Laboratory Study on the Hydraulic Conductivity and Pore Pressure of Sand-Silt Mixtures

The hydraulic conductivity plays a major role on the excess pore pressure generation during monotonic and cyclic loading of granular soils with fines. This paper aims to determine how much the hydraulic conductivity and pore pressure response of the sand-silt mixtures are affected by the percentage of fines and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests performed on samples reconstituted from Chlef River sand with 0, 10, 20, 30, 40, and 50% nonplastic silt at an effective confining stress of 100 kPa and two relative densities (D_r = 20, and 91%) are presented and discussed. It was found that the pore pressure increases linearly with the increase of the fines content and logarithmically with the increase of the intergranular void ratio. The results obtained from this study reveal that the saturated hydraulic conductivity (k) of the sand mixed with 50% low plastic fines can be, on average, four orders of magnitude smaller than that of the clean sand. The results show also that the hydraulic conductivity decreases hyperbolically with the increase of the fines content and the intergranular void ratio.     

Field Study on the Behavior of Destructive and Non-Destructive Piles Under Compression

This paper presents a series of full-scale load tests on long bored piles instrumented with strain gauges along the shafts, including eight field tests of piles loaded to failure and one non-destructive pile load test. The load-displacement response, skin friction, end resistance, and the threshold of the pile-soil relative displacement for fully mobilizing skin resistance were discussed. A simple softening model was proposed to describe the degradation behavior of the skin friction along the pile-soil interface and the load-displacement relationship developed at the pile base. It is found that the shaft resistance degradation investigated in the non-destructive load test only occurs at a shallow depth, and the skin friction of deeper soil is not fully developed. However, unlike the results of the non-destructive load tests, the softening is accompanied by a reduction in skin friction and observed to be along the whole pile depth. The thresholds of pile-soil relative displacement for fully mobilizing skin resistances in different soils have been found to be in the range 0.6% to 2.4% of the pile diameter. Moreover, in practical applications, a bilinear model is assumed to be feasible in analyzing the load-settlement relationship developed at the end of non-destructive pile, whereas the load transmission curve of the soils below the pile base corresponds to a softening model in the field tests of piles loaded to failure.     

两种混养方式对异枝江蓠(Gracilaria bailinae)生长性能、表面附生细菌群落及抗生素抗性基因的影响

为揭示"鱼-藻"和"鱼-虾-藻"混养对异枝江蓠(Gracilaria bailinae)生长性能、表面附生细菌群落和抗生素抗性基因(antibiotic resistance genes,ARGs)的影响,阐明异枝江蓠表面附生细菌群落与生长性能、ARGs之间的关系,利用16S rDNA高通量测序技术和Real-time qPCR技术分析了异枝江蓠表面附生细菌群落和ARGs的组成与差异,冗余分析(RDA)探讨细菌群落与生长性能、ARGs之间的关联。结果表明:(1)"鱼-虾-藻"混养会促进异枝江蓠的生长性能,增加表面附生细菌群落的多样性。(2)异枝江蓠表面附生细菌群落主要属于变形菌门、蓝藻门、浮霉菌门和拟杆菌门,不同混养方式中优势菌属组成不同,"鱼-虾-藻"混养优势菌属多样性较高。(3)"鱼-虾-藻"混养的异枝江蓠ARGs/MGEs的相对丰度大多高于"鱼-藻"混养。(4)RDA分析表明,生长性能主要与Ralstonia、Blastopirellula等显著相关,ARGs/MGEs主要与Nitrosomonas、Alteromonas、Pleurocapsa;CC-7319等显著相关。"鱼-虾-藻"混养能够增强异枝江蓠的生长性能,提高异枝江蓠表面附生细菌群落的多样性。但"鱼-虾-藻"混养能够增加异枝江蓠ARGs/MGEs的相对丰度,存在一定的生态风险。因此,在注重经济效益的同时也要关注可能存在的对人类健康的危害。研究结果将有助于海水养殖环境的优化,为大型海藻在海水养殖业中的应用与推广提供理论基础。     

