Last summer I built an underground sprinkler system for my lawn. As I flipped the switch for the first time and beamed with pride at my wonderful creation, I couldn’t help but notice the loud thud whenever one of the valves closed. Lo and behold (insert joke about engineer building projects here), this is a […]

# Archives for December 2013

## Fluid Dynamics

Fluid dynamics refers to the study of fluid in motion. It includes fluid moving through pipes, measurements with venturis and orifices, and other motion-related topics such as lift and drag, and pumps. Reference The field of fluid dynamics is a subcategory of fluid mechanics. It’s sibling is fluid statics. In practice, the field of fluid […]

## Acceleration Due to Gravity

The normal values for gravitational acceleration used in physics and engineering are: g = 9.8066 m/s2 g = 32.1740 ft/s2 Poles and Equator Because g varies from the poles to the equator, here are the extreme values: North and South Poles: g = 9.832 m/s2 = 32.26 ft/s2. Equator: g = 9.780 m/s2 = 32.09 […]

## How to Calculate Relative Density

Relative Density is the ratio of the density of a substance to a specified reference density. $latex D_r = \frac{\rho_s}{\rho_{ref}}&s=2$ Where: Dr = Relative Density (dimensionless) ρs = bulk density of soil (kg/m3 or lb/ft3) ρref = bulk density of reference (kg/m3 or lb/ft3) Often, the reference density is that of water, 62.4 lbs/ft3 or […]

## How to Calculate Specific Gravity

Specific Gravity is the ratio of the density of a soil to the density of water. $latex SG = \frac{\rho_s}{\rho_w}&s=2$ Where: SG = Specific Gravity (dimensionless) ρs = bulk density of soil (kg/m3 or lb/ft3) ρw = bulk density of water (kg/m3 or lb/ft3) = 1000 kg/m3 (62.4 lb/ft3) Specific Gravity of Various Substances Substance […]

## How to Calculate Bulk Density

Bulk density, also called soil density, is the ratio of the total mass of a soil to the total volume. $latex \rho = \frac{m_t}{V_t}\newline\newline =\frac{m_w + m_s}{V_g + V_w + V_s}&s=2$ Where: ρ = bulk density (kg/m3 or lb/ft3) mt = Total mass (kg or lbs) mw = Mass of water (kg or lbs) ms […]

## How to Calculate Degree of Saturation

The degree of saturation is the ratio of the volume of water in a soil to the volume of voids. $latex S = \frac{V_w}{V_v}\times 100\%\newline\newline =\frac{V_w}{V_g + V_w}\times 100\%&s=2$ Where: S = Degree of Saturation Vw = Volume of water (m3 or ft3) Vv = Volume of voids (m3 or ft3) Vg = Volume of […]

## How to Calculate Moisture Content

The moisture content of a soil is the ratio of the mass of water in a soil to the mass of solids. $latex n = \frac{m_w}{m_s} \times 100\%&s=2$ Where: mw = Mass of water (kg or lbs) ms = Mass of solids (kg or lbs) The moisture content is thus a ratio which can be […]

## How to Calculate Soil Porosity

The soil porosity, also called the void fraction, is the ratio of the volume of voids (open spaces, i.e. air and water) in a soil to the total volume. $latex n = \frac{V_v}{V_t}\newline\newline =\frac{V_g + V_w}{V_g + V_w + V_s}&s=2$ Where: Vv = Volume of voids (m3 or ft3) Vt = Total Volume (m3 or […]

## Concrete Slump: Explanation, testing and Interpretation

Concrete slump is a definition of the consistency, often called workability, of concrete. Slump Test The slump test is defined by ASTM C143 and AASHTO T119 in the United States, and EN 12350-2 in Europe. There is no significant other testing method for concrete workability in industry use today. A standard size cone (Base diameter […]