陕南地区膨胀土滑坡形成机理及防治措施     

刘海南  李永红  贺卫中  向茂西  姬怡微 《地质灾害与环境保护》2014,(3):20-24

以陕西省南部汉台区地质灾害详细调查项目为依托,通过对汉王镇红星村三、四组滑坡的勘查,发现汉台地区膨胀土滑坡的形成与区内自然地理、地形地貌、地层岩性、降水、地表水和人类工程活动密切相关。研究提出以排水工程、支挡工程和地基换填为主的综合防治措施,为汉台区地方政府地质灾害的防治、减灾工作提供依据,在陕南地区具有一定的推广意义。  相似文献   

A constitutive model for unsaturated soils with consideration of inter-particle bonding     

《Computers and Geotechnics》2014

The paper presents a physically-based constitutive model for unsaturated soils that considers the bonding effect of water menisci at inter-particle contacts. A bonding factor has been used to represent the magnitude of the equivalent bonding stress, defined as the bonding force per unit cross-sectional area. The average skeleton stress is employed to represent the effect of average fluid pressures within soil pores. Based on an empirical relationship between the bonding factor ζ and the ratio e/e_s (where e and e_s are void ratios at unsaturated and saturated states, respectively, at the same average skeleton stress), we propose an elasto-plastic constitutive model for isotropic stress states, and then extend this model to triaxial stress states within the framework of critical state soil mechanics. Because only one yield surface is needed in the proposed model, a relatively small number of parameters are required. Comparisons between experimental data and model results show that, in most cases, the proposed model can reasonably capture the important features of unsaturated soil behavior.  相似文献   

Discrete modeling of strain accumulation in granular soils under low amplitude cyclic loading     

《Computers and Geotechnics》2014

An advanced understanding of the strain accumulation phenomenon in granular soils subjected to low amplitude cyclic loading with relatively high frequency is needed to enhance the ability to predict the settlement of granular soils induced by vibrations. In the current study, the discrete element method is used to study this phenomenon. A loose and a medium dense sample composed of a relatively large number of spheres are considered. A series of stress controlled cyclic triaxial tests with different excitation amplitudes and frequencies is performed on these samples at different static stress states. The response of these samples at the macroscopic and microscopic scales is analyzed. The sample density, the cyclic stress amplitude and the static stress state importantly affect strain accumulation. However, the cyclic excitation frequency has a small effect on strain accumulation. At the microscopic scale, frictional sliding occurring at a few contacts continuously dissipates energy and the fraction of these contacts varies periodically during cyclic loading. The coordination number of these samples increases slightly as strain accumulates. However, the anisotropy remains almost constant during low amplitude cyclic excitation. A qualitatively good agreement between numerical and experimental results is found.  相似文献   

不同压实度荆门弱膨胀土的一维膨胀-压缩特性   总被引：1，自引：0，他引：1  

周葆春  张彦钧  汤致松 《岩土力学》2014,35(5):1275-1283

为探讨压实膨胀土的体变行为,以荆门弱膨胀土为研究对象,借助高压固结仪对6种制样压实度下的膨胀土试样进行了一维无荷载膨胀和含一次卸载-再加载循环的压缩试验。基于膨胀试验结果,构建了膨胀时程方程,通过参数分析,明确了方程参数的物理意义,并建议了膨胀时程曲线3阶段的划分方法。基于压缩试验结果,探讨了固结屈服应力、压缩指数Cc、回弹指数Cs、膨胀力与制样压实度、土体结构性、膨胀势、孔隙比的相关关系。试验结果及其分析表明,膨胀土体积变化是膨胀势与外部荷载、湿度变化的耦合作用结果,且具有强烈的水-力路径依赖性。  相似文献   

基于机器学习模型的区域土壤重金属空间预测精度比较研究     

金昭  吕建树 《地理研究》2022,41(6):1731-1747

为识别区域土壤重金属的空间变异特征并厘清其影响因素,本研究构建了多元线性回归（MLR）、弹性网络回归（ENR）、随机森林（RF）、随机梯度提升（SGB）、堆叠（stacking）集成模型、反向传播神经网络（BP-ANN）、基于模型平均的神经网络集成（avNNet）、线性核支持向量机（SVM-L）和高斯核支持向量机（SVM-R）共九种机器学习模型,利用山东省中部土壤重金属（Cd、Cu、Hg、Pb和Zn）和环境辅助变量数据,开展区域土壤重金属空间预测精度比较研究。结果表明：RF对五种重金属空间预测的决定系数（R²）介于0.263~0.448之间,平均绝对误差（MAE）和均方根误差（RMSE）分别小于8.408和10.636,预测值/实际值（P/O）均接近于1,对五种重金属的预测效果均较为理想,是研究区土壤重金属空间预测的最优模型;SVM-R整体预测性能仅次于RF,各项精度评价指标均相对稳健,可作为备选模型;其余七种模型的预测性能均明显低于RF和SVM-R。RF的空间预测结果显示,研究区五种重金属呈现出相似的空间分布格局,含量均由研究区东北部向西南部递减,包括东北部、北部和南部3个高值区,且高值区与当地工业–交通密集区的分布格局一致,反映出人类活动是研究区土壤重金属空间分异的主要影响因素。本研究可为区域土壤污染调查、评价和管控提供科学参考。  相似文献   

Using modified state surface approach to select parameter values in the Barcelona basic model     

