An experimental study of the parameters influencing ultimate bearing strength of weak floor strata using physical modeling

The evaluation of the bearing strength characteristics of floor strata during an excavation process while under heavy loads from an overlying rock mass is one of the important factors in strata control of any underground mine. Plate loading tests on simulated floor strata were carried out for varying geotechnical conditions of weak floor strata. The physico-mechanical properties of weak floor strata evaluated in the experiments include unconfined compressive strength (c), elastic modulus (E), Poissons ratio () angle of friction (), and the moisture content (MC). The paper summarizes the results of (1) bearing strength tests using different sizes of circular loading plate (2) influence of various physico-mechanical parameters of weak floor strata on its floor bearing strength and (3) bearing strength analysis of weak floor in jointed rock mass. The outcome of the results show that the ultimate bearing strength decreases considerably with increase of footing plate size. The experimental results strongly support the earlier field investigation findings depicted by Zhanjing et al. (1992). Thus the contradictions about the plate size effect on bearing strength (Katsutoshi et al., 1998) are further eliminated. It was further investigated that apart from the plate size, ultimate bearing strength is strongly correlated with uniaxial compressive strength. A better correlation between moisture content and ultimate bearing strength with a regression coef.cient of 0.91 was also achieved. An excellent correlation between angle of friction () and ultimate bearing strength was found.     

BOOK REVIEWS

Book Reviewed in this article: Geography and the Third World. International Seminar, 14–18 May 1980, Kuala Lumpur, Malaysia . Ishmail Ahmad and Jamaluddin Md Jahi, eds. The Growth Dilemma: Residents' Views and Local Population Change in the United States . Mark Baldassare. Sport and Place: A Geography of Sport in England, Scotland & Wales . John Bale. The Deindustrialization of America: Plant Closings, Community Abandonment, and the Dismantling of Basic Industry . Barry Bluestone and Bennett Harrison. Selected Essays 1963–1975: Carl O. Sauer . Bob Callahen, ed. Housing and Planning in the Countryside . G. Clark. Conflict, Politics and the Urban Scene . Kevin R. Cox and R. J. Johnston, eds. Thematic Maps: Their Design and Production . David J. Cuff and Mark T. Mattson. Wine: A Geographic Appreciation . Harm Jan de Blij. USSR in Maps . J. C. Dewdney. Political Geography: A Contemporary Perspective . Ramesh D. Dikshit. Rethinking Human Adaptation . Rada Dyson-Hudson and Michael A. Little, eds. Sacred Sands: The Struggle for Community in the indiana Dunes . J. Ronald Engel. Geography of the Biosphere . A. Furley and Walter W. Newey. Disaster and Reconstruction . Robert Geipel. Glasgow: The Making of a City . Andrew Gibb. Design for Arid Regions . Giden S. Golany, ed. Urbanization and Cancer Mortality: The United States Experience, 1950–1975 . Michael R. Greenberg. Geology in the Nineteenth Century: Changing Views of a Changing World . Mott T. Greene. Colonización y Destrucción de Bosques en Panamá . Stanley Heckadon Moreno and Alberto McKay, eds. Urban Geography: A First Approach . David T. Herbert and Colin J. Thomas. The Visual and Spatial Structure of Landscapes . Tadahiko Higuchi. Climate from Tree Rings . M. K. Hughes, P. M. Kelly, J. R. Pilcher, and V. C. LaMarche, Jr., eds. The structure of Nineteenth Century Cities . James H. Johnson and Colin G. Pooley, eds. The American Planner: Biographies and Recollections . Donald A. Krueckeberg, ed. Urban Land Policy For the 1980s, the Message for State and Local Government . George Lefcoe, ed. Regional Planning: Evolution, Crisis and Prospects . Gill C. Lim, ed. Relevance and Ethics In Geography . Bruce Mitchell and Dianne Draper. China: The Geography of Development and Modernization . Clifton W. Pannell and Laurence J. C. MA. The Urban Retailing System . Robert B. Potter. Hants. Nonconventional Energy Resources . Philip R. Pryde. Caribbean Migrants: Environment and Human Survival on St. Kitts and Nevis . Bonham C. Richardson. Population and Resources . Harry Robinson. East Los Angeles: History of A Barrio . Ricardo Romo. Integrated Impact Assessment . Frederick A. Rossini and Alan L. Porter, eds. Environmental Aesthetics: Essays in Interpretation . Barry Sadler and Allen Carlson, eds. Earthwatch . Charles Sheffield. Field Techniques and Research Methods in Geography . Robert H. Stoddard. Haiti: Land of Poverty . Robert J. Tata. Weathering and Erosion: Sources and Methods in Geography . Stephen T. Trudgill. Once Beneath the Forest. Prehistoric Terracing in the Río Bec Region of the Maya Lowlands . B. L. Turner, II. The Historical Geography of Scotland since 1707 . David Turnock.     

