Mechanisms to limit higher mode effects in a controlled rocking steel frame. 1: Concept,modelling, and low‐amplitude shake table testing

Controlled rocking steel frames have been proposed as an efficient way to avoid the structural damage and residual deformations that are expected in conventional seismic force resisting systems. Although the base rocking response is intended to limit the force demands, higher mode effects can amplify member design forces, reducing the viability of the system. This paper suggests that seismic forces may be limited more effectively by providing multiple force‐limiting mechanisms. Two techniques are proposed: detailing one or more rocking joints above the base rocking joint and providing a self‐centring energy dissipative (SCED) brace at one or more levels. These concepts are applied to the design of an eight‐storey prototype structure and a shake table model at 30% scale. A simple numerical model that was used as a design tool is in good agreement with frequency characterization and low‐amplitude seismic tests of the shake table model, particularly when multiple force‐limiting mechanisms are active. These results suggest that the proposed mechanisms can enable better capacity design by reducing the variability of peak seismic force demands without causing excessive displacements. Similar results are expected for other systems that rely on a single location of concentrated nonlinearity to limit peak seismic loads. Copyright © 2012 John Wiley & Sons, Ltd.     

Structural controls on a geothermal system in the Tarutung Basin,north central Sumatra

The Sumatra Fault System provides a unique geologic setting to evaluate the influence of structural controls on geothermal activity. Whereas most of the geothermal systems in Indonesia are controlled by volcanic activity, geothermal systems at the Sumatra Fault System might be controlled by faults and fractures. Exploration strategies for these geothermal systems need to be verified because the typical pattern of heat source and alteration clays are missing so that conventional exploration with magnetotelluric surveys might not provide sufficient data to delineate favorable settings for drilling. We present field geological, structural and geomorphological evidence combined with mapping of geothermal manifestations to allow constraints between fault dynamics and geothermal activity in the Tarutung Basin in north central Sumatra. Our results indicate that the fault pattern in the Tarutung Basin is generated by a compressional stress direction acting at a high angle to the right-lateral Sumatra Fault System. NW–SE striking normal faults possibly related to negative flower structures and NNW-SSE to NNE-SSW oriented dilative Riedel shears are preferential fluid pathways whereas ENE–WSW striking faults act as barriers in this system. The dominant of geothermal manifestations at the eastern part of the basin indicates local extension due to clockwise block rotation in the Sumatra Fault System. Our results support the effort to integrate detailed field geological surveys to refined exploration strategies even in tropical areas where outcrops are limited.     

裸露岩溶区地下河管道综合地球物理方法探测研究

本文选取桂林市海洋乡裸露岩溶区地下河管道分别进行了可控源音频大地电磁法、三极电测深法和充电法试验对比研究,其综合成果得到了钻探验证.试验研究表明,充电法对具有出口、进口或天窗的地下暗河定位追踪准确,效果明显.可控源音频大地电磁法探测深度大,横向分辨率高,对寻找深部构造破碎带具有独特的优势.三极测电深法受场地条件、高阻围岩和地形起伏影响较大,不能满足对地下暗河的定位要求.     

河南新安电厂冷却塔控制爆破拆除技术

控制爆破技术在城市改造、楼房基础以及高大构筑物的拆除领域得到了广泛应用。介绍了采用控制爆破技术成功地爆破拆除河南省新安电厂80 m高冷却塔的工程实例。     

分布式电磁探测系统在深部地下水资源勘查中的应用

可控源音频大地电磁法（CSAMT）是一种有效的地下深部资源勘探方法,但现有仪器分段分时的工作方式使得其观测精度受不同排列观测条件差异的影响。为了提高测量精度和效率,研制了一种实现整条测线多点同步观测的分布式电磁探测系统。系统由级联式大功率发射系统和分布式多通道接收系统组成,通过移动发射源位置实现CSAMT和激发极化法2种测量功能;仪器采集的多道原始数据经过干扰噪声抑制后提取出反演参数。利用该系统在吉林松江河地区开展了深部地下水资源勘查,并与同类仪器GDP32II的勘探结果进行了对比。结果表明：分布式电磁探测系统多点同步观测方式不但提高了工作效率,而且有效地克服了时变性、区域性外界噪声产生的横向异常影响。根据勘查结果在该地区成功预测了深部地下水的有利赋存位置并得到了钻井验证。     

Larval shell development of the toheroa,Paphies ventricosa (Gray, 1843) (Mactracea: Mesodesmatidae)

The larval shells of Paphies ventricosa, reared to settlement in the hatchery, are similar in longitudinal profile to shells of some other mactracean larvae; the umbo‐stage larval shells are nearly round with the anterior margin less broadly curved than the posterior margin, the anterior end is longer than the posterior end, and the umbo is broadly rounded. Straight‐hinge larvae had total lengths up to 149 μm, and total heights up to 126 μm, and umbo larvae had total lengths up to 320 μm, and total heights up to 282 μm. The larvae settled in about 22 days at a size of about 270 μm. The larval hinge structure bears some similarities to those of other mactracean larvae.     

