六合体应变干扰因素与地震短临异常特征研究   总被引：1，自引：0，他引：1       下载免费PDF全文

郑江蓉  徐徐  王俊  江昊琳 《地震工程学报》2011,33(1):84-90

利用江苏省南京市六合地震台钻孔体应变2003年1月1日至2008年12月31日的数字化观测资料,对气压和降雨这二种主要干扰因素的基本变化规律进行分析,讨论了发生在该台预报效能范围内的3次中强地震的短临异常特征.结果表明:气压变化在各个季节对观测值均有较大的影响,以短周期的正相关干扰影响为主,在时间上往往表现为准同步,相关系数能达到0.6～0.7以上;降雨对体应变的影响与降雨过程、降雨量及降雨时间等有密切的关系,持续降雨只有积累到一定程度才能促成固体潮畸变,这一过程虽较复杂,但仍有一定的规律可循.六合体应变对区域内中强地震有1～2月的突出短临异常变化.  相似文献   

自由场典型液化特征数值模拟试验     

何剑平  陈卫忠 《地震工程与工程振动》2011,31(2):162-169

应用FLAOD实现自由场液化数值模拟试验.试验结果验证了砂土液化典型特征:超静孔隙水压升高,有效应力降低,体积压缩积累增大.证实了液化的隔振作用:砂土在液化状态变为流体,不能传递剪力,液化时砂土位移、速度、加速度振幅显著降低,剪应力降低,动水向上渗流,土体向下沉降,水平残留不可恢复位移.球压应力、有效压应力、动水压力满...  相似文献   

福州地震台TJ-2型体积式应变仪安装及注水试验     

林国元 《华北地震科学》2011,29(1):53-56

在安装福州地震台TJ-2型体积式应变仪过程中,发现存在钻孔选点与观测室分开考虑等问题,提出一些建议。井孔注水试验结果揭示,该井孔探头顶部可能存在一个与探头近距离的含水层干扰。初步对气压、水位、降雨影响进行分析。  相似文献   

太康4．7级地震前地震活动图像和趋势分析     

林眉  刘希强  郑建常  徐长朋  冀东普 《地震地磁观测与研究》2011,32(4):7-11

对苏、鲁、皖、豫交界地区地震活动进行研究,指出该区2006年10月-2010年10月出现一个长轴约230km的3级地震空区。该空区及附近地区存在多项中期异常,即ML≥3地震活动具有频度高、能量强,中等地震震中空间分布相对集中及低b值等。讨论认为,苏、鲁、皖、豫交界地区存在多项中期异常,与2004年10月24日太康4．7级地震的强度不匹配,未来具有发生中强以上地震的危险。  相似文献   

Performance of mixed and enhanced finite elements for strain localization in hypoplasticity     

B. T. Trinh  K. Hackl 《国际地质力学数值与分析法杂志》2012,36(9):1125-1150

Displacement and mixed finite element formulations of shear localization in materials are presented. The formulations are based on hypoplastic constitutive laws for soils and the mixed enhanced treatment involving displacement, strain and stress rates as independently varied fields. Included in these formulations are the standard displacement method, the three‐field mixed formulation, the enhanced assumed strain method and the mixed enhanced strain method. Several numerical examples demonstrating the capability and performance of the different finite element formulations are presented. The numerical results are compared with available experimental data for Hostun RF sand and numerical results for Karlsruhe sand on biaxial tests. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A high strain‐rate constitutive model for sand and its application in finite‐element analysis of tunnels subjected to blast     

William Higgins  Tanusree Chakraborty  Dipanjan Basu 《国际地质力学数值与分析法杂志》2013,37(15):2590-2610

The paper presents a constitutive model for simulating the high strain‐rate behavior of sands. Based on the concepts of critical‐state soil mechanics, the bounding surface plasticity theory and the overstress theory of viscoplasticity, the constitutive model simulates the high strain‐rate behavior of sands under uniaxial, triaxial and multi‐axial loading conditions. The model parameters are determined for Ottawa and Fontainebleau sands, and the performance of the model under extreme transient loading conditions is demonstrated through simulations of split Hopkinson pressure bar tests up to a strain rate of 2000/s. The constitutive model is implemented in a finite‐element analysis software Abaqus to analyze underground tunnels in sandy soil subjected to internal blast loads. Parametric studies are conducted to examine the effect of relative density and type of sand and of the depth of tunnel on the variation of stresses and deformations in the soil adjacent to the tunnels. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Study on low‐strain integrity testing of pipe‐pile using the elastodynamic finite integration technique     

