Application of the numerical manifold method for stress wave propagation across rock masses     

G. F. Zhao  X. B. Zhao  J. B. Zhu 《国际地质力学数值与分析法杂志》2014,38(1):92-110

In this paper, the numerical manifold method (NMM) is extended to study wave propagation across rock masses. First, improvements to the system equations, contact treatment, and boundary conditions of the NMM are performed, where new system equations are derived based on the Newmark assumption of the space–time relationship, the edge‐to‐edge contact treatment is further developed for the NMM to handle stress wave propagation across discontinuities, and the viscous non‐reflection boundary condition is derived based on the energy minimisation principle. After the modification, numerical comparisons between the original and improved NMM are presented. The results show that the original system equations result in artificial numerical damping, which can be overcome by the Newmark system equations. Meanwhile, the original contact scheme suffers some calculation problems when modelling stress wave propagation across a discontinuity, which can be solved by the proposed edge‐to‐edge contact scheme. Subsequently, the influence of the mesh size and time step on the improved NMM for stress wave propagation is studied. Finally, 2D wave propagation is modelled, and the model's results are in good agreement with the analytical solution. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

考虑洞室岩体应力型破坏特征的局部地应力反演方法及应用     

裴书锋  赵金帅  于怀昌  刘国锋  夏跃林  张頔  徐进鹏 《岩土力学》2020,41(12):4093-4104

介绍了一种考虑地下洞室片帮、钻孔剥落等岩体应力型破坏特征为信息源，通过数值模拟智能反演方法预测高应力大型地下洞室群围岩局部应力场的新思路。该方法将地下洞室群片帮、钻孔剥落等应力型破坏的位置、深度或者宽度进行定量描述，以弹性模型计算获得的常偏应力大于岩体启裂强度的范围来表示应力型破坏范围，通过分析实测地应力数据约束部分地应力数量，然后采用智能数值反演方法得到其他的地应力分量。采用该方法预测了白鹤滩水电站右岸地下厂房0+76断面附近围岩地应力场，反演获得最大主应力在34 MPa左右。通过其他部位岩体破裂的数值模拟和观测结果对比，验证了地应力场预测的合理性。  相似文献   

Reply to comments on “Explicit versus implicit front advancing schemes for the simulation of hydraulic fracture growth” (Int. J. Numer. Anal. Methods Geomech., 2019, 43 (6), 1300–1315)” by Prof. Linkov     

Haseeb Zia  Brice Lecampion 《国际地质力学数值与分析法杂志》2020,44(18):2524-2526

We reply to Prof. Linkov comments on our article entitled “Explicit versus implicit front advancing schemes for the simulation of hydraulic fracture growth” (Int. J. Numer. Anal. Methods Geomech., 2019, 43 (6), 1300–1315). We present additional results indicating that both the implicit and explicit front advancement schemes are robust even in the case of a large stress contrast.  相似文献   

铁路路基粗粒土填料临界动应力试验研究     

王康宇  庄妍  耿雪玉 《岩土力学》2020,41(6):1865-1873

粗粒土填料被广泛应用于铁路基床填料中，直接承受轨道结构传递的列车动循环荷载的长期作用，研究其在列车动荷载作用下的动力行为特征及塑性变形特性可为路基状态评估、沉降控制提供思路。采用GDS动三轴试验系统对铁路基床表层的粗粒土填料动力响应开展研究，通过引入塑性应变率和安定理论，将不同频率、围压、循环动应力比等条件下路基填料的轴向塑性应变的发展规律划分为塑性安定、塑性蠕变和增量塑性破坏3种类型，并确定了塑性安定和塑性蠕变状态的临界动应力水平。研究表明：粗粒土填料的临界循环应力比随着围压的增大而增大，随着荷载频率的增加而减小。通过对试验结果的拟合分析，提出了以围压为变量的临界动应力经验公式，为合理评估列车荷载作用下路基任意深度的动力稳定提供了理论依据。  相似文献   

超高沥青混凝土心墙高应力水平的降低措施研究     

高俊  党发宁  马宗源 《岩土力学》2020,41(5):1730-1739

随着沥青混凝土心墙堆石坝的快速发展，超高沥青混凝土心墙堆石坝建设迎来了前所未有的机遇，但随着坝高的增加，心墙的安全挑战也变得异常突出。基于应力水平的定义，提出降低超高沥青混凝土心墙高应力水平的措施，依托心墙应力水平的敏感性研究，推算了独立满足和综合满足心墙屈服剪切破坏控制标准的心墙材料强度参数（最敏感材料参数）取值范围。研究表明，心墙应力水平随坝高和河谷岸坡坡比的增加而显著增大；心墙破坏比 、黏聚力 和内摩擦角 属于高敏感性参数；增大心墙破坏比 、黏聚力 和内摩擦角 能够显著地降低心墙应力水平；推荐适宜建设超高沥青混凝土心墙堆石坝的心墙破坏比 、黏聚力 和内摩擦角 取值范围： 0.8、 0.4 MPa和 31.5°（坝高 200 m），且随坝高的增长梯度按5%/25 m、15%/25 m和5%/25 m进行调整。  相似文献   

