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51.
Modeling the suitability of land to support specific land uses is an important and common GIS application. Three classic models, specifically pass/fail screening, graduated screening and weighted linear combination, are examined within a more general framework defined by fuzzy logic theory. The rationale underlying each model is explained using the concepts of fuzzy intersections, fuzzy unions and fuzzy averaging operations. These fuzzy implementations of the three classic models are then operationalized and used to analyze the distribution of kudzu in the conterminous United States. The fuzzy models achieve better predictive accuracies than their classic counterparts. By incorporating fuzzy suitability membership of environment factors in the modeling process, these fuzzy models also produce more informative fuzzy suitability maps. Through a defuzzification process, these fuzzy maps can be converted into conventional maps with clearly defined boundaries, suitable for use by individuals uncomfortable with fuzzy results. 相似文献
52.
Asuri Sridharan Ahmed El-Shafei Norihiko Miura 《Marine Georesources & Geotechnology》2013,31(1):21-50
The soft clay of Ariake Bay, in western Kyushu, Japan covers several hundred square kilometers. Ariake clay consists of the principal clay minerals namely smectite, illite, kaolinite and vermiculite, and other minerals in lesser quantity. The percentage of the principal clay mineral can vary significantly. The percent clay size fraction and the salt concentration can also vary significantly. In view of the importance of undrained shear strength in geotechnical engineering practice, its behavior has been studied with respect to variation in salt concentration. Basically two mechanisms control the undrained strength in clays, namely (a) cohesion or undrained strength is due to the net interparticle attractive forces, or (b) cohesion is due to the viscous nature of the double layer water. Concept (a) operates primarily for kaolinitic soil, and concept (b) dominates primarily for montmorillonitic soils. In Ariake clay, different clay minerals with different exchangeable cations and varying ion concentration in the pore water and varying nonclay size fraction are present. In view of this while both concepts (a) and (b) can coexist and operate simultaneously, one of the mechanisms dominates. For Isahaya clay, concept (a), factors responsible for an increase in level of flocculation and attractive forces result in higher undrained strength. Increase in salt concentration increases the remolded undrained strength at any moisture content. For Kubota and Kawazoe clays, concept (b) factors responsible for an expansion of diffuse double layer thickness, resulting in higher viscous resistance, increase the undrained shear strength, that is, as concentration decreases, the undrained strength increases at any moisture content. The liquid limit of Isahaya clay increases with increase in ion concentration and a marginal decrease is seen for both Kubota and Kawazoe clays, and their behavior has been explained satisfactorily. 相似文献
53.
Determination of Coefficient of Radial Consolidation Using Steepest Tangent Fitting Method 总被引：1，自引：1，他引：0
J. S. Vinod A. Sridharan Buddhima Indraratna 《Geotechnical and Geological Engineering》2010,28(4):533-536
Barron (Trans ASCE 113:718–724, 1948) theoretical relationship between degree of consolidation (U
r
) and time factor (T
r
) is generally used to determine the coefficient of radial consolidation c
r
. Several researchers have proposed different laboratory techniques for obtaining the value of c
r
. However, the usual approach is to compare some salient features of the theoretical U
r
–T
r
relationship with the compression, δ and time, t based on the laboratory data. In this paper, rapid consolidation test procedure originally proposed by Su (J Soil Mech Found
Div Am Soc Civ Eng No. 95: Proc. Pap. 1729 (1–9), 1958) to determine the coefficient of vertical consolidation (c
v
) is extended to evaluate Barron’s coefficient of radial consolidation c
r
for the case of equal strain. The characteristic feature of the proposed method is the identification of the steepest tangent
from the δ–log t plot. The slope of steepest tangent is independent of the drain spacing ratio (n) with a value of 0.847. This approach is rapid, and it predicts more reliable values of c
r
as it is less influenced by the secondary compression. In addition, this method is more versatile and can be applied for
consolidation trends which do not always exhibit the typical S-shape. 相似文献