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Site Investigation and Geomorphology > BS5930:2015 > Flashcards

BS5930:2015 Flashcards

Lectures 1-3

1
Q

Why is the ground important?

A

Fundamental but least understood part of an engineering structure

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2
Q

What do you need to know about the ground?

A
  1. Material in-situ
  2. Processes of formation, alteration
  3. Physical, chemical, engineering Properties
  4. Inputs for design and construction
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3
Q

What is logging?

A

Producing a description of the ground as it is in-situ

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4
Q

What is the significance of the ground’s geological history?

A

Resulting geological features cannot be removed; must be discovered and “engineered”

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5
Q

Who is William Smith?

A

Created first geological map of England, Wales, and Scotland by identifying variation/ageing of rocks encountered during construction of canals

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6
Q

What is Solid geology?

A

deep deposits of rock and engineering soil

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7
Q

What is Drift?

A

Recent superficial deposits of engineering soil (including glacial, alluvial soil) deposited over solid deposits <100,000 years ago

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8
Q

What are examples of Quaternary (~2.6 MYO) geology/glaciation processes?

A
  1. Large loading/unloading due to weight of glaciers
  2. Neotectonics (deposition of rock due to glacial movement/advancing/receeding)
  3. Erosion (forming V-shaped valleys)
  4. Overdeepened/Buried valleys (U-shaped valleys due to burial of erosional deposits from valley slopes)
  5. Paleo-slope instability
  6. Frozen ground conditions
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9
Q

Where do you get info that is Logged?

A

Exposures
Cores
Bulk Samples
Boreholes

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10
Q

What is logged in an exposure?

A

Plan, profile map, description, sketch, photo

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11
Q

What is logged in a core?

A

Core log, photo

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12
Q

What is logged in a sample?

A

Description, sketch, photo

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13
Q

What standard is used for Logging?

A

BS5930:2015 or Eurocode 7

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14
Q

What are the differences between BS5930:2015 and EC7?

A

None. EC7 is normative as of March 2015.

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15
Q

What is a Desk Study?

A

Cheap, quick method of getting background information on materials and places to make decisions about the subsequent ground investigation.
Enables the creation of a preliminary/conceptual ground model using books, maps, mining records, air photographs, newspapers, etc.

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16
Q

What is a Conceptual Ground model?

A

Preliminary ground model from desk study

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17
Q

What is the difference between soils and rocks?

A

Their genesis/origin/evolution

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18
Q

What is stronger, rocks or soils?

A

Rocks are stronger due to grain bonding, cementation during deposition (compaction/diagenesis/lithification), increasing cohesion, tensile strength, frictional strength

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19
Q

What are the types of rock based on Origin?

A
  1. Igneous (Extrusive, intrusive)
  2. Sedimentary
  3. Metamorphic
20
Q

What are the types of soil based on origin?

A
  1. Residual

2. Transported

21
Q

According to BS5930:2015, what is the difference between soil and rock?

A

Soil: Su < 300 KPa
Rock: UCS > 0.6 MPa

22
Q

What is the aim of ground investigation (Phase 2)?

A

To confirm or amend the ground model

23
Q

Give examples of tools/methods for ground investigation (e.g. drilling, sampling)

A 
Trial pitting
Augering
Window sampling
Cable percussive drilling with U100 sampler
Rotary core drilling (hollow stem auger)
Sonic drilling
CPT
24
Q

What are the sampling categories and quality classes?

A

A (high quality) to C (Low quality)

1 (best) to 5 (worst)

25
Q

What section of BS5930:2015 gives guidelines for Descriptions of soils and rocks?

A

Section 6

26
Q

What are the 3 characteristics that must be described in rock?

A
  1. Material characteristics
  2. Discontinuity characteristics
  3. Mass characteristics (Material + discontinuities)
27
Q

What are some things that must be included in a Core Log?

A 
GW strike
Gas emissions
Blowing/sucking holes
Type of flushing medium
Casing size/depth, type
Cutting bits/shoes used
Drilling fluid returns
Rate of penetration
Depth of in-situ tests
Sample depths
28
Q

What evidence is used from the core log? (4)

A
  1. Quantity of intact and non-intact core
  2. Type of material in core box
  3. Condition of recovered core (may differ from actual/in-situ mass)
  4. Drilling records from driller
29
Q

What is Core quantity?

A

Percentage of core recovered (can vary depending on geology, type of drilling)

30
Q

What can cause a gap/core loss?

A

Voids, drilling errors, compaction, karstic environments, settlement, realignment of fractures, etc.

31
Q

What can cause core gains?

A

Material falling in (unlikely due to flush), realignment of fractures, swelling

32
Q

What are Material characteristics?

A 
Strength
Inherent structure
Colour
Texture/fabric
Grain/crystal/particle size
Rock name
Minor constituents
33
Q

What is the difference between BS5930:2015 and BS5930:1999?

A

BS5930:1999 does not consider engineering soils (rocks with strengths <0.6 MPa are still considered as rock) and has classifications of Moderately Strong and Moderately Weak.
BS5930:2015 separates rock and soil (<0.6 Mpa) and has Medium strong and Extremely Weak categories.

34
Q

How is weathering described?

A

Must describe the degree, extent, and nature of weathering e.g. colour change, reduction in strength, products, fracture states, etc.

35
Q

What are Discontinuity characteristics?

A

Type, Inclination/dip, Orientation, Roughness, Aperture, Infill, Surface condition, Colour

36
Q

What is a Joint?

A

Discontinuity with no visible displacement

37
Q

What is a Fault?

A

Discontinuity with recognisable displacement (slickenside, smearing)

38
Q

What is a Bedding opening?

A

Separation on bedding

39
Q

What is a Cleavage fracture?

A

Fracture along cleavage

40
Q

What is an Induced fracture

A

Discontinuity of non-geological origin e.g. due to drilling, blasting, etc.

41
Q

What is an Incipient fracture?

A

Fracture with some tensile strength (not fully developed/possibly cemented)

42
Q

What is Total Core Recovery?

A

% of core recovered (intact and non intact) in a core run vs. length of core run

43
Q

What is Solid Core Recovery?

A

% of core recovered with at least 1 full diameter

44
Q

What is Rock Quality Designation?

A

Ratio of total length of pieces of solid core >100 mm long to the length of core run

45
Q

What is Fracture Index/Spacing?

A

of fractures or spacing of fractures over an arbitrary length

46
Q

What can be logged/recorded from an exposure and not a core?

A

Fracture orientation, roughness, aperture, persistence, termination, seepage/GWT conditions

47
Q

How is Chalk described in field logging using CIRIA 574?

A

By aperture, spacing of fractures and dry density of mass
Grade A (closed aperture) to D (structureless; Dc clast dominated or Dm matrix dominated)
Suffix 1 (>600mm spacing) to 5 (<20 mm spacing)
Best is A1 chalk

Site Investigation and Geomorphology (1 decks)

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