桩端下有软弱下卧层的群桩沉降分析

群桩沉降由桩身压缩和桩端沉降组成。本文采用桩身线弹性的假定计算单桩桩身压缩,用单桩的桩身压缩近似代替群桩桩身压缩,并用承台下的平均附加应力乘以桩端荷载传递系数后作为桩端的附加应力,推出了桩端下有软弱下卧层的群桩沉降计算方法,同时与其他计算方法和工程实测值进行了比较。     

自动制图综合中的线目标位移模型

数字地图制图环境下的自动综合是一个国际性的难题,其中地图要素的关系处理又是自动综合中的重点和难点之一,位移操作是关系处理的一个重要方法.本文以道路网的目标变形位移运用弹性力学思想进行理论和方法上的探讨,实现空间目标冲突的探测,进行目标的受力分析,运用平面杆件弹性体的受力变形模型,得到目标的位移量.该方法顾及目标间的空间关系,运用优化方法解决和控制位移的传播.     

武威-天祝-庄浪河NNW向断裂分段及变形特征

在野外专题考察、大比例尺活断层地质填图、高精度地质剖面及阶地剖面实测的基础上,较系统地讨论了武威－ 天祝－ 庄浪河ＮＮＷ 向断裂的活动时代、变形方式及分段特征。结果表明： 该断裂带是一条典型的全新世活动断裂,整个断裂可分为不同几何结构、不同构造类型、不同变形特征的南、中、北三个断层段。其中北段和中段为隐伏断层,发育有第四纪活动褶皱和１９２７ 年古浪８ 级地震破裂带;南段断裂呈弧形几何形态展布,显示了逆断层构造面的基本特征     

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牡丹江地震台形变数据快速转换软件

采用VB6.0编制形变数据快速转换软件,可以将epd格式的形变数据转换成Mapsis所要求的格式,便于研究人员使用.牡丹江地震台形变数据快速转换软件已在牡丹江地震台调试通过,使用效果较好,便于推广应用.     

Soil bentonite wall protects foundation from thrust faulting: analyses and experiment

When seismic thrust faults emerge on the ground surface,they are particularly damaging to buildings,bridges and lifelines that lie on the rupture path.To protect a structure founded on a rigid raft,a thick diaphragm-type soil bentonite wall(SBW) is installed in front of and near the foundation,at sufficient depth to intercept the propagating fault rupture.Extensive numerical analyses,verified against reduced–scale(1 g) split box physical model tests,reveal that such a wall,thanks to its high deformability and low shear resistance,"absorbs" the compressive thrust of the fault and forces the rupture to deviate upwards along its length.As a consequence,the foundation is left essentially intact.The effectiveness of SBW is demonstrated to depend on the exact location of the emerging fault and the magnitude of the fault offset.When the latter is large,the unprotected foundation experiences intolerable rigid-body rotation even if the foundation structural distress is not substantial.     

Analytical and experimental investigations on seismic performance of exterior beam–column subassemblages of existing RC‐framed building

Seismic performance of exterior beam–column subassemblages of reinforced concrete structure designed and detailed on the basis of the provisions of Eurocode and Indian Standards at different stages of their evolution is evaluated. Performance of the subassemblages designed and detailed according to the three different stages of codal evolution (gravity load design, ‘Nonductile’, and ‘Ductile’) is evaluated through analytical formulations and experimental investigations. In the ‘NonDuctile’ specimens, it has been observed that the shear distortion and degradation in stiffness and strength are significantly high. Performance of the ‘Ductile’ specimens based on Eurocode and Indian Standards is almost similar in terms of strength and stiffness degradation. Nevertheless, the specimen designed on the basis of Indian Standard shows higher energy dissipation at a given drift ratio. In the analytical study, shear and flexural failure of members of subassemblage and shear failure of the joint are considered as possible modes of failure of the beam–column subassemblage. For evaluating the shear strength of the joint region, a soften strut‐and‐tie model is used. Analytically obtained strengths based on the failure criteria of different components of the specimens have been first validated with experimental results and then used to determine the strength of the specimens. The investigation could indicate even the mode of failure at local level. It is utmost important to mention here that even the ductile specimens dissipate most of the energy through the development of damage in the joint region, which is neither desirable nor safe for the stability of whole structure. Copyright © 2013 John Wiley & Sons, Ltd.     

Migration of volatile organic contaminations (VOCs) through a deforming clay liner

A fully coupled thermal–hydraulic–mechanical–chemical (THMC) model was proposed to describe the migration of volatile organic contaminations (VOCs) in unsaturated landfill liners. The vertical soil stress, capillary pressure, air pressure, temperature increase, and solute concentration were selected as the primary variables. Finite deformations were described using Lagrangian coordinates. Non-isothermal moisture transport was found to be dependent on both the temperature gradient and the concentration of the VOCs. The VOCs were assumed to exist and be transported in three phases in the soil: solid, liquid, and gas. An illustrative example of an unsaturated landfill with a compacted clay liner was presented. For the case considered, the transport of gas phase VOCs was found to dominate the migration progress. Moreover, the temperature gradient can accelerate the breakthrough of VOCs in an unsaturated liner, while the mechanical consolidation slowed down the motion of the VOCs.     

A theory for the evolution of wind-generated gravity-wave spectra due to dissipation

Abstract

In Naeser (1979), later denoted N, it was shown that a frequency shift of a wave spectrum had to be expected as a result of dissipation of energy and conservation of spin of the waves. While time-dependency was treated in N, mainly space-dependency is treated here. In order to do this, the velocity of the spin of the waves is calculated. It is shown that this can be made equal to the group velocity by a second order coordinate transformation. In the limits of deep and shallow water the transformation becomes the identity, and leaves the Stokes drift at its usual value if the moment point is located at the mean water level.

By supposing that the dissipation is proportional to the molecular dissipation, and that the entire wind-wave interaction takes place at extremely high frequencies and at a constant rate, it is shown that the energy density at the high frequency slope of a fetch-dependent spectrum is inversely proportional to the fifth power of the frequency, while a spectrum which is only a function of the time for which the wind has blown is inversely proportional to the fourth power. The theory is compared with observations which it fits within the accuracy of the method. It is also compared with existing theories and reasons for the discrepancies are pointed out.     

砂土液化大变形本构模型的三维化及其数值实现

基于砂土液化大变形机理和适用于二维条件的边界面弹塑性本构模型,发展了符合三维应力空间中边界面和剪胀面上的应力映射规则,建立了三维应力空间中砂土液化大变形本构模型.针对模型特点采用半显式的Cutting Plane算法进行应力积分,并采用Pegasus求根算法根据映射规则计算边界面上的应力映射点,在OpenSees开源有限元平台上实现了三维模型的数值化.结合完全耦合的u-p格式有限元单元,对饱和砂土不排水循环扭剪试验进行了模拟,并进行了一个真三维倾斜地基的动力反应分析.计算结果表明模型和所采用的数值算法具有很好的模拟和分析三维条件下砂土液化后大变形的能力.