Rock Mechanical Characterization of an Argillaceous Host Rock of a Potential Radioactive Waste Repository

Summary The physical properties of foliated marls and shales from the Swiss Central Alps were investigated in the laboratory as part of the site characterization of a potential low and intermediate level radioactive waste repository. The rocks were first characterized by density, porosity and water content, then P-wave velocity measurements and uniaxial compression tests were conducted on samples oriented parallel, perpendicular and ∼45° inclined to the foliation. Correlations between P-wave velocities, Young's moduli, and uniaxial strengths and directional dependence of compressibility and permeability (determined at elevated hydrostatic pressures) revealed that two distinct families of microcracks cause the significant anisotropy. The pressure and time dependence of strength was then measured in triaxial compression, creep, and relaxation tests. In triaxial compression at room temperature, confining pressures up to 90 MPa and strain-rates as low as 10⁻⁸ s⁻¹ failure occured after small inelastic strains. Failure strength exhibits a strong pressure and a weak strain-rate dependence. The low friction coefficient of clay minerals appears to dominate the bulk frictional properties. Micromechanical modeling of triaxial compression, creep, and relaxation tests suggests that inelastic deformation is accommodated by subcritical crack growth.     

Influence of Water Content on Mechanical Properties of Improved Clayey Soil Using Steel Slag

The use of steel slag fines has been fully investigated and developed as it has similar chemical composition and mineralogy to that of Portland cement. Researchers from home and abroad have done lots of research on steel slag, such as its production, processing, properties, mechanical behavior, cementitious property and so on. This paper describes influence of water content on mechanical properties of improved clayey soil using steel slag and a series of tri-axial compression tests are carried out to study the influence of water content to the admixture of clayey soils and steel slag. Through the test data statistics and analysis, the basic rules of the mechanical properties of these mixed soils were gotten, especially, the optimum steel slag and water content. Through tri-axial compression tests, there are several kinds of specimen failure forms in different conditions of steel slag and water content. The stiffness of steel slag is larger than clayey soil, so the specimen with steel slag would break with an oblique angle whereas the clayey soil specimen would be compressed. Drawn from the experiment, while water content increases, cohesion c increases and internal friction angel φ decreases; however, in general, the maximum stress difference firstly increases, and then decreases. Under the same water content, with the curing period and steel slag content increase, cohesion c increases, internal friction angel φ decreases, however, the stress difference increases. By analyzing the specimen failure forms and the relations of stress difference and axial strain, the relations between stress difference max (σ₁ ? σ₃) and steel slag content and relations between the secant modulus E₅₀ and steel slag content are gotten. It is concluded that when the water content is about 18 % and steel slag content is about 30 %, the stress difference and secant modulus E₅₀ is larger than other cases. Therefore, in soft soil foundation treatment, such steel slag and water content could be chosen in order that the soil strength would be improved. So, judging from the results, the foundation settlement will be reduced by mixing appropriate steel slag and water content.     

Influences of Mineralogy and Water Content on the Mechanical Properties of Argillite

Callovo-Oxfordian (Cox) argillite was investigated in the context of feasibility studies for an underground repository for nuclear waste. In this study, the influence of mineralogical composition and water content on the mechanical properties of the Cox argillite was investigated. The samples were drilled from three representative depths at which the rock formations have different mineralogical compositions. Micro-indentation and mini-compression tests were performed on samples with different water contents. The elastic and failure properties of argillite were determined and were found to be related to the mineralogical composition and water content. Both the elastic modulus and strength decrease with increasing clay and water contents.     

利用自然伽马测井数据计算地层泥质含量

阐述了利用自然伽马测井数据,采用相对值法定量计算地层泥质含量的方法。用CorelDRAW绘图软件绘制泥质含量曲线。通过在研究区中的应用,证实了该方法的可靠性,为研究区地层泥质含量计算提供了可靠的依据。     

