青海滑坡初探

青海是我国滑坡灾害比较严重的地区之一。本文简要阐述了青海滑坡灾害的地质环境、类型、分布、影响因素等,并分析了滑坡灾害的发展趋势。对青海滑坡的治理提供借鉴。     

滚石灾害防治方法浅析

随着人类活动的广度和力度不断加大,多山地带的滚石问题越来越突出,致使有关滚石灾害及其防治方法的研究也逐步得到重视。总体而言,滚石灾害的防治方法可分为主动防护和被动防护两大类,可应用于不同的滚石灾害环境。对各类滚石灾害防治方法进行简单介绍之后,作者分析了各方法的应用范围和适用条件。     

四川华蓥山地重力灾害类型及成因分析

从华蓥山所处的地理位置出发,全面的介绍了华蓥山地区近些年来的重力灾害发生的情况,可以看到重力灾害在本地区的影响之大,已经成为了本地区主要的灾害类型。通过各方面的调查研究,采用科学分析和经验指导相结合的方法,分析了引起重力灾害发生的各种因素,并重点从地质因素、水体因素、人为因素等3方面分析了华蓥山地重力灾害发生的成因,总结了可以引起重力灾害发生的外因和内因,可以看到重力灾害不单是某一个因素导致,而是由于众多的因素相互的影响所导致的。采取各种措施来预防灾害的发生,减少灾害给人类的生产和生活带来的危害。     

四川省万县市滑坡群灾害灾情评估

地质灾害的全部过程可以概括为灾前孕育阶段、灾害活动阶段和灾后恢复阶段等三个阶段。对地质灾害灾情评估应包括对灾害灾情进行系统调查、统计、分析和评价等项工作,评估的重点是整个地质灾害形成过程中的灾害活动情况。本文以四川省万县市为例,在论述地质灾害灾情评估理论的基础上,对万县市的地质灾害～滑坡群进行了灾情的评估。     

山摧江溢路不通——————漫话泥石流

 甘肃舟曲的特大泥石流灾害引发了人们对泥石流的关注,本文从力学角度讨论了什 么是泥石流,泥石流产生的原因,以及防范泥石流灾害需注意的一些问题.     

东日本大地震引发的思考

 从近期发生的东日本大地震说起, 简述了火山、地震、海啸等灾害的爆发机理, 探讨了潮汐这一引发灾害可能诱因的本质内涵和其对地壳活动的影响.     

临汾地面沉降数值模拟及其与地裂缝灾害关系研究

临汾市区是继西安、大同等地区之后又一地裂缝灾害比较严重的地区, 已经严重影响着临汾市经济的可持续性发展。经研究表明, 地下水超采为影响该区地裂缝灾害的第二大因子, 它是通过地面沉降来促使地裂缝的形成和发展。本文通过对临汾市区地面沉降进行数值模拟, 总结出了地面沉降的变化规律。分析认为, 地裂缝灾害的易出现部位为沉降梯度陡变带, 即沉降梯度最大处。     

喜马拉雅山地区重大滑坡灾害及其与地层岩性的关系研究

位于青藏高原南部的喜马拉雅山地区,是高原隆升最快的地方,这里内外动力作用异常活跃,是我国重大滑坡灾害最严重的地区之一,重大滑坡灾害对国民经济和社会发展带来了极大危害。本文在对研究区的地质、地理背景进行了详细分析的基础上,利用遥感解译和实地调查相结合的手段,研究了该区重大滑坡灾害的分布及其与地层岩性的关系,将本区地层岩性大致划分为13个工程地质岩组:松散岩组、软弱岩组、软弱岩夹较软弱岩组、软弱岩夹较坚硬岩组、较软弱岩组、较软弱岩夹软弱岩组、较软弱岩夹较坚硬岩组、较软弱岩夹坚硬岩组、较坚硬岩与软弱岩互层岩组、较坚硬岩夹软弱岩岩组、较坚硬岩夹较软弱岩组、较坚硬岩组、坚硬岩组,发现重大滑坡更容易发生在软弱岩组、较硬岩夹较软弱岩组以及坚硬岩组中,而软弱岩夹较软弱岩组、较软弱岩夹较坚硬岩组中无重大滑坡灾害分布。重大滑坡灾害的上述分布特征,反映出地层岩性与重大滑坡灾害之间的复杂关系,一方面岩性软弱,比较容易发生滑坡灾害; 另一方面,岩性越坚硬,地形越高陡,也容易发生重大滑坡灾害。     

