Case-Based Reasoning for Slope Stability Evaluation and Its Application

Slope is a non-linear and uncertain kinetic system affected by many factors. In view of the incompleteness and uncertainty of the information of slope stability evaluation, a new method of slop stability evaluation by using case-based reasoning is presented. Considering the sensitivity of attribute weights to the environment, the algorithm of attribute weights is set up on the basis of the concept of changeable weights. Calculating the similarity between target case of the slope and base case, the stability of target case is evaluated. It is shown from examples that the method is simple, visual, practical, and convenient for use.

Opposition-Based Firefly Algorithm for Earth Slope Stability Evaluation

This paper introduces a new approach of firefly algorithm based on opposition-based learning （OBFA） to enhance the global search ability of the original algorithm. The new algorithm employs opposition based learning concept to generate initial population and also updating agents’ positions. The proposed OBFA is applied for minimization of the factor of safety and search for critical failure surface in slope stability analysis. The numerical experiments demonstrate the effectiveness and robustness of the new algorithm.

Source Range Estimation Based on Pulse Waveform Matching in a Slope Environment

An approach of source range estimation in an ocean environment with sloping bottom is presented. The approach is based on pulse waveform correlation matching between the received and simulated signals. An acoustic prop- agation experiment is carried out in a slope environment. The pulse signal is received by the vertical line array, and the depth structure can be obtained. For the experimental data, the depth structures of pulse waveforms are different, which depends on the source range. For a source with unknown range, the depth structure of pulse waveform can be first obtained from the experimental data. Next, the depth structures of pulse waveforms in dif- ferent ranges are numerically calculated. After the process of correlating the experimental and simulated signals, the range corresponding to the maximum value of the correlation coefficient is the estimated source range. For the explosive sources in the experiment with two depths, the mean relative errors of range estimation are both less than 7%.

干旱半干旱区岩质边坡生态基材防护特性与优化配比

为修复干旱半干旱区岩质边坡的生态系统,获得生态护坡基材的优化配比,以一种新型生态基材为研究对象,以黏结剂、木纤维、保水剂为3个因素,各取3个水平,开展多指标多因素正交试验探索各因素和水平对基材性能的影响规律。结果表明:黏结剂可以有效提升基材的强度和水稳性能,与适量水分作用可以发挥最优效能。随其掺量的增加,抗剪强度表现为先增加后减小,渗透系数和崩解量均表现为减小;施用较少剂量的保水剂即可对基材的渗透、持水性能产生较大的影响,有效提高基材固持自然降水的能力;木纤维与黏结剂的相互作用,可以促进其对基材的加筋补强和改善土壤构型效能的发挥,增强基材的抗冲抗剪性能。除渗透系数随木纤维掺量的增加而增加外,其他指标均呈先增大后减小的趋势。由极差分析可得,各因素对基材性能的影响程度表现为黏结剂>木纤维>保水剂,获得基材的最优配比为黏结剂3%,木纤维4%,保水剂0.1%,最优含水率为16%。

圆弧式地基合成孔径雷达在边坡变形监测中的应用

边坡变形监测是防止滑坡、崩塌、泥石流等地质灾害的有效途径之一。圆弧式地基合成孔径雷达是一种非接触式的新型地表形变监测设备,具有高分辨率、高频率、高精度、全方位、全天候实时监测等优点,更能有效地满足边坡变形监测的全面性和连续性要求。为了验证该设备在边坡变形监测中的效果和精度,本文采用两种便携圆弧式地基合成孔径雷达系统进行测试。测试结果表明,两种设备均能快速、全面地获得整个边坡的形变情况,具有较高的分辨率和亚毫米级的监测精度,且能实时发出预警,是一种全面高效的边坡变形监测手段。

基于FLAC/Slope模拟分析输电线路塔位边坡的开挖稳定性

塔位边坡的稳定性是输电线路基础设计考虑的一项重要内容。基于强度折减理论采用FLAC/Slope软件建立了输电线路典型塔位边坡的有限元分析模型,数值模拟了塔位边坡分步开挖施工过程,对各施工阶段的稳定性进行了评价分析,特别考虑了边坡稳定系数随边坡开挖步的变化规律。结果表明塔位边坡的坡脚或坡体分层处存在较大应力集中,且施工开挖步是影响边坡稳定系数变化的重要因素。