Zhi Tang Lu  Zhi Liang Wang  Dong Jia Liu 《国际地质力学数值与分析法杂志》2013,37(5):536-550

This study focuses on the three‐dimensional (3‐D) characteristics of wave propagation in pipe‐pile using elastodynamic finite integration technique. First, a real 3‐D pile‐soil model in cylindrical coordinate system is presented. Then, the governing equations are established. With the boundary and initial conditions, the numerical solution is obtained. The accuracy and feasibility of the self‐written code are further verified via comparing with the measured data. Velocity histories at different angles of pile top and pile tip are illustrated, and the snapshots reflecting the 3‐D characteristics of wave propagation are given. It shows that the interferences of Rayleigh waves can confuse the result interpretation for pile integrity testing. The increase of hammer contact time can effectively mitigate the interferences, and the interferences of Rayleigh waves are weakest at an angle of 90° from where hammer hits. Besides, surrounding soil can partly mitigate the wave interferences. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Variability of volume strain in bounded heterogeneous media     

Ching‐Min Chang  Hund‐Der Yeh 《水文研究》2013,27(3):319-323

The deformation of the solid matrix affects the fluid pore pressure and flow by altering the pore volume. Such interaction in turn affects the storage of groundwater in the void space. Obviously, this subject is of interest in groundwater hydrology. This paper describes an investigation of the effect of aquifer heterogeneity on the variability of the fluid pressure head and solid's volume strain, where the assumption of a constant vertical total stress leads to a relatively simple relationship between changes in solid's volume strain and fluid pressure head. To solve the problem analytically, focus is placed on the one‐dimensional models. It is found from our closed‐form solutions that the variance and correlation length of the log hydraulic conductivity are important in increasing the variability of pressure head and solid's volume strain. It is hoped that our findings will provide a basic framework for understanding and quantifying field‐scale volume strain processes and be useful in stimulating further research in this area. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Dynamics of unsaturated poroelastic solids at finite strain     

Ryosuke Uzuoka  Ronaldo I. Borja 《国际地质力学数值与分析法杂志》2012,36(13):1535-1573

We derive the governing equations for the dynamic response of unsaturated poroelastic solids at finite strain. We obtain simplified governing equations from the complete coupled formulation by neglecting the material time derivative of the relative velocities and the advection terms of the pore fluids relative to the solid skeleton, leading to a so‐called u^s ? p^w ? p^a formulation. We impose the weak forms of the momentum and mass balance equations at the current configuration and implement the framework numerically using a mixed finite element formulation. We verify the proposed method through comparison with analytical solutions and experiments of quasi‐static processes. We use a neo‐Hookean hyperelastic constitutive model for the solid matrix and demonstrate, through numerical examples, the impact of large deformation on the dynamic response of unsaturated poroelastic solids under a variety of loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Strain fields and mechanical response of a highly to medium fissured bentonite clay     

C. Vitone  F. Cotecchia  G. Viggiani  S. A. Hall 《国际地质力学数值与分析法杂志》2013,37(11):1510-1534

This article presents the developments of an ongoing research aimed at modelling the influence of fissuring on the behaviour of clays. In particular, it recalls the main results of an extensive laboratory investigation on a fissured bentonite clay from the south of Italy and presents the data of a new investigation on the evolution with shearing of the strain fields developing within the clay, resulting from Digital Image Correlation (DIC). Element test results are analysed in the framework of continuum mechanics and linked to the clay fissuring features, once characterised using the Fissuring IDentity (F‐ID) chart. This article compares the bentonite behaviour with that of other fissured clays of different F‐IDs, highlighting the common behavioural features. Thereafter, the soil response at the macro level is related to the DIC‐derived strain fields evolving within the clay with loading. For this purpose, DIC was successfully used to investigate the deformation processes active in the fissured clay and the sources of the localisation phenomena. DIC is shown to provide indications of the extent to which highly to medium fissured clays element test results can be of use to model the clay behaviour according to continuum mechanics. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献