汶川地震极重灾区地质背景及次生斜坡灾害空间发育规律

5·12汶川大地震造成大量的次生斜坡灾害,本次研究区域为汶川大地震的11个重灾区,包括汶川、北川、青川、安县、平武、茂县、江油、彭州、什邡、绵竹、理县等市县。通过对重灾区航片、卫片、雷达图像的解译研究发现,重灾区次生斜坡灾害的主要灾种表现为崩塌、滑坡以及崩塌、滑坡高速运动解体形成的碎屑流（个别地方由于水的参与表现为泥石流）以及它们堵江形成的堰塞湖。研究发现地震次生斜坡灾害的发育具有明显的丛集性规律。从区域上看,次生斜坡灾害明显呈带状,沿龙门山断裂带展布,并主要受北川—映秀断裂控制。各灾种的发育在不同地段发育的规模、频率差别较大。以灾害分布面积来排序,汶川县灾害面积最大,为131.55km2,其次为北川县,为45.57km2,其余9个县（市）灾害面积相差不大,均介于6~17km2,其中理县灾害面积最小,为6.25km2。各灾种的发育在不同地段发育的规模、频率差别较大。青川县、平武县灾种主要为滑坡,汶川县、茂县、安县、理县灾种主要表现崩塌转化的碎屑流,北川的主要灾种则为碎屑流,其次为滑坡,什邡、彭州、绵竹、江油等地主要灾种为崩塌。
灾种发育的这种地域性差别主要受控于地层岩性,除此而外,还与构造特征、地形地貌等因素紧密相关。研究表明：岩性对灾害种类的展布有决定性控制作用。统计发现,岩性越坚硬,崩塌、碎屑流发育率越高,滑坡则在软岩地区、较软岩地区和较坚硬区发育率最高,泥石流则在软岩地区最为发育。地形地貌对次生斜坡灾害的发育有重要影响,统计表明,崩塌、碎屑流以及泥石流在1200～2000m坡段范围内发育率最高,其次为800～1200m坡段;而滑坡则在800～1200m坡段范围发育率最高。对坡度而言,除11°~20°坡度范围外,崩塌和碎屑流的发育率总体具有随坡度增高而增大的特点;而滑坡和泥石流的发育率呈现典型的单峰特征,在1°~20°范围内发育率最大。坡向对地震次生斜坡灾害的发育影响不明显。
地震次生斜坡灾害的发育规律表明,地震斜坡灾害的发生主要受控于活动构造本身,并沿活动构造呈带状展布,同时受场地条件如岩性、地形地貌等因素的强烈控制。     

地震和风耦合作用下连体高层建筑联合易损性分析方法研究

近年来,城市地标建筑的建设中,高层连体建筑越来越受到青睐,在其服役期内不可避免地受到风和地震等多种灾害作用。而单一灾害作用下的结构失效概率低估了结构损伤乃至倒塌的可能性,迫切需要多灾害作用下的结构安全性能评价方法。本文以苏州国际会议酒店的连体高层建筑为对象,开展了地震和风耦合作用下的联合易损性分析方法研究。首先,建立了地震和风耦合作用下的多灾害易损性函数和结构性能需求函数,形成了多灾害联合易损性分析方法。随后,选取了地震动记录,开展了基于数值风洞的结构风荷载模拟,并进行了单一灾害作用下的结构易损性分析。最后,基于均匀分布抽样了100组地震和风耦合作用的荷载组合,开展了结构多灾害联合易损性分析。结果表明,结构易损性随着PGA和风速的增大而增大;相比单一灾害作用,地震与风耦合作用下,结构各破坏状态的失效概率均有所增加;当风速达40 m/s时,罕遇地震作用下结构轻微破坏、中等破坏、严重破坏和倒塌破坏的概率相比仅地震作用时分别增加了1.13%,35.67%,84.00%和98.33%。本文研究为复杂高层建筑多灾害安全性能评价提供了可用工具和参考。     

