通过计算比较分析,讨论了梁板式高桩码头结构计算的各种计算模型的适用性.分别以某15万t级集装箱高桩码头的结构段和单个排架段结构为研究对象,建立了梁板单元、实体单元和等效桩基实体单元的有限元分析模型,通过对控制工况进行计算比较,讨论了各种计算模型的计算效率、特点和适用性.计算码头桩基内力、横纵梁内力、沉降变形量时,可采用梁板单元结构段模型,作为近似,也可采用现设计规范推荐的投影梁板单元排架结构模型.

为设计和优化深水气力提升装置并估算其输送效率,基于连续性方程及冲量方程,耦合能量方程,并考虑气体体积膨胀和截面含气率变化,建立了一种通用的气力提升三相流装置的理论分析模型.该分析模型的计算结果与文献试验数据的吻合性较好.利用本文模型针对工程实例的计算分析表明,增大输送管径可有效提高提升系统的输送功效.

本文提出了一种针对海上风电单桩基础结构计算的改进竖向地基梁法,并对单桩基础结构进行了优化计算.对单桩基础结构采用竖向地基梁法计算,基于m法计算土抗力,限制浅层土抗力的极限值不能超过极限土压力.结合工程情况,利用传统竖向地基梁法与改进方法,对单桩基础结构进行了优化计算,两种方法的计算结果存在一定差异,改进计算方法所得最大泥面水平位移增大34.6％.对于变形控制较为严格的海上风电桩基础结构,限制浅层土抗力的极限值不能超过极限土压力并使用改进方法对单桩结构进行计算是必要的.

In order to improve the evaluation ability of bearing capacity of offshore large-diameter monopile, the initial high strain detection and repeated high strain detection with an interval of 10-84 days were carried out on 6 large-diameter monopiles with a diameter of 7.2m-7.4m in the offshore wind field dominated by cohesive soil layer. The results show that the time-dependent increase of tip resistance, pile side resistance and total resistance of large-diameter monopiles in the same offshore wind farm has great discreteness, and the axial force increment of pile has a consistent change trend. This paper puts forward the prediction interval of 95% guarantee rate of bearing capacity increment of offshore large-diameter single pile based on depth, which provides a basis for the design of large-diameter monopile.

针对硬质海床上的电缆采用混凝土联锁块软体排进行覆盖保护的技术方案,对软体排的抗拖锚稳定性进行了分析.首先对拖锚过程中位于软体排上的锚体及锚爪进行受力分析,建立锚爪在软体排上的运动控制方程,据此求得锚爪在软体排上的运动条件及施加给软体排的作用力;之后对软体排及电缆进行受力分析,建立软体排及电缆的抗滑稳定性分析方程.利用所建立的软体排抗拖锚稳定性分析方法,对试验模型进行了计算分析,结果与试验吻合.结合工程中的软体排参数,讨论分析了对软体排的抗拖锚性能有影响的因素和影响规律,并提出了提高软体排抗拖锚稳定性的措施.

In the simulation of discontinuous block systems, the discrete element method (DEM) has better computational efficiency and convergence than the finite element method (FEM). When several DEM particles are bonded together with parallel bonds (the bonded particle model, BPM), various shapes and block fractures can be simulated. The main aim of the BPM is to simulate a continuous material in which the stress distribution is continuous. Since the existing stress result for a single particle is an average value over the particle's area, stress results do not exist in the area between particles. In this paper, the stress value for a single two-dimensional DEM particle is deduced. A stress recovery procedure with a linear stress function for a triangular element generated by the centroids of three bonded particles is proposed. In this way, the recovered stress field for the whole mesh composed of all triangular elements is continuous. A stress gradient exists in the whole mesh. This can also provide more accurate stress values for judging a fracture inside a block. Symmetrical and asymmetrical models are simulated by the BPM and FEM. Similar to the FEM results, the recovered stress results for the BPM can describe the stress distribution in the simulated continuous blocks. For the model with the theoretical stress solution, the recovered result and the theoretical solution coincide well.

