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1.
Temperature changes are known to induce specific couplings in clay, in particular, an anomalously high thermal pressurization in undrained conditions or a thermal compaction in drained conditions, both of which are potential threats for the mechanical stability and sealing capacity of the geomaterials. Thermodynamical analysis of those peculiar thermomechanical couplings points to a potentially important latent energy, which in turn could limit the temperature change upon heating or cooling. The direct measurement of latent energy developed during a laboratory geomechanical test is challenging. Instead, proper identification of thermal hardening in conventional experiments with temperature changes provides an alternative route to estimate latent energy. In this work, existing laboratory thermomechanical tests of clays are analyzed with a rigorous thermodynamic framework to quantify the magnitude of latent energy in thermomechanically loaded clays. A thermodynamically consistent constitutive model for fully saturated clays that combines two key features, (a) the temperature dependence of the blocked energy and (b) the framework of bounding plasticity, is proposed. The performance of the model is validated by reproducing results obtained in laboratory tests for Boom and Opalinus clays. The thermomechanical loads considered to validate the model performance were then used to estimate the percentage of work that remains latent in the clayey material during plastic yielding. We find that the magnitude of latent energy is quite significant, typically a few tens of percent of the total dissipated energy, and increases significantly with temperature. Accordingly, it is expected to play an important role in the thermomechanical response of clays. 相似文献
2.
青海共和盆地地热资源热源机制与聚热模式 总被引:2,自引:0,他引:2
青海共和盆地东侧贵德扎仓热田是探讨共和盆地地热资源成因的关键地区。本文综合区域地质、岩石热物性、同位素年代学、水文地球化学和地球物理测量等方法,重点分析了共和盆地的构造背景和热源机制,深入研究了共和盆地地热能系统的关键环节。研究发现:①识别出盆地地壳15 km以下深度发育高导体,并可与新生代青藏高原东部中-下地壳发育的层状低速高导层对比;②近NW-NS向的瓦里贡左旋走滑逆冲断裂是扎仓热田重要的控热和导热断裂;③晚中生代花岗岩与上覆围岩具有显著的热导率;④温泉氢氧同位素指示水源以地表水补给为主;⑤存在浅层新生界碎屑岩中-低温热储和深层花岗岩中-高温热储,发育四层两类地热资源。综合分析提出了共和盆地干热岩三元聚热模式:即新生代中-下地壳发育的高温低速高导层是主要热源,中晚三叠世花岗岩是良好的导热和储热体,既是干热岩母岩,也是热储,新生代低热导率沉积岩是良好的盖层。研究对于青藏高原地热成因、资源预测、开发规划等具有参考意义。 相似文献
3.
Guangqiu Jin Wenhai Yang Huiyu Xu Zhongtian Zhang Saiyu Yuan Hongwu Tang Ling Li David Andrew Barry 《水文研究》2020,34(5):1144-1153
Contaminants that entered the streambed during previous surface water pollution events can be released to the stream, causing secondary pollution of the stream and impacting its eco-environmental condition. By means of laboratory experiments and numerical simulations, we investigated density effects on the release of solute from periodic bedforms. The results show that solute release from the upper streambed is driven by bedform-induced convection, and that density effects generally inhibit the solute release from the lower streambed. Density gradients modify the pore water flow patterns and form circulating flows in the area of lower streambed. The formation of circulating flows is affected by density gradients associated with the solute concentration and horizontal pressure gradients induced by stream slope. The circulating flows near the bottom of the streambed enhance mixing of the hyporheic zone and the ambient flow zone. 相似文献
4.
Jeffrey Wade Laura Lautz Christa Kelleher Philippe Vidon Julianne Davis Julio Beltran Casey Pearce 《水文研究》2020,34(26):5340-5353
Beaver dam analogues (BDAs) are a cost-effective stream restoration approach that leverages the recognized environmental benefits of natural beaver dams on channel stability and local hydrology. Although natural beaver dams are known to exert considerable influence on the hydrologic conditions of a stream system by mediating geomorphic processes, nutrient cycling, and groundwater–surface water interactions, the impacts of beaver-derived restoration methods on groundwater–surface water exchange are poorly characterized. To address this deficit, we monitored hyporheic exchange fluxes and streambed porewater biogeochemistry across a sequence of BDAs installed along a central Wyoming stream during the summer of 2019. Streambed fluxes were quantified by heat tracing methods and vertical hydraulic gradients. Biogeochemical activity was evaluated using major ion porewater chemistry and principal component analysis. Vertical fluxes of approximately 1.0 m/day were observed around the BDAs, as was the development of spatially heterogeneous zones of nitrate production, groundwater upwelling, and anaerobic reduction. Strong contrasts in hyporheic zone processes were observed across BDAs of differing sizes. This suggests that structures may function with size-dependent behaviour, only altering groundwater–surface water interactions after a threshold hydraulic step height is exceeded. Patterns of hyporheic exchange and biogeochemical cycling around the studied BDAs resemble those around natural beaver dams, suggesting that BDAs may provide comparable benefits to channel complexity and near-stream function over a 1-year period. 相似文献
5.
6.
