GB1601965A

GB1601965A - Reinforced earth structures

Info

Publication number: GB1601965A
Application number: GB2029478A
Authority: GB
Original assignee: TRANSPORT SECRETARY OF STATE F
Current assignee: TRANSPORT SECRETARY OF STATE F
Priority date: 1978-05-23
Filing date: 1978-05-23
Publication date: 1981-11-04

Description

(54) IMPROVEMENTS IN OR RELATING TO REINFORCED EARTH STRUCTURES (71) I, SECRETARY OF STATE FOR TRANSPORT, LONDON, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to reinforced earth structures.

Such structures comprise natural earth in which is embedded a plurality of reinforcing members, the reinforcing members usually being attached to facing units which define at least a part of a structure. Such structures may be cuttings or embankments produced in connection with road works in which the facing units constitute retaining walls. Reinforced earth construction is advantageous in that the soil can be contained by retaining walls of much less massive construction than would be the case otherwise especially with particulate soils such as sands and gravel where there is little or no cohesion between particles, frictional contact between reinforcing elements and the soil acting to enhance the stability of the structure.

Earth reinforcement is also applicable to more cohesive soils such as clay, with or without an admixture of soils of a more granular nature.

Clay soils have a tendency to become compacted unevenly which can give rise to variations in stress acting on retaining walls which could cause failure; this is due in part to the water holding nature of cohesive soils such as clay and the problem can be aggravated in wet locations or by inclement weather.

The invention is directed, as are parent application 39145/77 and Serial no. 1 601 964 and co-pending divisional application thereof 20296/78, Serial no. 1601967, to reinforced earth structures having some flexibility to accommodate uneven compacting of soil and also to enable a variable configuration to be achieved. One object is the provision of drainage means within reinforced earth structures.

According to the invention, a facing unit for a reinforced earth structure comprises a member having extended portions formed on opposite parallel sides thereof, the extended portion on one side extending partially along that side from or near one end thereof and the extended portion on the other side extending from or near the other end thereof, along that part of the side opposite to that part of the first-mentioned side not occupied by the extended portion thereon, one extended portion having a rod protruding therefrom and the other extended portion having a bore hole formed therein, the rod and the bore hole being substantially parallel to each other and to the respective sides.

A facing unit may be provided with external or internal drainage channels and the channels may contain water absorbent material.

An embodiment of the invention will now be described by way of example only with reference to Figures 3 and 4 of the drawings accompanying the Provisional Specification which are respectively an elevation and plan view of facing units forming part of a reinforced earth structure.

The figures show a construction including interconnected facing units. The facing units each consist of a rectangular concrete slab 5 having extended portions 6, 7 of thickened section formed on its longer sides. One extended portion 6 is formed on the lower half of one side and has a bore extending through it. The other extended portion 7 is formed on the upper half of the other side and. has a steel rod 8 embedded in it with the ends of the rod protruding above and below the extended portion. A facing comprises a series of facing units assembled together so that the downwardly protruding portion of a steel rod 8 fits down into the bore hole of the next adjacent unit thus connecting the units together.A further course may be assembled on top of a previous course with the upwardly protruding portions of the steel rods 8 in the extended portions 6 of the lower course engaging upwards into the bore holes in the extended portions 7 of the further course.

Adjacent facing units in a course can be assembled in line with each other to form a straight wall or they may be assembled at right angles. By suitable shaping the section of the extended portions 6, 7 as by rounding off corners instead of chamfering as shown, it is possible to vary the angles between adjacent facing units as may be desirable. Stabilising, or reinforcing, elements (not shown), usually comprising metal strips with holes or hooks at one end, are attached either to the lower portions 9 or the upper portions 10 of the rods 8 being thus disposed respectively between adjacent facing units in one course or between those in successive courses, the free ends of the stabilising elements extending into earth fill which is consolidated around them as erection of the facing proceeds.Stabilising elements can conveniently be of other material, and as glass reinforced plastics or webbing. providing that it has adequate tensile strength and has a surface which will maintain good frictional control with the earth file. One form of stabilising element comprises a prestressed concrete beam with its surface suitably roughened and provided at one end with a metal loop for attachment to the facing.