Discontinuous deformation analysis (DDA) has been widely applied for the simulation of block systems that have many discontinuous surfaces. The penalty method is utilized to ensure that there are no penetrations between blocks. A linear polynomial function for displacement leads to a constant stress for a block, which cannot precisely describe the stress field within the block. Therefore, a high-order polynomial displacement function and a fine mesh are always used to improve the precision of the stress field. However, these means are not practical for simulating block systems that have many contacts. In this paper, the contact-stress-based stress recovery methods are proposed for DDA. High-precision solutions for the contact stresses on the boundaries of the blocks are utilized. The first-order Gaussian point of a block is the block's centroid, where the constant stress obtained via DDA is of higher precision. The high-precision solutions for the stresses are utilized in the least squares method to recover a single block's inner stress field. The proposed methods enhance the resolution of the stress field inside a single block without increasing the computational effort in the main iterative process for displacement in DDA. Numerical examples are simulated using both the finite element method (FEM) with a fine mesh and the proposed DDA program. The recovered DDA results can accurately describe the distribution of the stresses in a single block and, in some areas, have the same precision as the FEM results. Moreover, the precision of the proposed methods improves as the gradient of the contact stress on the boundary decreases.

为研究以流体粒子描述波浪运动,以固体单元描述砾石运动的两相介质大变形运动,在港口、海岸工程科学研究中具有重要意义.本文提出砾石单元法(GEM),介绍了光滑粒子动力学方法(SPH)和GEM的基本原理,阐述了GEM与离散单元法(DEM)的异同之处,说明了采用SPH方法与GEM构建波浪砾石耦合运动数学模型的方法和过程.应用SPH方法建立数值波浪水槽,用GEM模拟波浪作用下堆积砾石的滚落、坍塌变形,构建了SPH方法与GEM耦合数学模型.模拟了水槽造波和波浪生成过程和波浪作用下砾石的滚落、坍塌变形,并与物理模型试验成果进行了比较,结果基本吻合.本文提出的GEM法具有模拟单相堆积砾石运动和堆积砾石与流体粒子耦合多相介质运动的功能,是对DEM法的补充和改善.本文提出的堆积力学球概念和拟序排列求解方法是砾石单元法的重要组成部分.

落锚作业是船舶抛锚定位过程的第1个环节,在落锚过程中,船锚不仅可能直接撞击海底管线造成危害,而且船锚的贯入深度会影响拖锚的运动轨迹,从而间接影响海底结构物的运行安全,可见确定船舶落锚阶段船锚的最终贯入深度十分重要.为此,首先开展一系列小比尺落锚模型试验,分别研究在黏性土和无黏性土中船锚质量和落锚高度对霍尔锚和大抓力锚最终贯入深度的影响,发现贯入深度随船锚质量和落锚高度的增加而呈非线性增加,但增幅不断减缓.然后,结合小比尺模型试验,采用能量法和太沙基极限承载力公式拟合船锚贯入深度的计算公式,并确定式中的经验系数.另外,在小比尺模型试验的基础上,验证船舶落锚的数值模拟方法,并对原型船锚的贯入过程进行分析,讨论贯入过程中船锚姿态变化的过程和规律,以进一步揭示落锚贯入深度与船锚触底动能之间的关系.最后,开展现场船舶落锚试验,对比分析本文公式、Young公式、DNV坠物公式、DNV落管公式与现场实测数据之间的差异,发现试验结果和本文公式吻合良好,在验证本文公式正确性的同时阐明了其他理论算法的适用条件与局限性.

宽肩台堆石堤是海岸工程中的一种海堤形式,其以结构简单、施工快捷、布局灵活和造价经济的特点在工程中得到了广泛应用.宽肩台防波堤以堆积块石为主体,在海区波浪作用下达到稳定的堆积结构.进行宽肩台式防波堤稳定性的研究是设计宽肩台防波堤的重要基础.介绍了波浪水槽的光滑粒子动力学(SPH)理论和建立方法,验证了造波结果.提出了一种块石单元法(GEM)模式,以块石单元为独立刚体来模拟宽肩台防波堤上的块石在波浪作用下的受力状态和运动过程.建立了一种垂向二维光滑粒子动力学方法SPH与GEM耦合的波浪和块石模型,采用SPH与GEM相结合,对防波堤堆石孔隙外部的波浪运动和内部的孔隙环流进行模拟计算,并根据Forchheimer公式确定孔隙内部的压力.用SPH方法模拟堆石堤外部流场的波浪破碎压力,用孔隙环流模拟堆石堤内部的孔隙压力.使用耦合模式模拟了宽肩台防波堤孔隙流场,验证了孔隙压力分布.模拟了波浪作用于块石和块石对波浪动力响应过程,给出了静态平衡到动态平衡的流固场变化,模拟结果与物理模型试验结果基本一致.耦合模型的建立为宽肩台堆石堤的稳定性研究提供了理论依据,同时也为同类型工程研究提供了新思路.

