Bridge pier scour mitigation under steady and unsteady flow conditions

Watercourse morphology is affected by local scouring when the flow interferes with anthropic structures. Controlling the scour hole size is of predominant importance to guarantee bridge safety as well as to limit the variations of river morphology. A combined countermeasure against bridge pier scour is proposed and tested in order to reduce the maximum scour depth and deviate it away from the bridge foundation. In the first part of the laboratory campaign, combination of two countermeasures (bed-sill and collar) was evaluated for a circular pier under clear-water and live-bed steady flow conditions. The proposed combined countermeasure exhibited an efficiency of about 64% in terms of scour depth reduction. Afterwards, it was tested in unsteady flow conditions, first for a circular pier, then in the case of a rectangular pier with round nose and tail, two circular in-line piers and two rectangular in-line piers, under a hydrograph with a peak flow velocity slightly above the threshold condition of sediment motion. Results showed that the combined countermeasure had an efficiency of about 63% for a single circular pier; however, higher efficiency (about 75%) was obtained in applications to rectangular pier and two in-line circular or rectangular piers.     

包头6．4级地震灾害特点及城市地震对策

分析总结了1996年包头6.4级地震的地震地质背景、工程场地条件及地震灾害特点,介绍了包头市的城市地震防御措施和应急对策,提出城市地震应急对策的主要问题。     

高层建筑结构中粘滞阻尼器的新型安装方式

在建筑结构中,一般粘滞阻尼器均布置在层间,但在有些情况下较小的层间位移差在一定程度上制约了阻尼器性能的充分发挥。系统回顾了为解决这一问题,目前最新的一些解决方案:改进层间阻尼器的连接方式,如基于连杆结构、杠杆原理与齿轮机构的位移放大系统,及大对角支撑;新型结构保护系统,如利用结构构件竖向振动位移及框架核心筒结构的加强层阻尼系统等,并重点分析了加强层阻尼系统。     

Effect of soil stabilization on audible band railway ground vibration

Although railway-generated ground vibrations usually have greater energy levels at lower frequencies, vibrations in the audible range above 20 Hz can nevertheless be relevant for secondary noise problems in buildings. One countermeasure is soil stabilization under the track embankment. While effective at low frequencies, a potential side effect is amplification in some audible bands. Presented here are both experimental and theoretical assessments of the countermeasure in the audible bands. The main innovation is the treatment of an infinite periodic track–ground system, using a transfer matrix approach with a repeating element including the rail, pad, sleeper, and an underlying half-space (ballast and soil). Excitation in this band is attributed to rail and wheel roughness. The model makes successful predictions when the half-space properties are allowed to be frequency-dependent such that the dispersion of the surface wave matches that in the actual layered earth (including ballast and underlying soil layers). The field measurements are also unique in that both before and after evaluation of the countermeasure was possible.     

地震作用下双薄壁高墩刚构桥桥台处的碰撞效应及减碰措施

针对双薄臂高墩连续刚构桥两侧桥台处主梁与背墙的碰撞现象,基于桥台-背土作用简化模型和Kelvin碰撞模型,采用非线性时程法研究碰撞对双薄臂墩地震剪力、弯矩、曲率和位移,以及支座纵向变形的影响。提出可牺牲背墙、阻尼器、加强型横系梁等三种减碰措施,并对比分析其减碰效果。研究表明:碰撞会显著增大高墩的地震内力和曲率响应,降低墩顶位移和支座的纵向变形;碰撞刚度的变化对碰撞效应的影响在20%以内;可牺牲背墙和阻尼器两种减碰措施均可大幅降低桥墩的地震内力和曲率,使其接近不考虑碰撞时的状态,阻尼器同时还可以保护支座不超过容许变形,而可牺牲背墙则会导致支座的地震破坏;加强型横系梁不能发挥减碰作用,反而会增大桥墩的地震响应。     

Liquefaction countermeasures by shallow ground improvement for houses and their cost analysis

A large number of houses suffered from liquefaction-induced damages in recent large earthquakes due to lack of economical countermeasures. In this study, the shallow ground improvement, up to several meters deep, was proposed as an economical liquefaction countermeasure for houses. Based on the case studies, the design criteria of allowable tilt angles and penetration settlements of houses were proposed for the required level of serviceability against moderate and large earthquakes. The results of questionnaire survey, airborne LiDAR survey and centrifuge model tests demonstrated that even a few meters of non-liquefiable layers in shallow ground could greatly reduce settlements and tilting of houses. A series of numerical analyses indicated that non-liquefiable layer of three meters thick below ground water table improved by solidification methods can prevent significant damages of houses. Furthermore, cost analyses were carried out for different ground improvement methods for both new and existing houses.     

