一种横观各向同性岩体蠕变模型     

李列列  管俊峰  肖明砾  刘海朝  唐克东 《岩土力学》2020,41(9):2922-2930

层状岩体由于层理面或者结构面的存在，在力学上具有横观各向同性的特点，现有的各向同性蠕变模型难以全面反映横观各向同性岩体的蠕变力学特性。为构建能够反映横观各向同性岩体的三维蠕变模型，以能反映瞬时应变、减速蠕变和稳态蠕变特征的黏弹性Burgers模型为基础，基于常泊松比假定，在三维各向同性蠕变本构方程的基础上，按照算子替换的方法，将横观各向同性柔度矩阵代替各向同性柔度矩阵，并考虑了平行和垂直层理方向岩体蠕变力学行为的差异性，推导了横观各向同性岩体的三维蠕变本构方程。根据本构方程的特点，提出了根据平行和垂直方向岩体蠕变试验结果进行三维蠕变本构模型中蠕变参数的辨识方法。将提出的模型应用于三轴蠕变试验参数辨识，从而获得了一套完整的三维蠕变参数，并与试验结果进行对比分析，从而验证了所提模型与方法的合理性和有效性。进一步，指出了传统蠕变试验设计方案的局限性，给出了横观各向同性材料蠕变试验设计建议。研究成果为研究岩体三维蠕变机制提供了新思路，可对岩体蠕变试验设计提供相应的科研支撑。  相似文献   

A comparative study of energy performance of hydrostatic seafloor sediment samplers and a new high-efficiency sampler     

《Applied Ocean Research》2019

The hydrostatic energy of high-pressure seawater is a renewable and green energy source for ocean exploration and have been used to replace underwater electrical energy transmission through the cable and underwater battery pack to power seafloor equipment. The advantage of the energy supply method is the cost-effective and the robustness. In the paper, the energy performance of the existing hydrostatic seafloor sediment samplers powered by seawater hydrostatic energy are modelled and analyzed and compared. In view of the common shortcoming of existing technology, a novel hydrostatic seafloor sediment sampler is proposed. The model of energy conversion of the new sampler is built, and its energy performance is obtained. The analysis results indicate that the energy conversion efficiency of the novel sediment sampler is much higher than the existing ones, which means that the new sampler can collect much longer sample with the limited amount of hydrostatic energy. The seawater hydrostatic energy conversion system of the new sampler can also be used to power other seafloor equipment.  相似文献   

Study of the flood control scheduling scheme for the Three Gorges Reservoir in a catastrophic flood          下载免费PDF全文

Shanghong Zhang  Zhu Jing  Wenda Li  Yujun Yi  Yong Zhao 《水文研究》2018,32(11):1625-1634

The Three Gorges Project is the world's largest water conservancy project. According to the design standards for the 1,000‐year flood, flood diversion areas in the Jingjiang reach of the Yangtze River must be utilized to ensure the safety of the Jingjiang area and the city of Wuhan. However, once these areas are used, the economic and life loss in these areas may be very great. Therefore, it is vital to reduce this loss by developing a scheme that reduces the use of the flood diversion areas through flood regulation by the Three Gorges Reservoir (TGR), under the premise of ensuring the safety of the Three Gorges Dam. For a 1,000‐year flood on the basis of a highly destructive flood in 1954, this paper evaluates scheduling schemes in which flood diversion areas are or are not used. The schemes are simulated based on 2.5‐m resolution reservoir topography and an optimized model of dynamic capacity flood regulation. The simulation results show the following. (a) In accord with the normal flood‐control regulation discharge, the maximum water level above the dam should be not more than 175 m, which ensures the safety of the dam and reservoir area. However, it is necessary to utilize the flood diversion areas within the Jingjiang area, and flood discharge can reach 2.81 billion m³. (b) In the case of relying on the TGR to impound floodwaters independently rather than using the flood diversion areas, the maximum water level above the dam reaches 177.35 m, which is less than the flood check level of 180.4 m to ensure the safety of the Three Gorges Dam. The average increase of the TGR water level in the Chongqing area is not more than 0.11 m, which indicates no significant effect on the upstream reservoir area. Comparing the various scheduling schemes, when the flood diversion areas are not used, it is believed that the TGR can execute safe flood control for a 1,000‐year flood, thereby greatly reducing flood damage.  相似文献   

Temporal variation of modulated-wave-train geometries and their influence on vertical bending moments of a container ship     

