模拟基坑开挖过程的试验研究

采用三轴剪切试验对基坑开挖过程中土体卸荷的应力路径进行模拟，研究了由于侧向卸荷对土体抗剪强度指标产生的影响，并从土的微观结构角度分析了产生这一现象的原因。试验结果表明，经过侧向卸荷过程土样的抗剪强度指标与常规三轴试验明显不同。     

复杂条件下双层立管的有限元分析

应用有限元方法,对双层立管进行了应力的计算分析。通过一个工程实例,阐述了模型建立．重要参数计算及结果分析的全过程,并着重分析了法兰位置,海底平管段的膨胀量及土壤的约束作用这三者对立管内部应力的显著影响,可为立管设计者借鉴。     

Pit bearing capacity effect on status of soil plug during pile driving in ocean engineering

Foundation piles of the offshore oil platforms in the Bohai Bay are usually longer than 100 m with a diameter larger than 2 m.Driving such long and large-sized piles into the ground is a difficult task.It needs a comprehensive consider ation of the pile dimensions,soil properties and the hammer energy.Thoughtful drivability analysis has to be performed in the design stage.It has been shown that judging whether the soil column inside the pile is fully plugged,which makes the pile behave as close-ended,strongly influences the accuracy of drivability analysis.Engineering practice repeatedly indicates that the current methods widely used for soil plug judgment often give incorrect results,leading the designers to make a wrong decision.It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile.Based on the Terzaghi’s bearing capacity calculation method for deep foundation,a new approach for judging soil plug status is put forward,in which the surcharge effect has been considered and the dynamic effect coefficient is included.This approach has been applied to some practical engineering projects successfully,which may give more reasonable results than the currently used method does.     

Model test based soil spring model and application in pipeline thermal buckling analysis

The buckling of submarine pipelines may occur due to the action of axial soil frictional force caused by relative movement of soil and pipeline, which is induced by the thermal and internal pressure. The likelihood of occurrence of this buckling phenomenon is largely determined by soil resistance. A series of large-scale model tests were carried out to facilitate the establishment of substantial data base for a variety of burial pipeline relationships. Based on the test data, nonlinear soil spring can be adopted to simulate the soil behavior during the pipeline movement. For uplift resistance, an ideal elasticity plasticity model is recommended in the case of H/D (depth-to-diameter ratio)>5 and an elasticity softened model is recommended in the case of H/D≤5. The soil resistance along the pipeline axial direction can be simulated by an ideal elasticity plasticity model. The numerical analyzing results show that the capacity of pipeline against thermal buckling decreases with its initial imperfection enlargement and increases with the burial depth enhancement.     

Analysis on Interface Shear Stress of Thermally Insulated Ocean Pipelines Under Installation

1.IntroductionMost of the crude oil producedfromoffshore China has a highcontent of wax,which makesthe oilagglomerate at hightemperature.Heat preservation measures,therefore,must be adopted to maintainthe temperature higher thanthe oil’s pour point,sotha…     

海底管线整体屈曲过程中塑性变形研究

海底管线是海洋油气工程中主要的输送手段。在工作状态下,受高温高压的影响,深海管线可能会发生水平向整体屈曲。随海洋油气作业水深的增大,施加于管线的温度和压强也逐渐增加,导致管线产生较大的屈曲位移和截面应力,使得截面产生塑性应变。本文采用数值模拟方法,对海底管线整体屈曲过程中塑性区的分布及其与整体屈曲影响因素的关联性、塑性变形对水平向变形的影响和塑性变形造成的截面椭圆度的变化规律进行分析,研究塑性变形对整体屈曲过程影响的规律。     

关于土层相关距离计算方法的研究

根据随机场理论,对求解土层相关距离的递推空间法和相关函数法进行比较和探讨,指出两种方法所求得的相关距离值存在偏差的原因,并从理论上证明当样本容量足够大时两种方法的计算结果可以得到统一。对相关函数法作出改进,使其更易于曲线的拟合和参数的确定,最后采用实际工程的勘察测试资料进行了分析计算,验证了由计算公式推导所得的结论在实际工程中也是成立的。     

严寒地区路堑边坡破坏机理及稳定计算分析

内蒙古省际通道新林北至扎兰屯段一级公路修建过程中,一些局部路堑边坡出现了较严重的边坡滑塌现象。目前公路行业的路基设计施工规范中尚没有涉及高寒地区路堑边坡的设计施工方法,也缺乏此类地区路堑边坡的稳定性设计评价标准。为此在进行了大量调研工作的基础上,对路堑边坡的破坏机理进行了分析,提出了确保公路路堑边坡稳定的有效措施及相应的计算方法,成果可为其他类似工程借鉴参考。     

固化污泥的工程性质及微观结构特征

通过室内试验,向污泥中添加不同比例的石灰、土和粉煤灰,研究了不同配合比下固化污泥的工程性质。研究发现,采用适当的配合比情况下,固化污泥的强度可以满足填埋的要求,渗透性也有很大提高;采用冷冻干燥技术和扫描电镜研究了固化污泥的微观结构,发现固化后污泥的密实性有较大的提高,这是其强度提高的一个重要原因;应用分形几何的理论,对由扫描电镜获取的固化污泥微观结构图像进行了定量分析,结果表明,分形维数和强度之间有较强的正相关性。