Study on embedded length of piles for slope reinforced with one row of piles

The embedded length of anti-slide piles for slope is analyzed by three-dimensional elastoplastic shear strength reduction method. The effect of embedded pile length on the factor of safety and pile behavior is analyzed. Furthermore, the effects of pile spacing, pile head conditions, pile bending stiffness and soil properties on length and behavior of pile are also analyzed. The results show that the pile spacing and the pile head conditions have significant influences on the critical embedded length of pile. It is found that the critical embedded length of pile, beyond which the factor of safety does not increase, increases with the decrease in pile spacing. The smaller the pile spacing is, the larger the integrity of the reinforced slope will be. A theoretical analysis of the slip surface is also conducted, and the slip surface determined by the pressure on piles, considering the influences of both soil and piles for slope, is in agreement with the ones in previous studies.

Research on Deformation and Force of Bridge Pile Foundation on High and Steep Slope in Mountainous Area

With the rapid development of my country’s economy, the demand for infrastructure construction is also increasing. However, in most areas of China, the terrains are mountainous and hilly. Some projects have to be built on steep slopes. Choosing viaducts or half-bridges on high-steep slopes is not only conducive to the protection of the surrounding environment, but also conducive to the stability of the slope. Bridges usually choose the form of pile foundation-high pier bridge. This paper uses numerical simulation to study and analyze the bridge pile foundation of the slope section. Relying on actual engineering, use the finite element software ABAQUS6.14 to establish a three-dimensional finite element model to study the bearing mechanism and mechanical characteristics of the pile foundation under vertical load, horizontal load and inclined load, discuss the influence of the nature of the soil around the pile and the stiffness of the pile body on the deformation and internal force of the bridge pile foundation in the slope section. The analysis results show that the horizontal load has a great influence on the horizontal displacement of the pile, but has a small influence on the vertical displacement, and the vertical load is just the opposite. Inclined load has obvious “p-Δ” effect. The increase in soil elastic modulus and pile stiffness will reduce the displacement of the pile foundation, but after reaching a certain range, the displacement of the pile foundation will tend to be stable. Therefore, in actual engineering, if the displacement of the pile foundation fails to meet the requirements, the hardness of the soil and the stiffness of the pile can be appropriately increased, but not blindly.

Integration of RUSLE Model with Remote Sensing and GIS Tools for Soil Loss Estimation in the Kubanni Drainage Basin, Zaria, Nigeria

The prevalence of unwholesome land use practices and population pressure exacerbates soil loss which is worsening the problem of sedimentation of the Kubanni dam. This study was conducted at the Kubanni drainage basin covering a spatial area of 56.7 Km2 in Samaru, Zaria, Nigeria to estimate annual soil loss using the RUSLE model. Satellite images of Landsat OLI for December 2014, 2016, 2018, February, July and November 2022;soil data, rainfall data from 2010 to 2022, and DEM of 30-meter resolution were utilized for the study. All factors of the RUSLE model were calculated for the basin using assembled data. The erosivity (R-factor) was discovered to be 553.437 MJ∙mm∙ha−1∙h−1∙yr−1. The average erodibility (K-factor) value was 0.1 Mg∙h∙h∙ha−1∙MJ−1∙mm−1∙yr−1. The Slope Length and Steepness factor (LS-factor) in the basin ranged between 0% and 13.47%. The Crop Management Factor (C-factor) values were obtained from a rescaling of the NDVI values derived for the study area and ranged from 0.26 to 0.55. Support practice (P-factors) were computed from the prevalent tillage practice in the basin and ranged from 0.27 to 0.40. The soil loss amount for the Kubanni basin was found to be 28441.482 tons∙ha−1∙yr−1, while the annual soil loss for the entire Kubanni drainage basin was found to be 49780.257 tons∙yr−1. The study has demonstrated the viability of coupling RUSLE model and Remote Sensing and Geographic Information System (GIS) techniques for the estimation of soil loss in the Kubanni drainage basin.

