随机有限元法在基坑变形可靠度分析中的应用

排桩内支撑支护结构作为一种常见的基坑支护形式,在设计时对其变形的控制要求较高,传统设计方法没有充分考虑材料参数的变异性,因此可以采用可靠度计算来评估围护桩的横向位移是否满足设计要求。由于围护桩的变形可靠度功能函数很难用显式方程来表达,本文选择了Monte Carlo随机有限元法来计算围护桩的位移可靠度,在Monte Carlo随机有限元法的基础上,通过对ABAQUS/CAE有限元模拟软件进行二次开发以实现随机有限元计算和后处理提取桩体横向位移最大值的功能。建立功能函数g=u_(警戒值)-u_(实际值),g大于零的概率即为围护桩的位移可靠度。为了验证该方法的有效性结合某工程案例,将土体的重度、内摩擦角和粘聚力3个变量作为随机变量计算了围护桩的位移可靠度。同时利用该方法研究分析了开挖区内降水深度对桩体位移可靠度的影响,结果表明随着降水深度的增加可靠度不断提升但提升幅度不断减小。

Factors influencing pore-pressure prediction in complex carbonates based on effective medium theory

A calculation model based on effective medium theory has been developed for predicting elastic properties of dry carbonates with complex pore structures by integrating the Kuster-Toksǒz model with a differential method.All types of pores are simultaneously introduced to the composite during the differential iteration process according to the ratio of their volume fractions.Based on this model,the effects of pore structures on predicted pore-pressure in carbonates were analyzed.Calculation results indicate that cracks with low pore aspect ratios lead to pore-pressure overestimation which results in lost circulation and reservoir damage.However,moldic pores and vugs with high pore aspect ratios lead to pore-pressure underestimation which results in well kick and even blowout.The pore-pressure deviation due to cracks and moldic pores increases with an increase in porosity.For carbonates with complex pore structures,adopting conventional pore-pressure prediction methods and casing program designs will expose the well drilling engineering to high uncertainties.Velocity prediction models considering the influence of pore structure need to be built to improve the reliability and accuracy of pore-pressure prediction in carbonates.

对农村农民收入与环境保护关系的思考——基于安徽省蒙城县楚村镇沟北村的实地调查报告

通过对安徽省亳州市蒙城县楚村镇沟北村实地调查发现,该村农民收入偏低,环境状况良好。收入偏低是因为没有工业生产,环境良好也得益于没有工业生产带来的污染,农民希望既能增加收入,又不破坏现有环境,现针对这种状况提出了加快土地流转并释放闲置土地资源;发展绿色农业和绿色林业;应加强技能培训;发挥名人效应以打造农副业土特产品牌;鼓励资产收益项目;增加商业活动;开辟金融扶贫渠道等对策建议。