GABION RETAINING WALLS

GABIONS

Introduction:

Gabions are rectangular basket fabricated from a hexagonal mesh of heavily galvanized steel wire filled with rocks and stacked at to of one another to form a gravity type wall. Gabions depends mainly on the interlocking of the Individual stones and rocks within the wire mesh for internal stability.

bjectives (why use gabions):

The main objective of providing gabions is to stabilize slope with seepage problems (less porous soil) Problems and non cohesive soil. Used also at soil water interface where the soil conditions, water velocity and expected vegetative lover are such that the soil may erode under the design flow conditions.

Vertical walls can be used in some cases but the advantage of gabions in that it is very porous than walls hence is very strong in maintaining pressure accros it.

Materials used:

(a) Galvanized steel wire mesh to preven corrosion in the wire mesh.

(b) Unweathered rocks/stones (100m to 250mm)

Size:

· For strong wall unweathered materials are used, this also prevents the breakdown of the rocks into pieces.

(d) Binding wire.

Should be made of same material as the wire mesh so as to prevent corrosion.

Tools used:

(a) Fasteners

(b) Measuring tabe

(d) Pincer

(e) Hand Compactor

Participants:

(a) Site Engineer

(b) Fore man

(d) Unskilled labours

Procedures Undertaken:

i. Preparation of foundation on which the gabions are to be placed.

(a) This includes cat and fill and grading surface irregularities loose material, vegetation and all foreign matters share removed from foundation surface area.

(b) Compaction of bedding or filler material by using hand compactor to bring the level surface ready to receive gabions.

Preparation of foundation is done to prevent settling of the gabions (lateral and vertical movement).

ii. Assembly of gabion baskets by joining the vehicle edge with fastener. Assembly gabions should conformed to the engineering specification i.e. (MXIMXIM

iii. Place the empty gabions baskets on the foundation surface and Interconnect the adjacent gabions a loud the top bottom and vertical edge using lacing wire.

iv. Fill the gabions carefully with un weathered rocks ensuring alignment avoiding bulges and providing a compact mass that minimizes voids.

v. Placing of gabion lids over the rock filling and seaweed to the sides and ends with binding wire.

vi. The next gabion basket is placed over the previous on by staggering the vertical joints between the gabions of adjacent row and layers by one half of a cell length.

COCLUSION:

Gabion walls at sloppy and seepage areas are the strongest wall that normal concrete wall and are cheap that the concrete walls.

STONE PITCHNG:

Introduction:

Stone pitching is a hard wearing stone surface using large stones, set into the slopy ground or side drains n the manner of rough labels to provide the reasonably level surface.

A surface drain system that is capable of discharging all the storm water with in the rain water attachment area.

Objectives:

The main objective of constructing stone pitched drains is to provide drainage system at the road pavement preventing water from uphill to enter the pavement. Stone pitched also protects the slope from weathering.

Material Used:-

(a) Stone that are hard, sound and free from weathering and decay.

(b) Portland cement (hardens under water).

(d) Water

Tools Used:

(a) String or rope for marking out the route.

(b) Measuring tape for dimensions

(d) Trowels.

(e) Lump hammer

(f) Wooden floats.

Participants:

(a) Site engineer

(b) Fore man

(d) Skilled labours

(e) Unskilled labours.

Procedures:

i. Marking out the route by using string where by it is tred in such a way that the width of the pitch becomes 20cm.

ii. Batching of material, this is done by considering the mortar mixing ratio.

Where by the ration used was 1:4

iii. Measured material (Sand and cement) were mixed together thoroughly until the mixture become homogeneous, then water was added and mix together to form mortal.

iv. On the biding concrete under the excavated drainage, water was applied to wet the surface and amount of mortar was spread on the surface ready to receive the stones.

v. Hard un weathered stones where laid carefully on the mortar, hammered down with a lump hammer in position to make sure they are within the string provided and obtained a bond by fitting in closely adjacent stones.

vi. The process of applying mortar and laying stone o it is repeated until we go to the height of 1m from the blinding concrete.

vii. After reading 1m height finishing is done to level the surface of the pitched stone by applying amount of mortal and wooden floats is used.

viii. Pointing was the applied to the mortar joints all stone pitched drain.