Method for the quantitative description of discontinuities in the rock mass, Part 9: Number of sets

IS 11315 Part 9 – Scope & Key Specifications

Scope Overview:

• Describes classification of joint sets in rock mass along tunnels or excavations.
• Joint sets are categorized by their number and randomness:

• Major discontinuities should be recorded individually.

Units & Symbols (SI Units):

Important Notes:

• Visual identification of joint sets should include a numbering system (e.g., "set No. 1") based on persistence or stability importance.
• Results should be rounded off as per IS 2-1960.

graph TD
    A[Rock Mass] --> B{Joint Sets}
    B --> I[Massive, Random]
    B --> II[1 Joint Set]
    B --> III[1 Joint Set + Random]
    B --> IV[2 Joint Sets]
    B --> V[2 Joint Sets + Random]
    B --> VI[3 Joint Sets]
    B --> VII[3 Joint Sets + Random]
    B --> VIII[4+ Joint Sets]
    B --> IX[Crushed Rock]

This classification aids in rock stability assessment and engineering design.

IS 11315 Part 9 - Key References, Units & Joint Sets Classification

1. Joint Sets Classification (Clause 5.2)

• Major discontinuities should be recorded individually.
• Visual recognition should include systematic numbering (Clause 4.4).

2. SI Units & Derived Units (International System)

3. Reporting & Rounding (Clause 0.6)

• Final values

IS 11315 Part 9 – Terminology & Definitions: Key Points

• Reference Standard: Definitions follow IS 11358-1986 (Clause 2.1).

• Number of Joint Sets (Clause 5.2):
  Describes rock mass jointing as:

  Code	Description
  I	Massive, occasional random joints
  II	One joint set
  III	One joint set plus random
  IV	Two joint sets
  V	Two joint sets plus random
  VI	Three joint sets
  VII	Three joint sets plus random
  VIII	Four or more joint sets
  IX	Crushed rock, earth-like

• SI Units (International System) Relevant to Rock Mechanics:

  Quantity	Unit	Symbol	Definition
  Length	metre	m
  Mass	kilogram	kg
  Time	second	s
  Force	newton	N	1 N = 1 kg·m/s²
  Pressure, Stress	pascal	Pa	1 Pa = 1 N/m²
  Energy	joule	J	1 J = 1 N·m
  Power	watt	W	1 W = 1 J/s

• Rounding Rules: Numerical values should follow revised rounding rules (Clause 3.3).

Summary Diagram: Joint Sets Classification

flowchart TD
    A[Rock Mass Jointing] --> B(I: Massive, Occasional Random)
    A --> C(II: One Joint Set)
    A --> D(III: One Joint Set + Random)
    A --> E(IV: Two Joint Sets)
    A --> F(V: Two Joint Sets + Random)
    A --> G(VI: Three Joint Sets)
    A --> H(VII: Three Joint Sets + Random)
    A --> I(VIII: Four or More Joint Sets)
    A --> J(IX: Crushed Rock,

IS 11315 Part 9 — General Principles: Key Points

1. Classification of Joint Sets (Clause 5.2)

Number of joint sets along a tunnel or rock mass is classified as:

Major individual discontinuities should be recorded separately.

2. Visual Recognition & Numbering (Clause 4.4)

• Joint sets should be numbered systematically, e.g., "Set No. 1" for the most persistent/stable set.
• Alternatively, number sets by their importance to stability.

3. Units (SI Units)

Summary Diagram: Joint Set Classification

graph TD
  I[Massive, occasional random joints]
  II[One joint set]
  III[One joint set + random]
  IV[Two joint sets]
  V[Two joint sets + random]
  VI[Three joint sets]
  VII[Three joint sets + random]
  VIII[Four or more joint sets]
  IX[Crushed rock, earth-like]

  I --> II --> III --> IV --> V --> VI --> VII --> VIII --> IX

**Use this classification and numbering system for consistent rock mass discontinuity description as per IS

IS 11315 Part 9 focuses on the "Number of Sets" in structural systems, particularly for visual recognition and identification.

Key Points from IS 11315 Part 9:

• Number of Sets: Refers to distinct groups of structural elements or forces acting in different directions.
• Identification Method (Clause 4.4):
  • Use a systematic numbering for each set, e.g., "Set No. 1", "Set No. 2", etc.
  • Numbering can be based on stability importance or visual recognition.
  • This facilitates clarity in analysis and documentation.

Typical Approach to Determine Number of Sets:

1. Identify distinct force directions or load paths.
2. Group elements or forces acting similarly into one set.
3. Assign each set a unique number or label.

