Design Guide for MassBlocä Retaining Walls

1 Design Guide for massbloc Retaining Walls (less than 3m high) Version May 2002 CSP Pacific Ph 0800 655 200 Version May 2002 Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 2 Table of Contents No. Section Page 1. General 2 2. Applications 3 3. Advantages 4 4. Design Approach 5 5. Technical Specifications 7 6. Installation Guide 10 7. Standard Design Guide 12 8. Supply Information 16 Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 3 General These notes have been compiled to aid in the Design of MassBlocTM Retaining Walls . The standard Design tables presented in this Guide shall be only used for preliminary Design of Walls LESS THAN 3m high ( 3 standard blocks high ). All Walls shall require detailed investigation and specific Design by a suitably qualified Engineer. Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 4 Applications MassBlocTM can be used in a variety of situations with the flexibility of a number of different Design solutions available, which allows them to be applied to difficult sites.

2 Retaining Walls Facing for bridge abutments Stream channelisation and erosion protection Coastal protection (beach front erosion protection) Tunnel entrance Walls Culvert wing Walls Slip repairs Temporary traffic parking barriers Temporary bin storage Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 5 Advantages Performance: MassBlocs are relatively flexible structures that are typically based on a compacted aggregate foundation. As wall construction is mortarless this dry stacked system can tolerate movement and settlement without causing visual distress at the face. Permeability: MassBlocs are highly permeable. This permeability can be supplemented by draincoil, which will further reduce the development of hydrostatic pressure behind the blocks. Durability: MassBlocs are manufactured from wet-cast concrete that results in a durable Retaining wall system. The blocks are resistant to cracking and do not rust or deform like gabions.

3 Speedy Installation: Two experienced workers and an excavator can place up to 70m of wall per day. Blocks are placed using the galvanised lifting eye, which is cast into the top of each block. Ecologically Friendly: MassBlocs are an ecologically safe building component. The blocks are manufactured from naturally occurring materials that are in abundant supply and are extracted with minimal environmental impact. MassBlocs are eco-friendly! Economics: MassBlocs are competitively priced and when all project costs are measured and compared against the speed of installation, durability and in-situ performance they represent excellent value for the construction dollars invested. No other system can beat MassBlocs in terms of speedy installation, durability and in-site performance. Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 6 Design Approach MassBlocsTM are essentially a gravity wall structure that depends on the mass of the blocks to resist the destabilising forces due to the retained soil and surcharge loadings.

4 As with all gravity type wall structures, there are three modes of failure by which a wall can fail. All three require careful analysis to ensure both safety and performance of the wall is maintained for the Design life of the structure. External Stability The three modes for which gravity Retaining Walls must be designed to ensure external stability are: Overturning: the wall fails by rotating about the toe of the wall Sliding: outward movement of the wall along its base Bearing Capacity: failure of the foundations causing the wall to lean over To guard against any of these failure modes occurring, the common practice is to Design the wall with a predetermined factor of safety designed in. These predetermined factors of safety are outlined below and are consistent with currently accepted Design practice. Failure Mode Recommended Minimum Factor of Safety Overturning Sliding Bearing Capacity As for all structures, the degree of uncertainty over Design parameters - and the consequences of the structure failing - dictate the level of safety required.

5 For the designs contained in this document, the factors of safety are defined above. In situations where the structure is to become a critical structure, where failure would cause significant property damage or even loss of life, then we recommend that higher safety factors be used. It is recommended that a suitably qualified geotechnical engineer undertake a detailed soils investigation. Internal Stability When considering the reinforced earth Retaining wall utilising geogrid the number and layout must also be determined to ensure that the reinforced fill does not fail internally. Two modes of failure have been checked and allowed for in the Design charts. Pull out failure: the geogrid pulls out of the soil without rupture Tensile rupture of the geogrid: the geogrid is stressed beyond its allowable tensile limit. Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 7 To guard against any of these failure modes occurring, the common practice is to Design the wall with a predetermined factor of safety designed in.

