We have studied in an earlier article, marking of side bearing type foundation. Let’s discuss the next topic.
Different types of Gravity Based Foundation
In a similar manner, one can give a marking to all such types of foundation by using the volume chart which is easily available on the internet, like for the case of side gravity (Bg-type) foundation, pure gravity (P-type) foundation, and new pure gravity (Mg-type) foundation.
You can visualize the trapezium with certain dimensions which need to be excavated.
For understanding more clearly, you can visit the nearby station where the electric locomotive is operative.
You would observe two pillars each on, one side of the platform which must be connected by the mast known as the boom in between. And on those booms, you will observe the assembly of steel tubes known as ‘Cantilever assembly‘.
Now, here we will discuss the marking of the foundation known as a portal where these pillar-like structures are erected generally known as ‘Uprights‘. (Uprights are the mast which places in the yard or station section).
Depending upon the number of tracks that these portals would cover they are divided into three types-
- N-type
- O-type
- R-type
Now for the erection, there must be some hole having some dimension where these uprights would be erected.
For creating those holes a cylindrical structure in the case of normal mast foundation and a cuboidal structure in the case of uprights is used called ‘Scroll‘.
Scroll used for the foundations dimensions are,
| Scroll | Foundation Dimension |
| N-type | 60 x 60cm |
| O-type | 70 x 70cm |
| R-type | 80 x 80cm (rarely used) |
Suppose, you need to supervise the foundation excavation of the yard. So, you must be aware of the dimension and type of portal to be excavated (dimensions can be obtained from the volume chart).
Generally, for uprights, the P-Type of the foundation is used. For instance, you can visualize a trapezium having a height of 1.60, one side of 3m, the other of 1m, and the width of 1.70m along the track. (P-10 type foundation dimension)
As the size of the N-type portal is 46x46cm, So, simply add 23 to the implantation to get the center where the scroll will be placed.
Alternatively, you can also check the center from the opposite portal if already done.
Note: In the case of the normal foundation, the height of the hole called as ‘Embedded’, the length must be1.35m. And in the case of the portal, it must be 1.45m.
I guess this gravity based foundation knowledge is sufficient for you to get the basics of railway construction (i.e. civil work) which needs to be done before planning for the electrical work.
In the upcoming article, I will explain the quality test which is to be done by the site engineer to ensure the standard.
I completed my BTech in electrical engineering in 2020, believe in the philosophy of ‘FIRST YOU LEARN THEN YOU EARN’. I am currently working as a GET in the ‘Railway Electrification’ project.