Newly proposed pile wall frame structures (PWFSs), notably with small-spaced row piles, have great potential for cofferdams of artificial islands applied for oil recovery in shallow seas. Studies have been called to analyze the bearing performance of small-spaced row piles subjected to lateral loads. A numerical investigation of laterally loaded row piles with small pile spacing was conducted to achieve a fitted algebraic expression of the P-Y curve. Significantly different from the hyperbolic P-Y curves of a single pile reported in other studies, the P-Y curve of small-spaced row piles is similar to an elastic–perfectly plastic curve, which simply depends on the ultimate lateral bearing capacity of piles (Pu) and initial slope of curves (Ki). Parametric studies have revealed that Pu and Ki values are affected by pile spacing, depth, untrained shear strength of soil, and relative soil–pile rigidity. Algebraic expression of the P-Y curve could be employed for the subgrade reaction method and be effectively used in predicting the behavior of small-spaced row piles, such as PWFSs.

劲性搅拌桩是一种将PHC管桩插入水泥土中形成协同受力的桩型.在天津市汉沽区某工业园区场地内进行了大直径等长芯劲性搅拌桩单桩竖向承载力试验,并和相同直径灌注桩做了对比.试验结果表明,劲性搅拌桩成桩质量好,水泥土取芯单轴抗压强度高,可以为管桩-水泥土内界面提供足够的抗剪强度.大直径劲性搅拌桩极限承载力、单桩总侧阻力、端承阻力和同直径灌注桩相比均有大幅度提升,短劲性搅拌桩的端承比例更大且端阻发挥的时机更早.和同直径的灌注桩比,劲性搅拌桩提供相同的承载力所需的桩身长度大幅度减少,降低单位承载力造价.

Pile wall frame structures (PWFSs) are double-wall sheet-pile structures with an integrally precast framework of reinforced concrete to connect double rows of closely placed piles. An engineering test on a cofferdam of PWFSs was conducted in Binzhou, where lateral displacement along pile shaft was carefully monitored during the hydraulic filling process. A 3D finite element model (FEM) of the test was established to study the stability failure mechanism of PWFSs. Then, a design method for PWFSs was proposed through a structural stability analysis based on the limit equilibrium method, with special consideration of the cutting pile force influenced by row spacing. According to FE results, lateral pile displacements drawn from the FEM correspond well with field observations, and earth pressures applied on closely spaced piles are in line with Rankine's theory. Results of the theoretical analysis indicate that the control slip surface lies on the bottom of a soil layer with a poorer shear strength index. The effects of framework width, pile spacing, pile length and diameter on structural stability are also evaluated. The feasibility of PWFSs has been verified by an engineering test, and the simplified design method established here is reasonable and effective for structural stability prediction.

ABSTRACT The research of sediment movement on bed surface is one of the most important coastal problems around the world. In this paper, the vertical distribution formula of sediment concentration is improved by summarizing theoretical formulas of predecessors. A developed formula of total sediment carrying capacity is obtained by dimensional analysis. The formulae of sediment carrying capacity of suspended load and the bed surface deformation equation are derived by using micro element analysis method. The equation for calculating and simulating the erosion and deposition of the bed surface under the condition of stable bed surface is simplified. The flow around a cylinder is calculated and the distribution of erosion and siltation field is plotted.

针对深水软土地基,研究开发箱筒型基础结构,介绍箱筒型基础结构的应用情况.针对箱筒型基础结构可气浮的特点,提出一套气浮运输和定位、抽负压下沉安装的施工方法.该方法不需要大型起吊运输船舶,设备简单,下沉速度快,偏斜度容易控制,综合费用低.箱筒型基础结构对软土地基的适应性强、稳定好、施工便捷、投资省,具有良好的经济效益和社会效益.

