CONSTRUCTION TECHNOLOGY & maintenance

CEM 417

SOURCES FROM slide: MOHD AMIZAN MOHAMD MOHD FADZIL ARSHAD SITI RASHIDAH MOHD NASIR FKA, UiTM Shah Alam.

WEEK 2

Stages for construction

1.

2.

3.

4.

Building Retaining walls, Drainage Road, Highway, Bridges Airports, Offshore/Marine structure

RETAINING WALLS

WEEK 2

At the end of week 2 lectures, student will be able to : - Identify the different types of retaining walls and their respective functions. (CO1; CO3)

RETAINING WALL

 Basic function – to retain soil at a slope which is greater than it would naturally assume, usually at a vertical or near vertical position

 Retaining wall failure at the Shin-Kang Dam

 1.

2.

3.

4.

D ESIGN OF RETAINING WALL   retaining walls have primary function of retaining soils at an angle in excess of the soil’s nature angle of repose.

Walls within the design height range are designed to provide the necessary resistance by either their own mass or by the principles of leverage.

Design consideration: Overturning of the wall does not occur Forward sliding does not occur Materials used are suitable The subsoil is not overloaded

F ACTORS WHICH DESIGNER NEED TO TAKE ACCOUNT  Nature and characteristics of the subsoil's  Height of water table – the presence of water can create hydrostatic pressure, affect bearing capacity of the subsoil together with its shear strength, reduce the frictional resistance between the underside of the foundation   Type of wall Materials to be used in the construction

 Failure of retaining wall (dam) due to water pressure..

T YPES OF WALLS

 Mass retaining walls  Cantilever walls  Counterfort retaining walls  Precast concrete retaining walls  Precast concrete crib retaining walls

M

ASS RETAINING WALLS

    Sometimes called slide or overturn

gravity walls

and rely upon their own mass together with the friction on the underside of the base to overcome the tendency to Generally only economic up to 1.8 m Mass walls can be constructed of semi engineering quality bricks bedded in a 1:3 cement mortar or of mass concrete Natural stone is suitable for small walls up to 1m high but generally it is used as a facing material for walls over 1 m

T YPICAL EXAMPLE OF MASS RETAINING WALLS BRICK MASS RETAINING WALL

Stone retaining wall Brick retaining wall

T YPICAL EXAMPLE OF MASS RETAINING WALLS MASS CONCRETE RETAINING WALL WITH STONE FACINGS

C ANTILEVER WALLS

  Usually of reinforced concrete and work on the principle of leverage where the stem is designed as a cantilever fixed at the base and the base is designed as a cantilever fixed at the stem Economic height range of 1.2 m to 6 m using pre stressing techniques  Any durable facing material can be applied to the surface to improve appearance of the wall

Cantilever wall

 Two basic forms:   A base with a large heel A cantilever with a large toe Cantilever T Cantilever L

C ANTILEVER WALLS

C OUNTERFORT RETAINING WALLS

   Can be constructed of reinforced or prestressed concrete Suitable for over 4.5 m Triangular beams placed at suitable centres behind the stem and above the base to enable the stem and base to act as slab spanning horizontally over or under the counterforts

P RECAST CONCRETE RETAINING WALL

    Manufactured from high-grade pre cast concrete on the cantilever principle.

Can be erected on a foundation as permanent retaining wall or be free standing to act as dividing wall between heaped materials which it can increase three times the storage volume for any given area Other advantages- reduction in time by eliminating curing period, cost of formwork, time to erect and dismantle the temporary forms Lifting holes are provided which can be utilized for fixing if required

APPLICATION

P RECAST CONCRETE RETAINING WALLS

P RE CAST CONCRETE CRIB RETAINING WALLS

 Designed on the principle of mass retaining walls  A system of pre cast concrete or treated timber components comprising headers and stretchers which interlock to form a 3 dimensional framework or crib of pre cast concrete timber units within which soil is retained   Constructed with a face batter between 1:6 and 1:8 Subsoil drainage is not required since the open face provides adequate drainage.

SUBSOIL DRAINAGE

At the end of week this lecture, student will be able to : Identify the functions of various subsoil drainage system. (CO1; CO3)

D

RAINAGE

Effluent- can be defined as that which flows out. In building drainage terms, there are three main forms of effluent: 1.

Subsoil water – water collected by means of special drains from the earth primarily to lower the water table level I the subsoil –clean, no need to treat.

2.

3.

Surface water –effluent collected from the surfaces such as roofs, paved areas- clean Foul or soil water –effluent contaminated by domestic or trade waste and require treatment

S

OURCE OF WATER

B

UILDING

R

EGULATION

C2 -R

ESISTANCE TO MOISTURE

    Subsoil drainage shall be provided if it is needed to avoid:   The passage of ground moisture to the interior of the building Damage to the fabric of the building Needed for sites with a high water table (level at which water occurs naturally below the ground) Ob

jective

of subsoil drainage – to lower the water table to a level such that it will not rise to within 0.25 m of the lowest floor of a building Advantages – improve the stability of the ground, lowering the humidity of the site and improve its horticultural properties

 The water collected by a subsoil drainage system has to be conveyed to a suitable outfall such as a river , lake or surface water drain and sewer.

T

HE IDEAL SITE

T

YPICAL SUBSOIL DRAINAGE DETAILS

M

ATERIALS OF SUBSOIL DRAINAGE

  Porous - absorb water through their walls and thus keep out fine particles of soil or silt Perforated – Holes in pipe of different pattern which allow water to enter into the pipe and channels to a collection points and discharged into the designated outlet.

    

S

UITABLE PIPES

Perforated clayware – BS EN 295-5 Porous concrete – BS 5911:part 114 Clayware field pipes – BS 1196 Profiled and slotted polypropylene or uPVC – BS 4962 Perforated uPVC – BS 4660

POLYETHYLENE PIPE

P

ERFORATED PIPE

Perforated pipes for footing drains & ABS pipe for downspout drains

Subsoil drainage

S

UBSOIL DRAINAGE SYSTEMS

 The layout of subsoils drains will depend on whether it is necessary to drain the whole site or if it is only the substructure of the building which needs to be protected

M

ODEL OF SUBSOIL DRAINAGE

Subsoil drainage systems and drains

  The pipes are arranged in a pattern to cover as much of the site as is necessary Water will naturally flow towards the easy passage provided by the drainage runs

H

ERRINGBONE DRAINAGE

M

OAT DRAINAGE

O

UTFALL TO STREAM OR RIVER

  The system is terminated at a suitable outfall such as a river, stream or surface water sewer In cases, permission must be obtained before discharging a subsoil system