《Applied Ocean Research》2019

A towing experiment was conducted using a modulated wave train to investigate the vertical bending responses of a hydro-structural container ship model. In the experiment, a spatially periodic modulated wave train, as a model of a freak wave in successive high waves mimicking the so-called three sisters, was generated by the recently established higher-order spectral method wave generation (HOSM-WG) method. HOSM-WG enables us to control the location and timing of the maximum crest height in a wave tank. With precise control of the towing carriage, an experiment was conducted in which the timing of the encounters between the ship model and the modulated wave train was accurately determined. The maximum sagging moment (SM) was found to increase in proportion with the encounter wave height. However, because of differences in the relative depth of the fore and aft troughs, the maximum SM is highly variable for a given wave height. The temporal wave-geometry evolution caused the relative trough-depth to vary significantly within a wave period in the vicinity of the maximum crest height. As a result, depending on the encounter timing, the SM varied considerably for a given wave height. The temporal variation of the wave geometry is a robust feature of a modulated wave train and is common between the spatially periodic and temporally periodic modulated wave trains.  相似文献   

近岸海域大型水母来源与迁移路径分析——以红沿河电厂海域为例     

孙雪  魏皓  张海彦  王彦涛  张广跃  刘汉霖 《海洋与湖沼》2019,50(6):1281-1291

近岸海域水母暴发可导致滨海火/核电厂取水口堵塞,对电厂安全运行造成潜在威胁。寻找水母源地及其迁移路径是水母治理的基础。本文基于拉格朗日质点追踪方法(LTRANS)建立反向追踪模型,并结合水母生态学特性对2015年6—9月聚集在红沿河电厂海域的大型水母进行溯源,获得水母源地及迁移路径,可以为螅状体栖息地寻找和水母拦截打捞提供依据,对近岸海域水母灾害防治具有重要指导意义。溯源结果表明:(1)红沿河电厂及其邻近海域的水母可能来自多个不同源区,辽东湾西部、北部及电厂南北两侧等海域的水母均有可能迁移至电厂附近;(2)受水温和环流影响,6—9月期间到达电厂附近的水母主要源区及迁移路径不同,早期出现在电厂海域的水母很可能是局地产生的,而7—9月持续的高风险水母灾害则主要取决于渤海不同源区水母的物理聚集;(3)根据水母的主要迁移路径,建议在电厂取水口约15km的海域设置一条封闭监测断面,对水母进行实时监测;在距离取水口约30km的外侧海域设置一条调查断面,于7月初至8月中旬,每5天进行一次定点拖网调查。此外,在距离电厂取水口15—20km的西南方向上,对水母进行拦截打捞可大大降低水母入侵风险。  相似文献   

基于水热耦合的青藏高原分布式水文模型——Ⅱ.考虑冰川和冻土的尼洋河流域水循环过程模拟          下载免费PDF全文

刘扬李  周祖昊  刘佳嘉  王鹏翔  李玉庆  朱熠明  姜欣彤  王康  王富强 《水科学进展》2021,32(2):201-210

尼洋河流域是雅鲁藏布江第四大支流,受冰川、积雪和冻土影响,水循环关系极其复杂。为深入研究该区域内的水文循环过程,本文在寒区水循环模型（WEP-COR）的基础上,针对青藏高原气候和地质特点,构建了耦合“积雪-土壤-砂砾石层”连续体和“积雪-冰川”水热过程模拟的青藏高原分布式水循环模型（WEP-QTP）。在尼洋河流域通过对2013—2016年的流量过程模拟发现,工布江达和泥曲站的逐月流量Nash-Sutcliffe效率系数分别达到0.810和0.752,比改进前的0.430和0.095有明显提升;以2015年为例,对比WEP-COR和WEP-QTP模型发现,WEP-QTP模型在汛期特别是主汛前（冻土融化期）模拟的流量过程不会出现较大的波动,模拟得到的逐日流量Nash-Sutcliffe效率系数相比WEP-COR从-0.67提高到0.54。模型增强了地下水含水层的调节作用,使得流量过程更加平稳且接近实测,研究结果表明,WEP-QTP模型适用于青藏高原的水文模拟。  相似文献   

Importance of intracellular Fe pools on growth of marine diatoms by using unialgal cultures and on the Oyashio region phytoplankton community during spring     

