Granular materials and method of soil reinforcement

Details Granular materials and method of soil reinforcement Granular materials and method of soil reinforcement

1996-03-07

1997-11-04

Graysay, Tamara L.

Hydraulic and earth engineering

Earth treatment or control

Chemical

404 76, C09K 1700, E01C 736, E01C 2100

Patent

active

056832087

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to techniques for making up grounds in which sands or granular substitute materials are used; it relates in particular to the production of sublayers of tracks, roads or sports terrains.
2. Discussion of the Background
When a road is created on a new ground, various steps are carried out, the first consisting in levelling the ground with machines such as bulldozers which flatten the projecting parts and fill up the holes. The second phase consists in depositing on the ground thus prepared a subgrade, the first function of which will be to allow movement of the convoys and machines over the ground while preventing it being damaged or the machines becoming bogged down. Next, onto the subgrade are deposited one or more other layers of different type, called foundation course, base course, etc., the common role of which is to support the layers closer to the surface which are bound by large quantities of hydraulic or bituminous binders.


SUMMARY OF THE INVENTION

Each of the subjacent layers is produced with a sand of well-defined quality which, unfortunately, in general, is not available in the vicinity of the site. Although the cost of such a material is not high, its transport may turn out to be very expensive.
One of the objects of the invention is to make it possible to use, for the production of subjacent layers, materials, in particular sand coming from pits near the site, to which fibres are added which give them the desired properties.
Another object of the invention is to improve the contribution of the subjacent layers to the stability of the road and to the integrity of the carriageway over time.
Likewise, in the field of land development, in order to prepare it for a new purpose such as, for example, in order to create a track, a sports terrain or a racecourse, in which the ground is first levelled by bulldozers, in the following step not only sand of defined particle size distribution but also modified ungraded materials may be brought in as new material.
It is also an object of the invention to enable the most varied of ungraded materials to be modified in order to enable them to be adapted as constituents of a subjacent layer which prepare the levelled ground for a new function, such as the use as a track, as a sports terrain, operating site, racecourse, etc.
Likewise the invention has to enable damaged roads to be repaired by reusing the granulates already in place or bringing in new powders or granulates.
The object of the invention is also to propose a product allowing reinforcement which is compatible with the usual additives to sand, such as hydraulic binders.
It is known, in particular from Patent Application WO 91/17311, to add, to fine sand of particle size defined by the ratio d/D in which d corresponds to the particles of small diameter and D to the particles of larger diameter, this sand satisfying the relationships d=0 and D<=6 mm, synthetic fibres in a quantity approximately lying between 0.2 and 5 per thousand by weight, preferably between 0.5 and 1 per thousand.
The synthetic fibres have a length from 15 to 100 mm and their diameter lies between 30 and 100 .mu.m. Fibres made from various materials are mentioned, the examples relating to polyacrylonitrile fibres.
The invention, by virtue of the choice of a suitable material and of the use of novel methods for incorporating the fibres into the inorganic granulates provides a product which is of superior quality, easier to employ and, taking everything into account, less expensive.
Techniques are also known for fixing sandy terrains in which a textile filamentary network, produced from at least one cable of continuous yarns, is incorporated into the sand. Thus, Patent Application FR-A-2,368,211 proposes adding a cable of 27,000 or 100,000 crimped filaments made of polyvinyl chloride, acrylonitrile or viscose in sand in order to stabilize dunes and to seed them. In this case, this is essentially to stabilize embankments and to limit wind erosion.
The inv

REFERENCES:
patent: 3861926 (1975-01-01), Irlam et al.
patent: 4867614 (1989-09-01), Freed

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