Selection of ground improvement techniques for foundation in weak soils -Guidelines

IS 13094: Scope & Key Specifications

Scope Summary (Clause 3.1)

• Defines terms related to ground improvement methods.
• Covers principles, applicability, equipment, materials, and results for various soil treatment techniques.

Key Data to Record (Clause 9.2)

• Operation sequence and spacing of treatment points.
• Depth of treatment.
• Equipment and installation details.
• Instrumentation records.
• Soil test results before/after treatment.
• Settlements during preloading.

Grain Size Ranges for Treatment Methods (Annex B, Clause 6.1.6.2)

Reference Table (Annex A, Clause 6.1.6.1)

• Guides selection of ground improvement method based on soil type, materials, equipment, and expected results.

Note: Use this standard for selecting and documenting appropriate ground improvement techniques, ensuring compliance with BIS quality control and inspection.

IS 13094: Referenced Standards & Key Specifications

Referenced Indian Standards (Clause 2.1)

• IS 1892:1979 – Code of Practice for Subsurface Investigation for Foundations
• IS 6403:1981 – Code of Practice for Determination of Bearing Capacity of Shallow Foundations
• IS 8009 (Part 1):1976 – Settlement Calculation for Shallow Foundations under Symmetrical Static Loads
• IS 8009 (Part 2):1980 – Settlement Calculation for Deep Foundations under Symmetrical Static Loads

Grain Size Ranges for Treatment Methods (Annex B, Clause 6.1.6.2)

Notes:

• The Standard Mark ensures compliance with BIS quality and testing protocols.
• For detailed design, refer to the above IS codes for formulas on bearing capacity, settlement, and subsurface investigations.

Summary:
IS 13094 references key IS codes essential for foundation design and treatment, specifying grain size ranges for various soil improvement methods in Annex B. Use these standards collectively for comprehensive foundation engineering.

IS 13094: Key Definitions & References

• Soil Reinforcement (Clause 3.4):
  Rods, strips, or fabrics embedded in soil to resist tensile, shear, and compressive forces.

• Related Standards (Clause 2.1):

  • IS 1892: Code for subsurface investigation for foundations
  • IS 6403: Code for bearing capacity of shallow foundations
  • IS 8009 (Part 1 & 2): Codes for settlement calculation of shallow and deep foundations under symmetrical static vertical loads

• Ground Improvement Methods (Clause 6.1.6.1 Annex A):
  Provides a tabulated guide on:

  • Principles of various ground improvement techniques
  • Soil condition applicability
  • Material and equipment requirements
  • Expected results and limitations

Summary Table: Soil Reinforcement Definition

For detailed design, refer to IS 1892 for subsurface data, IS 6403 for bearing capacity, and IS 8009 for settlement analysis.

flowchart LR
    A[Soil Mass] --> B[Reinforcement (rods, strips, fabrics)]
    B --> C[Improved Resistance]
    C --> D[Tensile, Shear, Compressive Forces]

This diagram shows soil reinforcement enhancing soil mass resistance to various forces.

IS 13094: Necessary Data for Soil Reinforcement and Ground Treatment

Key Data to Record (Clause 9.2)

• Sequence of operation of the work
• Sequence & spacing of treatment points
• Depth of treatment
• Equipment details and installation procedure
• Instrumentation records (if any)
• Soil test results before and after treatment
• Settlements during preloading

Essential Soil Properties (Clause 4.1.2)

• Index properties: e.g., grain size, Atterberg limits
• Shear parameters: cohesion (c), angle of internal friction (φ)
• Compressibility characteristics: e.g., modulus of elasticity, compression index

Relevant IS Codes for Reference (Clause 2.1)

Typical Formula: Bearing Capacity (IS 6403)

[ q_u = c N_c + \sigma N_q + 0.5 \gamma B N_\gamma ]