北京张坊地区岩溶地下水运移富集的构造控制分析

北京西山张坊地区碳酸盐岩集中分布,地下水赋存于复杂的构造裂隙网络中,形成岩溶裂隙水。文章从构造空间分布的属性和规律出发,分析了在张坊地区褶皱构造格架控制的岩溶水文地质单元内,地下水赋存富集规律与多期构造演化产生的一系列北东-北西向、南北向断裂及裂隙网络的制约关系。研究表明,本区断裂经历了侏罗世逆冲推覆活动与白垩世的伸展构造,先压后张两期构造作用的叠加,形成了多条区域性断裂,其导水性能大为增强。裂隙中频度较大的NE和NW向是优势裂隙,表现出构造节理的共轭特征,多高倾角或直立,导致雨水的直接下渗;在裂隙交汇带构成了区域地下水的径流通道和存储空间,控制了白岱、甘池-长沟、高庄-石窝富水区的形成以及岩溶泉的出露,具有重要的供水意义。      

近30年来长江口水下三角洲地形演变与受控因素分析

利用长江口1982-2010年间4个年份的高精度实测地形数据、大通站输沙量数据以及河口工程建设信息等,分3个阶段研究了长江口整体冲淤规律、不同分区冲淤变化时空差异、重点断面垂向冲淤特征、水下三角洲重要区域 (崇明东滩、横沙浅滩、九段沙以及南汇东滩) 的演变趋势与受控因素。结果表明：(1) 近30年长江口整体上表现为略微冲刷,冲刷面积占51.83%,在3个阶段中呈现出“冲刷—淤积—再冲刷”的冲淤演化态势,且冲淤变化时空差异显著,仅长江北港区为持续冲刷。(2) 崇明东滩和横沙浅滩东侧和北侧、九段沙北侧以及南汇东滩的5 m以浅区域以垂向淤积为主,而崇明东滩和横沙浅滩南侧、九段沙东侧和南侧的5 m以浅区域则以垂向冲刷为主。(3) 长江口重要区域2 m和5 m等深线包络面积整体上是不断增加的,1982-2010年时段内年均增加量分别为10.42 km²/a和7.99 km²/a,但各分区则表现不一致;10 m等深线包络面积在整体上及各个分区内均表现为明显减小;15 m等深线包络面积变幅较小,基本保持稳定状态;(4) 受河口工程建设影响,仅崇明东滩水下三角洲等深线包络面积减小的趋势与大通站输沙量减少趋势相同。主要结论：从长江口水下三角洲等深线包络面积和分布形态的变化看,基于目前上游输沙量持续减少的宏观自然背景下,大规模的河口工程建设对近年来长江口水下三角洲演变的控制作用日益明显。     

车西洼陷西北陡坡沙三下亚段地震相控反演砂砾岩储层预测

胜利油田的油气勘探方向逐渐由构造油藏向隐蔽油藏转变,砂砾岩油气藏成为非常重要的勘探目标,随着勘探程度的不断提高和新技术的不断应用,断陷湖盆的陡坡带成为重要的关注目标。地震相控反演充分利用了地震相界面对宏观地质体或岩性体的控制作用,将目标地层分成具有不同沉积特征的沉积单元,根据低频背景约束地震道外推反演中每个采样点的初值范围,同时控制反演时窗的大小,使反演结果具有明确的地质意义。针对车西洼陷陡坡带砂砾岩储层成因多、储层相变快、砂体描述困难等问题,在沉积相精细划分、储层物性分析、测井信息约束下,应用地震相控反演,预测古近系沙河街组三段下(沙三下)亚段陡坡带低孔低渗砂砾岩储层“甜点”分布,在扇辫状水道中、远端最有利的优质储层发育相带划分出4个“甜点区”。预测结果表明：砂砾岩体识别在垂向上达砂组级别,局部可达小层级别;横向上,不同成因类型砂体区分明显,可较好地识别出近岸水下扇、滑塌扇等砂砾岩储层,明显提高了断陷盆地陡坡带砂砾岩储层“甜点区”预测精度。     

由精密控制人工震源观测到的绵竹5.6级地震前后波速变化

地震危险区断层的应力状态变化及其精确测量一直是地球物理学关注的热点问题之一,主动震源探测技术的发展为解决上述问题带来了可能.汶川大地震后,结合汶川地震断裂带科学钻探,在四川省绵竹市九龙镇--跨越龙门山断裂带前山断裂,利用10 t精密控制人工震源进行了连续监测试验,在试验观测期间的2009年6月30日凌晨2时3分,当地发生了M_s5.6级地震,地震前后观测数据的对比分析表明,该地震发生前后,穿过断裂带的直达S波走时发生了时延为5~9 ms的微弱变化,射线路径上的平均波速相对下降了约0.3%,该时延主要是由地震同震效应引起的断裂带内应力调整和物性变化造成的.所使用的精密控制人工震源性能稳定,适于开展断层监测.这一结果对于发展断裂带主动震源动态监测技术具有重要意义.