水热综合作用下钙芒硝盐岩强度等参数的衰减规律研究

为了研究钙芒硝盐岩在水热综合作用下强度等参数的衰减规律,通过自行研制的实验装置,模拟了钙芒硝盐岩在30～70℃温度的蒸馏水中的浸泡实验。在浸泡40 d过程中,测试了钙芒硝盐岩的单轴抗压强度、弹性模量、纵波波速、破坏模式等参数,总结了浸水前后钙芒硝盐岩参数随时间、温度的变化规律;通过偏光显微镜对比观察了在浸泡前后钙芒硝盐岩微观结构的变化特征;分析了成分、结构、时间、温度等因素对钙芒硝盐岩强度等参数衰减的影响。研究结果表明：(1)钙芒硝盐岩强度随浸泡时间的增加衰减剧烈。浸泡7 d后,钙芒硝盐岩强度衰减为初始强度的50%～72%。浸泡30～40 d后,钙芒硝盐岩强度衰减至初始强度的10%以下。(2)钙芒硝盐岩在长时间的浸泡过程中,主要是其中的可溶成分的溶解、溶蚀作用导致了钙芒硝盐岩结构的劣化。(3)在实验温度(30～70℃)范围内,钙芒硝等矿物的溶解过程大致经历了溶解度先增大后减小的过程,钙芒硝盐岩强度存在先减小后增大的变化,但在相同浸泡时间下各浸泡温度间强度差值小于初始强度的10%,钙芒硝盐岩强度随浸泡温度(30～70℃)变化不大。论文研究成果深化了盐渍岩土,尤其是钙芒硝盐岩水岩相互作用的...     

World Stress Map Database as a Resource for Rock Mechanics and Rock Engineering

Knowledge of the in situ stress state is of key importance for rock engineering. We inform the reader about the World Stress Map (WSM) database and its application to rock mechanics and rock engineering purpose, and in particular the orientation of maximum horizontal stress. We discuss the WSM and the quality ranking system of stress orientation data. We show one example of discrete-measured and computed-smoothed stress orientations from central and northern Europe with respect to relative plate velocity trajectories. We give first insights into ongoing development of a second, more Quantitative World Stress Map database which compiles globally rock-type specific stress magnitudes versus depth. We discuss the vertical stress component, and the lateral stress coefficient versus depth for different rock types. We display stress magnitudes in 2D and 3D stress space, and investigate stress ratios in relation to depth, lithology and tectonic faulting regime.     

岩体质量的分形表述

介绍了岩石质量评价的分形表述方法，研究表明，分维数Ｄ比ＲＱＤ更能客观地表现结构面呈不规则分布岩体的完整性特征，可直接用于工程岩体分类。     

西南地区某隧道围岩岩爆预测研究

岩爆预测一直是地下工程领域中的世界性难题。本文以西南某隧道工程为例,从岩爆形成的3个条件:岩石岩爆倾向性、岩体完整性和高地应力环境3个方面着手,应用最大储存弹性应变能指标Es和岩石脆性系数B,对深埋隧道区段内可能发生岩爆的石英砂岩、灰岩岩体进行岩爆倾向性分析预测; 基于地应力测量数据资料,采用地质过程动态模拟的有限元分析方法,反演分析隧道工程区岩体地应力场,对隧道高应力区段作出判断; 根据现场所取样品试验结果综合分析隧道围岩的物理力学性质、岩石单轴抗压强度等。在分析和总结前人岩爆预测预报方法的基础上,以工程地质分析为基础,详细阐明隧道岩爆发生的条件,并以岩体力学和非线性科学理论为指导,采用地质综合分析、应力强度比法对隧道可能发生岩爆的部位及其强度进行综合预测。     

柴达木盆地北缘滩间山群火山岩及形成环境

上奥陶统滩间山群以浅变质的中基性火山岩为主，均历经不同程度蚀变，选用相对稳定的高场强元素、稀土元素及Th、Y等研究火山岩原岩组成。岩石化学和微量元素判别标志指示火山岩形成于岛弧环境。     

Rock fall hazard along the railway corridor to Jerusalem,Israel, in the Soreq and Refaim valleys

