Method for the quantitative description of discontinuities in the rock mass, Part 7: Filling

IS 11315 Part 7 - Scope & Key Specifications

This part deals with the characterization and presentation of filled discontinuities in rock engineering, focusing on their influence on project stability.

Key Aspects of Scope (Clause 5.1):

• Description of Filled Discontinuities should include:
  • Width
  • Wall roughness
  • Field sketch
  • Filling type: mineralogy, particle size, weathering grade, soil index parameters, swelling potential
  • Filling strength: manual index (S1–S6), shear strength, over-consolidation ratio, displaced/undisplaced state
  • Seepage: water content (rated W1–W6), permeability, quantitative data

Manual Index Test (Clause 4.5) - Table 1:

Note: S1–S6 grades apply to cohesive soils (clays, silty clays). Rock discontinuities use R0–R6 (see Part 6).

Summary Diagram of Filled Discontinuity Characterization:

graph TD
  A[Filled Discontinuity] --> B[Width]
  A --> C[Wall Roughness]
  A --> D[Field Sketch]
  A --> E[Filling Type]
  E --> E1[Mineralogy]
  E --> E2[

IS 11315 Part 7 (1987) - Key References and Tables

Manual Index Test for Filling Material (Clause 4.5, Table 1)

• Applies to cohesive soils (clays, silty clays).
• Rock discontinuities use R0-R6 grades (see Part 6).
• Filling strength parameters include manual index, shear strength, over-consolidation ratio.

Presentation of Results (Clause 5.1)

• Report includes width, wall roughness, field sketch.
• Filling type details: mineralogy, particle size, weathering grade, soil index parameters, swelling potential.
• Filling strength: manual index (S1-S6), shear strength, over-consolidation ratio, displaced/undisplaced status.
• Seepage: water content rating (W1-W6), permeability data.

Additional Notes

• Round off values per IS 2-1960.
• Manual index test is a quick field assessment of soil strength.

flowchart TD
    A[Filling Material] --> B[Manual Index Test]
    B --> C{Grade S1-S6}
    C -->|S1| D[Very Soft Clay <0.025 MPa]
    C -->|S3| E[Firm Clay 0.05-0.10 MPa]
    C -->|S6| F[Hard Clay >0.

IS 11315 Part 7 - Definitions & Key Specifications

• Definitions: As per Clause 2.1, all terms follow IS 11358-1986 definitions.

• Filled Discontinuity Description (Clause 5.1):
  Present details including:

  • Width
  • Wall roughness
  • Field sketch
  • Filling type (mineralogy, particle size, weathering grade, soil index parameters, swelling potential)
  • Filling strength (manual index SI-S6, shear strength, over-consolidation ratio, displaced/undisplaced)
  • Seepage (water content rating W1-W6, permeability, quantitative data)

• Manual Index for Filling Strength (Clause 4.5, Table 1):

• Notes:
  • S1-S6 grades apply to cohesive soils (clays, silty clays).
  • Rock discontinuities use R0-R6 (see Part 6).
  • Filling strength guides engineering assessment of filled discontinuities.

flowchart TD
    A[Filled Discontinuity] --> B[Width]
    A --> C[Wall Roughness]
    A --> D[Field Sketch]
    A --> E[Filling Type]
    E --> E1[Mineralogy]
    E --> E2[Particle Size]
    E --> E3[Weathering Grade]

IS 11315 Part 7: Procedure for Description of Filled Discontinuities

Key Parameters for Description

1. Width & Wall Roughness

   • Measure discontinuity aperture (width).
   • Describe wall roughness qualitatively or via standard roughness profiles.

2. Filling Type
   | Parameter | Description | |---------------------|-------------------------------------------| | Mineralogy | Identify mineral composition | | Particle Size | Classify size (clay, silt, sand, gravel) | | Weathering Grade | Degree of weathering of filling material | | Soil Index Parameters | Plasticity, liquidity indices | | Swelling Potential | Qualitative rating or laboratory tests |

3. Filling Strength
   | Parameter | Description | |-------------------------|----------------------------------------------| | Manual Strength Index (SI-S6) | Field or lab-based strength rating | | Shear Strength | Measured via direct shear tests | | Over-consolidation Ratio| Indicates preloading history | | Displaced/Undisplaced | Whether filling has been moved or intact |

4. Seepage Characteristics
   | Parameter | Description | |-----------------|----------------------------------------------| | Water Content | Rated W1 (dry) to W6 (saturated) | | Permeability | Quantitative permeability data (e.g., k values) |

Presentation Format (Clause 5.1)

• Arrange data emphasizing project relevance.
• Include field sketches showing discontinuity geometry.
• Tabulate parameters as above for clarity.

