The method for calculating the volume of a rubble stone foundation, sourced from river stones, differs slightly from other building materials due to the irregular shapes of the stones.
To estimate the quantity needed, it is important to know the formula calculation in rubble stone required for foundations.
Knowing the estimated amount of rubble stones needed for the foundation helps you calculate the material requirements for the construction – and thus, make an estimation for your budget.
If you’re not yet familiar with how to calculate the volume of a rubble stone foundation, read this article for insight.
How to Calculate the Volume of a River Stone Foundation
Source: Perkim
A foundation is one of the most important parts of construction as it can affect the strength of the building. Low-strength foundation might cause the building to sink or collapse. For this reason, foundations typically use strong materials, one of which is rubble stones.
Rubble stones are often used as foundation material because they are highly durable. As mentioned earlier, the method for calculating the volume of a rubble stone foundation is slightly different from other building materials as they have irregular shapes.
Therefore, you need to know the right formula to determine the right amount of rubble stones needed for the building’s foundation.
Before calculating the volume of the rubble stone foundation, you must first calculate the volume of the foundation itself with the following formula.
Foundation Volume = Cross-Sectional Area x Foundation Length
It’s important to note that the formula for the cross-sectional area of the foundation depends on the shape of the cross-section. Generally, the cross-section of a foundation is trapezoidal, so the formula for its area is the same as that for a trapezoid:
Cross-Sectional Area = ½ x (Length of Top Side + Length of Bottom Side) x Foundation Height
After determining the foundation's volume, you can proceed to calculate the volume of the rubble stone foundation with the following formula:
Rubble Stone Foundation Volume = Cross-Sectional Volume x Rubble Stone Coefficient
It should be noted that the river stone coefficient varies depending on the type and density of the stones.
However, the coefficient commonly used in calculations is 1.2. That way, you can determine the amount of rubble stones required by calculating the volume of the river stone foundation.
Simulation of Rubble Stone Foundation Calculation
As mentioned earlier, there are two steps to calculating the volume of a rubble stone foundation. First, calculate the foundation volume, then calculate the river stone foundation volume in the next step.
If you’re still confused by the formulas above, follow the simulation below to get a better understanding.
Suppose a foundation has a trapezoidal cross-section with a top side length of 30 cm and a bottom side length of 40 cm.
The foundation will be 20 meters long with a height of 60 cm. Below is the calculation for the rubble stone foundation volume using a river stone coefficient of 1.2.
Top side length = 30 cm = 0.3 m
Bottom side length = 40 cm = 0.4 m
Foundation height = 60 cm = 0.6 m
- Cross-Sectional Area = ½ x (Top Side Length x Bottom Side Length) x Foundation Height
Cross-Sectional Area = ½ x (0.3 m + 0.4 m) x 0.6 m
Cross-Sectional Area = 0.21 m²
- Foundation Volume = Cross-Sectional Area x Foundation Length
Foundation Volume = 0.21 m² x 20 m
Foundation Volume = 4.2 m³
- River Stone Foundation Volume = Foundation Volume x River Stone Coefficient
River Stone Foundation Volume = 4.2 m³ x 1.2
River Stone Foundation Volume = 5.04 m³
So, you would need a river stone foundation volume of 5.04 m³ to create a foundation with a volume of 4.2 m³.
Advantages of Rubble Stones for Foundations
After learning how to calculate the volume of a rubble stone foundation and its simulation above, you should know some of the advantages of rubble stones. Knowing these advantages helps you decide whether this material is suitable for your needs. Some of the advantages of river stone are as follows:
- High durability: Rubble stone has strong durability which supports structural loads well.
- High stability: Rubble stone can prevent shifting and cracking in the soil around the building.
- Weather resistance: River stone is resistant to high temperatures and humidity, making it less prone to damage.
Disadvantages of Rubble Stone for Foundations
In addition to the advantages mentioned above, rubble stones also have some drawbacks you should consider. Here are the disadvantages of rubble stones for foundations that you need to know:
- Limited load-bearing capacity: River stone has a limited load-bearing capacity, unlike modern foundation materials like reinforced concrete. Therefore, river stone is not suitable for high-rise buildings with very heavy loads.
- Time-consuming: The irregular shape of river stones makes the foundation construction process take longer, as more time is needed to arrange the stones to match the foundation design.
- Requires skilled labor: Building a foundation with river stones requires skilled labor because the stones' irregular shapes make the installation process more challenging.
Based on the advantages and disadvantages above, it can be concluded that rubble stone is suitable for small building foundations, such as minimalist houses or other non-high-rise buildings.
If you plan to build a large or multi-story structure, it is recommended to use other materials, such as reinforced concrete, for the foundation.
Additionally, you should hire experienced workers to construct the rubble stone foundation, as not all workers can arrange the irregularly shaped river stones into a solid foundation.
That’s the information on how to calculate the volume of a rubble stone foundation that you need to know.
Besides river stone, there are many other building materials commonly used, one of which is concrete. It is a practical material as you can use ready-to-use concrete or often called precast concrete.
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