Investigation of scour effect on tensile capacity of suction caissons considering stress history of sand     

Jinzhong Liu  Zhende Zhu  Baotian Wang 《Marine Georesources & Geotechnology》2013,31(9):1044-1056

Abstract

Since the pull-out response of upwind caissons governs the design of multi-caisson foundations, it is worthwhile to study scour effect on the tensile capacity of suction caissons. The tensile capacity of suction caissons after scour is relevant to the scour depth and the pressure under the caisson lid: the tensile capacity decreases dramatically with increasing scour depth; the smaller the pressure, the stronger the weakening effect of scour. Moreover, the scour effect is investigated in two cases: ignoring stress history and considering stress history. The results show that tensile capacity after scour is larger when the stress history is considered, so ignoring the stress history leads to a conservative design. In order to quantitatively evaluate the effect of scour depth and pressure, an empirical formula for the tensile capacity of suction caissons after scour is proposed based on multiple regression analysis.  相似文献   

Characteristics of Parameters for Local Scour Depth around Submarine Pipelines in Waves     

Sungduk Kim  Ju-Heum Yeon 《Marine Georesources & Geotechnology》2013,31(2):162-176

The purpose of this study is to investigate the characteristics of parameters for local scour depth around submarine pipes due to waves. Because it is impossible to consider all the factors that influence the scour, it is reasonable to investigate the correlations between parameters and scour. The experimental works about scour were performed for the conditions of 40, 60, 90 m pipe diameter, various wave periods, and wave height in the case of horizontal bed and 1/10 slope bed, respectively. Analyzing the results of experiments, the Reynolds number, Shields parameter, Keulegan-Carpenter number, Ursell number, and Modified Ursell number were estimated. The correlations between the relative scour depth, which is the maximum equilibrium local scour depth divided by the pipe diameter, and 5 parameters were analyzed. It was shown that there was hardly any correlation with the Reynolds number. In the case of a horizontal bed, the Keulegan-Carpent number had the highest correlation, but in the case of the slope bed the correlation was greatly reduced. The modified Ursell number showed a high correlation regardless of the type of bed.  相似文献   

弯曲河流斜槽裁弯模式与发育过程   总被引：1，自引：0，他引：1       下载免费PDF全文

李志威  王兆印  赵娜  余国安 《水科学进展》2013,24(2):161-168

结合遥感影像、野外调查和形态统计,深入分析斜槽裁弯现象,将其划分为切滩冲刷、串沟冲刷和主流顶冲3种模式。切滩模式发生于洪水期间主流水流动力轴线偏向凸滩后,形成漫流水流冲刷,极可能在边滩形成新的斜槽。切滩裁弯的形态统计表明,弯道曲率半径与平均河宽之比约2.92,分流角约54.8°。串沟模式是前期洪水漫过河湾内侧洪泛平原,漫滩水流冲刷形成若干串沟,后续洪水沿串沟继续冲刷,串沟逐步横向展宽和向下游侵蚀,直至形成新的河槽。主流顶冲模式是水流顶冲河湾内侧河岸,形成湾状缺口,后续洪水持续顶冲湾状缺口,直至上下游水流贯通,形成斜槽裁弯。  相似文献   

海啸波作用下泥沙运动——Ⅳ.建筑物局部冲刷          下载免费PDF全文

陈杰  蒋昌波  隆院男  邓斌  伍志元  刘静 《水科学进展》2013,24(6):830-835

基于波浪水槽实验,以沿海公路为对象,对海啸波作用下建筑物局部冲刷机理开展研究。实验采用1/10与1/20的组合坡度,选取N波作为入射波。实验对波高、波浪的上爬、回落和水跃过程、每个波作用后的地形进行了测量和记录。实验结果表明,N波作用下地形发生冲淤变化,在回落水流所形成的螺旋流作用下,路基向海侧形成明显的冲刷坑。路基所在位置是最主要因素,波高是次要因素,路基深度影响较小。路基位于滩肩侵蚀发生处,则最大冲刷深度相对较大。  相似文献   

Estimating effective shale area distributions from subsurface data     

《Marine and Petroleum Geology》2014

Estimation of shale bed continuity is needed in reservoir modeling and simulation as these constitute permeability barriers and baffles. However, efforts to characterize continuity of shale beds from 2D outcrop or well log sections lack critical 3D geometry and areal dimensions. A different approach is to estimate shale bed continuity by measuring the “effective shale area”. While it is a more indirect measure of shale bed continuity as it relies upon the sealing capacity of shales in selected, well-documented field examples, it eliminates the problem of the unknown but critical third dimension. Analyses of effective shale area distributions are made within structurally simple fields where hydrocarbon contacts were directly controlled by the sealing shales being measured, and faulting is limited. Datasets are exclusive to siliciclastic reservoirs formed in paleoenvironments ranging from non-marine to shallow water marine.Results show that effective shale areas are separated into two distinct distributions of fully marine versus non-marine/marginal marine origin. Shales deposited in non-marine to marginal marine paleoenvironments display smaller areas where effective sealing capacity is reduced by channel body incision. In fields where hydrocarbon columns are sealed by fully marine shale, larger areas are supported, often but not always, approaching structural spill points. In the case of reservoirs capped by these marine flooding shales, one can logically infer an abrupt decrease in channelization and resulting sizeable increase in continuity of shale bed seals.Similar shale types in traps formed in different structural regimes (e.g. extensional versus contractional domains) show comparable areal distributions, supporting use of data from different locations where the controls on hydrocarbon seal areas are well known. All shales measured here are areally large and would probably be accommodated in reservoir simulation deterministically, but use of the dimensions provided here would clearly be an aid in situations where a limited number of field appraisal wells are available. Discriminating between deterministic shales and stochastic shales, which are several orders of magnitude smaller in size, is also important for reservoir modeling and simulation. Results shown here should also be of great utility as input into discovery appraisal and field development scenario construction.  相似文献   

