What is meant by measuring site work?

Bid drawings typically include very little material about the precise requirements of site work operations, measuring site work and excavation work differs from measuring most other works on a construction project. The actual site work conditions are not provided and also the dimensions of the excavations are not known during the pre-construction phase. The precise measurement of the excavation and backfill of the earth material and topsoil is important for a contractor to decide upon the total cost required for the process. All the works should be carried out under OSHA (Occupational Safety and Health Administration) standards to ensure the safety of the workers.

Sitework and Excavation

The topsoil or excavated soil is usually measured in terms of cubic yards or cubic meters. The quantity of the fill material of the backfill is also calculated in terms of cubic yards or cubic meters. During excavation, no allowance is made for swell factors and compaction factors for the excavated soil. The excavations made at the construction site are made using excavators and are classified under categories such as site and topsoil clearing, excavation over the site to reduce levels, basement excavations, trench excavations, and pit excavations. If the materials to be excavated are of different types, each material is measured separately. The fill and backfill materials are then measured and classified as fill over the site to raise levels, backfill to basements, backfill to trenches, backfill to the pits, and gravel under slabs on grade.

When excess excavated material needs to be removed from the site, the surplus soil disposal item must be quantified. The quantity of this item may be estimated once all of the excavation and backfill items have been measured. At this stage, the overall volumes of excavated soil and common backfill define the quantity of material left over from operations.

Measurement of earthwork excavation and backfill

Cross-section method

Cross-sections of the current and proposed levels are plotted at regular intervals (station spacing) over the graph sheet representing the surface of the project site after taking the survey for elevations using the cross-section method. The cut area and fill area for each cross-section are calculated. Using the station spacing and cut area, the cut volume is obtained and using fill area and station spacing, the fill volume is obtained.

The following formula is used for calculating the cut and fill depth,

$$\begin{gathered} Volume = Station spacing\times \left(Area 1+Area N+\frac{Sum of other areas}{2}\right) \\ where \\ N=Number of stations \\ Area N=Area at the last station \end{gathered}$$

Another option is to create the sections in computer-aided design and drafting (CADD) and export the areas or to use the trapezoidal rule to calculate the areas analytically.

Grid method

The grid technique involves drawing a uniform grid onto a plan of the earthworks project and subtracting the current and proposed ground levels at each grid node. These parameters are used to calculate the average cut or fill depth necessary for each grid cell, and the volume for each cell is calculated by multiplying the depth by the cell area. By adding the volumes of each cell, the overall cut and fill volumes for the project may be estimated in cubic yards or cubic meters. Subtracting the average existing level of the cell from the average proposed level yields the cut or fill depth for each cell. If the resultant depth is positive, it is a filled cell and it is a cut cell if the resultant depth is negative. The volume is computed in cubic yards by multiplying the cut or fill depth by the grid-cell area in both cases.

For example, consider the following arrangement of grids of size 10' x 10' each for an area to be excavated.

Each grid intersection is divided into 4 parts, namely the new grade elevation, existing grade elevation, depth of cut, and depth of fill. The elevation details are obtained by surveying. Then these details are tabulated.

The frequency of the grid refers to the number of quarters of a particular station point in each grid. For example, for station point 3B, the frequency will be 4 as the station point applies to all the 4 adjacent quarters of the area. The total volume of cut depth is obtained by adding all the individual volumes of cut for each station point, the same is followed for fill volume. Then the volume is converted to cubic yards.

Contour area method

The contour area method uses the contour elevation lines printed on the topographic map and the grade lines drawn on the proposed site plan to calculate the site's cut and fill volumes. It is the product of the average area of nearby contour heights and the average elevation difference. The volume is computed in cubic feet and is converted to cubic yards.

The volume is computed using the following formula,

$$\begin{gathered} V=H\times \left[\frac{\left(A_1+A_2\right)}{2}\times \frac{1}{27}\right] \\ where, \\ V=Volume \\ A= Areas of the adjacent elevation contours in feet \\ H=Elevation difference between contours in feet \end{gathered}$$

The other methods used to obtain cut and fill volumes are the triangular area method, length interval method, depth area method, end area method, prismoidal formula method, triangulated irregular network, and digital terrain model methods.

Piling

Piling work is often subcontracted to any other contractor who has more experience in handling piling equipment and piling techniques than the main contractor. The piling work consists of the layout of piles, cutting off the top of piles, and removing excavated materials produced as a result of piling operations.

First, the length of the piles from the bottom end to the cutoff level of the pile is measured. The piles are then classified according to the materials used, cross-section, and length. The total cost of piling includes transporting, handling, and driving the piles. The piles are further characterized by their use on the project site, such as piles not fully embedded, piles driven in water, or piles driven under any other special circumstances. There are different types of piles based on materials such as timber piles, steel piles, steel sheet piles, concrete piles, and any other special type of piles.

If the piles are to be extracted, each type of pile is measured separately based on linear measurement for bearing piles and area measurement for sheet piles.

Context and Applications

This topic has scope in the following fields of study:

• Bachelor of Technology in Civil Engineering
• Master of Technology in Civil Engineering
• Bachelor of Technology in Geotechnical Engineering
• Master of Technology in Geotechnical Engineering

Practice Problems

Q 1. What is the increase in the volume of the undisturbed stage to an excavated stage called?
a. Swell Factors
b. Compaction
c. Deposit
d. Layer

Answer: Option a
Explanation: The ratio of the weight of undisturbed soil to the weight of an excavated soil is known as swell factors.

Q 2. What does OSHA stand for?
a. Organic Safety and Health Association
b. Occupational Safety and Healing Administration
c. Occupational Safety and Health Administration
d. Occupational Safety and Health Association

Answer: Option c
Explanation: The Occupational Safety and Health Administration, or OSHA is in charge of protecting workers' health and safety in the United States.

Q 3. What is the oldest equipment or truck used for doing earthwork called?
a. Shovel
b. Excavator
c. Tractor
d. None of the above

Answer: Option b
Explanation: Excavators are heavy construction equipment consisting of a boom, dipper (or stick), bucket, and cab on a rotating platform used to perform the work of moving the earth or topsoil and trench excavation. Diggers, motorized shovels, and 360-degree excavators are all terms used to represent excavators.

Q 4. What is the process of driving a pile vertically into the underground called?
a. Piling
b. Trench excavation
c. Compaction
d. Excavation

Answer: Option a
Explanation: The piles are driven into the subsurface using piling equipment. It is known as piling.

Q 5. What is the act of temporarily supporting a trench to prevent caving in the soil during earthwork excavation while site work called?
a. Drilling
b. Shoring
c. Trench excavation
d. Bracing

Answer: Option b
Explanation: Shoring is a technique in which a prop or temporary support is used during the repair or original construction of buildings and in excavations.