冻结粉土动强度的荷载效应及长期极限动强度   总被引：4，自引：1，他引：3  

沈忠言 《冰川冻土》1998,20(1):42-45

荷载效应包括速率效应和疲劳效应两部分．速率效应使冻土的动强度和退荷回弹动弹模随应变速率加快而提高;疲劳效应使冻土的动强度随振频增加而下降,但在低应变速率下却使动强度略有提高．在高应变速率下动强度大于静强度,在低应变速度下动强度小于静强度,其间存在一个临界应变速率．通过动强度－破坏振次关系,可确定长期极限动强度．  相似文献   

冲击荷载作用下饱和软粘土孔压增长与消散规律   总被引：17，自引：3，他引：14  

白冰  刘祖德 《岩土力学》1998,(2)

通过大量室内试验,研究饱和软粘土在冲击荷载作用下的变形和孔压增长规律,讨论孔压增长的内在机理和不同围压、不同冲击能作用下孔压量的变化。讨论土体的再团结变形规律,提出再固结体积压缩系数的确定方法。最后分析冲击荷载作用后的强度变化。这些讨论为动静结合法处理软基提供了依据。  相似文献   

The non-agricultural economy in post-socialist rural Romania: The insights and perceptions of national, regional and local institutions     

Wilfried Heller 《GeoJournal》1998,46(3):199-205

This study evaluates some aspects of the socio-economic transformation of rural Romania with reference to the views of representative organisations (at national, regional and local levels) and other experts. Interviews conducted in ten communes of nine Romanian counties (‘judete’) focus attention on the advantages and disadvantages of system change experienced since 1989; the most important problems and constraints for future socio-economic change; and appropriate policies and perspectives for development in the immediate future. Wherever appropriate the claims of interviewees are substantiated through reference to statistics, drawn in many cases from Chambers of Commerce & Industry (CCI). Local level representatives presented much more negative views on recent change than their national and regional level counterparts, but all agreed on the crucial problem of capital shortage. Thus while specific programmes to assist rural areas are justified, they cannot fully succeed until the national economy is able to grow more rapidly and attract greater foreign investment. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

新型耗能(阻尼)减震器的开发与研究   总被引：18，自引：7，他引：11  

周云  刘季 《地震工程与工程振动》1998,18(1):71-79

本文阐述了耗能减震的概念和原理,提出了耗能减震器设计的新思想,研制开发了多种新型实用耗能（阻尼）减震器,并对其中的圆环耗能器、双环耗能器、架颈圆环耗能器、弹塑性－摩擦复合耗能器等进行了循环荷载试验,考察了耗能器代作性能和耗能性能,对已装与未装耗能减震器的钢筋混凝土框架模型进行了伪动力对比实验,进一步考察了耗能减震器的减震效果。在试验研究的基础上,地耗能（阻尼）减震结构体系的分析方法进行了研究,并编  相似文献   

滁州市会峰大厦桩基垂直静荷载试验研究     

黄永浩  秦厚慈  沈国英 《安徽地质》1998,(1)

本文根据滁州市会峰大厦人工挖孔扩底桩的垂直静荷载试验成果,分析研究了滁州市红砂岩地基嵌岩桩的荷载有受力特征。  相似文献   

Mechanisms of isostatic compensation in the vicinity of the East African Rift, Kenya     

Timothy D. Bechtel  Donald W. Forsyth  Christopher J. Swain 《Geophysical Journal International》1987,90(2):445-465

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A new approximation for pore pressure accumulation in marine sediment due to water waves     

D.‐S. Jeng  B. R. Seymour  J. Li 《国际地质力学数值与分析法杂志》2007,31(1):53-69

The residual mechanism of wave‐induced pore water pressure accumulation in marine sediments is re‐examined. An analytical approximation is derived using a linear relation for pore pressure generation in cyclic loading, and mistakes in previous solutions (Int. J. Numer. Anal. Methods Geomech. 2001; 25 :885–907; J. Offshore Mech. Arctic Eng. (ASME) 1989; 111 (1):1–11) are corrected. A numerical scheme is then employed to solve the case with a non‐linear relation for pore pressure generation. Both analytical and numerical solutions are verified with experimental data (Laboratory and field investigation of wave– sediment interaction. Joseph H. Defrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 1983), and provide a better prediction of pore pressure accumulation than the previous solution (J. Offshore Mech. Arctic Eng. (ASME) 1989; 111 (1):1–11). The parametric study concludes that the pore pressure accumulation and use of full non‐linear relation of pore pressure become more important under the following conditions: (1) large wave amplitude, (2) longer wave period, (3) shallow water, (4) shallow soil and (5) softer soils with a low consolidation coefficient. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Soil-Structure Interaction Analysis of Jack-up Platforms Subjected to Monochrome and Irregular Waves     

