In this blog, I will write about works we performed from start to completion of the project, Dam Spillway Structure Maintenance & Rehabilitation Work of Madhya Marsyangdi Hydropower Station.
Introduction to Project
Client: Nepal Electricity Authority, Middle Marsyangdi Hydro Power Station, Siudibar, Lamjung
Contractor: LAMA- VENUS- HIMALAYAN JOINT VENTURE, Kathmandu
Contract Identification No: MMHPS – 2076/77–CT-04
Location: Siudibar, Lamjung
Project: Dam Spillway Structure Maintenance & Rehabilitation Work
Following is the step by step working procedures of the project
Insurance of the overall project
Insurance of the overall project is done. It includes insurance of all project members, staff, workers, and costly types of machinery. Costly machinery covers Concrete Mixture, Concrete Pump, Excavator, Submersible water Pumps, Crane, Sand Blasting Machines, Bar Cutter, Bar Bender, etc.
A copy of the insurance policy is then sent to the client, Nepal Electricity Authority.
Testing of Materials
Different construction materials to be used on-site are tested for their various properties. Cement, Sand, Aggregates, Reinforcement Bars are tested in the lab to check their tensile and compressive properties. Whereas, for Epoxy Chemicals, the Factory Test Certificate is the final.
Temporary housing, offices, laboratory, storeroom, workshops, workers camp, toilets, etc., that are essentially required on-site are set up.
Delivery and Installation of Plant & Machineries
Different Construction materials like Cement, Sand, Aggregates, Admixtures, MS pipes, Epoxy Materials, and other chemicals are delivered and stored on Site.
Machinery installed at the site are;
- Concrete Mixer
- Submersible Water Pumps
- Bar Bending Machine
- Sand Blasting Machine
- Bar Cutter Machine
Access Road Construction
Pathway to get to the site for excavation is constructed.
Large submersible pumps are fitted to pour out water.
Construction Coffer Dam
Large and small coffer dams are constructed to restrict water to flow back to the spillway.
Removing Sand Deposit and Debris
Sand deposits and debris is then removed.
Pre-Construction Joint Survey
A pre-construction survey of the access road, water and sand deposit level, the existing condition of the spillway, pier, ramp, roller bucket is done.
Preconstruction survey report is then submitted to the client.
Cutting Broken Reinforcement & Demolition work
Existing worn-out reinforcement bars are cut off using gas cutter and grinder. Also, the existing concrete surface is chipped off by chipping machine until loose soft concrete is removed.
Erection of Double Scaffolding
Class B MS pipes is erected to assist in chipping, drilling, anchoring, concreting and epoxy work.
Corrosion Treatment Work
Corrosion treatment of existing reinforcement bars is done to protect rebars.
Drilling and Anchoring Work
Holes of 28 mm or 25 mm diameter and 30 mm or 40 mm depth are drilled using a drilling machine. The hole is cleaned using an air blower, and the anchor rod is anchored using an Anchor – fix.
Welding Reinforcement bars
Existing worn-out Reinforcement bars are replaced by new Reinforcement bars of required diameter.
Lapping, coupling, welding.
High Strength concrete work
Firstly the rebars are provided with sufficient cover using different size cover blocks. The concreting surface is then cleaned by an air compressor or water jet. Next, the framework is provided for casting using a tie rod or any other suitable ways. Finally, high-strength M60 grade Concrete or micro concrete is poured on the surface. The required number of cube sets is prepared as a sample of the concrete casting.
Vibrator is then properly used to eliminate air bubbles by vigorously shaking the freshly poured concrete. The framework is also frequently inspected to prevent leakage of mortar and no deflections.
The applied framework is removed after 3 to 5 days and the concrete surface is cured for 7 days.
Application of Epoxy
The epoxy application area is firstly cleansed using the sandblasting machine. The resulting surface is then coated with primer, and a high abrasion-resistant epoxy coating is applied on the surface. The thickness of the epoxy is maintained as 10 -15 mm but may vary from surface to surface.
Post-Construction Survey And Documentation Work
Finishing & Site Clearance
After concreting and epoxy coating is completed, dismantling of Scaffolding, demobilization of plant & equipment and construction materials are done.
Handover of the project
After the completion of the project, the project is handed over to the Client in a small ceremony.