Objective prism survey of qsos in the field centered at 10h40m + 00°00′     

Ran He  Jian-Sheng Chen 《Astrophysics and Space Science》1993,200(2):279-311

QSO objective prism survey was done for the field centered at 10^h40^m + 00°00. For the 348 objects selected, we present in this paper their positions,B _J magnitudes, spectra, and finding charts. Based on the sample containing 163 QSO candidates with higher reliabilities (F 3), the surface density of QSO candidates withB _J 20 is estimated to be about 4.5 per square degree.Work based on UKST plates.  相似文献   

船式支护在基坑中的应用     

何世达  徐忠  李燕枫 《岩土工程技术》2021,(1)

在深厚软土地区的基坑,对基坑底软土进行搅拌加固形成强度较高的底板而保证坑底稳定,侧壁采用支护桩支护保证侧壁的稳定使其不倾倒,支护桩与加固底板两者共同作用形成的船状结构支护体系类似轮船的船侧壁及船底板,以保证基坑的稳定。结合具体的工程实例,介绍了船式支护的侧壁及底板的设计方法。工程案例成功实施,监测结果表明,船式支护既可避免支护桩嵌固深度过长,又利于软土的土方施工及工程桩的保护,是安全可靠的,对类似工程有一定的参考意义。  相似文献   

On the spatial characteristic of the short term and imminent anomalies of underground water behaviors before strong earthquake     

杜学彬  刘耀炜  倪明康 《地震学报(英文版)》1997,10(4):523-533

Ｏｎｔｈｅｓｐａｔｉａｌｃｈａｒａｃｔｅｒｉｓｔｉｃｏｆｔｈｅｓｈｏｒｔ┐ｔｅｒｍａｎｄｉｍｍｉｎｅｎｔａｎｏｍａｌｉｅｓｏｆｕｎｄｅｒｇｒｏｕｎｄｗａｔｅｒｂｅｈａｖｉｏｒｓｂｅｆｏｒｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅＸＵＥ－ＢＩＮＤＵ（杜学彬）...  相似文献   

硫铅酸盐“S”型瞬凝水泥干法护壁堵漏技术研究          下载免费PDF全文

彭振斌 《探矿工程》1995,(2):41-42,60

介绍了硫铝酸盐“Ｓ”型瞬凝水泥干法者漏时使用的配方,阐述了输送工具和扫孔钻具的设计以及灌注工艺技术。  相似文献   

Slip-weakening constitutive relation and the structure in the vicinity of a shear crack tip     

Changrong He 《Pure and Applied Geophysics》1995,145(3-4):747-757

Shear-crack model with a cohesive zone (or breakdown zone) is appropriate for the analysis of a fault surface in which slip distribution is strongly nonuniform. As the slipped portion advances, slip-weakening occurs over the so-called cohesive zone, a distance behind the fault tip. For a prescribed strength vs. displacement constitutive relation, however, the zone structure is difficult to determine by an analytical method except for some simple cases, thus it often requires a certain numerical procedure. This work proposes a numerical procedure to obtain approximated solutions of the problem by combining a series of elastic solutions derived bySmith (1974). The series is linearly combined and the unknown coefficients are determined by a nonlinear least square method. This method can fit a wide range of prescribed strength vs. displacement relations which may be simple algebraic relations or curves obtained by laboratory tests. By examining the residual errors and in comparison with a derived result in which linear stress is assumed within the zone, it could be concluded that the results provide good accuracy. Moreover, because the results are written in formulae, they can be easily referred to or used. By fitting constitutive curves in many different shapes, it is found that the stress distribution within the zone is more sensitive to the constitutive curve shape than the displacement. The most interesting fact is that the zone size is not sensitive to the curve shape, i.e., the zone size can be estimated by $$R = 3\mu \zeta \upsilon _c /\{ 2(1 - \upsilon )(\tau _c - \tau _f )\}$$ with ζ=1±0.11 for most cases.  相似文献   