Monjit Borthakur Anup Saikia Kiran Sharma 《Singapore journal of tropical geography》2020,41(3):341-366
Changing urban landscape with multistoried high rises, roads and pavements is continuously reducing urban green space. These structures result in high surface temperature variation within cities. To explore the relationship between surface temperature and normalized difference vegetation index (NDVI), this study estimates two models—geographically weighted regression (GWR) and a fixed effect panel data model in relation to the Guwahati Metropolitan Area (GMA), a secondary city in north east India. The results indicate the superiority of GWR regression in presence of spatial dependence. Panel data analysis shows that the densely populated urban areas in the GMA with less than 10 per cent greenery are 1°C warmer than the sub-urban areas with 50 per cent greenery. 相似文献
7.
燕山中部地区地热资源丰富,地热地质条件较好,但该地区大地热流测量工作较少,岩石圈热结构研究尚未开展,制约了该地区的地热地质研究与资源勘探开发。本文以该地区的七家-茅荆坝地热田为典型区,结合地温测井、取样测试、数据收集与分析,初步查明燕山中部大地热流特征及浅部-深部岩层热物性特征,填补了大地热流值测量空白区,在此基础上建立了研究区热结构概念模型,估算其深部地温分布。研究得出燕山中部大地热流值变化较大,平均约57 mW/m~2,与周边温泉水温存在较好的相关关系。其中七家-茅荆坝地热田大地热流值较高,为74.9 mW/m~2。通过深部地温分布计算得出七家—茅荆坝地区居里面埋深为21.5~22.8 km,莫霍面温度约815℃,分析结果与前人研究成果较为一致,验证了本文所建立岩石圈热结构模型的准确性。 相似文献
8.
基于高导热材料填充漏失构造的深井换热器性能分析 总被引:1,自引:0,他引:1
地热供暖可有效缓解北方雾霾天气。干热岩虽然储量丰富,但增强型地热技术由于开发费用较高,裂隙控制以及避免诱发地震的技术尚不成熟,现阶段还不能商业化应用。水热型地热开发技术虽较成熟,但受资源条件的限制,开发规模较小。对于大多地区,受地质构造和资源禀赋的控制,单井产水量较低或者回灌难,开发经济效益较差。深井换热器(DBHE)技术是开采地热水低产区或回灌难地区热能的有效方式,但受制于岩石导热系数低,单井输出功率小,投资回收期长。为提高DBHE的输出功率,本文提出了增强型深井换热器(EDBHE),通过主动将高导热性能的复合填充剂流进漏失构造的方式提高岩石的导热性能,通过调节回压、密度和黏度来控制漏失量。研究结果表明,单井EDBHE十个采暖季的平均取热功率为1002. 34 kW,是DBHE(424. 45 kW)的2. 36倍。而双井EDBHE十个采暖季的平均取热功率更是达到了27501. 61 kW,且热输出稳定,每年的衰减率0. 95%。EDBHE技术有效利用了出水量低或回灌难的水热型热储,大幅提高了其出力,扩大了地热供暖的应用范围。 相似文献
9.
Yinhui Zuo Shu Jiang Shihu Wu Wei Xu Jiong Zhang Renpeng Feng Meihua Yang Yongshui Zhou M. Santosh 《Basin Research》2020,32(6):1328-1346
The Chagan Depression in the Yingen-Ejinaqi Basin, located at the intersection of the Paleo-Asian Ocean and the Tethys Ocean domains is an important region to gain insights on terrestrial heat flow, lithospheric thermal structure and deep geodynamic processes. Here, we compute terrestrial heat flow values in the Chagan Depression using a large set of system steady-state temperature data from four representative wells and rock thermal conductivity. We also estimate the “thermal” lithospheric thickness, mantle heat flow, ratio of mantle heat flow to surface heat flow and Moho temperature to evaluate the regional tectonic framework and deep dynamics. The results show that the heat flow in the Chagan Depression ranges from 66.5 to 69.8 mW/m2, with an average value of 68.3 ± 1.2 mW/m2. The Chagan Depression is characterized by a thin “thermal” lithosphere, high mantle heat flow, and high Moho temperature, corresponding to the lithospheric thermal structure of “cold mantle and hot crust” type. We correlate the formation of the Yingen-Ejinaqi Basin to the Early Cretaceous and Cenozoic subduction of the western Pacific Plate and the Cenozoic multiple extrusions. Our results provide new insights into the thermal structure and dynamics of the lithospheric evolution in central China. 相似文献
10.
湖泊或海湾中的沉积物吸附氮(N)、磷(P)等元素所形成的沉积层成为水体富营养化的內源。在波浪作用下,尤其是强浪作用下,沉积物中的N、P会通过内源释放作用大量进入水体中。本文在自制的U型水槽中开展实验,采用不同水头差来模拟波浪的循环荷载作用,研究了沉积层中的N、P在静置固结状态(Ⅰ)、加波未液化状态(Ⅱ)、加波液化状态(Ⅲ)下的释放规律,并给出该试验条件下的沉积物释放速率的拟合方程。试验结果表明:沉积物中总氮(TN)和溶解性总氮(TDN)的释放速率会随着水动力作用的增强而增加;总磷(TP)、溶解性总磷(TDP)和活性磷酸盐(SRP)的释放速率也随着水动力作用增强而增加,但水体中悬浮物(SS)含量过高会限制其释放速率。 相似文献