深基坑复合喷锚支护技术探讨   总被引：3，自引：1，他引：3  

陈善雄  许锡昌  陈鹰  刘作 《岩土力学》2003,(Z2)

工程实践表明,复合喷锚支护是一种有效的深基坑支护型式,它可用于土层条件差、安全性要求高、变形控制严格的基坑工程中。复合支护中锚杆为主要受力构件,竖向花管为辅助受力构件,可起到限制、减小土体变形的作用。由于竖向注浆花管的加入,花管及注浆体抗剪作用加强,使基坑的整体稳定性得以大幅度提高。探讨了复合喷锚支护整体稳定性分析方法,建议将滑动区域分为加固土和原土两部分,将锚管注浆形成的注浆体等效为一层加固土,按喷锚支护模型计算复合喷锚支护整体稳定性。  相似文献   

Partial melting during tectonic exhumation of a granulite terrane: an example from the Larsemann Hills, East Antarctica   总被引：23，自引：0，他引：23  

C. J. CARSON  R. POWELL  C. J. L. WILSON  & P. H. G. M. DIRKS 《Journal of Metamorphic Geology》1997,15(1):105-126

Anatectic migmatites in medium- to low-pressure granulite facies metasediments exposed in the Larsemann Hills, East Antarctica, contain leucosomes with abundant quartz and plagioclase and minor interstitial K-feldspar, and assemblages of garnet–cordierite–spinel–ilmenite–sillimanite. Qualitative modelling in the system K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–O₂, in conjunction with various P–T calculations indicate that the high-grade retrograde evolution of the terrane was dominated by decompression from peak conditions of c. 7 kbar at c. 800 °C to 4–5 kbar at c. 750 °C. Extensive partial melting during decompression involved the replacement of biotite by the assemblage cordierite–garnet–spinel within the leucosomes. These leucosomes represent the site of partial melt generation, the cordierite–garnet–spinel–ilmenite assemblage representing the solid products and excess reactants from the melting reaction. The extraction and accumulation of this decompression-generated melt led to the formation of syntectonic pegmatites and extensive granitic plutons. Leucosome development and terrane decompression proceeded during crustal transpression, synchronous with upper crustal extension, during a progressive Early Palaeozoic collisional event. Subsequent retrograde evolution was characterized by cooling, as indicated by the growth of biotite replacing spinel and garnet, thin mantles of cordierite replacing spinel and quartz within metapelites, and garnet replacing orthopyroxene and hornblende within metabasites. P–T calculations on late mylonites indicate lower grade conditions of formation of c. 3.5 kbar at c. 650 °C, consistent with the development of late cooling textures.  相似文献   

Rapid cooling and exhumation of eclogitic rocks from the Great Caucasus, Russia   总被引：3，自引：0，他引：3  

A. PERCHUK  & P. PHILIPPOT 《Journal of Metamorphic Geology》1997,15(3):299-310

Diffusion modelling of growth-zoned garnet is used in combination with standard geothermometric and geobarometric techniques to estimate cooling and denudation rates from the mafic eclogites of the Red Cliff area, Great Caucasus, Russia. Euhedral garnet porphyroblasts exhibit different degrees of prograde growth zoning depending on the size of the grain (100 μm to several mm in diameter). Zoning patterns are mainly expressed in terms of Fe–Mg exchange, with 100*Mg/(Mg+Fe) increasing from 18–20 to 33–37 from core to rim. Geothermobarometry yields conditions of 680±40 °C and a minimum of 1.6±0.2 GPa and of 660±40 °C and 0.8±0.2 GPa for the high-pressure and retrograde stages of equilibration, respectively. A temperature of 600±40 °C has been recorded for the late-stage metamorphic overprint in the mica schists surrounding the eclogites. Relaxation of garnet zoning profiles was modelled for three different hypothetical P–T –t trajectories, all with an initial temperature of 680 °C and a pressure change of 0.8 GPa. The first two trajectories involve decompression associated with regular cooling down to 660 °C (near isothermal) and 600 °C. The third path is a two-step trajectory comprising near-isobaric cooling down to 600 °C followed by isothermal decompression to 0.8 GPa. These P–T trajectories cover as wide a range of pressure and temperature changes endured by the rocks as possible, thus representing extreme cases for calculating cooling and exhumation rates. Calculations indicate that the zoning pattern of the smallest garnet (i.e. garnet for which the zoning is most easily eliminated during post-growth processes) along the different paths can be preserved for the following average exhumation and cooling rates: path 1, 143 mm a^?1 and 102 °C Ma^?1; path 2, 60 mm a^?1 and 171 °C Ma^?1; path 3, 11–30 mm a^?1 and 200–400 °C Ma^?1. These results are discussed in light of theoretical P–T–t paths extracted from thermal models of regions of thickened crust, and from analogue models of accretionary wedge and continental lithosphere subduction.  相似文献   