李家窑膨胀岩膨胀性能的试验研究

对山西万家寨引黄工程南干线某地的膨胀岩进行了室内物理化学性质测试、常规的膨胀率与膨胀力及非常规的三向膨胀与大比例尺膨胀试验,分析结果后得出了相应的结论     

Effect of Rapid Thermal Cooling on Mechanical Rock Properties

Laboratory tests have been conducted to investigate the effects of rapid thermal cooling on various rock specimens including igneous, sedimentary, and metamorphic rocks. At first, various types of thermal loading were conducted: heating up to 100, 200, and 300 °C, followed by rapid cooling with a fan. In addition, multiple cyclic thermal cooling (10, 15 and 20 cycles) with a maximum temperature of only 100 °C was conducted. Experiments included edge notched disc (END) tests to determine the Mode I fracture toughness, Brazilian disc tests to determine tensile strength, seismic tests to determine P-wave velocity, and porosity tests leading to meaningful results. Even though only small changes of temperature (rapid cooling from 100 °C to room temperature) were applied, the results showed that crack growth occurred in some rock types (granite, diabase with ore veins, and KVS) while crack healing occurred in other rock types (diabase without ore veins, quartzite, and skarn). To better understand the results, 3D transient thermo-mechanical analysis was conducted using the ANSYS program. The results indicated that there was a thin region near the outside of the specimen where large tensile stresses occur and microcracking would be expected, and that there was a large area in the middle of the specimen where lower magnitude compressive stresses occur and crack closure would be expected. It was found that the more heterogeneous and more coarse-grained rock types are more likely to exhibit crack growth, while less heterogeneous and more fine-grained rocks are more likely to exhibit crack healing.     

岩石破坏后的注浆固结体的力学性能

在破裂岩石残余强度和变形性能研究的基础上,进一步开展其注浆固结体的力学性能试验研究。试验证实注浆固结后破裂岩块残余强度有不同程度的提高,同时发现其侧向变形和径向变形趋向协调,从而提高了破裂岩块的塑性变形性能,并在较大变形范围内保持稳定的承载能力。试验结果有助于解释围岩注浆加固控制巷道变形的机理。     

Effects of Material Composition and Water Content on the Mechanical Properties of Landslide Deposits Triggered by the Wenchuan Earthquake

Abundant landslide deposits were triggered by the Wenchuan earthquake, providing a rich source of material for subsequent debris flows or slope failures under rainfall conditions. A good understanding of the physical and mechanical properties of the landslide deposits is very important to the research on slope failure mechanisms and the initiation of debris flow. Laboratory biaxial compression tests are used to study the material compositions and water content impacts on the mechanical properties of landslide deposits, and a discrete element method (a bond-contact model) is used to study the particle stiffness, bond force, friction coefficient and confining stress impact on the mechanical behaviors and the relationships between the numerical and experimental parameters. The experimental results show that the failure stress of landslide deposits is decreased with increasing content of fine particles and also with increased water content, especially at the initial increasing stage. Cohesion of the saturated landslide deposits is increased, but the friction angle is decreased with the increase in the fine particle content. Shear strength parameters (the cohesion and friction angle) are decreased with the increasing water content at the initial increasing stage, and then, they slowly decrease. There is a critical value of the water content at 5%–7% (in weight) for the failure stress and shear strength parameters of the landslide deposits. Quadratic equations are presented to describe the relation between the bond force and cohesion, and the numerical friction coefficient and the experimental friction angle.     

水对不同岩石声波速度影响的研究

通过分析不同成因类型岩石的声波速度,提出了水对不同岩石声波速度的影响,从岩石孔隙及隐微裂隙的发育程度及岩石的水理性质解释了在水的作用下岩石声波变化规律,利用这些规律可以初步判断岩石的隐微裂隙发育程度及水理性质。     

泥质岩有机质的赋存状态及其对泥质岩封盖能力的影响

应用荧光显微镜法,首次对济阳坳陷下第三系泥质岩中有机质的赋存状态进行了研究。下第三系泥质岩有机质的赋存状态可划分为顺层富集型、分散型和局部富集型等三种类型。有机质呈顺层富集型分布的泥质岩,其有机质丰度大多较高,主要沉积于半深湖-深湖相中。有机质呈分散型分布的泥质岩,其有机质丰度变化范围较大,大多形成在河流-三角洲相、滨-浅湖相或浊流沉积中。结合部分揭示泥质岩封盖能力的定量分析数据,下第三系泥质岩可概括出以下三种不同的组合特点:①泥质岩中有机质丰度高且有机质呈顺层富集型状态赋存时,泥质岩封盖能力差;② 泥质岩有机质丰度高且有机质呈分散型状态赋存时,泥质岩具有一定的封盖能力;③ 泥质岩有机质丰度低且有机质呈分散型状态赋存时,泥质岩封盖能力较好,因此,泥质岩中有机质的赋存状态对泥质岩的封盖能力有着不可忽视的影响。在研究评价泥质岩对油气藏的封盖能力时可作为重要的依据之一。     

月岩采样及其物理力学特性调研分析

月岩的存在形式和主要物理力学特性直接关系到月岩的可钻性,是取心钻具设计、钻进工艺确定及可靠取心的基本前提和重要依据。通过大量调研分析,认为:国外历次取心管样品中发现月岩以直径较大的岩石颗粒存在,比例为40%～80%,月岩在月球样品中的比重高达65%;月岩粒径分布广,且随着深度的增加粒径大小呈先减小后增大的趋势。月海玄武岩呈疏松状态,其主要物理力学范围为密度3.26～3.51 g/cm3,堆密度3.04～3.34 g/cm3,孔隙度0～10%,抗压强度约200 MPa,动态抗拉强度114～160 MPa。     