Example Table for Number of Sets:

Presentation of Results (Clause 5):

• Clearly list each set with its number and description.
• Include diagrams (e.g., Fig. 1 in the code) showing sets and numbering for easy reference.

graph LR
A[Identify Forces] --> B[Group into Sets]
B --> C{Number Sets}
C --> D[Set No. 1: Primary]
C --> E[Set No. 2: Secondary]
C --> F[Set No. 3: Tertiary]

This method ensures clarity and systematic analysis per IS 11315 Part 9.

Key Specifications & Guidelines for Field Survey and Data Collection (IS 11315 Part 9)

1. Recording Joint Sets (Clauses 4.1, 4.3 & 5.2):

• Identify and record all joint sets present in the mapped area.
• Use polar equal area nets to plot discontinuity poles; up to 150 joints may be measured.
• Classify rock mass based on number of joint sets locally:

• Major individual discontinuities must be recorded individually.

2. Interpretation Notes:

• Number of sets depends on area size and spacing of joints.
• Distinguish systematic (persistent, parallel joints) from non-systematic (random).
• Include incipient discontinuities if excavation disturbs rock mass.

3. Units & Symbols (SI Units):

Practical Tips for Field Survey:

• Use statistical tests on pole plots for set identification.
• Focus on local joint sets relevant to the structure (tunnel, slope).
• Record orientation, spacing, persistence of joints.

flowchart TD
    A[Field Survey Start] --> B[Measure Discontinuities (up to 150)]
    B --> C[Plot Poles on Polar Equal Area Net]
    C --> D{Identify Joint Sets}
    D -->|Systematic| E

IS 11315 Part 9: Data Presentation and Interpretation - Key Points

1. Joint Sets Classification (Clause 5.2)

• Major discontinuities should be recorded individually.
• Visual representation of joint sets is recommended (Clause 5.1).
• Number joint sets systematically by persistence or stability importance (Clause 4.4).

2. Units and Symbols (SI Units)

3. Rounding Off (Clause 0.6)

• Follow IS:2-1960 for rounding off final values in reports.

Summary Diagram: Joint Set Classification

flowchart TD
    A[Rock Mass] --> B{Number of Joint Sets}
    B -->|0| I[Massive, occasional random joints]
    B -->|1| II[One joint set]
    B -->|1 + random| III[One joint set plus random]
    B -->|2| IV[Two joint sets]
    B -->|2 + random| V[Two joint sets plus random]
    B -->|3| VI[Three joint sets]
    B -->|3 + random| VII[Three joint sets plus random]
    B -->|≥

IS 11315 Part 9: Reporting of Results - Key Points

1. Classification of Joint Sets (Clause 5.2)

Number of joint sets along a tunnel or rock mass is classified as:

• Major discontinuities must be recorded individually.

2. Units for Reporting (SI Units)

Use SI units consistently when reporting results:

• 1 N = 1 kg·m/s²
• 1 Pa = 1 N/m²

3. Rounding Off Results

• Follow IS:2-1960 for rounding off final observed or calculated values.

4. Identification of Joint Sets (Clause 4.4)

• Number joint sets systematically, e.g., "set No.1" for the most persistent/stable set.

flowchart LR
    A[Visual Inspection] --> B[Identify Joint Sets]
    B --> C{Number of Sets?}
    C -->|I| D[Massive, random joints]
    C -->|II| E[One joint set]
    C -->|III| F[One joint set + random]
    C -->|IV| G[Two joint sets]
    C -->|V| H[Two joint sets + random]
    C -->|VI| I[Three joint sets]
    C -->|VII| J[Three joint sets + random]
    C -->|VIII| K[Four or more sets]
    C -->|IX| L

IS 11315 Part 9: Notes on Application and Limitations (Joint Sets in Rock Masses)

Key Points from Clause 5.2 - Joint Sets Classification

• Joint sets along a tunnel or rock mass are classified as:

• Major discontinuities must be recorded individually.

Units & Symbols (SI Units)

• Length: m (metre)
• Force: N (newton), where 1 N = 1 kg·m/s²
• Pressure/Stress: Pa (pascal), where 1 Pa = 1 N/m²

Application Notes:

• Use systematic numbering for joint sets based on persistence or stability importance (e.g., Set No. 1 = most persistent).
• Visual identification should be supported by consistent labeling.
• This part focuses on number of joint sets, other parameters covered in other parts.

Summary Diagram: Joint Set Classification

graph TD
    A[Rock Mass]
    A --> I[Massive, occasional random joints]
    A --> II[One joint set]
    A --> III[One joint set + random]
    A --> IV[Two joint sets]
    A --> V[Two joint sets + random]
    A --> VI[Three joint sets]
    A --> VII[Three joint sets + random]
    A --> VIII[Four or more joint sets]
    A --> IX[Crushed rock, earth-like]

Use this classification to describe rock discontinuities and support stability analysis in tunneling or excavation design.