Koji Sugie  Kenshi Kuma  Satoshi Fujita  Satomi Ushizaka  Koji Suzuki  Tsutomu Ikeda 《Journal of Oceanography》2011,67(2):183-196

We report on the ability for luxury Fe uptake and the potential for growth utilizing intracellular Fe pools for 4 coastal centric diatom isolates and in situ phytoplankton assemblages, mainly composed of diatoms. Iron uptake of the diatom isolates and natural phytoplankton assemblages in the Oyashio region during spring blooms were prevented by adding hydroxamate siderophore desferrioxamine B (DFB). After the addition of DFB, intracellular Fe in the diatom isolates supported 2.4–4.2 cell divisions with 1.2–2.6 Chl a doublings. The intracellular Fe was primarily used for cell generation rather than Chl a production, leading to a reduction in the Chl a cell quota in the Fe-starved cells with time. The metabolic properties of the Fe-starved cells with their cell morphologies were different among species or genera. An on-deck incubation experiment also exhibited 1.9 cell divisions and 0.81 Chl a doublings of phytoplankton after the addition of DFB, also indicating the preference of cell generation over Chl a production. A decrease in the level of cellular Chl a, a main light-harvesting pigment in Fe-starved diatoms, may become a superior survival strategy to protect the cells from high irradiance that can cause photo-oxidative damages through photosynthesis. Such relatively low-Fe with high-light conditions could often occur in surface waters of the Oyashio region from spring to summer.  相似文献   

圆形煤场中桩-网复合地基原体试验研究     

戴洪军  刘欣良  任治军  韦华 《岩土力学》2011,32(2):487-494

在大型圆形煤场中采用桩-网复合地基是火电厂地基方案设计的新思路,该方案不仅要考虑地基土层的强度满足上部荷载的要求,还需要考虑堆载区内土体的变形对环基的影响。通过对圆形煤场中桩-网复合地基原体试验研究,介绍了在大面积堆载下如何进行桩、土及垫层中应力与应变的测试,设计了2套堆载与测试方案,在试验1区铺设了2层土工格栅,而在试验2区未铺设土工格栅。根据在2个试验区所获得的测试成果,研究了大面积堆载对堆载区内外土体变形的影响深度与范围,对比分析了不同高程处垫层与土体的竖向及侧向应力随深度的变化规律,结合堆载区中桩与边桩的桩身轴力变化,计算出上部桩侧土体对桩所产生的负摩阻力,并依据承台顶面附近测得的垫层与土层的应力,计算出桩土分担荷载的比例,以及桩土应力比的大小与变化规律。在此基础上得到土工格栅对大面积堆载区内外土体应变与应力的影响程度,从而可以为大型圆形煤场桩-网复合地基方案的设计与施工提供客观的技术参数与建议。  相似文献   

结构-地基体系水平与扭转位移耦合效应研究     

姜南  赵慧芳 《地震工程与工程振动》2011,31(5):142-148

采用动力理论对地基-结构非线性相互作用体系的振动方程进行了定性分析.基于多线性随动强化模型,采用非线性有限元法求解了基础和地基土之间的水平刚度与摇摆刚度,建立了结构-地基非线性相互作用体系的力学模型.利用拉格朗日能量法推导了结构水平位移和扭转相耦合的振动方程.采用多尺度法研究了结构-地基相互作用体系的主共振.通过分析不...  相似文献   

Characteristics of the semidiurnal tide in the MLT over Maui (20.75°N, 156.43°W) with meteor radar observations     

A. Guharay  S.J. Franke 《Journal of Atmospheric and Solar》2011,73(5-6):678-685

Semidiurnal tidal features have been examined in the Mesosphere and Lower Thermosphere (MLT) from the long-term (2002–2007) meteor wind data over Maui (20.75°N, 156.43°W). Amplitude and phase obtained from the harmonic analysis exhibit large day to day variability. Mean amplitude obtained from the monthly mean data over the observation period is found to vary within ～8–28 m/s and 10–32 m/s for the zonal and meridional winds, respectively. The amplitude has revealed clear semiannual oscillation (SAO) pattern with maxima during solstices and altitudinal growth in both wind components. Significant resemblance in its variability with other observations carried out from the low latitude sites all over the globe is obtained. Vertical wavelength estimated from the phase gradients exposes large values (>90 km) in all seasons. Contribution of the semidiurnal tide to the total tidal variability in the MLT is found to vary over wide range throughout the year with generally higher influence during winter season over diurnal and terdiurnal components.  相似文献