Upper Bound Solution of Soil Slope Stability under Coupling Effect of Rainfall and Earthquake

Based on the limit analysis upper bound method,a new model of soil slope collapse has been proposed which consists of two rigid block zones and a plastic shear zone.Soil slope was induced failure by coupling effect of rainfall and earthquake,and these blocks were also incorporated horizontal earthquake force and vertical gravitate.The velocities and forces were analyzed in three blocks,and the expression of velocity discontinuities was obtained by the principle of incompressibility.The external force work for the blocks,the internal energy of the plastic shear zone and the velocity discontinuous were solved.The present stability ratios are compared to the prevenient research,which shows the superiority of the mechanism and rationality of the analysis.The critical height of the soil slope can provide theoretical basis for slope support and design.

Impact of Surface Water and Groundwater Pollutions on Irrigated Soil, El Minia Province, Northern Upper Egypt

Current research has been focused on heavy metals pollution in surface water and groundwater and effect on irrigated soil from El Minia Province, north Upper Egypt. Concentration of heavy metals (e.g., As, Co, Hg, Ni, Se, Cd and Cr) in surface water, groundwater and irrigated soil samples is most significantly affected by leachate of many pollutants as the factories, agricultural activities, urban and natural processes. Microbiological parameters and microscopic investigations are revealed that some localities are common by micro-organisms, which are unsuitable for drinking waters.

Characteristic of Soil Hydro-Physical Properties and Water Dynamics under Different Vegetation Restoration Types

By combining the observation of the soil profile at field and the chemical and physical analysis in laboratory, a study on the hydro-physical properties of soil in six different vegetation types and the dynamics of water content after rain was conducted in Wanchanggou, Guangyuan City to find out the vegetation types with effective water-conservation functions in order to serve the ecological restoration in the low hill heavy rain area upper the Jialing River. Results showed that., the hydro-physical properties of soil in the mixed Alnus crernastogyne and Cupressua Leyland forest （AcCl） were best. But in the depth of 0-20 cm. The properties of soil in the abandoned cropland （Fm） was better than that in the AcCl. The soil bulk densities varied significantly between the layers of 0-20 cm and 20-40 cm in all the six vegetation types except that in the Robinia pseudoacacia shrub forest （RpII）, and the changes of the maximum and the capillary moisture capacity between layers were significant only in the Fm and in the AcCl. Of these stands, the AcCl had the shortest water-absorbing period and the strongest moisture changes in the upper layer （0-15 cm）. In the same stand, the deeper the soil layer, the slighter the soil moisture varied, and the longer the soil moisture accumulating process lasted.

基于极限分析上限法的地震作用下分层地基盾构隧道开挖面稳定性研究

目前针对盾构隧道开挖面稳定性的研究还较少考虑土体分层特性和地震作用的耦合影响,因此构建了一种在分层土体中考虑地震作用的开挖面三维对数螺旋破坏模型进行研究。首先,将地震引起的动态响应通过拟静力法简化为水平和竖直两个方向上的惯性力作用;其次,在均质土体中的三维对数螺旋破坏机制的基础上,将其改进为适用于分层土体的三维对数螺旋破坏机制;再次,根据上限定理,在虚功率方程中引入地震惯性力所做功率,得到考虑土体分层特性和地震作用条件下的盾构隧道开挖面支护力的上限解;最后,将上限理论解与三维数值模拟结果和既有模型试验结果进行对比,得到了较好的一致性。此外,针对水平地震加速度系数和地层厚度对关键物理特征进行了影响因素分析。结果表明,当比例系数ζ>0时,极限支护力随水平地震加速度系数的增大显著增大;当ζ<0时,极限支护力随水平地震加速度系数增大而增大的趋势减弱。当水平地震加速度系数kh=0时,即在无地震作用情况下,归一化极限支护力不随ζ的变化而变化;在上硬下软土层中,下部土层厚度比的增大会引起极限支护力的增大,在上软下硬土层中,下部土层厚度比的增大会引起极限支护力的减小。

