和矿柱应力变化，提出了3DMine-Surfer-Rhino-ANSYS-FLAC3D多软件联合建模方法，解决了复杂空区群三维数值模型构建和大数量小尺寸矿房矿柱网格剖分问题。以广西大新锰矿矿体开采为案例，构建了留矿法与房柱法形成的采空区的三维数值模型，模拟分析空区的稳定性和决策胶结充填治理方案。研究结果表明：（1）大新锰矿留矿法开采的空区部分顶柱有垮落风险；（2）房柱法开采的空区部分矿柱变形大，有塑性破坏；（3）对于胶结充填留矿法的空区，隔一充一充填方案治理效果更好，在治理初期地表沉降更小。     

Method for calculating horizontal drain induced non-linear and large strain degree of consolidation

Consolidating dredged clay slurries using a combination of vacuum pressure and prefabricated horizontal drains (PHDs) is widely used in practice. This is a large strain problem, but there is no existing large strain theory for PHD induced consolidation. A method with explicit equations has been proposed to consider both mechanical and geometrical non-linearities in analyzing PHD induced consolidation. The method considers stepwise variation of properties using imaginary time concept. An imaginary time is determined by the condition of continuity of degree of consolidation before and after changing the properties. Then the method was applied to analyze a large scale model test of vacuum consolidation with PHD. Two analyses were conducted. One considered both the mechanical and geometrical non-linearity (large strain), and another only considered mechanical non-linearity (small strain). The results of large strain analysis agree with the measured settlement curve and excess pore pressures well. While the small strain analysis under-estimated the rate of consolidation significantly. The results from this study indicate that for analyzing PHD induced consolidation of clay slurries considering the effect of large strain is important, and the proposed method can be a useful design tool.