Comparison of the Effects of the Different Methods for Computing the Slope Length Factor at a Watershed Scale

The slope length factor is one of the parameters of the Universal Soil Loss Equation(USLE)and the Revised Universal Soil Loss Equation(RUSLE)and is sometimes calculated based on a digital elevation model(DEM).The methods for calculating the slope length factor are important because the values obtained may depend on the methods used for calculation.The purpose of this study was to compare the difference in spatial distribution of the slope length factor between the different methods at a watershed scale.One method used the uniform slope length factor equation(USLFE)where the effects of slope irregularities(such as slope gradient,etc.)on soil erosion by water were not considered.The other method used segmented slope length factor equation(SSLFE)which considered the effects of slope irregularities on soil erosion by water.The Arc Macro Language(AML)Version 4 program for the revised universal soil loss equation(RUSLE).which uses the USLFE,was chosen to calculate the slope length factor.In a parallel analysis,the AML code of RUSLE Version 4 was modified according to the SSLFE to calculate the slope length factor.Two watersheds with different slope and gully densities were chosen.The results show that the slope length factor and soil loss using the USLFE method were lower than those using the SSLFE method,especially on downslopes watershed with more frequent steep slopes and higher gully densities.In addition,the slope length factor and soil loss calculated by the USLFE showed less spatial variation.

青藏高原坡度坡长因子(LS)空间格局及影响因素分析

地形是影响土壤侵蚀的主要因素,但目前关于青藏高原地形因子的分布格局和影响因素有待研究。基于1弧秒分辨率的SRTM(shuttle radar topography mission)高程数据,计算坡度、坡长、LS因子(slope length and steepness factors,LS),结合高程积分和Hack剖面等,对青藏高原LS因子的分布格局、统计分布特征和影响因素进行研究,结果表明:(1)坡度、坡长和LS因子这3个地形指标,均表现出高原内部小、四周高山大的格局,内流区与外流区的坡度均值分别为6.55°和14.3°,坡长均值分别为122.9,172.2 m,LS均值分别为4.8和12.7;(2)青藏高原LS因子整体受坡度影响,但高原边缘陡峭地区LS因子主要受坡长影响;(3)青藏高原6条主要河流的Hack剖面都呈上凸形态,该地区地貌演化整体上处于幼年期;(4)青藏高原LS因子的分布特征与土壤侵蚀类型及其组合有对应关系:周边地区的高值对应冰川侵蚀—水蚀,西北部的低值对应水力—冻融侵蚀和风蚀,东南部边缘向高原内部过渡地区的较高值对应水力—重力侵蚀。通过分析LS因子的分布格局和统计特征,可为土壤侵蚀学评价提供理论和数据支撑,对于青藏高原地球系统物质迁移转换研究具有重要意义。

山区公路顺层边坡首次失稳长度影响因素及确定方法

西部山区公路建设中常遭遇顺层边坡,其首次失稳长度L_(c)是失稳机制及加固设计的关键参数,现有L_(c)确定方法存在一定局限性。依托31个四川盆周山区公路顺层边坡失稳案例,系统调查坡体结构特征(岩层倾角α、边坡走向与岩层走向的夹角θ和坡长L)及外在灾变诱因(切层厚度D和降雨量Q)对首次失稳长度的特征,并结合数值分析,探讨顺层边坡首次失稳长度的主要影响因子及确定方法,建立更加完善的多因素首次失稳长度的拟合关系式。结果表明:顺层边坡破坏主要发生在θ≤30°范围,坡体双面临空甚至三面临空时,θ>30°的顺层边坡也发生失稳;L_(c)随L的增大而增大,且L_(c)/L等于0.3~1.0;L_(c)/D介于3~24之间,不含软弱夹层时L_(c)/D等于3~10;α在12°~35°时,顺层边坡稳定性最差,且L_(c)/D随α的增大而减小;降雨对顺层边坡的失稳诱发源于软弱夹层的饱水软化,汛期开挖是含软弱夹层顺层边坡失稳的灾变诱因。边坡首次失稳长度影响因子敏感度从大到小排序为:①含软弱夹层边坡:岩层倾角、坡长、切层厚度、内摩擦角、黏聚力、弹性模量、开挖高度;②无软弱夹层边坡:岩层倾角、内摩擦角、切层厚度、黏聚力、坡长。提出的走向夹角折减系数和多因素首次失稳长度计算公式对边坡破坏范围的确定有指导意义。

Assessment of soil erosion in the Irga watershed on the eastern edge of the Chota Nagpur Plateau,India

