A rate‐dependent cohesive crack model based on anisotropic damage coupled to plasticity     

Per‐Ola Svahn  Kenneth Runesson 《国际地质力学数值与分析法杂志》2006,30(9):887-916

In quasi‐brittle material the complex process of decohesion between particles in microcracks and localization of the displacement field into macrocracks is limited to a narrow fracture zone, and it is often modelled with cohesive crack models. Since the anisotropic nature of the decohesion process in separation and sliding is essential, it is particularly focused in this paper. Moreover, for cyclic and dynamic loading the unloading, load reversal (including crack closure) and rate dependency are essential features that are included in a new model. The modelling of degradation is based on a ‘localized’ version of anisotropic continuum damage coupled to inelasticity. The concept of strain energy equivalence between the states in the effective and nominal settings is adopted in order to define the free energy of the interface. The proposed fracture criterion is of the Mohr type, with a smooth transition of the failure and kinematics (slip and dilatation) characteristics between tension and shear. The chosen potential, of the Lemaitre‐type, for evolution of the dissipative processes is additively decomposed into plastic and damage parts, and non‐associative constitutive equations are obtained. The constitutive equations are integrated by applying the backward Euler rule and by using Newton iteration. The proposed model is assessed analytically and numerically and a typical calibration procedure for concrete is proposed. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Surface and subsurface water balance estimation by the groundwater recharge model and a 3-D two-phase flow model/Estimation de bilan hydrologique de surface et de subsurface à l’aide de modèles de recharge de nappe et d’écoulement diphasique 3-D     

《水文科学杂志》2013,58(2)

Abstract

Abstract Land development often results in adverse environmental impact for surface and subsurface water systems. For areas close to the coast, land changes may also result in seawater intrusion into coastal aquifers. Due to this, it is important to evaluate potential adverse effects in advance of any land development. For evaluation purposes a combined groundwater recharge model is proposed with a quasi three-dimensional unconfined groundwater flow equation. The catchment water balance for a planned new campus area of Kyushu University in southern Japan, was selected as a case study to test the model approach. Since most of the study area is covered with forest, the proposed groundwater recharge model considers rainfall interception by forest canopy. The results show that simulated groundwater and surface runoff agree well with observations. It is also shown that actual evapotranspiration, including rainfall interception by forest canopy, is well represented in the proposed simulation model. Several hydrological components such as direct surface runoff rate, groundwater spring flow rate to a ground depression, trans-basin groundwater flow etc., were also investigated.  相似文献   

BP神经网络在区域似大地水准面精化中的应用     

雷伟伟  陈虎  郑红晓 《地理空间信息》2009,7(5):81-83

研究BP神经网络算法在区域似大地水准面精化中的应用，阐述了神经网络的结构及其算法，根据焦作市D级GPS网控制点的数据，利用MATLAB进行编程计算，拟舍得到厘米级的似大地水准面模型，并得到了有益的结论。  相似文献   

姑咱地震台张应变异常信号与修路施工间关系探讨     

张凌空  牛安福 《地震地磁观测与研究》2021,42(1):98-104

与2008年5月12日汶川M_S8.0地震时记录到的大量压应变异常信号不同,2013年4月芦山M_S7.0地震前后姑咱地震台钻孔应变仪记录到的却是显著张应变异常,特别是临震前几日信号大幅度突升,而该时段恰巧台站大门前进行修路施工,这究竟是地球物理异常还是干扰,一直有很大争议。研究发现,这些异常信号在时间上具有高度的准同步性,即都发生在白天8:00—10:00或7:30—17:00之间,这正是工人的上班时间,而自然力产生的异常应具有随机性特征,不应有较强规律性;其次,临震前的异常振幅比芦山地震本身产生的振幅还大2倍,将其视为地球物理异常也有违常理。又结合腾冲地震台钻孔应变观测干扰实例进行分析,认为尚不能排除该张应变异常为施工干扰的可能性。  相似文献   

非均匀P\|偏振电磁波在导电界面的反射系数曲线   总被引：1，自引：1，他引：1       下载免费PDF全文

李瑞忠  刘福平  杨长春  张红梅  陈辉国 《地球物理学进展》2005,20(2):342-347

基于非均匀电磁波在导电媒质中传播时其相移常数和振幅衰减常数方向的不一致性，利用电磁波在导电媒质界面的边界条件，导出了非均匀P\|偏振电磁波的反射系数. 反射系数随入射角的变化曲线显示：当电磁波由电导率大的介质射向电导率小的介质时，在相移常数临界角和衰减常数临界角附近存在峰值，且反射系数的数值小于1，这一结果与全反射光的结果有明显的差异.  相似文献   

