Multivariate analysis of soil moisture history for a hillslope     

Sanghyun Kim   《Journal of Hydrology》2009,374(3-4):318-328

In this study, the spatial distribution of measured soil moisture was analyzed on the platform of multivariate modeling. Soil moisture time series for two seasons were selected and used for analysis to reveal similarities and differences in soil moisture responses for a few rainfall events. The development of a soil moisture transport process that considers the representative element volume and uncertainty of soil media provides the hydrological basis for time series modeling. The systematic procedure of Box–Jenkins with noise modeling was used to delineate the final models for all monitoring points. The physical basis of mass balance and the continuity in inflow contribution, as well as statistical criteria, were used in the model selection procedure. Heuristic approaches provide the spatial distribution of selected models along the transect of a hillside. Comparative analysis for two different depths and seasons provide an understanding of the variation in soil moisture transfer processes at the hillslope scale. Differences in soil moisture models for both depths and seasons are associated with eco-hydrological processes. The relationships between distributed topographic features and modeling results were explored to configure dominant hydrological processes for each season.  相似文献   

Static and seismic bearing capacity of shallow strip footings     

《Soil Dynamics and Earthquake Engineering》2016

In this study, the evaluation of static and seismic bearing capacity factors for a shallow strip footing was carried out by using the method of characteristics, which was extended to the seismic condition by means of the pseudo-static approach. The results, for both smooth and rough foundations, were checked against those obtained through finite element analyses.Under seismic conditions the three bearing capacity problems for N_c, N_q and N_γ were solved independently and the seismic bearing capacity factors were evaluated accounting separately for the effect of horizontal and vertical inertia forces arising in the soil, in the lateral surcharge and in the superstructure.Empirical formulae approximating the extensive numerical results are proposed to compute the static values of N_γ and the corrective coefficients that can be introduced in the well-known Terzaghi׳s formula of the bearing capacity to extend its applicability to seismic design of foundations.  相似文献   

Major advances in liquefaction research by laboratory tests compared with in situ behavior     

《Soil Dynamics and Earthquake Engineering》2016

Major advances in liquefaction research in the laboratory to understand the basic mechanisms in comparison with in situ behavior during previous earthquakes are reviewed. Then, several issues related to liquefaction triggering and post-liquefaction deformation are selected for further discussion in the author's perspective. These include effects of fines associated with aging, effects of gravels, effects of initial shear stress, and lateral spreading and lateral flow due to void redistribution. It has been disclosed that a quite a few issues still remain to be settled in evaluating liquefaction onset and post-liquefaction deformations for improving engineering design, particularly for Performance-Based Design (PBD).  相似文献   

郯庐断裂带安徽段土壤气体的地球化学特征   总被引：3，自引：0，他引：3  

郑海刚  方震  周晓成  李军辉  孙玉涛  李玲利 《中国地震》2016,32(4):642-652

在郯庐断裂带安徽段由北向南分别于泗县、明光、肥东、桐城布设了4个测区,每个测区各布设了4条跨断层土壤气测量剖面,测量土壤气Rn、Hg和CO_2的浓度。根据16条跨断层土壤气剖面的测量结果,对郯庐断裂带安徽段的3种土壤气体的释放特征及其与断层空间位置间的关系进行了初步分析。结果表明,气体在断裂带附近较为富集,对断层位置有一定指示作用;气体的富集程度与断裂的活动性、该区段断层岩性及地质环境有一定关系。该结果对于认识测量区域气体的积累特征及构造地球化学研究有一定意义。  相似文献   

Intercomparison of the JULES and CABLE land surface models through assimilation of remotely sensed soil moisture in southeast Australia     

《Advances in water resources》2014

Numerous land surface models exist for predicting water and energy fluxes in the terrestrial environment. These land surface models have different conceptualizations (i.e., process or physics based), together with structural differences in representing spatial variability, alternate empirical methods, mathematical formulations and computational approach. These inherent differences in modeling approach, and associated variations in outputs make it difficult to compare and contrast land surface models in a straight-forward manner. While model intercomparison studies have been undertaken in the past, leading to significant progress on the improvement of land surface models, additional framework towards identification of model weakness is needed. Given that land surface models are increasingly being integrated with satellite based estimates to improve their prediction skill, it is practical to undertake model intercomparison on the basis of soil moisture data assimilation. Consequently, this study compares two land surface models: the Joint UK Land Environment Simulator (JULES) and the Community Atmosphere Biosphere Land Exchange (CABLE) for soil moisture estimation and associated assessment of model uncertainty. A retrieved soil moisture data set from the Soil Moisture and Ocean Salinity (SMOS) mission was assimilated into both models, with their updated estimates validated against in-situ soil moisture in the Yanco area, Australia. The findings show that the updated estimates from both models generally provided a more accurate estimate of soil moisture than the open loop estimate based on calibration alone. Moreover, the JULES output was found to provide a slightly better estimate of soil moisture than the CABLE output at both near-surface and deeper soil layers. An assessment of the updated membership in decision space also showed that the JULES model had a relatively stable, less sensitive, and more highly convergent internal dynamics than the CABLE model.  相似文献   

