共查询到20条相似文献，搜索用时 31 毫秒
1.
冻土水热耦合模型数值求解及结果检验 总被引：1，自引：0，他引：1
首先对作者所建立的基于多孔介质理论的季节冻土水热迁移耦合模型进行数值求解;对模型方程进行修正, 并给出了模型方程中参数的确定方法。然后以长春松原公路段土体为研究对象, 对实际工程中冻结情况下水分迁移的情况进行预测;给定模型边界条件对模型求解, 将结果与野外实际监测结果进行对比。温度变化对比数据表明, 模型可以较好地预测终值情况, 而中间过程的误差较大, 但是趋势基本一致。水分迁移方向及量的对比数据表明, 模型计算结果要小于实测结果, 但是整体上计算结果与实测结果的变化趋势较一致, 且同样是和最终值吻合较好, 误差最小。结果表明, 模型计算结果可较好地模拟参数最终值, 但存在一定误差。 相似文献
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利用多元逐步回归分析法,结合Landsat8 OLI遥感数据对该地区土壤有机碳进行定量反演.试验采集了164个土壤样品,通过3倍标准差准则对样品进行奇异点去除及数据集划分,其中120个样品作为训练集,44个样品作为验证集,建立土壤有机碳的多元逐步回归预测模型.结果表明：有机碳与Landsat8各波段反射率均显著相关;黑土有机碳光谱预测最优模型以倒数为自变量模型最优,决定系数R2=0.180,均方根误差RMSE=0.558,海伦地区适于Corg含量遥感反演,预测模型稳定性好,可以用于揭示黑土典型区Corg含量的空间分布特征.同时认为在不对土壤进行地面光谱测试的情况下,直接采用化学分析数据与遥感卫星相关联的方法预测模型拟合度有限,光谱对有机碳可解释性较低. 相似文献
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应用主成分分析法研究渗透介质的渗透稳定问题 总被引：2，自引：0，他引：2
结合国内多个水电工程的大量渗透试验数据，在多维系统中选择了5项指标：干密度、孔隙比、不均匀系数、渗透系数和临界坡降，采用多元统计中的主成分分析法进行聚类，运用回归分析建立了砂性土、砂卵石土、断层带物质三类渗透介质的渗透模型。将所建立的断层带物质渗透模型应用到单薄山梁断层带的渗透稳定分析预测上，得到了模型计算结果与渗透试验所得结果相一致的结论，说明主成分分析法在渗透稳定分析中具有一定的适用性。 相似文献
5.
探地雷达技术对表层岩溶带典型剖面组构刻画与界面识别 总被引：1，自引：0，他引：1
表层岩溶带是岩溶研究的重要对象,以往研究以剖面调查半定量为主,文章利用探地雷达属性技术对其发育情况进行定量研究。选取3个表层岩溶带的典型剖面（浅裂隙土、深裂隙土、厚土层覆盖）,并采集探地雷达数据,通过提取相干体属性和均方根振幅属性来挖掘雷达数据中的潜在信息,用于区分介质组构和识别发育深度界面。结果表明,均方根振幅属性较好地区分出了浅裂隙土型和深裂隙土型的岩土介质,厚土层覆盖型的犁耕层与非犁耕层土壤介质;相干体属性能较好地识别出表层岩溶带和下部完整基岩,定量化其发育厚度。 相似文献
6.
Current studies have focused on selecting constitutive models using optimization methods or selecting simple formulas or models using Bayesian methods. In contrast, this paper deals with the challenge to propose an effective Bayesian-based selection method for advanced soil models accounting for the soil uncertainty. Four representative critical state-based advanced sand models are chosen as database of constitutive model. Triaxial tests on Hostun sand are selected as training and testing data. The Bayesian method is enhanced based on transitional Markov chain Monte Carlo method, whereby the generalization ability for each model is simultaneously evaluated, for the model selection. The most plausible/suitable model in terms of predictive ability, generalization ability, and model complexity is selected using training data. The performance of the method is then validated by testing data. Finally, a series of drained triaxial tests on Karlsruhe sand is used for further evaluating the performance. 相似文献
7.
