单重保温海底管线层间抗剪能力的室内全比尺试验研究

单重保温管较传统的双重管中管结构具有很多优势。铺设单重管最容易出现的问题是由于张紧器张力作用而导致单重管各层之间产生剪切力,如果抗剪能力不足产生相对滑移,就会出现拉脱现象,造成工程事故。以某依托工程采用的单重保温管为例,介绍了各层之间抗剪能力的室内全比尺试验方法,给出的试验结果可供设计参考。     

结构性海洋黏土损伤模型的二次开发及应用

原状土的结构性作为21世纪土力学的核心问题,一直以来受到学者们的广泛关注。软黏土的结构性损伤这一力学行为会对海洋结构物基础造成不可忽略的影响。以海底原状土的结构性特征为研究对象,推导了考虑黏土结构性的SANICLAY模型的数值实现格式。通过子增量步显式算法和有限元的二次开发,实现了结构性多屈服面本构模型在有限元方法中的应用。通过与不同应力路径下的三轴试验结果对比,验证了开发的子程序可准确模拟海洋黏土所具有的结构性。基于不同应力路径试验的数值模拟结果,研究了不同固结和剪切条件下土体塑性势面和屈服面的演化规律,揭示了土体固结可降低结构性损伤程度以及剪切过程中土体产生结构性损伤的机制。将二次开发的子程序应用到具体的边值问题中,开展了可考虑土体结构性影响的海上风电筒型基础静承载力研究,揭示了土体结构性对筒型基础的地基破坏模式、峰值承载力和残余承载力的影响;引入残余衰减比来表征土体结构性破坏后筒型基础的残余承载力,并建立了残余衰减比与结构损伤因子之间的关系。     

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.     

制度转型背景下的成都市博物馆空间生产过程与机制

博物馆空间生产是文化空间生产的重要构成,现已成为城市发展的重要实践。在制度转型的背景下,国内学者对此研究尚少。以成都市为案例地,采用深度访谈、参与式观察、文本梳理等质性研究方法,深入分析制度转型背景下博物馆空间生产过程与机制,揭示博物馆空间生产的总体状况以及博物馆空间生产所经历的探索、规范和集约3个阶段。从空间属性(根本动力)、主体结构改变(主体动力)、城乡统筹与旧城改造(基础动力)3个方面归纳了博物馆空间生产机制。讨论了制度转型期我国博物馆空间生产独特性的原因及存在的问题。     

饱和软黏土中不同形状深水防沉板基础承载特性研究

防沉板基础是水下井口、管汇节点与管汇终端等的永久支撑结构,其承受的荷载具有明显的复杂性、非线性和不确定性,给防沉板基础的稳定性研究带来了巨大挑战。本文研究了在剪切强度随深度线性增长的不排水饱和软黏土中,相同用钢量条件下矩形、方形、六边形和圆形防沉板基础的承载特性。采用数值模拟方法确定了竖向荷载V、水平向荷载H(H_x、H_y)、弯矩荷载M(M_x、M_y)和扭矩荷载T联合作用下,防沉板基础在V-H、V-M、V-T、H_x-H_y、M_x-M_y、T-H和T-M荷载空间的地基承载力包络线,并建立了相应的拟合公式。研究表明,不同的基础形状对其承载力影响显著,当V较大时,适宜选用圆形基础;当H较为显著时,应选用矩形或方形基础;圆形、方形和矩形基础的抗弯特性分别适用于不同条件下M为主控荷载的情况;当T的影响不可忽视时,矩形或方形基础为首选形式,六边形和圆形基础次之。     

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…     

点支撑缺陷下海底埋管热屈曲分析

由于生产工艺的要求,开采的原油经常需要在一定的温度和压力下才能顺利输送,而输油过程中的高温和高压会导致海底管线中产生较大的附加应力。管线受到地基土的约束作用后无法自由变形,附加应力的不断累积,造成管线发生整体屈曲变形,埋地的海底管线通常会产生竖直向的整体屈曲变形而影响使用甚至破坏。基于点支撑初始缺陷形式的海底管线,给出了管线竖直向整体屈曲分析的解析解,结合实际工程中铺设的高温高压输油管线进行了整体屈曲分析,揭示了不同温度条件下埋地管线发生竖直向整体屈曲的规律性,提出挖沟掩埋可以有效地防止管线发生温度应力下的整体屈曲     

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。     

海上风电机组筒型基础工作及承载特性研究

筒型基础是一种新型的海上风电基础,由于其具有减少工程量、节省投资、缩短施工时间、可重复使用等优点,在某些领域正在逐步替代桩基和重力式基础。目前工程上对筒型基础的设计还没有现成的规范可供使用,一般是将筒内部土体与筒壁视为一体,然后采用简化的极限平衡方法进行设计计算,不能反映筒内土体的工作特性。以福建近海某风电基础工程为依托,采用大型有限元软件ABAQUS对海上风机单筒基础的承载特性进行了三维有限元数值分析。根据海上风机的受力特点,考虑基础隔舱的作用效果,建立了筒型基础的简化模型与有无隔舱的计算模型。计算结果表明：筒型基础在受荷过程中,基础内部土体产生屈服变形,使得筒型基础的承载特性不同于简化极限平衡方法。两者之间的差异使得实际的地基承载能力比极限平衡方法计算所得的要小。此外,对现行简化计算方法的误差进行了估计,并对筒型基础承载力计算提出建议,可供筒型基础设计者参考。