Rocking response of flexible circular foundations on layered media

The analysis of the response of a flexible circular foundation on layered media due to an arbitrarily distributed vertical loading is presented. The analysis is based on the ‘ring method’ approach, i.e. discretization of the foundation in a set of concentric rings. The arbitrarily distributed loading is expanded in the circumferential direction in a Fourier series. The influence coefficient matrix of soil for each element of the series is evaluated utilizing the stiffness matrix approach. The stiffness matrix of the foundation is obtained from the finite difference energy method approach. Numerical examples illustrate the influence of several soil-foundation parameters on the rocking response of a foundation. Results are presented in terms of displacement and soil reaction distributions and impedance functions point to significantly different responses of flexible and rigid foundations.     

兴文世界地质公园的旅游循环经济模式探讨

随着旅游经济的飞速发展,旅游环境问题日趋严重。本文将循环经济的新理念引入到兴文世界地质公园的旅游中,可构建旅游循环经济的新型发展模式。在兴文旅游循环经济中形成三大循环:旅游小循环——四大景区内部的旅游资源的循环利用;旅游中循环——旅游业与其他产业部门之间的循环,组织生态产业链联结不同的产业部门,形成共享资源和互换副产品的产业组合;旅游大循环——整个社会的循环,大力发展绿色消费市场和资源回收产业,完成"旅游资源——旅游产品——旅游再生资源"的闭合环路。这三种旅游循环模式的整合使整个兴文县经济、社会及环境相互协调,从而实现旅游资源的循环利用和旅游环境的可持续发展。     

Undrained lower bound solutions for end bearing capacity of shallow circular piles in non-homogeneous and anisotropic clays

The undrained bearing capacity of shallow circular piles in non-homogeneous and anisotropic clay is investigated by the lower bound (LB) finite element limit analysis (FELA) under two-dimensional (2D) axisymmetric condition using second-order cone programming, and the new solution of the problem is presented. Modified from the isotropic von Mises yield criterion, a cross-anisotropic undrained strength criterion of clays under the axisymmetric state of stress requiring three input shear strengths in triaxial compression, direct simple shear, and triaxial extension is employed in the 2D axisymmetric LB FELA. Parametric studies on the effects of pile embedment ratio, dimensionless strength gradient, anisotropic strength ratio, and pile roughness are investigated extensively, while the predicted failure mechanisms associated with these parameters are discussed and compared. Numerical results of undrained end bearing capacity of shallow circular piles are summarized in the form of design tables that are useful for design practice and represent a new contribution to the field of pile capacity considering the combined effects of undrained strength non-homogeneity and anisotropy.     

基于环形扫面测量的三维直流电阻率法任意各向异性模型响应特征

高精度地下任意各向异性介质电性分布特征识别是当前的热门研究课题。本文以国内外前人工作为基础,基于非结构化网格,利用基于梯度恢复的后验误差估计指导网格自适应细化过程,实现了直流电阻率法三维有限元数值模拟。通过与一维模型半解析解的对比,验证了本文算法的有效性。考虑到电各向异性介质在观测中存在视电阻率反常现象,本文采用了环形扫面测量方法。通过对几种典型各向异性模型的模拟分析,得到了相应的各向异性影响规律和识别特征,各向异性主轴电阻率之间的比值大小决定了椭圆型视电阻率极性曲线长轴与短轴的比值大小,主轴电阻率的旋转方向会改变视电阻率极性曲线的形状。本文的算法研究及数值模拟技术可为直流电法数据精细处理和解释提供技术支撑。     

Prediction of streamwise flow-induced vibration of a circular cylinder in the first instability range

The streamwise flow-induced vibration of a circular cylinder with symmetric vortex shedding in the first instability range is investigated, and a wake oscillator model for the dynamic response prediction is proposed. An approach is applied to calibrate the empirical parameters in the present model; the numerical and experimental results are compared to validate the proposed model. It can be found that the present prediction model is accurate and sufficiently simple to be easily applied in practice.     

