红粘土动本构关系与动模量衰减模型

针对高速交通循环荷载下红粘土路堑基床的动力稳定性问题,基于大量室内动三轴试验,研究了不同试验条件下原状结构红粘土动本构关系及动模量衰减规律。试验成果表明:原状结构红粘土动本构关系仍可用R.L.Kondner双曲线模型描述;动模量随动应变的增大非线性减小,具有明显的应变软化特征。围压、固结比、含水比对红粘土动本构特征及动模量衰减规律均有明显影响。不考虑其它因素,随围压或固结比的增大,动本构曲线逐渐偏向应力轴,随含水比的增大,动本构曲线逐渐偏离应力轴。同等条件下,动模量随围压、固结比的增大而增大,随含水比的增大而减小。基于回归分析,给出了不同试验条件下原状结构红粘土双曲线模型参数、动模量衰减经验公式及其拟合参数。     

响水海上风机群桩基础变形特性的有限元分析

江苏省响水海上风电场位于响水县陈港附近海域。由于海上风机群桩基础复杂的工程特性,地基基础设计是该工程的技术难题之一。考虑了静力工况和循环风荷载工况,对响水2 MW风力发电机组群桩基础的变形特性进行了计算和分析。计算结果表明,静力荷载工况下基础变形在允许范围内,考虑循环风荷载时的变形较静力荷载工况的方案略有增大;桩土系统随着深度水平位移和影响范围逐渐减小,竖向最大沉降量基本不变,影响范围有一定扩展;桩土系统的受力变形特性不仅取决于所受到的荷载组合,也取决于地基条件。     

动荷载作用下饱和砂土动剪模量试验研究

在50kPa、100kPa和200kPa 3种固结压力下分别对饱和度为95%、92%、88%和83%的土样进行了循环单剪试验,得到了该土样在4种饱和度、3种固结压力下的最大动剪模量Gdmax以及动剪模量比G/Gdmax-γ归一化曲线。分析得出,同一固结压力下土样的Gdmax和G/Gdmax随着饱和度的增大相对减小;随着固结压力的增大,两者数值上差异逐渐减小。最后对此种现象进行了讨论并分析了其产生的原因。     

Intergrain contact density indices for granular mixes-Ⅰ: Framework

Mechanical behavior such as stress-strain response, shear strength, resistance to liquefaction, modulus, and shear wave velocity of granular mixes containing coarse and fine grains is dependent on intergrain contact density of the soil. The global void ratio e is a poor index of contact density for such soils. The contact density depends on void ratio, fine grain content (CF), size disparity between particles, and gradation among other factors. A simple analysis of a two-sized particle system with large size disparity is used to develop an understanding of the effects of CF, e, and gradation of coarse and fine grained soils in the soil mix on intergrain contact density. An equivalent intergranular void ratio (ec)eq is introduced as a useful intergrain contact density for soils at fines content of less than a threshold value CFth. Beyond this value, an equivalent interfine void ratio (ef)eq is introduced as a primary intergrain contact density index. At higher values of CF beyond a limiting value of fine grains content CFL, an interfine void ratio ef is introduced as the primary contact density index. Relevant equivalent relative density indices (Drc)eq and (Drf)eq are also presented. Experimental data show that these new indices correlate well with steady state strength, liquefaction resistance, and shear wave velocities of sands, silty sands, sandy silts, and gravelly sand mixes.     

循环振动导致黄河口潮坪土成分结构变异研究

在黄河三角洲潮坪采集循环振动荷载施加前后长1 m的原状样各一个,在实验室对原状样以10 cm为间隔取样,进行粒度成分分析和微结构观测,研究循环振动荷载导致的海床土成分与结构的变化。发现总体上振动导致土体颗粒长轴呈现竖向排列趋势,深0~40 cm的表层土细粒含量增高,级配变好;深40~70 cm土体细粒含量降低,级配变差;70 cm以下土体受振动影响不明显。现场海床土孔隙水压力监测结果表明,这种海床土的成分结构变异与循环荷载导致土体重复液化及渗流场作用有关。     

Assessment of cyclic response to suction caisson in clay using a three-dimensional displacement approach

