室内水平电渗排水试验研究     

王宁伟  韩旭  张雷 《岩土工程技术》2014,28(5)

根据多次室内试验,大致掌握了不同电势梯度下非饱和黏性土的水平电渗排水规律,从电渗排水量、排水速率、土体电阻、能量消耗、电渗透系数、耗能系数等方面对电渗进行曲线分析,通过分析大致判断电渗排水的终止条件,可以对未来电渗法的实际操作给出一定的理论依据.试验结果表明:随着通电时间的增加,土体的电阻增大,其电流减小,导致电渗排水的速率降低,出于节能的考虑,可以在电渗末期停止通电,这样做既节能又有利于电渗排水的效果.  相似文献   

桩侧注浆抗拔桩离心模型试验与原位测试分析     

钱建固  马霄  李伟伟 《岩土力学》2014,35(5):1241-1246

通过离心机模型试验研究了注浆对接触面特性、抗拔桩荷载-位移曲线及桩侧摩阻力的影响,揭示了注浆提高桩身侧摩阻力发展规律和抗拔承载机制,并进一步将离心机模型试验的结果与原位试验结果进行了对比分析。研究表明,注浆桩侧摩阻力的发挥呈现一个渐进过程,桩身上部极限摩阻力率先发挥,并逐渐向中下部发展;注浆后桩侧极限桩侧摩阻力得到提高,而发挥极限状态所需的桩-土相对位移减小,上拔加载过程中,桩侧上部和下部极限摩阻力增幅较大,中部增幅较小。离心与现场试验一致表明,桩侧注浆显著提高了桩的抗拔刚度及极限承载能力。  相似文献   

时间域瞬变电磁在玄武岩盖层区煤田勘探中的应用     

李霄龙  崔迎龙  杨威  何清立 《吉林地质》2014,(4)

玄武岩盖层下固体矿产的勘探工作,一直没有取得良好的效果,通过普通物探手段难以穿透由玄武岩盖层所引起的高阻层,随着物探技术方法的不断革新,时间域瞬变电磁法(TDEM)可以有效的穿透中厚、巨厚玄武岩高阻层,且对盖层下隐伏矿体的地质情况,有较清晰的揭露,达到了良好的效果。  相似文献   

伊拉克艾哈代布油田AD205H井钻井液技术          下载免费PDF全文

孙莉  杨桂林  孙义春 《探矿工程》2014,41(8):33-35，39

AD205H井是伊拉克艾哈代布油田的首口简化三开水平井,上部水敏泥岩易分散造浆、缩径,中部存在高压盐水层、燧石结核地层,储层灰岩含量高,从而增加了施工周期,制约了该区水平井发展步伐。针对上述钻井难点,开展了钻井液抑制性、抗温性、抗盐性、抗污染评价试验,研制了混油聚磺钻井液体系。现场应用表明,聚磺钻井液体系抗污染能力强,施工过程中性能稳定。对于上部水敏性泥浆有很强的抑制作用,对于下部易渗漏的灰岩地层有很好的封堵作用,减少了井下复杂事故的出现。此井为该地区简化井身结构第一口井,低密度优质钻井液保证了该井的顺利施工,创造了该油田钻井施工的多项纪录。  相似文献   

基于泥沙流变特性的吸力式沉箱减阻技术     

钟丹  张民曦  俞梅欣  李小军  喻国良 《海洋工程》2022,40(6):31-40

针对吸力式沉箱在黏性底床中沉贯安装的减阻问题,基于黏性泥沙的流变特性,开展了一系列不同振动荷载作用下的室内沉贯模型试验,分析了振动荷载对吸力式沉箱沉贯过程的影响和沉贯减阻效果。试验结果表明：在压力沉贯阶段或吸力沉贯阶段施加高频振动荷载,均能促使吸力式沉箱侧壁周围的土体发生流化,有效降低沉箱的沉贯阻力;减阻效果与振动频率和沉箱的长径比有关,与振动频率成正比,与沉箱的长径比成反比;存在一个临界频率,当振动频率大于该频率后,沉贯阻力随频率的减小不明显;施加高频振动荷载有助于减小吸力沉贯阶段沉箱内的土塞高度,促进沉箱沉贯到位。研究成果可为黏性泥沙流变减阻技术在吸力式沉箱中的应用提供理论依据和技术参考。  相似文献   

网毯式油气成藏体系仓储层运移机理研究   总被引：2，自引：0，他引：2  

张善文  王永诗  姜素华  王志英 《中国海洋大学学报(自然科学版)》2009,39(3)

研究网毯式油气成藏体系仓储层运移油的机理,揭示断层幕式排烃期仓储层运移油的机理,以油气二次运移理论为指导,开展了油沿断裂纵向运移及油在仓储层内横向运移的定量研究.首先根据地质模型,建立断层内油压力衰减梯度的数学模型,根据能量守恒原理,推导出油沿断层纵向运移的压力梯度公式,计算出油沿断裂进入仓储层的初始压力,再根据仓储层的地质模型,建立油在仓储层内横向运移的压力衰减模型及上网层开启时的泄压模型,推导出油沿仓储层横向运移的压力梯度公式及泄压公式,最终得出仓储层运移油的合力公式.并指出当运移动力大于运移阻力,即运移合力为正时,仓储层以运移油为主,当运移动力等于或小于运移阻力,即运移合力为负时,仓储层以临时仓储(成毯)、成藏为主.通过对运移合力的计算,可以判断油在仓储层内运移、成毯和成藏的状态,预测仓储层运移、成毯或成藏的范围,从而指导该体系隐蔽油气藏的勘探.  相似文献   