基于摩尔-库仑模型的非线性本构模型的开发及其在应变局部化中的应用

以FLAC中的Mohr-Coulomb（M-C）本构模型为基础,在C++环境下实现了考虑拉伸截断的非线性本构模型的二次开发。针对应力及位移的分布规律,将理想弹塑性的Hoek-Brown（H-B）本构模型、M-C本构模型及自定义本构模型的数值解及H-B本构模型的理论解进行了比较,验证了自定义本构模型的正确性。采用弹-脆-塑性的自定义本构模型,以先加载,后挖洞的方式模拟了圆形巷道围岩的应变局部化过程,在计算模型的边界条件对称及均质本构参数的条件下,模拟出了4个对称的V型坑,模拟结果与静水压力条件下岩爆的现场观测及试验结果吻合,而采用接近脆性的H-B应变软化模型所得结果的对称性较差     

The Circular Economic Development Level of Beijing’s Service Sector Based on AHP Modeling

As a mega-city constrained by resources and the environment, Beijing has developed a leading service sector, and it is necessary to evaluate the service sector circular economy in this major global city. Here, we establish an indicator system including internal subsystem (economic production, resources consumption, waste emissions, and waste recycling), external subsystem (industry correlation) and mutualistic subsystem (society development), and use AHP modeling to evaluate the period from 2000 to 2013. We found that the development of the service sector circular economy in Beijing experienced an increase from 2000 to 2008, then a decrease from 2009 to 2013. This change mainly resulted from the decrease in Beijing’s GDP following the international financial crisis in 2008. The internal subsystem greatly influences the service sector circular economy:synthetic weight of economic production, resource consumption, waste emissions and waste recycling was 0.367,0.136,0.136 and 0.075, respectively. Within the external subsystem, industrial correlation has a weak connection with Beijing’s service sector circular economy with asynthetic weight of 0.143, this result illustrates that the development of the service sector circular economy has an intimate relationship with other cities or provinces around Beijing, such as Tianjin and Hebei. As are presentative of the mutualistic subsystem, society development has a positive nexus with the service sector circular economy with asynthetic weight of 0.143, proving that the development of the service sector circular economy can improve the service sector employment ratio in Beijing. We conclude with some suggestions on how to develop the service sector circular economy in Beijing.     

GIS中3维空间圆曲线的不确定性εσ模型

随着GIS向3维领域的不断发展,对3维空间元素的不确定性研究日趋重要.基于不确定性理论及概率统计理论,研究GIS中3维空间圆曲线的不确定性模型.首先建立3维空间圆曲线上任意点坐标的微分关系式,然后得到圆曲线上任意点坐标的方差, 进而获得3维空间圆曲线的εσ模型.实际算例表明,3维空间圆曲线误差分布呈现出"两端大,中间小"的趋势.     

圆形煤场中桩-网复合地基原体试验研究

在大型圆形煤场中采用桩-网复合地基是火电厂地基方案设计的新思路,该方案不仅要考虑地基土层的强度满足上部荷载的要求,还需要考虑堆载区内土体的变形对环基的影响。通过对圆形煤场中桩-网复合地基原体试验研究,介绍了在大面积堆载下如何进行桩、土及垫层中应力与应变的测试,设计了2套堆载与测试方案,在试验1区铺设了2层土工格栅,而在试验2区未铺设土工格栅。根据在2个试验区所获得的测试成果,研究了大面积堆载对堆载区内外土体变形的影响深度与范围,对比分析了不同高程处垫层与土体的竖向及侧向应力随深度的变化规律,结合堆载区中桩与边桩的桩身轴力变化,计算出上部桩侧土体对桩所产生的负摩阻力,并依据承台顶面附近测得的垫层与土层的应力,计算出桩土分担荷载的比例,以及桩土应力比的大小与变化规律。在此基础上得到土工格栅对大面积堆载区内外土体应变与应力的影响程度,从而可以为大型圆形煤场桩-网复合地基方案的设计与施工提供客观的技术参数与建议。