End Bearing Capacity of Drilled Shafts in Sand: A Numerical Approach

In this paper, a modeling procedure is carried out to numerically analyze the end bearing capacity of drilled shafts in sand. The Mohr–Coulomb elastic plastic constitutive law with stress dependent elastic parameters is used for all numerical analyses performed in this study. The numerical results are compared with the available experimental equations. It is seen that numerical results are in good agreement with experimental equations. The variation of the end bearing capacity of drilled shafts versus embedment depth is also studied. Numerical results show that with increase in pile embedment depth, the end bearing capacity increases. However, the rate of increase becomes smaller as the pile embedment depth increases. Also, numerical analyses show that, for equal settlement, the end bearing decreases with increase in the pile diameter. Finally, a sensitivity analysis is performed to obtain the separate effect of each sand parameter on the end bearing capacity of drilled shafts, and the parameters that are most influential are identified.     

极软质岩石中嵌岩桩的单桩承载力探讨

通过对极软质岩石地基进行现场原位测试，以及对极软质岩石地层中嵌岩桩的承载力计算，就如何根据现场原位静载试验确定极软质岩层的极限端阻力标准值的问题进行了研究，进而确定了桩端总极限端阻力标准值的计算方法，并提出了极软质岩石地基中基桩的设计方法及承载力的取定意见。     

浅变质细碎屑岩中韧性剪切变形构造岩特征及其类型划分

作者首次研究了浅变质细碎屑岩中韧性剪切带变形构造岩的特征,并进行构造岩类型划分;同时,对该类型构造岩与典型长英质糜棱岩的特征进行了对比分析;而后在构造岩岩石组构及综合研究基础上提出：这种构造岩的变形机制以粒间滑动为主,伴有细粒化,它们成生于地壳５—８ｋｍ的较浅层位和较低的温度、压力条件下。     

Hydraulic Characteristics of Rough Fractures in Linear Flow under Normal and Shear Load

Summary A hydro-mechanical testing system, which is capable of measuring both the flow rates and the normal and shear displacement of a rock fracture, was built to investigate the hydraulic behaviour of rough tension fractures. Laboratory hydraulic tests in linear flow were conducted on rough rock fractures, artificially created using a splitter under various normal and shear loading. Prior to the tests, aperture distributions were determined by measuring the topography of upper and lower fracture surfaces using a laser profilometer. Experimental variograms of the initial aperture distributions were classified into four groups of geostatistical model, though the overall experimental variograms could be well fitted to the exponential model. The permeability of the rough rock fractures decayed exponentially with respect to the normal stress increase up to 5 MPa. Hydraulic behaviours during monotonic shear loading were significantly affected by the dilation occurring until the shear stress reached the peak strength. With the further dilation, the permeability of the rough fracture specimens increased more. However, beyond shear displacement of about 7 to 8 mm, permeability gradually reached a maximum threshold value. The combined effects of both asperity degradation and gouge production, which prohibited the subsequent enlargement of mean fracture aperture, mainly caused this phenomenon. Permeability changes during cyclic shear loading showed somewhat irregular variations, especially after the first shear loading cycle, due to the complex interaction from asperity degradations and production of gouge materials. The relation between hydraulic and mechanical apertures was analyzed to investigate the valid range of mechanical apertures to be applied to the cubic law. Received June 12, 2001; accepted February 26, 2002 Published online September 2, 2002     

The Strain Ellipsoid and Shear Planes in Rocks

正 In discussing the origin and trend of certain types of fault,joint,cleavageand other fractures,and in petrofabric analysis it has been a common practicesince the time of G.F.Becker[1],to refer to the so-called strain-ellipsoid.But it is questionable whether those references are always made with a     

关于韧性剪切带中构造岩鉴定的讨论

从事岩矿鉴定近三十年,感觉最难鉴定的莫过于韧性剪切带中的构造岩。韧性剪切带是深部地壳中的一个构造薄弱带,产于定向压力环境中,产于该带的代表性岩石有构造片岩、糜棱岩、构造片麻岩,这三类岩石既有共性,又有个性,连续过渡递进变形而形成一系列特有的显微构造,且矿物组合也随着温压及流体等条件而产生规律性的变化,把制备好的样品通过偏光显微镜能呈现出诸多特有的显微现象,由此可以引领专业的岩矿鉴定者作出正确的判断,从而更好的服务于区域地质调查及找矿工作。本文将引用相关理论结合实际工作经验就有关岩石的显微特征作一个粗略规纳总结。     

