by PKDN Chinthaka Somaratna

CONSTRUCTION OF LIQUID RETAINING STRUCTURES

at Rathamalna/ Moratuwa Waste Water

Treatment Plant

PROJECT DESCRIPTION

Project Name : Design and Construction of Rathamalna/Moratuwa and Jaela/Ekala Waste water disposal system

Client : National Water Supply and Drainage Board

Funding Agency: Swedish International Development Agency (SIDA)

Consultant : Sweco international Contractor : E. Phil & Sons AS. Sub Contractor : China Geo Engineering

Cooperation

RATMALANA/MORATUWA

LAYOUT OF THE RATHAMALANA/MORATUWA WWTP

PLAN VIEW OF THE TANKS

42.8m

38m 5.0m

10.8m

15.0m

14.2m

SECTION OF THE WWTP

Wall Height = 6.6m , 4.5m Base thickness = 800mm, 500mmTapered Wall Bottom thickness 800mm, Top thickness 400mm

10.8m

5.0m

38m

42.8m

3.0m

PARTIAL CONTRACTION JOINTS AT BASE

• Surface type waterstops used at the base

• 50% of the Reinforcement continued at joint

• Grove has provided 25mmx 20mm and filled with water proofing sealant.

BASE CONSTRUCTION

Sulfate resistance cement had used for the ready-mix concrete.

At the construction joints surface type waterstops used.

WALLS CONSTRUCTION

PARTIAL CONTRACTION JOINTS AT WALLS

• Flat type waterstops used at the walls

• Half the Reinforcement continued at joint

• Grove has provided and water proofing sealant on both side of the wall

• Alternative Panels were concrete to minimize the early thermal cracking

• Application of bitumen Paint for the wall section below the ground.

CURING WORKS

CONSTRUCTION JOINTS

• At the construction joints waterstops has not used.

• Surface chipped and clean properly. Before fixing the formwork and prior to concrete.

• Bonding agent has used prior to the concreting the second and third lifts

Partial Contraction joints.

Construction joints.

MAJOR ISSUES

• Surface Crakes

• Pass through cracks and leaking while testing the water tightness.

• Honey combs

• At the wall construction formwork of 2.5 m height and the formwork has failed while vibrating due to lack of ties at the beginning and later it has corrected.

HONEY COMBS

• Honeycombs only in few places were observed.

• Good workability of the concrete and good vibration make less honeycombs

• Those few honeycombs were repaired using non shrinkage grout

WATER LEAKING- PASS THROUGH CRACKS

TWO METHODS USED FOR RECTIFYING THE CRACKSRECTIFYING THE SURFACE CRACKS

Cutting the grove along the surface cark and non shrinkage grout is used on the grove for the rectifying those surface cracks.

RECTIFYING THE PASS THROUGH CRACKS

Pressure grouting has used for rectifying the pass through cracks

• While commissioning this waste water treatment plant main contractor has bankrupt in Europe and contract has terminated in 30 November 2013 with the 95% of the work has completed.

• NWS&DB faced lots of problems and with the assist of the M&E Subcontractor finally this waste water treatment plant has declared open on September 2014.

THANK YOU