The frame-fixed soldier pile structure (FSPS) is a new cofferdam structure of artificial island, with a notable feature of closely-spaced row-piles. Microstructure of soft soil has a significant effect on macroscopic physical quantities. The relationship between microstructure deformation characteristics of soft clay and shear strength index of soil was established by scanning electron microscope (SEM) test. Based on the subgrade reaction approach, a plane pole system finite element model (PPSFEM) was established to study displacement and internal force distribution along pile of FSPS under lateral load. The "load migrating" process was considered in the model that partial lateral load would transfer from rear pile to front pile via interior soil as interior soil reached the ultimate state. Study on how these factors affect the distribution of horizontal displacement and internal forces along pile has been performed through PPSFEM, including constraint form between frame structure and pile, m-values of subsoil and backfilling materials. The shear strength index of soil is significant affected by the microstructure. Parameter analysis indicates that the frame structure improves internal force distribution of pile foundation, that the feature of separated piles decreases the horizontal soil resistance of front pile, and that the articulated constraint form between pile and underpart of framework benefits to reduce the maximum bending moment of pile.

The compression characteristics and deformation parameters of the rubble-bedding of gravity quays are investigated by prototype compression test. Stones of 10～80 kg are randomly filled in a steel cylinder, and are imposed to varying levels of compression load. The load-deformation curves of the block stones and the circumferential strain of the steel cylinder are tested. The stress-strain curves and deformation parameters are finally obtained from combined experimental and finite element analysis. Five groups of samples with different initial void ratios and grading curves are studied by compression test of reciprocating loading and unloading. According to the test phenomena and data, the particle crushing characteristics, the compression characteristics and void ratios characteristics of the block stones are analyzed. The Poisson's ratio of the block stones can be assumed as a constant between 0.2 and 0.3. The compressive deformation moduli depend on the numbers of loading and unloading, which can be denoted as three compression modulus parameters of initial loading, secondary loading and multiple loading according to the value range. The stress-strain curve of the block stones in the rubble-bedding of gravity quays can be described piecewise by the corresponding modulus of compression according to the loading times of segmented load stress.

Purpose A new coupled model is developed to simulate the interaction between fluid droplet collisions on discrete particles (DPs) by using mathematic function.Design/methodology/approach In this model, the smoothed particle hydrodynamics (SPH) is used based on the kernel function and the time step which takes into consideration to the fluid domain in accordance with the discrete element method (DEM) with resistance function. The interaction between fluid and DPs consists of three parts, which are repulsive force, viscous shear force and attractive force caused by the capillary action. The numerical simulation of droplet collision on DPs presents the whole process of droplet motion. Otherwise, an experimental data were conducted to record the realistic process for verification.Findings The comparison result indicated that the numerical simulation is capable of capturing the entire process for droplet collision on DPs.Research limitations/implications However, based on the difference of experimental environment, type of the DP and setups, the maximum spreading dimeters of could not fit the experimental data exactly.Originality/value In sum, the coupled SPH-DEM method simulation shows that the coupled model of SPH-DEM developed an entire effectiveness process for fluid-solid interaction problem.

Circular foundations are widely employed in offshore engineering to support facilities and are generally subjected to fully three-dimensional loading due to the harsh offshore environmental load and complex operational loads. The undrained capacity of surface circular foundations on soil with varying strength profiles and under fully three-dimensional loading is investigated and presented in the form of failure envelopes that obtained from finite element analyses. The combined ultimate limit state of circular foundations is defined as the two-dimensional failure envelopes in resultant H-M loading space accounting for the vertical load and torsion mobilisation. The effects of vertical load and torsion mobilisation, soil shear strength heterogeneity and loading angle from moment to horizontal load on the shape of normalised H-M failure envelopes are explored. A series of expressions are proposed to describe the shape of failure envelopes obtained numerically, enabling essentially instantaneous generation of failure envelopes and optimisation of a circular foundation design based on constraint of any input variable through implementation in an automated calculation tool. An example application is ultimately provided to illustrate how the proposed expressions may be used in practice.