俯冲带地震诱发机制:研究进展综述   总被引：4，自引：0，他引：4  

邵同宾  嵇少丞 《地质论评》2015,61(2):245-268

俯冲带作为地球循环体系的关键部位,具有构造活跃、地震多发以及地质条件复杂等特征。基于震源位置,俯冲带地震既可划分为板间和板内地震,也可分为浅源、中源和深源地震。俯冲带内的浅源地震包括板间地震和浅源板内地震,而中源和深源地震皆属于板内地震。在地球浅部,温度与压力低,浅源地震是由岩石发生脆性破裂或沿着先存断层发生不稳定摩擦滑移造成的。随着深度增加,温度和压力的增加使得流行于浅部的脆性和摩擦行为在无水条件下被强烈抑制,岩石从而表现为可抑制地震的韧性行为,使得中-深源地震的诱发机制有别于常规的脆性行为。随着研究的逐渐深入,人们了解到中源地震的诱发机制主要是脱水或与流体相关的致脆以及塑性剪切失稳,而深源地震的成因主要是相变致裂。然而,中-深源地震很可能是两种或两种以上机制共同作用的结果。例如,在中源深度既可能是流体相关的致脆导致脱水源区的脆性围岩产生地震,亦可能是脱水的蛇纹岩本身可能在流体孔隙压的作用下作粘滑滑移,而前者比后者更为重要。孕震带宽度大于"反裂隙模型"预测的亚稳态橄榄石冷核宽度的深源地震可能是由第一阶段的相变致裂和第二阶段的塑性剪切失稳诱发,而孕震带的实际宽度与预测宽度相当的深源地震则可能仅由相变致裂引起。只要过渡带内名义无水矿物中的结构水能释放出来,脱水致脆同样可能触发一些深源地震;而塑性剪切失稳不仅能在中-深源地震触发后的扩展阶段起着主导作用,而且还能单独触发一些中-深源地震,因此能够解释大多数反复发生的中-深源地震活动。  相似文献   

Experimental evaluation of shear strength behaviour of plastic and non-plastic silts     

A. Usmani  K.G. Sharma  A. Nanda 《Geomechanics and Geoengineering》2015,10(3):174-181

Silt is available in many parts of the world in combination with sands and clays. However, due to lack of clear understanding of its engineering behaviour, most of the time it is interpreted in terms of either sands or clays. Structures that are usually built on silty soils are designed to take into account design procedures developed for sandy or clayey soils. Presence of silts in combination with varying amount of sand and clays produces silt that is either plastic or non-plastic in nature. Silt is available in and around the Delhi region, in a majority mixture along with fine sands, which is non-plastic in nature. On the other hand silty deposits found in offshore Bombay High region are found in abundance along with significant amounts of clays and are termed as plastic silts. In this paper a comparison of the stress-strain behaviour of plastic and non-plastic silts is carried out under triaxial compression loading during both drained and undrained conditions. Two representative samples each from Delhi and Bombay High regions were considered for this comparison and results of stress-strain under four sets of confining pressure are discussed in detail. It is observed from this study that behaviour of silts is mainly dependent on the composition and structure of the resultant soil matrix. It is concluded from the results that shear strength parameters as well as volume change/pore pressure response of silty soils is dominated by the constituent soil present along with the silt. It is seen from the comparative behaviour of non-plastic and plastic silts that the presence of sand and clays has a governing effect on pore pressure development and the resultant friction angle. The study also corroborated that the nature of silt is transitional both in the case of plastic and non-plastic forms.  相似文献   

东昆仑造山带东段哈图沟–清水泉–沟里韧性剪切带塑性变形及动力学条件研究   总被引：1，自引：0，他引：1  

李小兵  裴先治  陈有炘  刘成军  李佐臣  李瑞保  陈国超  魏博 《大地构造与成矿学》2015,(2)

