David J. Elton

FUZZY INFORMATION PROCESSING BY THE MONTE CARLO SIMULATION TECHNIQUE

Abstract This paper presents a new method utilizing the Monte Carlo simulation technique for processing fuzzy information. The method was primarily developed for determining the weighted average of a group of ratings that are represented by fuzzy subsets. By generating a uniform random number, normalizing it with respect to the maximum functional value of the cumulative membership function, and then equating the normalized uniform random number to the cumulative function F(x), a value x can be back-calculated for each fuzzy subset. The resulting value x is a random number representing that fuzzy subset. The weighted average was then calculated with these random numbers. The first through fourth moment parameters were obtained and used to fit the random values of the weighted average with a beta distribution. By normalizing the curve-fitted beta distribution function with respect to its maximum functional value, the membership function of the final fuzzy subset was obtained. Comparison is made between the ...

A Capacitive Fringing Field Sensor Design for Moisture Measurement Based on Printed Circuit Board Technology

Interdigitated electrode capacitive fringing field sensors have been utilized in numerous applications. Although various technologies are used to realize these types of sensors, printed circuit board technology is particularly advantageous for realizing this type of sensor through fabricating the interdigitated electrode structures in the patterned Cu foil. Additionally, the solder mask coating can insulate the electrodes to prevent shorting in the presence of water. Using this approach, prototype sensors were designed, simulated, fabricated, and successfully evaluated. Applications include water detection and quantity measurement and soil moisture content measurement.

Theory of Soil / Geotextile Interaction

In this study, soil/geotextile interaction is characterized by the following general equation-τ = τa + tan δ*( σnor) n -where τ and σnor are shear and normal stresses on the failure plane at failure, τa is the soil/fabric adhesion component, and δ* and n are friction indexes. This equation provides a general relationship in which the classical Mohr-Coulomb law is considered as a special case. It holds for a wide range of normal stresses and describes soil/geotextile interaction in terms of material-related parameters. A theoretical interpretation of the effects of critical factors affecting soil / geotextile interaction is based on this equation. The four main factors examined are soil/geotextile adhesion, normal stress, deformation of junctions at the soil/fabric interface, and surface roughness. To evaluate interactive deformational modes of soil / geotextile systems, a pull-out test device was designed and constructed and used to test woven and nonwoven textiles. Identified interactive modes were divided into three main categories: pure slippage, complete rupture, and combined slippage and longi tudinal deformation. This categorization supported by the equation above can help rationalize the complex mechanism involved in pull-out conditions.

CONTRACTOR PREQUALIFICATION USING FUZZY SETS

Abstract Contractor prequalification involves evaluation of factors that contain a high degree of uncertainty. Current methods of contractor prequalification fail to address uncertainty in the evaluation process. The use of fuzzy sets is examined to address this shortcoming. Fuzzy sets have been employed in order to provide a more consistent, rational method of evaluating the non-random uncertainties that are present in the contractor evaluation process. The linguistic factors (such as good, fair, or poor) used in fuzzy set analysis provide a more appropriate means to model decision circumstances that occur in industry than the current crisp (usually numerical) factors. Evaluation factors from a previous study are used. Each factor was assigned a grade. Correspondingly, each grade was represented by a fuzzy set. These fuzzy sets were then weighted and combined resulting in a fuzzy set. This composite fuzzy set represents the contractors rating. When evaluating multiple contractors, each contractors comp...

Pullout and Direct Shear Testing of Geosynthetic Reinforcement: State-of-the-Art Report

The frictional characteristics of a soil-geosynthetic interface can be determined by direct shear and pullout tests. The direct shear test is commonly conducted according to ASTM standard D5321. However, at present there is no ASTM method for pullout testing of geosynthetics. During the past 10 years different researchers have obtained a wealth of information from direct shear and pullout tests of geosynthetics. A critical analysis of direct shear and pullout tests and an evaluation of the effects of fundamental material and testing parameters on test results are presented.

Performance Evaluation of Nonwoven Geotextiles in Soil-Fabric Interaction

A laboratory research program was undertaken to determine the influence of fabric mass and normal pressure on the stress-strain characteristics of a geotextile-soil inter face. Pullout tests were done in a large pullout box using three needlepunched non woven geotextiles with the same apparent opening sizes and different mass/unit areas. A dry medium sand was the cover material. Effects of mass/unit area of the fabric and normal pressure on pullout test results were analyzed in terms of ultimate pullout load and strain at different points on the geotextile specimens. Pullout tests were conducted at 7, 14, and 21 kPa normal pressures and at a constant displacement rate of 20 mm/min. Pullout resistance decreased with increased gootextile mass / unit area due to extensive necking of the geotextiles. Pullout resistance also increased with increasing normal pressure. Effective embedment length was determined at each normal pressure level based on the strain developed along the length of the geotextiles.

Capacitive fringing field sensors in printed circuit board technology

Capacitive fringing field sensors utilizing interdigitated electrode structures have been utilized in many applications. Printed circuit board technology is useful for realizing this type of sensor architecture by fabricating the interdigitated electrode structures in the patterned Cu foil. Furthermore, the solder mask coating is useful for insulating the electrodes to prevent shorting in the presence of water. Using this approach, prototype sensors were designed, simulated, fabricated and successfully evaluated. Applications include water detection and quantity measurement, and soil moisture content measurement.

Bubblepoint Testing of Geotextiles: Apparatus and Operation

A simple, inexpensive device for measuring geotextile pore sizes, using ASTM D 6767, is described and its operation is outlined with guidance for correct operation. The accuracy and consistency of the test are shown. The test appears to have better consistency than the apparent opening size (AOS) test, avoids the inherent and operator-dependent problems of the AOS test, and further, describes the entire pore size distribution of a geotextile, making it useful for developing a more complete filter criterion. Suggestions are made for improving ASTM D 6767.

VERTICAL CAPACITY OF PILES USING FUZZY SETS

Abstract Because prediction of the load-carrying capacity of piles continues to challenge geo-technical engineers, new solutions are needed. The problem is aggravated by the lack of understanding of the phenomena of soil-pile interaction, and the limited quantity and inexact quality of subsurface soil information that can be provided for analysis. The use of fuzzy set theory improves the engineers ability to handle the uncertainty in the soil parameters and the prediction methods and thus improves the reliability of the pre dicted capacity. A methodology for predicting pile capacity based on fuzzy set theory is developed and implemented in a computer program. The validity of the program re sults is evaluated using a US Federal Highway Administration (FHWA) pile load test database. The comparison between predicted and measured ultimate capacities of piles in sand, clay and mixed soils shows that the predictive capability of the developed program is very good.

Preparing Very Loose Granular Triaxial Specimens by Ex Situ Freezing

Ex situ soil freezing can be used to prepare very loose cohesionless triaxial specimens that can be handled, stored, and transported. This paper describes two freezing techniques, freezing with cold air in a freezer and freezing with liquid nitrogen. These methods are used to prepare very loose saturated Ottawa sand specimens. Special equipment and techniques used for each method are described. The advantages and disadvantages of both methods and the effectiveness of the efforts to minimize disturbance due to volume changes during freezing are discussed. Properties of specimens prepared using each method are presented. The results of 16 consolidated undrained triaxial shear tests are presented. The freezing method affects the amount of volume change during freezing but does not significantly affect the effective angle of internal friction.