关于地震科学实验场的一些思考——地下云图

由中国地震局和美国国家科学基金委、地质调查局合作建立的地震预报研究实验场为中国早期地震工作的发展起到了良好的推动作用。由于种种客观原因,地震预报实验场的多数预想目标未能达成,发展受到了阻碍。最近几年,实验场重新受到重视,并更名为"地震科学实验场"。结合目前地震学发展的前沿和防震减灾事业的实际需求,本文提出增加"地下云图"作为实验场的新方向。利用高重复性、环境友好、安全性高的气枪震源,持续激发地震信号,实现对地下介质速度变化的连续监测;结合背景噪声成像获得的高分辨率3维地壳结构,构建4维(三维空间+一维时间)地下结构成像。"地下云图"可以反映地下速度和应力变化,为全国范围的地震监测预测提供新的业务手段,推动地震预测从经验预测到物理预测的转换。     

15km3天然气球罐设计研究及优化

天然气的广泛应用,促进存储容器向大型化发展。以已投产使用的10km³天然气球罐为设计基础,设计建造完全国产化的15km³天然气球罐,利用计算参数建立有限元模型,验证模型的可靠性。建立双层拉杆模型,施加地震荷载及风载,进行动力响应分析及应力分析。为讨论双层拉杆最优位置及直径,建立了5种上下拉杆比例不同的模型,另外每种比例模型设计3种不同拉杆直径。结果表明:在8度设防二类场地地震波的情况下,上层和下层拉杆比例为0.618∶1,直径为50mm的模型对于球罐优化方面优于其他模型,球罐各项参数均显著减小且应力无放大效应。     

提高地浸钻孔出水量的有效技术措施

地浸钻孔是一种以采矿为目的的钻孔,提高钻孔出水量就是提高钻孔的采矿量。通过对多年地浸钻孔施工经验和理论进行分析,发现影响钻孔出水量的主要因素为钻井泥浆的成分和性能以及人工过滤层的渗透性差异,提出在地浸钻孔施工方案中采用植物胶净化泥浆钻进和扩孔、投砾罐射吸式填砾、物理化学组合洗井3种技术措施,对比前后施工钻孔的出水量大小,证明了该技术措施对提高地浸钻孔出水量具有良好的效果。     

冻融循环下花岗岩剪切蠕变试验与模型研究

为探讨冻融对寒区工程岩石剪切蠕变特性的影响,以吉林省辉白隧道花岗岩为研究对象,对经历不同冻融循环次数的试样开展细观特征分析和剪切蠕变试验。试验结果表明：（1）随着冻融次数的增加,试样裂隙、孔隙不断扩展,岩石表面损伤现象愈发明显;（2）试样主要以中小孔隙为主,孔隙度随着冻融次数的增加呈非线性增长趋势;（3）随着冻融循环次数增加,蠕变变形量和蠕变速率逐渐增大,而蠕变时长、破坏应力和长期强度均呈现明显降低趋势。根据试验结果,进行冻融岩石非定常蠕变参数的表达,提出了冻融岩石损伤黏性元件,构建了花岗岩冻融剪切蠕变本构模型。将蠕变试验曲线和理论模型拟合曲线进行对比,验证了模型的正确性和适用性。通过对蠕变参数进行敏感性分析,研究了其对花岗岩蠕变变形的影响,并给出了蠕变参数随冻融循环次数的变化规律。该研究结果对于寒区岩体工程长期稳定性评价具有指导意义。     

测绘工程实验教学示范中心建设初探

介绍了武汉大学测绘学院测绘实验教学示范中心建设情况,分析了实验示范中心所进行的实践与改革,对提高测绘工程专业水平有一定的参考意义。     

Experimental simulation of degrading structures through active control

In experimental studies of structural behaviour, it is often desirable, even necessary, to perform tests on a test structure from its undamaged state, through its damaged states, and finally to failure. The fact that experiments of this type are not often done primarily because of its prohibitive cost. In this paper, a testing procedure is proposed in which a test structure is allowed to undergo its degradation in real time yet it is not physically damaged, thus allowing it to be reused. The underlying concept is that of active structural control. Considerable research and development of active structural control in civil engineering has taken place relative to responsive control of structures against damaging environmental loads. While the use of active control systems to simulate damage in an experimental setting as proposed in this paper appears to be new, much of the existing knowledge base in active structural control is directly applicable. © 1998 John Wiley & Sons, Ltd.     

