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101.
The direct simple shear (DSS) device is one of the commonly used laboratory element testing tools to characterize the shear behaviour of soil. The interpretation of results from an element test requires understanding of the degree of stress and strain non-uniformities in a given test specimen. So far, studies on stress and strain non-uniformities in the DSS test have been conducted using direct boundary measurements of stresses in laboratory specimens supported by a continuum based analytical approach. Discrete element modelling now provides a means of modelling the soil behaviour in a realistic manner using a particulate approach. Accordingly, the performance of a DSS specimen was modelled using discrete element modelling with emphasis on assessing stress and strain non-uniformities in the specimen during shearing. The approach allowed for the numerical determination of stresses not only at the boundaries, but also within the DSS specimen. It was shown that mobilised stress ratio distribution throughout the shearing phase for the majority of specimen volume at locations near the central planes parallel and perpendicular to the direction of shearing is fairly uniform. Finally, it was noted that the potential for particle slippage at locations near the specimen centre can result in non-uniform shear strain distributions. 相似文献
102.
Luminescence sensitivities of quartz grains from eolian deposits in northern China and their implications for provenance 总被引:2,自引:0,他引:2
The thermoluminescence (TL) and optically stimulated luminescence (OSL) sensitivities of quartz grains from deserts and loess–red clay sequences are used to trace eolian provenances in northern China. Our results indicate that the 110°C TL peak and OSL sensitivities of quartz grains show differences among Chinese deserts, which can be subdivided into four groups according to the spatial variations of luminescence sensitivities. Such differences are related mostly to the regional difference in rock types of mountains surrounding or adjacent to the deserts. We also examine the possible provenance changes between the Quaternary loess and the Tertiary eolian red clay, and the results indicate that the luminescence sensitivity of Tertiary red clay is higher than that of Quaternary loess (L1, L15, and L33), implying source materials of the eolian deposits changed relative to those of the Quaternary. 相似文献
103.
ATLAS III in situ heating test in boom clay: Field data,observation and interpretation 总被引:1,自引:0,他引:1
The ATLAS III small scale in situ heating test aimed at assessing the thermo-hydro-mechanical (THM) effects on the Boom clay of the significant temperature gradients generated in this host rock as a consequence of the geological disposal of radioactive, heat-emitting wastes. This paper presents data on temperature, pore water pressure and total stress measured during the experiment and highlights several interesting observations regarding the thermal anisotropy and THM coupling in the Boom clay. The test has a simple geometry and well defined boundary conditions, which facilitates the comparison between measurement and numerical modeling studies. These studies included three dimensional coupled THM modeling of the test. The good agreement between measurement and numerical modeling of temperature and pore water pressure yields a set of THM parameters and confirms the thermo-mechanical anisotropy of the Boom clay. 相似文献
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将全球分为15个研究区,用1900~2009年MW≥7.0地震目录,统计分析了各区大地震与月球交点运动周期的关系,得出15个研究区中有10个区,大地震存在统计意义上的18.6 a周期:活跃段为12.4 a,平静段为6.2 a;环太平洋地震带北、南、西、东4大区的大地震,不仅有这样的周期,而且其地震活跃段的时间存在一定规律.用第6个18.6 a(1991~2009年)期间的大地震,检验据前5个18.6 a(1900~1990年)地震目录所得18.6 a 周期的稳定性和实用性,发现有这种周期的地区多数的周期性是稳定的.大地震18.6 a周期的可能成因有: (1)18.6 a潮波通过调制日潮和半日潮调制大地震; (2)上地幔内流体的潮汐(地内潮)作用; (3)18.6 a潮波通过影响地球自转变化调制大地震. 相似文献
109.
This paper summarizes the relevant results of the design, construction, testing, and implementation of a nominal 120 kN magnetorheological damper developed to control a free‐plan tall building in Santiago, Chile, equipped with two 160‐ton tuned masses. Cyclic as well as hybrid simulation tests were performed on the prototype damper. Global building responses using measured MR properties showed good correlation with analytical estimations. Also, a proposed physical controller for the MR damper was validated through hybrid and building pull‐back tests. Its performance is essentially equivalent to that of an LQR controller, but the information needed in its implementation is considerably less. Pull‐back tests of 10 cm amplitude were performed on one mass along the flexible edge of the building and its response controlled using the passive and controlled modes of the MR damper. The MR damper was capable of controlling the TM displacements very effectively, as well as the simulated building response for different ground motions and harmonic excitation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
110.
Because a conventional isolation system with constant isolation frequency is usually a long‐period dynamic system, its seismic response is likely to be amplified in earthquakes with strong long‐period wave components, such as near‐fault ground motions. Seismic isolators with variable mechanical properties may provide a promising solution to alleviate this problem. To this end, in this work sliding isolators with variable curvature (SIVC) were studied experimentally. An SIVC isolator is similar to a friction pendulum system (FPS) isolator, except that its sliding surface has variable curvature rather being spherical. As a result, the SIVC's isolation stiffness that is proportional to the curvature becomes a function of the isolator displacement. By appropriately designing the geometry of the sliding surface, the SIVC is able to possess favorable hysteretic behavior. In order to prove the applicability of the SIVC concept, several prototype SIVC isolators, whose sliding surfaces are defined by a sixth‐order polynomial function, were fabricated and tested in this study. A cyclic element test on the prototype SIVC isolators and a shaking table test on an SIVC isolated steel frame were all conducted. The results of both tests have verified that the prototype SIVC isolators do indeed have the hysteretic property of variable stiffness as prescribed by the derived formulas in this study. Moreover, it is also demonstrated that the proposed SIVC is able to effectively reduce the isolator drift in a near‐fault earthquake with strong long‐period components, as compared with that of an FPS system with the same friction coefficient. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献