Land Levelling Methods and Equipments

Land leveling is a crucial process in agriculture, construction, and civil engineering. The primary aim of land leveling is to create a smooth, even surface on the land, enabling proper drainage and efficient use of land for farming, construction, or other purposes.

Definition: The process of modifying the surface relief (elevation) of land by grading and smoothing to a planned grade to achieve certain specifications.

Purpose in Agriculture: Land leveling is a crucial process in agriculture that has several purposes. Here are some of the main purposes of land leveling in agriculture:

• Improving drainage: Land leveling helps to create a uniform surface that allows water to drain away from crops and prevents waterlogging, which can damage crops and reduce yields.
• Improving irrigation: A level surface allows for more efficient irrigation, ensuring that water is distributed evenly across the field and reducing water waste.
• Enhancing soil health: Leveling the land removes soil pockets and high spots, which can cause variations in soil moisture and affect crop growth. This helps to improve soil health and promotes uniform crop growth.
• Reducing soil erosion: A level surface reduces the risk of soil erosion by preventing water runoff from creating gullies and channels that can carry away soil.
• Improving crop yield: Land leveling ensures that crops are planted on a level surface, allowing for uniform crop growth and reducing crop damage from standing water, which can lead to increased crop yields.
• Terracing: It is another important technique used in agriculture that is achieved through land leveling. that helps to reduce soil erosion, increase arable land, improve water management, enhance soil fertility, and improve crop yield.
• Efficient use of resources: Land leveling enables farmers to make more efficient use of their resources, including fertilizers and irrigation water, resulting in lower input costs and higher profits.

METHODS OF LEVELLING AND GRADING

A. Based on Surveying

1. Simple Levelling

If the two points of ground surface are visible from an instrument single setting and the elevation difference is not too much, then reading is done to identify the level of the proposed point concerning planned grade land, it is called simple leveling.

2. Differential Levelling

If the two points of ground surface are too far apart or there are ground obstructions and there is a need for multiple settings of instruments to identify the level of the proposed point concerning planned grade land, it is called differential leveling.

B. Based on Common Use

1. Plane Method

This method is suitable for creating a completely level surface. The steps for this method are:

a. Determination of the centroid of the field.

• Land fields can have different shapes such as rectangular, triangular, or irregular.
• The centroid of a rectangular field is located at the point of intersection of its diagonals, whereas the intersection of the lines drawn from its corner to midpoints of the opposite sides of a triangle is the centroid of the triangular field.
• In the case of an irregular field, the area is divided into rectangles and right-angled triangles for the determination of centroid.
• The centroid is located by computing moments from two reference lines at right angles to each other.
• The distance to the centroid from any line of reference is equal to the sum of the products obtained by multiplying the area of each part times the distance from the line of reference to its centroid, divided by the total area of the field.
• By computing the distance to the centroid from two lines of reference perpendicular to each other, the exact point of the centroid can be obtained.
• The procedure to compute the centroid of a field involves summing the elevations of all stations and dividing by the total number of stations.
• The elevation of the centroid can be calculated using the formula (sum of elevations of all stations) / (total number of stations).

For Illustration: Determine the elevation of the centroid of a rectangular field when the elevations of the stations at the lines obtained from a topographic survey are provided, and stakes need to be set up for leveling work.

Stations	1	2	3	4	5
A	10.2	9.8	9.5	9.3	9.1
B	9.1	8.8	9.3	9.0	8.9
C	10.0	9.5	9.2	8.8	8.6
D	9.5	9.3	9.1	8.7	8.4

The sum of the elevations of the 20 stations is 182.4 m, and the total number of stations is 20.

Elevation of centroid =(10.2+9.8+9.5+9.3+9.1+9.1+8.8+9.3+9.0+8.9+10.0+9.5+9.2+8.8+8.6+9.5+9.3+9.1+8.7+8.4) / 20 = 9.12 m

The elevation of the centroid of the rectangular field is 9.12 m.

b. Determination of average elevation of the field by adding the elevations of all grid points and dividing by the number of grid points.

c. Computation of Formation Levels, Cuts-Fills

Any plane passing through the centroid at the average elevation will result in equal volumes of cut and fill. The elevation of each grid point is then computed based on the required longitudinal downfield grade and cross-field grade for the field. The calculation of cut and fill involves the subtraction of the point's original elevation from the formation level at the grid point.

2. Profile Method

• The method involves plotting ground profiles of grid lines and establishing a grade that balances cuts and fills while minimizing haul distances.
• It is suitable for flat land with undulating topography where a uniform surface relief is desired.
• The designer works with profiles of grid lines rather than elevations.
• Profiles are plotted in one direction with the datum line in the correct position with adjacent profiles.
• Trial grade lines are plotted on each profile based on design criteria.
• The balance between cuts and fills is estimated by comparing the areas between plotted profiles and trial grade lines.
• Several trials are usually necessary to obtain satisfactory grade lines.
• The volume of cut and fill is calculated, and the grade lines are adjusted to achieve the desired cut-fill ratio for the field.