Analysis of Penetration Depth of Pipeline on Cohesive Soil Seabed

This paper conducts laboratory tests to investigate detailedly the soil deformation law around the pipeline and its penetration depth under self-gravity. The seabed model is prepared by consolidating saturated soil using vacuum pressure technology, and the pipeline models are specifically designed to possess different radii. Based on the experimental results and digital images, the soil deformation process is analyzed and summarized, a kinematic admissible velocity field is given and an upper bound solution of pipeline penetration depth and soil reaction force is derived and proposed in this paper. In order to verify the accuracy of the upper bound solution deduced in this paper,a comparison is made among some published results and the solution suggested in this paper, the comparison results confirm that the upper bound solution and the soil failure mode are reasonable. Finally two empirical formulas are given in this paper to estimate the soil reaction force of seabed and the penetration depth of pipeline. The empirical formulas are in agreement with the upper bound solution derived in this paper, and the conclusion of this paper could provide some theoretical reference for the further study of the interaction between the pipeline and the soil.

Hydrological Modeling of Upper OumErRabia Basin (Morocco), Comparative Study of the Event-Based and Continuous-Process HEC-HMS Model Methods

Human population growth and land-use changes raise demand and competition for water resources. The Upper OumErRabia River Basin is experiencing high rangeland and matorral conversion to irrigated agricultural land expansion. Given Morocco’s per capita water availability, River-basin hydrologic modelling could potentially bring together agricultural, water resources and conservation objectives. However, not everywhere have hydrological models considered events and continuous assessment of climatic data. In this study, HEC-HMS modelling approach is used to explore the event-based and continuous-process simulation of land-use and land cover change (LULCC) impact on water balance. The use of HEC-GeoHMS facilitated the digital data processing for coupling with the model. The basin’s physical characteristics and the hydro-climatic data helped to generate a geospatial database for HEC-HMS model. We analyzed baseline and future scenario changes for the 1980-2016 period using the SCS Curve-Number and the Soil Moisture Accounting (SMA) loss methods. SMA was coupled with the Hargreaves evapotranspiration method. Model calibration focused on reproducing observed basin runoff hydrograph. To evaluate the model performance for both calibration and validation, the Coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE), Root Mean Square Error (RSR) and Percent Bias (PBIAS) criteria were exploited. The average calibration NSE values were 0.740 and 0.585 for event-based (daily) and continuous-process (annual) respectively. The R2, RSR and PBIAS values were 0.624, 0.634 and +16.7 respectively. This is rated as good performance besides the validation simulations were satisfactory for subsequent hydrologic analyses. We conclude that the basin’s hydrologic response to positive and negative LULCC scenarios is significant both positive and negative scenarios. The study findings provide useful information for key stakeholders/decision-makers in water resources.

Distribution Regularity of Debris Flow and Its Hazard in Upper Reaches of Yangtze River and Other Rivers of Southwestern China

In the upper reaches of Yangtze River and other rivers of southwestern China, the debris flows develop and lead to most serious disasters because of the various landforms, complex geological structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform, geological structure, and precipitation. The regularities of distribution of debris flows are as following： （1） distributed in transition belts of different morphologic regions; （2） distributed in the area with strong stream trenching; （3） distributed along fracture zones and seismic belts： （4） distributed in the area with abundant precipitation; （5） distribution of debris flow is azonal. The activity of abundant debris flows not only brings harm to Towns, Villages and Farmlands, Main Lines of Communication, Water-Power Engineering, Stream Channels etc., but also induces strong water and soil loss. According to the present status of debris flow prevention, the problems in disasters mitigation and soil conservancy are found out, and the key works are brought up for the future disasters prevention and soil conservancy.

