Retaining Wall Retaining walls 11.2

(sketch)

Design The retaining wall is designed to support the weight of soil in the wedge between the angle of repose and the back of the wall. To prevent sliding a rib or heel is added to underside of the footing Retaining walls more than 1.2m high require a consent from the Territorial authority.

The retaining wall is designed to support the weight of soil in the wedge between the angle of repose and the back of the wall.

To prevent sliding a rib or heel is added to underside of the footing

Retaining walls more than 1.2m high require a consent from the Territorial authority.

(sketch again ,it is good practice)

Wall design Surcharge Any additional loading which can be imposed above the level of the completed retaining wall and within a distance equal to the height of the wall. This includes vehicles, buildings, etc. Angle of repose The safe slope of an excavated face for the type of ground where it will not move under its own weight.

Design Overturning does not occur Sliding does not occur Soil is not overloaded

Overturning does not occur

Sliding does not occur

Soil is not overloaded

Design Shape and type of wall is determined by. Position of the wall in relation to boundary Height of the wall Type of soil to be retained Material to be used for the wall Type of drainage Access to site Sub soil for bearing strength Moisture control

Shape and type of wall is determined by.

Position of the wall in relation to boundary

Height of the wall

Type of soil to be retained

Material to be used for the wall

Type of drainage

Access to site

Sub soil for bearing strength

Moisture control

Methods of Failure Fracture Overturn Slide

Reasons for Drainage The accumulation of ground water behind a retaining wall can cause serious problems including: Pressure build-up behind the wall causing movement in the wall. Encouraging the growth of mould and algae. The lifting of finishes applied to the wall.

The accumulation of ground water behind a retaining wall can cause serious problems including:

Pressure build-up behind the wall causing movement in the wall.

Encouraging the growth of mould and algae.

The lifting of finishes applied to the wall.

DrainageRequirements behind walls A 100mm diameter perforated pipe installed at the base of the wall above the footing and below floor level A minimum of 100mm of free draining material under the pipe. A suitable filter cloth to protect the pipe from silting up. Back-filling of a clean free-draining material. Access to clean the subsoil drain allowing it to continue to function effectively throughout the service life of the building.

A 100mm diameter perforated pipe installed at the base of the wall above the footing and below floor level

A minimum of 100mm of free draining material under the pipe.

A suitable filter cloth to protect the pipe from silting up.

Back-filling of a clean free-draining material.

Access to clean the subsoil drain allowing it to continue to function effectively throughout the service life of the building.

Drain Types Weep holes through wall Drain pipes behind walls taking water to sump box. Core drain sheets

Weep holes through wall

Drain pipes behind walls taking water to sump box.

Core drain sheets

Marley ‘drainflo’

Wall without drainage

Tanking Be continuous around the buried part of the building. Have an approved vapour flow resistance. Have all joints sealed. Be protected against damage. Have a durability rating of not less than 50 years.

Be continuous around the buried part of the building.

Have an approved vapour flow resistance.

Have all joints sealed.

Be protected against damage.

Have a durability rating of not less than 50 years.

Tanking Materials Mastic Asphalt a layer of hot towelled asphalt applied to the wall Reinforced bitumen sheets – 3mm thick heat sealed to the wall and joints. Multilayered polyethylene and rubberized asphalt – self adhesive sheet easily applied to walls Latex emulsion – Two coat paint on sealer (mulseal) Butyl sheeting – same as butynol roofing The surface of tanking must be protected with sheets of fibre cement

Mastic Asphalt a layer of hot towelled asphalt applied to the wall

Reinforced bitumen sheets – 3mm thick heat sealed to the wall and joints.