SCOUR RATE FORMULA     

Zhaoyin WANGProf Dr.  International Research  Training Center on Erosion  Sedimentation. P.O.Box  Beijing  China Jinchi HUANG Dr. Senior Engineer  China Institute of Water Resources  Hydro-Power Research  P.O.Box  Beijing . Chi 《国际泥沙研究》1997,(3)

I.INTRODUCTIONhiverchannelsaresubjecttocontinuouschangeingeometryduetoillteraCtionbetWeentheflowanderodibleboundaries.Ofconcerntothedesignersofoilpipelinesacrossariver,bridgesandhydraulicworksistheproblemofscourwhichcanunderminetheStructures.Scouratsiteofbridgesandhydraulicworksoccursduetoconstrictedflowandexistenceofbridgepiers.SuchatabOfscouroccursonlyinashortsection,usuallyillthesameorderofthelengthofthehydraulicworksorbridges.Therefore,thispatternofscouriscalledlocalscour.Man}rresea…  相似文献   

Analysis of riverbank instability due to toe scour and lateral erosion     

Colin R. Thorne  Steven R. Abt 《地球表面变化过程与地形》1993,18(9):835-843

This paper provides instruction in the use of the computer spreadsheet to undertake the calculations necessary to apply the Osman–Thorne bank stability analysis for steep, eroding riverbanks. The guide explains how to input the necessary parameters into the LOTUS 123 spreadsheet in order to:

• 1 find the initial factor of safety of the bank with respect to slab-type failure;
• 2 test the sensitivity of bank stability to changes in the engineering properties of the bank material;
• 3 analyse the response of bank stability to toe scour and/or lateral erosion and find the critical condition;
• 4 find the geometry of the failure surface and failure block;
• 5 analyse the response of bank stability to further toe scour and/or lateral erosion;
• 6 find the geometry of the failure surface and failure block in subsequent failures.

  相似文献   

长江口深水航道整治一期工程南导提丁坝群头局部冲刷试验研究   总被引：1，自引：1，他引：1  

卢无疆  贾建军等 《海洋工程》2001,19(2):29-33

采用双向稳定水流、清水定床、局部动床的试验方法，用正态模型研究长江口深水航道整治一期工程南导堤丁坝群坝头局部冲刷问题。结果表明，航道开挖和双本坝的存在使得下游流速有所增加，影响程度落潮大于涨潮。坝头局部冲刷主要受落潮流控制，在沿深度为单一砂粉底质情况下，坝头冲刷坑深度分别达到27m和29m；考虑到原状底质下部为极难起动的粘土，实际冲刷坑底界到达粘土层后就不再刷深，此时冲刷坑深度为7．4m和4．7m，冲刷坑的平面范围有所加大。工程设计提出的护坦尺度能较好地保护坝头前沿滩地，适当缩小护坦尺度也能起到保护作用，但冲刷范围明显增大。  相似文献   

Experimental Study on Local Scour Around A Large Circular Cylinder Under Irregular Waves     

周益人  陈国平 《中国海洋工程》2004,18(2):245-256

1 .IntroductionWiththedevelopmentofexploitationofmarineresources ,theconstructionofoffshorestructuresdevelopsrapidly ,suchasmarineoilplatforms ,deep waterbreakwaters ,marinebridges ,largehar bors,etc .Thesestructureswillchangesurroundingwaveandcurrentconditionsandleadtolocalscourofseabed ,resultinginstructuraldamage .Therefore ,localscouraroundmarinestructuresaswellastheirprotectionhasdrawnmuchattentionfromrelativeengineeringfields .Manyscholarshaveconduct edtheoreticalanalysisandexperimentals…  相似文献   

Local Scour Around Piles Under Wave Action   总被引：1，自引：0，他引：1  

陈国平左其华  黄海龙 《中国海洋工程》2004,18(3):403-412

The model tests are performed with regular waves, and the effect of wave height, wave period, water depth, sediment size and pile diameter is evaluated. The shape and size of local scour around piles are studied. There are three typical scour patterns due to wave action. It is found that a relationship exists between the erosion depth and the wave number. An empirical formula of the maximum local scour is thus derived.  相似文献