Xiong Zhang  Ming Xiao 《国际地质力学数值与分析法杂志》2013,37(12):1847-1866

The Barcelona basic model (BBM) successfully explained many key features of unsaturated soils and received extensive acceptance. It is also one of the few elastoplastic constitutive models for unsaturated soils that have been implemented within finite element codes and applied to the analysis of real boundary value problems. The BBM was proposed in incremental forms according to theories of soil plasticity in which individual aspects of the isotropic virgin behavior are controlled by multiple parameters, whereas at the same time, a single parameter controls more than one aspect of soil behavior. Although a variety of methods have been recently developed for calibrating model parameters for elastoplastic soil models, at present, there are no well‐established, simple, and objective methods for selecting parameter values in the BBM from laboratory tests. This has been one of the major obstacles to the dissemination of this constitutive model beyond the research context. This article presents an optimization approach especially developed for simple and objective identification of material parameters in the BBM. This is achieved by combining a modified state surface approach, recently proposed to model the elastoplastic behavior of unsaturated soils under isotropic stress conditions, with the Newton or quasi‐Newton method to simultaneously determine the five parameters governing isotropic virgin behavior in the BBM. The comparison between results using the proposed method and an existing method for the same laboratory tests was discussed from which the simplicity and objectivity of the proposed method were evaluated. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Analysis of the FEBEX multi‐barrier system including thermoplasticity of unsaturated bentonite     

Fabrice Dupray  Bertrand François  Lyesse Laloui 《国际地质力学数值与分析法杂志》2013,37(4):399-422

Deep geological repository involving a multibarrier system constitutes one of the most promising options for isolating high‐level radioactive waste from the human environment. To certify the efficiency of waste isolation, it is essential to understand the behaviour of confining geomaterial under a variety of environmental conditions. To this end, results from a near‐to‐real experiment, the full‐scale engineered barriers in situ experiment, are studied by means of a thermo–hydro–mechanical finite element approach, including a consistent thermoplastic constitutive model for unsaturated soils. Laboratory tests are simulated to calibrate model parameters. The results of the numerical simulations are compared with sensor measurements and show the ability of the model to reproduce the main behavioural features of the system. The influence of the hysteretic and temperature‐dependent retention of water on the mechanical response is exhibited. Finally, those results are interpreted in the light of thermoplasticity of unsaturated soils, which reveals the highly coupled and non‐linear characters of the processes encountered. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Microtopography,water storage and flow patterns in a fine‐textured soil under agricultural use     

Christina Bogner  Mohammadreza Mirzaei  Stéphane Ruy  Bernd Huwe 《水文研究》2013,27(12):1797-1806

Agricultural use of soils implies tillage and often compaction and therefore influences processes on soil surface and affects infiltration of water into the subsoil. Although many studies on soil surface processes or flow patterns in soils exist, works relating both are rare in literature. We did two tracer experiments with Brilliant Blue FCF on a tilled and compacted plot and a non‐tilled one to investigate water storage on the soil surface during simulated rainfall and changes of soil microtopography, to analyse the associated flow patterns in the soil and to relate both to tillage and compaction. Our results show that storage was larger on the tilled and compacted plot than on the non‐tilled one. After tillage, transport processes above the plough pan were partly disconnected from those underneath because macropores were disrupted and buried by the tillage operation. However, preferential flow along cracks occurred on both plots and the macropores buried below the tillage pan still functioned as preferential flow paths. Therefore, we conclude that the studied soil is susceptible to deep vertical solute propagation at dry conditions when cracks are open, irrespective of tillage and compaction. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A Generalized Backward Euler algorithm for the numerical integration of an isotropic hardening elastoplastic model for mechanical and chemical degradation of bonded geomaterials     

Claudio Tamagnini  Riccardo Castellanza  Roberto Nova 《国际地质力学数值与分析法杂志》2002,26(10):963-1004

An extended version of the classical Generalized Backward Euler (GBE) algorithm is proposed for the numerical integration of a three‐invariant isotropic‐hardening elastoplastic model for cemented soils or weak rocks undergoing mechanical and non‐mechanical degradation processes. The restriction to isotropy allows to formulate the return mapping algorithm in the space of principal elastic strains. In this way, an efficient and robust integration scheme is developed which can be applied to relatively complex yield surface and plastic potential functions. Moreover, the proposed algorithm can be linearized in closed form, thus allowing for quadratic convergence in the global Newton iteration. A series of numerical experiments are performed to illustrate the accuracy and convergence properties of the algorithm. Selected results from a finite element analysis of a circular footing on a soft rock layer undergoing chemical weathering are then presented to illustrate the algorithm performance at the boundary value problem level. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

南宁膨胀土持水性能的温度效应及微观机制     

曾召田  崔哲旗  孙德安  姚志  潘斌 《岩土力学》2023,(8):2177-2185

采用蒸汽平衡法测定了4种温度(T=5、25、40、60℃)条件下Whatman No.42滤纸的率定曲线,建立了考虑温度影响的双线性率定曲线方程,发现滤纸的持水性能随温度升高而降低,且温度对率定曲线高吸力段滤纸持水性能的影响要弱于低吸力段。在此基础上,以南宁膨胀土为研究对象,使用滤纸法测定了不同温度作用下膨胀土试样的土-水特征曲线。试验结果表明,随着温度的升高,膨胀土持水性能下降,但温度的影响幅度会随着吸力的增大而减弱,当基质吸力达到40MPa时,不同温度下试样的体积含水率并没有明显变化,即此时温度对膨胀土的持水性能变化几乎无影响。为解释上述宏观现象,选取部分试样进行了压汞试验和吸附结合水试验,并根据试验结果从土体中各相及各相界面相互耦合作用的物理机制角度阐述了南宁膨胀土持水性能的温度效应及微观机制。  相似文献