Insitu moisture content of soil at borrow area is 14% and its moist unit weight is 17KN/m³.Specific gravity of solids for soil is 2.7.The finished compacted volume is 2000m³.If the soil compacted to dru unit weight of 18KN/m³ at moisture content of 16%ii)If a dump truck can carry 150KN of soil in a trip,what will be the number of trips required to transport soil to construction site? iii)what is the amount of water in KN to be added to borrow soil to give desired compaction?

Question

Answer

Given:
- Moisture content of soil at borrow area = 14%
- Moist unit weight of soil = 17 kN/m³
- Specific gravity of solids for soil = 2.7
- Finished compacted volume = 2000 m³
- Dry unit weight of compacted soil = 18 kN/m³
- Moisture content of compacted soil = 16%
- Capacity of dump truck = 150 kN

To find:
i) Number of trips required to transport soil to the construction site
ii) Amount of water in kN to be added to borrow soil to achieve desired compaction

Solution:

1. Calculation of Dry Unit Weight:
The dry unit weight of soil can be calculated using the following formula:
Dry unit weight (γd) = Moist unit weight (γ) - (Moisture content (w) × Unit weight of water (γw))
Given:
Moist unit weight (γ) = 17 kN/m³
Moisture content (w) = 14%
Unit weight of water (γw) = 9.81 kN/m³ (approximate value)

Substituting the values:
γd = 17 - (0.14 × 9.81) = 17 - 1.3734 = 15.6266 kN/m³ (approximate value)

2. Calculation of Water Content:
To calculate the water content, we need to find the weight of water present in the soil. The weight of water can be calculated using the following formula:
Weight of water = (Moisture content (w) × Dry unit weight (γd) × Volume)

Given:
Moisture content (w) = 16%
Dry unit weight (γd) = 18 kN/m³
Volume = 2000 m³

Substituting the values:
Weight of water = (0.16 × 18 × 2000) = 5760 kN

3. Calculation of Amount of Water to be Added:
To achieve the desired compaction, we need to add water to the borrow soil. The amount of water to be added can be calculated using the following formula:
Amount of water to be added = Weight of water required - Weight of water present

Given:
Weight of water required = 0 (since the desired moisture content is already given)
Weight of water present = (Moisture content (w) × Dry unit weight (γd) × Volume)

Substituting the values:
Weight of water present = (0.14 × 15.6266 × 2000) = 4393.84 kN

Amount of water to be added = 0 - 4393.84 = -4393.84 kN

4. Calculation of Number of Trips:
To calculate the number of trips required to transport the soil, we need to divide the total weight of soil by the capacity of the dump truck.
Total weight of soil = Dry unit weight (γd) × Volume
Number of trips = Total weight of soil / Capacity of dump truck

Given:
Dry unit weight (γd) = 18 kN/m³
Volume = 2000 m³
Capacity of dump truck = 150 kN

Sub

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