MULTISCALE MECHANICS OF BIOLOGICAL AND BIOLOGICALLY INSPIRED MATERIALS AND STRUCTURES

The world of natural materials and structures provides an abundance of applications in which mechanics is a critical issue for our understanding of functional material properties. In particular, the mechanical properties of biological materials and structures play an important role in virtually all physiological processes and at all scales, from the molecular and nanoscale to the macroscale, linking research fields as diverse as genetics to structural mechanics in an approach referred to as materiomics. Example cases that illustrate the importance of mechanics in biology include mechanical support provided by materials like bone, the facilitation of locomotion capabilities by muscle and tendon, or the protection against environmental impact by materials as the skin or armors. In this article we review recent progress and case studies, relevant for a variety of applications that range from medicine to civil engineering. We demonstrate the importance of fundamental mechanistic insight at multiple time- and length-scales to arrive at a systematic understanding of materials and structures in biology, in the context of both physiological and disease states and for the development of de novo biomaterials. Three particularly intriguing issues that will be discussed here include： First, the capacity of biological systems to turn weakness to strength through the utilization of multiple structural levels within the universality-diversity paradigm. Second, material breakdown in extreme and disease conditions. And third, we review an example where the hierarchical design paradigm found in natural protein materials has been applied in the development of a novel hiomaterial based on amyloid protein.     

GUST BUFFETING AND AEROELASTIC BEHAVIOUR OF POLES AND MONOTUBULAR TOWERS

The evolution in the constructional field and the realization of ever more slender and light structures have emphasized the increasing difficulty of properly evaluating the actions and effects of wind on poles and monotubular towers. Faced with this situation the Italian constructors, united in a consortium coordinated by ACS ACAI Servizi, entrusted the Department of Structural and Geotechnical Engineering of Genova University with the task of formulating an ad hoc calculation procedure for this type of structure. This gave rise to a wide-ranging research project in which theoretical models, experimental evaluations and engineering methods were developed in parallel through an effective and quite a unique co-operation between researchers, designers and builders. This paper illustrates the physical aspects, the general principles and the basic formulation of the method proposed, with special emphasis on gust buffeting and aeroelastic phenomena. Preliminary results of full-scale measurements of the structural damping are also presented. The conclusions highlight the scientific and technical perspectives of this research.     

FLUID FORCES AND DYNAMICS OF A HYDROELASTIC STRUCTURE WITH VERY LOW MASS AND DAMPING

In this paper we present some central new results from a study of the dynamics and fluid forcing on an elastically mounted rigid cylinder, constrained to oscillate transversely to a free stream. With very low damping, and with a low specific mass that is around 1% of the value used in the classic study of Feng (1968), we show that the cylinder excitation regime extends over a large range of normalized velocity (around four times that found by Feng), with a large amplitude which is around twice that of Feng. Four distinct regions of response are identified, namely the initial excitation region, the “upper branch” (of very high amplitude response), the “lower branch” (of moderate amplitude response), and the desynchronization region. There are distinct differences in the character of mode transitions, as follows. As normalized velocity is increased, there is a hysteretic jump from an initial excitation regime to the upper branch, whereas the jump from the upper to the lower branch involves an intermittent switching, which is illustrated by plotting the instantaneous phase between lift force and displacement using the Hilbert transform. Contrary to classical “lock-in”, whereby the oscillation frequency matches the structural natural frequency, we find that the oscillation frequency increases markedly above the natural frequency, through the excitation regime. Finally, we present the first lift force measurements for such a freely vibrating cylinder experiment, yielding a maximum lift coefficient of around 4·5, whereas a maximum drag coefficient of 6·0 is also measured. The lift is comparable, but somewhat higher, than the forces measured (C_L∼2·0) in the equivalent free-vibration experiments of Hoveret al.(1997), involving force-feedback and on-line computer-simulation of the modelled structure. Both the lift and drag maxima exhibit at least a five-fold increase over the stationary cylinder case. Perhaps the largest effect is found for the fluctuating drag, which is found to be upto 100 times that measured for a static cylinder.     

