地质岩心钻孔人工造斜方法实践          下载免费PDF全文

孙孝刚  卢忠友  张涛 《探矿工程》2016,43(11):15-20

在岩心钻探施工过程中,钻遇岩（矿）心脱落需要补取岩心,或钻具脱落、埋钻和烧钻需要绕障时,人工造斜方法是解决问题的有效手段。钻孔较浅,造斜孔段刚好在变径后的位置,且上部孔壁稳定,易于扩孔和下套管,宜选用异径偏心楔人工造斜;钻孔较深,不能改变口径,造斜孔段岩层硬度较大,宜选用同径偏心楔人工造斜;钻孔较深,造斜孔段岩层硬度不大（如煤系地层中的煤层、泥岩等）,宜选用同径自然造斜。选用偏斜楔造斜时,偏斜楔长度、偏斜角大小和导斜槽直径的合理选择,偏斜楔下入钻孔过程中的正确操作;选用同径自然造斜,水泥浆灌注孔段位置确定、水泥浆凝固后达到一定的强度和造斜过程中合理的钻进参数,是造斜成功的关键。  相似文献   

Visa restrictions and economic globalisation     

《Applied geography (Sevenoaks, England)》2017

The cross-border mobility of people, goods and services, and capital has expanded enormously both in intensity and diversity over recent decades. States have a general interest in facilitating these flows in order to benefit from economic globalisation. Yet, mainly due to security concerns, most governments grant visa-free mobility only very selectively. Drawing on a new bilateral visa policy database covering up to 194 destination and 214 origin countries over the 1995 to 2013 period, our analysis finds that the introduction of a visa restriction by a destination country for citizens from a particular origin country deters tourism inflows by about 20 per cent. Visa restrictions also reduce bilateral trade and foreign investment, but to a smaller extent than previous studies have suggested. We further find that some of the deterred flows in tourists and goods and services are redirected to other (visa-free) destinations. This deterrence-cum-deflection effect of restrictive visa policies implies significant economic costs for both visa-issuing and visa-targeted countries, but it creates some positive externalities for countries with a more liberal visa policy. Liberalised visa policies would in particular help poorer countries to partake more in the benefits of economic globalisation.  相似文献   

Inertial Instability of Arbitrarily Meandering Currents Governed by the Eccentrically Cyclogeostrophic Equation     

Hideo Kawai 《Journal of Oceanography》2003,59(2):163-172

Using natural coordinates, we have derived a criterion for the inertial instability of arbitrarily meandering currents. Such currents, governed by the eccentrically cyclogeostrophic equation, are adopted as the basic current field for the parcel method. We assume that any virtual displacement which is given to a water parcel moving in the basic field has no influence on this field. From the conservation of mechanical energy for a virtual displacement we derive an inertial instability frequency ω _m = [(f + 2u/r)Z]^0.5 for the eccentrically cyclogeostrophic current, where f is the Coriolis parameter, u the velocity (always positive), r the radius of curvature of a streamline (negative for an anticyclonic meander), and Z the vertical component of absolute vorticity. If ω _m ² is negative, the eccentrically cyclogeostrophic current becomes unstable. Although the conventional, centrifugal instability criterion, derived from the conservation of angular momentum in a circularly symmetric current field, has a certain meaning for a monopolar vortex, it contains a radial shear vorticity that is difficult to use in arbitrarily meandering currents. The new criterion ω _m ² contains a lateral shear vorticity that is applicable to arbitrarily meandering currents. Examining instabilities of concentric rings with radii of 50–100 km, we consider reasons why the anticyclonic supersolid rotation has been very much less frequently observed than the cyclonic supersolid rotation, despite a prediction of some common stability and a rapid change in radial velocity gradient for the former. Classifying eccentric streamlines into the large and small curvature-gradient types, we point out that the large-gradient curvature in anticyclonic rings is apt to be unstable. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