Application of Rock Mass Characterization for Determining the Mechanical Properties of Rock Mass: a Comparative Study

The results of geotechnical explorations, engineering geological investigation (including laboratory and in situ tests) and field observations have been used, along with borehole logging charts, to obtain the rock mass geotechnical data. Based on the data, the rock mass along the Sabzkuh water conveyance tunnel route was classified by rock mass rating (RMR), Q-system (Q), rock mass index (RMi) and geological strength index (GSI) (3 methods). A new series of correlations were established between the systems based on the data collected from the study area. These relationships were then compared with those reported in the literature, and two new relations were recommended. The classifications were utilized to calculate mechanical properties (rock mass strength and deformation modulus) of the rock mass along the tunnel according to available empirical relations, and to distinguish the upper-bound and lower-bound relations.     

泥质烃源岩密度分级分离与有机碳分配

选取东营凹陷第三系11 块泥质烃源岩样品,粉碎后按小于1.6 g/cm3,1.6~2.2 g/cm3 和大于2.2 g/cm3 的密度,分离成1,2,3 三个组分,希望可以把烃源岩中游离的有机质、无机矿物与有机黏土复合体分别提取出来。对各组分进行质量、有机碳及扫描电镜分析,探讨不同密度组分中有机质赋存形式及有机碳分配方式的差异性。密度分组后各组分的质量、有机碳量回收率基本上达到100%,表明密度分离方法可信,且对烃源岩的破坏较弱。通过扫描电镜观察发现,1 组分中存在大量的生物碎屑有机质,经盐酸处理后,有机质颗粒表面干净,而2,3 组分中只见有大量的矿物颗粒,但能谱分析显示了C 元素的存在。这些特征表明1 组分为生物碎屑有机质,而2,3 组分中有机质与无机矿物相混合。有机碳分析表明,1 组分有机碳含量平均高达14.24％,但其仅占全岩有机碳量的1.11%;2,3 组分中有机碳含量分别为3.26%,2.77%,两者占全岩有机碳量的90% 以上。由此看来与无机矿物相结合是烃源岩中有机质较为重要的赋存方式,这部分有机质对全岩生烃量的贡献不容忽视。     

Particle Flow Simulation of Anisotropic Mechanical Properties of Cracked Rock Mass

Geotechnical and Geological Engineering - In order to study the anisotropy caused by crack propagation and evolution of rock mass, a particle flow model reflecting the anisotropic mechanical...     

Influence of Pore Fluid Chemistry on the Mechanical Properties of Clay-Based Materials

The producers of nuclear waste, within all countries exploring options, including Canada, have determined the long-term solution to be a deep geological repository. In the Canadian concept, within the deep geologic repository a number of clay-based barriers will separate the containers from the surrounding geosphere. Following placement the surrounding groundwater will infiltrate into the repository. In order to analyze the performance of the repository under very complex conditions, accurate material properties are required. The chemistry of the host rock is an important aspect as the behaviour of clay-based barrier materials could be affected by the saturating saline groundwater. This paper investigates the saturated mechanical behaviour of light backfill (composed of 50 % silica sand and 50 % Na-bentonite clay) and dense backfill (composed of 70 % crushed granite, 25 % glacial lake clay and 5 % Na-bentonite clay) and the quantifying the effect of pore fluid chemistry on the strength and compressibility behaviour of the materials. The results indicate that light backfill behaviour is strongly influenced by its pore fluid chemistry while dense backfill shows limited effects. The material parameters of light backfill and dense backfill are interpreted for input into numerical simulations. These results and interpretation enrich the understanding of the mechanical response of light and dense backfill, two components of the sealing system of the Canadian deep geologic repository.     

Creep Properties of Altered Rock Subjected to Water Influx-Lost Cycles

Geotechnical and Geological Engineering - Creep properties of altered granite were changed due to water level rise and fall in the tailings ponds. In this paper, the effects of water influx-lost...     

泥岩有机质的赋存状态与油气初次运移的关系

从济阳坳陷古近系 新近系泥岩的研究实例出发,分析了泥岩孔隙结构特征及有机质的赋存状态,探讨了泥质烃源岩排烃通道与初次运移的关系模式。研究认为泥岩中孔隙小而多,喉道窄而细,孔喉分选性较好,具有较好的连通性,微裂 (隙 )缝常见。泥岩中有机质的赋存状态可划分为顺层富集型、分散型和局部富集型等三种不同的种类。泥岩中有机质呈分散型分布时,成熟油气通过较粗孔喉系统作为通道进行排烃是初次运移的方式之一。泥岩中有机质呈顺层富集型分布时,在有机质富集处,岩石结合力较弱,加上成熟油气形成的流体压力较高,极易产生微裂 (隙 )缝,成为成熟油气初次运移的主要通道。