冻土区输电线路塔基选位的影响因素分析   总被引：1，自引：0，他引：1  

程东幸  张建民  刘厚健  俞祁浩  刘志伟 《工程地质学报》2009,17(3):329-334

青海西藏500kV直流联网输电线路工程跨越整个青藏高原,其生存环境不可避免与冻土有着紧密联系,冻土特有的冻胀、融沉特性给线路的勘测、设计、施工及后期运营带来了极大挑战。本文对取自青藏高原的原状和重塑冻土样样品进行了物理力学试验。结果表明:同种土在不同含冰量下,随含冰量的增大,则冻融特性敏感性增强;不同性质的土,在含冰量相同的情况下,颗粒越细,则冻融特性越敏感。同时,分析认为:塔基地质环境、不良冻土现象、不同地貌单元、冻土的热稳定性特征及施工作业便捷性等都是影响塔基稳定性的重要因素。  相似文献   

Hydrous olivine (Mg_{1? y?} Fe²⁺_y)_{2? x} ?v _x ? SiO₄H_{2 x} – a new DHMS phase of variable composition observed as nanometer-sized precipitations in mantle olivine     

N. R. Khisina  R. Wirth 《Physics and Chemistry of Minerals》2002,29(2):98-111

 An olivine grain from a peridotite nodule 9206 (Udachnaya kimberlite, Siberia) was investigated by TEM methods including AEM, HRTEM, SAED and EELS techniques. A previous study of the 9206 olivine sample revealed OH absorption bands in the IR spectrum and abundant nanometer-sized OH-bearing inclusions, of hexagonal-like or lamellar shape. Inclusions, which are several hundred nm in size, consist of 10 ? phase, talc and serpentine (chrysotile and lizardite). The lamellar (LI) and hexagon-like small inclusions of several ten nm in size (SI) are the topic of the present paper. AEM investigations of the inclusions reveal Mg, Fe and Si as cations only. The Mg/Si and Fe/Si atomic ratios are lower in the inclusions than in the host olivine. The Si concentration in the olivine host and both lamellar inclusions and small inclusions is the same. A pre-peak at 528eV was observed in EEL spectra of LI and SI, which is attributed to OH⁻ or Fe³⁺. From these data it is concluded that there is a OH⁻- or Fe³⁺-bearing cation-deficient olivine-like phase present. HRTEM lattice fringe images of LI and SI exhibit modulated band-like contrasts, which are superimposed onto the olivine lattice. Diffraction patterns (Fourier-transforms) of the HREM images as well as SAED patterns show that the band-like contrasts in HRTEM images of the inclusions are caused by periodic modulations of the olivine lattice. Three kinds of superperiodicity in the olivine structure such as 2a, 3a and 3c, were observed in SAED patterns. The corresponding olivine supercells labelled here as Hy-2a, Hy-3a and Hy-3c were derived. The M1-vacancies located in the (100) and (001) octahedral layers of the olivine lattice are suggested to form ordered arrays of planar defects (PD), which cause the band-like contrasts in HRTEM patterns as well as the superperiodicity in the SAED patterns. The vacancy concentrations as well as the chemical composition of Hy-2a, Hy-3a and Hy-3c olivine supercells were calculated using crystal chemical approaches, assuming either {(OH)^< _O−V^" _Me−(OH)^< _O}^↔, or {F e ^< _Fe −H _Me ^′}^↔ or {2F e ^< _Fe −V _Me ^"}^↔ point defect associates. The calculated theoretical compositions Mg_1.615Fe⁺² _0.135v_0.25SiO₄H_0.5 (Hy-2a) and Mg_1.54Fe²⁺ _0.12v_0.33SiO₄H_0.66 (Hy-3a and Hy-3c) are in a good agreement with the AEM data on inclusions. Hy-2a, Hy-3a and Hy-3c are considered to be a hydrous olivine with the extended chemical formula (Mg_1-yFe²⁺ _y)_2−xv_xSiO₄H_2x. The crystal structure of hydrous olivine is proposed to be a modular olivine structure with Mg-vacant modules. The crystal chemical formula of hydrous olivines in terms of a modular structure can be written as [MgSiO₄H₂] · 3[Mg_1.82Fe_0.18SiO₄] for Hy-2a, [MgSiO₄H₂] · 2[Mg_1.82Fe_0.18SiO₄] for Hy-3a and Hy-3c. Hydrous olivine is suggested to be exsolved from the olivine 9206, which has been initially saturated by OH-bearing point defects. The olivine 9206 hydration as well as the following exsolution of hydrous olivine inclusions is suggested to occur at high pressure-high temperature conditions of the upper mantle. Received: 15 January 2001 / Accepted: 2 July 2001  相似文献   