Human activities to improve the quality of life have accelerated the natural rate of soil erosion.In turn,these natural disasters have taken a great impact on humans.Human activities,particularly the conversion of vegetated land into agricultural land and built-up area,stand out as primary contributors to soil erosion.The present study investigated the risk of soil erosion in the Irga watershed located on the eastern fringe of the Chota Nagpur Plateau in Jharkhand,India,which is dominated by sandy loam and sandy clay loam soil with low soil organic carbon(SOC)content.The study used the Revised Universal Soil Loss Equation(RUSLE)and Geographical Information System(GIS)technique to determine the rate of soil erosion.The five parameters(rainfall-runoff erosivity(R)factor,soil erodibility(K)factor,slope length and steepness(LS)factor,cover-management(C)factor,and support practice(P)factor)of the RUSLE were applied to present a more accurate distribution characteristic of soil erosion in the Irga watershed.The result shows that the R factor is positively correlated with rainfall and follows the same distribution pattern as the rainfall.The K factor values in the northern part of the study area are relatively low,while they are relatively high in the southern part.The mean value of the LS factor is 2.74,which is low due to the flat terrain of the Irga watershed.There is a negative linear correlation between Normalized Difference Vegetation Index(NDVI)and the C factor,and the high values of the C factor are observed in places with low NDVI.The mean value of the P factor is 0.210,with a range from 0.000 to 1.000.After calculating all parameters,we obtained the average soil erosion rate of 1.43 t/(hm^(2)•a),with the highest rate reaching as high as 32.71 t/(hm^(2)•a).Therefore,the study area faces a low risk of soil erosion.However,preventative measures are essential to avoid future damage to productive and constructive activities caused by soil erosion.This study also identifies the spatial distribution of soil erosion rate,which will help policy-makers to implement targeted soil erosion control measures.

基于Slide的研山铁矿高陡边坡稳定性分析

露天矿山边坡稳定性对采场安全生产至关重要。为探究边坡施工过程中的安全隐患,以研山铁矿高陡边坡为研究对象,考虑爆破震动及地震作用荷载,运用Slide二维边坡数值模拟软件对典型剖面进行稳定性计算。结果表明:在正常工况条件、爆破震动及地震作用下,边坡整体安全系数符合要求,整体处于稳定状态。但在爆破震动及地震作用下,边坡局部安全系数介于临界值,可能存在局部滑坡风险。为保证采场生产安全,提出了相应的边坡管理预防措施,为相关实践工作提供一定参考。

A comparison study between 2D and 3D slope stability analyses considering spatial soil variability

In engineering practice,the stability of a slope is often analyzed as a 2D problem assuming a plane-strain condition,which may lead to significant errors.In this paper,a comprehensive study is carried out to compare the results of 2D and 3D slope stability analyses,using the strength reduction method for deterministic analysis and the random field approach for probabilistic analysis,respectively.The results of this comparison study confirm that in the deterministic stability evaluation,the 2D analysis tends to obtain a smaller factor of safety than does its 3D counterpart.In the probabilistic evaluation that considers the spatial variability of soil properties,the 2D analysis tends to yield a larger probability of failure than its 3D counterpart.A significant feature of the 3D probabilistic slope stability analysis is the presence of multiple local failures distributed along the slope longitudinal direction.This paper provides insights regarding the degree of errors in modeling a 3D slope as a 2D problem,which can be regarded as a complement to the previous 3D slope stability analyses.

坡长坡度因子计算工具

地形(坡长坡度)因子是坡面土壤侵蚀模型USLE(通用土壤流失方程)或CSLE(中国水蚀方程)中的重要参数。本文选择了适合我国土壤侵蚀特点的坡长坡度因子计算公式,基于Visual Studio 2010平台进行了程序编写,开发了LS计算工具。该工具界面友好且计算速度快,在32位计算机上可快速计算1万行×1万列数据区域的坡长坡度因子,在64位计算机上能计算4万行×4万列数据区域的坡长坡度因子。本软件的开发可为区域土壤侵蚀评价以及水土保持措施规划服务。

基于GIS的区域坡度坡长因子提取算法

为提高基于地理信息系统的区域土壤侵蚀研究、水土保持环境效应评价、流域水文分析等的应用效率,设计新的坡度坡长(LS)因子算法,利用正向-反向遍历算法取代原累积坡长算法,以获取区域尺度下的LS因子。实验结果表明,在计算精度允许的范围内,新算法使计算机运行效率有较大幅度的提高。