火山岩中囊状体的特征及其鉴别

熔岩和火山碎屑岩是两类最主要的火山岩,分别代表了两种不同的火山喷发方式和成岩过程,是火山岩分类命名中首先要注意区分的。囊状体具有与浆屑很相似的形态和结构,但对其研究还相当不足,易导致富含囊状体的流纹质—英安质熔岩与富含浆屑的熔结凝灰岩相混淆,产生熔岩与火山碎屑岩分类上的错误。本文首次介绍囊状体的基本特征并分析其与浆屑之区别。囊状体由矿物集合体(结晶内带)和外围脱玻体(脱玻外带)构成,因形态总体似囊状而得名,可呈条带状、透镜状,两端呈撕裂状或须状等,有时也呈斑块状消光和脱玻褪色体;它们是火山岩中微小的高温气相或液相长英质组份结晶、并释热诱发周围玻璃质脱玻形成的一种原生岩石结构。正确区分囊状体和浆屑对火山岩的分类命名及成因研究有重要作用,并避免火山碎屑岩的人为扩大化。     

桩的荷载传递机理分析

荷载传递函数法是桩荷载传递机理分析的重要方法之一。针对桩－土共同作用过程中的桩周土体分别处于弹性与塑性状态的划分,以天然地基抗剪强度随深度线性增长的规律,由荷载传递函数的基本微分方程解得荷载传递的解析表达式,并以实例说明这种分析思路的实用性。     

华南海岸沙丘岩的特征及其与海滩岩的区别

沙丘岩是热带亚热带的一种特殊的岩石类型，尽管外貌相似，但它们成因和特征上有别于海滩岩。作者通过对西沙石岛、海南岛文昌和临高、广东阳江青洲岛、汕头广澳等处具一定代表性的沙丘岩的研究，总结了沙丘岩的沉积学、岩石学特征及其与海滩岩的区别。华南沙丘岩由岛屿上的灰砂和含生物碎屑的海岸风成沙丘物质胶结而成。分布高程可达＋６０ｍ以上，岩石中发育板状交错层理、大型槽状交错层理、上凸层理、似水平层理以及根管构造；其物质来源与海滩砂具继承关系，兼具风成砂的特点，部分沙丘岩还混有坡积物及陆生生物壳体。沙丘岩的颗粒多为中砂粒径，普遍分选好，（ＳＫ１）偏度变化比较大，ＫＧ峰度较小，Ｙ１值为负值，与海滩砂、海滩岩差别较大。沙丘岩中发育各种淡水渗流环境中特有的胶结物和胶结组构。虽然沙丘岩与现代海滩岩相比，其Ｃａ、Ｍｇ、Ｓｒ元素的含量及比例不同，但可以完全与上升海滩岩相似。本文作者认为:辨别沙丘岩主要从产状、沉积构造、粒度分析、胶结物及组构诸方面进行研究。     

香港岩石的硬度与点荷载指标和强度的关系

无损硬度测试——施密特锤及肖氏硬度实验和点荷载试验是三种经常用来间接测定岩石强度指标的方法。目前很多学者已提出了不同的经验关系,这些关系主要是把硬度指标、点荷载指标和单轴抗压强度、单轴抗拉强度与间接拉伸强度联系起来。但是在应用这些关系时,必须首先用当地的岩石特性数据加以验证,查看地质变化的影响,才可确保使用无误。本文的主要目的是根据大量香港岩石（包括花岗岩、石灰岩、大理岩和凝灰岩）的实验数据,提出一套适用于香港地区岩石的经验关系,另外也对其他经验关系作了考证。     

Trace Elements Characteristics of Rocks in Nuri, Tibet

Please refer to the attachment(s) for more details     

辽宁西部中生代火山岩的基本特征

辽西中生代火山岩主要分布于燕辽台褶带,由兴隆沟、兰旗和义县旋回构成。火山岩的岩石化学特征为SiO_2平均60.2%、富Na_2O、介于钙碱性和弱碱性系列之间。稀土总量低,铕的负异常弱,Isr在0.70546—0.70653之间。其特征与源区基底太古代建平群变质岩十分相似,反映了它们之间的成因联系。将太古代建平群变质岩和亏损地幔作为端员组分,由G.Faure二元混合模拟公式求得辽西中生代火山岩由65.8%—82.1%的源区物质——建平群变质岩和34.2%—7.9%的亏损地幔混合组成,表明辽西中生代火山岩主要是由源区物质——晚太古代建平群变质岩经部分熔融后形成的,成因上属于典型的不成熟地壳重熔类型。     

福建上杭-尤溪地区岩浆岩的分形特征

分形不仅能揭示地质现象的复杂程度,且在某种程度上反映了地质过程的成因本质。上杭－尤溪地区的分形研究表明：①侵入岩的分形值普遍较小,火山岩的分形值普遍较大;②火山岩的分形值与应力成正相关,而侵入岩则相反;③分形值受区内大型的政和－大埔断裂、上杭－云霄断裂、永安－晋江断裂控制;④火山岩的分形值接近于临界值时对成矿有利。     

Trace Elements Characteristics of Rocks in Chengba, Tibet

Please refer to the attachment(s) for more details     

水泥粉喷桩荷载传递规律的试验研究

通过水泥粉喷桩的现场足尺试验,测试了极体的应力-应变关系,推算出极侧摩阻力、轴力变化曲线。结果表明,荷载沿桩身的传递有一定范围,桩体的变形、应力、侧摩阻力主要集中在临界桩长范围内,而各量变化梯度在浅部较大。桩侧摩阻力的发挥与极土相对位移有关。桩体破坏也发生在浅层,破坏形式为环向拉裂和桩体横向压碎。     