斜压大气亚临界不稳定的数值试验     

陆维松  江敦双  张惠莲 《南京气象学院学报》2001,24(3):299-307

利用一个由表面摩擦和辐射线弛强迫驱动的斜压准地转两层模式作数值试验，来研究斜压大气中的亚临界不稳定现象。试验结果表明，当无量纲量β≥0.25时，斜压两层大气中能够发生亚临界不稳定现象。亚临界不稳定现象的发生与初始扰动的选择有关。科氏参数的经向梯度的大小又是影响斜压稳定性强度的一个重要因素，其值越大，斜压稳定性强度越小。  相似文献   

Trajectory Control： Directional MWD Inversely New Wellbore Positioning Accuracy Prediction Method     

AhmedAbdAlazizIbrahim TagwaAhmedMusa 《中国地质大学学报(英文版)》2004,15(4):425-433

The deviation control of directional drilling is essentially the controlling of two angles of the wellbore actually drilled, namely, the inclination and azimuth. In directional drilling the bit trajectory never coincides exactly with the planned path, which is usually a plane curve with straight, building, holding, and dropping sections in succession. The drilling direction is of course dependant on the direction of the resultant forces acting on the bit and it is quite a tough job to hit the optimum target at the hole bottom as required. The traditional passive methods for correcting the drilling path have not met the demand to improve the techniques of deviation control. A method for combining wellbore surveys to obtain a composite, more accurate well position relies on accepting the position of the well from the most accurate survey instrument used in a given section of the wellbore. The error in each position measurement is the sum of many independent root sources of error effects. The relationship between surveys and other influential factors is considered, along with an analysis of different points of view. The collaborative work describes, establishes a common starting point of wellbore position uncertainty model, definition of what constitutes an error model, mathematics of position uncertainty calculation and an error model for basic directional service.  相似文献   

The　quasi－static　solutions　of　two　kinds　of　the　thermo－elastic　problem　and　the　time　spacedistributionfeatureoftheseismicprecursorfields     

赵永安 《地震学报(英文版)》1996,9(3):471-484

Ｔｈｅｑｕａｓｉ┐ｓｔａｔｉｃｓｏｌｕｔｉｏｎｓｏｆｔｗｏｋｉｎｄｓｏｆｔｈｅｔｈｅｒｍｏ┐ｅｌａｓｔｉｃｐｒｏｂｌｅｍａｎｄｔｈｅｔｉｍｅｓｐａｃｅｄｉｓｔｒｉｂｕｔｉｏｎｆｅａｔｕｒｅｏｆｔｈｅｓｅｉｓｍｉｃｐｒｅｃｕｒｓｏｒｆｉｅｌｄｓＹＯＮ...  相似文献   

非均匀介质中微侧向测井仪器的三维有限元数值分析     

陈晓光  聂在平 《物探化探计算技术》1997,19(3):202-209

在这篇文章中，分析了一个具有井眼的非均匀介质中似稳电流场的边值问题。采用了三维有限元的直接解法求解三维似稳电流场；给出了微侧向测井仪器的电极表面电流分布、假几何因子以及８英寸井眼的泥饼校正曲线；求出了在具有倾斜地层条件下，微侧向测井仪器对界面的响应。数值结果与发表的文献非常吻合，从而证明了这种方法的正确性。因此，它为新的仪器研制和微侧向测井解释提供了可靠的数据和理论依据。  相似文献   

基于神经网络的似大地水准面模型精化方法研究     

杨小青  胡伍生 《测绘工程》2008,17(4):8-11

似大地水准面的精化与高程异常的求解是同一个概念,为提高似大地水准面精化的精度,采用格网＋神经网络方法,借助神经网络BP方法,建立高程异常与坐标之间的函数关系;用训练好的神经网络模型和固定间隔的格网,建立格网模型;在已建好的格网模型中,内插出给定点的高程异常值。结合江苏省C级GPS水准网进行试验,拟合效果有明显的改进,克服了目前研究中存在的问题。  相似文献