1
EARTH STRUCTURES
The invention relates to earth structures, certain components for use in earth structures and to methods of constructing earth structures.
It is known from European Patent Application No. 0 318 243 to provide an earth structure frictionally stabilised by a plurality of elongate stabilising elements in the form of strips extending rearwardly from a facing of the structure into an earth mass. The earth is stabilised throughout the mass by frictional engagement with the strips, thereby enabling the earth mass to behave as an elastic material with greatly improved resistance to failure. The facing of the known structure consists of a series of rows of "C" shaped mesh facing panels arranged one above another. The panels in each row are supported by laterally spaced support straps. These are also "C" shaped, each having an upright front portion in front of the panels and relatively short upper and lower rearwardly extending portions. These upper and lower portions are connected to an earth stabilising strip. Thus the forward end of each stabilising strip is located between a rearwardly extending upper portion at the top of a support strap in one row and a rearwardly extending lower portion at the bottom of a support strap in the row above. A bolt passes through the upper and lower rearwardly extending portions and the stabilising strip to form a secure connection.
The advantages of using facing panels formed of mesh are that they are lightweight and thus inexpensive compared to eg. concrete panels and that they allow the growth of vegetation on the facing, thus giving it a "green" appearance. However, because of their lightweight nature, the mesh facing panels are flexible and thus subject to deformation. In particular, there is a tendency for the facing panels to bulge out where they span between the laterally spaced support straps. If it were desired, for aesthetic or other reasons, not to use the support straps and to connect the stabilising strips directly to the mesh facing panels, there would be an increased tendency for the panels to deform.
Viewed from one aspect, the invention provides an earth structure comprising a plurality of elongate stabilising elements in an earth mass behind a mesh facing, and a plurality of connectors behind the facing and connecting it to the stabilising elements, each connector having a rear attachment portion attached to a respective earth stabilising element, and having at least two spaced apart front attachment portions attached to the mesh facing.
It will be appreciated that the forward earth pressure on the mesh facing is withstood by the stabilising elements connected to the facing via the connectors. By attaching each connector to the mesh facing by the spaced apart front attachment portions, the load on the mesh racing applied by the connector is distributed between those attachment portions, thereby reducing the deflection of the facing.
In fact, the connector arrangement may be useful with other types of facing where it is desired to limit the deflections by distributing the load thereon.
Thus, viewed from another aspect, the invention provides an earth structure comprising a plurality of elongate stabilising elements in an earth mass behind a facing, and a plurality of connectors behind the facing and connecting it to the stabilising elements, each connector having a rear attachment portion attached to a respective earth stabilising element, and having at least two spaced apart front attachment portions attached to the facing. For example, the facing may be made of a sheet or sheets of eg. metal.
The invention also provides a connector for use in the earth structures described herein. In one broad aspect, the
2
invention provides a connector for connecting an earth stabilising element and a facing, comprising a rear attachment portion for attachment to an earth stabilising element, and at least two spaced apart front attachment portions for 5 attachment to a facing. The front attachment portions may take any convenient form but are preferably arranged to hook on to a bar or lug of the facing. Thus each front attachment portion may be in the form of a hook. In a preferred embodiment, the connector has two front attach
io ment portions and is substantially "V" shaped. The front attachment portions are preferably spaced apart in a horizontal or lateral direction. The connector may be formed by bending a bar, for example a 14 mm diameter steel bar. The connectors are preferably capable of pivoting about
15 a horizontal axis at the facing. This can advantageously permit the connectors to be at an appropriate orientation, normally horizontal, for any angle of facing. In general, the slope of the facing can vary between 45° to the horizontal and vertical (90° to the horizontal). Pivotability of the
20 connectors can advantageously be achieved by the hooks described above, which can pass round at least one substantially horizontal bar of the facing.
The connectors extend rearwardly into the earth so as to have a length in this direction which is substantially less than
25 the length of the stabilising elements, for example less than one quarter, preferably less than one fifth.
In a preferred embodiment, a mesh facing comprises mesh panels arranged one above another, and the connectors connect a substantially horizontal bar of a lower facing panel
30 with a substantially horizontal bar of an upper facing panel arranged above the lower facing panel. Thus the connectors serve to connect lower and upper facing panels together as well as to connect the facing to the stabilising elements. The facing may be made up of mesh facing panels which are
35 substantially "L" shaped in vertical cross-section. Typically, the front portion of the "L" will be substantially longer than the rearwardly extending portion, for example at least five times longer and preferably ten times longer.
The use of "L" shaped panels rather than the known "C"
40 shaped panels results in more potential deformation along the horizontal joint between the panels, because the rearwardly extending portion at the top of the panels is omitted, thereby reducing the stiffness of the panels. However, the use of a connector having at least two spaced apart attach
45 ment portions attached to the facing panel compensates for the loss of stiffness.
The "L" shaped panels can be used to form vertical facings and also non-vertical facings, even if the angle between the front portion and rearwardly extending portion
50 of the "L" is 90°, if the connectors are pivotably attached and thus do not have to be at the same orientation as the rearwardly extending portion of the "L". This advantageously permits standardisation of the facing panels for facings of different slopes. Moreover, a particular facing can
55 have portions of different slopes whilst still using the same panels.
The connectors are preferably arranged to permit relative vertical movement between the lower and upper facing panels. This can be achieved by the hooks described above,
60 having a vertical play which is greater than the combined thickness of the two horizontal bars. Thus, in a preferred construction method, the horizontal bar of an upper facing panel may be spaced upwardly from the horizontal bar of a lower facing panel by a wedge. This determines the position
65 of the connector and thus the position of the stabilising element in the earth behind the facing. Once the upper facing panel has been backfilled the wedge can be removed and as