Multilayered polyethylene and rubberized asphalt – self adhesive sheet easily applied to walls

Latex emulsion – Two coat paint on sealer (mulseal)

Butyl sheeting – same as butynol roofing

The surface of tanking must be protected with sheets of fibre cement

Tanking Protection Light weight rigid sheeting such as Fibre cement Treated ply Oil tempered hardboard Polystyrene Proprietary system drainage mat and protection sheet

Light weight rigid sheeting such as

Fibre cement

Treated ply

Oil tempered hardboard

Polystyrene

Proprietary system drainage mat and protection sheet

Expol Styro-Drain Expanded Polystyrene Drainage Board Styro-drain comes in sheets 1800 x 1200 x 90mm and can be cut with a sharp knife or hand saw

Expol Styro-Drain

Expanded Polystyrene Drainage Board

Styro-drain comes in sheets 1800 x 1200 x 90mm and can be cut with a sharp knife or hand saw

Core Drain sheets

Core Drain sheets

Mega Flow

Geotextile fabric Geotextiles are often used to replace thick expensive granular filters in drainage pplications.

Revision so far. Why is it necessary to make an early assessment of soil types that will support the wall? What factors will need to be taken into account when selecting a retaining wall system? What precautions relation to site boundaries will have to be taken during construction of retaining walls? Name four types of retaining walls? When may it be necessary to provide a safety barrier on top of a retaining wall to comply with the building code? Why I got fired

Why is it necessary to make an early assessment of soil types that will support the wall?

What factors will need to be taken into account when selecting a retaining wall system?

What precautions relation to site boundaries will have to be taken during construction of retaining walls?

Name four types of retaining walls?

When may it be necessary to provide a safety barrier on top of a retaining wall to comply with the building code?

Why I got fired

Water Stops

Water stops Ideal for flat slabs. Lay the waterstop directly on the compacted subgrade, place and finish concrete. Base seal is suitable for construction, contraction (control), and expansion joints.

Ideal for flat slabs.

Lay the waterstop directly on the compacted subgrade, place and finish concrete.

Base seal is suitable for construction, contraction (control), and expansion joints.

Retaining wall types Timber Crib Cantilever Concrete Mass Concrete Crib wall Reinforced concrete Wall Reinforced concrete masonry Gravity Cantilever Crib

Timber

Crib

Cantilever

Concrete

Mass Concrete

Crib wall

Reinforced concrete Wall

Reinforced concrete masonry

Timber retaining walls

Timber Cantilever walls

Timber crib wall Compacted bas course OR Concrete base course Set up on raking angle. Building a crib wall

Compacted bas course

OR

Concrete base course

Set up on raking angle.

Building a crib wall

Timber Crib Wall

Timber Crib Wall

Concrete crib wall

Mass Concrete & Gravity Wall

Gravity walls are made from a large mass of stone, concrete or composite material. Gravity walls depend on the size and weight of the wall mass to resist pressures from behind.

Gravity walls are made from a large mass of stone, concrete or composite material. Gravity walls depend on the size and weight of the wall mass to resist pressures from behind.

Mass Concrete

Concrete block retaining wall

Cantilever Wall Cantilevered walls are made from a relatively thin stem of steel-reinforced, cast-in-place concrete or mortared masonry (often in the shape of an inverted T or L)

Cantilevered walls are made from a relatively thin stem of steel-reinforced, cast-in-place concrete or mortared masonry (often in the shape of an inverted T or L)

Cantilevered Pole Retaining Wall

Temporary Protection for Excavated Faces Soil must be protected from slumping by Cover face with polythene Cover face with bitumen sprayed hessian. For larger excavations use sprayed concrete Support all excavated faces with large timbers and props (to be avoided)

Soil must be protected from slumping by

Cover face with polythene

Cover face with bitumen sprayed hessian.

For larger excavations use sprayed concrete

Support all excavated faces with large timbers and props (to be avoided)

Sheet piling Sewer upgrade in Christchurch

Sewer upgrade in Christchurch

Revision What is meant by the angle of repose? Why is a rib sometimes added to the underside of a retaining wall footing? Name a tanking material suitable for tanking a house basement wall. Draw a cross section of a ‘dumb bell’ water stop. What material would you use for backfill where drainage is required? If an excavated face will not stand in all weathers what will you have to do?

What is meant by the angle of repose?

Why is a rib sometimes added to the underside of a retaining wall footing?

Name a tanking material suitable for tanking a house basement wall.

Draw a cross section of a ‘dumb bell’ water stop.

What material would you use for backfill where drainage is required?

If an excavated face will not stand in all weathers what will you have to do?