中国主要水蚀典型区侵蚀地形特征分析

地形是影响地表水文和土壤侵蚀的主要环境因素,坡度、坡长和LS因子是土壤侵蚀模型的重要参数。该文以第四次全国土壤侵蚀普查项目为依托,在ANUDEM软件环境中建立25m分辨率文地貌关系正确的DEM(Hydrologically Correct Digital Elevation Model,Hc-DEM),提取了坡度、坡长并计算了LS因子,对中国主要水蚀地区的土壤侵蚀地形因子的空间及统计特征进行了分析,并将该数据与目前应用较为广泛的2种遥感高程数据进行了对比。结果表明,25m分辨率Hc-DEM可用以表达各典型样区地形特征,其上提取的坡度和坡长,符合一般地貌学原理和常规认识;坡度在东北地区最为平缓(0.8°),而在黄土丘陵区最陡(22.3°);坡长则在东北地区最长而黄土丘陵区最短(479m和69m);在地势比较低的河谷和地势较高的分水地带坡度比较平缓,而在分水岭到河谷冲积平原之间坡度较陡;在地形起伏较大的陡坡丘陵或坡度平缓的丘陵,坡长均比较大;LS因子的空间分布格局与坡度基本一致;该文得到的数据与ASTER和SRTM遥感高程数据对比具有明显优势,全国土壤侵蚀普查项目建立的DEM,在全国、省区和大流域尺度上的土壤侵蚀评价制图中具有不可替代性。该文阐明了中国主要水蚀区的侵蚀地形特征,为土壤侵蚀学、水文学中地形因子的提取提供了参考。

基于DEM的流域坡度坡长因子计算方法研究初报

流域尺度的坡度坡长(LS)因子计算是区域土壤侵蚀评价的重要基础。基于坡面水文学和土壤侵蚀学,对流域坡度坡长因子计算的基本原理、方法和工作流程进行了讨论。以黄土丘陵区的安塞县县南沟流域为例,对LS因子进行了实例计算,并对计算结果进行了初步分析,同时提出了目前亟待研究的问题。

微型桩群加固土坡稳定性分析

微型桩是一种边坡快速加固技术,多大面积成群布置。基于强度折减技术研究了微型桩群加固边坡安全系数的数值计算方法,并对微型桩群加固均质土坡和含软弱夹层土坡的稳定性进行了对比分析。结果表明,微型桩群加固均质土坡的破坏模式与其布设位置关系密切,采用传统非耦合方法假定滑动面位置不变进行微型桩群的工程设计值得商榷;对于均质土坡,微型桩群锚固深度较小时,桩身变形以刚性旋转为主,随着锚固深度的增加,微型桩群的变形由刚性倾斜转化为柔性弯曲变形,对于含软弱夹层边坡,微型桩群的变形主要是弯曲变形;微型桩群最优锚固长度约为滑面以上自由段长度的1.5~2.0倍。削剪作用能够改善微型桩群受力并降低成本;对于均质土坡,当削剪长度小于自由段长度1/4时,不会降低加固边坡的安全系数,对于含软弱夹层边坡,最大削剪长度约为自由段长度的1/2;实际工程中对于可削剪的微型桩部分,无需设计加筋体,仅将钻孔回填压实即可,能够在确保加固效果的同时降低成本。

锚杆长度与边坡坡率对最优锚固角的影响

最优锚固角是锚固工程设计中的重要参数,为了探讨锚杆长度和边坡坡率对于锚杆最优锚固角的影响,采用FLAC3D数值方法,建立边坡模型,通过数值计算发现锚杆长度和边坡坡率对最优锚固角影响较大,研究结果表明:1边坡安全系数随锚杆长度的增大呈现先增大后基本保持不变的趋势,存在有效锚固长度,锚杆倾角越大对应的有效锚固长度越小。2边坡安全系数随锚杆倾角的增大呈现先增大后减小的趋势,存在最优锚固角;并且最优锚固角随锚杆长度的增大而线性减小。3当锚杆倾角未达到最优锚固角之前,边坡坡率对安全系数影响较小,而当锚杆倾角达到或者超过最优锚固角,边坡坡率的影响逐渐显现,并且坡率越大所对应的最优锚固角也越大。