• (q_u): Ultimate bearing capacity
• (c): Cohesion
• (\sigma): Effective overburden pressure
• (\gamma): Unit weight of soil
• (B): Width of foundation
• (N_c, N_q, N_\gamma): Bearing capacity factors

flowchart TD
    A[Start: Site Investigation] --> B[Record Soil Properties]
    B --> C[Plan Treatment Points & Depth]
    C --> D[Select Equipment & Procedure]
    D --> E[Execute Treatment]
    E --> F[Monitor Instrumentation & Settlements]
    F --> G[Perform Post-Treatment Soil Tests]
    G --> H[Evaluate Results & Adjust Design]

This structured data collection ensures reliable design and quality control in soil reinforcement projects per IS 13094.

IS 13094: Key Points for Establishing Need for Ground Improvement

1. Information to Collect (Clause 4.1 & 4.1.4)

• Nature of structure: Type, size, and geometry.
• Area covered: Footprint and influence zone.
• Loading: Intensity, nature (static/dynamic), and distribution.
• Permissible distortions: Tolerable settlements and differential movements the structure can withstand.

2. Considerations (Clause 5)

• Soil conditions and bearing capacity.
• Expected settlements vs. permissible limits.
• Groundwater conditions.
• Environmental and construction constraints.
• Economic feasibility.

3. Selection of Ground Improvement Methods (Clause 6.1.6.1 & Annex A)

• Refer to Annex A for a tabulated guide on:
  • Methods: e.g., vibro-compaction, stone columns, grouting.
  • Soil applicability: Cohesive, cohesionless, organic soils.
  • Material & equipment requirements.
  • Expected improvement results.
  • Limitations and suitability.

Typical Decision Flow (Simplified)

flowchart TD
    A[Collect Site & Structure Data] --> B[Assess Soil & Loading Conditions]
    B --> C{Are Settlements Acceptable?}
    C -- Yes --> D[No Ground Improvement Needed]
    C -- No --> E[Select Ground Improvement Method (Annex A)]
    E --> F[Design & Implement Ground Improvement]

Summary Table Example (from Annex A)

Use IS 13094 Annex A as primary reference for method selection based on site-specific data.

IS 13094: Ground Improvement Methods - Key Points

1. Ground Improvement Methods (Clause 6.1 & Annex A)

• Various methods are tabulated in Annex A with:
  • Principles
  • Applicability to soil types (clays, silts, sands, etc.)
  • Material requirements
  • Equipment needed
  • Expected results
  • Limitations

2. Selection Guidelines (Clause 6.1.6.3)

• Multiple methods may be suitable for one site.
• Perform a comparative study considering:
  • Soil conditions
  • Cost
  • Time
  • Equipment availability
• Combination of methods may optimize results.

3. Equipment & Accessories (Clause 7)

• Equipment must:
  • Reach required depths
  • Avoid damaging soil structure during installation
• Choice depends on method and contractor resources.

4. Control of Works (Clause 8)

• Quality control is essential to ensure effectiveness.

Common Ground Improvement Methods (from IS 13094 Annex A summary)

Example: Bearing Capacity Improvement by Stone Columns

[ q_{ult} = q_{soil} + \eta \cdot q_{columns} ]

Where:

• ( q_{ult} ) = Improved ultimate bearing capacity
• ( q_{soil} ) = Original soil bearing capacity
• ( q_{columns} ) = Bearing capacity of stone columns
• ( \eta ) = Efficiency factor (typically 0.6 to 0.9)

flowchart TD
    A[Weak Soil] --> B[

IS 13094: Equipment and Accessories for Ground Improvement

Key Points from IS 13094

• Clause 6.1.6.3:
  Multiple methods may be suitable; select based on relative study or combine methods if needed.

• Clause 7 (Equipment and Accessories):

  • Equipment depends on the chosen ground improvement method.
  • Must reach required depths effectively.
  • Installation should not degrade subsoil properties or treatment efficacy.
  • Equipment varies with contractor design and resources.

• Clause 6.1.6.1 & Annex A:
  Annex A provides a comparative table of methods, soil applicability, material needs, equipment types, expected results, and limitations—useful for selecting equipment.