Taicheng An Hui Chen Huiying Zhan Kun Zhu Ronny Berndtsson 《Environmental Geology》2005,47(4):467-474
A laboratory study was executed to investigate the effect of surfactants to enhance sorption of polycyclic aromatic hydrocarbon (PAH) contaminants in loess soil. Phenanthrene and naphthalene were chosen as organic contaminant indicators in loess soil modified by the cation surfactant hexadecyltrimethylammonium (HDTMA) bromide. The kinetic behavior of sorption during transport in natural and modified loess soil was studied. The results indicated that sorption rate in the cation surfactant modified loess soils was at least 3 times faster than that of the natural soil. A first-order kinetics model fitted the sorption data well for both soils. The sorption rates of the two organic compounds were related to their primary residual quantity on the soils. The experiments showed that sorption amounts approached constant values approximately within 30 and 90 min for naphthalene and phenanthrene at 298–318 K, respectively. The rate constants, however, displayed negative correlation with increasing temperature. With changing temperature, the activation energy was calculated at –6.196–1.172 kJ/mol for naphthalene and –28.86–15.70 kJ/mol for phenanthrene at 298–318 K. The results can be used to predict the sorption kinetics of phenanthrene and naphthalene in loess soils, and in a wider perspective, be used to better understand the transport of petroleum contaminants in the soil environment. 相似文献
8.
This paper presents an efficient Bayesian back-analysis procedure for braced excavations using wall deflection data at multiple points. Response surfaces obtained from finite element analyses are adopted to efficiently evaluate the wall responses. Deflection data for 49 wall sections from 11 case histories are collected to characterize the model error of the finite element method for evaluating the deflections at various points. A braced excavation project in Hang Zhou, China is chosen to illustrate the effectiveness of the proposed procedure. The results indicate that the soil parameters could be updated more significantly for the updating that uses the deflection data at multiple points than that only uses the maximum deflection data. The predicted deflections from the updated parameters agree fairly well with the field observations. The main significance of the proposed procedure is that it improves the updating efficiency of the soil parameters without adding monitoring effort compared with the traditional method that uses the maximum deflection data. 相似文献
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内陆河高寒山区流域分布式水热耦合模型（Ⅲ）：MM5嵌套结果 总被引：3，自引：4，他引：3
利用中尺度气候模式MM5计算黑河山区流域2003年2月11日到6月30日的日降水量、2.0 m高度的日平均气温和潜热，并将其嵌套到DWHC模型中。MM5运行周期为10 d，积分步长为3 s，空间分辨率为3 km。保持DWHC模型土壤参数、植被参数、经验参数和可调参数等不变，仅对模型初始参数进行了调整，利用最近距离法（nearest）将MM5输出结果插值到1 km×1 km格点上，所计算的黑河干流出山口日平均流量与实测序列的NSE＝0.79，B＝-0.79（％），EV＝0.79，R2＝0.81。利用基于三角网格的立体插值法（cubic）所获结果与此相当，NSE＝0.79，B＝-0.65（％），EV＝0.79，R2＝0.80。这说明利用MM5 DWHC嵌套模型来模拟流域日平均流量是可行的。MM5 DWHC嵌套模型在径流模拟方面，比利用地面资料驱动结果要好。MM5 DWHC嵌套模型的计算结果表明，内陆河高寒山区流域存在明显的浅表产流特征，这与地面观测资料驱动结果一致。模型调试结果表明，MM5输出结果存在某种奇异性，且输出的非汛期降水量明显偏大。 相似文献
11.
Towards spatial geochemical modelling: Use of geographically weighted regression for mapping soil organic carbon contents in Ireland 总被引：6，自引：0，他引：6
It is challenging to perform spatial geochemical modelling due to the spatial heterogeneity features of geochemical variables. Meanwhile, high quality geochemical maps are needed for better environmental management. Soil organic C (SOC) distribution maps are required for improvements in soil management and for the estimation of C stocks at regional scales. This study investigates the use of a geographically weighted regression (GWR) method for the spatial modelling of SOC in Ireland. A total of 1310 samples of SOC data were extracted from the National Soil Database of Ireland. Environmental factors of rainfall, land cover and soil type were investigated and included as the independent variables to establish the GWR model. The GWR provided comparable and reasonable results with the other chosen methods of ordinary kriging (OK), inverse distance weighted (IDW) and multiple linear regression (MLR). The SOC map produced using the GWR model showed clear spatial patterns influenced by environmental factors and the smoothing effect of spatial interpolation was reduced. This study has demonstrated that GWR provides a promising method for spatial geochemical modelling of SOC and potentially other geochemical parameters. 相似文献
12.