雨后不同时长基覆型边坡动力失稳破坏研究

基覆型边坡由于其上部为松散型堆积体,下部为基岩的特点,在降雨和地震作用下的失稳过程和破坏特征和其他边坡有较大不同,而降雨和地震作用的间隔时间会对二者耦合作用产生较大影响。利用自制的模型箱对基覆型边坡开展振动台模型试验,研究不同降雨停止时长对边坡稳定性的影响以及边坡降雨后静止不同时长在地震作用下的失稳特征和破坏模式。试验结果表明,降雨后间隔不同时间发生地震,边坡的破坏方式均呈过渡式破坏。在达到一定降雨强度后,降雨期间边坡含水率和孔隙水压力突增,而降雨停止后随着静止时长的增加,二者不断减小,之后达到稳定状态;随着静止时长的不断增加,基覆型边坡失稳临界加速度不断增加,大致和静止时长呈一个正相关的函数关系。

基于GB-SAR的矿山边坡局部变形演化与失稳预测

为了提高地基合成孔径雷达(ground-based synthetic aperture radar, GB-SAR)边坡监测效果与失稳预测能力,在广东省某石灰石矿山架设地基雷达,开展实地监测试验,结合矿山地质条件与监测数据研究不同类型的岩体变形演化特征,根据变形特征选择位移最大点的监测数据利用速度倒数法进行失稳预测。通过分析典型案例的监测数据来优化速度倒数法的算法,进而对矿山试验数据进行研究。研究结果表明:通过分析雷达三维模型变形图的局部位移差异,能够初步判断边坡岩体的变形破坏方式;适当增大移动平均滤波法的移动时间周期C,能够更早地发现灾害征兆,更好地识别岩体加速变形阶段及临滑阶段。研究结果可为基于雷达的滑坡预测提供参考。

基于多项式有限混合模型的Slope One算法改进

针对多项式有限混合模型参数估计过程中存在的初始化依赖、参数易收敛到边界值以及容易陷入局部最优等问题,引入了最小信息长度准则,优化多项式有限混合模型的参数估计过程。在此基础上,采用基于多项式有限混合模型的聚类算法对用户评分行为进行聚类,利用模型求解得到的聚类归属概率对Slope One算法实施改进。实验结果表明:应用最小信息长度准则对多项式有限混合模型进行优化后,聚类效果明显提高;同时,相比于基于用户聚类的Slope One推荐算法,改进算法具有明显的改进效果。

山区公路项目斜坡基底高填方边坡支护探讨

以某山区公路项目为例,探讨其路基边坡基底的高填方边坡支护方案,采用有限元数值模拟的方法分析不同支护方式对高填方边坡整体稳定性的影响,提出针对性的工程措施。施工监测结果显示工程措施可有效提高边坡整体稳定性,可为类似工程施工提供参考。

递增式连续降雨条件下典型山区坡面径流产沙水动力学特征

山区复杂的下垫面条件导致了山区小流域水文响应过程的复杂性,山区坡面作为山区小流域水文响应的基本单元,研究其不同下垫面条件下径流产沙水动力特征具有重要意义。为明晰山区坡面不同下垫面条件下径流水沙水动力特征,该研究选用官山河小流域作为研究对象,基于室内模拟递增式连续降雨试验方法,研究了坡度、土层厚度分布和土层底部透水性等山区坡面下垫面特性共同作用下的坡面径流产沙水动力学特征。结果表明:1)连续降雨条件下,雷诺数、水流剪切力和径流功率随着产流时间和雨强增加呈现增加趋势,Darcy-Weisbach阻力系数呈降低趋势。2)雨强增加使雷诺数均值和径流功率均值显著增加(P<0.05),设计雨强60、90、120 mm/h时的雷诺数均值、径流功率均值分别比30 mm/h的雷诺数均值、径流功率均值增加了130%、276%、366%和171%、328%、435%;坡度增加使水流剪切力均值和径流功率均值显著增加(P<0.05),坡度15°、25°的水流剪切力均值分别比坡度5°的增加了135%和187%,坡度15°、25°的径流功率均值分别比坡度5°的均值增加了224%和357%;土层厚度分布对阻力系数均值和土层底部透水的雷诺数均值、径流功率均值有显著影响(P<0.05),土层底部透水性仅对土层厚度分布为上薄下厚的雷诺数均值和水流剪切力均值有显著影响(P<0.05)。3)雨强是影响坡面产流产沙水动力特征的主导因素,对雷诺数的方差贡献率高达83.11%,水流剪切力主要受到雨强和坡度的影响,累计贡献率达67.64%,径流功率主要受到雨强和坡度的影响,累计贡献率达80.58%。在单一雨强条件下,坡度和土层厚度分布是影响水动力参数的主要因素,土层厚度分布和坡度的交互作用、土层底部透水性和土层厚度分布的交互作用对水动力参数也有一定影响。因此,在研究坡面产流产沙规律时,除考虑雨强和坡度外,还应兼顾考虑土层厚度分布和土层底部透水性及其交互作用的影响。该研究结果可为山区坡面复杂下垫面条件下的坡面产流产沙机理提供一定的理论支撑,并为改进山区小流域水文过程分布式模拟提供参数率定依据。