Characteristics and genesis of maghemite in Chinese loess and paleosols: Mechanism for magnetic susceptibility enhancement in paleosols   总被引：4，自引：0，他引：4  

Tianhu Chen  Huifang Xu  Qiaoqin Xie  Jun Chen  Junfeng Ji  Huayu Lu 《Earth and Planetary Science Letters》2005,240(3-4):790-802

Morphological characteristics and microstructures of magnetic minerals extracted from Chinese loess and paleosols were investigated using powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Our results indicate that maghemite in loess–paleosol sequences was transformed from magnetite through oxidation of magnetite. Maghemite transformed from eolian magnetite during chemical weathering has low-angle grain boundaries among maghemite nano-crystals. Some nano-crystalline maghemites with nanoporous texture resulted from microbe-induced precipitation of magnetite or transformation of poorly crystalline ferric Fe (oxy)hydroxides in presence of Fe-reducing bacteria. Aggregates of euhedral maghemite nano-crystals were transformed from magnetite magnetosomes. Both microbe-induced nanoporous magnetite and microbe-produced magnetite magnetosomes are directly related to microbial activities and pedogenesis of the paleosols. It is proposed that the formation of nano-crystalline maghemite with superparamagnetic property in paleosol results in the enhancement of magnetic susceptibility, although the total amount (weight percent) of magnetic minerals in both paleosol and loess units is similar. Our results also show that nano-crystalline and nanoporous magnetite grains prefer to transform into maghemite in semi-arid soil environments instead of hematite, although hematite is a thermodynamically stable phase. This result also indicates that a decrease in crystal size will increase stability of maghemite. It is also inferred that surface energy of maghemite is lower than that of hematite.  相似文献   

声波在两种多孔介质界面上的反射和透射   总被引：11，自引：1，他引：11       下载免费PDF全文

乔文孝  王宁 《地球物理学报》1992,35(2):242-248

本文导出了声波在两种多孔介质界面上反射、透射的一般计算公式.作为例子,数值计算了P₁波入射于界面时,P₁、P₂和S波的反射、透射系数与声波频率、入射角等量之间的关系.结果表明,各种模式波的反射、透射系数与入射角、多孔介质性质有关,在Biot特征频率附近与频率有关,并用界面两侧的法向能流相等验证了结果的正确性.若把多孔介质当作均匀固体处理,将会得到显著不同的结果.  相似文献   

爆震观测及爆震效应的工程评价     

谢建清 《华南地震》1992,12(1):64-73

本文介绍了有关爆破地震效应工程评价方法及其标准,汇报了观测仪器和得到的不同地区的经验传递系数,同时还介绍了部分振速及爆破地震烈度标准。  相似文献   

成层介质中交流电测井响应   总被引：27，自引：10，他引：27       下载免费PDF全文

张庚骥  汪涵明 《地球物理学报》1995,38(6):840-849

本文给出了纵向成层、径向不均匀介质中轴对称电磁波的反射阵和透射阵的递推公式．用这些阵可以计算交流电测并响应，包括感应测并和深探测电磁波传播测井（ＤＰＴ）．同时还给出了幅度基函数和斜度基函数，它们分别＂支撑＂起结点上函数的幅度和斜度．  相似文献   