Maziar Gholami KORZANI  Ali Akbar AGHAKOUCHAK 《海洋工程》2015,29(1):65-80

As jack-up platforms have recently been used in deeper and harsher waters, there has been an increasing demand to understand their behaviour more accurately to develop more sophisticated analysis techniques. One of the areas of significant development has been the modelling of spudcan performance, where the load-displacement behaviour of the foundation is required to be included in any numerical model of the structure. In this study, beam on nonlinear winkler foundation (BNWF) modeling—which is based on using nonlinear springs and dampers instead of a continuum soil media—is employed for this purpose. A regular monochrome design wave and an irregular wave representing a design sea state are applied to the platform as lateral loading. By using the BNWF model and assuming a granular soil under spudcans, properties such as soil nonlinear behaviour near the structure, contact phenomena at the interface of soil and spudcan (such as uplifting and rocking), and geometrical nonlinear behaviour of the structure are studied. Results of this study show that inelastic behaviour of the soil causes an increase in the lateral displacement at the hull elevation and permanent unequal settlement in soil below the spudcans, which are increased by decreasing the friction angle of the sandy soil. In fact, spudcans and the underlying soil cause a relative fixity at the platform support, which changes the dynamic response of the structure compared with the case where the structure is assumed to have a fixed support or pinned support. For simulating this behaviour without explicit modelling of soil-structure interaction (SSI), moment-rotation curves at the end of platform legs, which are dependent on foundation dimensions and soil characteristics, are obtained. These curves can be used in a simplified model of the platform for considering the relative fixity at the soil-foundation interface.  相似文献   

不同洞口位置节能砌块隐形密框复合墙体恢复力模型研究          下载免费PDF全文

倪博文  李升才  朱永甫 《世界地震工程》2022,38(1):056-68

为研究洞口位置对节能砌块隐形密框复合墙体滞回特性的影响,对6个采用低周反复加载方式的1/2缩尺试件的试验现象及数据进行分析。基于试验结果和现有恢复力模型理论,对试验数据进行拟合分析,利用退化四折线模型和回归方法,建立节能砌块隐形密框复合墙体的四折线恢复力模型。试验结果表明:当洞口位于墙体中间时,试件滞回环愈加丰满,试件初始刚度有所增加,承载力衰减速率减小,卸载刚度退化速率变慢。通过对骨架曲线特征参数的计算,并和试验骨架曲线对比,两者吻合较好,表明该恢复力模型可以较好的反映出不同洞口位置对其滞回特性的影响,可为节能砌块隐形密框复合墙体的弹塑性分析及工程应用提供参考。  相似文献   

A nutrient loading budget for Biscayne Bay, Florida     

Caccia VG  Boyer JN 《Marine pollution bulletin》2007,54(7):994-1008

The water quality in Biscayne Bay has been significantly affected by past and continuing coastal and watershed development. The nutrient concentrations in the Bay have been dramatically changed by the conversion of natural creeks and sheet flow freshwater inputs to rapid and episodic canal inputs from the large and rapidly expanding Miami metropolitan area. This study is an evaluation of nutrient loadings to Biscayne Bay for 1994-2002 from canal, atmospheric, and groundwater sources. Dissolved inorganic nitrogen (DIN, as nitrate, nitrite, and ammonium) and total phosphorus (TP) loadings by the canals were influenced by their geographic locations relative to discharge amount, watershed land use, stormwater runoff, and proximity to landfills. Annual budgets showed that canals contributed the bulk of N loading to the bay as 1687.2 metric ton N yr(-1) (88% total load). Direct atmospheric DIN load for Biscayne Bay was only 231.7 ton N yr(-1), based on surface area. Of the canal DIN load, nitrate+nitrite (NO(x)(-)) loading (1294.5 ton N yr(-1)) made up a much greater proportion than that of ammonium (NH(4)(+), 392.6 ton N yr(-1)). In the urbanized north and central Bay, canal DIN load was evenly split between NO(x)(-) and NH(4)(+). However, in the south, 95% of the DIN load was in the form of NO(x)(-), reflecting the more agricultural land use. Contrary to N, canals contributed the only 66% of P load to the bay (27.5 ton P yr(-1)). Atmospheric TP load was 14 ton Pyr(-1). In the north, canal P load dominated the budget while in the south, atmospheric load was almost double canal load. Groundwater inputs, estimated only for the south Bay, represented an important source of N and P in this zone. Groundwater input of N (141 ton N yr(-1)) was about equal to atmospheric load, while P load (5.9 ton P yr(-1)) was about equal to canal load.  相似文献