Reinforcements and a reinforcement system for stabilized earth

Details Reinforcements and a reinforcement system for stabilized earth Reinforcements and a reinforcement system for stabilized earth

1997-08-13

2000-06-27

Lillis, Eileen Dunn

Hydraulic and earth engineering

Earth treatment or control

Rock or earth bolt or anchor

405258, E02D 1720

Patent

active

060799072

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to improvements to or in connection with reinforcements for use in stabilized or framed earth masses.


PRIOR ART

The technique of stabilizing earth masses by incorporation of flexible reinforcements in the mass itself is in general use throughout the world, and at the present time the basic theoretical principles of its operation are known fairly accurately, these principles having been originally established in British Patent No 1069361 of Henri Vidal, which is now in the public domain, and being briefly summarized below in order to provide a complete statement of the invention.
A mass of natural, unstabilized ground has a potential sliding or fracturing surface, which was initially established by Coulomb as a plane and which, usually passing through the foot of the outer surface of the mass, forms an angle dependent on the internal angle of friction of the ground, with a value of approximately 63.degree. in relation to the horizontal for ground habitually used for this type of construction. Other forms of sliding surface, of circular and generally curvilinear development, are closer to reality. In all cases ground situated on this surface is called an "active wedge".
The fixing of this "active wedge" by means of a resistant front face is what concerns the construction of traditional walls. Fastening it by joining to the ground at the rear, from a front face of lower resistance, is what constitutes the anchored wall technique.
The inclusion of reinforcements distributed in the ground of the mass modifies the characteristics of the latter, so that the boundary of the "active wedge" is situated substantially nearer the outer boundary surface of the mass, with an inclined plane development at the base, which becomes vertical from a certain height onwards, to a separation close to 0.3 H from said outer surface, H being the mechanical height of the mass. Numerous trials and actual measurements made in the last 20 years for the different reinforcement methods employed confirm that the boundary of the "active zone" practically coincides with the position of the maximum tensions in the reinforcement elements. This means that the inclusion of reinforcements distributed in the ground modifies and improves the behaviour of the ground by giving it a certain anisotropy.
These principles have given rise to numerous methods of reinforcement consisting of a more or less light, deformable face, from which reinforcement elements extend towards the ground to be stabilized, in such a manner as to pass across the boundary of the "active zone" and extend over a sufficient length--the "resistant zone"--for the frictional forces of the reinforcement elements relative to the ground to exceed the maximum tension values developed in them (see FIG. 1). It is found that these frictional forces do not develop in a useful manner beyond a distance of 0.8 H of the face, even with low values of H, with the exception of special cases in respect of load and/or configuration of the slope on the mass.
The friction capacity of each reinforcement element is obviously dependent on the useful length behind the "active zone", on the pressure which the ground exerts on its surface, on the area of contact and on the nature of the surface material of the element, which is translated into the coefficient of friction between said material and the ground.
The reinforcements are generally incorporated in the earthwork in successive layers, over which extends a certain thickness of ground, which is compacted and over which is laid the following layer of reinforcements, this pattern being repeated until the total height of the mass is reached. The whole arrangement must be sufficiently stable to support the thrust of the ground at the rear and the thrust of the loads acting on it, with the safety coefficients required.
With these methods, and in a general way, in order to ensure sufficient frictional interaction of the reinforcement elements, it is convenient for a minimum of some 2%, and preferably some 5%, of the area of t

REFERENCES:
patent: 1270659 (1918-06-01), Ravier
patent: 1792333 (1931-02-01), Takechi
patent: 4239419 (1980-12-01), Gillen, Jr.
patent: 4411557 (1983-10-01), Booth
patent: 4649729 (1987-03-01), McDowell et al.
patent: 4955758 (1990-09-01), Hyde

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