基于点稳定系数法的斜坡稳定性分析

基于莫尔-库伦强度理论构架,界定了点稳定系数的概念,并推导其计算公式。利用Geostudio软件建立了均质斜坡模型及计算其应力分布,并在此基础上结合MATLAB软件计算斜坡模型中各点的点稳定系数,勾绘出斜坡体内不同稳定度区域,探析了斜坡稳定性,并与传统极限平衡法进行了对比。对比结果表明:对直立斜坡,两种方法的计算结果均为不稳定,但点稳定性系数法勾绘出坡脚及坡脚底部存在两处不稳定区域;对60°斜坡,点稳定系数法的计算结果表明坡脚处存在潜在不稳定区域,而极限平衡法的计算结果表明坡体处于稳定状态;对45°斜坡,两种方法的计算结果均为稳定,计算结果一致。进一步分析得到结论:点稳定系数法不需要假设或指定某一形状滑面进行斜坡稳定性评价,且可考虑应力集中对坡体稳定性的影响;极限平衡法以稳定系数表达计算结果,而点稳定系数法以不稳定区域表达计算结果。在分析了应力和岩土体力学参数因素对点稳定系数法计算结果的敏感性后发现:相对于极限平衡法,岩土体力学参数对点稳定系数法影响更为敏感,存在黏聚力界限点和内摩擦角界限点,且对均质斜坡破坏形式(局部滑动变形破坏或整体压缩变形破坏)起着非常重要的作用。     

Calibration of resistance factor for design of pile foundations considering feasibility robustness

The resistance factor for pile foundations in load and resistance factor design (LRFD) is traditionally calibrated considering target reliability index (β_T) and statistics of load and resistance bias factors. However, the resistance bias factor is hard to quantify statistically. Consequently, the design obtained using the calibrated resistance factor can still miss β_T if the variation in resistance bias factor has been underestimated. In this paper, we propose a new resistance factor calibration approach to address this dilemma by considering “feasibility robustness” of design in the calibration process. Herein, the feasibility robustness is defined as a probability that the β_T requirement can still be satisfied even in the presence of uncertainty or variation in the computed bearing capacity. For illustration, LRFD approach for pile foundations commonly used in Shanghai, China is examined. Emphasis is placed on re-calibration of resistance factors at various feasibility robustness levels, with due consideration of the variation in the resistance bias factor. A case study is presented to illustrate the use of the re-calibrated resistance factors. The results show that the feasibility robustness is gained at the expense of cost efficiency; in other words, the two objectives are conflicting. To aid in the design decision-making, an optimal feasibility robustness level and corresponding resistance factors are suggested in the absence of a designer’s preference.     

Parametric studies of disturbed rock slope stability based on finite element limit analysis methods

This study employs the finite element upper bound and lower bound limit analysis methods to investigate the stability of inhomogeneous rock slopes. The differences in the stability numbers of the upper and lower bound solutions are bracketed within ±10.5% or better, and the stability numbers obtained are presented in rock slope stability charts. These stability charts can provide a convenient tool for preliminary stability designs of inhomogeneous rock slopes. Various recommended blasting damage zones are considered, and disturbance factors are used to represent damage levels. Results showed that rock mass disturbance could significantly influence the evaluation of rock slope stability.     

Effect of non-linear soil deformation on the interaction among energy piles

This study investigates the effect of non-linear soil deformation on the displacement interaction among energy piles. The work is based on interaction factor analyses of full-scale pile group tests, whose results are compared with experimental evidence. The results presented highlight the tendency of interaction factor analyses that ignore non-linear soil deformation to overestimate the interaction and the displacement of energy pile groups. This outcome, in accordance with previous studies for conventional pile groups subjected to mechanical loads, may be considered in the analysis and design of energy pile groups subjected to thermal (and mechanical) loads through the interaction factor method.     

