Rainfall thresholds for shallow landsliding derived from pressure‐head monitoring: cases with permeable and impermeable bedrocks in Boso Peninsula,Japan     

Yuki Matsushi  Yukinori Matsukura 《地球表面变化过程与地形》2007,32(9):1308-1322

Rainfall thresholds for shallow landslide initiation were determined for hillslopes with two types of bedrock, permeable sandstone and impermeable mudstone, in the Boso Peninsula, Japan. The pressure‐head response to rainfall was monitored above a slip scarp due to earlier landslides. Multiple regression analysis estimated the rainfall thresholds for landsliding from the relation between the magnitude of the rainfall event and slope instability caused by the increased pressure heads. The thresholds were expressed as critical combinations of rainfall intensity and duration, incorporating the geotechnical properties of the hillslope materials and also the slope hydrological processes. The permeable sandstone hillslope has a greater critical rainfall and hence a longer recurrence interval than the impermeable mudstone hillslope. This implies a lower potential for landsliding in sandstone hillslopes, corresponding to lower landslide activity. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

用置换法处理桩端沉碴     

吴敏艳  肖尚惠 《南方国土资源》2001,14(3):76-78

文章对超出规范规定范围内的桩端沉碴提出用置换法处理的技术方法 ,取得显著效果 ,克服了传统处理方法强度小等缺点 ,也避免了采用跨越处理工期长、造价高的不良后果。  相似文献   

Setting minimum head capsule abundance and taxa deletion criteria in chironomid-based inference models   总被引：6，自引：0，他引：6  

Roberto Quinlan  John P. Smol 《Journal of Paleolimnology》2001,26(3):327-342

Criteria for removing training set lakes and taxa in chironomidbased inference models, due to low abundances, have largely been ad hoc. We used an anoxia inference model and a hypolimnetic oxygen model from southcentral Ontario to determine what effect subfossil head capsule abundance and taxa deletion criteria have on fossil inference statistics. Results from six training set lakes suggest that a minimum abundance of 40–50 head capsules is sufficient for use in inference models, however more diverse samples likely require more than 50 head capsules. Taxa deletion criteria substantially improved the predictive ability of inference models (lowered the root mean squared error of prediction (RMSEP)). The common practice of including taxa with only 2% abundance in at least two lakes was one of the deletion criteria that much improved inference models. Similar deletion criteria, such as 2% in at least 3 lakes and 3% in at least 1 lake, produced comparable improvements (up to 18% reduction in RMSEP).  相似文献   

Unsteady source flow in weakly heterogeneous porous media     

Peter Indelman 《Computational Geosciences》2000,4(4):351-381

Average nonuniform flows in heterogeneous formations are modeled with the aid of the nonlocal effective Darcy's law. The mean head for flow toward source of instantaneous discharge in a heterogeneous medium of given statistics represents the fundamental solution of the average flow equation and is called the Mean Green Function (MGF). The general representation of the MGF is obtained for weakly heterogeneous formations as a functional of the logconductivity correlation function. For Gaussian logconductivity correlation, the MGF is derived in terms of one quadrature in time t and it is analyzed for isotropic media of any dimensionality d and for 3D axisymmetric formations. The MGF is further applied to determining the mean head distribution for flow driven by a continuous source of constant discharge. The large time asymptotic of the mean head is analyzed in details.  相似文献   

高水头下深厚覆盖层高土石围堰应力变形分析     

汪明元  陈敬虞  孙常青  陈云 《岩土力学》2006,27(Z2):485-490

乌东德水电站位于长江上游的金沙江,其土石围堰高74 m,河床砂卵石覆盖层厚70 m,上下游水头差达151 m,且设计在下游侧堰脚开挖70 m深的基坑,拟采用高86 m的混凝土防渗墙上接复合土工膜防渗。对该高水头下深厚覆盖层高土石围堰的应力变形特征进行了非线性有限元分析,模拟了堰体填筑、蓄水、下游侧降水与基坑开挖的过程,采用无厚度Goodman单元模拟堰体与防渗墙间的接触面。应力与变形分析的结果表明围堰的设计方案是可行的。此外,研究了覆盖层与围堰填料的参数,防渗墙的材料、厚度与墙底沉渣等因素的影响,对设计方案提出了建议。  相似文献   

紧邻边坡建筑物基础软托换及边坡喷锚网加固技术     

肖春喜  张华  刘泉声 《岩土力学》2004,25(5):835-838

详细地介绍了采用花管注浆的软托换技术,对紧邻边坡的建筑物地基进行加固处理,对开挖的边坡采取喷锚网结构支护这一技术在工程中的加固机理。实践表明,花管注浆联合喷锚网支护这种复合的加固方法,不仅能对紧邻边坡的建筑物的基础进行托换,还能对边坡进行有效地支护,保证了边坡的稳定性和建筑物的安全性,其设计方法具有一定的参考价值。  相似文献   