We evaluate rock fall hazard along the railway corridor to Jerusalem, Israel, in the Soreq and Refaim valleys. For the purpose, we use a combination of historical information on past rock fall events, field surveys aided by the interpretation of aerial photographs, and numerical rock fall modeling. Historical information indicates that on July 11, 1927 an m _L 6.2 Dead-Sea transform earthquake caused rock falls in the studied area. The seismically induced rock falls damaged the railway tracks. Field observations revealed that the source area for the 1927 failures was located in the Aminadav formation, at the contact with the Moza formation. At the stratigraphic contact, rock blocks 10⁰–10¹ m³ in size are formed as a result of tensile stresses and associated fracturing in the dolomite of the Aminadav formation, combined with continuous creep of the blocks on the marl of the underlying Moza formation. We use topographical, geological, and geomorphological information to calibrate a three-dimensional numerical simulation of rock falls in the studied area. We use the results of the numerical modeling, and additional independent information, to assess rock fall hazard and the associated risk in the Soreq and Refaim valleys. Results indicate that in the studied area, rock fall risk to the railway line to Jerusalem is due primarily to Dead-Sea transform earthquakes, with m _L  > 6. We identify nine sections of the railway line where rock fall risk exists, for a total length of 2.5 km. We further note that seismically induced rock falls can produce damage to the road network in the studied area, make it difficult or impossible for earthquake casualties to reach hospitals in Jerusalem. We conclude offering recommendations on how to mitigate the risk posed by earthquake-induced rock falls in the studied area.     

石鼓群的划分及变质特征探讨

石鼓群位于云南西北部,面积约1 600km2,为甘孜一理塘板块的结晶基底.据现有资料,分为古元古代黎明岩群、中元古代新主岩群、新元古代巨甸岩群.黎明岩群为云母石英片岩、云母片岩,夹斜长片麻岩、斜长角闪岩.泥质岩石中具铁铝榴石、十字石、蓝晶石组合,基性岩中具铁铝榴石、普通角闪石组合,为中压低角闪岩相.黎明岩群后期抬升减压,叠加低压低角闪岩相变质,新生红柱石,部分原生蓝晶石退变成红柱石.于侵入其中的斜长角闪岩中获得Nd同位素模式年龄1 369.8Ma和1 343.8Ma,绿泥石英片岩中获得1 896.6Ma和2 161MaNd同位素模式年龄,故将黎明岩群时代置于古元古代.新主岩群分哈吉洛岩组和路西岩组,岩性为云母石英片岩、云母片岩、大理岩夹片麻岩及斜长角闪岩,部分岩石具糜棱岩化.哈吉洛岩组为低压低角闪岩相,具红柱石、十字石、铁铝榴石组合,路西岩组为高绿片岩相.于侵入新主岩群中的变质变形花岗质岩脉中获得锆石铅同位素年龄811 ±2Ma、820±1Ma、823±1Ma,故将新主岩群时代置于中元古代.巨甸岩群分陇巴岩组和塔城岩组,岩性为千枚岩、板岩,夹一层变质杏仁状玄武岩,为低绿片岩相.     

Quantifying weather conditions for rock fall hazard management

Relationships between weather conditions and rock fall occurrences have been acknowledged in the past, but seldom have such relationships been quantified and published. Rock falls are frequent hazards along transportation corridors through mountainous terrain, and predicting hazardous rock fall periods based on weather conditions can enhance mitigation approaches. We investigate the relationship between weather conditions and rock fall occurrences along a railway section through the Canadian Cordillera. Monthly weather-rock fall trends suggest that the seasonal variation in rock fall frequency is associated with cycles of freezing and thawing during the winter months. The intensity of precipitation and freeze–thaw cycles for different time-windows was then compared against recorded rock falls on a case-by-case approach. We found that periods when 90% of rock falls occurred could be predicted by the 3-day antecedent precipitation and freeze–thaw cycles. Some rock falls not predicted by this 3-day antecedent approach occurred during the first two weeks of spring thaw. These findings are used to propose a rock fall hazard chart, based on readily available weather data, to aid railway operators in their decision-making regarding safe operations.     

基于黏弹塑性的云岭隧道软弱围岩参数反演与稳定性分析

软弱隧道围岩在工程实际和试验研究中都表现出较强的流变性质, 容易造成围岩的过大变形而导致失稳.按新奥法施工原则对云岭隧道左洞进口段的软弱围岩段开挖过程进行监测, 分析初期围岩位移收敛值以及二次支护和衬砌的压力变化情况, 通过黏弹性有限元反分析理论, 建立基于黏弹塑性的反分析体系, 对围岩参数进行反演和优化.通过采用ANSYS有限元程序模拟开挖过程, 并将现场实际量测值与计算数据进行比较, 为隧道支护设计和施工的安全可靠性提供科学依据和技术指导.      