地震作用下双层土质边坡稳定性上限分析

为探究地震作用对双层土质边坡稳定性的影响,基于极限分析上限理论,建立了地震作用下双层土质边坡旋转破坏机构。采用拟静力法简化地震荷载作用,推导了双层土质边坡安全系数表达式。分析土体黏聚力比、边坡坡角以及地震作用对双层土质边坡稳定性及其滑动面参数的影响。研究结果表明:在水平地震作用下,随着黏聚力比的增大,边坡安全系数呈非线性增大且潜在滑动面变浅;当水平地震作用增强时,边坡失稳破坏范围显著加大;随着竖向地震系数及黏聚力比的增大,边坡安全系数略微降低;水平地震作用增强时,竖向地震作用对边坡稳定性的影响逐渐增大,此时需要考虑竖向地震的影响。

基于极限分析理论的复合地层中双模盾构开挖面稳定性研究

针对目前双模式盾构在复合地层土-岩交界面进行掘进模式转换过程中掘进面稳定性研究中存在的问题,采用空间离散技术构建双模式盾构在穿越土-岩交界面过程中开挖面前方岩土体的二维破坏机制,利用该破坏机制和极限分析上限定理推导得到极限状态下土舱压力的目标函数,通过优化计算得到盾构机在穿越土-岩交界面过程中维持开挖面稳定所需的土舱压力上限解,并讨论不同参数对土舱压力及开挖面前方岩土体破坏模式的影响。在此基础上,基于可靠度理论建立土舱压力的可靠度模型,并给出复合地层中容许可靠度下维持开挖面稳定性最小土舱压力的建议值。结果表明:盾构机在穿越土-岩交界面过程中维持开挖面稳定所需的土舱压力随着盾构机与土-岩交界面距离的减小而减小;开挖面前方岩土体的破坏范围随着界面倾角的增大而增大。

轻度放牧和禁牧草地土壤物理力学性质特征--以夏藏滩滑坡区为例

为研究轻度放牧和禁牧对黄河上游滑坡分布区草地土壤物理力学性质的影响,本研究选取黄河上游夏藏滩滑坡分布区为研究区,通过开展野外勘察、取样以及室内土壤物理力学性质试验,对比分析了轻度放牧和禁牧对滑坡分布区边坡植物生长和土壤物理力学性质的影响。结果表明:禁牧草地植物种类数量、平均覆盖度、平均株高均高于轻度放牧草地,分别增长65.1%、62.8%和13.6%;禁牧草地土壤含水率、根系干重密度、土壤黏聚力均显著高于轻度放牧草地(P<0.05),且轻度放牧草地和禁牧草地土壤黏聚力与根系干重密度均呈显著正相关关系(R^(2)=0.841和0.875,P<0.05)。本研究结果可为有效防治研究区流域河岸边坡坡面水土流失、浅层滑坡等次生地质灾害,提供理论依据和实际指导。

岛状多年冻土区高速铁路路基热状态及工程措施效果分析

为揭示岛状多年冻土区高速铁路路基热状态,提出合理有效的制冷结构,在新建哈尔滨至伊春高速铁路某车站试验段开展现场监测,获得岛状多年冻土的地温数据;基于实测地温数据,采用冻土水热耦合理论,对将在试验段实施的两侧双排普通热棒路基、两侧双排+中心单排全季热棒路基、两侧单排+基底横向通铺全季热棒路基3种制冷路基结构进行数值模拟,对比了3种制冷路基结构的地温分布特征及对下伏岛状多年冻土的降温效果。研究结果表明:铁力地区年均气温和降水呈增大趋势,天然场地岛状多年冻土地温在-0.3℃左右,属于高温极不稳定多年冻土。3种制冷路基结构中,两侧单排+基底横向通铺全季热棒对岛状多年冻土保护及降温效果最优,两侧双排普通热棒最差。普通热棒路基的多年冻土上限呈“两侧凸,中间凹”形态,抬升不明显;全季热棒路基的多年冻土上限呈“上凸缓斜平顶”形态,抬升显著。研究成果可对多年冻土区高速铁路路基建设和结构优化提供技术支撑。