东昆仑造山带东段哈图沟–清水泉–沟里韧性剪切带记录了多个旋回的造山作用,本文通过对韧性剪切带中石英c轴组构和显微构造特征测试分析,探讨东昆仑造山带东段陆块间俯冲拼合及地壳伸展减薄的形成机制。结果显示,韧性剪切带变形温度介于380~650℃之间,形成环境为中–高绿片岩相到低角闪岩相,剪切带内差异应力值介于173~509 MPa之间,应变速率介于6.93×10–14~1.43×10–8 s–1之间,主体为10–11~10–10 s–1,显示韧性剪切带变形是快速俯冲作用下的产物,越靠近东昆仑造山带东段东昆中断裂带其变形温度、差异应力值及相应的应变速率值越大,表明东昆仑造山带东段韧性剪切变形中心为东昆中断裂带。利用不同方法所计算出的韧性剪切带运动学涡度值,显示韧性剪切带早期瞬时运动学涡度(0.56~1)对应于东昆仑造山带东段东昆南与东昆仑造山带东段东昆北陆块间俯冲的初始阶段,中后期运动学涡度(0.25~0.91)应当对应于东昆南与东昆北陆块间的俯冲碰撞阶段,最晚期的C′瞬时运动学涡度(0.19~0.51)则对应于后造山的伸展阶段。通过石英c轴组构结合其宏微观构造特征,认为东昆中构造带至少经历了3个期次的构造运动,分别为加里东晚期的逆冲兼左行走滑剪切作用、晚海西–印支期的逆冲兼右行走滑剪切作用和燕山早期及之后的脆韧性–脆性的左行走滑剪切作用。  相似文献   

克拉玛依科博馆倾斜结构抗震设计     

赵楠 《地震工程与工程振动》2011,31(2):111-117

结合克拉玛依市科技博物馆工程,对超限倾斜结构设定性能设计目标,并针对性能目标提出抗震措施及抗震构造措施.考虑结构材料的非线性属性,采用静力非线性分析方法,分析倾斜框架-剪力墙结构在地震作用下的响应,尤其是结构在罕遇地震作用下的非线性动力特性.结果表明,结构在罕遇地震下也是安全可靠的,剪力墙尚处在弹性范围,未出现塑性铰,...  相似文献   

Experimental study and constitutive modelling of elasto‐plastic damage in heat‐treated mortar     

Xiao‐Ting Chen  J. F. Shao  C. A. Davy  F. Skoczylas 《国际地质力学数值与分析法杂志》2010,34(4):357-382

This study investigates the effect of a heat‐treatment upon the thermo‐mechanical behaviour of a model cement‐based material, i.e. a normalized mortar, with a (w/c) ratio of 0.5. First, a whole set of varied experimental results is provided, in order to either identify or validate a thermo‐mechanical constitutive model, presented in the second paper part. Experimental responses of both hydraulic and mechanical behaviour are given after different heating/cooling cycling levels (105, 200, 300, 400^°C). The reference state, used for comparison purposes, is taken after mass stabilization at 60^°C. Typical uniaxial compression tests are provided, and original triaxial deviatoric compressive test responses are also given. Hydraulic behaviour is identified simultaneously to triaxial deviatoric compressive loading through gas permeability K_gas assessment. K_gas is well correlated with volumetric strain evolution: gas permeability increases hugely when ε_v testifies of a dilatant material behaviour, instead of contractile from the test start. Finally, the thermo‐mechanical model, based on a thermodynamics approach, is identified using the experimental results on uniaxial and triaxial deviatoric compression. It is also positively validated at residual state for triaxial deviatoric compression, but also by using a different stress path in lateral extension, which is at the origin of noticeable plasticity. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

海涂围垦工程中悬挂式爆破挤淤基础处理技术探讨   总被引：1，自引：0，他引：1  

王文杰  赵微人  郭加根 《海岸工程》2010,29(3):51-56

沿海软土地基围涂工程中悬挂式爆破挤淤基础处理断面结构设计中遇到的最大难题是对腰宽的处理,腰宽太窄则工后沉降大,反之,则断面石方量增大,投资增加,因此,试图通过工程实例说明悬挂式爆破挤淤基础处理断面设计及工程实施过程中遇到的问题及对策措施。  相似文献   

