SOILS

Question 1

What is a Site Plan?

Answer 1

A site plan is typically a large scale drawing that shows the full extent of the site for an existing or proposed development. Site plans, along with location plans, may be necessary for planning applications. In most cases, site plans will be drawn up following a series of desk-based studies and site investigations.

Question 2

What is a Site?

Answer 2

An area of ground on which a town, building, or monument is constructed.

Question 3

What is a Site Investigation?

Answer 3

The objective of a site investigation is to gather the information needed to carry out the risk assessment, in order to be in a position to assess the presence and significance of contamination of land.

Question 4

Why is a Site Investigation important?

Answer 4

▪ Leads to an incomplete engineering design
▪ Subsequently leads to a wrongly estimated project
cost
▪ Which leads to an insufficiently prepared Bill of
Quantities or Schedule of Rates
▪ Later leads to an inadequate method statement
▪ Consequently, leads to a delayed completion date
▪ Which leads to subsequent claims and prolongation
cost
▪ Eventually results a higher completion cost than the
budget.

Question 5

What is a Desk Study?

Answer 5

A Desk Study which takes into account existing information about the site.

This information will come from a variety of sources and will include such diverse matters as the history of the site, its topography, geology, vegetation etc.

Question 6

What is a Walkover Study?

Answer 6

A Walk-over Survey which is a direct inspection of the site.

Usually giving the engineer/designer the opportunity to identify the nature of the ground and the nature of any hazardous features.

Question 7

What is a physical exploration?

Answer 7

A physical exploration and inspection, of the ground by means of boreholes or trial pits.

This third stage is sometimes called the Ground Investigation.

Question 8

What does the NHBC require for all sites?

Answer 8

NHBC requires all sites to be assessed by a Desk study and a Walkover survey.

The Results should be used to determine whether or not hazards are known or suspected.

Question 9

What is a Basic Investigation?

Answer 9

Basic investigation Where hazards are not suspected a basic investigation will be required to support the results of the initial assessment.

Question 10

What is a Detailed Survey?

Answer 10

Detailed investigation Where hazards are known or suspected a detailed investigation will be required.

Question 11

What is the scientific term for Soil?

Answer 11

The term ‘soil’ refers to ‘The upper layer of the earth’s crust, in which plants grow. It consists of weathered rock, organic matter, air spaces and water.

Question 12

What are the basic types of soils?

Answer 12

Very coarse, coarse soils, sands, fine soils, clays, organic soils.

Question 13

What are the advanced types of soils?

Answer 13

Calcareous soil, Plastic soil, Non-plastic soil, Subsoil, Topsoil, Superficial deposit, Sediments, Till and Engineered soil.

Question 14

What is a Boulder soil type in construction?

Answer 14

Particle sizes: Anything above 200 mm.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.
Compactness: Loose.

Strength field test: By inspection of voids and particle packing.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 15

What is the Cobbles?

Answer 15

Particle sizes: 60-200 mm.

Particle shape: Angular, sub-angular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.
Compactness: Dense.

Strength field test: By inspection of voids and particle packing.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 16

What is Coarse Gravel?

Answer 16

Particle sizes: 20-60 mm. Easily visible to the naked eye meaning that grading can be described. Well graded means there is a wide range of grain sizes; poorly graded means there is a limited range.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.

Composite soil types: Clay or silt content of under 5%.
Classified as ‘slightly clayey’ or ‘slightly silty’.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 17

What is Medium Gravel?

Answer 17

Particle sizes: 6-20 mm. Easily visible to the naked eye meaning that grading can be described. Well graded means there is a wide range of grain sizes; poorly graded means there is a limited range.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.

Composite soil types: Clay or silt content of 5-15%. Classified as ‘clayey’ or ‘silty’.

Compactness: Loose.

Strength field test: Can be excavated with a spade; 50 mm wooden peg can be easily driven.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 18

What is fine gravel?

Answer 18

Particle sizes: 2-6 mm. Easily visible to the naked eye meaning that grading can be described. Well graded means there is a wide range of grain sizes; poorly graded means there is a limited range.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.

Composite soil types: Clay or silt content of 15-35%. Classified as ‘very clayey’ or ‘very silty’.

Compactness: Dense.

Strength field test: Excavation requires a pick; 50 mm wooden peg is difficult to drive.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 19

What is coarse sand?

Answer 19

Particle sizes: 0.6-2 mm. Visible to the naked eye. When dry there is little to no cohesion. Grading can be described.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.
Composite soil types: Classified as ‘sandy gravel’ or ‘gravelly sand’. Clayey composites are described as plastic or cohesive. Silty composites are described as non-plastic or of low plasticity.

Compactness: Slightly cemented.

Strength field test: Visual examination; pick removes soil in lumps.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 20

What is medium sand?

Answer 20

Particle sizes: 0.2-0.6 mm. Visible to the naked eye. When dry there is little to no cohesion. Grading can be described.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.