基底原状土置换在超限回填边坡中的运用分析

贵州山区工程建设用地紧张,场地高填深挖现象普遍。以贵州省某县城一弃土场为例,研究分析了坡脚强支护和基底原土置换在超限回填边坡中的应用。通过经济、技术、工期和弃土能力等方面的对比分析,超限回填边坡采用基底原土置换的方案,具有技术可靠、性价比高、工期短等优点,是一种相对科学可行的方案。

中关村广场结构加固改造设计

针对中关村广场结构加固改造,对比不同的加固方法之后,确定了在原有楼层不拆除的情况下,先在拟增加楼板位置施工梁、板结构,后拆除原有结构梁、板的加固方法;同时,介绍了新增梁与原结构柱连接构造做法,减小了施工难度。通过对比分析改造前后房屋的抗震设防标准及抗震等级,采取了改变结构体系加固方法,并根据现状建筑大部分位于地下室的特点,采取了抗震性能化设计方法,避免了大范围加固框架柱,节约了加固成本。在保持现状顶板覆土不移除的情况下,通过托换技术,采用扩大截面法对梁下部进行加固,达到了建筑功能需求。最后对比了抗浮锚杆抗浮加固方案、增加底板刚度抗浮加固方案、回填压重材料加固方案的经济性,并最终选择了抗浮锚杆抗浮加固方案,解决了该项目抗浮问题。

基于NbS结构的黄土填方边坡降雨物理模型试验

黄土高原地区,在“平山造城”“固沟保塬”“治沟造地”等计划开展过程中产生了大量的填方工程边坡,存在着巨大的地质灾害隐患。为了对黄土高原地区填方边坡治理提供新的解决思路,本文将黄土-古土壤层状自稳结构引入黄土填方边坡的灾变防控中,利用生石灰以及改性纤维素对黄土进行改良,提出了基于自然的解决方案(natural-based solutions,NbS)理念的黄土填方边坡控水结构,并开展人工降雨物理模拟实验,探究了有无控水结构下填方边坡渗流场、应力场和形变场变化规律、低渗场性质对边坡的影响,最终得出边坡失稳破坏模式。结果表明:1)改良黄土具有良好的工程性质,与重塑黄土相比,其液限、塑限均提高,抗剪强度增强,饱和渗透系数大幅下降,其中,改性纤维素改良黄土渗透系数降低88.59%,石灰改良黄土渗透系数降低95.18%,有控水结构边坡水分运移速度较慢,低渗层起到了良好的隔水效果;2)抗侵蚀面层的存在提高了边坡的抗侵蚀能力,有控水结构坡面的侵蚀量仅为无控水结构的28.43%;3)有控水结构边坡变形破坏模式为渐进式剪切滑移失稳,无控水结构边坡变形破坏模式为突发式溃散流滑破坏。本研究成果可为黄土高原地区填方边坡的生态治理及灾变防控工作提供理论参考。

Influence of rock property correlation on reliability analysis of rock slope stability: From property characterization to reliability analysis

Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden.

