Influence of pore water pressure on upper bound analysis of collapse shape for square tunnel in Hoek-Brown media

To investigate the effective shape of collapsing block in square tunnel subjected to pore water pressure, the analytical solution of detaching curve was derived using upper bound theorem of limit analysis with Hoek-Brown failure criterion. The work rate of pore water pressure, which was regarded as an external rate of work, was taken into account in the framework of limit analysis. Taking advantages of variational calculation, the objective function with respect to detaching curve was optimized to obtain the effective shape of collapsing block for square tunnel. According to the numerical results, it is found that the varying pore water pressure coefficient only affects the height and width of the collapsing block, whereas the shape of collapsing block remains unchanged.     

Reliability analysis of retaining walls with multiple failure modes

In order to reduce the errors of the reliability of the retaining wall structure in the establishment of function, in the estimation of parameter and algorithm, firstly, two new reliability and stability models of anti-slipping and anti-overturning based on the upper-bound theory of limit analysis were established, and two kinds of failure modes were regarded as a series of systems with multiple correlated failure modes. Then, statistical characteristics of parameters of the retaining wall structure were inferred by maximal entropy principle. At last, the structural reliabilities of single failure mode and multiple failure modes were calculated by Monte Carlo method in MATLAB and the results were compared and analyzed on the sensitivity. It indicates that this method, with a high precision, is not only easy to program and quick in calculation, but also without the limit of nonlinear functions and non-normal random variables. And the results calculated by this method which applies both the limit analysis theory, maximal entropy principle and Monte Carlo method into analyzing the reliability of the retaining wall structures is more scientific, accurate and reliable, in comparison with those calculated by traditional method.     

Stability analysis for natural slope by kinematical approach

The stability of natural slope was analyzed on the basis of limit analysis. The sliding model of a kind of natural slope was presented. A new kinematically admissible velocity field for the new sliding model was constructed. The stability factor formulation by the upper bound theorem leads to a classical nonlinear programming problem, when the external work rate and internal energy dissipation were solved, and the constraint condition of the programming problem was given. The upper bound optimization problem can be solved efficiently by applying a nonlinear SQP algorithm, and stability factor was obtained, which agrees well with previous achievements.     

考虑温度效应的沥青混合料参数模型

选取修正Burgers模型作为沥青混合料的粘弹性本构模型,基于最小二乘法原理对单轴压缩蠕变试验数据进行拟合,获得本构模型的粘弹性参数。考虑温度变化对沥青混合料粘弹性的影响,建立修正Burgers模型的粘弹性参数模型,运用实验数据拟合粘弹性参数模型的分项系数,理论计算考虑温度效应的蠕变柔量,与实验结果对比分析表明,参数模型有较好的适用性,拟合精度高。粘弹性参数模型能将有限的实验数据推广到其他温度工况,节约大量实验,具有很好适用性。     

Back analysis of general slope under earthquake forces using upper bound theorem

Long time monitoring is acquired to obtain the displacement data for displacement-based geotechnical material back analysis, and these data are hard to be measured under some special condition, such as earthquake. For a simple homogeneous slope, the position of a critical failure surface is determined by value of c/tan ~b. Utilizing upper bound theorem of limit analysis, the external work rate and internal energy for normal slope under earthquake forces are given, and the formula for minimum safety factor is derived. On this basis, the equation of slip surface and the surface depth of a given position are solved. In this way, the strength parameter can be analyzed by known slip surface depth. For practical use, the surface depth for a given slope under varying strength parameter is presented. Finally, two examples are given to show its simplicity and effectiveness.     

近红外光谱分析技术在原油调合中的应用

介绍了当前应用于原油性质快速测定的近红外光谱分析仪和分析技术,以及该技术在原油调合中的应用,分析了该技术在炼厂应用时应注意的问题,为今后技术改进提供参考.该技术的分析系统由分析仪、原油基础数据库、近红外谱图数据库和分析软件组成.     

非均质边坡上限分析的离散机构及应用

 针对非均质边坡,尤其是内摩擦角非均匀边坡的上限分析问题,提出一种新的上限机构。该机构基于滑动面离散的基本思想,采用点到点的方式生成速度间断面,并满足相关联流动法则要求以及几何均匀性条件。推导该机构内外功率的计算方程,并采用序列二次规划(SQP)算法和二分法联合求解边坡的临界高度。利用Matlab编制程序进行求解。将该机构结果与已有文献以及数值模拟结果进行对比,证明该机构在均质、各向异性、非均质等多种工况下均有良好的适用性。最后利用该机构分析内摩擦角随深度线性变化边坡的临界高度变化规律,结果表明内摩擦角非均匀系数对临界高度有显著影响。     

锅炉检修平台倾斜高处坠落事故的案例分析

2014年2月6日10时左右，河南省某化工集团热电公司锅炉炉膛进行升降作业时检修平台，西南角发生倾斜，河南某检修有限公司2名作业人员从检修平台坠落，造成轻微伤害。     

关于对D-D503罐内甲苯含量超标事故的案例分析

2014年1月15日10时40分，某股份公司技术中心实验室报精苯装置纯苯样分析结果，其中苯含量97．57％，甲苯含量2．4％，纯苯分析不合格。精苯主控立即上报并通知现场人员，11时将纯苯切出至不合格苯管线。随后主控人员调整系统负荷、工艺指标，13时50分取样分析合格，14时19分纯苯切回产品罐。