Alternatively, facing units may be provided as shown in the drawing with one or more brackets 11 on their rear faces, ie the faces directed towards earth fill, for the attachment of stabilising elements. The brackets are of U-section with holes in their opposite arms to receive pins for connecting to stabilising elements. Preferably the brackets have arms spaced apart to permit relative vertical movement between facing panels and stabilising elements and with some packing 20 of a flexible or compressible material inserted to enable full advantage being taken of this feature while inhibiting undue relative movement.

In a modification, a vertical clearance is provided between facing units by rebating the upper surfaces of the extended portions 6, 7 as shown in dotted lines at x, y in Fig. 3.

This permits vertical banks of units to move independently of those on either side to accommodate uneven settlement of earth fill.

Build-up of water in wet conditions can lead to the imposition of hydraulic loadings on facings in addition to those directly due to earth fill.

Improved drainage can be achieved by forming channels in facing units. Channels can be formed in the earth bearing face of a facing unit, or within the facing unit itself, and connected to the earth bearing face by passages. Water passing into the channels drains to suitable collection means from which it may be conducted away. The effectiveness of this arrangement can be enhanced by the use of water absorbent material such as porous plastic or sintered metal whereby water is attracted by capillary action. Alternatively, water absorbent material may be applied directly on the earth bearing faces of facing units in the form of a sheet which will serve to conduct water away.

The water may be conducted to specially formed ducts, to existing weep holes such as are commonly provided in facing units, or weep holes may be specially provided.

Improved drainage can also be obtained, especially with cohesive soils, by interposing granular material, such as gravel, between the main earth fill and facings.

WHAT I CLAIM IS: 1. A facing unit for a reinforced earth structure comprising a member having extended portions formed on opposite parallel sides thereof, the extended portion on one side extending partially along that side from or near one end thereof and the extended portion on the other side extending from or near the other end thereof along that part of said side opposite to that part of first mentioned side not occupied by the extended portion thereon, one extended portion having a rod protruding therefrom and the other extended portion having a bore hole formed therein, the rod and the bore hole being substantially parallel to each other and to the respective sides.

2. A facing unit for a reinforced earth structure according to claim 1 provided with attachment means for the connection of a stabilising element.

3. A facing unit for a reinforced earth structure according to claim 1 or claim 2 having a channel formed in it.

4. A facing unit for a reinforced earth structure according to claim 3 in which the channel is formed internally in the unit and is connected to the outside thereof by a passage or passages.

5. A facing unit for a reinforced earth structure according to claim 3 or claim 4 in which a water absorbent material is disposed within the channel.

6. A facing for a reinforced earth structure comprising a plurality of interconnected facing units as claimed in any of claims 1-5.

7. A facing for a reinforced earth structure according to claim 6 in which the rods in at least some of the facing units engage the bore holes in adjacent facing units.

8. A facing for a reinforced earth structure according to claim 6 or claim 7 in which individual rods protrude in opposite directions from the respective extended portions to engage the bore holes in facing units

