Spatial and Temporal Stress Variations before and after the 2008 Wenchuan Mw 7.9 Earthquake and its Implications: A Study based on Borehole Stress Data

In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF), prior to and following the 2008 Wenchuan earthquake(WCEQ). Analysis of the stress field related to fault strength and behavior is useful for understanding geodynamic processes and conducting hazard assessments. The shallow stress changes after the WCEQ show clear along-strike variations. Degrees of stress orientation rotations have a negative ...     

适用于堆石料的分数阶下加载面模型

堆石料的应力-应变曲线具有应变硬化和软化的特性,并且体积变形会伴随着剪缩和剪胀现象的发生;此外,应力水平、应力路径和密度等因素均会对堆石料的力学特性产生显著的影响。基于临界状态土力学的理论框架,建立了适用于堆石料的分数阶下加载面模型,该模型为典型的双屈服模型。在平均主应力p-剪应力q平面,剪切过程中堆石料当前应力状态点和参考应力点分别位于下加载面和参考屈服面上,两者之间的相对位置与孔隙比之差ρ相关。相比于状态参量Ψ,ρ能够额外考虑应力路径对堆石料剪胀特性的影响。新模型的另一个显著特点在于能够考虑堆石料塑性流动方向与加载方向之间的差异性。在不引入塑性势函数的情况下,新模型对屈服函数进行Caputo微分并得到分数阶塑性流动法则,进而统一描述相关联和非相关联的塑性流动法则。新模型具有形式简单且参数较少等优点,所包含的7个材料参数均具有明确的物理意义,并且可以采用常规的室内试验结果进行标定。通过将模型计算结果与Tacheng堆石料在不同初始孔隙比和围压条件下的三轴压缩排水试验结果进行对比分析,结果表明新模型能够准确地描述堆石料的应力-应变曲线和体积变形特点;同时,新模型也能够合理地描述初始孔隙比对堆石料在e-lnp平面(e为孔隙比)临界状态线的影响。     

液舱晃荡载荷计算与强度校核系统研究

随着薄膜型LNG运输船的需求量不断增加,晃荡载荷已成为船舶安全性研究的重要内容之一。本文结合中国船级社规范所推荐的公式,对薄膜型LNG船晃荡水平的载荷进行研究,提出载荷计算方法和流程,在MSC.patran的基础上结合二次开发语言PCL,设计了一套晃荡载荷计算与校核系统。该系统对有限元模型进行前后处理,设计了舱室识别算法来搜索晃荡载荷的作用域,实现薄膜型LNG船晃荡载荷的自动计算与施加,完成屈服强度评估。通过算例测试证明本系统自动计算结果的有效性和准确性,可以为工程设计人员大大节约工作量,大幅度提高工作效率。     

非线性模型实用处理方法探讨

本文结合非线性模型通常采用迭代计算方法处理的实际,指出在给定初值的情况下,直接依据迭代计算结果的收敛情况来判别非线性模型能否进行线性化,可以避免对非线性强度指标的复杂计算,从而简化判别过程中的数据处理方法;实例表明,相对已有非线性强度指标的计算,依据迭代计算结果判断非线性化模型的线性化度量,计算简洁,可靠性更高。     

基于因子分析的九江市综合经济实力研究

从经济发展规模、经济发展结构和经济发展效益3个方面选取了9个能够反映综合经济实力的指标,运用因子分析法,借助SPSS16．0软件对数据进行分析。并根据因子分析得到的因子得分对九江市的综合经济实力做出综合评价。研究结果证踢九江市的综合经济实力在江西省排名第三,属于中上等水平。对此提出了推动工业企业低碳化;加强对外开放水平;继续发挥旅游优势的建议,是进一步提升九江市综合经济实力的有效途径。     

FY-2C卫星资料在热带风暴“范斯高”预报分析中的应用

运用FY-2C卫星云图及其相关定量资料TBB,对热带风暴"范斯高"的强度、路径及降水进行了综合分析,归纳出"范斯高"发生发展中云系的一些特征,从而判断其强度变化和移动方向;在降水方面,黑体亮温(TBB)场和降水量有很好的对应关系,TBB场清晰地揭示了"范斯高"的降水分布特征,即五指山以北出现强降水,其中西部最强,而南部降水较弱。     

一大型倾倒体边坡非线性强度折减稳定性分析

分析的大型倾倒体边坡位于西藏林芝地区巴河上老虎嘴水电站右岸交通洞出口附近。该倾倒体坡体结构破碎,节理发育,边坡开挖后多次发生滑塌。在分析该倾倒体成因基础上,其强度特性用适于节理岩体的Hoek-Brown准则描述;计算采用非线性强度折减弹塑性数值方法;并对比了刚体极限平衡法计算结果。结果表明,两种方法获得的整体安全系数基本一致;加固前边坡基本处于极限平衡状态;数值分析较好地揭示了边坡失稳滑动特征;经工程措施处理后稳定性总体满足设计要求。     

模糊数学在数字测井解释岩石强度中的应用

目前岩石相对硬度分六个等级,在实际工作中,可不考虑某一岩石的抗压强度的准确性,只需求出它隶属于某一级硬度的可靠程度即可,为此提出模糊模式识别方法解决这类问题:首先确定与岩石抗压强度相关的3个数字测井参数——强度指数、杨氏模量、密度参与计算,然后分配相应权重,构建与硬度级别相对应的6个模糊子集,最后建立判别岩石硬度分级的6个隶属函数作为模糊模式识别岩石硬度等级。判别原则:将任一深度的强度指数、杨氏模量、密度3个数据加权求和,将其值作为判别对象依次代入6个模糊模式得到6个计算值,按照最大隶属原则,确定其相对的硬度级别,该值越接近1,则其隶属于那个硬度级别的程度就越大。     

An anisotropic strength criterion for jointed rock masses and its application in wellbore stability analyses

In this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd.     

Population balance in confined comminution using a physically based probabilistic approach for polydisperse granular materials

A novel, simplified approach is presented in order to compute variations of grading in granular assemblies during confined comminution under quasi‐static compression. The method is based on a population balance equation and requires a breakage probability, considered here as a probabilistic phenomenon that takes into account the particle strength and the loading condition of individual grains. Under basic assumptions, a simple breakage probability can be defined in order to get a valuable result for engineering applications and powder technology. The size effect in the strength of individual particles is introduced according to Weibull's theory. The particle loading and the cushioning effect in the granular packing are accounted for by considering the orientations of the contact forces obtained from 3D discrete element method simulations of highly polydisperse materials. The method proposed could have a value for engineering purposes in powder technology and geomechanics and gives a general framework for further research developments based on population balance. Copyright © 2016 John Wiley & Sons, Ltd.