大理‘KRK26’上部烟叶物理特性差异和土壤养分相关性分析

为明确大理州‘KRK26’植烟区域上部烟叶物理特性及其与土壤养分的关系,采用描述性统计、简单相关和典型相关分析方法,研究了该区域上部烟叶物理特性状况并分析了上部烟叶物理特性与土壤养分的相关性。结果表明:大理州‘KRK26’上部烟叶平均厚度0.20 mm、单叶重12.21 g、含梗率24.24%、叶面密度74.95 g/cm2、拉力1.38 N、平衡含水率13.35%,厚度略偏高、拉力偏低、其他指标与全国平均水平相当;4个植烟区的上部烟叶厚度、含梗率、叶面密度和拉力指标差异不显著,而单叶重以大理市显著高于永平和云龙、与漾濞差异不显著,平衡含水率以云龙显著最高;简单相关分析显示单叶重与土壤总氮、有效磷、交换性镁和有效锌显著正相关,与全钾、氯离子极显著负相关,叶面密度与速效钾显著负相关;同时简单相关和典型相关共同表明在一定范围内,随着土壤有机质、全磷和速效钾含量的降低,烟叶含水率降低;反之升高。

民国时期黄河上游地区水土保持建设成效与启示

民国时期,由于报刊的宣传普及、专家学者的讲演与培训、农业技术机构的设立和专门人才的培养,水土保持思想得到广泛传播,农业发展呈现新特征,林业建设和黄河治理得到了有力的推进。尽管受当时社会环境和科学技术水平的影响,黄河上游地区水土保持工作研究存在资金短缺、技术不成熟、设备落后、农民参与度不高等方面的局限性,但其在设立水土保持实验区和农业试验场、加大对水土保持的宣传普及、推进农林牧业协调发展、推进法治建设、实现乡村振兴和生态保护的协调发展等方面的做法仍然值得我们今天借鉴。

黄河上游夏藏滩巨型滑坡区根-土复合体理化与强度特性

为研究黄河上游夏藏滩巨型滑坡分布区土体理化性质及力学强度特征,本研究通过在该滑坡体不同位置制取植物及土体试样,测定各采样点植物生长量指标、土体密度、含水率、含根量、抗剪强度指标以及营养元素含量等指标;在此基础上,通过采用Spearman相关性分析方法,探讨了该滑坡体不同位置植被类型、土体理化性质以及根-土复合体抗剪强度特征。结果表明:植物种类随海拔高度降低表现出增加趋势,其中优势草本植物为异针茅(Stipa aliena)、黄花棘豆(Oxytropis ochrocephala)、沙蒿(Artemisia desertorum)等3种;滑坡分布区土体pH值呈中性至碱性,有机质、全氮、全磷等3种营养元素含量在滑坡体后缘位置变化幅度相对较大,全钾、碱解氮等其余4种营养元素变化幅度较大但未表现出明显变化规律;土体含水率随海拔高度降低呈先增加后降低,土体密度呈增加的变化趋势,即随海拔降低增加幅度分别为7.05%和5.88%;根-土复合体粘聚力c值与含根量均表现出随海拔高度降低呈先增加后降低的变化趋势;此外,通过采用Spearman相关性分析得到,根-土复合体粘聚力c值与海拔高度之间呈负相关关系,而与含根量、有机质、含水率之间则呈正相关关系。研究结果对防治黄河上游龙羊峡至积石峡流域两岸边坡水土流失、浅层滑坡等地质灾害现象具有实际指导意义。

黄河中上游地区铁路建设项目的水土保持及其监理

以黄河中上游地区铁路建设项目水土保持监理工作为背景,总结了该类工程的水土保持工程措施及监理工作开展的思路。介绍了案例工程情况,阐述了水土保持施工的准备工作、防治措施等内容。在监理工作方面,从监理项目部建设、管理制度建设、过程控制和资料管理等方面提出了完善思路。