考虑海床变形的裸露悬跨海底管道静力分析     

邢静忠  柳春图 《海洋工程》2007,25(4):21-26,38

针对裸露悬跨海底管道,考虑线弹性海床刚度,利用梁的小挠度理论,研究管道在自重作用下的变形和内力,推导给出了未脱离海床的管道段和悬跨管道段的变形和内力公式。在跨度较大的悬跨情况下,悬跨管道段较大的向下弯曲变形可能引起海床上管道脱离海床而翘起。建立管道翘起的判定准则,对于翘起情况推导相应的计算公式,通过算例给出翘起情况下管道的变形和内力。通过计算分析发现:工程上多数悬跨是翘起情况,没有翘起的计算公式只适应于跨度较小的悬跨管道。同时翘起情况下不同海床刚度对悬跨管道无量纲内力影响不大。  相似文献   

Trial and Numerical Analysis of Specimen Pipelay     

HE  Yanping 《中国海洋工程》2002,16(2):257-262

Subsea pipelay has a relatively long history. In recent years, there has been a domestic need for the laying of large diameter thin wall pipes. A land-based trial for the large diameter thin wall specimen pipe is described in this paper. Re-gression analysis is performed for the trial data and the formula derived can express the trial data very well. Numerical analysis is adopted to compute various trial conditions. Then the numerical model is revised with the trial results, which are consistent with each other. After summarization of the results of trial and numerical analysis, the characteristics are described of the spatial configuration during the laying of the pipe and it is concluded that the maximum strain appears around the center of the raised pipeline. In the end, a reference Standard, which limits the maximum stress below the yield stress is provided.  相似文献   

Modulus of Subgrade Reaction for Laterally Loaded Piles in Multiple Layered Foundation   总被引：1，自引：1，他引：1  

Lu Ziai Associate Professor  Dept. of Navigation  Ocean Engineering  Hohai University  Nanjing 《中国海洋工程》1997,(4)

-According to the field test data of laterally loaded steel piles at home and abroad,an empiri-cal formula for evaluating the modulus of subgrade reaction under static load in layered soil is proposed.The suggested formula takes account of not only non-linearity of K_s with the depth but also its variationwith the load.It is shown that the computed bending moments along the pile shaft and the deflection atthe pile top are consistent with the measured ones.  相似文献   

北半球大气遥相关型冬夏差异及其与温度场关系的探讨   总被引：2，自引：2，他引：0  

陈芳丽  黎伟标 《大气科学》2009,33(3):513-523

利用55年的NCEP/NCAR再分析资料, 采用合成分析等方法探讨了冬、 夏季北半球大气遥相关型的差异及其与温度场的关系。主要结果有: 北半球冬、 夏季典型的大气遥相关型具有很大的差异, 且大气遥相关路径的偏折与温度场的变化有密切的关系。北半球冬季, 呈经向型分布特征的大气遥相关路径在温度纬向梯度正负号发生改变处发生偏折; 而在北半球夏季, 由于温度场分布呈现纬向特征, 遥相关路径不易产生南北向的偏折, 从而使得异常中心基本上沿纬圈分布, 呈明显的纬向特征。此外, 由于冬季等温线南北起伏明显的区域往往位于东西方向海陆交界处, 因此冬季大气遥相关路径往往在东西向海陆交界处发生偏折。  相似文献   

灵敏电流计特性参数测量方法探讨     

曾桂芬 《成都信息工程学院学报》1999,(3)

讨论了灵敏电流计特性参数的两种常用测量方法，推导出它们的测量误差公式，分析了造成测量误差的诸因素，提出一种能减小测量误差的新方法。  相似文献   

Large Deflection Dynamic Response Analysis of Flexible Hull Beams by the Multibody System Method     

ZHANG Xiaojun WU Guorong 《中国海洋大学学报(英文版)》2007,6(2):205-208

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多宝山-铜山陡斜矿体深孔受控定向钻进工艺          下载免费PDF全文

樊腊生  陈尚喜 《探矿工程》1998,(2):31-32

在老矿区勘探时,针对新布置的钻孔大多数是两老孔中间的加密孔或后排孔这一特点,给出了新布置钻孔轴线的设计方法以及采取的造斜、纠斜技术措施,取得了较好的效果。  相似文献