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Retaining Walls – Counterfort Engineering Drawings The Smart Masonry wall system is a dry-stacked concrete masonry block wall system and offers quicker and more cost-effective concrete construction solutions by utilising mortar-less technology.

The Australian Masonry Standard AS 3700:2001 restricts the height of free standing walls constructed in 150 series and 200 series block units to approximately 12 times the width of the block, ie 1.6m and 2.2m respectively. Drawings for these are available in Datasheet 20.

Traditional free-standing retaining walls utilise the vertical bending and shear capacities of the concrete masonry for strength and stability. A method of construction to permit greater heights to be retained is to use “counterforts” behind the retaining wall face.

The counterforts are short “wing” walls that project at 90 degrees to the longitudinal axis of the retaining wall external face and are tied with steel reinforcement to the rear of the wall and the reinforced concrete base. In this type of construction, up to the top of the counterforts, the horizontal bending and shear capacities of the concrete masonry are utilised for strength and stability. The retaining wall above the tops of the “counterforts” is then designed as a typical free-standing retaining wall.

The absence of mortar, combined with the complete filling of internal voids due to the high strength, high slump and fine aggregate core-filling grout used, results in a wall which is less permeable and more resistant to moisture penetration than conventional mortared masonry. Smart Masonry walls however have a similar texture to conventional masonry walls. Smart Masonry are ideally suited to both free standing and counterfort retaining walls and may be left bare or coated to provide a suitable finish. A thinner render coating is achievable due to the improved alignment of blocks and the absence of mortar.

There are drawings and tables for both the 150 series (140mm wide) block and for the 200 series (190mm wide) block for the following five heights of walls.

(a) 150 series Smart Blocks - 2.4m, 3.0m, 3.6m

(b) 200 series Smart Blocks - 4.2m; 4.8m

Counterfort Retaining

Walls

Claybrick and Paver Design and Advisory Service Pty Ltd 18 Bergion Street, Rochedale South

QLD 4123, Australia

Structural Certification – Counterfort Retaining Walls 1. Description

The following Certification applies to counterfort retaining walls described in Smart Masonry Counterfort Retaining Walls Data Sheet No 52. 2. Loads & Design Assumptions

(a) Dead and Live Loads – Normal (b) Surcharge Loads – Nil (c) Soil Friction Angle – 27 degrees (d) Back Fill – free draining material compacted to Class II Material Strength – Density = 19 kN/cubic metre (e) Foundations – Natural in-situ soil material - Minimum Safe Bearing Pressure – 150 kPa (f) Smart Masonry Strength

(i) Compression • Characteristic unconfined compressive strength of unit, f’uc = 25MPa • Characteristic compressive strength of grouted masonry, f’mg = 9.6MPa • Design characteristic compressive strength of Smart Masonry core filling grout, f’cg = 32 MPa. (ii) Bending • Characteristic compressive strength of masonry, f’m = 25 MPa (iii) Shear • Characteristic shear strength of reinforced masonry, f’vm = 0.35 MPa

(g) Yield Strength of Steel Reinforcement, f’sy = 400 MPa 3. References

The following information was consulted during the design of the Counterfort retaining walls: (a) AS 1170.1 SAA Loading Code (b) AS 4678 – 2002 Earth-retaining Structures (c) AS 3600 – 2001 Concrete Structures (d) AS 3700 - 2001 Masonry Structures (e) Smart Masonry Test Reports

4. Certification It is certified that provided the counterfort retaining walls are constructed with Smart Masonry concrete blocks with f’uc = 25 MPa, good building practice in accordance with AS 3700-2001, in accordance with the drawings contained in Smart Masonry Counterfort Retaining Wall Data Sheet No. 52, and provided the design loads are not exceeded and the design assumptions are followed; then the structures will be structurally stable.

W.J.Moore PC Eng, B.E. Civil R.M.I.T R.P.E.Q. 2403 29th August, 2002

Block Quantities (approximate estimates) Table (A): Number of Blocks in Wall Face & Counterforts, for a single Counterfort spacing (1).

Wall Height Counterfort(m) Spacing (m)

15.01 15.03 15.21 20.01 20.03 20.21 15.01 20.012.4 1.8 - 7 7 543.0 1.4 4 10 10 533.6 1.2 12 17 13 544.2 1.6 - - - 12 16 12 844.8 1.2 - - - 28 23 16 72

Note (1): Block quantities include blocks contained in one counterfort, for each counterfort spacing. Allowance must also be made for blocks in wall over-run at wall ends.