Estimates of flow resistance and eddy viscosity coefficients for 2D modelling on vegetated floodplains     

C. A. Vionnet  P. A. Tassi  J. P. Martín Vide 《水文研究》2004,18(15):2907-2926

The problem of quantifying the effects of flexible plants on flow resistance and eddy viscosity by vegetated floodplains is first addressed with a one‐dimensional (1D) approximation based upon the so‐called lateral distribution method. The estimates so obtained are then tested with two‐dimensional (2D) numerical simulations based on the full shallow water equations through the use of the computational code Telemac‐2D. Data obtained on a physical model of the Besòs River (Spain), whose floodplains were covered with plastic ornamental plants to mimic the effect of flexible vegetation, is used for the validation of the numerical results. Additionally, the values of flow resistance estimated numerically with the 1D and 2D simulations are compared with values obtained in a rectangular flume under flow conditions (slope, water depth and artificial lining) similar to those used on the reduced model. It is then established that as more physical mechanisms are included in the mathematical model used to study the problem, the ratio between the floodplain and the main channel flow resistance coefficient increases. The approach demonstrates that whenever enough flow data is available, the lateral distribution method delivers values of flow resistance and eddy viscosity which are highly consistent with 2D numerical modelling. This finding could mean considerable savings in the burdensome task of specifying flow resistance and turbulence dissipation values for 2D modelling of large compound channel systems. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Testing a theoretical resistance law for overland flow on a stony hillslope     

Alessio Nicosia  Costanza Di Stefano  Vincenzo Pampalone  Vincenzo Palmeri  Vito Ferro  Mark A. Nearing 《水文研究》2020,34(9):2048-2056

Overland flow, sediments, and nutrients transported in runoff are important processes involved in soil erosion and water pollution. Modelling transport of sediments and chemicals requires accurate estimates of hydraulic resistance, which is one of the key variables characterizing runoff water depth and velocity. In this paper, a new theoretical power–velocity profile, originally deduced neglecting the impact effect of rainfall, was initially modified for taking into account the effect of rainfall intensity. Then a theoretical flow resistance law was obtained by integration of the new flow velocity distribution. This flow resistance law was tested using field measurements by Nearing for the condition of overland flow under simulated rainfall. Measurements of the Darcy–Weisbach friction factor, corresponding to flow Reynolds number ranging from 48 to 194, were obtained for simulated rainfall with two different rainfall intensity values (59 and 178 mm hr⁻¹). The database, including measurements of flow velocity, water depth, cross-sectional area, wetted perimeter, and bed slope, allowed for calibration of the relationship between the velocity profile parameter Γ, the slope steepness s, and the flow Froude number F, taking also into account the influence of rainfall intensity i. Results yielded the following conclusions: (a) The proposed theoretical flow resistance equation accurately estimated the Darcy–Weisbach friction factor for overland flow under simulated rainfall, (b) the flow resistance increased with rainfall intensity for laminar overland flow, and (c) the mean flow velocity was quasi-independent of the slope gradient.  相似文献   

基于广义接触模型的离散元方法及其对船体冰载荷的分析   总被引：1，自引：1，他引：0  

孔帅  季顺迎 《海洋工程》2020,38(3):102-112

冰载荷是影响船舶结构安全的主要环境载荷,因而确定破冰船的冰载荷特征可用于船体结构设计及船舶安全预警分析。海冰作为典型的脆性材料,可采用单元间具有黏结失效效应的离散元方法模拟其破碎行为。为有效地模拟海冰破碎的渐进过程,采用由局部黏结点组成黏结单元的广义接触模型。为分析该模型中直接决定黏结单元失效的强度参数的影响,采用海冰单轴压缩和三点弯曲试验数值模拟进行分析。通过模型试验确定了失效模型中法向黏结强度、切向黏结强度和Mohr-Coulomb准则中的接触摩擦系数的影响。将该数值模型应用于极地科学考察船"雪龙号"的平整冰区冰载荷分析中,并与船舶整体冰阻力经验公式进行了对比验证。  相似文献   

钢筋混凝土预制拼装柱扭转力学性能数值模拟与参数分析     

刘洪涛  孔鹏超  王作虎  廖维张 《震灾防御技术》2022,17(2):372-380

采用ABAQUS大型有限元分析软件开展预制拼装柱扭转力学性能数值模拟及参数分析,研究了轴压比、灌浆套筒位置及长度、预制构件拼接缝界面黏结强度对灌浆套筒连接中柱抗扭性能的影响。研究结果表明:轴压比会显著影响预制拼装柱抗扭承载力和变形,而灌浆套筒位置和长度对预制拼装柱抗扭力学性能的影响不明显;预制构件拼接缝界面黏结强度显著影响预制拼装柱抗扭性能。基于预制拼装构件和现浇构件力学性能的对比分析,提出了轴向荷载和扭矩共同作用下灌浆套筒连接预制拼装柱抗扭承载力设计方法。  相似文献