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31.
Influence of Structural Non-Stationarity of Surface Roughness on Morphological Characterization and Mechanical Deformation of Rock Joints 总被引:2,自引:2,他引:0
N. Fardin 《Rock Mechanics and Rock Engineering》2008,41(2):267-297
Summary Structural non-stationarity of surface roughness affects accurate morphological characterization as well as mechanical behaviour
of rock joints at the laboratory scale using samples with a size below the stationarity threshold. In this paper, the effect
of structural non-stationarity of surface roughness is investigated by studying the scale dependence of surface roughness
and mechanical behaviour of rock joints. The results show that the structural non-stationarity mainly affects the accurate
characterization of the surface roughness of the fracture samples. It also controls the amount and location of the contact
areas during shear tests, which in turn affects the mechanical properties and asperity degradation of the samples. It is concluded
that for accurate determination of the morphological and mechanical properties of rock joints at laboratory and field scales,
samples with size equal to or larger than the stationarity threshold are required.
Author’s address: Nader Fardin, Rock Mechanics Group, Department of Mining Engineering, Faculty of Engineering, University
of Tehran, P.O. Box: 11365/4563, Tehran, Iran 相似文献
32.
Nonlinear Analysis of Local Site Effects on Seismic Ground Response in the Bam Earthquake 总被引:1,自引:0,他引:1
M. H. T. Rayhani M. H. El Naggar S. H. Tabatabaei 《Geotechnical and Geological Engineering》2008,26(1):91-100
The influence of local geologic and soil conditions on the intensity of ground shaking is addressed in this study. The amplification
of the ground motion due to local site effects resulted in severe damage to dwellings in the Bam area during the 2003 Bam
Earthquake. A unique set of strong motion acceleration recordings was obtained at the Bam accelerograph station. Although
the highest peak ground acceleration recorded was the vertical component (nearly 1 g), the longitudinal component (fault-parallel
motion) clearly had the largest maximum velocity as well as maximum ground displacement. Subsurface geotechnical and geophysical
(down-hole) data in two different sites have been obtained and used to estimate the local site condition on earthquake ground
motion in the area. The ground response analyses have been conducted considering the nonlinear behavior of the soil deposits
using both equivalent linear and nonlinear approaches. The fully nonlinear method embodied in FLAC was used to evaluate the
nonlinear soil properties on earthquake wave propagation through the soil layer, and compare with the response from the equivalent
linear approach. It is shown that thick alluvium deposits amplified the ground motion and resulted in significant damage in
residential buildings in the earthquake stricken region. The comparison of results indicated similar response spectra of the
motions for both equivalent and nonlinear analyses, showing peaks in the period range of 0.3–1.5 s. However, the amplification
levels of nonlinear analysis were less than the equivalent linear method especially in long periods. The observed response
spectra are shown to be above the NEHRP building code design requirements, especially at high frequencies. 相似文献
33.
鲁中南隆起区第四纪晚期断裂活动特征 总被引:6,自引:1,他引:6
根据野外调查,并综合前人的研究资料,对鲁中南地区第四纪晚期断裂活动进行了分析,研究表明,鲁中南隆起区第四纪断裂活动具有时空不均匀性,主要表现为第四纪时期断层活动强度变化和断裂活动的群集性以及第四纪晚期断裂活动段分布的局限性上。对于鲁中南地区而言,活动断层可以分为中更新世中期(500kaBP)至晚更新世初期(90kaBP)活断层和晚更新世中、晚期至全新世早期活断层两类;其中前一类(主要是中更新世断裂)断裂数量较多,分布较为广泛,而晚更新世晚期以来的活动断裂段的数量较少,分布较局限。它们对地震的控制能力不同,前者可控制5.5级左右的地震,而后一类可控制6-7级地震的发生。 相似文献
34.
AbstractThe ground vibrations during pile driving operation have a drastic potential to undermine the surrounding structures both in land and reclaimed land. Particularly, reclaimed land necessitates ample application of pile driving due to the weak land condition. To prevent the structural damage, attenuation of the ground vibrations to an allowable level through active isolation of circular open trench is the scope of this study. In this research, finite element simulations of continuous impact pile driving process from the ground surface was executed with particular attention to the pile-soil interaction, and thereby, the efficiency of open trench application in attenuation of the unsafe distance of different structures was surveyed using the vibration sensitivity degree. Regarding the crucial parameters of an open trench (depth, width, and location), it was concluded that a sufficient high depth can attenuate the unsafe distance up to 68%, the trench width variations are less effective, and an average pile-trench distance is the most efficient option. The excavation volume was also concluded as another crucial parameter in open trench design which takes all three parameters into account. The trench depth equal to the pile’s maximum critical depth of vibration was inferred for an optimum design. 相似文献
35.
提出一种基于BP神经网络的结构破损诊断方法,该方法以结构破损前后柔度的变化作为破损诊断网络输入,为了解决由于系统响应样本数据空间分布不均匀对网络收敛速度及网络诊断影响问题,对网络训练样本采用广义空间格点进行了交换,模拟算例及应用实例均表明,本文方法能准确诊断结构破损位置与破坏程度,是一种有效的结构破损诊断方法. 相似文献
36.
37.
Gao Yinli Yan Shuwang Wang Jinying
Graduate Student Tianjin University Tianjin
Professor Tianjin University Tianjin
Senior Engineer China Offshore Oil Engineering Co. 《中国海洋工程》1995,(1)
This paper introduces a stability design system of submarine pipelines. The system can provide a reasonable design procedure for users with reference to domestic and foreign methods and in the light of home engineering experience. 相似文献
38.
提出一种确定连续系统参数的时域方法。该方法利用方波输入和系统稳定性,离析出输出采样信号与结构参数的内在联系,推导出确定连续系统结构参数的算法.指出该算法与辨识方法相结合,可实现对含随机干扰的连续系统结构参数的估计. 相似文献
39.
Many innovative floating offshore structures have been proposed for cost effectiveness of oil and gas exploration and production in water depths exceeding one thousand meters in recent years. One such type of platform is the offshore floating Spar platform. The Spar platform is modelled as a rigid body with six degrees-of-freedom, connected to the sea floor by multi-component catenary mooring lines, which are attached to the Spar platform at the fairleads. The response dependent stiffness matrix consists of two parts (a) the hydrostatics provide restoring force in heave, roll and pitch, (b) the mooring lines provide the restoring force which are represented here by nonlinear horizontal springs. A unidirectional regular wave model is used for computing the incident wave kinematics by Airy’s wave theory and force by Morison’s equation. The response analysis is performed in time domain to solve the dynamic behavior of the moored Spar platform as an integrated system using the iterative incremental Newmark’s Beta approach. Numerical studies are conducted for sea state conditions with and without coupling of degrees-of-freedom. 相似文献
40.
筒型基础沉贯阻力估算方法 总被引:1,自引:0,他引:1
系统地总结国外有代表性工程实践对筒型基础沉贯阻力的研究 ,并将各种方法综合起来 ,提出了加权综合估算法 ,供今后的研究和工程实践参考 相似文献