Effect of Inter-Column Spacing on Soil Stresses due to Vibro-Installed Stone Columns: Interesting Findings   总被引：1，自引：0，他引：1  

Hesham Elshazly  Mohamed Elkasabgy  Azza Elleboudy 《Geotechnical and Geological Engineering》2008,26(2):225-236

This paper reveals the interesting relation between the inter-column spacing and the corresponding alteration of soil state of stresses due to the vibro-installation technique. This relation is inferred from analyses for load settlement records of various field load tests, performed for stone columns arrangements with different inter-column spacing values. In order to have adequate confidence in the findings, a well-documented case history, involving three columns patterns along with their relevant field and laboratory test results, is utilized for this study. Moreover, a well-tested finite element model, capable of simulating both elasto-plastic and time dependent soil deformations as well as pore water pressure building and dissipation, is employed in the analysis. Instead of determining the soil response to the test load, based on known initial soil stresses and material properties, the analysis is inversely posed to determine the soil initial stresses, based on the recorded settlements and the post-installation material properties. The alteration in the soil state of stress is represented by the increase in the post-installation horizontal to vertical stress ratio, K*, as a function of the inter-column spacing. It is found that this alteration experiences a systematic decrease in its magnitude as the inter-column spacing increases.  相似文献   

Burial and scour around short cylinder under progressive shoaling waves     

S. I. Voropayev  F. Y. Testik  H. J. S. Fernando  D. L. Boyer 《Ocean Engineering》2003,30(13):1647-1667

The results of a laboratory experimental program aimed at better understanding the scour around and burial of heavy cylindrical objects under oscillating flow on a sandy bed are described. This study was motivated by its application to the dynamics of isolated cobbles/mines on a sandy floor under nonlinear progressive waves, such as that occur in shallow coastal waters beyond the wave-breaking region. In the experiments, nonlinear progressive waves were generated in a long wave tank of rectangular cross-section with a bottom slope. Model mines (short cylinders) were placed on the sandy bottom and the temporal evolution of the bed profile and the velocity field in the near field of the object were observed. Experiments were conducted at relatively high Reynolds numbers for a range of flow conditions, which can be characterized by the Keulegan–Carpenter number and Shields parameter. Depending on the values of these parameters, four different scour regimes around the cylinder including periodical burial of cylinder under migrating sand ripples were observed; they were classified as: (i) no scour/burial, (ii) initial scour, (iii) expanded scour, and (iv) periodic burial cases. A scour regime diagram was developed and the demarcation criteria between different regimes were deduced. Semi-empirical formulae that permit estimation of the scour depth with time, the equilibrium maximum scour depth and length, and conditions necessary for the burial of the cylinder as a function of main external parameters are also proposed.  相似文献   

昆仑山地震前长波辐射异常特征分析   总被引：3，自引：1，他引：3  

冯蜀青  李萍  杨英莲  张娟 《高原地震》2002,14(2):22-28

应用NOAA、AVHRR资料反演的地气长波辐射值OLR对2001年11月14日昆仑山口西8.1级地震进行了追踪研究。结果表明：2001年10月起OLR出现明显的异常带，随时间的变化，异常区域不断向未来的震源聚拢，并且在未来地震震中区持续存在小的OLR高值闭合区，10月开始OLR出现突出的反常升势。  相似文献   

异型柱框架结构抗震设计研究   总被引：1，自引：1，他引：1  

肖建庄  黄珏  李杰  张盛东 《地震工程与工程振动》2003,23(2):85-88

本文在充分考虑钢筋混凝土异型柱框架结构受力特点的基础上，从结构布置、内力组合与调整、轴压比限值和其他构造措施等方面，针对抗震计算和概念设计进行了分析与讨论，得出注重抗震计算分析、加强抗震概念设计等结论，分析过程和有关结论可供工程设计人员参考。  相似文献   

华北地区大震前区域地震活动的中短期变化          下载免费PDF全文

林怀存  刘希强 《地震地质》1997,19(1):38-42

对发生在华北地区３１个Ｍ≥５地震震前区域地震活动的时间序列进行的研究得出：（１）华北地区发生Ｍ≥５地震前，区域地震活动的短期平静现象与大震发生的相关性很强。３１个Ｍ≥５地震前的平静时间主要集中在２０～８７ｄ，１２０～２１０ｄ和大于２１０ｄ。同时还得出大震前的短期平静时间与震级大小无关的结论；（２）区域地震活动在短时间内出现增强趋势，与发生大震的相关性很弱，相关的仅占总数的６．４％  相似文献   