3. Plan-Inspection Method

• The plan inspection method is a fast way to estimate the required earthwork for a land leveling project.
• This method is suitable for moderately flat land slopes.
• The technique involves overlaying a proposed ground surface map onto the original contour map.
• The plan inspection method involves contour adjustment by drawing new contour lines with uniform slope and spacing.
• Although the plan inspection method does not guarantee the minimum cuts and fills or the shortest haul length, it provides a quick estimate for the earthwork required.

4. Contour-Adjustment Method

• To maintain a balance between cut and fill, the proposed contour is kept at an average position concerning the original contour at the same elevation.
• The sum of the design cut and fills from the stake points are compared with the total and then readjusted to obtain design levels.
• The contour adjustment method is used to smoothen steep lands that are to be irrigated.
• This method requires the designer to exercise considerable judgment to minimize earthwork and haul.
• The design grade elevations are determined after a careful study of the topography.
• The method involves a trial and error approach considering downgrade and cross-slope limitations.

Equipment for Land Grading/Levelling

Equipment for land grading and field layout includes various tools and machines that are used to level the land surface and prepare it for various agricultural or construction purposes. Some of the common equipment used for land grading and field layout are:

• Surveying tools - These tools are used to determine the elevation and slope of the land surface. Surveying equipment includes Levelling machines, Total Station, etc.
• Bulldozers - These machines are used to move soil, level the ground, and remove obstacles such as rocks and trees. They are generally used for heavy-duty earth-moving tasks.
• Graders - These machines are used to level and grade the surface of the land by using a blade that can be adjusted to the desired level. Motor graders have a long blade mounted in the middle of the machine that can be adjusted to different angles to achieve desired slope and contour.
• Scrapers -A scrapper is a versatile earth-moving machine used in land-leveling operations. It is designed to cut, level, and move large quantities of earth and soil with great efficiency. Scrappers are commonly used for large-scale projects such as highway construction, mining, and agricultural land leveling. A scrapper consists of a large hopper mounted on wheels, which is pulled by a tractor or other heavy equipment. The hopper is equipped with a cutting blade that is used to scrape the topsoil and push it into the hopper. The blade can be adjusted to control the depth of the cut, allowing the operator to level the land to a desired elevation. Scrappers are highly efficient machines that can cover large areas of land quickly. They are ideal for leveling large agricultural fields, where precision is key to maximizing crop yields. With their ability to cut and move large volumes of soil, scrappers are also commonly used in mining operations to move large quantities of ore and waste material. One of the major advantages of using a scrapper for land leveling is that it requires minimal labor. The machine can be operated by a single person, who can control the blade height and hopper dump function from the cab of the tractor. This means that the operator can cover a large area of land in a relatively short period, saving both time and money. In addition to their efficiency, scrappers are also highly versatile machines that can be used for a variety of applications. They can be used to build and maintain roads, construct dams and levees, and move large quantities of material in mining operations.
• Excavators - These machines are used to dig, level, and grade the soil. They can also be used to remove debris and obstacles.
• Rollers - These machines are used to compact soil and level it to the desired grade.
• Laser-guided grading systems - These systems use lasers to guide grading machines to achieve a high level of accuracy and precision. The term "laser" is an acronym that stands for Light Amplification by Stimulated Emission of Radiations. In the field of agriculture, construction, and other related industries, the use of lasers has become increasingly popular. Specifically, in land leveling, helium-neon-type lasers that produce red light are commonly used. These lasers are mounted on different types of equipment such as bulldozers, scrapers, road graders, and terraces. Compared to traditional land leveling methods, laser-guided land leveling has numerous advantages, including time-saving, higher accuracy, less labor, cost-effectiveness, and the ability to download land elevation data onto a laptop for land leveling design. The laser-guided land leveling system comprises three main components: the laser transmitter, laser sensor, and electronic hydraulic control system.

• Laser Transmitter: The laser transmitter sends a self-leveled, 360-degree continuous laser from a tripod in the middle of the work site. The laser is projected onto the plane or slope desired for excavation.
• Laser Sensor: The laser is picked up by one or more receivers that can be hand-held, rod-mounted, or equipment-mounted.
• Electronic Hydraulic Control System: The laser receivers are connected to the equipment's hydraulics. The signals from the laser are used to control hydraulic valves, which control the desired depth of cut and track the elevation of the field. 
• The laser-guided system can be utilized for various tasks such as laying pipelines, excavating ditches and canals, and lining canals. It is particularly useful for land leveling on steep terrain that is to be irrigated, and the design grade elevations are determined through careful study of the topography.
• GPS systems - These systems are used to accurately determine the position and elevation of the land surface, which can be used to guide grading machines.
• String lines - These are used to mark out the boundaries and contours of the land surface.
• Trenchers - These machines are used to dig trenches for drainage and irrigation system.
• Tillage Equipment: Machines like Seed Drills, Cultivators, and harrows are used to plant seeds in a controlled and precise manner and to prepare the soil for planting by breaking up clumps of soil and removing weeds.

All of these tools and machines play an important role in land grading and field layout, and the specific equipment used will depend on the requirements of the project and the nature of the land being worked on.