金属矿开采节理演化诱发覆岩变形失稳机制研究

金属矿开采诱发覆岩变形是一个复杂的力学问题,在工程活动的扰动下,采空区围岩的原始应力状态将被打破,引起覆岩的应力重分布,从而达到新的应力平衡状态。当覆岩中存在一些软弱结构面时,这些软弱结构面将不断地发展、演化,并可能出现贯通,其对覆岩的变形和破坏具有明显的影响。针对节理条件这一变量,采用Udec二维离散元模型,分析了双岩桥模型和四岩桥模型中各岩桥破裂特征及机制,并对比了两组模型中顶板应力释放规律及特点。采用3组对比模型实验,分析了0°/90°,45°/45°,20°/70°节理条件下岩移特点及变形机制。基于数值模型,对镜儿泉矿区实际节理条件下的地表变形特征和沉陷范围进行了研究,模型结果与地表变形GPS监测结果具有很好的一致性。     

磁测成果圈定半坡镁铁岩体及推断深部形态

半坡地区地面高精度磁测成果发现正磁异常与镁铁—超镁铁岩体的关系比较密切。随即开展△T异常圈定镁铁—超镁铁岩体范围,推断岩体的大大致形态,为在岩体中寻找岩浆岩型镍铜铂钯矿提供深部岩体形态资料。     

准噶尔盆地西北缘石炭系火山岩岩性岩相特征与裂缝分布关系

新疆准噶尔盆地西北缘大范围发育石炭系火山岩-沉积岩序列的交互式地层,剖面垂向层序由若干个火山喷发岩-沉积岩序列所组成。以克拉玛依油田六、七、九区石炭系火山岩-沉积岩为例,利用地震、钻井、岩心、电性实测资料,尝试性地提出了准噶尔盆地西北缘石炭系内幕地层划分方案,并从火山岩-沉积岩期次的划分、各期次火山岩-沉积岩岩相分布模式的建立、不同岩性裂缝发育程度定量描述的角度出发,详细论述各期次岩性、岩相、裂缝与油气藏形成的相关性,明确了六、七、九区石炭系裂缝发育区,为该区后续的勘探、开发部署提供科学依据。     

岩体结构变形破坏的内在驱动力-不平衡力

岩体结构的变形破坏是一个渐近过程,常规的强度设计与极限分析均无法描述这一过程。在回顾总结岩体结构破坏控制、变形控制的基础上,提出岩体结构变形破坏控制最终要落实到开裂控制上来。总结了岩体结构开裂计算的特点和难点,阐明了用不平衡力描述岩体结构变形破坏过程的理论依据。分别从单轴压缩试验、边坡开挖卸荷、拱坝坝踵坝趾开裂等3个具体的数值案例论证不平衡力与开裂破坏的内在相关性。提出了蓄水导致不可逆的谷幅变形也是不平衡力作用结果:裂隙水压力使屈服面收缩、原先处于屈服或临界屈服状态的岩体应力状态超出屈服面,产生不平衡力和不可逆的塑性变形。指出了不平衡力本质是岩体结构非平衡态到平衡态的距离,岩体结构非平衡演化的总体趋势服从最小塑性余能原理,进一步指出了无法消除的不平衡力是岩体结构变形破坏的内在驱动力。不平衡力不仅可以作为岩体结构变形破坏的判据,还能给出相应的加固措施,具有重要的工程意义。     

循环冻融条件下岩石物理特性的试验研究

新鲜岩石和风化岩石的力学性质有着较大的区别,特别是当岩石的风化程度很深时,岩石的力学性质会明显下降,而在实际工程中又常常将风化岩石作为工程的基础,因此,研究和认识风化岩石的力学特性是有必要的.温度的变化是引起岩石风化的主要原因之一,尤其是循环温度变化更容易使岩石风化.将采自焦作的大理岩和砂岩分成干燥和饱和两组岩样,进行了循环冻融试验来模拟岩石的风化.在冻融前、每10次循环冻融后,量测岩样的质量,利用NM-4B非金属超声检测分析仪对各岩样进行超声纵波无损检测,总共进行50次循环冻融.分析了循环冻融对岩石质量损失的影响并就纵波波速的改变进行了比较,据此归纳出岩石材料受风化影响的物理特性.     