Comprehensive three dimensional finite element analysis,parametric study and sensitivity analysis on the seismic performance of soil–micropile-superstructure interaction     

《Soil Dynamics and Earthquake Engineering》2014

A comprehensive dynamic three dimensional finite element model, which includes the effect of lots of important parameters on the micropiles seismic performance, has been presented. The validation of the built model has been carried out using remodeling a single degree of freedom shaking table test done by Mc Manus at the University of Canterbury. The gained results proved the accuracy of the constructed model. Then, using the parametric analysis, effects of all the earthquake characteristics, soil properties, superstructure and micropiles' cap and micropiles structure on the seismic performance of micropiles have been investigated by means of presenting internal forces and displacements which occurred as the main result of earthquake. Furthermore, using the data analysis, the most and the least influential parameters on internal forces are obtained based on the Cosine Amplitude Method (CAM).  相似文献   

Simulation of soil–foundation–structure interaction of Hualien large-scale seismic test using dynamic centrifuge test     

《Soil Dynamics and Earthquake Engineering》2014

Understanding the soil–structure interaction (SSI) mechanism is crucial in the seismic design of nuclear power plant (NPP) containment systems. Although the numerical analysis method is generally used in seismic design, there is a need for experimental verification for the reliable estimation of SSI behavior. In this study a dynamic centrifuge test was performed to simulate the SSI behavior of a Hualien large-scale seismic test (LSST) during the Chi-Chi earthquake. To simulate the soil profile and dynamic soil properties of the Hualien site, a series of resonant column (RC) tests was performed to determine the model soil preparation conditions, such as the compaction density and the ratio of soil–gravel contents. The variations in the shear wave velocity (V_S) profiles of the sand, gravel, and backfill layers in the model were estimated using the RC test results. During the centrifuge test, the V_S profiles of the model were evaluated using in-flight bender element tests and compared with the in-situ V_S profile at Hualien. The containment building model was modeled using aluminum and the proper scaling laws. A series of dynamic centrifuge tests was performed with a 1/50 scale model using the base motion recorded during the Chi-Chi-earthquake. In the soil layer and foundation level, the centrifuge test results were similar to the LSST data in both the time and frequency domains, but there were differences in the structure owing to the complex structural response as well as the material damping difference between the concrete in the prototype and aluminum in the model. In addition, as the input base motion amplitude was increased to a maximum value of 0.4g (prototype scale), the responses of the soil and containment model were measured. This study shows the potential of utilizing dynamic centrifuge tests as an experimental modeling tool for site specific SSI analyses of soil–foundation–NPP containment system.  相似文献   

Effects of soil–structure interaction on seismic base isolation     

《Soil Dynamics and Earthquake Engineering》2014

The effects of soil–structure interaction on the performance of a nonlinear seismic base isolation system for a simple elastic structure are examined. The steady-state response of the system to harmonic excitation is obtained by use of the equivalent linearization method. Simple analytical expressions for the deformation of the base isolation system and of the superstructure at resonance are obtained in terms of an effective replacement oscillator characterized by amplitude-dependent frequency, damping ratio, and excitation. Numerical results suggest that the seismic response of a structure resting on an inelastic base isolation system may be larger when the flexibility of the soil is considered than the corresponding response obtained by ignoring the effects of soil–structure interaction. It is shown that, in the undamped case and in the absence of soil–structure interaction effects, a critical harmonic excitation exists beyond which the steady-state resonant response of the isolators and structure become unbounded.  相似文献   

Effect of preloading on the amplification characteristics of soil profiles     

《Soil Dynamics and Earthquake Engineering》2014

Preloading is a temporary loading, usually an embankment, applied to improve subsurface soils by densification. This paper studies the effect of preloading on the amplification characteristics of soft sites with an elaborate parametric analysis. The soil type, the depth of the bedrock, the water table depth, the level of preloading, the applied earthquake, the shear wave velocity of the bedrock and the shear modulus and damping versus shear strain relations were varied in a systematic manner. The analysis was performed by the commonly used one-dimensional equivalent-linear dynamic method. The shear wave velocity versus depth and the effect of preloading on shear velocity are computed with well-established soil mechanics equations. The results illustrated that the seismic response at the top of the profile generally decreases as a result of preloading. A more detailed analysis of results shows that the effect of preloading on the seismic response depends on the soil type and the depth of the bedrock. Based on these results, a method is proposed by which a practicing engineer involved with improvement of soft ground can simulate the effect of preloading on the seismic motion.  相似文献   

Simplified methods in Soil Dynamics     

《Soil Dynamics and Earthquake Engineering》2014

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