偏心水平荷载下内藏钢桁架混凝土核心筒抗震试验研究     

常卫华  曹万林  张建伟  赵长军 《世界地震工程》2007,23(4):112-118

对两个1／6缩尺的核心筒结构模型进行了偏心水平荷载作用下的低周反复荷载试验研究，其中包括一个普通混凝土核心筒和一个内藏钢桁架混凝土组合核心筒。在试验的基础上，分析了两个试件的承载力、刚度、延性、滞回特性、耗能能力、破坏特征以及抗震机理。试验研究表明：偏心水平荷载作用下，内藏钢桁架混凝土组合核心筒比普通混凝土核心筒抗震能力显著提高。  相似文献   

Experimental and Numerical Studies on Rock Breaking with TBM Tools under High Stress Confinement   总被引：3，自引：2，他引：3  

N. Innaurato  C. Oggeri  P. P. Oreste  R. Vinai 《Rock Mechanics and Rock Engineering》2007,40(5):429-451

Summary The understanding of rock breaking and chipping due to the TBM cutter disks mechanism in deep tunnels is considered in this paper. The interest stems from the use of TBMs for the excavation of long Trans-Alpine tunnels. Some tests that simulate the disk cutter action at the tunnel face by means of an indenter, acting on a rock specimen are proposed. The rock specimen is confined through a flat-jack and a confinement-free area on one side of the specimen simulates the formation of a groove near the indenter, like it occurs in TBM excavation conditions. Results show a limited influence of the confinement stress versus the thrust increment required for breaking the rock between the indenter and the free side of the specimen. Numerical modelling of the cutter disk action on confined material has also been carried out in order to investigate further aspects of the fracture initiation. Also in this case the importance of the relative position between disk cutter and groove is pointed out.  相似文献   

航空重力测量的偏心改正     

孙中苗  夏哲仁  肖云  李迎春 《武汉大学学报(信息科学版)》2003,(Z1)

导出了航空重力测量偏心改正的实用计算公式 ,利用某航空重力测量实测数据 ,计算了位置、速度和加速度的偏心改正 ,并对垂直加速度、厄特弗斯改正、水平加速度改正和空间改正的偏心影响进行了详细分析 ,讨论了偏心改正对偏心距、姿态角的测定精度要求。  相似文献   

The geomagnetic eccentric dipole: facts and fallacies     

F. J. Lowes 《Geophysical Journal International》1994,118(3):671-679

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Shake table tests on a mass eccentric model with base isolation   总被引：1，自引：0，他引：1  

Bijan Samali  Yi Min Wu  Jianchun Li 《地震工程与结构动力学》2003,32(9):1353-1372

A mass eccentric structure is usually more seismically vulnerable than its concentric counterpart because of the coupled torsional–translational response of such structures. In this work, dynamic characteristics and response of a five‐storey benchmark model with moderate mass eccentricity were investigated using a shake table, simulating four different ground motions. The effectiveness of laminated rubber bearings (LRB) and lead‐core rubber bearings (LCRB) in protecting eccentric structures was examined and evaluated in relation to translational and torsional responses of the benchmark model. It was observed that both translational and torsional responses were significantly reduced with the addition of either a LRB or LCRB isolated system regardless of the nature of ground motion input. The LRB were identified to be more effective than LCRB in reducing model relative displacements, the relative torsional angle as well as accelerations, and therefore provided a better protection of the superstructure and its contents. On the other hand, LCRB rendered a smaller torsional angle and absolute displacement of the base isolation system, hence a more stable structural system. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

In-situ Measurements of Cutter Forces on Boring Machine at Äspö Hard Rock Laboratory Part II. Characteristics of Cutter Forces and Examination of Cracks Generated     

Z. X. Zhang  S. Q. Kou  P.-A. Lindqvist 《Rock Mechanics and Rock Engineering》2003,36(1):63-83

Summary By means of spectral analysis, the measured normal forces, tangential forces, and side forces acting on two button cutters on the boring machine in ?sp? Hard Rock Laboratory were analysed and the basic characteristics of the cutter forces were determined. After the measurements of the cutter forces, some rock core samples were taken from the bottom and the wall of the test borehole. These samples were cut, polished, and examined by means of a Scanning Electron Microscope (SEM). The lengths of the major cracks in the rock samples were measured, and a relation between the length of the median cracks and the relevant cutter forces was investigated. Received October 5, 2001; accepted June 25, 2002; Published online November 19, 2002  相似文献   