潜水钻机在漂石和砂卵石漏浆地层中大口径钻孔工法探讨     

范孟彬 《水文地质工程地质》1997,24(4):54-54,57

本文重点介绍在漂石，砂卵石地层中进行大口径φ１．８ｍ桩基施工时，采用钻，抓成孔工艺的实例。  相似文献   

石龟山大桥直径3～4.4m空心桩施工技术          下载免费PDF全文

冯宗才  范清明  陆祖安 《探矿工程》1997,(1):21-24

施工φ３￣４．４ｍ空心桩，需要预制空心桩节和护筒，搭建水上平台，进而介绍了钻孔施工，桩节组拼以及压浆等工艺。与实心桩相比，空心桩显示了独特的优越性。  相似文献   

Three-dimensional Rayleigh hysteresis of oriented core samples from the German Continental Deep Drilling Program: susceptibility tensor, Rayleigh tensor, three-dimensional Rayleigh law   总被引：2，自引：0，他引：2  

H. Markert  A. Lehmann 《Geophysical Journal International》1996,127(1):201-214

Rayleigh hysteresis, as defined by the well-known Rayleigh relations, has been observed not only when magnetization of pyrrhotite-bearing KTB-samples is measured in parallel to a weak dc magnetic field, but also in experiments where field and measuring directions have been adjusted strictly perpendicularly to each other. Nine-tupels of independent Rayleigh hysteresis loops could thus be compiled. Their characteristic coefficients X ^ijk of initial susceptibility together with the Rayleigh loss coefficients α^jk have been proved to determine completely the samples' weak-field magnetic anisotropy. Interpreting the coefficient matrices ( X ^ijk) and (α^jk) as the tensor of initial susceptibility and the Rayleigh tensor, respectively, generalization of the isotropic Rayleigh relations in terms of corresponding tensor relationships has been suggested for the anisotropic case. Application to the KTB samples showed 3-D Rayleigh hysteresis measurements to be an excellent tool for rock magnetic analysis in terms of ore content and crystalline texture. In particular, a magnetocrystalline double texture of the basal planes of pyrrhotite precipitates and their [1120] directions of easy magnetization have been clearly detected. Surprisingly, the welt-known theorem α= const. X ²_I, formulated by Néel (1942) for the isotropic case, has been found to hold true even in tensor generalization (α_jk) = const ( X ²_jk). To reach sufficient resolution for the measurements performed, a sensitive vibrating coil magnetometer (VCM) has been developed.  相似文献   

X射线荧光测井井液的影响与校正     

葛良全  周四春  谢庭周  章晔  程业勋  侯胜利 《物探化探计算技术》1996,(S5)

X射线荧光测井中 ,井液位于井下探管与井壁之间 ,它的影响不但表现在对特征X射线的吸收 ,而且表现在对源初级射线和特征 X射线的散射。井液的校正采用硬件与软件相结合的方法 ,在硬件上 ,使含有探测器的部分制成单独的短臂 ,有效地保证了探测窗与井壁的良好接触 ;在软件上 ,提出的双散射峰法和散射峰 -逃逸峰法 ,能够校正 0 - 10 mm厚的井液对 X射线荧光测井结果的影响  相似文献   

MD－50型钻机液压系统的设计          下载免费PDF全文

于飞 《探矿工程》1996,(2):47-48

介绍了ＭＤ－５０型钻机液压系统的设计原理和主要液压元件的选择依据，并通过对设计和实践的总结，谈了作者在全液压钻机液压系统设计中的一些体会。  相似文献   

席状岩浆房中的岩浆冷却及动力稳定性   总被引：4，自引：0，他引：4  

张正阶  宋谢炎 《岩石学报》1996,12(1):1-16

关于岩浆房中岩浆的结晶分异方式一直存在着争议，其基本矛盾在于对岩浆冷却历史及热不稳定性可能引起的对流形式的理解各不相同。本文在充分考虑席状岩浆房的基本物理特征的基础上，建立了稳定岩浆体系的动态冷却模型，并以攀枝花层状岩体为例，计算了相应的温度场、密度场及粘度场。同时，提出了一种基于能量守恒的、对热不稳定性进行分析的新方法。计算了热不稳定性可能引起的对流强度、对流区域及对流时间，并深入讨论了在一定的热不稳定状态下，不同的岩浆屈服强度对对流特征参量的影响。结果表明，在该岩体的整个固化过程中，如果曾发生过自发对流，其对流也是极微弱而短暂的，不会影响中下部岩浆房中岩浆的固化和结晶。这一结论与对该岩体的实际观察相符。  相似文献   

流体在同心环状空间中流动时的压力损失     

张祝新  程晓新  夏圣强 《吉林大学学报(地球科学版)》1997,(2)

同心环状空间是工程上较常见到的流体流动空间，在此空间中流体流动情况的分析较复杂。工程上对其流动情况的分析常常是引用流体力学中的分析结果，但往往由于对环状空间结构的条件重视不够，引用时很容易出毛病。经过仔细推导分析，指出其应用条件，并有助于对同心环状空间中流体流动时压力损失的分析与计算  相似文献