Numerical evaluation of soft inter‐slab joint in concrete‐faced rockfill dam with dual mortar finite element method          下载免费PDF全文

Mozhen Zhou  Bingyin Zhang  Chong Peng 《国际地质力学数值与分析法杂志》2018,42(5):781-805

Recently constructed concrete‐faced rockfill dams (CFRDs) often use soft inter‐slab joints to prevent axial compression‐induced extrusion damage in the concrete face. Due to the complexity of the multibody contact and the lack of information on the actual behavior of soft joints, it is highly challenging to numerically assess the effect of soft joints in CFRDs. In this paper, we present a numerical approach for the three‐dimensional modeling of CFRDs with hard and soft joints. A dual mortar finite element method with Lagrange multiplier is developed to treat the multibody contact in hard joints with impenetrability condition. The soft joint slab‐filler‐slab contact system is modeled using an equivalent contact interface approach, where the soft contact constraints are imposed using a perturbed Lagrange formulation. Through a series of laboratory tests, the mechanical behavior of soft joint is investigated. An extrusion model for the soft joint is presented and implemented in the dual mortar finite element method. The proposed numerical method is applied to the three‐dimensional analysis of Tianshengqiao‐1 CFRD. Despite the complex multibody contact and strong material and geometry nonlinearities in the CFRD, the proposed method is stable and capable of capturing salient characteristics of the CFRD. Numerical results show that in Tianshengqiao‐1, the employment of soft joints can effectively reduce the axial compression stress, thus greatly alleviating the risk of extrusion damage in the concrete face.  相似文献   

黑海参(Holothuria atra)对环境沉积物的摄食选择及消化系统功能适应性研究     

薛英楼  高菲  许强  黄端杰  王爱民  孙涛 《海洋与湖沼》2019,50(5):1070-1079

黑海参(Holothuria atra)是热带珊瑚礁大型底栖动物群落中的代表种类之一,其摄食活动对珊瑚礁生境底质有机物的循环再利用具有重要作用。本文研究了三亚蜈支洲岛典型热带珊瑚礁海域野生黑海参的沉积物选择特征及其触手和消化系统结构功能的适应性。结果表明,黑海参摄取的沉积物颗粒相对较粗,其中粒径0.25mm部分占到了总重量的96.67%。触手上3—6个乳突形成乳突簇[直径(283.00±40.94)μm],适宜摄取大颗粒沉积物。黑海参胃内含物有机物含量显著高于环境沉积物,证实其对有机物含量的选择性;粒径0.25mm部分有机物含量占摄入总有机物量的75%,与环境沉积物中相同粒度的有机物总量占比接近(76%),表明黑海参选择的沉积物粒径范围有效保证了其高效摄入有机质。黑海参前肠的脂肪酶、淀粉酶、纤维素酶、胰蛋白酶活性最高,同时绝大部分的有机质(98.33%)在前肠被吸收。组织学定量分析表明,黑海参前肠黏膜层厚度最大,占总厚度的56.33%,这与其高效吸收有机质的功能相适应;后肠的肠壁总厚度和黏膜下层、肌层厚度均显著高于前肠和中肠,表明其具有相对更好的弹性和收缩能力,适合于大颗粒有机质的高效输送与排出。研究结果证实,黑海参摄食器官和消化道独特的结构与功能保证了其在珊瑚砂粗颗粒生境中高效摄取有机物。  相似文献   

Analytical modeling on consolidation of stiffened deep mixed column-reinforced soft soil under embankment     

Zhen Zhang  Fengrui Rao  Guanbao Ye 《国际地质力学数值与分析法杂志》2020,44(1):137-158

Stiffened deep mixed (SDM) column is a new ground improvement technique to improve soft soil, which can be used to increase bearing capacity, reduce deformation, and enhance stability of soft soil. This technique has been successfully adopted to support the highway and railway embankments over soft soils in China and other countries. However, there have been limited investigations on its consolidation under embankment loading. This paper developed an analytical solution for the consolidation of embankment over soft soil with SDM column in which core pile is equal to or shorter than outer DM column. The consolidation problem was simplified as a consolidation of composite soil considering the load shear effect of core pile. The developed solution was verified by a comparison with the results computed by three-dimensional (3-D) finite element analysis. A parametric study based on the derived solution was conducted to investigate influence factors—length of core pile, diameter of core pile, diameter of SDM column, modulus of DM column, and permeability coefficient of DM column—on the consolidation behavior of SDM column-supported embankment over soft soil. The developed solution was applied to a case history of SDM column-supported embankment, and a good agreement was found between the predictions and the field measurements.  相似文献   

A study of coral reef resilience and implications of adaptive management and rehabilitation in Khanh Hoa Province, Vietnam     