大王北洼陷烃源岩有机地球化学特征

根据烃源岩可溶抽提物的色谱和色谱- 质谱分析结果,对大王北洼陷沙四段、沙三段和沙一段烃源岩的饱和烃和芳烃生物标志化合物组合特征进行了对比研究,揭示了三套烃源岩在沉积环境和有机母源输入的不同特征,总结了应用生物标志化合物鉴别三套烃源岩的组合参数特征,为精细的油源对比奠定了基础。研究表明,沙四段烃源岩具有较低的Pr /Ph,4-甲基甾烷同类物中C28 4-甲基系列含量最低、较高的甲藻甾烷含量、较低的重排甾烷含量、异常的C35 升藿烷含量、高伽马蜡烷异常指数、含一定量的奥利烷和较高的硫芴系列化合物含量等特征,反映了沙四段烃源岩形成于高盐度含硫强还原沉积环境,低等水生生物为主,高等植物有明显贡献的混合母源特征。沙三段烃源岩具有较高的Pr /Ph,4-甲基甾烷同类物中C29 4-甲基系列含量最低、几乎不含甲藻甾烷、较高的重排甾烷含量、基本正常的升藿烷分布、低伽马蜡烷异常指数和较低的奥利烷含量等特征,反映了沙三段烃源岩形成于半咸水的一般还原环境,低等水生生物为主,有一定量高等植物有机输入的混合母源特征。沙一段烃源岩具有极低的Pr /Ph,4-甲基甾烷同类物中C28 4-甲基系列含量最低、较高的甲藻甾烷含量、很低的重排甾烷含量、异常的C33 升藿烷含量、高伽马蜡烷异常指数、极低的奥利烷含量和较高的脱羟基维生素E 含量等特征,反映了沙一段烃源岩形成于高盐度强还原沉积环境,低等水生生物占绝对优势的有机母源特征。对研究区烃源岩生物标志化合物成熟度参数随深度的变化进行了分析,结果表明在不同层系中成熟度参数的演化存在显著差异,沉积埋藏历史和沉积环境可能是导致这些差异的原因,为此在应用这些参数进行烃源岩乃至生成石油的成熟度评价时,应使用不同的标准。     

Mechanical Properties and Deformation and Failure Characteristics of Surrounding Rocks of Tunnels Excavated in Soft Rocks

As soft rocks are likely to soften, slime and swell while contacting water, the existence of soft rocks is harmful for stability of surrounding rocks and supporting structures of tunnels. Through uniaxial and triaxial tests under dry condition and triaxial test with different moisture contents, the mechanical properties and failure modes of soft rocks were studied under conditions that the schistosity plane of the rock samples was vertical to, presented an oblique angle with, and paralleled to the loading direction. The results showed that peak strengths in natural and water-bearing states increased with increasing confining pressures, while those in water-bearing state were 40% lower than those in natural state. The samples were mainly subjected to ductile failure in both natural and water-bearing states while the samples in natural state exhibited a certain brittle failure characteristic in post-peak phase. With the increase of confining pressures, the post-peak curve gradually became gentle after certain brittle failure while the post-peak stresses had an insignificant change. In comparison, the samples in water-bearing state showed significant post-peak disparity, that is, exhibited strong ductile failure characteristic. Moreover, the fitting relationship between triaxial compressive strength and moisture of soft rocks can be expresses as σ ₁ = Aω + B (A < 0, B > 0) while that between elasticity modulus and moisture can be expresses as E = Aω + B (A < 0, B > 0).     

岩石剪切破裂中的“Riedel Shear”构造模式

岩石破裂中的“里德尔切变”(Riedel Shear),是地质构造研究中常见的违反岩石破裂准则理论的逆反现象。文中侧重从应力应变理论的角度讨论了这一构造模式形成的机理,并结合典型构造实例对其进行了系统分析。     

东营凹陷烃源岩轻烃特征

以1-己烯和1-壬烯为内标物质,采用低沸点溶剂密封抽提色谱分析技术,对东营有效烃源岩的轻烃进行了定量分析,在准确获取C1～C15组分质量分数的同时又能得到有重要信息的轻烃参数.分析表明岩石中的轻烃与可溶有机质(轻烃 沥青"A")的质量分数比值平均可达14.59%,并随演化程度的增强而增大;链烷烃和环烷烃质量分数比值与成熟度有很好的线性关系,当链烷烃与环烷烃质量分数比值等于1～2时为低熟阶段,当链烷烃与环烷烃质量分数比值等于2～6时为成熟阶段;证实了2,4-二甲基戊烷与2,3-二甲基戊烷质量分数比值的对数是温度的函数,利用相应的计算公式可获取源岩经历的最高埋藏温度.