中国大陆第四纪地壳运动时程   总被引：5，自引：0，他引：5  

冯希杰 《地质论评》1992,38(3):210-214

本文从中国大陆有代表性的青藏高原、黄土高原、三峡地区着手,进行了新构造运动剖析。并结合全国火山活动期次,总结出中国大陆第四纪地壳运动的时程变化。从而为进一步探讨新构造运动特点和规律,为国民经济建设及人类生存环境提供了一定的地质背景资料。  相似文献   

冀西北长城纪宣龙式铁矿层中微体植物化石的发现及其意义   总被引：10，自引：0，他引：10  

杜汝霖  刘志礼 《地质论评》1992,38(2):184-189

本文研究的是笔者等在冀西北长城系串岭沟组宣龙式铁矿层中发现的微体植物化石,这些化石都保存在铁质叠层石(肾状赤铁矿)和铁质核形石(鲕状赤铁矿)的基本层中。微化石以丝状体为主,部分为球状体。归属于原核生物蓝藻门颤藻科的两个属和色球藻科的一个属。化石层同位素年龄约在1800—1757Ma。这些化石与北美冈弗林特组微化石比较,既有些相似,又有些区别。该化石的发现为研究铁矿的成因,指示沉积环境及层位对比都很有意义。  相似文献   

Synchronization of seismoacoustic emission with deformation of the Earth’s upper crust     

A. S. Belyakov  V. S. Lavrov  Corresponding Member of the RAS A. V. Nikolaev  L. L. Khudzinskii 《Doklady Earth Sciences》2006,407(1):258-258

  相似文献   

Strength and stability of frictional sliding of gabbro gouge at elevated temperatures   总被引：7，自引：1，他引：7  

Changrong He  Wenming Yao  Zeli Wang  Yongsheng Zhou   《Tectonophysics》2006,427(1-4):217

To investigate the strength of frictional sliding and stability of mafic lower crust, we conducted experiments on oven-dried gabbro gouge of 1 mm thick sandwiched between country rock pieces (with gouge inclined 35° to the sample axis) at slip rates of 1.22 × 10^− 3 mm/s and 1.22 × 10^− 4 mm/s and elevated temperatures up to 615 °C. Special attention has been paid to whether transition from velocity weakening to velocity strengthening occurs due to the elevation of temperature.Two series of experiments were conducted with normal stresses of 200 MPa and 300 MPa, respectively. For both normal stresses, the friction strengths are comparable at least up to 510 °C, with no significant weakening effect of increasing temperature. Comparison of our results with Byerlee's rule on a strike slip fault with a specific temperature profile in the Zhangbei region of North China shows that the strength given by experiments are around that given by Byerlee's rule and a little greater in the high temperature range.At 200 MPa normal stress, the steady-state rate dependence a − b shows only positive values, probably still in the “run-in” process where velocity strengthening is a common feature. With a normal stress of 300 MPa, the values of steady-state rate dependence decreases systematically with increasing temperature, and stick-slip occurred at 615 °C. Considering the limited displacement, limited normal stress applied and the effect of normal stress for the temperatures above 420 °C, it is inferred here that velocity weakening may be the typical behaviour at higher normal stress for temperature above 420 °C and at least up to 615 °C, which covers most of the temperature range in the lower crust of geologically stable continental interior. For a dry mafic lower crust in cool continental interiors where frictional sliding prevails over plastic flow, unstable slip nucleation may occur to generate earthquakes.  相似文献   

Can stable isotopes be used to monitor landfill leachate impact on surface waters?     

Jessica C. North  Russell D. Frew  Robert Van Hale 《Journal of Geochemical Exploration》2006,88(1-3):49

Bacterially mediated methanogenesis in municipal solid waste landfills has been shown to cause an enrichment of carbon stable isotope ratios of dissolved inorganic carbon and hydrogen stable isotope ratios of water in landfill leachate. In the present study, we investigate the universality of this enrichment in leachate obtained from four diverse landfill sites in New Zealand. At each site, surface water samples upstream and downstream of landfills were analysed to examine the applicability of stable isotope ratios as a tool for monitoring leachate contamination in landfill-associated streams. The design of leachate collection systems, operational history, and landfill location appeared to strongly influence leachate isotopic values and the effectiveness of isotope ratios as an environmental monitoring tool for surface water.  相似文献