黄土斜坡稳定性的模糊信息分析法

本文基于黄土斜坡稳定性的实际资料,利用信息分配、模糊一二级近似推论及信息集中等原因建立了一套黄土斜坡稳定性的评价方法。用这套方法对一些黄土斜坡(非母体)稳定性进行了验证,其结果与实际情况一致。本方法已应用于兰州市滑坡防灾规划和皋兰山三台阁北侧几个滑坡及斜坡稳定性的研究中,效果良好。     

云南公路滑坡稳定性分析中模糊信息分析法的应用

将模糊信息分析方法应用于公路滑坡稳定性分析。运用模糊信息分析中的模糊信息信息分配、信息集中等方法,在云南元磨高速公路滑坡的50组公路滑坡资料中选取了滑坡高度、坡度、组成物质的粘聚力、内摩擦角等重要影响因素,建立了其与滑坡稳定性之间的模糊关系,得到相应的滑坡稳定性分析数学模型。应用该模型对该区域其他滑坡进行验证,其效果良好,故该方法可较好的应用于实际。     

A nonstationary parameter model for the sandstone creep tests

The rock masses of hydro-fluctuation belt experience seepage pressure following impoundment in the Three Gorges Reservoir; its creep behaviors are significant for reservoir bank slopes. To study the creep behaviors under seepage pressure (0, 1.45, and 1.75 MPa), we performed creep tests using representative landslide sandstone in the Three Gorges Reservoir and investigated the sandstone creep behaviors under the coupling effects of seepage pressure and stress. Previous researches on rocks have usually regarded the creep constitutive parameter as a constant; however, in this study, a nonlinear, nonstationary, plastic-viscous (NNPV) creep model which can describe the curve of sandstone creep tests is proposed. The rock-creep parameters under three levels of seepage pressure were identified, and theoretical curves using the NNPV model agreed well with the experimental data, indicating that the new model cannot only describe the primary creep and secondary creep stages under varying seepage pressures but also, in particular, perfectly describes the tertiary creep stage. Finally, the sensitivity of the NNPV model parameters is analyzed, and the result shows that the nonstationary coefficient α and the nonlinear coefficient m are main parameters affecting the tertiary creep stage.     

Study on the deformation and failure modes of filling slope in loess filling engineering: a case study at a loess mountain airport

Lvliang airport is a typical loess filling engineering located in 20.5 km north of Lvliang City in Shanxi Province, China. By the end of March 2012, 14 fissures extending more than 7.5 m were observed in a loess-filled slope, of which the longest fissure is up to 82 m. Field monitoring and laboratory tests have been performed to investigate the slope failure modes. The test program includes wetting tests on unsaturated compacted samples and stress path tests on saturated samples. Field monitoring and observations show that differential settlement caused by non-homogeneity in compacted loess density might lead to the formation of fissures in the loess-filled slope. It was founded that the wetting deformation contributed to the development of differential settlement. Fissures are the essential factor for the loess-filled slope failure. Four deformation stages exhibit in the loess-filled slope prior final failure including development of the fissures, softening of the compacted loess, creeping of the slope leading edge and fissuring of the trailing edge and formation of the through-sliding surface. Development of the sliding surface mainly includes upward and downward expansion of the fissures. Upward expansion is a wetting failure process in loading condition, while downward expansion is a load-off wetting process. In addition, development of the sliding surface is accelerated by softening of the compacted soils as a result of water infiltration. Therefore, the key for taking countermeasures against filling landslides is to monitor and control the development of differential settlement and fissures in the slope shoulders. Digging out and extra-filling the fissures are an effective way for preventing these landslides.     

模糊数学在西北地区场地震害预测中的应用

本文收集了西北地区大量的震害资料及实验室试验结果,利用信息分配,模糊综合评判及信息集中等原理建立了一套适用于西北地区的场地震害的预测方法。文中将场地分为三类:稳定区、基本稳定区和不稳定区。以地形地貌、土的液化、土的震馅、人工填土的厚度、软土(厚度大于0.3米)的埋深以及边坡稳定性等六个因素作为评价的指标。用这套方法对宝鸡、西安两市的一些场地震害进行了评价计算,其结果与宏观分析的结果一致。     

Effects of molding water content and compaction degree on the microstructure and permeability of compacted loess

Acta Geotechnica - Molding water content and compaction degree are the major factors driving differences in the microstructure, which has a control on the permeability of compacted loess. Although...     