线性度方法在前兆观测数据分析处理中的应用   总被引：3，自引：1，他引：3  

吴国有  关华平 《中国地震》1997,13(1):52-58

利用空间线性度方法，对前兆场中不同台站，不同学科的前兆观测数据从总体形态上进行综合分析，得到关于描述前兆场的新的特征量ａ（空间线性度）本文给出了空间线性度的具体计算方法，并以华北地区为例，分析处理了区内１９７０～１９９４年部分地电阻率和地下水位观测资料，所得结果表明，新的前兆特征量ａ在中强地震之前一年左右时间内有异常显示。  相似文献   

Seismic response analysis of multidrum classical columns     

Dimitrios Konstantinidis  Nicos Makris 《地震工程与结构动力学》2005,34(10):1243-1270

This paper presents a numerical investigation on the seismic response of multidrum classical columns. The motivation for this study originates from the need to understand: (a) the level of ground shaking that classical multidrum columns can survive, and (b) the possible advantages or disadvantages of retrofitting multidrum columns with metallic shear links that replace the wooden poles that were installed in ancient times. The numerical study presented in this paper is conducted with the commercially available software Working Model 2D?, which can capture with fidelity the sliding, rocking, and slide‐rocking response of rigid‐body assemblies. This paper validates the software Working Model by comparing selected computed responses with scarce analytical solutions and the results from in‐house numerical codes initially developed at the University of California, Berkeley, to study the seismic response of electrical transformers and heavy laboratory equipment. The study reveals that relative sliding between drums happens even when the g‐value of the ground acceleration is less than the coefficient of friction, µ, of the sliding interfaces and concludes that: (a) typical multidrum classical columns can survive the ground shaking from strong ground motions recorded near the causative faults of earthquakes with magnitudes M_w=6.0–7.4; (b) in most cases multidrum classical columns free to dislocate at the drum interfaces exhibit more controlled seismic response than the monolithic columns with same size and slenderness; (c) the shear strength of the wooden poles has a marginal effect on the sliding response of the drums; and (d) stiff metallic shear links in‐between column drums may have an undesirable role on the seismic stability of classical columns and should be avoided. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

柯坪6.5级地震的部分前兆异常及预报     

王玉珍  杨德宏 《内陆地震》1991,5(4):362-367

1991年2月25日柯坪6.5级地震前,震中附近地区的土层地应力、金属摆倾斜仪等多项前兆观测出现异常变化,说明强震发生前近场灵敏度较低的简陋仪器也能观测到明显的前兆反应。分析、认识这些异常对地震短临预报的决策是有益的。  相似文献   

北京地区“环流－降水－谷物”系统的短期振动研究          下载免费PDF全文

黄嘉佑  张镡  颜明元 《应用气象学报》1994,(3)

文章用因子分析方法提取北京地区小麦气象产量主要特征及代表序列，并对该序列和北京地面气象要素的关系用交叉谱进行研究。发现它们在前期秋冬季中的４－６年的周期振荡（中心周期为４．５年）中有显著的相关，当前期秋季和冬季的降水量和气温在振荡中处于正距平时，当年的气象产量为丰年，反之为欠年；进一步对该序列与大气环流的静力和动力物理量之间关系研究发现它们在同样的周期振荡中有十分强烈的表现，尤其表现在与动力物理量上。研究结果进一步证实“环流－降水－谷物”系统的存在，并揭示在短期气候振动（４－６年）上的规律性。  相似文献   

印尼8.7级地震前银川台形变数字化观测资料短临异常特征分析   总被引：1，自引：1，他引：1  

李国斌 《高原地震》2005,17(2):33-37

采用形变观测资料分析方法中比较常用的形态法、差分法、消除潮汐改正和零漂法，处理了银川台形变数字化观测资料，发现在印尼8．7级地震前出现了一些短临异常情况，并对异常的变化特征做了相应的分析。  相似文献