应力幅值比对土-结构接触面非共轴特性影响研究

运用80 t大型三维多功能土工试验机（3DMAS）,进行了不同应力幅值比下粗粒土与结构接触面大型三维循环直剪试验,深入分析了应力控制往返椭圆剪切路径下接触面切向位移、非共轴角和剪切柔度等三维力学特性以及应力幅值比的影响规律。应力控制往返椭圆剪切路径下,接触面产生了明显的x向和y向位移、非共轴角和剪切柔度。x向和y向位移幅值、剪切柔度峰值均随循环剪切的进行逐渐减小而后趋于稳定,表现出演化特性。非共轴角受切向应力幅值及切向应力增量方向共同影响,其最值、稳定值随循环周次基本保持不变;正向剪切时非共轴角最大值（最小值）与反向剪切时最小值（最大值）基本出现在同一位置。接触面剪切柔度与非共轴角随旋转角度的变化趋势相反,剪切柔度的增加会抑制非共轴角的发展,反之亦然,两者对立统一。应力幅值比对接触面切向位移间椭圆关系及其时程变化形式、切向应力位移类椭圆关系等影响较小,主要影响切向位移幅值及其偏移程度、切向位移间椭圆关系的长短轴大小及方向、切向应力位移类椭圆关系的长短轴大小、非共轴角的数值及其随旋转角度的变化形式和最值出现位置、剪切柔度随旋转角度的变化形式和峰值及其产生位置等。应力幅值比越大,切向位移幅值越大、向负向偏移越大,剪切柔度峰值越大,随循环剪切的进行减小的速率越慢。应力幅值比ξ_τ=1和ξ_τ≠1时接触面非共轴角和剪切柔度随旋转角度的发展变化形式差别很大。     

列车动荷载下桩网结构路基土拱效应试验研究

通过三维模型试验研究了列车动荷载作用下的土拱效应。试验结果表明,动荷载作用下土拱效应依然有效,随着填土的增高,土拱效应在增强,土工格栅的存在可以增强土拱效应的作用。但动荷载条件下动应力的分布与自重条件下的应力分布截然不同。动荷载作用下土拱效应会发生退化,表现为动荷载施加过程中先前由桩所承担的部分动应力会转移至桩间土;完成动荷载施加后,最初由桩承担的部分自重荷载也会转移至桩间土。填土高度和土工格栅对于动荷载作用下土拱的稳定性有很大的影响,但当高度达到一定值之后,填土高度的影响就可忽略,土工格栅的存在使得土拱效应的削弱程度减小了一半。     

Storm Surges from Extra-Tropical Cyclones

The possible influence of climate change on the tracks of the extra-tropical cyclones as well as storm surges is studied. Two differentdata bases have been used: one for the Great Lakes of North America and the otherfor the German Bight in the North Sea of Europe. For the Great Lakes region,significant east-west and north-south shifts in the tracks of ETC'S with decadal periodicities have been observed. However, there was no trend in the amplitudes of storm surges. The most important result for the Great Lakes is that, depending upon its position relative to the constantly shifting storm tracks, a given location could eitherexperience a major storm surge or could miss out completely.The storm surges in the German Bight in general, and at Cuxhaven in particular, appear to show a slightly increasing trend in the latterpart of the 20th century. However, the most significant result for the German Bightis that the number of storm tides (i.e., multiple peaks in a given storm surge event)definitely has shown an increase in the second half of the 20th century. This increase isinterpreted as due to the influence of meso-scale weather systems embedded in the synoptic scale ETCs.     

冻土路基在地震作用下的动力响应

青藏高原是地震多发区,冻土区的公路、铁路在地震作用下的动力响应必须考虑．将冻土作为黏弹塑性材料,考虑冻土在动力荷载作用下的热力耦合效应,从热传导方程、渗流微分方程和动力平衡方程出发,建立了冻土的动力热一力耦合微分方程．根据相应的有限元列式,对路基在地震荷载作用下的动力响应进行了计算与分析．     

南阳膨胀土的工程地质特征和填筑适宜性

施工阶段的工程地质调查发现,宁（南京）西（西安）铁路内乡-镇平段南阳膨胀土成因类型上不仅有第四系冲积洪积粘土,而且发育上第三系湖相沉积粘土。不同成因的膨胀土具有不同的空间分布特征和工程性质,X射线衍射测试表明,南阳膨胀土的主要膨胀性粘土矿物是伊利石/蒙脱石混层矿物。物质组成和物理化学性质差异导致击实土在含水量变化条件下膨胀力和膨胀变形有明显的差别;对同一种膨胀土材料,其击实含水量越小,膨胀性越强,甚至含水量降低1 %～2 %,膨胀力就可以增加到200 %以上;击实膨胀土的直剪强度受到钙质结核含量的影响,对于膨胀势为高或强的膨胀土,结核含量小于15 % 时,经过干湿循环后直剪强度衰减量为40 %～65 %,结核含量为25 %～30 % 的强膨胀土直剪强度衰减量则低于30 %;对膨胀土的地质特征、工程性质、击实土的膨胀性和直剪试验结果进行分析,探讨其用于填筑铁路路基的适宜性,进行了填筑适宜性分级。依据研究成果制定的路基施工工艺取得了比较理想的工程效果     

