黄土滑坡滑带土剪切蠕变特性试验研究

滑带土蠕变特性对渐变型边坡时效变形起控制性作用。本文以黄土滑坡滑带土为研究对象,以含水率14%、18%、22%和26%作为控制条件,开展剪切蠕变试验,分析不同含水状态下黄土的应变特征、蠕变速率和长期强度变化规律。研究表明：滑带土在水作用下蠕变现象明显,包含衰减、稳定和加速蠕变阶段,与渐变型滑坡三阶段演化过程相对应;含水状态的增强对黄土蠕变变形和速率的增长起一定的促进作用,含水率的升高可能会使黄土更容易发生蠕变破坏行为;滑带土在四种含水率下的长期强度分别为96.37 kPa、78.04 kPa、65.38 kPa和41.29 kPa,长期强度随含水作用的增强而递减。该研究可为渐变型黄土滑坡长期变形及时变稳定性研究提供参考。     

三峡库区黄土坡滑坡滑带工程地质特征研究

在宏观分析滑坡地质特征的基础上,结合室内及现场试验对黄土坡滑坡Ⅰ号临江崩滑堆积体滑带土岩性、颗粒成分、矿物成分、微观结构、物理力学特征与崩滑体在水库回水条件下的变形进行分析研究。结果表明,滑带土中黏粒及粉粒含量较高,有明显的深层蠕变磨光面和擦痕,且含有亲水的黏土矿物成分和呈片状结构特征是滑带土在回水作用下易饱水软化的重要条件;滑带土饱水后力学强度降低是导致崩滑体蠕动变形的重要原因。     

典型黄土滑坡滑带土不同含水率下蠕变特性试验研究

黄土斜坡在受到降雨、人工灌溉、河流水浸润等作用后容易发生蠕变,最终发生滑坡,有时甚至会造成灾难性事故。以往研究中对不同含水率下黄土滑坡滑带土的蠕变性质研究较少,更缺乏定量化的规律分析。以榆林市色草湾村黄土滑坡滑带土为例,进行了一系列三轴蠕变试验,得到了黄土不同含水率下(w=10%、12%、14%、16%、18%,w表示含水率)的应力-应变-时间曲线与应力-应变等时曲线,分析了含水率对黄土蠕变特性的影响,并利用等时曲线法求取了黄土的长期强度,得出如下结论:(1)含水率越大,样品蠕变破坏所需的偏应力越小,轴向应变也越大,含水率增大后自由水厚度增大,土颗粒间胶结程度减小,且水膜会对土颗粒起润滑作用易于其错动滑移;(2)含水率越大,施加每级荷载后样品蠕变曲线达到稳定状态所需时间越长,水分的增加会使土体结构完整性降低,在应力的作用下土体内部结构调整相对缓慢,固结和蠕变过程中孔隙水压力消散需要的时间也越长;(3)通过分析黄土试样蠕变破坏表面形态发现,含水率较小时,蠕变破坏后的试样有明显的剪切破坏面,当试样含水率越大时,越容易发生横向鼓胀,表现出塑性破坏特征,表明含水率较大时,水的软化作用大于水对于...     

锁儿头滑坡滑带土不同含水率大剪试验研究

锁儿头滑坡属特大型断层破碎带滑坡。该滑坡滑带土主要由强风化的中、上志留统千枚岩、板岩等构成,滑带土中粒径大于2 mm的颗粒含量约为30%,在滑带土颗粒组成中占有重要地位,其强度特征对滑坡体的稳定性分析具有重要影 响。为此,利用室内大型直剪仪对不同含水率下锁儿头滑坡滑带土的剪切特性进行试验研究,结果表明,在控制干密度为1.7 g/cm3情况下,不同含水率滑带土试样的剪应力-应变关系均呈现出弱应变硬化特征,而且法向压力越大,应变硬化特征越明显;在剪应变ε为10%时,相同含水率下滑带土剪切模量G0.1随法向压力的增大而增大,同一法向压力下的剪切模量G0.1与含水率间呈负线性相关关系;利用邓肯-张双曲线模型对锁儿头滑坡滑带土不同含水率下大剪试验剪应力-应变关系进行数据拟合,拟合效果良好,但该模型不能反映土的应变软化性质。     

Residual-state creep of clastic soil in a reactivated slow-moving landslide in the Three Gorges Reservoir Region,China