黄土区大跨度隧道开挖技术探讨

临洮(安家咀)至临夏一级公路百和隧道均为Ⅴ级围岩,主要有黄土浅埋段、岩质地段、黄土深埋段、小净距段以及黄土深埋段等情况,针对不同的围岩情况和地质条件,有针对性的采用CD法、上下台阶留核心土法及三台阶分步法进行开挖。

论深基坑支护的空间效应

深基坑是一个复杂的三维空间问题。本文借助于坑壁土体的三维破坏模式，基于土的塑性上限理论及极限平衡分析理论，探讨了两坑壁端部对坑壁支护结构上土压力的整体屏蔽作用，提出了考虑空间效应的土压力计算公式。该计算公式可用于基坑护坡桩、地下连续墙等支护系统的设计。

武汉软土地区地铁隧道长期沉降规律及原因分析

以武汉地铁8号线出入段线矩形隧道为分析对象,将近5年的地铁运营监测沉降数据与隧道沿线工程地质条件、地下水及周边施工进行对比分析,系统研究地铁隧道长期沉降规律。结果表明,出入段线隧道最大累计沉降106.1 mm,且沿线形成了三个大的沉降槽。隧道结构下卧软弱土层较厚且分布不均、地下水位及上盖物业开发是导致出入段线长期沉降的主要原因。轨道交通结构的长期沉降问题,需要结合“设计—施工—运营”统筹考虑。

土质斜坡地层倾斜锚板抗拔承载力分析

研究目的:合理估算锚板抗拔承载力是保持锚板基础稳定工作的重要保障,本文聚焦土质斜坡地层中埋设的倾斜条形锚板,构造了一种极限状态下非对称的锚板上拔破坏机制,并假设土体破坏服从非线性强度准则与非关联流动法则。基于该破坏机制,利用上限法与变分原理,推导锚板极限抗拔承载力及锚板上方土体破坏面方程的解析表达式,系统研究各参数对锚板抗拔承载力的影响规律。研究结论:(1)推导得到了锚板极限抗拔承载力及锚板上方土体破坏面方程的解析表达式,并与现有文献成果进行了对比分析,验证了本文分析方法的有效性;(2)斜坡倾斜锚板上方土体破坏范围呈现一定的非对称特征,随锚板倾角增大,土体破坏范围逐渐向坡下方向偏移,土体破坏范围与土体剪胀系数、初始黏聚力正相关,与非线性系数、重度、地表荷载负相关;(3)锚板埋深比、埋设角度、地表倾角、土体黏聚力及剪胀系数对锚板抗拔承载力及土体上拔破坏范围会产生显著影响,在工程设计中应予以重视,以实现锚板基础的最优布设与承载能力有效发挥。

阳城隧道土砂分界地层隧道围岩变形特征及控制工法研究

为解决采用三台阶法施工的土砂分界地层隧道围岩变形控制难题,以浩吉铁路阳城隧道为依托,采用室内试验、数值模拟和理论分析等方法对不同隧道埋深及土砂分界位置(土砂比,即土层厚度与砂层厚度之比)下的隧道围岩变形规律进行研究,并提出围岩变形控制工法的选取原则。研究结果表明:1)不同隧道埋深及土砂比情况下的围岩变形曲线可分为变形预发展阶段、变形快速发展阶段、变形缓慢发展阶段和变形稳定阶段4个阶段,且均可采用Boltzmann函数进行良好拟合;2)当土砂比由0∶1增至1∶0时,隧道拱顶沉降、边墙水平收敛和仰拱隆起对土砂分界面的位置变化具有不同的响应规律;3)提出适用于采用三台阶法施工的土砂分界地层隧道围岩变形控制工法选取原则,并通过计算证明,该原则可有效指导围岩变形的控制。