Composite soil types: Classified as ‘sandy gravel’ or ‘gravelly sand’. Clayey composites are described a plastic or cohesive. Silty composites are described as non-plastic or of low plasticity.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 21

What is fine sand?

Answer 21

Particle sizes: 0.06-0.2 mm. Visible to the naked eye. When dry there is little to no cohesion. Grading can be described.

Particle shape: Angular, subangular, rounded, flat, elongated.

Texture: Rough, smooth, or polished.

Composite soil types: Classified as ‘sandy gravel’ or ‘gravelly sand’. Clayey composites are described a plastic or cohesive. Silty composites are described as non-plastic or of low plasticity.

Structure: Homogenous, inter-stratified, heterogeneous, or weathered.

Question 22

What is coarse silt?

Answer 22

Particle sizes: 0.02-0.06 mm. Barely visible to the naked eye.

Particle nature: Non-plastic or of low plasticity.

Compactness: Soft or loose.

Strength field test: Easily moulded or powdered between fingers.

Structure: Fissured, intact, homogeneous, inter-stratified, or weathered.

Question 23

What is medium silts?

Answer 23

Particle sizes: 0.006-0.02 mm. Not visible to the naked eye.

Particle nature: Non-plastic or of low plasticity.

Compactness: Firm or dense.

Strength field test: Can be moulded or powdered between fingers with strong pressure.

Structure: Fissured, intact, homogeneous, inter-stratified, or weathered.

Question 24

What is fine silts?

Answer 24

Particle sizes: 0.002-0.006 mm. Not visible to the naked eye.

Particle nature: Non-plastic or of low plasticity.

Composite soil types: Sand or gravel content of 35-65%. Classified as ‘sandy’ or ‘gravelly’.

Compactness: Very soft.

Strength field test: Exudes between fingers when squeezed in hand.

Structure: Fissured, intact, homogeneous, inter-stratified, or weathered.

Question 25

What is Clay?

Answer 25

Dry lumps can be broken but not powdered between fingers; smooth to the touch; shrinks on drying which usually leaves cracks.

Particle nature: Intermediate plasticity through to high plasticity.

Composite soil types: Sand or gravel content of less than 35%.

Compactness: Soft.

Strength field test: Soft (moulded by light finger pressure), firm (moulded by strong finger pressure), stiff (can be indented by thumb), very stiff (can be indented by thumb nail).

Structure: Fissured, intact, homogeneous, inter-stratified, or weathered.

Question 26

What is organic clay silts or sand?

Answer 26

Particle sizes: Varies.

Visual identification: Contains substantial amounts of organic vegetable matter.

Composite soil types: Sand or gravel content of 35-65%. Classified as ‘sandy’ or ‘gravelly’.

Compactness: Firm.

Strength field test: Fibres already compressed together.

Structure: Fibrous (plant remains recognisable and retains some strength); amorphous (recognisable plant absent).

Question 27

What are peats?

Answer 27

Particle sizes: Varies.

Visual identification: Predominantly plant material which remains dark brown or black, usually with a distinctive smell and low-bulk density.

Compactness: Spongy, plastic.

Strength field test: Very compressible and open structure; can be moulded by hand.

Structure: Fibrous (plant remains recognisable and retains some strength); amorphous (recognisable plant absent).

Question 28

What Alluvial deposits?

Answer 28

Natural materials deposited within and adjacent to rivers.

Question 29

What is Calcareous Soil?

Answer 29

Calcareous soil is soil which contains accumulations of calcium and magnesium carbonate, formed by the weathering of calcareous rocks and fossil shell beds.

Question 30

What is Plastic Soil?

Answer 30

Plastic soil is soil with a relatively high proportion of silt and clay that, within a certain moisture content range, is capable of being moulded or deformed without rupture.

Question 31

What is Non-Plastic Soil?

Answer 31

A non-plastic soil is a soil with coarse textures which do not exhibit plasticity at any moisture content. For more information see: Non-plastic soil.

Question 32

What is Sub-Soil?

Answer 32

Weathered soil layer extending between the natural topsoil and the unweathered basal layer (geological parent material) below, or similar material on which topsoil can be spread.

Subsoil has lower organic matter and plant nutrient content than topsoil. In most cases topsoils require a subsoil to perform one or a number of natural soil functions.

Question 33

What is Topsoil?

Answer 33

The upper layer of a soil profile, usually darker in colour (because of its higher organic matter content) and more fertile than subsoil, and which is a product of natural biological and environmental processes.

Question 34

What is Superficial Deposit?

Answer 34

A geological deposit that was laid down during the Quaternary period.

Such deposits were largely formed by river and glacial processes but can also include wind-blown deposits known as loess.

Question 35

What is Sediment?

Answer 35

The layers of particles that cover the bottom of water bodies such as lakes, ponds, rivers and reservoirs. Ref The SuDS Manual (C753), published by CIRIA in 2015.

Question 36

What is Till?

Answer 36

An unsorted glacial sediment deposited directly by a glacier.

Question 37

What is Engineered soil?

Answer 37

An artificial substrate of soil with crushed stone, sands and other materials.