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Papers by Herman Peiffer
International Polymer Processing, May 1, 1994
Abstract In the processing of polypropylene via a melt, the extruder exerts an important influenc... more Abstract In the processing of polypropylene via a melt, the extruder exerts an important influence on product quality. Trials were carried out on production extruders with the aim of improving melt quality. As an aid to evaluating the screws, a computer model was developed which could simulate extruders. This model is described in the first part of this paper. In the second part, the computer model is tested using experimental data taken from a range of different extruders. The comparisons illustrate the excellent correlation and hence validity of the model. On the basis of these results, recommendations are given for the optimization of single-screw extruders.
Design of Axially Loaded Piles European Practice, 2020
This paper describes the development of an instrumented dilatometer which is identical in dimensi... more This paper describes the development of an instrumented dilatometer which is identical in dimensions and thus soil disturbance during penetration to the standard dilatometer introduced by Prof. Marchetti in 1980, except for the use of a rigid piston with a larger displacement up to 2.35 mm and instrumentation allowing measurements of full pressure-displacement curve and porewater pressure at the piston center. The fabrication of this instrumented dilatometer was assisted by a novel metal 3D printing technique, which may provide further insight in improving other geotechnical testing apparatus. The new instrumented dilatometer was tested at a site of silty sand in Belgium, along with a DMT and a CPT located 1 m apart. Results show that the instrumented DMT can provide an opportunity to improve the estimation of lift-off pressure , which is crucial to the DMT interpretation, ba sed on the judgement of the full expansion curve. RÉSUMÉ : Cet article décrit le développement d'un dila...
In Belgium the Boom Clay is a well known overconsolidated clay formation. This Tertiary clay, wit... more In Belgium the Boom Clay is a well known overconsolidated clay formation. This Tertiary clay, with the same geological origin as the London Clay, is used for the fabrication of bricks, roofing tiles. In the article is described how the DMT can be used to evaluate the stability of slopes, to determine the risk of instability and how the cause of the failure directly could be related to the results of the DMT-measurement. The results of the tests before the period of instability, during the period of instability and after stabilization are discussed. The KD-value is a representative value to judge the risk of instability.
We utilize a bench-scale centrifuge to speed up the process of porous media in ltration. This all... more We utilize a bench-scale centrifuge to speed up the process of porous media in ltration. This allows to obtain measurements in a fraction of the time needed by standard in ltration methods, especially for clayey soils. By measuring only transient data like water level in an inflow or outflow chamber, gravitational center of the sample, or the rotational momentum of the sample, it is possible to determine the soil characteristics. This is done by solving the inverse problem based on the mathematical model for saturated and unsaturated water infi ltration in soil. The model for the unsaturated flow is based on Richards' equation and the Van Genuchten-Mualem formula. We present the experimental set-up, accuracy of the measurements, and the numerical solution method. For saturated flow we compare with standard tests and the classical formula for hydraulic conductivity in a centrifuge from two discrete measurements.
In this chapter, the origin and remediation of an important sliding in the overconsolidated Boom ... more In this chapter, the origin and remediation of an important sliding in the overconsolidated Boom Clay in Kruibeke (Belgium) is discussed. Local and environmental factors caused an unstable slope about 30 m deep, A larger sensitivity to erosion resulted finally in the instability of the slope. Because of the formation of fine cracks in the soil there was a possibility for the water to penetrate in the clay close to the surface, resulting in the presence of higher water pressures. Also, the presence of the excavator on top of the slope during exploitation had an important impact on the stress state of the soil. Both an analytical and numerical approach were used to estimate the factor of safety. Because of the change of the soil characteristics, the factor of safety decreases, which can be estimated through a numerical analysis (using the Strength Reduction Method). This chapter also discussed the applied techniques for the remediation using numerical analysis. Also, the importance of...
International Polymer Processing, May 1, 1994
Abstract In the processing of polypropylene via a melt, the extruder exerts an important influenc... more Abstract In the processing of polypropylene via a melt, the extruder exerts an important influence on product quality. Trials were carried out on production extruders with the aim of improving melt quality. As an aid to evaluating the screws, a computer model was developed which could simulate extruders. This model is described in the first part of this paper. In the second part, the computer model is tested using experimental data taken from a range of different extruders. The comparisons illustrate the excellent correlation and hence validity of the model. On the basis of these results, recommendations are given for the optimization of single-screw extruders.
Design of Axially Loaded Piles European Practice, 2020
This paper describes the development of an instrumented dilatometer which is identical in dimensi... more This paper describes the development of an instrumented dilatometer which is identical in dimensions and thus soil disturbance during penetration to the standard dilatometer introduced by Prof. Marchetti in 1980, except for the use of a rigid piston with a larger displacement up to 2.35 mm and instrumentation allowing measurements of full pressure-displacement curve and porewater pressure at the piston center. The fabrication of this instrumented dilatometer was assisted by a novel metal 3D printing technique, which may provide further insight in improving other geotechnical testing apparatus. The new instrumented dilatometer was tested at a site of silty sand in Belgium, along with a DMT and a CPT located 1 m apart. Results show that the instrumented DMT can provide an opportunity to improve the estimation of lift-off pressure , which is crucial to the DMT interpretation, ba sed on the judgement of the full expansion curve. RÉSUMÉ : Cet article décrit le développement d'un dila...
In Belgium the Boom Clay is a well known overconsolidated clay formation. This Tertiary clay, wit... more In Belgium the Boom Clay is a well known overconsolidated clay formation. This Tertiary clay, with the same geological origin as the London Clay, is used for the fabrication of bricks, roofing tiles. In the article is described how the DMT can be used to evaluate the stability of slopes, to determine the risk of instability and how the cause of the failure directly could be related to the results of the DMT-measurement. The results of the tests before the period of instability, during the period of instability and after stabilization are discussed. The KD-value is a representative value to judge the risk of instability.
We utilize a bench-scale centrifuge to speed up the process of porous media in ltration. This all... more We utilize a bench-scale centrifuge to speed up the process of porous media in ltration. This allows to obtain measurements in a fraction of the time needed by standard in ltration methods, especially for clayey soils. By measuring only transient data like water level in an inflow or outflow chamber, gravitational center of the sample, or the rotational momentum of the sample, it is possible to determine the soil characteristics. This is done by solving the inverse problem based on the mathematical model for saturated and unsaturated water infi ltration in soil. The model for the unsaturated flow is based on Richards' equation and the Van Genuchten-Mualem formula. We present the experimental set-up, accuracy of the measurements, and the numerical solution method. For saturated flow we compare with standard tests and the classical formula for hydraulic conductivity in a centrifuge from two discrete measurements.
In this chapter, the origin and remediation of an important sliding in the overconsolidated Boom ... more In this chapter, the origin and remediation of an important sliding in the overconsolidated Boom Clay in Kruibeke (Belgium) is discussed. Local and environmental factors caused an unstable slope about 30 m deep, A larger sensitivity to erosion resulted finally in the instability of the slope. Because of the formation of fine cracks in the soil there was a possibility for the water to penetrate in the clay close to the surface, resulting in the presence of higher water pressures. Also, the presence of the excavator on top of the slope during exploitation had an important impact on the stress state of the soil. Both an analytical and numerical approach were used to estimate the factor of safety. Because of the change of the soil characteristics, the factor of safety decreases, which can be estimated through a numerical analysis (using the Strength Reduction Method). This chapter also discussed the applied techniques for the remediation using numerical analysis. Also, the importance of...