C60全珊瑚海水混凝土的钢筋锈蚀行为研究

采用线性极化电阻法,测试了C60全珊瑚海水混凝土（coral aggregate seawater concrete,简称CASC）的线性极化曲线、自腐蚀电位（E_corr）和极化电阻（R_p）,研究了不同暴露时间、不同种类钢筋CASC的钢筋腐蚀行为,提出了提升岛礁CASC结构耐久性的建议措施。结果表明：随着暴露时间的延长,CASC的E_corr和R_p均逐渐降低,钢筋的耐蚀性能逐渐减弱。不同种类钢筋CASC耐蚀性能规律为：316不锈钢筋优于有机新涂层钢筋,优于普通钢筋。即使暴露0 d,CASC中普通钢筋仍会发生锈蚀,表明普通钢筋在不附加任何防腐措施的条件下不适用于岛礁CASC结构。综合分析阻锈效果和成本因素,316不锈钢筋的性价比明显低于有机新涂层钢筋,建议岛礁CASC工程优先选用有机新涂层钢筋。     

Calibration of LRFD Format for Steel Jacket Offshore Platforms in China Offshore Area （ 1 ） ： Statistical Parameters of Loads and Resistances

1 .IntroductionThe structural design method has evolvedfromthe workingstress method,damage stage methodtolimit state method.The more recent probabilisticlimit state design method,whichis based onreliabili-tytheory,has beengenerallyacceptedinthe designcode…     

问题中的理论平均波阻(英文)

利用准三维的ｆＫｄＶ方程和四区间划分法,理论给出了任意截面的直渠道中先锋孤立子生成的理论平均波阻和区间平均能量的时间变化率。基于ｆＫｄＶ方程系数的正则性,文中结果是Ｘｕ等人结果的一个推广。对具有相同截面面积的正方形和等腰三角形截面的渠道及在不同强迫源和强迫源速度条件下,对理论平均波阻和平均生成能的时间变化率进行了数值比较和理论预报。比较指出,理论和数值结果吻合得很好。     

A two-dimensional finite volume hydrodynamic model for coastal areas: Model development and validation

A two dimensional implicit finite volume scheme for solving the shallow-water equations is developed. The effects of the Coriolis force, surface wind stress, and waves are included. A non-uniform rectilinear forward staggered grid is used with Cartesian coordinates. The time integration is performed using the Euler implicit technique. The convective flux is treated using the deferred correction method. The viscous terms are discretized using a second order central difference approximation. The SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm is used for coupling the velocity components and the water elevation gradient for the water level correction. The system of equations is solved sequentially using the Strongly Implicit Procedure (SIP). To simulate wave driven current, a phase averaged wave model is used first to simulate wave transformation and calculate radiation stresses. The performance of the developed model is validated for different sources of external forces and different combinations of boundary conditions. The validation cases include tidal circulation in a harbor and wave induced currents behind a breakwater parallel to the coastline. The model is finally applied to simulate the flow pattern in a closed artificial lagoon and along the coastline near Damietta Port located along the Northern coast of Egypt. Results of the developed model agree well with the published results for the considered cases.     

Model Test of Sand Restraining Force on Pipeline

This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theory is verified. The effect of cyclic loading is considered in the test.     

先锋孤立子生成的理论平均波阻(Ⅰ).理论

根据作者导得的AfKdV方程，理论上确定了先锋孤立子生成问题的理论平均波阻，能量劈分及能量劈分比。本文的能量劈分是确定先锋孤立子生成参数的理论基础。同时，本理论确定了现有理论中的自由未知参数问题，从而使先锋孤立子生成参数得到理论预报。     

海上平台桶基负压沉贯阻力与土体稳定数值计算研究

用有限元分析方法对桶形基础负压沉贯过程中流场进行动态模拟,提出桶形基础沉贯阻力计算方法和土体稳定有限计算方法,提出桶内土体稳定性判断准则,计算结果表明所提方法是合理的,并具有工程实用性。