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排序方式: 共有197条查询结果,搜索用时 140 毫秒
191.
192.
龙永煤田地质构造复杂,岩性倾角变化大,断层破碎带多,在应用金刚石绳索取心工艺钻进时,常常存在着掉块、坍塌和漏失现象,造成孔内事故多,钻进效率低等问题。通过反复的实践研究,总结出根据不同的地层特性,选择适宜的钻孔口径、钻具级配和钻头型号,配制不同的冲洗液;针对地层的漏失特点和漏失量的大小,采用不同的堵漏材料的技术措施,从而初步解决了在该区钻进时遇到的技术难点,减少了孔内事故的发生,将钻月效率由430m提高到603m,取得了良好的经济效益。 相似文献
193.
Kavita Pandit 《The Professional geographer》2000,52(3):483-493
The age patterns of U.S. internal migration, while examined extensively at the national level, have not been fully explored at the regional scale. This study examines, using 1985 ‐ 1990 census data, the state‐level variations in two aspects of lifecycle mobility: the mobility level, or the average number of moves made over the lifecycle, and the mobility timing, or the age at which half the lifetime moves are completed. It further delineates typologies of states based upon their age structure of mobility. The study found that regional patterns in the mobility level showed some evidence of the Snowbelt‐Sunbelt patterns that characterized economic restructuring in the 1980s. Geographic patterns of mobility timing were less clear; however states in the West and the South showed somewhat more young distributions than the other regions. Further, there was a statistically significant relationship between mobility levels and timing: states with higher mobility levels also exhibited older mobility profiles, as a consequence of disproportionately high elderly mobility rates. The study highlights the regional differences in mobility behavior, and the interplay between the “how much” and the “when” of mobility. 相似文献
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195.
在裂隙,岩溶裂隙含水层水文地质条件研究基础上,根据炸药在水中原理,介绍了控制炸药爆炸能量和孔内爆炸方法,达到对岩体的爆炸致裂以及对原储导水裂隙的冲刷作用,提高了地下工程中钻孔或水源井的疏排效率,同时又保护站孔孔壁不被破坏。 相似文献
196.
LNG接收站取水流道内水流形态复杂,泥沙淤积问题往往难以避免,特别是在含沙量较高水域,流道内泥沙淤积可能威胁接收站的正常运营。为实现LNG取水泵站不停机条件下清淤,开展取水泵站射流冲刷物理模型试验,模拟了射流冲沙装置开启后吸水间射流水流特征及冲刷效果,探究了射流冲刷设置的喷嘴与翼墙夹角、射流流量、冲刷时间等因素影响下流道内减淤清淤效果。试验结果表明,在理想状态下吸水间射流冲沙装置连续作用12 h基本可达到较为理想的清淤效果;一次大风浪过后,装置连续作用0.5 h基本可达到较为理想的清淤效果。清淤效果视射流流量、喷嘴与翼墙夹角以及冲刷时间不同而有差别。结合取水泵站泥沙淤积物理模型试验研究成果,取水泵站淤积区主要发生在前池、过滤池末端、吸水间和消防泵附近,建议在这些区域安装射流冲沙装置,实现不停机状态下的减淤清淤,提高取水安全保证率,从而提高运营效益。 相似文献
197.
J.O. Blanton A.J. Garrett J.S. Bollinger D.W. Hayes L.D. Koffman J. Amft T. Moore 《Estuarine, Coastal and Shelf Science》2010
A study of tracer transport and retention in a small tidal creek and marsh system located in the southeastern US was conducted using a three-dimensional hydrodynamic model and data from a dye tracer release. The model simulated tidally driven flow, including inundation and drying out of the marshes and the dispersal of the dye tracer. Flow measurements in the tidal creek showed that the simulations appeared to generally duplicate the tidally driven flow into and out of the tidal creeks and marshes. The dye tracer experiment was conducted to test the hydrodynamic model's ability to simulate dispersal of a point release of pollutants into the creek during an incoming tide. The simulations reproduced much of the experimental measurements, but bathymetric errors and lack of resolution of the smallest arms of the tidal creeks affected the ability to faithfully reproduce the initial peak in measured dye tracer concentrations at a sampling location far from the boundary. The lack of the smallest tidal creeks led to some trapping of water and dye in the marshes. Two independent estimates of flushing time yielded values between 1.6 and 2.4 days. An uncertainty analysis indicates that model simulations are sensitive to variations in parameters such as water depth and marsh grass density. On the other hand, omission of the smallest tidal creeks in simulations may be partially offset by decreasing marsh grass density. Further improvements must rely on more accurate and detailed bathymetric data that resolves the smaller arms of the tidal creeks and includes quantitative information about the density and distribution of marsh grass. 相似文献