We study the creep properties of clastic soil in residual state. The intact samples are taken from a reactivated slow-moving landslide in the Three Gorges Reservoir Region, China. Firstly, the patterns of the landslide movement are analysed based on recent monitoring data, which indicate that the soil within the shear zone is undergoing two deformation processes: a creep phase, characterised by different creep rates, and a dormant phase. We then study the creep behaviour of the soil samples through a series of ring shear creep tests under various shear stress conditions. The creep response depends strongly on the ratio of the shear stress to the residual strength, and the normal effective stress, whereas the creep rate decreases due to strength regain. The long-term strength of the clastic soil is close to the residual strength. Therefore, the residual strength obtained from conventional shear test, which is less time consuming than creep test, can be used in long-term stability analyses of creeping landslides.     

Three-dimensional analyses of the sliding surface distribution in the Huangtupo No. 1 riverside sliding mass in the Three Gorges Reservoir area of China

The Huangtupo landslide is one of the largest and most destructive landslides still deforming in the Three Gorges area of China. In recent years, most studies on this landslide have been based on the data obtained from an investigation conducted in 2001. To further elucidate the geological structure and evolution of the landslide, we began building a field test site in the area of the sliding mass with the fastest deformation velocity in 2009. A group of tunnels with a total length of 1.1 km has been excavated, and nine boreholes with depths between 76.8 and 127.1 m have been drilled into the sliding body. Additionally, relative monitoring devices, such as borehole inclinometers and crack meters, have been installed. Based on the findings of the previous investigation and the latest tunneling, drilling, and monitoring data, a spatial distribution model of the sliding surfaces of the Huangtupo No. 1 riverside sliding mass has been established using the discrete smooth interpolation (DSI) method. Significant differences are revealed between the previous proposed sliding surface and the latest monitoring data. We propose that the Huangtupo No. 1 sliding mass has two sliding surfaces. Thus, the sliding mass can be further divided into two secondary sliding bodies, which are named the No. 1-1 (east) and No. 1-2 (west) sliding masses. The No. 1-1 sliding mass slid first, and the material along the western boundary slid later, producing the No. 1-2 sliding body, which has a smaller volume and shallower depth. The areas, volumes, and thicknesses of each sliding body have been calculated using a digital 3D model.     

黄土滑坡滑带土的特点——以天水椒树湾滑坡为例

黄土滑坡已成为影响黄土地区公路、铁路等基础设施建设的主要因素,滑坡的形成在一定程度上就是滑带土变形破坏过程。从黄土滑坡滑带土的分类、物理力学性质、宏观与微观特征等方面进行了较系统的研究,探究其变形和破坏规律。结合甘肃天水的黄土滑坡实例进行了具体分析。     

低速缓动滑坡滑带土剪切蠕变特性

滑带土的蠕变特性对低速缓动滑坡的形成演化过程起着控制性作用。本文选取典型的低速缓动滑坡—二庄科北区滑坡的滑带土为研究对象,在不同正应力水平作用下,通过对该滑带土的饱和试样进行直剪蠕变试验,研究了它的剪切蠕变特性。结果表明:该滑带土具有明显的蠕变特性,均包括瞬时变形、衰减蠕变和稳态蠕变3个阶段;随着剪切荷载的增大,衰减蠕变阶段及瞬时变形阶段的变形量均增大,衰减蠕变持续时间更长;其等时应力—应变曲线呈现出非线性特征,且曲线具有明显拐点;在长期荷载作用下出现强度损失,且正应力越大,强度损失越大;随着时间增大,衰减蠕变阶段的剪应变率越来越小,且剪应力越大,剪应变率越大;在蠕变破坏前的阶段,剪应变率随正应力增大而减小,即滑坡埋深越深,滑速越慢。     

Determination of soil properties for plane strain condition from the triaxial tests results

Significant difference in stress–strain behavior of dense cohesionless soil has been observed between plane strain and triaxial test conditions. At present, majority of geotechnical laboratories have no plane strain testing facility. Therefore, geotechnical professionals are more dependent on the conventional triaxial test for soil properties, whereas many geotechnical structures prevail close to plane strain condition. A method has been proposed to determine soil properties for plane strain condition from the conventional triaxial tests. This method can especially be used to determine the internal friction angle and stress–strain relationship for plane strain condition from triaxial tests results. Copyright © 2015 John Wiley & Sons, Ltd.     