Table (B): Number of Blocks per metre length of Wall Face (includes blocks in Counterforts)Wall Height Counterfort Block Type and Quantities in Total Wall/m Length of Wall

(m) Spacing (m) 15.01 15.03 15.21 20.01 20.03 20.21 150 series 200 series2.4 1.8 30 4 4 383.0 1.4 41 8 8 573.6 1.2 55 15 11 814.2 1.6 60 6 8 744.8 1.2 84 20 14 118

Counterforts only (quantities based on single counterfort wall) Wall Face

Total

Block Type and Quantities

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Any use of this brochure for building systems other than the Smart Masonry Building System is prohibited. For applications outside the scope of this publication or where there are specific local authority requirements, consult a Registered Professional Engineer. Smart Masonry reserves the right to

change the details in this publication without notice. ©Smart Masonry Pty Ltd ABN 75 086 712 665

SM-C

118-

-01 Available from:

SPECIFICATION – SMART MASONRY COUNTERFORT RETAINING WALLS 1.0 INTRODUCTION

The Smart Masonry counterfort retaining wall system consists of a reinforced concrete base supporting a reinforced and grouted Smart Masonry dry stack block wall. The wall is reinforced with vertical and horizontal bars with the vertical bars lapping with the starter bars from the base. The wall is core-filled with Smart Masonry grout.

2.0 DESIGN ASSUMPTIONS - LOADINGS (a) Design details are provided for a level back-fill with no surcharge. (b) The counterfort wall has been designed to retain the following materials:

- Type A material – material having an effective friction angle of 30 degrees (min); being sands, gravel or rock materials; - Type B material – material having an effective friction angle of 25 degrees (min); being coarse-grained soil with silt particles

3.0 WALL FOUNDATION Construct the wall base in sound natural soil (Type A or B material) or rock having a minimum allowable bearing pressure of 150 kPa. Professional engineering advice should be sought if founding conditions other than these are encountered, in particular soft, poorly drained, or filled ground; ground containing organic matter; aggressive soils; or heavily fractured rock.

4.0 BACK-FILLING The design assumes coarse grained, free draining soil without the inclusion of fine soil particles (clean sand or gravel, broken rock) compacted to Class II requirements. An appropriate drainage system is required at the base of the wall, on the soil retention side, so that excess water is removed to a drainage point beyond the ends of the wall.

5.0 DURABILITY REQUIREMENTS For 150 series walls applications within 1 km of the coast, horizontal steel reinforcement in the front (exposed) face of the wall should be hot dipped galvanised.

6.0 MATERIAL SPECIFICATION • Block: Characteristic unconfined compressive strength of masonry unit, f´uc = 25 MPa • Wall: Axial compression - Characteristic compressive strength of grouted masonry, f´mg = 9.6 MPa

Bending - Characteristic compressive strength of grouted masonry, f´m = f’uc = 25 MPa • Grout: Design characteristic compressive strength of Smart Masonry core-filling grout, f´cg = 32 MPa; 250mm slump; 3 to 4mm

nominal maximum aggregate size • Base Concrete: f´c = 25 MPa, 100mm slump. • Reinforcement: Grade 400Y as shown on drawing • Base Concrete Cover = 50mm (min) • All concrete masonry workmanship and materials shall be in accordance with AS3700-2001 • All concrete construction shall be in accordance with AS3600-2001 • All reinforcing bars shall conform to AS/NZS4671-2001

7.0 CONSTRUCTION REQUIREMENTS a) Excavate wall footings such that steps in the concrete base accommodate a height change in increments of 200mm (to suit blockwork

coursing). b) Place base reinforcement, including wall starter bars, accurately in position in accordance with the drawing. Use a template or similar

means to restrain starter bars during concrete placement. c) Place base concrete using mechanical vibration and finish the base top surface accurately to the required levels with a wood float. d) Lay the first course of Smart Masonry blocks on a Smart Masonry Grout levelling base, using a stringline to ensure the course is plumb

and horizontal. Construct the wall generally in accordance with Smart Masonry Data Sheet 5 “How to install the Smart Masonry system”.

e) Provide 40mm dia. Weepholes at 2.4m cs through the wall in the first blockwork course above the top of the base height for all walls 1.8m and higher. Locate the hole away from the block’s internal webs.

f) Core-fill the wall using Smart Masonry Grout. Compact grout using a pencil vibrator (preferred), or by rodding. g) Install waterproofing membrane to rear of wall, if required. h) The contractor is responsible for maintaining the structure, and neighbouring structures, in a safe and stable condition during

construction. i) Install specified drainage behind the wall and carefully backfill, compacting as necessary as the work proceeds. Compact a clay

capping layer in the upper 200mm of the backfill so as to prevent water flowing down behind the wall.