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391.
C. J. Loupasakis B. G. Christaras G. Ch. Dimopoulos T. N. Hatzigogos 《Geotechnical and Geological Engineering》2009,27(1):71-80
The selection of the constitutive laws reproducing the response of geomaterials usually becomes a very complicated procedure;
especially during the analysis of geostructures containing coarse grained materials. The objective of this study, is the evaluation
of models based on the perfect and hardening plasticity theory, regarding their ability to analyze the behaviour of soil materials,
used for the construction of earth dams. The evaluated constitutive laws are the elastic–perfect plastic model based on the
Mohr–Coulomb failure criterion and the isotropic hardening CAP model based on the same criterion. The data used for the evaluation
of the models, originate from the body of the Sfikia earth dam. This dam is considered suitable, because of the specialized
laboratory tests’ available data, regarding the materials of every zone. The availability of those data, as well as the variety
of the construction geomaterials, allows the deduction of generalized conclusions, concerning the ability of the specific
models to simulate a variety of similar earth constructions. 相似文献
392.
Abidin Kaya 《Geotechnical and Geological Engineering》2009,27(2):281-288
A backpropagation artificial neural network (ANN) model is developed to predict the secant friction angle of residual and
fully softened soils, using data reported by Stark et al. (J Geotech Geoenviron Eng ASCE 131:575–588, 2005). In the ANN model, index properties such as liquid limit, plastic limit, activity, clay fraction and effective normal stress
are used as input variables while secant residual friction angle is used as output variable. The model is verified using data
that were not used for model training and testing. The results also indicate that the secant residual friction angle of cohesive
soils can be predicted quite accurately using liquid limit, clay fraction and effective normal stress as input variables with
R
2 = 0.93. The sensitivity analysis results indicate that plastic limit and activity have no appreciable effect on ANN predicted
secant friction angles. The secant friction angle predictions of the ANN model were also compared with those of Stark’s et
al. (2005) curves and the empirical formulas suggested for the same data sets by Wright (Evaluation of soil shear strengths for slope
and retaining wall stability with emphasis on high plasticity clays, 2005). The comparison shows that the ANN model predictions are very close to those suggested by the Stark et al. (2005) curves but much better than the prediction of Wright’s (2005) empirical equations. The results also show that ANN is an alternative powerful tool to predict the secant friction angle
of soils. 相似文献
393.
Utilizing computational neural networks for evaluating the permeability of compacted clay liners 总被引:1,自引:0,他引:1
The design of lined waste-storage facilities is significantly influenced by the permeability of the liner. The permeability of compacted clay liners, in turn, is influenced by factors such as clay type and composition, compaction type and effort, and operating conditions. The complexity of the permeation process makes it difficult to predict analytically the permeability from these factors. As a result, empirical regression models are frequently used to predict permeability. In this paper, permeability prediction models are developed using computational neural networks (CNNS). The developed CNN models are used to predict the permeability of compacted clay for a known set of soil properties and field and laboratory conditions. Moreover, the models are used to determine the relative importance of the various input parameters to the model output. Also, a comparison between regression models and neural networks for predicting permeability is presented and the advantages of utilizing CNN methodology over regression techniques in model development are highlighted. 相似文献
394.
对山东半岛沿岸7个泻湖的表层沉积物中的细颗粒成分中的粘土矿物进行了定性和半定量分析,并描述了矿物特征,发现粘土矿物的百分含量判别很大,其中蒙皂石的含量在地域上由西向东规则递减。泻湖与海水的交换状况对粘土组分有相当的影响,不久前封闭的泻湖的粘土矿物成分与未封闭的泻湖不同,显示了物源、物源成分的搬运距离及水体交换等因素的明显影响,表明了泻湖沉积物与环境动力及物源有密切关系。 相似文献
395.
A shortcoming of the hypoplastic model for clays proposed by the first author is an incorrect prediction of the initial portion
of the undrained stress path, particularly for tests on normally consolidated soils at isotropic stress states. A conceptually
simple modification of this model, which overcomes this drawback, is proposed in the contribution. The modified model is applicable
to both normally consolidated and overconsolidated soils and predicts the same swept-out-memory states (i.e., normal compression
lines) as the original model. At anisotropic stress states and at higher overconsolidation ratios the modified model yields
predictions similar to the original model. 相似文献
396.
Presented in this paper are the results of experimental study and analysis of the subsidence characteristics obtained from soil samples with different contents of clay particles though laboratory dynamic triaxial test, Laser particle size analysis, chemical analysis and electronic microscope scanning. By comparison of the obtained data, the following conclusions are drawn out:(1)The stability of the loess varies with different content of clay; (2) The relation between the dynamic shear strength and the clay particles is not monotonous, but parabolic; (3) In the same consolidation ratio, the clayey loess is the weakest subsidence-resistant when the clay particle content is between 16%~17%. 相似文献
397.
398.
399.
Barbara Lang Alan P. Bedford Nigel Richardson Stephen J. Brooks 《Journal of Paleolimnology》2003,30(4):451-460
Initial investigations of Holocene carbonate sediment from Hawes Water, Northwest England, yielded lower numbers of chironomid head capsules than anticipated. Standard techniques used to prepare sediment for chironomid analysis were ineffective in breaking up the coarse crystalline sediment structure sufficiently. This led to large amounts of sediment being retained and increased sample processing times. The low yield of head capsules also meant that more sediment was needed to produce adequate numbers of head capsules for analysis. The use of ultra-sound as part of the sediment processing was investigated. This technique reduced the amount of sediment left for sorting and yielded significantly more head capsules which were of equivalent structural condition and cleaner than those produced by conventional methods. The technique was extended to clay samples where similar results were obtained although shorter treatment times are recommended. The proportion of Tanytarsini and Tanypodinae heads increased significantly in carbonate and clay samples, respectively; both sediment types showed a significant decline in the proportion of Chironomini. The results indicate that ultra-sonic preparation of samples will yield a more accurate representation of chironomid assemblages in sediments leading to greater sensitivity and reliability in analysing past environmental conditions. 相似文献
400.