An investigation was made to present analytical solutions of cyclic response to suction caisson subjected to inclined cyclic loadings in clay using a three-dimensional displacement approach. A model representing the relationship between vertical load and vertical displacement and that between lateral load and lateral displacement along the skirt of suction caisson subjected to cyclic loadings is proposed for overconsolidated clay. For the effect of vertical load on cyclic load capacity of suction caisson, using the Mindlin solution in the case of a vertical point load, the vertical stress of soil under the base of suction caisson is presented. For the stress state of soil beneath the base of suction caisson subjected to cyclic loading, the Mohr–Coulomb failure line and critical state line are presented and the relationship between total stress, effective mean principal stress, stress difference, and pore-pressure is elucidated. The comparison of results predicted by the present method for a suction caisson subjected to cyclic loadings in clay has shown good agreement with those obtained from field tests. Cyclic behavior of clay up to failure is made clear from the relationship between cyclic tensile load, vertical and lateral displacements, and rotation and that between depth, vertical, and lateral pressures.     

海水工厂化养殖废水循环利用的初步探讨

以海水工厂化养殖排出的废水养殖双齿围沙蚕(Perinereis aibuhitensis)、菲律宾蛤仔(Ruditapes phi-lippinarum)、长牡蛎(Crassostreagigas)和细基江蓠(Gracilariatenuistipitata).结果表明:双齿围沙蚕耐污染能力最强;细基江蓠和双齿围沙蚕具有较强的净化水质能力.养殖废水经7 d处理后,NH4+-N、NoO3--N、NO2--N、PO43--P、COD和底质有机物分别下降至处理前的11.20%、23.69%、27.50%、14.6%、3.2%和0.32%,且沙蚕和江蓠平均日生长率分别为2.30 mg/g·d和80 mg/g·d.该方法不但能净化水质,还能实现养殖废水的循环利用.     

Influence of Frequency on the Behaviour of Plate Anchors Subjected to Cyclic Loading

This article reports the response of embedded circular plate anchors to varying frequencies of cyclic loading. The effects of time period of loading cycles and pre-loading on movement of anchors and post-cyclic monotonic pullout behavior are studied using a model circular (80 mm diameter) plate anchor, buried at embedment ratio of six in a soft saturated clay. The frequencies of loading cycles have showed considerable effect on movement of anchors. For given duration of loading, higher frequency cycles cause more movement of anchor than lower frequency cycles. Pre-loading reduces the movement of anchors in subsequent loading stages. When anchors are recycled at a load ratio level less than the pre-cycling load, the movement of anchor in recycling phase are very much reduced, but if the recycling is done at a higher load ratio level, the effect is not that much pronounced and the anchors behave as if they were not subjected to any cycling load in the past. Anchor subjected to cyclic loading and then monotonic pullout shows an increase in initial stiffness, whereas the peak pullout load was found to decrease marginally over that of an anchor not subjected to any cyclic loading. For the present test conditions, the relative post-cyclic stiffness of anchors is found to vary from 1.169 to 1.327.     

Cyclic Sequences, Events and Evolution of the Sino-Korean Plate, with a Discussion on the Evolution of Molar-tooth Carbonates, Phosphorites and Source Rocks

This paper gives an account of the research that the authors conducted on the cyclic sequences, events and evolutionary history from Proterozoic to Meso-Cenozoic in the Sino-Korean plate based on the principle of the Cosmos-Earth System. The authors divided this plate into 20 super-cyclic or super-mega-cyclic periods and more than 100 Oort periods. The research focused on important sea flooding events, uplift interruption events, tilting movement events, molar-tooth carbonate events, thermal events, polarity reversal events, karst events, volcanic explosion events and storm events, as well as types of resource areas and paleotectonic evolution. By means of the isochronous theory of the Cosmos-Earth System periodicity and based on long-excentricity and periodicity, the authors elaborately studied the paleogeographic evolution of the aulacogen of the Sino-Korean plate, the oolitic beach platform formation, the development of foreland basin and continental rift valley basin, and reconstructed the evolution     

岩石单轴压缩试验Kaiser效应实质的研究

岩石 Kaiser效应具有记忆先前应力、纵向应变和横向应变的能力 ,记忆的准确程度随加载阶段不同而不同。为了解 Kaiser效应的记忆实质 ,通过岩石单轴压缩试验确定 Kaiser效应对体积应变、弹性模量和泊松比三项物性参数的记忆能力。结果表明 ,岩石 Kaiser效应具有记忆先前物性参数的能力 ,其中尤以对弹性模量的记忆能力表现为最好 ,而且受时间因素影响不大 ,说明岩石 Kaiser效应的实质是对其内部物理特性的记忆