流体作用下石榴石溶解-沉淀蠕变过程——以红河-哀牢山剪切带内石榴夕线片麻岩研究为例

石榴夕线片麻岩是中、下地壳主要组成岩石之一,岩石内石榴石和夕线石的结晶学优选方位会显著影响地壳深部流变性质,因此探讨特征变质矿物的变形机制和主要受控因素对构造带深部演化过程有深远意义。本文选取红河-哀牢山韧性剪切带内石榴夕线片麻岩为研究对象,通过定向切片内显微构造、电子探针、X-ray成分扫描、电子背散射衍射（EBSD）和相平衡模拟综合研究,揭示出石榴石在溶解沉淀反应过程中具有明显的粒度敏感性,不同粒径石榴石表现出截然不同的长宽比、成分环带、包裹体排列方式和压力影发育情况。石榴石表面流体活动明显截切早期生长环带。EBSD分析揭示石榴石破碎颗粒以绕〈112〉轴机械旋转为主,溶解过程主要集中于颗粒表面和裂隙内高曲率位置。夕线石的EBSD结果表明基质内夕线石以绕〈010〉轴旋转为主,而流体作用明显区域夕线石则以（100）[001]滑移为主。岩石相平衡模拟限定岩石变质峰期P-T条件达高压麻粒岩相,退变过程中同剪切变形导致大量流体渗入而形成降温降压退变轨迹,由~9.5kbar、760℃演化至~6.0kbar、500~600℃,并在粗粒石榴石内保存早期进变质环带,剪切抬升过程中石榴石内普遍发育垂直剪切方向的裂隙,并在流体作用下进一步改造其形态。此研究揭示红河-哀牢山剪切带内除前人报道的石榴石高温韧性变形外,还存在大量中-上地壳层次同变质反应下的溶解-沉淀蠕变作用。因此,石榴石变质-变形的综合研究有助于揭示变质杂岩带挤压-剪切-伸展多阶段构造演化过程。

     

In situ infiltration test using a reclaimed abandoned river bed: managed aquifer recharge in Shijiazhuang City,China

Managed aquifer recharge (MAR) is necessary for water resources management in arid and semiarid regions. Infiltration rate is often a decisive limiting factor in site selection for MAR. In order to avoid scale effects in the application of infiltration rate parameters, the largest in situ infiltration test in China was undertaken between August 19 and August 30, 2009 to measure the infiltration rate of the field selected for MAR in Shijiazhuang City, China. The in situ test lasted for 10 days, and about 1.82 × 10⁷ m³ of water was introduced into the infiltration field. Groundwater level variations were monitored during the test. Monitoring showed that the infiltration rate of surface water was 1.5 m/day, which means that about 10–15 × 10⁸ m³/a of water could be injected into the target aquifer. Also, groundwater level variations showed that the northern part of the infiltration field had a higher infiltration rate, as predicted, and the test result supplied a sound foundation for validation of the groundwater numerical simulation, which will be of benefit for future predictions of the response of the groundwater level to artificial recharge engineering. Finally, an artificial recharge plan was proposed based on the infiltration test results and the water source conditions, which would be useful for the development of MAR programs and management of local water resources.     

Analysis of dynamic factors of debris landslide by means of the model of quantitative theory—using the Xintan landslide, China, as an example

If prediction of a debris landslide is to be completed, the first problem is how to determine and correlate the dynamic factors. The special composition and complicated geological conditions of debris landslides have many dynamic factors influencing displacement and stability. Correlations are generally very complicated. The relationship and sequence of factors is too complex to be completed by traditional mathematical model. In order to solve the problem above, a systematical study of the quantitative and qualitative dynamic factors using a model of the quantitative theory was performed based on the displacements of Xintan landslide, China. Rainfall was found to be the most important dynamic factor among the six factors controlling displacements. Relative importance sequence and correlation was also established. All prediction results agree with the mechanism and displacement pattern of the Xintan landslide. Optimized measures of prevention and control for debris landslides can be completed with correlation of the dynamic factors by means of the quantitative theory model.     