GPS在西安市地面沉降与地裂缝监测中的应用研究

本文从GPS监测网的布网原则和设计方案出发,对GPS外业观测和内业数据处理中的关键技术进行了深入研究,提出了一套适用于大城市地面沉降与地裂缝灾害监测的作业方法和数据处理方案。通过西安地区地面沉降和地裂缝的GPS监测实践,证明了本文提出的监测网的布设原则、GPS外业施测和内业数据处理方案是切实可行的,并且通过GPS监测获取了西安地面沉降和地裂缝近期活动的有关数据信息,且其与精密水准结果具有很好的一致性。     

泥石流预测、预报技术方法的研究现状浅析

泥石流灾害的预测、预报是减灾防灾重要环节和基础。在充分研究泥石流形成条件基础上 ,正确预测、预报泥石流 ,是目前最大限度减少泥石流灾害损失所采取的主要方法。本文综合了当前泥石流预测预报的方法 ,分析了泥石流长期、中期、短期预报及泥石流预报的原理 ,不同时期泥石流预报的特征及存在的问题。我国是受泥石流危害最为严重的国家之一。每年由泥石流造成的直接经济损失约达几十亿元之多 ,减少泥石流灾害造成的损失主要取决于预测预报工作等。     

COMPARISON OF THEORY AND EXPERIMENT ON AEROACOUSTIC LOADS AND DEFLECTIONS

The correlation of acoustic pressure loads induced by a turbulent wake on a nearby structural panel is considered: this problem is relevant to the acoustic fatigue of aircraft, rocket and satellite structures. Both the correlation of acoustic pressure loads and the panel deflections, were measured in an 8-m diameter transonic wind tunnel. Using the measured correlation of acoustic pressures, as an input to a finite-element aeroelastic code, the panel response was reproduced. The latter was also satisfactorily reproduced, using again the aeroelastic code, with input given by a theoretical formula for the correlation of acoustic pressures; the derivation of this formula, and the semi-empirical parameters which appear in it, are included in this paper. The comparison of acoustic responses in aeroacoustic wind tunnels (AWT) and progressive wave tubes (PWT) shows that much work needs to be done to bridge that gap; this is important since the PWT is the standard test means, whereas the AWT is more representative of real flight conditions but also more demanding in resources. Since this may be the first instance of successful modelling of acoustic fatigue, it may be appropriate to list briefly the essential “positive” features and associated physical phenomena: (i) a standard aeroelastic structural code can predict acoustic fatigue, provided that the correlation of pressure loads be adequately specified; (ii) the correlation of pressure loads is determined by the interference of acoustic waves, which depends on the exact evaluation of multiple scattering integrals, involving the statistics of random phase shifts; (iii) for the relatively low frequencies (one to a few hundred Hz) of aeroacoustic fatigue, the main cause of random phase effects is scattering by irregular wakes, which are thin on wavelength scale, and appear as partially reflecting rough interfaces. It may also be appropriate to mention some of the “negative” features, to which may be attached illusory importance; (iv) deterministic flow features, even conspicuous or of large scale, such as convection, are not relevant to aeroacoustic fatigue, because they do not produce random phase shifts; (v) local turbulence, of scale much smaller than the wavelength of sound, cannot produce significant random phase shifts, and is also of little consequence to aeroacoustic fatigue; (vi) the precise location of sound sources can become of little consequence, after multiple scattering gives rise to a diffuse sound field; and (vii) there is not much ground for distinction between unsteady flow and sound waves, since at transonic speeds they are both associated with pressures fluctuating in time and space.     