钢筋混凝土短肢剪力墙抗震性能试验研究

通过6片1：2单层短肢墙试体的低周反复荷戴试验,研究了在低周反复荷载作用下钢筋混凝土短肢剪力墙的整体工作性能、破坏形态及滞回特性。结果表明：试件的最终破坏均是由连梁失效引起的,连梁是短肢剪力墙结构的薄弱环节,因此,连梁的混凝土强度不应低于墙肢的混凝土强度,以免连梁出现粘结破坏;有翼墙的短肢剪力墙试体其延性系数都达到了3．5以上．其耗能能力较无翼墙短肢墙好。     

Relative quantification of wind erosion in argan woodlands in the Souss Basin,Morocco

The endemic argan woodlands cover large parts of South Morocco and create a characteristic landscape with areas of sparsely vegetated and bare soil surfaces between single trees. This unique ecosystem has been under extensive agrosilvopastoral management for centuries and is now at risk of degradation caused by overgrazing and increasing scarcity and variability of rainfall. To investigate susceptibility to wind erosion, we conducted an experimental–empirical study including wind tunnel tests and a drone-generated digital elevation model and quantified wind-erodible material on five different associated surface types by means of sediment catchers. The highest emission flux was measured on freshly ploughed surfaces (1875 g m^–2 h^–1), while older ploughed areas with a re-established crust produced a much lower emission flux (795 g m^–2 h^–1). Extensive tillage may have been a sustainable practice for generations, but increasing drought and uncertainty of rainfall now lead to an acute risk of severe soil erosion and dust production. The typical crusted surfaces characterized by residual rock fragment accumulation and wash processes produced the second highest emission flux (1,354 g m^–2 h^–1). Material collected from tree-shaded areas (933 g m^–2 h^–1) was revealed to be a considerable source of organic material, possibly affecting substrate conditions positively on a larger regional scale. The lowest flux was measured on rock fragment-covered surfaces (301 g m^–2 h^–1). The data show that open argan woodland may be a considerable source for wind erosion and dust production, depending on surface characteristics strongly related to management. An adapted management must include the conservation of argan trees to offer a promising approach to prevent severe wind erosion and dust production and mitigate possible impacts of land-use change and climate change related shifts in wind and rainfall patterns. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

不同减隔震措施下平板支座抗震性能试验研究

为探究不同减隔震措施对短边距混凝土网架平板支座的抗震性能和破坏模式的影响,分别针对不同混凝土边缘距离以及采用不同减隔震措施的四个平板支座缩尺试件进行拟静力加载试验,对平板支座破坏模式、滞回曲线、箍筋应变进行分析。试验结果表明:平板支座的运动伴随着平动和转动。当混凝土边距不足时,边缘混凝土在压剪作用下,会发生冲切破坏。开长孔支座能较好的释放水平位移,并且对锚栓约束较弱,使其受力较小,从而减轻了边缘混凝土的受力。对采用橡胶垫板的支座,混凝土边缘未发生破坏,原因是橡胶垫具有良好的变形能力,可以释放支座的位移和转角,使得边缘混凝土受力较小。因此,针对混凝土边缘距离较短的平板支座节点,为防止混凝土发生边缘破坏,可采用开长孔支座,但需要对孔长进行合理的设计。采用橡胶垫支座也可避免混凝土发生边缘破坏,橡胶垫板可按照我国相关设计规范进行设计。     

Development of detachable replaceable links for eccentrically braced frames

Eccentrically braced frames (EBFs) can be repaired after a major earthquake by replacing the links. The link replacement is not a straightforward process and is influenced by the type of the link and the amount of residual frame deformations. The past decade has witnessed the development of different types of replaceable links such as end-plated links, web connected links, bolted flange and web spliced links, and collector beam and brace spliced links. All of the developed replaceable link details, except the web connected links, are not suitable for link replacement under residual frame drift. In this paper, a detachable replaceable link detail which is based on splicing the link at its mid-length is proposed. The detail is well suited for installation under residual frame drifts. In addition, the weight and size of the members to be transported and erected are reduced significantly, thereby facilitating the replacement procedure. Performance of this proposed replaceable link is studied by conducting six nearly full scale EBF tests under quasi-static cyclic loading. The link length ratio, type of end-plated mid-splice connection, and the amount of residual drift are considered as test variables. The test results revealed that the inelastic rotation capacity of the detachable replaceable links exceeds the requirements of the AISC Seismic Provisions for Structural Steel Buildings. No failures are observed in the end-plated mid-splice connections demonstrating the potential of the proposed details. The detachable replaceable links are investigated by numerical analysis as well to further validate their applicability and to develop design recommendations.