Summary Table Example

flowchart TD
    A[Start: Identify Filled Discontinuity] --> B[Measure Width & Roughness]
   

IS 11315 Part 7 — Key Points on Measurement of Dimensions and Wall Conditions

1. Measurement of Filled Discontinuities (Clauses 4.1, 4.1.1, 4.1.2)

• Simple filled discontinuities (e.g., clay-filled joints):
  • Measure minimum and maximum widths to nearest ±10%.
  • Estimate the modal (most common) width.
  • Large width variation may indicate shear displacement if walls are unaltered.
• Complex filled discontinuities (e.g., shear zones, faults):
  • Estimate or measure principal dimensions to nearest ±10%.
  • Prepare field sketches showing wall rock condition (fracturing, alteration).
• Wall roughness:
  • Measure mean amplitude of wall roughness using a straight edge.
  • Compare roughness amplitude to mean filling width (see Fig. 1 in code).
  • Important for assessing shear strength and deformation.

2. Presentation of Results (Clause 5.1 & Table 5)

Report should include:

Summary Diagram of Measurement Process

flowchart TD
    A[Identify Discontinuity Type] --> B{Simple or Complex?}
    B -- Simple --> C[Measure min, max, modal widths ±10%]
    B -- Complex --> D[Estimate principal dimensions ±10%]
    D --> E[Prepare field sketches of wall condition]
    C --> F[Measure wall roughness amplitude]
    F --> G[Compare roughness to filling width]
    E & G --> H[Record filling type, strength, seepage]
    H --> I[Present results as per Table

IS 11315 Part 7 (1987) — Classification of Filling Material

Key Table: Manual Index for Filling Material (Clause 4.5)

Additional Specifications:

• Filling grading (Clause 4.4): Estimate % clay, silt, sand, rock particles ±10% by hand.
• Presentation of results (Clause 5.1): Include width, wall roughness, field sketch, filling type (mineralogy, particle size, weathering), filling strength (manual index, shear strength, over-consolidation), and seepage (water content rating W1-W6, permeability).
• Grades S1–S6 apply to cohesive soils (clays, silty clays).
• Rock discontinuities use grades R0–R6 (see Part 6).

Practical Use:

• Use manual field tests to classify filling strength quickly.
• Helps assess discontinuity stability in rock masses with filled joints.

flowchart TD
    A[Filling Material] --> B{Manual Penetration Test}
    B -->|Fist penetrates| S1[Very Soft Clay <0.025 MPa]
    B -->|Thumb penetrates easily| S2[Soft Clay 0.025-0.05 MPa]
    B -->|Thumb penetrates moderately| S3[Firm Clay 0.

IS 11315 Part 7: Mineralogical & Particle Size Analysis - Key Points

1. Mineralogical Analysis (Clause 4.3)

• Focus on finest fraction of filling/gouge as it controls long-term shear strength.
• Determine mineralogical composition, especially for active/swelling clays.
• Sampling required if mineralogy is uncertain.
• Hydrothermal alteration may complicate identification.

2. Particle Size Classification (Clause 4.4.1, IS 1498-1970)

3. Manual Index Tests for Filling Material (Clause 4.5, Table 1)

Summary Workflow for Analysis:

flowchart TD
    A[Sample Collection] --> B[Particle Size Estimation]
    B --> C{Estimate % of Clay, Silt, Sand, Rock}
    C --> D[Manual Index Tests on Fine Fraction]
    D --> E[Mineralogical Composition Analysis

IS 11315 Part 7 (1987) — Laboratory Testing of Filling Material

Key Table: Manual Index for Filling Material (Clause 4.5)

• Grades S1 to S6 apply to cohesive soils (clays, silty clays).
• Used for quick field estimation of filling material strength.

Presentation of Results (Clause 5.1)

• Describe:
  • Width of filled discontinuity
  • Wall roughness
  • Field sketch
  • Filling type: mineralogy, particle size, weathering grade, soil index parameters, swelling potential
  • Filling strength: manual index (S1–S6), shear strength, over-consolidation ratio, displaced/undisplaced state
  • Seepage: water content rating (W1–W6), permeability data

Summary Diagram of Manual Index Test

graph TD
    A[Filling Material] --> B{Field Penetration Test}
    B -->|Fist penetration| S1[Very Soft Clay <0.025 MPa]
    B -->|Thumb easy penetration| S2[Soft Clay 0.025-0.05 MPa]
    B -->|Thumb moderate effort| S3[Firm Clay 0.05-0.10 MPa]
    B -->|Thumb indentation| S4[Stiff Clay 0.