再论波动方程反演波速问题——波的反射与透射公式     

黄光远  关华勇  刘小军 《CT理论与应用研究》1993,(3)

本文是文[1]的续篇,讨论由波动方程(?)Q/(?)t~2=v~2(x)△Q 反演波速v(x)的方法是否近似可用。作者指出,在非均匀介质条件下用此波动方程不能正确描述波的传播特性,因它不能保证弹性力在间断面上连续。以双层介质为例,分别从此方程及原始波动方程出发推导波的反射与透射公式,得到不同的反射系数与透射系数表达式。二者相差很大,不可能是近似关系,因此从波动方程直接反演波速函数的方法是不可取的。  相似文献   

A numerical study on 2-D compressive wave propagation in rock masses with a set of joints along the radial direction normal to the joints   总被引：1，自引：0，他引：1  

W.D. Lei  A.M. Hefny  S. Yan  J. Teng 《Computers and Geotechnics》2007,34(6):508-523

An explosion in a borehole or an accidental explosion in a tunnel will generate a two-dimensional (2-D) compressive wave that travels through the surrounding rock mass. For the problem of 2-D compressive wave propagation in a rock mass with parallel joints in the radial direction normal to the joints, parametric studies on the transmission ratio and the maximum rebound ratio are performed in universal distinct element code. The variation of the transmission ratio with the ratio of joint spacing to wavelength is generalized into a characteristic curve, which can be used as a prediction model for estimating the transmission ratio. The relationship between the maximum rebound ratio and the influence factors is obtained in charts. The charts can be used as a prediction model for estimating the maximum rebound ratio. The proposed prediction models for estimating the transmission ratio and the maximum rebound ratio are applied to a field explosion test, Mandai test in Singapore. The minimum possible values of peak particle velocity (PPV) at the monitoring points are estimated by using the proposed prediction model for estimating the transmission ratio along the radial direction normal to the joints. On the other hand, the maximum possible values of PPV are estimated by using the proposed prediction model for estimating the maximum rebound ratio along the same radial direction. The comparison shows a good agreement between the field-recorded PPVs and the estimated range of PPVs given by the minimum possible PPVs and the maximum possible PPVs at the monitoring points in Mandai test. The good agreement between the estimated and field-recorded values validates the proposed prediction models for estimating peak particle velocity in a rock mass with a set of joints due to application of a compressive wave at the boundary of a tunnel or a borehole.  相似文献   

Shear waves at a corrugated interface between anisotropic elastic and visco-elastic solid half-spaces     

S. K. Tomar  Jatinder Kaur 《Journal of Seismology》2007,11(3):235-258

Rayleigh’s method of approximation is employed to find out the reflection and transmission coefficients due to an incident plane SH wave at a corrugated interface between a laterally and vertically inhomogeneous anisotropic elastic solid half-space and a laterally and vertically inhomogeneous isotropic visco-elastic solid half-space. The lateral and vertical inhomogeneities are described by the exponential variations of elastic parameters. The formulae of reflection and transmission coefficients are derived in closed form for the first-order approximation of the corrugation. The effects of the corrugation of the interface, the inhomogeneity, the anisotropy, the visco-elasticity and the frequency of the incident wave on these coefficients are studied analytically and numerically for a specific model containing a periodic interface. The results of earlier workers have been reduced as particular cases from the present formulation.  相似文献   

Java多线程及多点连接技术在WebGIS数据传输中的应用     

Peng Zhuangzhi Yu Xin School of Remote Sensing  Information Engineering  Wuhan University  Luoyu Road  Wuhan  China 《测绘科技情报》2007,(1)

目前空间数据的传输效率低下已成为制约WebGIS发展的主要瓶颈之一。多线程技术以及多点连接在提高系统吞吐率、有效利用系统资源、改善用户任务之间的通信效率等方面有着显著作用。本文采用地图分层和图面分割的方法以及Java多线程和多点连接技术实现了WebGIS空间数据的高效传输。  相似文献