悬臂排桩支护结构空间变形分析   总被引：9，自引：2，他引：7  

许锡昌  陈善雄  徐海滨 《岩土力学》2006,27(2):184-188

以矩形基坑悬臂排桩支护结构为研究对象,通过分析现场实测数据和数值计算,归纳出了冠梁和支护桩的空间变形模式,建立了整个支护系统的能量表达式。利用最小势能原理,推导了基坑中部桩顶最大位移的解析解,分析了各主要支护参数对该位移的影响。研究结果表明,桩顶最大位移随坡顶超载和桩间距的增大基本呈线性增大趋势;当嵌固深度系数逐渐增大时,桩顶最大位移也逐渐增大,但趋势渐缓;基坑长度对其影响也较大,当基坑长度超过一定数值后,最大位移值趋于稳定。最后利用所得的研究成果对某基坑进行了验证,并与现场实测结果进行了对比,计算结果能够满足工程要求。  相似文献   

水库蓄水对库底沉降影响的数值分析   总被引：1，自引：0，他引：1  

王俊杰  朱俊高  王克东  徐建荣 《岩土力学》2005,26(10):1591-1596

抽水蓄能电站常采用沥青混凝土进行库底防渗护面处理,过快的蓄水速率和过大的蓄水水头可能导致库底护面开裂。以某抽水蓄能电站的上水库为例,用考虑Biot固结理论的平面有限元法,在依据沉降观测点实测资料优化确定地基土模型参数的基础上,分析了水库蓄水速率和蓄水水头对库底沉降量、沉降率及库底沥青混凝土应变率的影响。结果表明,蓄水速率对地基的最终沉降值影响不明显,而在蓄高水位历时内,地基的沉降增量和最大沉降率均与蓄水速率和蓄水水头有很好的相关性,沥青混凝土的最大应变率仅与蓄水速率相关。  相似文献   

A comparison between the single ring pressure infiltrometer and simplified falling head techniques          下载免费PDF全文

V. Bagarello  G. Baiamonte  M. Castellini  S. Di Prima  M. Iovino 《水文研究》2014,28(18):4843-4853

Testing the relative performances of the single ring pressure infiltrometer (PI) and simplified falling head (SFH) techniques to determine the field saturated soil hydraulic conductivity, K_fs, at the near point scale may help to better establish the usability of these techniques for interpreting and simulating hydrological processes. A sampling of 10 Sicilian sites showed that the measured K_fs was generally higher with the SFH technique than the PI one, with statistically significant differences by a factor varying from 3 to 192, depending on the site. A short experiment with the SFH technique yielded higher K_fs values because a longer experiment with the PI probably promoted short‐term swelling phenomena reducing macroporosity. Moreover, the PI device likely altered the infiltration surface at the beginning of the run, particularly in the less stable soils, where soil particle arrangement may be expected to vary upon wetting. This interpretation was supported by a soil structure stability index, SSI, and also by the hydraulic conductivity data obtained with the tension infiltrometer, i.e. with a practically negligible disturbance of the sampled soil surface. In particular, a statistically significant, increasing relationship with SSI and an unsaturated conductivity greater than the saturated one were only detected for the K_fs data obtained with the PI. The SFH and PI techniques should be expected to yield more similar results in relatively rigid porous media (low percentages of fine particles and structurally stable soils) than in soils that modify appreciably their particle arrangement upon wetting. The simultaneous use of the two techniques may allow to improve K_fs determination in soils that change their hydrodynamic behaviour during a runoff producing rainfall event. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

A coupled one‐dimensional viscoelastic–plastic model for aquitard consolidation caused by hydraulic head variations in aquifers          下载免费PDF全文

T.‐L. Tsai 《水文研究》2015,29(22):4779-4793

Accurate and practical calculation of aquitard consolidation is required for a reliable analysis of land subsidence caused by groundwater overexploitation in a multilayered aquifer system because aquitards are generally more compressible than aquifers are. This study proposes a coupled one‐dimensional viscoelastic–plastic consolidation model that considers the combined effect of changes in soil parameters and body force to simulate aquitard consolidation caused by hydraulic head variations in neighbouring aquifers. The proposed model uses variable total stress and simultaneously solves hydraulic head and vertical soil displacement. The constitutive relation based on the Voigt model with different elastic moduli of the spring in normally consolidated and overconsolidated soils is used to describe the viscoelastic–plastic deformation mechanism of aquitards. In addition, the proposed model considers the combined effect of variations in hydraulic conductivity, elastic moduli, and body force on the calculation of aquitard consolidation. Three hypothetical scenarios with various hydraulic head variations in aquifers are used to examine the coupled one‐dimensional viscoelastic–plastic consolidation model. The results show that neglecting plasticity and viscosity of soil causes aquitard consolidation to be respectively underestimated and overestimated. In addition, ignoring body force variation underestimates aquitard consolidation, whereas neglecting soil parameters variation overestimates aquitard consolidation. Two real case scenarios are also studied to further demonstrate the applicability of the coupled one‐dimensional viscoelastic–plastic consolidation model. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献