强震下四边钢柱支承单层柱面网壳弹塑性地震响应研究     

刘云涛  李海旺 《地震学刊》2014,(6):687-692

采用集中塑性铰理论和SAP2000结构分析软件,对某体育练习馆（钢柱周边支承单层柱面网壳）整体结构进行了强震下弹塑性地震响应分析。分析中考虑了几何和材料双重非线性影响,获得了节点位移响应、杆件塑性铰的分布特征和结构的整体变形与失效形态,并评定了整体结构在强震下的极限承载力与失效类型。结果表明：该结构在强震下的失效界限地震加速度峰值为1260gal,最大竖向变形为短向跨度的1/163,满足＂避难与救灾建筑结构＂的抗震性能设防要求;结构的失效类型为动力失稳破坏,临界失效时出现塑性铰的杆件较少,结构塑性发展程度不充分;由整体稳定控制的单层柱面网壳在满足稳定承载力的要求下具有较大的抗震潜能。  相似文献   

基于Hoek-Brown准则的隧洞围岩变形研究   总被引：1，自引：0，他引：1  

温森  杨圣奇 《岩土力学》2011,32(1):63-69

由于在许多实际条件下,比如节理岩体中,线性的M-C准则不太适用,非线性的Hoek-Brown比较适用,因此,可以尝试使用这一非线性屈服准则对洞室变形进行研究。研究隧洞变形时,将围岩分为弹性区、应变软化区、塑性流动区。采用Hoek-Brown准则和非关联流动法则对洞室变形进行了理论推导;软化区域围岩参数随着塑性变形增加而变化,解析法难以求得应力,采用龙格－库塔方法进行数值计算,求解得到塑性软化区和流动区半径,并最终求得洞室变形。通过算例计算表明,在不考虑软化区和流动区时,方法和Carranza-Torres计算结果相差甚小;随着原岩应力的增加,膨胀角对洞室变形的影响增大。  相似文献   

FRP约束混凝土矩形短柱的延性分析   总被引：3，自引：0，他引：3  

魏洋  吴刚  吴智深  顾冬生  郭正兴 《地震工程与工程振动》2009,29(3)

将已有混凝土柱延性的定义、纤维截面模型及等效塑性铰方法应用于纤维增强复合材料(FRP)约束矩形混凝土试件的延性分析,通过FRP约束矩形混凝土应力-应变关系考虑FRP约束的影响,计算结果与试验结果符合较好。同时,对FRP约束混凝土矩形柱延性的主要影响参数进行了分析,该方法可以进一步用于FRP约束混凝土试件延性的定量参数研究。  相似文献   

Performance-based concept on seismic evaluation of existing bridges   总被引：1，自引：0，他引：1  

W.Phillip Yen 《地震工程与工程振动(英文版)》2009,8(1):127-135

Conventional seismic evaluation of existing bridges explores the ability of a bridge to survive under significant earthquake excitations. This approach has several major drawbacks, such as only a single structural performance of near collapse is considered, and the simplified approach of adopting strength-based concept to indirectly estimate the nonlinear behavior of a structure lacks accuracy. As a result, performance-based concepts that include a wider variety of structural performance states of a given bridge excited by different levels of earthquake intensity is needed by the engineering community. This paper introduces an improved process for the seismic evaluation of existing bridges. The relationship between the overall structural performance and earthquakes with varying levels of peak ground acceleration (PGA) can successfully be linked. A universal perspective on the seismic evaluation of bridges over their entire life-cycle can be easily obtained to investigate multiple performance objectives. The accuracy of the proposed method, based on pushover analysis, is proven in a case study that compares the results from the proposed procedure with additional nonlinear time history analyses.  相似文献