坡耕地等高反坡阶整地措施对滇中典型流域土壤酸碱性和酶活性的影响

【目的】探讨等高反坡阶整地措施对坡耕地酸化土壤改良效果及酶活性的影响。【方法】以滇中迤者流域试验区已实施等高反坡阶的坡耕地土壤为研究对象(原状坡耕地为对照),采用野外调查采样、室内实验及经典统计分析的方法,研究试验样地土壤pH、交换性阳离子(Ca^(2+)、Mg^(2+)、K^(+)、Na^(+)、H^(+)、Al^(3+)、Fe^(3+))、阳离子交换量(CEC)及蔗糖酶、脲酶、磷酸酶、过氧化氢酶、蛋白酶、多酚氧化酶、淀粉酶指标的变化规律,以探究土壤酸化及酶活性变化特征。【结果】坡耕地等高反坡阶措施可显著降低致酸阳离子(H^(+)、Al^(3+)、Fe^(3+))含量(P<0.05),使得交换性H+降低20.00%,交换性Al^(3+)和交换性Fe^(3+)含量分别减少25.64%和69.29%。提升土壤pH 9.46%~13.25%、增加交换性盐基离子(Ca^(2+)、Mg^(2+)、K^(+)、Na^(+))11.14%~39.31%、3.59%~8.96%、7.89%~17.14%、3.35%~7.99%及CEC含量(P<0.05)14.74%~21.33%。实施措施后土壤脲酶、蔗糖酶、蛋白酶、过氧化氢酶和微生物量碳、氮的活性显著提高(P<0.05)6.43%~15.28%、7.00%~31.70%、38.56%~73.71%、8.01%~21.20%、7.08%~11.14%和17.57%~31.48%,磷酸酶活性较原状坡耕地显著(P<0.05)下降38.00%~95.85%,且pH、交换性盐基离子和CEC含量均与酶活性呈极显著正相关(P<0.01),而致酸阳离子与酶活性呈极显著负相关(P<0.01)。双因素方差分析表明,整地措施、酸化影响指标(pH、交换性离子)及其二者交互作用显著影响着酶活性(P<0.05),酸化影响指标对酶活性的贡献最大。【结论】布设等高反坡阶措施能改善土壤酸化环境,增强酶活性,这对于解决坡耕地土壤酸化问题,提高山区坡耕地生产力具有重要意义。

Different influences of u-InGaN upper waveguide on the performance of GaN-based blue and green laser diodes

Performances of blue and green laser diodes（LDs） with different u-InGaN upper waveguides（UWGs） are investigated theoretically by using LASTIP. It is found that the slope efficiency（SE） of blue LD decreases due to great optical loss when the indium content of u-InGaN UWG is more than 0.02, although its leakage current decreases obviously. Meanwhile the SE of the green LD increases when the indium content of u-InGaN UWG is varied from 0 to 0.05, which is attributed to the reduction of leakage current and the small increase of optical loss. Therefore, a new blue LD structure with In（0.05） Ga（0.95）N lower waveguide（LWG） is designed to reduce the optical loss, and its slope efficiency is improved significantly.

Development of slope mass rating system using K-means and fuzzy c-means clustering algorithms

Classification systems such as Slope Mass Rating(SMR) are currently being used to undertake slope stability analysis. In SMR classification system, data is allocated to certain classes based on linguistic and experience-based criteria. In order to eliminate linguistic criteria resulted from experience-based judgments and account for uncertainties in determining class boundaries developed by SMR system,the system classification results were corrected using two clustering algorithms, namely K-means and fuzzy c-means(FCM), for the ratings obtained via continuous and discrete functions. By applying clustering algorithms in SMR classification system, no in-advance experience-based judgment was made on the number of extracted classes in this system, and it was only after all steps of the clustering algorithms were accomplished that new classification scheme was proposed for SMR system under different failure modes based on the ratings obtained via continuous and discrete functions. The results of this study showed that, engineers can achieve more reliable and objective evaluations over slope stability by using SMR system based on the ratings calculated via continuous and discrete functions.

SEGREGATION OF ALLOYING ELEMENTS IN CAST Ni-BASE SUPERALLOYS

An investigation was made on the possibility of using Ni-x phase diagrams to judge the sym- bol and degree of segregation of alloying element x in cast nickel-base superalloys.The pre- diction coincides with the experimental data.

Effect of VFe addition on hydrogen storage behavior of TiMn_(1.5)-based alloys

The hydrogen absorption and desorption behavior of TiMn_(1.25)Cr_(0.25)alloys with VFe substitution for partial Mn was investigated at 273, 293 and 313 K. It is found thatVFe substitution increases their hydrogen storage capacity, decreases the plateau pressure and thehysteresis factor of their pressure-composition-temperature (PCT) curves. After annealing treatmentat 1223 K for 6 h, TiMn_(0.95)Cr_(0.25)(VFe)_(0.3) alloy exhibits a lower hydrogen desorptionplateau pressure (0.27 MPa at 313 K) and a smaller hysteresis factor (0.13 at 313 K); the maximumand effective hydrogen storage capacities (mass fraction) are 2.03% and 1.12% respectively, whichcan satisfy the demand of hydrogen storage tanks for proton exchange membrane fuel cells (PEMFC).