风电场风资源测量与计算的精度控制

根据多个复杂地形风电场观测操作实践和大量观测数据的计算分析,提出了对观测数据和计算质量精度控制的主要措施,包括:复杂地形测风站布设的5个原则,仪器的合理选型和设置;对由于测风仪固有的系统误差和缺测数据的插补订正可能引起的计算误差进行了定量估算,通过对大量实测数据的对比计算显示:①目前普遍采用的进口风速计的相对偏差在1.6%～5.25%之间,由此可导致轮毂高度附近的年平均风功率密度误差在5%以上,最大达13.8%;②在季风气候区、复杂地形和风的年变率较大的地区,进行缺测数据插补订正时,应选取同季或同一主导风向的数据作为插补订正的基础数据,否则可能导致其平均风功率密度相对误差达20%～50%.     

黄河源区草地退化对局地气候环境影响的数值模拟

土地覆盖变化会影响到近地层各气象要素发生不同程度的变化.利用中尺度数值模式MM5,设计了一个控制试验和一个敏感性试验.通过对2003年7月一个月的积分,模拟了黄河源区草原退化对局地气候环境的影响.结果表明,黄河源区草原退化导致该地区2 m高度气温及地表温度明显升高;空气湿度及土壤湿度不同程度减小;草原退化后降水的减小影响到径流减小;草原退化后还引起退化区感热通量增加,潜热通量减小,有效通量(感热通量+潜热通量)减小.与草地农牧化相比,草原退化对气候环境的影响程度更强.     

Numerical inversion of deformation caused by pressure sources: application to Mount Etna (Italy)

The interpretation of geodetic data in volcanic areas is usually based on analytical deformation models. Although numerical finite element (FE) modelling allows realistic features such as topography and crustal heterogeneities to be included, the technique is not computationally convenient for solving inverse problems using classical methods. In this paper, we develop a general tool to perform inversions of geodetic data by means of 3-D FE models. The forward model is a library of numerical displacement solutions, where each entry of the library is the surface displacement due to a single stress component applied to an element of the grid. The final solution is a weighted combination of the six stress components applied to a single element-source. The pre-computed forward models are implemented in a global search algorithm, followed by an appraisal of the sampled solutions. After providing extended testing, we apply the method to model the 1993–1997 inflation phase at Mt Etna, documented by GPS and EDM measurements. We consider four different forward libraries, computed in models characterized by homogeneous/heterogeneous medium and flat/topographic free surface. Our results suggest that the elastic heterogeneities of the medium can significantly alter the position of the inferred source, while the topography has minor effect.     

河南省地热资源开发利用现状及展望

河南省地热资源丰富,在开封、周口、舞阳、济源、南阳盆地以及濮阳凹陷、汤阴地堑有望找到很好的热储层。现已开发的热储层为埋深８００～１３００ｍ的第三系中细砂层,水温４０～５０℃,水质优良。如果加深钻井深度至２０００ｍ,则有望找到７０℃以上的高温地热水,届时省内地热资源开发利用将上一个新台阶,达到供热采暖水平。文中对河南省地热资源的开发利用现状作一简要介绍,并对如何提高开发利用水平和资源保护提出建议。     

Numerical simulations of the influence of the seasonal snow cover on the occurrence of permafrost at high latitudes

It has repeatedly been reported that snow cover is a dominating factor in determining the presence or absence of permafrost in the discontinuous and sporadic permafrost regions. The temperature at the snow-soil interface by the end of winter, known as the bottom temperature of winter snow (BTS) method, has been used to detect the existence of permafrost in European alpine regions when the maximum snow depth is about 1.0 m or greater. A critical snow thickness of about 50 cm or greater can prevent the development of permafrost in eastern Hudson Bay, Canada. The objective of this study is to investigate the impact of snow cover on the presence or absence of permafrost in cold regions through numerical simulations. A one-dimensional heat transfer model with phase change and a snow cover regime is used to simulate energy exchange between deep soils and the atmosphere. The model has been validated against the in situ data in the Arctic. The simulation results indicate that both snow depth and the onset date of snow cover establishment are important parameters in relation to the presence or absence of permafrost. Early establishment of snow cover can make permafrost disappear, even with a relatively thin snow cover. Permafrost may survive when snow cover starts after the middle of December even with a snow thickness >1.0 m. This effect of snow cover on the ground thermal regime can be explained with reference to the pattern of seasonal temperature variation. Early establishment of snow cover enhances the insulating impact over the entire cold season, thus warming and eventually thawing the permafrost. The insulating effect is substantially reduced when snow cover starts relatively late and snowmelt in the spring creates a huge heat sink, resulting in a favorable combination for permafrost existence.     