陕北风沙滩地区包气带抗污能力试验研究

为了研究陕北风沙滩地区包气带风积沙的抗污能力,在榆林煤化工厂厂区及其周边地区选择4个试验点,采用双环入渗法,选择渣场炉渣浸出液（Cd、Cr、Cu、Mn、Ni和Pb重金属污染物溶液）进行渣场污水入渗试验,采用人工配置污染物溶液（COD、氨氮、F、石油类和挥发酚）进行了配污试点试验。渣场污水入渗试验过程中,由于水流的冲刷作用,剖面上大部分污染物的含量都小于入渗前的含量;而渗后样的测定结果则表明包气带风积沙对污水中Cr、Cu、Mn、Ni和Pb的净化能力较强。配污试点试验表明包气带对无机污染物的阻滞作用会延缓其对地下水的污染,石油类在包气带中的运移速度缓慢,难以在水流的作用下到达含水层,而COD容易造成地下水污染,挥发酚对含水层的污染能力要小于COD。应考虑采取适当方式降低地下水位,增大包气带厚度,以加强包气带对地下水的保护能力。     

Erosion effects on soil properties of the unique red soil hilly region of the economic development zone in southern China

Erosion can have a significant impact on soil properties in areas characterized by undulating topography. The spatial trends of soil properties and the availability of soil nutrients change with land use conversion. Most studies on these changes in China, however, focus on the natural or agricultural ecosystems. Little attention has been paid to unique changes, such as the conversion of natural or agricultural land to economic development zones. To this end, it has been determined that the properties of the surface soil in an economic development zone with unique topography characterized by large mounds of earth and stones in the red soil hilly region in China. The aim of this study is to characterize the overall level and spatial patterns of the concentrations of topsoil selected soil properties, including pH, cation exchange capacity (CEC), bulk density, soil moisture, soil organic carbon (SOC), soil nitrogen (N), soil phosphorus (P), and soil potassium (K). Results show that the mean pH and CEC of soils is as low as 5.35 and 6.47?cmol?kg^?1, and the mean value of soil moisture is 0.30?g?g^?1, and the mean level of bulk density is 1.45?g?cm^?3. SOC and total P are as low as 5.89 and 0.35?g?kg^?1, while total N and total K have a high level of 8.44 and 25.2?g?kg^?1. The mean level of alkali-hydrolyzable N, Olsen P, and available K is 54.33, 6.35, and 120.33?mg?kg^?1, respectively, all at intermediate or low levels according to the Second National Soil Survey. All selected soil properties and nutrients have overall similar spatial patterns with the highest value on the lower slope positions except for alkali-hydrolyzable N. The results are most likely governed by the native properties of red soil, zonal climate, agricultural history for all the soils, and different degrees of soil erosion, and the probable impact of human activity like construction among different slope positions. Results indicate that (1) topography influences soil properties, as evidenced by the different spatial trends of the soil nutrients, and (2) human activity, especially construction, affects the soil properties of economic development zones. This study aims to provide valuable insights for the evaluation of soil quality as a prerequisite for land use planning in economic development zones.     

Double-parameter threshold and its formation mechanism of the colluvial landslide: Xintan landslide, China

Data compiled from monitoring the displacement resulting from the Xintan landslide in China was analyzed. The stability of the demonstrated colluvial slope has a close correlation with two parameters, the velocity of the displacement and the angle of the surface vector. The stability trend can be described and evaluated by both the velocity of the displacement and the vector angles. The displacement vector angle, for which there is no substitute, serves as an explicit criterion for the stability of the slope, hence it is significant in the prediction of the catastrophic movement of landslides. A systematic analysis of the features of the vector angles of the surface displacement space and time was performed. The evolving mechanism of space-time and the characteristics of the displacement vector angles were deduced. On the basis of these deductions and by using principles of statistics, the double-parameter threshold for forecasting the stability of the colluvial slopes was established. According to the double-parameter threshold, a calculation and evaluation of stability was completed in terms of the monitoring data of the F-series of points on the Xintan slope. The forecast results coincided with the destabilized timetable, thus demonstrating that the double-parameter criterion has, to a certain extent, precision and practical application for forecasting of landslides.     