抗滑桩设计中的两个问题

文章针对抗滑桩加固边坡设计中抗滑桩内力计算、合理桩长的选择这两个问题,运用有限元强度折减法直接计算抗滑桩所受的滑坡推力、桩身内力、滑面形式,优化锚索的锚固力,使锚索与抗滑桩协调作用。研究不同桩长的抗滑桩加固效果,发现沉埋桩不仅可使边坡达到足够的稳定性,而且沉埋桩所受的滑坡推力降低、桩身内力比全长桩更为合理,在条件许可的情况下沉埋桩可更为有效地加固边坡,这为抗滑桩设计中选择合理桩长的这个问题提供了一个很好的解决方法。

考虑P-Δ效应的陡坡段桥梁双桩结构受力分析

深入分析了陡坡段桥梁桩基受力的P-Δ效应形成机理.依据土压力理论与弹性地基梁理论,通过对坡体剩余下滑力和土体抗力的合理简化,建立了陡坡段桥梁双桩结构体系的桩土相互作用模型.在此基础上,导出不同特征桩段微分方程的幂级数解答,从而提出了一种可考虑P-Δ效应的陡坡段桥梁桩基受力计算方法.与文献算例对比分析表明了该方法的合理性.最后,对双桩结构内力与位移的影响因素及其敏感性进行了探讨,结果表明:前桩P-Δ效应的影响不容忽视,当桩顶荷载水平及地基抗力比例系数相同时,后桩桩身最大弯矩比前桩大,且最大弯矩作用面均位于边坡滑动面附近,陡坡上的桥梁桩基同样具有嵌固深度效应.

锦屏水电站缆机平台高陡边坡开挖支护数值模拟

以锦屏水电站缆机平台高陡边坡为例,采用有限元法对其分级开挖支护过程进行数值模拟计算,分析不同的单级开挖高度、岩体强度参数和支护时间对高陡边坡变形和稳定性的影响。结果表明:边坡的变形、安全系数受岩体强度参数影响较大;较好岩体条件下,单级开挖高度和支护时间对边坡的变形、安全系数影响很小,较差岩体条件下,单级开挖高度和支护时间对边坡的变形、安全系数影响显著,且单级开挖高度越大,支护的作用效果越明显。研究成果可为实际高陡岩石边坡工程开挖支护方案优化和施工提供参考。

车镇北带古近系砂砾岩体储层特征及影响因素分析

通过岩芯观察、薄片鉴定、物性分析、扫描电镜观察等技术手段,研究了车镇凹陷北部陡坡带古近系砂砾岩体储层的主要岩石类型、储集空间类型、物性特征和影响因素。研究结果表明,砂砾岩体岩石学特征具有成分成熟度和结构成熟度低的特点;主要储集空间类型为粒间溶孔和粒内溶孔,微裂缝也具有一定的储集意义;该区砂砾岩体储层物性具有随埋深增加而变差的趋势,且在深部地层中次生孔隙较为发育,影响该区储层物性的因素主要有沉积相、成岩作用以及异常压力,其中沉积相带是控制储层物性的根本性因素。

映秀—卧龙公路沿线汶川地震地质灾害研究

映秀—卧龙公路是汶川地震灾区距震中最近、震害最为严重的一条公路,本文对沿线地震地质灾害进行了详细的调查研究。依据震害特征,将沿线震害划分为斜坡中上部强风化岩体及土层失稳、结构面切割岩体崩滑失稳、滑坡、泥石流等4类,并分析了沿线震害发育规律。调查表明：龙门山后山断裂两侧地震地质灾害呈现显著的差异性,主要是由深大断裂的消震隔震效应,地貌放大效应,地质结构等三方面因素决定的。通过134条实测剖面分析,研究了地震失稳斜坡坡度和失稳部位。地震诱发失稳斜坡坡度在33°~84°之间,主要分布在41°~65°之间,可以认为地震诱发斜坡失稳灾害主要发生在40°以上的斜坡。斜坡失稳部位主要分布在斜坡中上部以及地貌突出部位,主要失稳部位在0.4坡高以上。从研究斜坡动力失稳的角度,将沿线斜坡划分为基岩-土层及强风化层斜坡地质结构、不利外倾结构面基岩斜坡地质结构、块状构造基岩斜坡地质结构、块碎石土层斜坡地质结构等几种地质结构模型,分析论述了各种地质结构相应的地震地质灾害类型及特点。