岩石蠕变的应力-应变比分析

对岩石蠕变的应力-应变比分析方法进行了探索。蠕变是岩石重要的力学性质之一。岩石在各个应力水平下的蠕变曲线具有几何相似性。根据岩石蠕变的应力-应变比曲线可以近一步分析得到等时模量曲线。在岩石蠕变本构描述十分复杂、至今没有成熟的理论的情况下,应力-应变比分析方法具有十分重要的现实意义。     

藏东竹瓦根花岗岩成因、演化及成矿专属性

初步查明测区侵入岩时空分布特点及形成构造环境。解析德母拉岩带、阿扎贡拉岩带,按花岗岩类的成分和结构演化序列,将测区花岗岩划分为三缅村、竹瓦根2个序列及7个单元,归于侏罗纪、白垩纪两大岩浆活动期。     

Application of the adaptive neuro-fuzzy inference system for prediction of a rock engineering classification system

The rock engineering classification system is based on six parameters defined by Bieniawski [5], who employed parallel sets of linguistic and numerical criteria that were acknowledged to influence the behaviour of rock masses and the stability of rock structures. Consequently, experts frequently relate rock joints and discontinuities as well as ground water conditions in linguistic terms, with rough calculations. Recently, intelligence system approaches such as artificial neural network (ANN) and neuro-fuzzy methods have been used successfully for time series modelling. Using neuro-fuzzy approaches, which enable the information that is stored in trained networks to be expressed in the form of a fuzzy rule base, would help to overcome this issue. This paper presents the results of a study of the application of neuro-fuzzy methods to predict rock mass rating. We note that the proposed weights technique was applied in this process. We show that neuro-fuzzy methods give better predictions than conventional modelling approaches.     

Simulating damage evolution and fracture propagation in sandstone containing a preexisting 3-D surface flaw under uniaxial compression

Preexisting flaws and rock heterogeneity have important ramifications on the process of rock fracturing and on rock stability in many applications. Therefore, there is great interest in numerical modelling of rock fracture and the underlying mechanisms. We simulated damage evolution and fracture propagation in sandstone specimens containing a preexisting 3-D surface flaw under uniaxial compression. We applied the linear elastic damage model based on the unified strength theory following the rock failure process analysis code. However, in contrast to the rock failure process analysis code, we used the finite element method with tetrahedron elements on unstructured meshes. It provided higher geometrical flexibility and allowed for a more accurate representation of the disk-shaped flaw with various flaw depths, angles, and lengths through locally adapted meshes. The rock heterogeneity was modelled by sampling the initial local Young's modulus from a Weibull distribution over a cubic grid. The values were then interpolated to the computational finite element method mesh. This method introduced an additional length scale for the rock heterogeneity represented by the cell size in the sampling grid. The generation of three typical surface cracking patterns, called wing cracks, anti-wing cracks, and far-field cracks, were identified in the simulation results. These depend on the geometry of the preexisting surface flaw. The simulated fracture propagation, coalescence types, and failure modes for the specimens with preexisting surface flaw show good agreement with recent experimental studies.     

Constitutive model for soft rocks considering structural healing and decay

The behavior of soft rock depends on the contact area between mineral particles and the tensile strength of the interparticle cementation, which are usually referred to as structures. We investigated the effects of structural decay and healing on the behavior of soft rock through monotonic and slide-hold-slide triaxial tests under the drained condition with constant effective confining pressure. We developed a constitutive model for soft rocks incorporating structural healing and decay in the context of the extended critical state theory. The model was validated via laboratory tests and captured the behavior of soft rock, including the healing and decay phenomena.     

An analytical elucidation of the influence of surfactant on rock drilling by shear/drag bit

Summary We explain analytically the effects of surfactants on the enhancement of drilling rates in rock. We propose that the weakening effect is not simply due to the chemical action of the surfactant, as suggested by Rebinder in the 1930's but to a combination of mechanical and chemical interactions. We apply a fracture mechanics approach to elucidate surfactant-assisted drilling. An analysis of the chip formation process during rock cutting by a shear/drag bit has shown that the surfactant-induced damage zone develops in rock primarily in front of the individual bit, and its size can be as much as twice the thickness of the removed chips. This analysis allows us to estimate the influence of surfactants on cutting forces.