Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Patent
1996-04-22
1997-12-16
Chilcot, Richard
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
73843, G01N 308
Patent
active
056987897
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for measuring the properties, such as elastic, plastic and viscous deformation resistances, of granular earth materials subjected to a load, according to which method cylinder between a planar bottom plate and cover plate of the cylinder, deviate by an angle from the central axis of the cylinder in the same plane and in the same direction, changing the position of the plates rotationally in relation to the central axis of the cylinder with the plates remaining parallel to each other, and
In this connection, earth materials refer to gravel, sand, crushed aggregates including crushed rock, stiff fresh concrete and other similar granular components.
Information is needed in earthwork about the suitability of the earth material for each particular purpose, for example about the changing of earth materials under traffic loads in road construction, the behaviour of the foundations of buildings in earthquake areas, the bearing capacity of the sea bottom under a leg of a drilling rig, and the behaviour of a granular material during transportation and compaction.
Elastic, or reversible, deformations occur in earth materials subjected to a load. If the load is heavy enough, it also causes plastic, or irreversible, deformations in the earth material, and these often lead to the damaging of the structure.
If the material comprises stiff viscous components, it behaves in a viscoelastoplastic way, in which case a viscous deformation resistance appears in the same way as a plastic resistance. This phenomenon is well known from materials, such as asphalt, which are used for road pavement and have some bitumen mixed in them. A special feature of a viscous resistance is that it decreases if the sliding speed is reduced or the temperature of the sample is increased. By means of these measures, a viscous and plastic resistance can be distinguished from each other.
When the foundation of a device or a building is designed to carry periodic loads, the aim is that there will be no detrimental, irreversible (plastic) deformations in the ground soil. Therefore it is important that both the elastic and plastic behaviour of the material can be measured as reliably as possible especially in the borderland between these two phenomena. The strengths of a material and the facts about its behaviour measured by prior methods have been approximate, since measuring has been difficult and inexact.
Transfers of large earth materials are preferably avoided during building due to costs. Therefore, information is desired about the properties of all usable materials situated near the building site. Different materials, for example gravel and crushed aggregate, are often mixed in construction. Then the properties of the mixed material have to be controlled by continuous measurements. In these measurements it is also important that the elastic and plastic behaviour of the material can be measured separately.
It is also important to know the viscous properties of the material in developing and testing asphalt and in paving roads, so that the compaction properties of the aggregate, the amount of bitumen, and the viscosity could be proportioned to each other in making the asphalt material.
The elastic and plastic deformations and stresses of an earth material under periodic loads are generally measured in laboratories by means of for example a shear box and a so-called triaxial tester. There are several practical problems in these tests. The movement in the tests takes place back and forth in one direction. To achieve such a periodic movement, complex and expensive equipment is required. The study of great deformations, i.e. the plastic area, is not particularly exact, since the field of deformation of the sample in each device is very non-homogenous. Due to these and also to other reasons, there is a great deal of deviation in the results, and therefore they are not very reliable.
A method and an apparatus for measuring the properties of a stiff, granular material, in particular its compactibility, are previously kno
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S.F. Brown "Lecture I: Bituminous Materials: Elastic Stiffness and Permanent Deformation", I.1-I.11.
Lainio Kai Juhani
Paakkinen Ilmari
Chilcot Richard
Noori Max H.
Paakkinen Ilmari
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