VO Si Tuan  HUA Thai Tuyen  PHAN Kim Hoang 《海洋学报(英文版)》2019,38(1):112-117

The Province of Khanh Hoa, Vietnam, is located in the western South China Sea and boasts a shoreline of 385 km and many islands. Previous studies have indicated the extreme diversity and abundance of coral reefs in its waters as compared with other coastal provinces of Vietnam. A study on the resilience of coral reefs against increased surface water temperature and anthropogenic impact is conducted at 19 reef sites in 2015. At each site, a series of parameters (e.g., coral covers, genus diversity, and coral recruitment, substratum heterogeneity, depth, water exchange level, and sediment deposit and water temperature) are measured quantitatively or semi-quantitatively. The measured data are rated based on the relationship between the parameter values and coral susceptibility; the consideration that reef health reflects the biological capability to adapt to environmental changes and the recruitment potential if bleached; and positive or negative influences of physical factors in the mitigation of thermal stress and protecting corals from bleaching. A cumulative analysis enables researchers to divide the studied reefs into four categories based on varying levels of reef health to support resilience, recovery, and vulnerability in the case of increased water temperature. Relevant management interventions for each category and other supporting activities are suggested to enhance management effectiveness and to plan the rehabilitation of coral reefs for biodiversity conservation and touristic development, taking into account the involvement of related stakeholders.  相似文献   

西沙群岛基底火山碎屑岩中单斜辉石的矿物化学特征及其地质意义     

李诗颖  余克服  张瑜  陶士臣  严宏强 《海洋学报》2019,41(7):65-76

本文利用电子探针对南海西沙群岛琛航岛珊瑚礁底部火山碎屑岩中的单斜辉石矿物的化学特征进行了研究。结果表明，该单斜辉石属于富钙透辉石，部分有正环带结构，从核部到边部Ca、Fe、Ti的含量逐渐增加，是岩浆正常结晶顺序的反映，说明该区域的岩浆演化是向着富Ca、Fe、Ti方向发展的。主量元素数据显示，单斜辉石具有低Si高Al的特征(SiO₂=41.40%～48.44%，Al₂O₃=5.54%～10.20%)，且AlⅣ含量较高，说明母岩浆为不饱和碱性岩浆系列；此外，单斜辉石Ca含量偏高，Ca/(Ca+Mg+Fe)值在46.1%～51.4%之间，推测是母岩浆的高Ca含量导致了大量高钙辉石的产出。结合西沙海域的地震和构造资料，推测琛航岛珊瑚礁的基底是玄武质火山碎屑岩组成的平顶状海山，系岩浆穿过断裂发育的岩石圈层在西沙群岛的海底喷发，随后火山碎屑物质经过堆积、固结作用而形成；该火山碎屑岩的原岩为板内碱性玄武岩。  相似文献   

Numerical predictions of the behaviour of soft clay with two anisotropic elastoplastic models     

Paulo J. Venda Oliveira  Luís J.L. Lemos 《Computers and Geotechnics》2011

The numerical predictions obtained with the Melanie and MIT-E3 models are compared. Firstly, the performance of the constitutive models is checked against undrained triaxial tests. The models are then used to replicate the behaviour of an embankment built on soft clay. The numerical results are compared with the field data in terms of settlements, lateral displacements and excess pore pressures. Additionally, the numerical predictions are also analysed in terms of yield area, contours of vertical effective stresses, horizontal effective stresses and shear stresses and in terms of effective stress paths.  相似文献   

新厝公路拓宽工程软土路基施工监测分析     

郭锡斌 《福建地质》2011,30(4):352-356

福清新厝公路拓宽海堤段海堤内侧采用分级加载进行路基施工填筑软基加例处理,通过3个断面监测数据分析,最大水平位移日变量为2．28mm／d,最大沉降速率为5．97nm/d,各测点的沉降速率和水平位移均在安全控制范围之内。至监测末期最大总沉降量占淤泥层厚度7％,海堤地基固结度76．3％～85．0％,但尚有10．9～15．8m...  相似文献   

上覆压力及排水条件对吹填软土强度影响   总被引：1，自引：0，他引：1  

杨爱武  闫澍旺  杜东菊  赵瑞斌  卢力强  王江宏 《岩土力学》2011,32(1):172-178

吹填土由于其成分来源及沉积环境不同,性质千差万别。以天津海积软土为土质材料,模拟现场吹填环境,研究了吹填软土强度形成影响因素。试验表明,不同的压力及排水条件对吹填软土强度增长影响较大。当排水条件有利于土体中的水排出时,强度增长明显。上覆压力对土体强度增长的影响通过一定的排水条件得以实现,排水条件差和压力增大时,强度增长缓慢且很小,反之,强度增长快且绝对值大。  相似文献   

某软土地区深基坑开挖数值模拟分析     

邴启超  马永峰  张志豪 《中国勘察设计》2011,(2):73-75

以某软土地区深基坑开挖为背景,运用有限元方法计算模拟了基坑开挖的不同阶段,分析不同工况下基坑及周围土体的变形和受力情况,并对不同施工方式下基坑变形和受力进行了对比分析。数值分析表明软土地区深基坑开挖时,需采取相应的施工措施,控制基坑变形和受力,确保工程安全顺利进行。研究结论可为类似工程提供借鉴与参考。  相似文献   

基于灰色理论的真空堆载预压分层沉降预测     

赵鹏洲  印长俊 《岩土工程技术》2011,25(1):13-16

对真空堆载预压加固处理的软土地基,用灰色理论模型预测地基的分层沉降,结果表明：对于土层分布均匀的地基,verhulst模型能较准确地预测分层沉降,误差在10％以内。对于土层分布不均匀的地基,verhulst模型预测误差较大,进行残差修正,修正的verhulst模型能较准确地预测分层沉降。用不同点数预测地基的分层沉降,同实测沉降数据对比发现、对于土层均匀或不均匀的软土地基,在已知真空影响范围外土层的沉降时,灰色模型就能较准确地预测分层沉降。  相似文献