Fully coupled hydraulic fracture simulation using the improved element partition method

The improved element partition method (IEPM) is a newly developed fracture simulation approach. IEPM allows a fracture to run across an element without introducing extra degrees of freedom. It can also simulate any number of fractures in a prescribed mesh without remeshing. In this study, the IEPM is extended to hydraulic fracture simulation. First, the seepage and volumetric storage matrix of a cracked element are derived using virtual nodes (the intersection points of a crack with element edges). Subsequently, the fully coupled hydromechanical equation is derived for this cracked element. To eliminate the extra degrees of freedom (virtual nodal quantities), the water pressure and displacement of the virtual nodes are associated with their adjacent nodes through least squares interpolation. Finally, the fully coupled equation in terms of nodal quantities is obtained. The verification cases validate the method. By using this method, the field-scale hydraulic fracturing process is well simulated. The proposed approach is simple and efficient for field-scale hydraulic fracture simulation.     

地形对黄土高原滑坡的影响

高分辨率地形与影像数据的缺乏已成为研究地表现象、特征与过程的重要瓶颈。低成本无人机设备和摄影测量技术的发展,打开了地学领域获取高分辨率数据的大门,大大提高了地质灾害野外调查与灾害编目的精度与效率。本文通过无人机野外调查和遥感室内目视解译,构建了一个包含307个黄土滑坡属性的数据库。在此基础上,通过数字地形分析和数理统计等方法,总结归纳了黄土滑坡样本数据的分布规律,探讨了地形对黄土滑坡分布的影响,阐述了地形相对高差对最长滑动距离、滑坡周长、滑坡面积的影响,提出了基于传统经验公式拟合的滑坡规模快速预测公式。结果表明：① 滑坡规模—频率分布具有明显的规律性,不同最大长度、最大宽度和周长的黄土滑坡数量分布均呈现正偏态分布,而不同面积的滑坡数量分布则服从幂函数分布;② 地形对黄土滑坡发育控制作用明显,不同地形高差、平均坡度、坡形的斜坡单元滑坡发育数量差异较大;③ 地形相对高差与滑坡的最长滑距、周长和面积的拟合曲线很好地符合幂律分布规律,但不同地形区的拟合效果有所差异,黄土丘陵区拟合效果最好,黄土高原全区次之,黄土台塬区最差;④ 本文建立的黄土滑坡规模快速预测模型,为黄土滑坡灾害调查提供了经验公式支撑。     

黄土裂隙的漫灌效应对斜坡稳定性的影响分析

以甘肃省黑方台地区滑坡为研究对象,在非饱和土特性试验基础上,根据地下水位的监测资料建立典型斜坡饱和-非饱和渗流模型,模拟斜坡灌溉作用后裂隙对斜坡渗流场的影响,研究斜坡裂隙效应对斜坡稳定性的影响。结果表明:灌溉水迅速沿裂隙下渗,形成渗流优势通道;裂隙附近土体的孔隙水压力迅速升高,导致其局部形成饱和区域;随着裂隙数量的增加,饱和区域明显增大,且裂隙的位置越靠近台塬边缘,对斜坡边缘的孔隙水压力及基质吸力影响越显著。综合斜坡稳定性分析结果可知:裂隙发育位置越靠近台塬边缘,斜坡稳定性越差;而裂隙数量的增加对于斜坡的稳定性影响更大,且裂隙对于斜坡稳定性的影响是一个短时间过程。夯填裂缝是控制滑坡发生的有效途径。     

Zircon U-Pb Ages of Quaternary Loess-Paleosol Sequences from the Luochuan Section: Implication for Sediment Provenance

<正>Objective The sediment provenances of the thick Quaternary Loess-Paleosol sequences of the Chinese Loess Plateau can provide clues to the evolution of the paleoclimate and paleoenvironment in East Asia.Furthermore,based on the proposed sediment sources and transport routes,the evolution of the East Asian monsoon can be evaluated.