东莞市区震害预测与防御对策系统建设

在地震小区划、概率设定地震和广泛收集地震地质、建(构)筑物、生命线工程、地震次生灾害源、社会环境与经济人口数据等的基础上,对东莞市区89.3 km2范围工作区开展震害预测与防御对策研究,得到不同烈度下建(构)筑物、生命线工程的震害分析结果,以及地震次生灾害影响、人员伤亡与经济损失评估结果,对工作区及东莞市的抗震能力进行...     

张家口市防震减灾宣传工作的特点和对策

本文总结了近年来张家口市防震减灾宣传工作的特点和对策。防震减灾是一项社会公益事业,涉及到各行各业,需要全社会的理解和大力支持,希望社会各界都来关注、参与防震减灾工作。     

Stone columns as liquefaction countermeasure in non-plastic silty soils

In many cases densification with vibro-stone columns cannot be obtained in non-plastic silty soils. Shear stress re-distribution concepts [1] have been previously proposed as means to assess stone columns as a liquefaction countermeasure in such non-plastic silty soils. In this study, centrifuge testing is conducted to assess the performance of this liquefaction countermeasure. Attention is focused on exploring the overall site stiffening effects due to the stone column placement rather than the drainage effects. The response of a saturated silt stratum is analyzed under base dynamic excitation conditions. In a series of four separate model tests, this stratum is studied first without, then with stone columns, as a free-field situation, and with a surface foundation surcharge. The underlying mechanism and effectiveness of the stone columns are discussed based on the recorded dynamic responses. Effect of the installed columns on excess pore pressures and deformations is analyzed and compared. The test results demonstrate that stone columns can be an effective technique in the remediation of liquefaction induced settlement of non-plastic silty deposits particularly under shallow foundations, or vertical effective stresses larger than about 45 kPa (1000 psf) in free field conditions.     

Numerical assessment of liquefaction mitigation effects on residential houses: Case histories of the 2007 Niigata Chuetsu-offshore earthquake

In this study, the effectiveness of liquefaction countermeasures for residential houses was explored using a fully coupled dynamic effective-stress finite element procedure. Numerical analyses were conducted on two wooden houses that were damaged to different degrees due to dune liquefaction during the 2007 Niigata Chuetsu-offshore earthquake. House A, which was only improved by horizontal drainage pipes to lower the ground water level, was completely destroyed; however, house B, which was improved by a horizontal drainage system, soil–cement mixtures, and steel-pipe piles, was slightly deformed. Numerical results show that the effects of the sand dune slope on the damage to the two houses were somewhat different. For house B, it was found that the steel-pipe piles were more effective. Two countermeasures generally led to a greater degree of reduction in both lateral and vertical displacements of house B than only a single countermeasure employed. In addition, the combined implementation of steel-pipe piles and soil–cement mixtures was the most effective among the cases with two countermeasures.     

中国海域及其相邻海域地震烈度区划图及简要说明

我国具有辽阔的海域,随着国民经济的发展,我国海域资源的开发和利用将日趋重要,海上活动愈来愈频繁。因此编制中国海域及其相邻海域地震烈度区划图(它是海域地震对策的组成部份)就成为十分必要的了。由于我国海域地震资料和地质构造资料较少,精度较差,故已往未进行过海域地震烈度区划。本文综合研究了海域地震资料、地质资料、地形资     

Did annual run‐off and low flow decrease with reduced forestry practices in Japan?