川西山区某公路拱桥变形破裂成因及处理措施探讨   总被引：2，自引：0，他引：2  

李育枢  李天斌  赵其华  王兰生 《中国地质灾害与防治学报》2003,14(2):50-55

川西山区某公路桥为一长16m的双曲偏心单孔坡条石拱桥，横跨于一小型冲沟上。东侧桥基为强—中风化钙质泥岩，西侧桥基置于一多期泥石流堆积体斜坡上(未做特殊处理)。1996年建成通车后，1997年桥身开始出现裂缝，到1999年已发展成为一座危桥，且变形破裂迹象呈进一步发展的趋势。在这个过程中，为了缓解这一趋势并彻底查清变形破裂成因，以便为危桥的全面整治提供科学依据。先后进行了桥体及周边边坡变形破裂迹象的调查、桥体三维位移长期监测、桥基灌桨加固及效果检测、周围地质环境勘察以及地质灾害危险性评价等工作。文章在大量勘察、试验以及监测数据的基础上，运用工程地质的基本分析方法．并引入结构力学理论及断裂动力学理论，对该公路拱桥的变形破裂成因进行了深入地分析和探讨。研究表明，双曲偏心拱的桥身结构不能与周边复杂的地质环境相适应是桥体变形破裂的根本原因。西侧斜坡体侧向主动土压力和两桥台间的不均匀沉降是拱桥变形破裂的起因和触发因素。而桥面间歇性动荷载作用则是促使桥体已有裂纹进一步扩展的主要原因。针对桥体的病害原因，为危桥整治提出了将原拱桥桥身结构改为对桥基变形适应性强的桥梁结构，将西侧较软弱的桥基进行灌桨加固。将两桥台用地粱连接增加桥体整体刚度并在西桥台设置与竖向支撑相结合的综合处理措施。  相似文献   

锥形聚晶金刚石复合片齿破岩特征与机制研究     

熊超  黄中伟  王立超  史怀忠  赫文豪  陈振良  李根生 《岩土力学》2023,(8):2432-2444

锥形聚晶金刚石复合片(polycrystalline diamond compact,PDC)齿是一种具有较强抗冲击性和耐磨性的新型PDC齿,在坚硬、强研磨性和软硬交错地层中取得了非常好的钻井提速效果。为了揭示锥形齿破碎硬岩机制,开展锥形齿破碎花岗岩试验与数值模拟研究,分析了切削深度和前倾角对锥形齿切削力和破岩比能的影响规律,采用高速摄像机和透明K9玻璃观测了锥形齿作用下岩屑形成过程及微裂纹萌生与扩展过程,通过数值模拟分析了破岩过程中岩石应力响应与损伤演化特性,结合对切削槽和大尺寸块体岩屑表面形貌及断口微观特征分析,建立了锥形齿破碎花岗岩机制模型。结果表明,锥形齿破碎花岗岩的过程可以分为挤压成核和块体崩裂两个阶段,前倾角对岩石破碎过程影响较小,切削深度的影响显著;锥形齿周围的裂纹主要由压实核、纵向裂纹和横向裂纹组成,纵向裂纹和横向裂纹扩展的最大深度分别为切削深度的6.69倍和4.53倍;齿尖周围压应力集中,岩石发生压剪破坏,压应力区外围形成弧形条带状拉应力区,并在齿尖及压应力区边界处诱导出拉伸微裂纹;微裂纹向齿前扩展形成弧形拉伸主裂纹,发生块体岩屑崩裂,提高破岩效率,向岩石内部扩展劣化...  相似文献   

基于新表面理论的TBM破岩效率评价指标     

闫长斌  李高留  陈健  李严  杨延栋  杨风威  杨继华 《岩土力学》2023,(4):1153-1164

岩碴是岩-机作用的直接产物,也是评价隧道掘进机（TBM）破岩效率和优化TBM掘进参数的有效指标。依托兰州水源地建设工程和龙岩万安溪引水工程,开展不同岩性条件下TBM岩碴筛分试验,得到了岩碴粒径分布规律。基于新表面理论,从滚刀破岩能量转化角度出发,提出了一种新的TBM破岩效率评价指标。基于岩碴粒径分布规律和TBM掘进参数统计,探讨了新表面理论指标与比能、岩碴粗糙度指数之间的关系,指出了新表面理论指标在反映岩碴破碎程度和评价TBM破岩效率方面的优势。对新表面理论指标与TBM掘进推力以及刀间距s与贯入度p的比值进行回归分析,得到了硬岩（围岩等级为Ⅱ级）和软岩（围岩等级为III级）掘进条件下的TBM最优掘进推力和s/p取值区间。研究表明：（1）新表面理论指标符合岩石破碎学原理,可准确评价TBM破岩效率。岩碴越是破碎,新表面理论指标越大,掘进能耗越高,此时TBM破岩效率相对较低。（2）新表面理论指标与比能、岩碴粗糙度指数均具有良好的线性相关关系。岩碴越是破碎,破碎单位体积岩石的能量消耗越大,新表面理论指标越大,对应的粗糙度指数越小。软岩掘进条件下TBM掘进比能低于硬岩,而岩碴破碎程度高于硬岩。（...  相似文献   

关于偏心荷载下地基承载力的验算方法     

宋二祥  陈星屹  林世杰 《岩土力学》2022,43(7):1925-1932

针对偏心荷载作用下的地基承载力验算,以条形基础为例,介绍了Meyerhof提出的考虑荷载偏心的地基承载力计算方法,并通过与有限元上下限极限分析这一极限荷载精细数值计算方法的比较验证了其正确性和准确性。所考虑的地基既包括排水条件下的一般地基,也包括不排水强度随深度近似线性增大的饱和黏性土地基。依据有关机理深入分析了基础埋深对偏心荷载下地基承载力计算精度的影响,明确了可以考虑基础埋深有利作用的偏心距上限。进而采用本课题组所提出计算地基承载力的改进公式,通过计算并结合理论分析比较了国内规范验算方法与按Meyerhof方法的验算,表明采用后一方法更为合理。  相似文献