Modeling of embankment beneath marine deposited soft sensitive clays considering straightforward creep degradation

Abstract

One method straightforwardly describing the creep degradation behavior of soft marine clay is proposed and applied to the embankment modeling. Based on the experimental phenomena, the evolution of creep coefficient of soft structured clay is identified comparing with reconstituted clay, and formulated using the creep coefficient of reconstituted clay and a creep-based structure parameter relating to the inter-particle bonding. The contributions of inter-particle bonding and debonding to creep coefficient are thus considered and the creep degradation behavior is then captured straightforwardly. The creep coefficient is extended to 3D and incorporated into a newly developed elasto-viscoplastic model to describe the creep degradation in a direct way. Based on the correlations, the liquid limit is adopted as the viscosity related input parameter. The model is derived using Newton–Raphson algorithm and implemented into a Finite Element code for coupled consolidation analysis. The general applicability on creep degradation of the model is validated by simulating 1D creep, 1D CRS (constant strain rate) and 3D undrained creep tests. Finally, the enhanced model considering creep degradation is applied and validated by simulating one test embankment and one test fill on marine deposited soft sensitive clays.     

TY型管节点局部柔度的参数分析及试验研究

由于海洋平台管节点的局部柔度对平台结构的静动力性能有重要影响，如何确定各类管节点的局部柔度成为一个重要的研究课题。本文用半解析方法计算了海洋平台中一类常见的管节点──ＴＹ型管节点的局部柔度，并用回归方法得出了计算ＴＹ型管节点局部柔度矩阵中各元素的参数公式。本文还介绍了对一组ＴＹ型管节点ＰＶＣ塑料模型进行的局部柔度试验。参数公式计算结果与模型试验结果的比较表明，本文得出的参数公式是基本可靠的，建议可在海洋平台总体结构分析中使用。     

Study on roughness coefficient for unsubmerged reed in the Changjiang Estuary

The influence of density,foliage and stem flexibility on the roughness coefficients under unsubmerged conditions,such as Manning’s n,is investigated experimentally.An instrumentation system has been developed for measuring the flow rate ranging from 0.1 to 0.3 L/s under the condition of different artificial foliated reeds.Based on the experimental results,the influence on the relationship between n with different density,foliage,flexibility and flow depth is discussed.It is found that the foliage and the density are the important factors affecting Manning’s n.At a range of relatively low velocity and relatively large bending stiffness of stem,Manning’s n is not influenced significanthy by the flexibility of stem.     

堤下爆炸法处理淤泥地基新工艺的理论、实验及工程应用(Ⅰ)堤下爆炸法的理论及实验研究

在淤泥质海岸建造高桩码头,通常在开挖基槽后沉桩再抛石形成棱体。基槽中的回淤淤泥很难清除,为此研制了堤下爆炸挤淤新工艺。本文是关于该新工艺的理论、实验及工程应用的一个总结,分两部分,第一部分着重介绍挤淤机理、装药工艺、模型律及药量公式等。研究及应用表明,这种新工艺与先前我们研制成功的爆夯法及爆填法一起,构成了较为完整的工艺系列。     

South Africa's coastal-breeding white-breasted cormorants: population trends,breeding season and movements,and diet

White-breasted cormorants Phalacrocorax [carbo] lucidus breed around South Africa's coast and at inland localities. Along the coasts of the Northern, Western and Eastern Cape provinces, numbers breeding were similar during the periods 1977–1981 (1 116 pairs at 41 localities) and 2008–2012 (1 280 pairs at 41 localities). Along the coast of KwaZulu-Natal (not counted in 1977–1981), 197 pairs bred at nine localities in 2008–2012, when the overall number breeding around South Africa's coastline was about 1 477 pairs. Between the two study periods, numbers decreased in the Northern and Western Cape provinces following the loss of several breeding localities, but they increased in the Eastern Cape. In the Western Cape, however, numbers were stable east of Cape Agulhas and at nine well-monitored West Coast localities that were surveyed from 1978 to 2012. White-breasted cormorants breed throughout the year, with breeding at some localities more seasonal than at others and the timing of peaks in breeding varying at and between localities. In the vicinity of Saldanha Bay/Langebaan Lagoon (Western Cape), in Algoa Bay (Eastern Cape) and in northern KwaZulu-Natal, it is likely that birds moved between breeding localities in different years, although breeding often occurred at the same locality over several years. Human disturbance, presence of predators, competition for breeding space and occurrence of breeding by other waterbirds may influence movements between colonies. Securing sufficient good habitat at which white-breasted cormorants may breed will be important for conservation of the species. The species may breed at an age of 4 years, possibly younger. The bulk of their diet around South Africa's coast consists of inshore marine and estuarine fish species that are not intensively exploited by humans.