尽管连续混合器模型已经广泛应用于土壤中溶质迁移转化规律计算,但却仅限于饱和土壤条件。通过采用Kostiakov公式描述非稳定入渗过程,并结合活塞假设计算入渗过程中土壤水分的运动和分布规律,将连续混合器模型扩展应用于非饱和土壤的盐分淋洗过程计算,并求出了模型的解析解。分析发现,在一定的土壤质地、初始含水率剖面和初始含盐量剖面下,模型的计算结果会受到土层划分厚度的影响,而合理的土层厚度又与饱和导水率和溶质弥散系数之间存在量纲一的函数关系。当土层厚度选取合理时,连续混合器模型与HYDRUS-1D的计算结果十分接近,采用该模型模拟试验土壤盐分淋洗过程,显示了较好的计算精度。 相似文献
13.
Capturing strain localization in reinforced soils 总被引：2，自引：1，他引：1
Lade’s single hardening soil model with Cosserat rotation embodied in the finite element method is employed to investigate
the behavior of geosynthetic reinforced soils with special attention to the development of shear banding. The ability of the
finite element model to detect shear banding in a reinforced soil is examined against three high quality small-scale laboratory
plane strain tests on Toyoura sand with and without reinforcement. These three tests were chosen because of the clear failure
surfaces that developed in the soil during loading. The FEM analyses were able to reasonably simulate the plane strain laboratory
tests including both unreinforced and reinforced cases. The FEM analyses gave reasonably good agreement with the experimental
results in terms of global stress–strain relationships and shear band occurrences. Furthermore, and based on FE analyses of
a hypothetical geosynthetic reinforced soil (GRS) retaining wall, it is shown that the geosynthetic reinforcements are very
effective in hindering the formation of shear bands in GRS retaining walls when small spacing between the reinforcement layers
was used. When used properly, the geosynthetic reinforcements made the soil behave as a truly reinforced mass of considerable
stiffness and strength. 相似文献
14.
Landslide-prone slopes in earthquake-affected areas commonly feature heterogeneity and high permeability due to the presence of cracks and fissures that were caused by ground shaking. Landslide reactivation in heterogeneous slope may be affected by preferential flow that was commonly occurred under heavy rainfall. Current hydro-mechanical models that are based on a single-permeability model consider soil as a homogeneous continuum, which, however, cannot explicitly represent the hydraulic properties of heterogeneous soil. The present study adopted a dual-permeability model, using two Darcy-Richards equations to simulate the infiltration processes in both matrix and preferential flow domains. The hydrological results were integrated with an infinite slope stability approach, attempting to investigate the hydro-mechanical behavior. A coarse-textured unstable slope in an earthquake-affected area was chosen for conducting artificial rainfall experiment, and in the experiment slope, failure was triggered several times under heavy rainfall. The simulated hydro-mechanical results of both single- and dual-permeability model were compared with the measurements, including soil moisture content, pore water pressure, and slope stability conditions. Under high-intensity rainfall, the measured soil moisture and pore water pressure at 1-m depth showed faster hydrological response than its simulations, which can be regarded as a typical evidence of preferential flow. We found the dual-permeability model substantially improved the quantification of hydro-mechanical processes. Such improvement could assist in obtaining more reliable landslide-triggering predication. In the light of the implementation of a dual-permeability model for slope stability analysis, a more flexible and robust early warning system for shallow landslides hazard in coarse-textured slopes could be provided. 相似文献
15.
The paper at hand investigates a strategy to calibrate different constitutive models for soils via back analysis. The efficiency and reliability of the parameter identification for soil models is worked out. In order to demonstrate of how to utilise identification procedures, results from optimisation against conventional oedometer and drained triaxial compression tests on natural Pappadai clay are presented and discussed. The aim of geotechnical optimisation problems is to obtain a set of model parameter values that provide the best match between soil model simulations and appropriate measurements. For the parameter identification process, a constrained population-based algorithm is chosen, namely the Particle Swarm Optimiser. The identification is carried out in an initial step separately on each test and then simultaneously on oedometer and triaxial tests. The evaluation is performed employing three different constitutive models of varying complexity and number of constitutive parameters.A subsequent residual analysis and the computation of confidence intervals for the parameters provide valuable results to assess the quality of the identified parameters in correlation with the evaluated data. Therefore, criteria of the utility and reliability of the mathematical models for further prognosis computations can be estimated. 相似文献
16.
基坑开挖过程中,土体应力路径、卸载回弹再压缩特性与简单加载或卸载不同,采用常规的理想弹塑性模型模拟基坑开挖,得到的围护墙位移、坑内土体回弹以及坑外沉降较大。分析了基坑开挖不同区域土体的性状,采用土体硬化模型模拟基坑开挖的卸载与土体硬化行为,结合工程算例,对比土体硬化模型和理想弹塑性模拟以及实测的围护结构土压力、围护墙水平位移和坑外土体沉降,并利用强度折减法分析基坑的稳定性。计算结果表明,考虑土体硬化的HS模型有限元方法能体现土体卸载再加载与开挖的特性,所得土压力、围护结构水平位移以及基坑抗隆起稳定性符合软土地区基坑工程的实践。 相似文献
17.