中国对虾Penaeus orientalis Kishinouye养成期虾池细菌生态学初探

本文从细菌生态学角度结合理化因子阐述了中国对虾养成期虾池水体和底泥中异养菌、条件致病菌(几丁质降解菌和弧菌)的数量变动及菌属组成状况,并与未养虾池作了比较分析。结果表明:虾池内水体中异养菌和条件致病菌数量均比未养虾池水体中的高1～2个数量级,底泥中条件致病菌数量略高于未养虾池。虾池内、外水体中的细菌属组成基本一致,均以革兰氏阴性菌为主,而底泥中的革兰氏阳性菌稍占优势。     

A bucket wheel dredge system for offshore tin mining beyond the 50 m water depth

A bucket wheel dredge (BWD) for offshore tin mining is part of the long term plan of PT Timah Tbk to identify new dredging technologies for mining in greater than 50 m water depths. Measured tin-ore physical properties are used in a new BWD computer model to investigate deep water tin mining. The model simulates the cutting and hydraulic transport of submerged tin-ore. The results show that hydraulic tin mining beyond water depths of 50 m is feasible. It is best to employ hydraulic transport for lifting the tin-ore from the ocean floor to the surface and to use barges to transport the tin-ore to land processing plants.     

黄茅海内治导线对潮汐要素影响的试验研究

通过物理模型试验 ,研究了黄茅海内不同治导线对潮汐要素的影响 ,得出治导线对河口湾内的潮位变化随着上游径流量的增加而逐渐减弱的结论。中水大潮时 ,湾顶与湾腰处高潮位降低 ,低潮位抬高 ,其幅度与治导线进占的海域面积成正比。洪水大潮时 ,高潮位一般也降低。低潮位则有时降低 ,有时有所抬高。河口湾治导线实施后 ,涨潮最大流速、平均流速和落潮平均流速均有所减小 ,但落潮最大流速不减反增。涨、落潮潮量有不同程度的减少 ,其减幅与治导线的进占规模成正比。各站的高、低潮位发生时间都有前移趋势 ,治导线越往外推 ,潮时前移量就越大。本文对这些现象的成因进行了分析 ,并就潮位、潮流速及潮流量的变化对防洪水位和交通航运水深的影响作了阐述。     

An automated full waveform logging system for high-resolution P-wave profiles in marine sediments

An automated, PC-based logging system has been developed to investigate marine sediment cores by full waveform transmission seismograms. High-resolution P-wave velocity and amplitude attenuation profiles are simultaneously derived from the transmission data to characterize the acoustic properties of the sediment column.A pair of ultrasonic, piezoelectric wheel probes is used to generate and record the transmission signals travelling radially through the sediment core. Both unsplit and split cores are allowed. Mounted in a carriage driven by a stepping motor via a shaft the probes automatically move along the core liner, stopping at equidistant spacings to provide a quasi-continuous inspection of the core by the transmission data. The axial travel distance and the core diameter are determined by digital measuring tools.First arrivals are picked automatically from the transmission seismograms using either a threshold in the seismogram's envelope or a cross-correlation algorithm taking the zero-offset signal of both wheel probes into account. Combined with the core diameter these first arrivals lead to a P-wave velocity profile with a relative precision of 1 to 2 m s^–1. Simultaneously, the maximum peak-to-peak amplitudes of the transmission seismograms are evaluated to get a first idea on the amplitude attenuation along the sediment core.Two examples of gravity cores taken during a recent cruise of R.V. METEOR in the Western Equatorial Atlantic are presented. They yield that the P-wave profiles can be used for locating strong and fine-scale lithological changes, e.g. turbidite layers and slight variations in the sand, silt or clay content. In addition, the transmission seismograms and their amplitude spectra obviously seem to reveal a correlation between the relative amount of low-frequency spectral components and the sediment grain size, and thus provide a tool for the determination of additional, related physical or sedimentological parameters in future investigations.     

