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81.
82.
多道瞬态瑞雷波法在探测煤矿采空区中的应用 总被引:7,自引:0,他引:7
采空区探测是工程建筑和煤矿生产中亟待解决的问题。常规物探方法在对落后的“房—柱”式开采技术造成的面积较小、埋深较浅的采空区进行探测时存在漏报或误报的情况。根据采空区的地球物理特征,探讨多道瞬态瑞雷波技术的探测机理,并通过勘探实例阐述了该方法在浅层煤矿采空区探测中的实用性和有效性。 相似文献
83.
分析了造成波浪衰减几种力学机制,并针对不同模型海底底床下的波浪衰减,以及有限深底床和无限深底床的波浪衰减进行了计算比较,认为造成波浪衰减的力学机制直接和底床砂质的性质相关。 相似文献
84.
本文采用液压阻尼系统(HDS)控制立式圆柱钢制储罐的地震反应,建立了安装HDS储罐的力学分析模型,并进行了数值计算,从频域对安装HDS后储罐的地震响应进行了分析,研究了HDS的减震效果和HDS和HDS参数对储罐地震反应的影响。 相似文献
85.
IntroductionThe analysis of dynamic soil-structure interaction for important engineering project is still based on linear model (including equivalent linear model) with complex damping, and traditional frequency domain method (Lysmer, et al, 1975, 1981; DING, et al, 1999). Namely, first calculating frequency domain solution by Fourier transform, and then calculating time domain solution by Fourier inverse transform. The motion equation of a system in frequency domain is usually written as (… 相似文献
86.
87.
Oldřich Novotný L. V. Burlako T. A. Proskuryakova 《Studia Geophysica et Geodaetica》1996,40(2):167-177
Summary Dispersion relations for Love and Rayleigh waves in a layer on a half-space are modified by introducing quadratic slownesses instead of velocities. The advantages of this approach are demonstrated on analytical formulae for computing the group velocity. 相似文献
88.
A total of 11 earthquakes with 15 Rayleigh wave paths, recorded at 11 broadband digital PASSCAL seismometers installed in
the Tibet Plateau by the Sino-U.S. joint research group, were used to determine the phase velocity and attenuation coefficient
of surface waves in periods of 10–130 s. The average shear wave velocity and quality factor {ie271-1} structures in the crust
and upper mantle were obtained in this region. The result shows the average {ie271-2} is low and there exists a high attenuation
({ie271-3}=93–141) layer in the crust. The depth range of the low {ie271-4} value layer (16–42 km) is consistent with the
range of low velocity layer (21–51 km) in the crust. Below 63 km in the lower crust, {ie271-5} decreases with depth from 114
to 34 at depth of 180 km. The low shear wave velocity and low value of {ie271-6} at the same depth range in the crust indicate
that the rocks in the range is probably melted or partially melted. According to the shear wave velocity structure, the average
thickness of the crust is about 71 km and a clear velocity discontiniuty appears at the depth of 51 km. The low-velocity zone
(4. 26 km/s) at depth of 96–180 km may be corresponding to the asthenosphere.
Contribution No. 96A0047, Institute of Geophysics, SSB, China.
This study was supported by the National Natural Science Foundation of China. 相似文献
89.
Claudio Chiaruttini Stefano Grimaz Enrico Priolo 《Soil Dynamics and Earthquake Engineering》1996,15(2):75
A two-dimensional elastic Chebyshev spectral element method (SPEM) is used to model the seismic wavefield within a massive structure and in its vicinity. We consider 2-D models where a linear elastic structure, with quadrangular cross-section, resting on an elastic homogeneous half-space, is impinged upon by the waves generated by a surface impulse at some distance. The scattering of Rayleigh waves and the response of the structure are extensively analysed in a parametric way, varying size, mechanical parameters and shape of the load. Some of the models considered are representative of embankments and earth dams. The simulation shows that some models resonate, storing part of the incoming energy. With realistic parameters, the lowest resonance frequency is due to pure shear deformation and is controlled by the shear velocity and height of the load. Flexural modes are excited only at higher frequencies. The acceleration at the top of the structure may be five/seven times higher than at the base, depending on the mass of the structure. The gradual release of trapped energy produces a ground roll lasting several seconds after the wave front has passed. The ground-roll amplitude depends on the sturcture's mass and can be as large as 30% of the peak acceleration. Outside resonance conditions, the ground motion is almost unaffected by the presence of the artefact; the horizontal motion on top of it is nearly twice the motion at ground level. Similar results should be expected when the incident field is an upcoming shear wave. A qualitative discussion shows that the presence of anelastic attenuation in the embankment does not significantly alter the preceding conclusions, unless it is of very low values (e.g. Q < 15).The modelling results that we discuss indicate that the soil-structure interaction may substantially alter the ‘free-field’ ground motion. From a practical point of view, the main conclusions are: (1) careful analysis is necessary when interpreting seismic records collected in the vicinity of large artefacts; (2) seismic hazard at a site may depend on the presence of man-made structures such as embankments, dams, tall and massive buildings. 相似文献
90.