ADDED MASS AND OSCILLATION FREQUENCY FOR A CIRCULAR CYLINDER SUBJECTED TO VORTEX-INDUCED VIBRATIONS AND EXTERNAL DISTURBANCE

This paper reports results from an experiment with a lightly damped elastically mounted rigid cylinder subjected to constant flow velocity. The cylinder was allowed to vibrate in the cross-flow direction and was fixed in the flow direction. The Reynolds numbers varied from 10⁴to 6×10⁴. The added mass for the freely vibrating cylinder agreed well with the results found by others in driven cylinder tests. The predicted natural frequency based on the measured added mass was approximately equal to the measured mean oscillation frequency. The added mass calculated from one oscillation cycle to the next varied considerably. The oscillation frequency from one oscillation to the next corresponded to the natural frequency including the added mass for the same cycle. By movement of the attachment point of the elastic members to the external structure a disturbance could be added to the normal vortex-induced vibrations (VIV) response. When an external disturbance was introduced at a frequency other than the VIV frequency, the added mass coefficient was found to be weakly influenced by the external harmonic disturbance.     

DYNAMICS AND STABILITY OF PINNED–CLAMPED AND CLAMPED–PINNED CYLINDRICAL SHELLS CONVEYING FLUID

The paper examines the dynamics and stability of fluid-conveying cylindrical shells having pinned–clamped or clamped–pinned boundary conditions, where “pinned” is an abbreviation for “simply supported”. Flügge's equations are used to describe the shell motion, while the fluid-dynamic perturbation pressure is obtained utilizing the linearized potential flow theory. The solution is obtained using two methods — the travelling wave method and the Fourier-transform approach. The results obtained by both methods suggest that the negative damping of the clamped–pinned systems and positive damping of the pinned–clamped systems, observed by previous investigators for any arbitrarily small flow velocity, are simply numerical artefacts; this is reinforced by energy considerations, in which the work done by the fluid on the shell is shown to be zero. Hence, it is concluded that both systems are conservative.     

软岩流变过程与强度研究

文中通过分析软岩流变特征找出流变速度与作用载荷之间的关系。利用U-σ相关曲线确定能够反映流变过程的4个特征点(流变起始点、等速流变起始点、加速流变起始点、流变破坏点).根据4个特征点的变化规律确定临界等速流变应力的方法和流变强度取值原则。     

青藏铁路多年冻土区沼泽化斜坡路基稳定性分析

青藏铁路多年冻土斜坡段路基稳定性对铁路长期运营具有潜在的威胁,分析评价当前和未来斜坡路基稳定性可指导路基工程的正确设计和施工,从而保证铁路的安全运营。多年冻土地温变化使斜坡路基稳定性分析不同于普通土路基,其冻融交界面位置是制约斜坡路基稳定性的关键所在。通过对安多试验段3a来的地温监测,分析路基地温变化规律,并预测了未来50a内试验段地温的变化趋势,建立了当前和未来条件下的斜坡路基稳定性模型,计算分析了斜坡路基的稳定性。通过上述研究,取得以下认识和结论:(1)铁路路堤的填筑,引起多年冻土温度场重分布;由于坡向不对称和几何不对称,使得地温场存在不对称;(2)依据冻融界面位置和活动层的地温特征将冻土路基划分为4个不同时期,即冬季严寒期(1~2月)、春夏融化活动期(3~8月)、最大融深期(9~10月)及回冻活动期(11~12月);通过计算对比分析,每年最大融深期的稳定性系数最小;(3)数值分析的预测结果表明,20a以后,安多段试验段路基的多年冻土完全退化,在所预测的第10年最大融深期稳定性系数最小。