Birendra Kumar’s Post

Transcript

The first step in building a highway is planning. In a flat land, planning can be easy, but in a difficult terrain, actual work in planning is required. For example, this is a very hilly piece of land. To build A roll over a steep hill is very dangerous and not practical. Therefore, before construction begins, earth works need to be done. To make the road less deep. The high point of the land will be cut down and the low point will be filled up. This process is called. Up and feel, cut and feel is very important to reduce the steep angle of the road for the safety of the drivers. A steep Rd. creates more blind spots. For example, if somebody left a sofa uphill, the driver will have less time to react because he couldn't see the sofa ahead of time. When driving downhill, especially in the dark, the driver also could not see the sofa ahead of time. Use the steep angle is reduced by cut and fill. The driver's vision would go further and have more time to react to any possible danger ahead of time. The sofa is just an example, it could be anything on the road today. Designing of the curve is also important for safety. The outer edge of the curve is slightly elevated higher. When the vehicle makes a turn at the high speed, it needs a centripetal force to make a smooth turn without the outer edge being higher, a vehicle is likely to flip when turning at the high speed. This design applies to all types of high speed curves. After planning an earthwork is done, highways will be constructed with multiple layers. The reason for using multiple layer is to prevent erosion in the long term. Without multiple layers applied, when the road cracks, water comes in. Soil comes out in the long run. When losing too much soil, ropes will be broken or even collapse. That's why having multiple layers would prevent a large amount of soil from being eroded. Subgrade is compacted natural soil that acts as a foundation for the highway sub base course. This layer is typically composed of crushed rock. It enhances the bearing capacity of the subgrade and prevent soil from coming out base course. It consists of granular or bituminous material if function is to distribute the stress transmitted through the surface course. Surface course is a top layer and directly exposed to the traffic. The materials are mixture of granular and bitumen to provide a smooth surface and also can resist the abrasive forces of traffic. Even with multiple layers, erosion still happens in smaller amounts and form potholes. But at least potholes are still easier to fix compared to a collapse or totally broken Rd. Highway bridges are less likely to have potholes or being damaged over time because they are not built by rock and soil. They're built with layers of steel beam and reinforced concrete, so there's no need to worry about erosion. Hwy. bridges are built in smaller section and then assembled together in between. There is a small space in joint which allows each bridge section to expand and contract without cracking. Most matter expands when it's hot and contracts when it's cold. Using steel and reinforced concrete is applying only in some short section of the highway, such as bridges, because it costs a lot more compared to using soil and rocks. Draining system is also very important to keep water out of the road surface. Highways are never flat, they're always built in a convex shape upward to let the water flow to the side of the road. This is to prevent accidents caused by hydroplaning either city. There's more advanced training systems such as sewer. Or ditch. Thank you for watching. If you like this video, subscribe to my channel. My name Lucius, I'll see you in the next video.