6 These predetermined factors of safety are outlined below and are consistent with currently accepted Design practice. Failure Mode Recommended Minimum Factor of Safety Pull out failure Tensile rupture of the geogrid All Geo-grid shown in the Design cross sections is Tensar SR 80 and the designs are based exclusively for this type of grid and granular backfill (2mm 20m). The spacing and number of layers shown in the Design Guide are only applicable to Design parameters shown. The Design solutions are only to be used as a Guide and where the parameters vary a suitably qualified engineer should be engaged to ensure that the appropriate Design solution is chosen. As for all structures the degree of uncertainty over Design parameters and the consequences of the structure failing dictate the level of safety required. For the designs contained in this document the factors of safety are defined above. In situations where the structure is to become a critical structure, where failure would cause significant property damage or even loss of life, then we recommend that higher safety factors be used.

7 Drainage Considerations MassBlocsTM are constructed from a no fines concrete mix that allows water to easily permeate through the blocks. This effectively allows the wall to drain naturally. Filter fabric and drain coil are also included to ensure that no hydrostatic pore pressure is able to accumulate and destabilise the wall. This is more of a precautionary measure and included as part of good Design practice. Seismic Considerations MassBlocTM Walls are designed to be relatively flexible and can undergo small changes in line and level without adversely affecting their structural integrity. The effects of seismic conditions on 3m high or less Walls are minimal and have not been allowed for in this manual. If a situation arises where additional seismic forces need to be allowed for, it is recommended that a suitably qualified structural engineer be engaged to carry out the seismic analysis. Global Stability MassBlocTM Walls must also be analysed for global stability.

8 This shall be undertaken by a suitably qualified geotechnical engineer. They must consider potential failure surfaces passing through the backfill and foundation soils. Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 8 Technical Specifications Base Unit Dimensions Face width 1185mm Vertical height of front face 1000mm Vertical height of rear face 1000mm Depth of unit 880mm Block weight tonne Standard Unit Dimensions Face width 1185mm Vertical height of front face 1000mm Vertical height of rear face 1150mm Depth of unit 880mm Block weight tonne For Design flexibility, blocks of varying heights and width may be ordered (note: maximum height is 1000mm and maximum width is 1185mm) Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 9 Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 10 Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 11 Installation Guide Note.

9 This information is provided as a Guide only. The registered engineer's Design details shall take precedence if there is any conflict or ambiguity with this information. Step One Excavate the base to the required depth This will be site dependent - generally 1200mm wide and 200mm deep Step Two Place GAP65 (or equivalent) into trench then compact to engineer s requirements (100kpa as a basic Guide ) Use a laser level for the best result Place a layer of binding material ( GAP7 on sand) up to 20mm thick over the entire foundation Use a screed to achieve a perfect level front to back and end to end Step Three Set string line or conduit approximately 10mm from the front of the massbloc wall Blocks can be placed onto the base using an excavator with a certified chain and swift lift Should the work area be within reach of the hiab, blocks can be delivered and placed directly from the truck Care must be taken so that the block is not damaged when unloading or placing Step Four Lower the massbloc base unit approximately 30mm from the prepared base and move the unit slowly into position and then lower fully Each consecutive block is lowered 30mm from base keeping 20mm away from previously placed block Design Guide for massbloc Retaining Walls (less than 3m high)

10 CSP Pacific Ph 0800 655 200 Page 12 Once the front face is positioned correctly, slowly move the block to touch the adjoining block Using a spirit level, check that each block is level Step Five Once the base is level front to back and side to side, standard blocks can be placed on top Step Six Back filling - the engineer's details will provide the required method. Options include: Firth no fines concrete mix (Flowable Fill ) Reid Bars Manta Rays Geogrids between each unit Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 13 Standard Design Guide GRAVITY WALL / LEVEL BACKFILL / VEHICLE SURCHARGE g = 20kN/m3 C = 0 F = 300 Retaining wallheight, : Concrete placed behind the wall is to be highMassbloc Gravity Retaining Wall With Additional Concrete Mass For a Vehicle Surcharge of 12kPaVehicle Surcharge Design Guide for massbloc Retaining Walls (less than 3m high) CSP Pacific Ph 0800 655 200 Page 14 GRAVITY WALL / SLOPING BACKFILL / NO SURCHARGE g = 20kN/m3 C = 0 F = 300 Retaining wallheight.