Geotechnical Engineering Vocabulary

Vocabulary flashcards on Geotechnical Engineering concepts from lecture notes.

Void Ratio (e)

The ratio of volume of voids to the volume of solids and is expressed as decimal.

Porosity (n)

The ratio of volume of voids in a soil to the total volume of soil and is expressed as percentage.

Degree of Saturation (S)

The ratio of volume of water to the volume of voids.

Air Content (ac)

The ratio of volume of air to the volume of voids.

Percentage Air Voids (na)

The ratio volume of air to the total volume.

Density (ρ)

A measure of the quantity of mass in a unit volume of material

Unit weight (γ)

Measure of the weight of the unit volume material

Water Content (w)

Ratio of mass of water to the mass of soil, sometimes called as moisture content.

Dry Unit Weight (γd)

A measure of the amount of solid particles per unit volume.

Bulk Unit Weight (γt)

A measure of the amount of solid particles plus water per unit volume.

Saturated Unit Weight (γsat)

Equal to the bulk density when the total voids is filled up with water.

Submerged Unit Weight (γsub)

The effective mass per unit volume when the soil is submerged below standing water or below ground water table.

Description of Soil

Describes the physical nature and state of the soil, arrived by visual inspection, simple test, observation of site conditions.

Soil Classification

Separation of soil into classes or groups each having similar characteristics and potentially similar behaviour.

Wet Sieving

Separating fine grains from coarse grains by washing the soil specimen on a 75 micron sieve mess.

Dry Sieve Analysis

Carried out one of the particles coarser than 75µ. Samples (with fine removed) are dried and shaken through a set of sieves of descending sizes.

Sedimentation Analysis

Terminal velocity of a spherical particle is governed by the diameter of the particle and the properties of the suspension.

Grading Characteristics

Indicates the uniformity and range in grain size distribution.

Liquid Limit (w1)

The water content corresponding to the arbitrary limit between liquid and plastic state of consistency of a soil.

Plastic Limit (wp)

The water content corresponding to an arbitrary limit between the plastic and the semi-solid states of consistency of a soil.

Shrinkage Limit (ws)

The maximum water content at which a reduction in water content will not cause a decrease in the volume of a soil mass. It is the lowest water content at which a soil can still be completely saturated.

Plasticity Index (Ip)

The range of water content over which the soil remains in the plastic state.

Liquidity Index (IL)

Used for scaling the neutral water content of a soil sample of the limits. It is a measure of soil strength

Consistency index

Indicates the consistency (firmness) of a soil. It shows water content of the soil near to its plastic limit.

Flow Index

The rate at which a soil mass loses its shear strength with increase in water content.

Toughness Index

A measure of the shear strength of a soil mass at its plastic limit.

Activity of Soils

A measure of water holding capacity of clayey soils.

Sensitivity

A parameter which indicates the weakening of a soil mass due to remoulding.

Relative Density

Indicates how a soil mass would behave under loads. It gives clear idea about the denseness of soil mass, and void ratio

Permeability of Soils

The property of soil, which allows the flow of any liquid through its pores voids. The permeable soils will allow water flow from points of high energy to points of low energy.

Darcy’s Law

There is a linear relationship between flow velocity (v) and the hydraulic gradient (i) for any given saturated soil under steady laminar flow condition.

Constant Head Flow

The total quantity of flow Q in time t can be given by Q = qt = K i At

Falling Head Flow

Total head h in a standpipe of area a is allowed to fall hydraulic gradient is varies with time.

Total Stress

When a load is applied to soil, it is carried by the water in the pores as well as the solid grains.

Pore Water Pressure

The pressure of water in the pores of the soil

Principle of Effective Stress

Effective stress is a force that keeps a collection of particles rigid.

Quick Sand Condition

An upward flow causes decrease in effective stress, by opposing force of gravity. When this cause to counteract completely the gravity force, effective stress is reduced to zero and the soil behaves like a very viscous liquid.