塔河油田奥陶系储层构造应力场研究     

刘佳庚  李静  苏玉亮  范作松  刘旭亮  郭豪 《地质力学学报》2020,26(1):48-54

油气储层构造应力场的分布特征，对油气运移、注采井网布置、储层改造等具有重要意义。为此，文章从塔河油田AD13井区的地质构造演化入手，基于油田测井资料，结合弹性力学及有限元理论，建立研究区地应力弹性力学计算模型，利用有限元软件对研究区储层地应力进行模拟研究，并将模拟结果与现场地应力实测值进行对比分析。结果表明，研究区最大水平主应力为102~130 MPa，最小水平主应力为87~110 MPa，均为压应力；研究区东部及南部最大水平主应力方向为北东向，西北部最大水平主应力方向为北东东向，西南部最大水平主应力方向为南东向，地应力大小及方向均与实际结果相符。研究结果可为研究区油气勘探开发工程提供科学依据。   相似文献   

三疣梭子蟹几丁质酶基因(PtCht6)的克隆及其在免疫中的功能分析     

宋柳  吕建建  王磊  孙东方  刘萍 《海洋与湖沼》2019,50(5):1080-1090

几丁质酶(chitinase)在甲壳动物的蜕皮、消化和免疫等很多生物学过程中发挥重要功能,为深入探讨几丁质酶的免疫防御机制,本实验利用RACE技术克隆了三疣梭子蟹(Portunus trituberculatus)PtCht6基因。该基因cDNA全长2736bp,开放阅读框(ORF)2103bp,编码700个氨基酸,具有几丁质酶GH18家族典型特征。利用实时荧光定量技术分析PtCht6在三疣梭子蟹不同组织、不同蜕皮阶段、不同病原感染以及低盐胁迫(11)下的表达特征,结果显示:PtCht6在各组织中均有表达且在肝胰腺中的表达量最高;在不同蜕皮时期的肝胰腺中,其表达量由蜕皮后期(A/B)、蜕皮间期(C)、蜕皮前期(D)依次递减(P0.05);人工感染WSSV和副溶血弧菌后.PtCht6的表达量在肝胰腺中分别于12h、72h达到最大值,在血细胞中均于12h达到最大值,且相较于对照组,整体显著上调表达(P0.05);低盐胁迫能够显著抑制该基因的表达,最高抑制73倍(P0.05)。同时发现,低盐环境下感染WSSV后,该基因达到峰值的时间明显延迟(至少延迟12h.P0.05)。该研究结果预示PtCht6作为免疫因子参与三疣梭子蟹的病原防御,且低盐胁迫在一定程度上抑制了该基因的免疫功能。  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   

Inference of in situ stress from thermoporoelastic borehole breakouts based on artificial neural network     

Hua Zhang  Shunde Yin 《国际地质力学数值与分析法杂志》2019,43(16):2493-2511

The determination of in situ stresses is very important in petroleum engineering. Hydraulic fracturing is a widely accepted technique for the determination of in situ stresses nowadays. Unfortunately, the hydraulic fracturing test is time-consuming and expensive. Taking advantage of the shape of borehole breakouts measured from widely available caliper and image logs to determine in situ stress in petroleum engineering is highly attractive. By finite element modeling of borehole breakouts considering thermoporoelasticity, the authors simulate the process of borehole breakouts in terms of initiation, development, and stabilization under Mogi-Coulomb criterion and end up with the shape of borehole breakouts. Artificial neural network provides such a tool to establish the relationship between in situ stress and shape of borehole breakouts, which can be used to determine in situ stress based on different shape of borehole breakouts by inverse analysis. In this paper, two steps are taken to determine in situ stress by inverse analysis. First, sets of finite element modeling provide sets of data on in situ stress and borehole breakout measures considering the influence of drilling fluid temperature and pore pressure, which will be used to train an artificial neural network that can eventually represent the relationship between the in situ stress and borehole breakout measures. Second, for a given measure of borehole breakouts in a certain drilling fluid temperature, the trained artificial neural network will be used to predict the corresponding in situ stress. Results of numerical experiments show that the inverse analysis based on finite element modeling of borehole breakouts and artificial neural network is a promising method to determine in situ stress.  相似文献   

Current-induced scour beneath initially elevated subsea pipelines     

《Applied Ocean Research》2019

When a subsea pipeline is laid on an uneven seabed, certain sections may have an initial elevation with respect to the far-field seabed, e_o, and thus potentially affecting the on-bottom stability of the pipeline. This paper focuses on quantifying the effects of the upstream dimensionless seabed shear stress, θ_∞, and Reynolds number, Re, on: (1) the maximum dimensionless seabed shear stress beneath the pipe, θ_max, to be compared to the critical shear stress in order to determine whether scour would occur and progress towards an equilibrium state; and, (2) the dimensionless equilibrium scour depth beneath the pipe, S_eq/D. Using a 2-D Reynolds averaged Navier-Stokes (RANS) approach along with the k-ω Shear Stress Transport (SST) turbulence model, a parametric study involving 243 computational fluid dynamics (CFD) simulations was conducted. The simulation results were used to develop a closed-form equation for the prediction of θ_max. Subsequently, experimental measurements of S_eq/D have been compiled from published literature, to develop a new closed-form equation for the prediction of S_eq/D with a high correlation to the experimental data. In summary, we present two closed-form equations for the prediction of θ_max and S_eq/D for pipelines with an initial e_o/D, which are applicable for both clear-water and live-bed conditions. The effects of θ_∞ and Re have been included, albeit Re having a small influence as compared to the other parameters.  相似文献