A characterisation of the physical properties of soil and the implications for landslide occurrence on the slopes of Mount Elgon,Eastern Uganda

Soil properties of major landslides that occurred recently on the mid-altitude slopes of Mount Elgon, eastern Uganda were analysed. A mudflow, located at the Kitati protected forest site, and two deep debris flows on the Nametsi and Buwabwala deforested steep slopes (36°–58°) were surveyed. In order to test the hypothesis that ‘soils at the landslide sites are particularly ‘problem soils’ and thus prone to landslides’, the following analyses were undertaken: particle size distribution, Atterberg limits, shear strength and factor of safety (F_s). Soils at the Kitati and Buwabwala sites exhibited expansive potential, owing to clay contents well above 20%. A clay content exceeding 32% was identified at the Nametsi debris flow site implying an extremely high expansive potential of the soil. High liquid limits (LLs) at Kitati (59%) and Buwabwala (53%) meant that the soils qualified as vertisols susceptible to landslides. High plasticity indices (PIs) (averaging 33%) also confirmed the vertic nature of soils at the Nametsi debris flow site. Whereas the value of F _s  < 1 for the Kitati site signifies an inherently unstable slope, Nametsi and Buwabwala are supposedly stable slopes (F _s  > 1). Despite this finding, the stable sites could be described as only conditionally stable because of the interplay of various physical, pedological and anthropogenic factors. The results point to the fact that soils at the landslide sites are inherently ‘problem soils’ where slope failure can occur even without human intervention. Therefore, the hypothesis that soils at three landslide sites are inherently ‘problem soils’ and prone to landslides, is accepted.     

六盘山东麓断裂带滑坡类型与变形机理研究——以泾河源区为例

六盘山东麓地层结构特殊,断裂褶皱等构造发育,滑坡及其隐患点等不良地质灾害较多,特殊的地理、构造位置和潜在的孕震背景,致使该区具有产生大型滑坡的可能。本文依据新一轮以图幅带专题研究的地质灾害调查获取大量的数据,通过统计分析,对六盘山东麓断裂带滑坡产生的孕灾地质环境条件及其滑坡特性等进行了剖析,将研究区滑坡归纳为红层软岩滑坡、断层影响型滑坡、堆积层滑坡、黄土型滑坡4种不同类型,同时对其形成机理进行了探讨分析与研究,为完成地质灾害风险性区划评价,提出地质灾害综合防治对策建议提供了重要的理论依据。     

A method for identifying soil properties influencing crop yield: the example of maize in the Savanna Belt of South-western Nigeria

This paper describes a method of identifying the crucial soil properties influencing yields of crops, using the example of maize in south-western Nigeria. The method involves first, the examination of the relationship between soil properties and the maize parameters using the simple bivariate correlation analysis and the multiple regression model. It also involves, in part, the computation of an index of soil variable contribution to maize prediction in order to identify the crucial soil properties influencing the yield of the crop. In the current study, the multiple regression model reduces the 20 soil properties analysed to the 14 that have made significant contributions to the crop's prediction. The 14 variables were later reduced to two using the maize-prediction index. The index has the merits of being very simple to compute and the ability to reduce the numerous variables to few significant ones as far as the crop under investigation is concerned.     

Diurnal soil water dynamics in the shallow vadose zone (field site of China University of Geosciences,China)

Because of the relatively low soil moisture in arid or semi-arid regions, water vapour movement often predominates in the vadose zone and affects the partitioning of energy among various land surface fluxes. In an outdoor sand bunker experiment, the soil water content at 10 and 30 cm depth were measured at hourly intervals for 2.5 days during October 2004. It was found that the soil moisture reached the daily maximum value (5.9–6.1% at 10 cm and 11.9–13.1% at 30 cm) and minimum value (4.4–4.5% at 10 cm and 10.4–10.8% at 30 cm) at midday (0–1 p.m. for 10 cm and 2–3 p.m. for 30 cm) and before dawn (2–3 a.m. for 10 cm and 4–5 a.m. for 30 cm), respectively. The modified HYDRUS-1D code, which refers to the coupled water, water vapour and heat transport in soil, was used to simulate the moisture and water vapour flow in the soil. The numerical analyses provided insight into the diurnal movement of liquid water and water vapour driven by the gradients of pressure heads and temperatures in the subsurface zone. The simulated temperature and water content were in good agreement with the measured values. The spatial–temporal distribution of liquid water flux, water vapour flux and soil temperature showed a detailed diurnal pattern of soil water dynamics in relatively coarse sand. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.