采用有限元等效体力方法数值分析火山区岩浆压力变形源——以长白山火山为例          下载免费PDF全文

黄禄渊  程惠红  张怀  高锐  石耀霖 《地球物理学报》1954,63(11):4050-4064

火山区岩浆压力变形源的反演计算采用解析方法存在难以考虑地形的限制,采用传统有限元方法则存在网格依赖和计算量大的问题,反演过程中每一次正演由于岩浆房位置和大小变化都需要重新生成一次网格,耗费巨大的计算量和网格生成时间.为了克服上述问题,首次在长白山火山区使用"有限元等效体力"方法考虑地形影响反演地下岩浆压力变形源,计算岩浆应力扰动对周边断层稳定性的影响.在火山区地下压力变形源引起的地表形变计算中,地表地形影响不可忽略.埋深越浅,地表最大径向位移u_r所在的位置越靠近岩浆囊中心.当坡度达到30°时,最大垂向位移u_z所在位置不再位于岩浆囊正上方.椭球状岩浆囊压力源可以较好地模拟长白山火山地区2002—2003年间的GPS和水准测量.岩浆房扰动应力场和区域构造应力场的叠加有可能造成天池西部近EW向,天池北部以NW-NNW向为主的现今应力方向.岩浆房压力源引起的库仑应力变化有利于天池火山口NW向震群在空间上主要分布于火山口的西南和东北部.  相似文献   

Multicriteria to estimate the environmental risk of sediment from the Obedska Bog (Northern Serbia), a reservation area on UNESCO's list     

《国际泥沙研究》2020,35(5):527-539

The objective of this current study is to compare related sediment legislation standards and norms to the diversity and influence of anthropogenic and natural (geogenic) sources of pollution in the investigated fluvial relief test site region of the Obedska bog. All metals (nickel (Ni), zinc (Zn), cadmium (Cd), copper (Cu) and lead (Pb) except chromium (Cr)) and arsenic (As) have higher values than the Upper Continental Crust (UCC) for loess sediment. Several sharp leaps in the enrichment factor (r) suggested “indicators of anthropogenic metal pollution” for Cd, Cu (r > 5.0) and Zn, Ni (r > 1.0) for this region. In addition, the Chemical Proxy of Alteration (CPA, 60–95) from the unique Jadar block terrane and neighbouring representative catchment areas, confirmed moderate to higher intensity of alteration. Principal Component Analysis/Factor Analysis (PCA/FA) and cluster analysis suggest that Ni, Zn, Cu and Cd are derived from several anthropogenic sources, whereas As is convincingly of geogenic origin, and Pb and Cr exhibit dual origins. The sum of 16 U. S. Environmental Protection Agency Polycyclic Aromatic Hydrocarbons (EPA PAHs) indicated heterogenic sources, but minor effects to biota. The results of the current investigation indicated intensive and highly diffuse sources of pollution in this United Nations Educational, Scientific and Cultural Organization [UNESCO's] region. The outcomes indicate that Cu should be added to the European Union [EU] watch list of emerging contaminants.  相似文献   

Quasi-static crack models and the frictional stress threshold criterion for slip arrest     

M. Bonafede  M. Dragoni  E. Boschi 《Geophysical Journal International》1985,83(3):615-635

Summary. Two-dimensional crack problems in elastic homogeneous isotropic media are considered which describe rupture over a fault surface characterized by non-uniform stress drop. Solutions can be found in which the stress field is finite at the crack tips and the rupture surface is not assigned a priori , but is part of the solution. These crack models are found to be consistent with the frictional stress threshold criterion for slip arrest over pre-existing fault surfaces. A crack is found to stop when its contribution to the stress field is opposite to the stress drop at the crack tips. The quasi-static propagation of a crack up to the arrest configuration is studied in terms of the minimum energy principle. The crack spontaneously propagates in such a way as to make the value of the stress intensity factor at one tip equal to the value at the other tip. Furthermore a tip propagating in a region with higher friction is found to move more slowly than the other tip propagating in a region with lower friction. Simple criteria for fracture arrest are derived, in terms of a properly averaged stress drop. Piecewise constant stress drop profiles are explicitly considered yielding a variety of solutions which can be applied to modelling asperities or barriers over a fault plane. The evaluation of the amount of the energy released during the quasi-static crack propagation shows that stopping phases cannot be efficiently radiated if the crack comes to rest in a low friction region.  相似文献   

Applications of graph theory to gross error detection for GPS geodetic control networks   总被引：1，自引：0，他引：1  

Samwel Simon Katambi 《地球空间信息科学学报》2002,5(4):26-31

1　ＧｒａｐｈｔｈｅｏｒｙａｎｄｄｅｆｉｎｉｔｉｏｎｓＡｇｒａｐｈＧｃｏｎｓｉｓｔｓｏｆｐｏｉｎｔｓ (ＮＯＤＥＳ)ａｎｄｌｉｎｅｓ (ＥＤＧＥＳ)ｃｏｎｎｅｃｔｉｎｇｔｈｅｓｅｐｏｉｎｔｓ .Ｔｈｅｐｏｉｎｔｓａｒｅｃａｌｌｅｄｎｏｄｅｓａｎｄｌｉｎｅｓａｒｅｅｄｇｅｓ .Ａｄｉｒｅｃｔｅｄｇｒａｐｈｉｓａｇｒａｐｈｉｎｗｈｉｃｈｔｈｅｅｄｇｅｓｃｏｎ ｎｅｃｔｉｎｇｔｈｅｎｏｄｅｓａｒｅｓｐｅｃｉｆｉｅｄ .Ａｔｒｅｅｉｓａｃｏｎｎｅｃｔｅｄｇｒａｐｈｗｉｔｈｏｕｔａｎｙｌｏｏｐ .Ａｌｏｏｐｉｓａｃｌｏｓ…  相似文献   