Behzad Amir-Faryar M. Sherif Aggour Richard H. McCuen 《Geomechanics and Geoengineering》2017,12(1):60-71
Numerous model forms have been used to predict the dynamic behaviours of soils, mainly the shear modulus and material damping. These models are used to represent normalised shear modulus reduction and material damping curves. The majority of the existing models are empirical and were proposed for specific soil types, strain ranges, etc. Some are limited to the data used in fitting, but fail to provide a good fit to other sets of data. The available model functions are not universal, which means that a model developed for one soil type may not be applicable for use with other soil types. In this paper, two universal mathematical models were proposed to predict the normalised shear modulus reduction and material damping curves. The mathematical model forms are sufficiently flexible to be widely used with different soil types. The models were evaluated using verification data of eight different soil types, i.e., data that were not used to fit the model parameters. The results indicate that the proposed model forms can accurately model the dynamic soil properties within the typical earthquake range. The advantage of developing the two universal models are two-fold, first the forms are applicable for sand, clay, and fibre-soil composite and second with further testing of soils, the model coefficients could ultimately be used to further understand the physical processes in soil behaviour, especially damping. 相似文献
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参考加拿大Alberta SGRG层次性分析模式,选择其中Tier 1、Tier 2两层次进行分析,结合适合我国的参数计算出了某农药厂土壤地下水中的有机污染物1,2-二氯乙烷、1,2-二氯丙烷修复值,得到了通用的Tier 1修复指导值分别为:渗坑土壤中1,2-二氯乙烷6.2μg/kg,1,2-二氯丙烷67μg/kg;场地地下水中1,2-二氯乙烷、1,2-二氯丙烷均为5μg/L。在此基础上,结合实地调查获取场地参数,利用Tier 2评价对指导值进行修正,确定了场地最终修复目标值:渗坑土壤中1,2-二氯乙烷为11μg/kg,1,2-二氯丙烷为45μg/kg;地下水中1,2-二氯乙烷、1,2-二氯丙烷仍为5μg/L。各途径修复值的改变较符合层次性评价的理论,即Tier 2修复值较Tier 1宽松;但1,2-二氯丙烷的保护DUA途径修复值较Tier 1更加严格,这是由于场地特定条件造成的。 相似文献
19.
砂土中水平受荷桩非线性分析 总被引：4，自引：0，他引：4
对水平受荷桩的非线性分析,多采用p-y曲线法。现行p-y曲线模型很多,曲线形式和选用的参数各不相同。分析各桩土参数对现有p-y曲线的影响,并选择合理的标准化参数将各p-y曲线归一化,采用双曲线模型拟合归一化曲线。总结目前对地基反力模量和土体极限抗力的研究,并考虑桩径、施工等因素的影响,选择合理的双曲线模型参数。通过实例对比分析,证明了双曲线模型以及参数选取的有效性和适用性。双曲线模型形式简洁,符合理想土体的应力-应变关系,并能近似拟合现有的砂土p-y曲线,可广泛用于工程中砂土水平受荷桩基的非线性分析 相似文献
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土壤环境质量支持向量机预测模型初探——以湖南长沙、株洲、湘潭地区为例 总被引：1，自引：0，他引：1
针对土壤环境质量时序连续监测数据缺乏的现状以及城市建设发展需要,笔者试图通过建立土壤环境质量影响因素预测模型,实现利用影响因素对土壤环境质量进行预测评估。基于支持向量机相对传统经验模型除了更适合样本少情况以外,还具有泛化力强、精确度较高的优势,尝试建立基于支持向量机的土壤环境质量预测模型。研究选择时序连续的9个土壤环境质量影响因素,如国内生产总值、有害废水、废气、固体废物产生量、人口总数、年降雨量、植被覆盖面积等作为土壤环境质量预测评价因子,以长沙、株洲、湘潭地区1986年和2003年的879个土壤样品的Cu、Pb、Zn、Cd、Co、Ni、Cr、Mn含量和17年的51个影响因素样本数据作为学习和预测检验样本,采用遗传算法优选并确定了高斯核函数参数(γ)、损失函数不敏感度(ε)以及惩罚因子参数值(C),它们分别为1.021、0.000416和1012。优化逼近了土壤环境质量与影响因素的关系隐函数,获得基于支持向量机的土壤环境质量预测模型,检验结果显示了模型的有效性。 相似文献