IS 11315 Part 7 (1987) — Manual Index Tests for Filling Strength

Key Table: Manual Index (Clause 4.5)

Notes:

• Grades S1 to S6 apply to cohesive soils (clays, silty clays, clay-silt-sand mixes).
• Manual test can be replaced by a soil mechanics penetrometer, measuring max resistance, related as:
  [ \text{Max Resistance} = 2 \times \text{Undrained Shear Strength} = 2 \times (c_u) ]
• Presentation of results should include:
  • Filling type (mineralogy, particle size, weathering, swelling potential)
  • Filling strength (manual index grade, shear strength, over-consolidation ratio)
  • Seepage (water content rating W1–W6, permeability)

Practical Tip:

Use a straight edge to measure wall roughness amplitude vs filling width (Fig.1, Clause 4.1.1) for detailed shear strength assessment.

flowchart TD
    A[Manual Index Test] --> B{Penetration Effort}
    B -->|Fist| S1[Very Soft Clay <0.025 MPa]
    B -->|Thumb Easy| S2[Soft Clay 0.025-

Assessment of Shear Displacement and Over-Consolidation
(IS 11315 Part 7, Clauses 4.6 & 4.5)

Key Points:

• Shear Displacement Evidence:
  Look for slickensides, shears, displaced cross joints indicating prior shear displacement through clay filling.

• Over-Consolidation Ratio (OCR):

  • If displacement occurred, discontinuity strength ~ residual strength; OCR less critical.
  • If no displacement, OCR important as peak shear strength > residual strength.
  • Beware of strength reduction over time due to swelling, softening, strain softening, especially under unloading or excavation.

Manual Index Test for Clay Filling (Table 1, Clause 4.5)

• Note: Penetrometer readings = 2 × undrained shear strength.

Practical Recommendations:

• Record displacement status (displaced/undisplaced) and OCR during field assessment.
• Use manual index or penetrometer for clay strength classification.
• Consider time-dependent strength loss due to swelling and softening in design.

flowchart TD
    A[Filled Discontinuity] --> B{Previous Shear Displacement?}
    B -- Yes --> C[Residual Strength Dominates]
    B -- No --> D[Peak Strength Depends on OCR]
    D --> E[

IS 11315 Part 7: Water Content and Permeability Evaluation

Water Content Rating (Clause 4.7)

Note: Flow is often anisotropic, mainly parallel to fault planes.

Manual Index Test for Filling Strength (Clause 4.5, Table 1)

Key Factors Affecting Water Content & Permeability (Clause 3.3)

• Mineralogy of filling material
• Particle size distribution
• Over-consolidation ratio
• Water content & permeability
• Previous shear displacement
• Wall roughness
• Fracturing/crushing of wall rock

Presentation of Results (Clause 5.1)

• Width, wall roughness, field sketch
• Filling type: mineralogy, particle size, weathering, soil index,

IS 11315 Part 7: Presentation of Results - Key Points

1. Presentation Format (Clause 5.1)

Results should describe the filled discontinuity including:

• Width
• Wall roughness
• Field sketch
• Filling type: mineralogy, particle size, weathering grade, soil index parameters, swelling potential
• Filling strength: manual index (SI-S6), shear strength, over-consolidation ratio, displaced/undisplaced condition
• Seepage: water content rating (W1-W6), permeability, quantitative data

2. Manual Index (Table 1, Clause 4.5)

Used to estimate uniaxial compressive strength (UCS) of filling material:

3. Water Content Rating (Clause 4.7)

4. Rounding Off (Clause None)

Key Specifications & Tables for Field Sketches (IS 11315 Part 7)

1. Field Sketch Essentials (Clause 4.1.2 & 5.1)

• Sketch principal dimensions of filled discontinuities (shear zones, faults, dykes) to nearest ±10%.
• Include wall rock condition: fracturing, alteration.
• Present:
  • Width
  • Wall roughness
  • Filling type & strength
  • Seepage characteristics
• Use sketches to communicate degree of fracturing and alteration (see Fig. 2 in code).

2. Filling Type Description (Clause 5.1)

3. Filling Strength (Clause 5.1 & Table 1)

• Use manual index tests to classify soil strength:

4. Seepage (Clause 5.1)

• Record water content rating W1 to W6.
• Note permeability and any quantitative seepage data.

Summary Flow for Field Sketch & Data Collection

flowchart TD
    A[Identify