There are couples of design of concrete drain in construction, such as berm drain, toe drain, embankment shoulder drain, cascaded drain and etc. All of them are made from concrete, the mixture of the concrete is depending on what drain to be constructed. Concrete drain can be constructed by hand, without any machine, concrete can be mixed by hand as well if the quantity used is less. Sometimes concrete drain can be spoiled or failure, concrete drain such as cascaded drain is connecting with the concrete curb, if the concrete curb doesn’t function well to control velocity of the water flow, the high speed of water flow might destroy the concrete cascaded drain, so rectification work for concrete drain has to be carried on.

How To Rectify Eroded Concrete Drain

1) The eroded concrete drain shall be excavated and form benching with a case backhoe.

2) Suitable earth shall be filled in layer and compact with a plate compactor.

How To Build Concrete Drain

1) After completion of reinstatement of the eroded concrete drain to the profile, excavation of the concrete cascading drain shall be carry out by case backhoe.

2) The bottom trench earth shall be levelled and trimmed manually by general workers for laying for 50mm thick lean concrete.

3) After the lean concrete had set, erection of formwork shall be carried out.

4) BRC reinforcement of the correct dimensions shall be installed.

5) Grade 20 concrete shall be laid and compact with poker vibrator up the drain bottom slab.

6) After the base concrete had set, concrete drain side wall reinforcement and formwork shall be installed.

7) Grade 20 concrete shall be delivered, laid and compact to specification.

8 ) Prior to all concreting works, formwork and reinforcement shall be inspected by the Engineer or his representative to ensure that the formwork and reinforcement are properly aligned and secured in place.

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In construction area, many contractors do not want to follow what the client’s need or client’s instruction. Contractors do their own way without follow the design because of saving cost, this is the most serious problem that occurred in construction line. In my case, I faced a lot of similar problems in my project which the drainage contractor doesn’t follow the design and causes the drainage systems in trouble.

What Is Drainage Systems?

Drainage system is very important for a building, industrial area, housing area, and etc. Drainage is used to guide the rain water to flow into the right place. It’s used to avoid flood happening in that area. Most probably drainage is constructed with concrete, but there is also some drainage systems that installed with pipe or we called it piping system as well.

In construction, there is a drainage called Cascaded Drain. Cascaded drain is constructed on the slope, it’s constructed like a staircase and it’s constructed in steps. It’s very commonly used in my country, it’s very useful to be constructed on the slope to avoid slope failure due to overflow of rain water.

I’ll be explaining what is concrete cascaded drain and how is it going to be look like if it’s under designed, which is happened in my project site.

Before we can construct the concrete cascaded drain on the slope, we have to do excavation work so that we can install the formwork system to pouring the concrete.

The photo above shows a workman is installing the formwork system and concrete is going to be poured after the formwork system work is done.

This is what a concrete cascaded drain supposed to be constructed and the drainage system is working well. The steps are in 90 degrees and the speed of water flow can be slowed down when the water rain comes from top to bottom.

In the above statement, that’s a proper way and proper drainage system which is constructed on my other project site. I’m going to show you a failure drainage systems that has been occurred in my current project site. The failure drainage systems is due to the cascaded drain is under designed, the drainage contractor didn’t follow the design and even my instructions. It’s lucky that I’m still able to order the drainage contractor to repair the failure drainage system.

This is the concrete cascaded drain which is under designed. As you see on the photo and compare it with the photos above, there is no 90 degrees steps like the staircase. Other than this, the height of the sides for the drainage system is not enough and it’s not following the design. With that said, when the high volume of water rain and high speed of water flow, the drainage systems doesn’t perform well to slow down the speed of flow. In this case, when the high speed of water flow, the water overflow onto the side of the cascaded drain and we called it stone pitching.

This is the incident after a few days of high speed water flowing. The stone pitching on the side of cascaded drain fall down. The drainage system is totally fail because of the design error. In this case, we have a few months period, it’s like a warranty from contractor and we called it as “Defect Liability Period“, which mean that the drainage contractor have to ensure that the drainage system is working perfectly within that period.

So, I ordered the drainage contractor to repair the failure cascaded drain. Although it’s still not looking nice but as long as it can support the slope and has the ability to slow down the water rain flow. The drainage contractor doesn’t follow my design and repair in his own way.

After repairing of the failure cascaded drain, it looks fishy but it can still performs well. That’s the under designed drainage system, it may waste a lot of time and cost to repair it.

I ordered the drainage contractor to repair the stone pitching and rise up the level to avoid overflowing of high speed water rain flow. Other than this, I ordered him to construct a 150mm height of brickwall at the bottom of guardrail to protect the stone pitching and avoid the overflowing as well.

It’s not a standard design for a concrete cascaded drainage systems. Although it works well but everything goes wrong, we will be facing problem if the government doesn’t accept the design and we have to waste time and cost to re-construct the drainage system again. In construction line, many smaller contractors are trying to save their cost and trying to construct the works in simple ways and using cheap material.

As what I discussed with MAHAGURU58 in “Precast Concrete Road Curb” article, so called ‘con’tractors are throwing their reputation, they save cost and make a good profit but they lose their reputation. Reputation in construction line is much more important than money, you lose your reputation and you’re not able to get any jobs from client in public or private project.

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