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. together. A further course may be assembled on top of a previous course with the upwardly protruding portions of the steel rods 8 in the extended portions 6 of the lower course engaging upwards into the bore holes in the extended portions 7 of the further course. Adjacent facing units in a course can be assembled in line with each other to form a straight wall or they may be assembled at right angles. By suitable shaping the section of the extended portions 6, 7 as by rounding off corners instead of chamfering as shown, it is possible to vary the angles between adjacent facing units as may be desirable. Stabilising, or reinforcing, elements (not shown), usually comprising metal strips with holes or hooks at one end, are attached either to the lower portions 9 or the upper portions 10 of the rods 8 being thus disposed respectively between adjacent facing units in one course or between those in successive courses, the free ends of the stabilising elements extending into earth fill which is consolidated around them as erection of the facing proceeds.Stabilising elements can conveniently be of other material, and as glass reinforced plastics or webbing. providing that it has adequate tensile strength and has a surface which will maintain good frictional control with the earth file. One form of stabilising element comprises a prestressed concrete beam with its surface suitably roughened and provided at one end with a metal loop for attachment to the facing. Alternatively, facing units may be provided as shown in the drawing with one or more brackets 11 on their rear faces, ie the faces directed towards earth fill, for the attachment of stabilising elements. The brackets are of U-section with holes in their opposite arms to receive pins for connecting to stabilising elements. Preferably the brackets have arms spaced apart to permit relative vertical movement between facing panels and stabilising elements and with some packing 20 of a flexible or compressible material inserted to enable full advantage being taken of this feature while inhibiting undue relative movement. In a modification, a vertical clearance is provided between facing units by rebating the upper surfaces of the extended portions 6, 7 as shown in dotted lines at x, y in Fig. 3. This permits vertical banks of units to move independently of those on either side to accommodate uneven settlement of earth fill. Build-up of water in wet conditions can lead to the imposition of hydraulic loadings on facings in addition to those directly due to earth fill. Improved drainage can be achieved by forming channels in facing units. Channels can be formed in the earth bearing face of a facing unit, or within the facing unit itself, and connected to the earth bearing face by passages. Water passing into the channels drains to suitable collection means from which it may be conducted away. The effectiveness of this arrangement can be enhanced by the use of water absorbent material such as porous plastic or sintered metal whereby water is attracted by capillary action. Alternatively, water absorbent material may be applied directly on the earth bearing faces of facing units in the form of a sheet which will serve to conduct water away. The water may be conducted to specially formed ducts, to existing weep holes such as are commonly provided in facing units, or weep holes may be specially provided. Improved drainage can also be obtained, especially with cohesive soils, by interposing granular material, such as gravel, between the main earth fill and facings. WHAT I CLAIM IS:

1. A facing unit for a reinforced earth structure comprising a member having extended portions formed on opposite parallel sides thereof, the extended portion on one side extending partially along that side from or near one end thereof and the extended portion on the other side extending from or near the other end thereof along that part of said side opposite to that part of first mentioned side not occupied by the extended portion thereon, one extended portion having a rod protruding therefrom and the other extended portion having a bore hole formed therein, the rod and the bore hole being substantially parallel to each other and to the respective sides.

disposed adjacently in the lateral and vertical senses.

9. A facing for a reinforced earth structure according to claim 7 or claim 8 in which a clearance is provided between surfaces of extended portions from which rods project and the mating surfaces containing the bore holes engaged by the rods.

1().

A facing for a reinforced earth structure according to any of claims 6--9 in which at least some of the facing units are provided with brackets for the connection of stabilising elements.

I I. A reinforced earth structure comprising a facing unit as claimed in any of claims l---5 and a stabilising element connected to the facing unit.

12. A reinforced earth structure according to claim ll in which the stabilising element is connected to the rod.

13. A reinforced earth structure comprising a facing as claimed in any of claims 6--10 and stabilising elements connected to at least some of the facing units.

14. A reinforced earth structure comprising a plurality of facing units at least some of which have one extended portion formed on each of their espective sides and extending from the opposite ends of the sides, and a rod protruding from one of the extended portions and a bore hole in the other extended portion arranged in such manner that the rod of a facing unit will engage the bore hole of an adjacent facing unit. and stabilising elements connected to at least some of the facing units.

15. A reinforced earth structure according to claim 14 in which a clearance is provided between surfaces of extended por tions from which rods protrude and the mating surfaces containing the bore holes engaged by the rods.

16. A reinforced earth structure according to claim 14 or claim 15 in which at least some of the stabilising elements are connected to the rods.

17. A reinforced earth structure according to claim 14 in which at least some of the facing units are provided with brackets to which the stabilising elements are connected.

18. A reinforced earth structure according to claim 17 in which brackets have arms spaced apart to provide clearance between the arms and the attachment portion of a stabilising element.

19. A reinforced earth structure according to claim 15 and claim 16 or claim 17 in which packing of a flexible or compressible nature is interposed within the clearance.

20. A reinforced earth structure according to any of claims 11-19 comprising earth fill extending around the stabilising elements.

21. A facing unit for a reinforced earth structure substantially as herein described with reference to Figures 3 and 4 of the drawings accompanying the Provisional Specification.

22. A facing for a reinforced earth structure substantially as herein described with reference to Figures 3 and 4 of the drawings accompanying the Provisional Specification.

23. A reinforced earth structure substantially as herein described with reference to Figures 3 and 4 of the drawings accompanying the Provisional Specification.