顶承静压桩托换施工技术

通过某钢厂的应用实例,介绍了顶承静压桩基础托换施工的设计及工艺方法,并进行沉降对比分析。     

地籍信息系统中的时空信息管理

在描述地籍管理中时间及其关系的基础上 ,提出了地籍信息依据变更频度对历史数据进行分割存贮的分频基态修正法 ,并在对时态信息处理分析的基础上阐述了基于事件的时空数据模型。     

The air flow and heat transfer in gravel embankment in permafrost areas

A comparative numerical investigation of transient temperature profile and pore-air velocities in horizontal rock block embankments are conducted using the "gravels model", in which the embankment is composed of stones and air, and the "porous media model" respectively. As the velocities from the "gravels model" directly reflect the true flow of air and winter-time convection, in this paper it can be concluded that computational results from the "gravels model"are superior to the "porous media model". In addition, the "gravels model" has the advantages of reflecting the effect of the dimensions and collocation of gravels upon the temperature fields.Therefore, the computation of the gravels embankment is mainly based on the gravels model.Simulation results show that in summer, a clockwise circulation of the pore-air extends throughout most of the embankment. However its motion is very weak that results in relatively straight horizontal isotherm lines. And heat transfer is mainly maintained through conduction. But in winter, the pore-air velocities are higher and multiple vortexes are formed in the embankment.Natural convection then becomes the dominant influence on the isotherm shapes within the embankment. The isotherms are complex and alternative upward and downward flowing plumes exist. The winter-time convection can further reduce the temperature of the foundation soil beneath the gravel embankment. In addition, the effects of the gravel dimensions within the embankment have been analyzed and compared in the gravels model. It shows that in winter, large stones, e.g. 200 mm, lead to stronger vortexes than those of small stones, say 60 mm. Consequently, the zone of low-temperature beneath the large-stone embankment extends deeper into the ground.     

联合像素级和对象级分析的遥感影像变化检测

为改善高空间分辨率遥感影像的变化检测精度,提出一种联合像素级和对象级分析的变化检测新框架。首先将多时相影像进行叠合,对叠加影像进行主成分分析,并利用基于熵率的方法对第一主成分影像进行分割,通过改变超像素数目来获取多层次不同尺寸大小的超像素区域。同时,对多时相影像进行光谱差异和纹理差异分析,采用自适应PCNN神经网络方法进行图像融合,利用水平集(CV)方法对融合后的影像进行分割获取像素级变化检测结果。最后,结合多尺度区域标记矩阵对检测结果进行变化强度等级量化和决策级融合,作为变化检测的后处理部分,以获取最终的对象级变化检测结果。采用SPOT-5多光谱影像进行试验。结果表明这种新框架可以有效集成基于像素和基于对象两种图像分析方法的优势,能够进一步提高变化检测过程的稳定性和适用性。     

Long-term groundwater storage changes and land subsidence development in the North China Plain (1971–2015)

The North China Plain (NCP) has been suffering from groundwater storage (GWS) depletion and land subsidence for a long period. This paper collects data on GWS changes and land subsidence from in situ groundwater-level measurements, literature, and satellite observations to provide an overview of the evolution of the aquifer system during 1971–2015 with a focus on the sub-regional variations. It is found that the GWS showed a prolonged declining rate of ?17.8?±?0.1 mm/yr during 1971–2015, with a negative correlation to groundwater abstraction before year ~2000 and a positive correlation after ~2000. Statistical correlations between subsidence rate and the GWS anomaly (GWSA), groundwater abstraction, and annual precipitation show that the land subsidence in three sub-regions (Beijing, Tianjin, and Hebei) represents different temporal variations due to varying driver factors. Continuous drought caused intensive GWS depletion (?76.1?±?6.5 mm/yr) and land subsidence in Beijing during 1999–2012. Negative correlations between total groundwater abstraction and land subsidence exhibited after the 1980s indicate that it may be questionable to infer subsidence from regional abstraction data. Instead, the GWSA generally provides a reliable correlation with subsidence. This study highlights the spatio-temporal variabilities of GWS depletion and land subsidence in the NCP under natural and anthropogenic impacts, and the importance of GWS changes for understanding land subsidence development.     

A bond-based smoothed particle hydrodynamics considering frictional contact effect for simulating rock fracture

Acta Geotechnica - A bond-based smoothed particle hydrodynamics considering hybrid friction contact (BB-SPH-HFC) method is proposed to simulate the dynamic friction behavior during crack initiation...     

Study on fish community structure in the Zhujiang Estuary and its adjacent waters

I~IOXMoreattentionhasbenpaidtothefishcornlnwhtiesintheestuaryandcoastalwaters,andanemphasishashogivenontheuseofvariousdiversityindicesandmultivariateanalysismethanethat~onthaisindicesinthestudyofthecharacteristicsOffishcornmwhties(Zhuetal.,1994;Zhuet...     

THE SCHEME FOR THE DATABASE BUILDING AND UPDATING OF 1:10 000 DIGITAL ELEVATION MODELS

The National Bureau of Surveying and Mapping of China has planned to speed up the development of spatial data infrastructure (SDI) in the coming few years. This SDI consists of four types of digital products, i. e., digital orthophotos, digital elevation models,digital line graphs and digital raster graphs. For the DEM,a scheme for the database building and updating of 1:10 000 digital elevation models has been proposed and some experimental tests have also been accomplished. This paper describes the theoretical (and/or technical)background and reports some of the experimental results to support the scheme. Various aspects of the scheme such as accuracy, data sources, data sampling, spatial resolution, terrain modeling, data organization, etc are discussed.     

THE SCHEME FOR THE DATABASE BUILDING AND UPDATING OF 1∶10 000 DIGITAL ELEVATION MODELS

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河南文化遗址中自然变形现象的新发现

本文通过在河南新密、洛阳和南阳等地的实地考察,发现了一批存在于文化遗址中的自然变形现象,时代涉及新(旧)石器过渡期、东周到北魏时期等。其中在新密李家沟旧石器向新石器过渡期遗址发现三组裂缝,可代表三次构造变形活动。洛阳汉魏故城发现两类裂隙,一类穿切性较好,应为构造裂隙;另一类贯通性差,应为干燥收缩裂隙。南阳东周文化遗址发现两组充填裂隙,一组走向北东,一组走向北西,两组正交,被砂土充填,应为地震液化脉体,显示所在地区东周后有地震活动发生。初步研究表明,这些自然变形现象与当地区域构造方向具有一定的相关性,说明这些遗迹为史前地震事件记录的可能性较大,进一步分析判定这些自然变形现象的形成机制,对河南地震考古工作及历史地震研究的进一步开展具有重要的现实意义。