Morphological evolution of gravel and sand extraction pits, Tromper Wiek, Baltic Sea

The growing demand for marine mineral resources introduces anthropogenic impacts in the coastal zone, among others also through aggregate dredging. Pits created by anchor hopper dredging may affect local sediment budgets, local hydrodynamics and biological habitats. In this study we investigate the processes and time-scales of pits refilling at two extraction sites over 6 years following cessation of dredging. We focused on the evolution of a single pit at a gravel extraction site and the development of a group of three pits located at a sand extraction site. In the case of the gravel pit, a series of six sonograph and two multibeam surveys were evaluated. We observed a spatial expansion of the edge of the pit, decreasing availability of screened sand in the neighbourhood of the pit (a possible source of refilling), and a slowing down of the refilling process with time. At the sandy pit site a series of seven sonographs and two multibeam surveys were available. We observed a smoothing of the edges and larger mean refilling rates than in the gravel pit case. We conclude that the most effective method for monitoring of pit evolution is to make measurements every six months by simultaneously deploying sidescan sonar and multibeam devices.     

The chemical, physical and structural properties of estuarine ice in Great Bay, New Hampshire

The purpose of this study was to provide general information on the chemical, physical and structural properties of estuarine ice and show how it compares with sea ice found at higher latitudes in order to determine whether the ice in Great Bay can be used as an analog in the study of arctic sea ice.Ice cores and water samples were collected during the 1983–1984 winter season at Adams Point in Great Bay, New Hampshire. Concentrations of chloride, nitrogen (as nitrate and nitrite), bromide, phosphate, sulfate and silicate were determined for samples chosen on the basis of identifiable stratigraphic layers (i.e. bubble size and shape, sediment layers, etc.).Similarities between ice formation in Great Bay and those in the arctic regions include the nature of the freezing process and the ice types produced. In addition, the distribution and concentration of chemical constituents were found to be similar to those observed in arctic sea ice. Factors affecting the chemistry of the ice in Great Bay include rainfall during the freezing season, the presence of sediment layers in the ice cores, the nature of incorporation of brine into the crystal structure of the ice and the drainage of brine.     

2015年12月乌鲁木齐极端暴雪成因分析

利用常规观测资料、NCEP FNL（1o×1o）再分析资料以及卫星、雷达资料,对乌鲁木齐2015年12月10日-12日的极端暴雪天气过程的环流演变及暴雪产生和维持的机制进行了初步分析。结果表明：此次暴雪过程是欧洲脊发展推动乌拉尔山地区长波槽东移南压,同时配合低层风场的辐合切变、地面冷锋及地形强迫抬升等共同作用造成此次过程。500hPa偏南气流,700hPa、850hPa的偏北气流在乌鲁木齐的交汇有利于加强冷暖空气的汇合和水汽的聚集,为乌鲁木齐强降雪提供了有利的动力条件。各物理量场的配合及地形作用使得此次乌鲁木齐大暴雪持续时间长,降雪强度大;降雪前期乌鲁木齐逆温使不稳定能量集中释放;散度辐合中心最强时段及上升运动均与降雪时段对应,乌鲁木齐地形引起的强迫抬升为暴雪提供有利的垂直环流;水汽的主要来源为阿拉伯海及孟加拉湾,且水汽在中低层的辐合上升明显,水汽通量散度辐合中心的出现时间对本次乌鲁木齐大暴雪的最强降水时段有很好的指示意义。