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41.
Priti Maheshwari P. K. Basudhar S. Chandra 《Geotechnical and Geological Engineering》2006,24(2):313-324
The paper describes a mechanical model for estimating the flexural response of a strip footing, supporting a column (imposing
a concentrated load), resting on a compacted granular bed overlying a reinforcement layer for example, geogrids, geomats etc.
below which lies a loose soil deposit. The footing is idealized as a beam and the reinforcing element is assumed to have finite
bending stiffness and negligible frictional resistance. The upper and lower soil layers are idealized by a series of linear
and discrete springs (Winkler springs) of different stiffness values. To find the response of such a model the governing differential
equations have been derived and expressed in a nondimensional form. A closed form analytical solution of the same has been
obtained subjected to appropriate boundary conditions. Using the present approach the resulting solution for a degenerated
case of a long beam is found to be identical to the same of Hetenyi (1946, Beams on elastic foundations, University of Michigan
press, Ann Arbor, MI). Parametric studies reveal that the ratio of flexural rigidity of upper and lower beam and the ratio
of stiffness of the upper and lower soil layers affect significantly the response of the foundation. 相似文献
42.
Substantial damage to water supply systems, including water delivery pipelines, water treatment plants, reservoirs, and water
storage tanks, was reported after the 1999 Chi–Chi Taiwan Earthquake. This paper first summarizes the damage survey and then
presents the results of seismic fragility analysis for underground pipelines. Construction blueprints of the water delivery
pipelines and repair work orders of 11 townships and cities in the disastrous area were digitized into a Geographical Information
System (GIS) for analysis and assessment. With the aid of the GIS system, we found that PVC pipes made up 86% of water delivery
pipelines while steel, cast iron, ductile iron, PE and others took the rest. Therefore, this paper focuses on the fragility
analysis of PVC pipes. Three different methods were applied to derive the fragility relations between the PVC water pipes
having nominal diameters (approximately inner diameters) greater than or equal to 65 mm and earthquake intensity parameters
such as peak ground acceleration and peak ground velocity. The results were then examined with those of other countries. The
discrepancy between our results and the empirical equation used by HAZUS, an earthquake loss estimation software developed
by the Federal Emergency Management Agency was not significant. 相似文献
43.
The area of Serravalle, sited in the northern part of the town of Vittorio Veneto (TV), NE Italy, has been the target of a
seismic microzonation campaign. 10 seismic stations have been deployed for a 7 months period to record in continuous mode.
Three stations were installed on bedrock outcrops and seven on sedimentary sites with variable cover thickness. Spectral analyses
have been performed on the collected data-set using the Generalized Inversion Technique (GIT, e.g. Andrews, 1986). In particular,
spectral ratios have been calculated for each station relatively to the average of the three reference, bedrock sites. The
spectral ratios provide quantitative estimates of the seismic motion amplifications which occur in each of the monitored sites.
Two sites show high values of amplification, 5 times larger than signal amplitude at the reference sites, in correspondence
of well discernible peak frequencies of 5 Hz. Results for the other stations show smaller amounts of site amplification spreading
over a broad range of frequencies. Sites where the highest amplifications were recorded all lie on the left bank of the Meschio
River and in areas farther away from its outlet into the plain correlating with the presence of thick layers of Quaternary
deposits. 相似文献
44.
45.
Ground motion scaling in the Marmara region, Turkey 总被引:1,自引:0,他引:1
A. Akinci L. Malagnini R. B. Herrmann R. Gok M. B. Sørensen 《Geophysical Journal International》2006,166(2):635-651
46.
A general tomographic technique is designed in order (i) to operate in anisotropic media; (ii) to account for the uneven seismic sampling and (iii) to handle massive data sets in a reasonable computing time. One modus operandi to compute a 3-D body wave velocity model relies on surface wave phase velocity measurements. An intermediate step, shared by other approaches, consists in translating, for each period of a given mode branch, the phase velocities integrated along ray paths into local velocity perturbations. To this end, we develop a method, which accounts for the azimuthal anisotropy in its comprehensive form. The weakly non-linear forward problem allows to use a conjugate gradient optimization. The Earth's surface is regularly discretized and the partial derivatives are assigned to the individual grid points. Possible lack of lateral resolution, due to the inescapable uneven ray path coverage, is taken into account through the a priori covariances on parameters with laterally variable correlation lengths. This method allows to efficiently separate the 2ψ and the 4ψ anisotropic effects from the isotropic perturbations. Fundamental mode and overtone phase velocity maps, derived with real Rayleigh wave data sets, are presented and compared with previous maps. The isotropic models concur well with the results of Trampert & Woodhouse. Large 4ψ heterogeneities are located in the tectonically active regions and over the continental lithospheres such as North America, Antarctica or Australia. At various periods, a significant 4ψ signature is correlated with the Hawaii hotspot track. Finally, concurring with the conclusions of Trampert & Woodhouse, our phase velocity maps show that Rayleigh wave data sets do need both 2ψ and 4ψ anisotropic terms. 相似文献
47.
江西省宜春城区地面塌陷特征及防治建议 总被引:2,自引:0,他引:2
宜春城区属岗阜低丘地形,分布石炭系-二叠系覆盖型及裸露型碳酸盐岩,占城区面积近70%。浅部岩溶发育,覆盖层厚度一般小于20m,土洞较多,基岩面起伏大,第四系岩性结构复杂,地下水埋藏浅。由于抽采地下水及建筑施工振动等人为因素影响,诱发地面塌陷12处,造成重大经济损失。在城市规划功能布局时应充分考虑地面塌陷的易发程度及场地建设适宜性;应限制诱发塌陷因素的强度,在易发区须严格控制地下水开采,严禁新建开采井;塌陷治理的主要方法有填堵、跨越、灌注、深基础控制抽排水强度、及其它综合治理或避让方法,同时做好灾害的监测预报工作。 相似文献
48.
采用文件映射降低大数据量探地雷达(GPR)数据显示对计算机内存的需求,同时使GPR数据可以当作一维数组进行数据处理,方便对数据的随机、实时访问;应用直接写位图、视区分割的成图方案,实现对GPR数据的实时显示;通过位图调色板实现GPR数据调色板,灵活应用该技术可使本来需要对原始数据进行大量运算的算法通过调整调色板实现,提高了GPR数据处理的速度。 相似文献
49.
John R. Greenwood Joanne E. Norris Jo Wint 《Geotechnical and Geological Engineering》2006,24(3):467-481
The procedure for geotechnical site investigation is well established but little attention is currently given to investigating
the potential of vegetation to assist with ground stability. This paper describes how routine investigation procedures may
be adapted to consider the effects of the vegetation. It is recommended that the major part of the vegetation investigation
is carried out, at relatively low cost, during the preliminary (desk) study phase of the investigation when there is maximum
flexibility to take account of findings in the proposed design and construction. The techniques available for investigation
of the effects of vegetation are reviewed and references provided for further consideration. As for general geotechnical investigation
work, it is important that a balance of effort is maintained in the vegetation investigation between (a) site characterisation
(defining and identifying the existing and proposed vegetation to suit the site and ground conditions), (b) testing (in-situ and laboratory testing of the vegetation and root systems to provide design parameters) and (c) modelling (to analyse the
vegetation effects). 相似文献
50.