Types of Levelling and Application to Chain & Levelling Instruments in Building Construction
Levelling is a fundamental process in surveying used to determine the elevation of different points on the ground. It plays a vital role in building construction by ensuring proper alignment, drainage, and structural stability. In ITI Draughtsman Civil, understanding the types of levelling and their application using chain and levelling instruments is essential for practical fieldwork.
1. Types of Levelling
Levelling is classified into different types based on its purpose and method:
(a) Simple Levelling
- Used to find the difference in elevation between two points.
- Suitable for short distances.
(b) Differential Levelling
- Used when points are far apart or separated by obstacles.
- Involves multiple instrument setups.
(c) Fly Levelling
- Used to transfer benchmark from one location to another.
- Quick method without detailed observations.
(d) Profile (Longitudinal) Levelling
- Used for preparing longitudinal sections.
- Applied in roads, railways, and canals.
(e) Cross Section Levelling
- Used to determine levels across a line.
- Helpful in earthwork calculations.
(f) Reciprocal Levelling
- Used when there are obstacles like rivers.
- Helps eliminate errors due to curvature and refraction.
2. Application of Chain in Levelling
Although levelling mainly deals with vertical measurements, chaining is also used to measure horizontal distances between points.
- Used to measure distance between survey stations.
- Helps in locating points for levelling observations.
- Used in profile and cross-section levelling.
- Assists in preparing accurate site layouts.
3. Application of Levelling Instruments in Building Construction
Levelling instruments such as auto level, dumpy level, and tilting level are widely used in building construction for various purposes:
(a) Site Preparation
- Determining ground levels before construction.
- Ensuring proper site grading and drainage.
(b) Foundation Work
- Checking excavation depth.
- Maintaining uniform foundation level.
(c) Structural Alignment
- Ensuring horizontal alignment of floors and slabs.
- Maintaining correct level of beams and columns.
(d) Road and Pavement Construction
- Setting gradients and slopes.
- Ensuring proper drainage.
(e) Drainage and Sewer Systems
- Maintaining proper slope for flow of water.
- Avoiding water stagnation.
4. Importance in Building Construction
- Ensures accuracy in construction work.
- Prevents structural defects.
- Helps in proper drainage and water flow.
- Improves durability and safety of structures.
5. Precautions
- Ensure proper leveling of the instrument.
- Keep staff vertical during readings.
- Check measurements regularly.
- Maintain instruments properly.
Role of Draughtsman Civil
A Draughtsman Civil uses levelling data and chain measurements to prepare plans, sections, and layouts. Proper understanding helps in accurate design and execution of construction projects.
Conclusion
Levelling is an essential surveying process with various types used for different purposes. The use of chain and levelling instruments plays a significant role in building construction.
For ITI Draughtsman Civil students, understanding these concepts is crucial for accurate surveying, planning, and successful construction work.