Development of marine water quality criteria for the USA   总被引：6，自引：0，他引：6  

Russo RC 《Marine pollution bulletin》2002,45(1-12):84-91

The US Environmental Protection Agency has developed guidelines for deriving numerical national water quality criteria for the protection of aquatic organisms and their uses. These guidelines provide the method for deriving water quality criteria, including minimum data base requirements, data evaluation procedures, and calculations. The guidelines have been in place for a long time, and states have used them to derive water quality standards for their water bodies. More recent efforts have been directed towards the development of technical guidance based on the concept that bioassessment and biocriteria programs for estuaries and near coastal waters are interrelated and are critical components of comprehensive water resource protection and management. This is a holistic approach to protection and management, integrating biological assessments into traditional chemical and physical evaluations and augmenting the established water quality criteria. The method for deriving water quality criteria and the approach for biocriteria development for marine systems are described.  相似文献   

Studies on seismic reduction of story‐incresed buildings with friction layer and energy‐dissipated devices     

Hong‐Nan Li  Yong‐Wei Yin  Su‐Yan Wang 《地震工程与结构动力学》2003,32(14):2143-2160

A new type of energy‐dissipated structural system for existing buildings with story‐increased frames is presented and investigated in this paper. In this system the sliding‐friction layer between the lowest increased floor of the outer frame structure and the roof of the original building is applied, and energy‐dissipated dampers are used for the connections between the columns of the outer frame and each floor of the original building. A shaking table test is performed on the model of the system and the simplified structural model of this system is given. The theory of the non‐classical damping approach is introduced to the calculation analyses and compared with test results. The results show that friction and energy‐dissipated devices are very effective in reducing the seismic response and dissipating the input energy of the model structure. Finally, the design scheme and dynamic time‐history analyses of an existing engineering project are investigated to illustrate the application and advantages of the given method. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

The Time-Dependent Reduction of Sliding Cohesion due to Rock Bridges Along Discontinuities: A Fracture Mechanics Approach   总被引：1，自引：3，他引：1  

J. Kemeny 《Rock Mechanics and Rock Engineering》2003,36(1):27-38

Summary In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures. Received November 5, 2001; accepted July 24, 2002; Published online November 19, 2002  相似文献   

Finite element modelling of frictional instability between deformable rocks   总被引：1，自引：0，他引：1  

H. L. Xing  A. Makinouchi 《国际地质力学数值与分析法杂志》2003,27(12):1005-1025

Earthquakes are recognized as resulting from a stick–slip frictional instability along faults. Based on the node‐to‐point contact element strategy (an arbitrarily shaped contact element strategy applied with the static‐explicit algorithm for modelling non‐linear frictional contact problems proposed by authors), a finite element code for modelling the 3‐D non‐linear friction contact between deformable bodies has been developed and extended here to analyse the non‐linear stick–slip frictional instability between deformable rocks with a rate‐ and state‐dependent friction law. A typical fault bend model is taken as an application example to be analysed here. The variations of the normal contact force, the frictional force, the transition of stick–slip instable state and the related relative slip velocity along the fault between the deformable rocks and the stress evolution in the total bodies during the different stages are investigated, respectively. The calculated results demonstrate the usefulness of this code for simulating the non‐linear frictional instability between deformable rocks. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

浙江省仙居县地质灾害调查与区划   总被引：4，自引：0，他引：4  

曹恺  孟高头等 《地球科学》2002,27(2):217-221

结合地质灾害调查与区划项目中“以人为本”的思想,在调查仙居县具体地理情况、地质环境的基础上，分析了对地质灾害起控制作用的因素，建立了敏感因子评估模型，由于地质灾害致灾害因素的复杂性及不确定性，引进了模糊数学综合评判法，对地质灾害进行区划，依据区划结果在仙居县土地规划提出了切实可行的建议。  相似文献   

1973年炉霍大地震(Ms=7.6)最大余震(Ms=6.3)的库仑破裂应力触发   总被引：15，自引：0，他引：15  

刘桂萍  傅征祥 《中国地震》2002,18(2):175-182

1973年2月6日在四川省炉霍发生Ms7.6大地震，震后在震中周围出现丰富的余震，其最大余震（Ms6.3）发生在鲜水河断裂和玉树－甘孜断裂之间的正断层活动区内。本文根据震源机制解，地表破裂，同震位错分布，地震地质构造等资料，建立炉霍走大地震破裂的弹性位错模型，计算该大地震在周围正断层滑动方向上引起的库仑破裂应力变化（△CFS），结果表明，最大余震发生在库仑破裂应力增加（△CFS＞0）的地区，△CFS＝4.5MPa,因此认为，最大余震可能是由主震引起的库仑破裂应力变化触发的。  相似文献