Analysis of a rigid footing lying on three-layered soil using the finite difference method     

Priti Maheshwari  M. R. Madhav 《Geotechnical and Geological Engineering》2006,24(4):851-869

A numerical procedure is described for the analysis of the vertical deformation and the stress distribution of the strip footings on layered soil media. Three layers of soil with different stiffness are considered with the middle soil layer the thinnest and most stiff layer. The soil media is discretized and using the theory of elasticity, the governing differential equations are obtained in terms of vertical and horizontal displacements. These equations along with appropriate boundary and continuity conditions are solved by using the finite difference method. The vertical and horizontal displacements, strains and stresses are found at various nodes in the soil media. Parametric studies are carried out to study the effect of the placement depth of the middle soil layer, the relative ratios of the moduli of deformation of the soil layers on the vertical displacement of the footing and the vertical stress distribution. These studies reveal that the middle thin but very stiff layer acts like a plate and redistributes the stresses on the lower soft soil layer uniformly. The displacement on the top and bottom of the middle soil layer is almost the same showing that the compression of the middle layer is negligible as it is very stiff.  相似文献   

An approximate projection of availability of the fresh groundwater resources in the South West district of NCT Delhi, India: a case study     

Shashank Shekhar 《Hydrogeology Journal》2006,14(7):1330-1338

The future availability and sustainability of fresh groundwater resources in the South West district of the national capital territory (NCT) Delhi, India, have been projected. Due to a rapid decline in groundwater level and quality, the district has been required by the Government of India to regulate development of groundwater resources. Shallow groundwater is mostly saline and water resources in the area are limited. The methodology applied here involves microzonation of the district in terms of thickness of fresh groundwater and then quantification of present and future availability of freshwater in different freshwater zones, including tentative timescales. The calculation method has been aided by data on historic trends in water level at representative groundwater monitoring stations, located either in fresh groundwater zones or near to them. It is estimated that the presently available 481 million m³ of resources will be reduced to 374 million m³ by year 2007 and to 303 million m³ by the year 2012, and by the year 2022 the district will have only 176 million m³ of available fresh groundwater resources.  相似文献   

Modeling of Beams on Reinforced Granular Beds     

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   

Damage Survey of Water Supply Systems and Fragility Curve of PVC Water Pipelines in the Chi–Chi Taiwan Earthquake     

Ban-Jwu Shih  Che-Hao Chang 《Natural Hazards》2006,37(1-2):71-85

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   

Site Effects Study in the Serravalle Village (NE Italy) by Means of Spectral Ratios Analyses Relatively to Multiple Reference Sites     

Andrea Restivo  Carla Barnaba  Alberto Michelini 《Natural Hazards》2006,39(1):31-49

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   

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

  相似文献   

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  

刘细元  马振兴  杨永革  吕少俊  张永忠  陶木金 《中国地质灾害与防治学报》2006,17(2):89-94

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   

探地雷达数据可视化方法     

张志勇  刘艳阳  陈越  刘庆成 《华东地质学院学报》2006,29(4):353-356

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   

Site Investigation for the Effects of Vegetation on Ground Stability     

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   

SPOT5影像严格几何纠正方法研究   总被引：8，自引：1，他引：8  

宁晓刚  张晓东  胡进刚 《测绘信息与工程》2005,30(1):43-45

根据SPOT卫星的成像原理和特点,讨论了对SPOT5卫星影像按共线方程法进行有控制点的几何纠正的方法,经对关中、陕北和陕南三种地形的影像纠正结果进行对比检验,证明了该方法精度达到了较高水平。  相似文献