基于SRTM DEM的地形起伏度对天水市黄土滑坡的影响分析

以天水市辖区30 m分辨率的SRTM DEM数据为基础,首先利用GIS空间分析模块中邻域统计分析法,依次选取2×2、3×3、4×4、…、28×28、29×29、30×30共29个矩形邻域分析窗口,运用均值变点分析法进行最佳计算单元的计算分析。结果表明：12×12的网格大小（12.96×10⁴ m²）为曲线突变的拐点,作为曲线由陡变缓的阈值,确定12×12的网格大小（12.96×10⁴ m²）为研究区地形起伏度计算的最佳单元,生成研究区地形起伏度分级图。进而采用确定性系数法（CF）、证据权法、信息量法和条件概率法对研究区发育的黄土滑坡灾害与地形起伏度之间的相关关系进行了定量分析。研究结果表明,区内地形起伏度影响因子层中地形起伏度60~120 m的分级因子层为黄土滑坡灾害的易发因子层,而其中60~90 m区间的值最大,为黄土滑坡灾害的优势因子区间,对滑坡的响应最敏感。     

诸广中段中山地区铀矿床地质特征及找矿潜力分析

文章简要介绍了诸广中段中山地区的地质背景,认为其具有较好的铀成矿地质条件。区内铀矿体具有"三层楼"式的空间分布特征,主要成脉状、透镜体状产出。铀矿石类型主要为碎裂岩型、硅质角砾岩型及微晶石英脉型。通过对控矿因素的详细分析,认为铀矿化受地层、岩体及其内外接触带和构造的多重控制,但以构造控矿为主,蚀变对矿化具有一定的影响;铀矿化富集中心深部及外围尚有较大的找矿空间,具备较大的找矿潜力,有望进一步扩大铀资源规模。     

无人机航空伽马能谱数据处理中大气氡的修正

介绍了无人机航空伽马能谱数据处理中大气氡修正的一种方法——能谱比法的原理与方法、数据处理过程及其在无人机航空伽马能谱数据处理中的应用。使用该方法对喀什地区的无人机航空伽马能谱进行修正,修正后的航放U较好地反映了该区的地质情况,可以应用到生产实践中去。     

青海省达肯达坂山地区化探元素组合分区探讨

文章对青海省达肯达坂山地区1∶5万水系沉积物测量所得数据进行R型因子分析,提取了5种具有代表性的因子组合类型,对各因子元素组合得分归类,绘制了测区地球化学分区图。通过判读分析,地球化学分区图反映了不同地质体中以相应元素组合类型为主的地球化学异常。研究对比组合分区与因子得分异常,有利于推断相关元素的浓集部位,也为确定找矿靶区提供了方向。     

Research Progress and Development Tendency About Thermal Physical Properties of Rocks

The fundamental researches about thermal physical properties of rocks have much concern in oil and gas field. They go through four stages and are applied in thermal structure of lithosphere, thermal evolution of sedimentary basins, geotechnical engineering and geothermal area. This article summarized the current research progress on the basis of thermal physical properties of rocks and proposed the development of tendency for the future. Moreover, some cylindrical heat pipe, disc heat pipe, spherical heat pipe based on in-situ measurement method and prediction model based on mathematical statistics have been developed. The scholars discuss the internal relation between thermal conductivity parameter of rocks and other physical properties by a large number of experiments. The researches show that the thermal conductivity of rocks is affected by many factors, and the petrologic characteristic is the most important factor. The porosity of rocks, filled fluid properties, acoustic characteristics are also related to thermal conductivity, which is affected by temperature, pressure and anisotropy. In consideration of the study of thermal physical properties of rocks, we proposed the following tendency for the future. First of all, shale gas is regarded as a hot spot in oil-gas exploration and the formation mechanism and the formation of shale gas reservoir are under the control of thermal physical properties of shale gas, but the relationship among thermal conductivity and organic porous, organic carbon content, gas content, fractured characteristics remains unknown. Therefore, exploring the thermal physical properties of gas-bearing shale is an important research direction in oil and gas field. Secondly, the study of big data represents the general trend. Though the database of rocks thermal parameter is continually expanding, measuring in-situ thermal conductivity continuously in well is the best method to get the accurate in-situ thermal conductivity of rocks. Hence, the development of logging method principle and logging instruments based on thermal physical properties of rocks is a necessary trend for the future.