An integrated data-directed numerical method for estimating the undiscovered mineral endowment in a region

An integrated data-directed numerical method has been developed to estimate the undiscovered mineral endowment within a given area. The method has been used to estimate the undiscovered uranium endowment in the San Juan Basin, New Mexico, U.S.A. The favorability of uranium concentration was evaluated in each of 2,068 cells defined within the Basin. Favorability was based on the correlated similarity of the geologic characteristics of each cell to the geologic characteristics of five area-related deposit models. Estimates of the undiscovered endowment for each cell were categorized according to deposit type, depth, and cutoff grade. The method can be applied to any mineral or energy commodity provided that the data collected reflect discovered endowment.     

地震作用下平行地裂缝场地隧道动力响应分析

以西安地铁3号线小寨区间近距离平行地裂缝的特殊工程场地为工程研究背景,基于有限差分原理的FLAC3D数值模拟方法,研究地震和地裂缝场地沉降耦合荷载作用时地铁隧道地震动力响应问题。结果表明：地表峰值加速度在地裂缝附近取得最大值,且PGA放大系数由地裂缝向两侧逐渐衰减;地裂缝隧道场地水平地震土压力增量随着输入地震波峰值加速度PGA的增大而增大;上盘的水平土压力增量明显大于下盘,且曲线在地铁隧道处存在一个峰值;隧道结构中,左拱腰处水平土压力相比右拱腰及拱顶处水平土压力较大,且拱底与左拱腰处水平土压力一致;隧道拱顶处水平土压力增幅量明显,且隧道处水平土压力增量随输入地震波PGA的增大而增大,左拱腰处的水平土压力地震响应大于右拱腰,但增幅小于右拱腰。     

Application of the DDM and fracture mechanics model on the simulation of rock breakage by mechanical tools

A DDM (displacement discontinuity method) program coupled with a modified energy criterion is used to simulate the development of cracks and chips by indentation tools. In our analysis a cavity model is applied to represent the expansion of crushed rock to the surrounding rock and the cracks are formedin two-dimensional and quasi-static conditions. The model parameters, rock properties and load magnitudes are varied in the numerical calculations. The results show that chips are formed by multiple mechanisms of either tension or shear, or their combinations. The cracks may either propagate to the free surface to form chips or rest in the rock subsurface. The crack development is dependent upon rock and fracture properties, loading force and tool characteristics. The DDM is a convenient tool in the study of rock fragmentation and cracks.     

琼东南盆地块体搬运沉积区多类型水合物赋存特征与数值模拟

南海北部琼东南盆地陵水凹陷的钻探、三维地震与地球化学分析表明, 该区域发育热成因气控制的呈烟囱状反射特征的裂隙充填型和薄砂层的孔隙充填型水合物.不同站位水合物富集程度、厚度与赋存形态不同, 这种复杂水合物富集成藏的控制因素还有待进一步明确.本文利用宽频处理三维地震与随钻测井资料, 精细识别了裂隙充填型水合物发育的空间分布, 分析了断层与块体搬运沉积物对水合物赋存的影响, 通过建立重烃气体影响的Ⅱ型水合物稳定带底界, 并结合数值模拟方法, 定量模拟了多类型水合物形成与富集的控制因素.结果表明: 起源于基底隆起的断层连通了深部气源与浅部水合物稳定带, 控制着深部热成因气向上运移, 发育的多期块体搬运沉积内局部裂隙及下部的有利砂层, 使水合物在垂向上呈多层叠置分布特征.