Civil Engineering/Surveying/leveling/types of leveling /Profile levelling

Summary

The script explains the process of profile leveling, a surveying technique used in engineering to determine the amount of earth to be cut or filled for leveled construction. It involves setting up a level instrument, taking readings at regular intervals along a central line, and recording these in a level notebook. The method includes marking points, taking foresights and backsights, and using either the height of instrument or rise and fall method for level reduction. The final step is plotting a profile, which graphically represents the ground points on a longitudinal section, with a larger vertical scale to highlight elevation differences.

Takeaways

• 📏 Profile leveling is a surveying technique used to determine earthwork quantities for construction projects.
• 📍 It is conducted along the central line of a track of land where linear engineering work is planned.
• 🔍 The process involves setting up a level instrument at various locations and taking readings at regular intervals.
• 📋 A benchmark is used as a reference point for taking back sights and foresights with a leveling staff.
• 📏 Turning points (TP) and salient points are marked and observed to capture changes in the gradient.
• 📊 The readings are recorded in a level notebook, detailing each observation's station and elevation.
• ✂️ The reduction of levels can be calculated using either the height of the instrument method or the rise and fall method.
• 📊 Plotting the profile leveling provides a graphical representation of the ground points on a longitudinal section.
• 📐 The vertical scale of the profile is typically larger than the horizontal scale to emphasize elevation differences.
• 📈 Segmented straight lines connecting the reduced level points represent the ground's longitudinal profile.

Q & A

What is profile leveling?

Profile leveling is a method of surveying carried out along the central line of a track of land where a linear engineering work is to be constructed. It is also known as longitudinal sectioning.

Why is profile leveling important in engineering?

Profile leveling is important as it helps determine how much earth needs to be cut or filled to make a leveled construction, which is essential for the planning and execution of linear engineering projects like roads, railways, and canals.

What are the steps involved in carrying out profile leveling?

The steps include setting up the level on a convenient location, taking a backsight on a benchmark, marking points at regular intervals, taking observations at these points using a leveling staff, repositioning the instrument, and recording the readings in a level notebook.

How are the readings from profile leveling recorded?

The readings are recorded in a level notebook with columns for backsight, intermediate sides, and foresight. The reduced levels of various stations are computed and plotted to create a profile.

What is the purpose of marking points at regular intervals during profile leveling?

Marking points at regular intervals allows for systematic data collection along the alignment, which is necessary for accurately determining the depth of cutting or filling required at each point.

What is the significance of the benchmark in profile leveling?

The benchmark serves as a reference point for the leveling process. A backsight is taken on this marked benchmark to establish a known starting elevation for the leveling work.

How are the reduced levels of various stations computed?

The reduced levels can be computed using either the height of instrument method or the rise and fall method, which involve calculations based on the readings taken at different points along the profile.

What is the purpose of plotting a profile after leveling?

Plotting a profile provides a graphical representation of the ground points on a longitudinal section, which helps visualize the elevation changes and plan the construction work more effectively.

Why is the vertical scale of a profile plot generally larger than the horizontal scale?

The vertical scale is drawn larger than the horizontal scale to accentuate the differences in elevations, making it easier to identify and plan for the necessary earthwork.

How are salient points, such as changes in slope, recorded in profile leveling?

Salient points like changes in slope are recorded by taking foresights at these points during the leveling process and noting down the readings in the level notebook.