Japan developed large areas of coniferous plantations for timber production between the 1950s and 1970s; however, forestry practices such as thinning, pruning, and harvesting in most of the plantations have declined since the 1980s. Researchers speculated that reduced forestry practices could reduce run‐off and therefore available water resources. As a countermeasure to this potential risk, many local governments have introduced local taxes to stimulate forestry practices in the plantations. However, no studies have presented evidence for decreased annual run‐off and/or low flow in watersheds where forestry practices have declined. As a starting point for assessing this risk, this study examined potential changes in the annual run‐off and low flow in the Terauchi watershed. A large area of this watershed was covered with coniferous plantations. We first surveyed the annual investment in forestry operations and the number of forest owners in the city of Amagi. (Note that Amagi includes the Terauchi watershed.) Both decreased during the period 1979–2007, indicating reduced forestry practices. The frequency distribution of plantation tree ages in the watershed also suggested reduced forestry practices. After excluding the effect of precipitation, we examined potential changes in the annual run‐off and low flow during the period 1979–2007. We did not observe significant decreases in the annual run‐off and low flow during the period. Thus, the risk of decreased water resources might be less than expected, and countermeasures to the risk should be reconsidered. Copyright © 2010 John Wiley & Sons, Ltd.     

论工业企业防震减灾

本文论述了我国工业企业防震减灾现状，提出工业企业防震减灾的目标和指导原则，以及部分工业企业的防震减灾措施和对策。     

Particle image velocimetry evaluation of flow-altering countermeasures for local scour around a submerged circular cylinder

The effect of scour countermeasures on the mechanism of local scour around a cylinder requires clarification in order to develop design methodology for use in practice. Previous investigations on countermeasure performance, though useful, have not provided adequate measurements to support this understanding. In the present investigation, particle image velocimetry(PIV) measurements were acquired at several streamwise-vertical planes in the flow field surrounding a submerged circular cylinder wit...     

新时期防震减灾宣传工作的特点与对策

本文以青岛市的防震减灾宣传实践为例, 总结了近年来青岛市防震减灾宣传工作的特点与对策.     

城市地震灾害与防震减灾对策

综合有关资料显示,地震灾害造成城市人员重大伤亡,经济损失惨重,是毁城之首。城市震灾具有许多特点,是防震减灾的重中之重,提出了城市的综合防震减灾对策,可减轻未来震灾损失,促进社会的稳定和可持续发展。     

乐山市诱发地震及对策研究的进展

乐山市诱发地震及对策研究获2007年度乐山市科学技术进步三等奖。本文介绍了乐山市内的水溶采盐诱发地震和水库蓄水诱发地震的特点、成因及对策。     

A Challenge of Water Purification in Dokai Bay, Japan

A history of water pollution and countermeasures for water purification in Dokai Bay, Japan are reviewed. Now, Dokai Bay suffers from the occurrences of red tides and oxygen-deficiency in summer. In order to prevent the occurrences of red tides and oxygen-deficiency, an ecological numerical model has been developed. The model experiments forecast that when the phosphorus or nitrogen load from land will be cut by 90% or 95%, respectively, red tides and oxygen-deficiency will not occur in Dokai Bay. If the industrial and sewage facilities are not sufficient to cut the nutrients load to the necessary degree, we have to consider other countermeasures such as cultivating bivalves and algae in order to decrease the nutrients concentration in the bay. International co-operation related to coastal zone management is also discussed.     

浅析汶川地震后的建设工程抗震设防管理

基于汶川地震中建设工程受灾状况,对建设工程抗震设防的现状进行初步分析,对目前建设工程抗震设防工作中存在的问题及其对策进行探讨,以促进该项工作能够健康有序地向前推进。     

生物操纵与非经典生物操纵的应用分析及对策探讨

分析了生物操纵(biomanipulation)和非经典生物操纵(non-traditional biomanipulation)理论的原理、应用条件及局限性,提出了在局部水体治理湖泊富营养化的对策.分析认为:生物操纵的核心内容是利用浮游动物控制藻类;但浮游动物不能有效控制丝状藻类和形成群体的蓝藻水华;我国的大型浅水湖泊浮游动物数量一般并不多,对浮游植物摄食压力不大;在浅水湖泊,浮游动物摄食藻类后很快分解、释放又进入物质循环,因此不能治理湖泊富营养化;浮游动物是浮游植物和鱼类等经济水生动物之间重要的营养通道,过分追求保护浮游动物是值得思考和研究的问题.而非经典生物操纵的核心内容是利用鱼类直接控制蓝藻水华;当鲢、鳙鱼达到阈值密度可以控制蓝藻水华,但很难控制所有藻类和降低N、P治理湖泊富营养化.在局部水体治理湖泊富营养化的对策是:把鱼类控藻、水生植被恢复和局部水域生态系统重建相结合,形成具有利用与控制蓝藻生产鱼类、吸收氮磷净化水质功能的"水质生物调控单元".