• Clause 9.2 (Data Recording):
  Record equipment details and installation procedures for quality control.

Typical Equipment Considerations (General Engineering)

Selection Criteria Summary

• Depth capability
• Effect on subsoil (avoid disturbance)
• Compatibility with soil type
• Availability and contractor resources

Mermaid Diagram: Equipment Selection Flow

graph TD
A[Start: Identify Soil & Improvement Method] --> B{Multiple Methods?}
B -- Yes --> C[Perform Relative Study]
B -- No --> D[Select Single Method]
C --> E{Combination Needed?}
E -- Yes --> F[Combine Methods & Equipment]
E -- No --> D
D --> G[Select Equipment based on Method]
G --> H[Check Depth & Soil Impact]
H --> I[Finalize Equipment & Accessories]

Summary: Use Annex A for method-equipment matching, ensure equipment reaches required depths without harming soil, and maintain detailed records per Clause 9.2 for quality control.

IS 13094: Control of Ground Improvement Works — Key Points

1. Selection of Method (Clause 6.1.6.3 & 6.1.6.1)

• When multiple ground improvement methods seem suitable, perform a comparative study considering:
  • Soil type
  • Material availability
  • Equipment feasibility
  • Expected results & limitations
• Combination of methods may be optimal.
• Refer to Annex A for a tabulated guide on:
  • Methods
  • Soil applicability
  • Material & equipment needs
  • Expected outcomes & limitations

2. Equipment & Installation (Clause 7)

• Equipment must:
  • Reach required depths
  • Not degrade subsoil properties
• Installation method must preserve soil integrity to ensure treatment efficacy.

3. Control of Works (Clause 8)

• Continuous monitoring of:
  • Equipment performance
  • Depth and uniformity of treatment
  • Soil property changes post-treatment
• Control procedures ensure desired bearing capacity and settlement limits are achieved.

Typical Control Parameters & Checks

Summary Diagram of Control Process

flowchart TD
    A[Site Investigation] --> B[Method Selection]
    B --> C[Equipment Selection]
    C --> D[Ground Improvement Execution]
    D --> E[Monitoring & Control]
    E --> F{Satisfactory Results?}
    F -- Yes --> G[Foundation Construction]
    F -- No --> B

Note: For detailed formulas and design tables, refer to Annex A of IS 13094 and related IS codes on soil improvement and foundation design.

IS 13094: Recording of Data – Key Points & Specifications

Data to be Recorded (Clause 9.2)

• Sequence of operation of the ground improvement work.
• Sequence and spacing of treatment points.
• Depth of treatment achieved.
• Details of equipment and installation procedure.
• Records of instrumentation used (pore pressure, earth pressure, settlement gauges).
• Results of soil tests before and after treatment.
• Measurement of settlements during preloading.

Testing & Monitoring (Clause 8.2)

• Repeat field and laboratory tests post-treatment to assess improvement.
• For medium/major works, conduct a trial area test to optimize treatment.
• Use instrumentation to monitor:
  • Pore water pressure
  • Soil movements
  • Earth pressures
  • Foundation settlements

Inspector Role (Clause 9.1)

• A competent inspector must record all necessary data during execution.

Typical Data Recording Table Format

flowchart TD
    A[Start Ground Improvement] --> B[Record Sequence of Operation]
    B --> C[Record Treatment Points & Spacing]
    C --> D[Record Depth of Treatment]
    D --> E[Record Equipment & Installation]
    E --> F[Monitor Instrumentation Data]
    F --> G[Conduct Soil Tests Before & After]
    G --> H[Record Settlements During Preloading]
    H --> I[Repeat Tests Post-Treatment]
    I --> J[Analyze & Optimize]

This structured recording ensures traceability and quality control in ground improvement works per IS 13094.

Summary of Soil Improvement Methods (IS 13094 - Annex A)

Injection and Grouting Methods

IS 13094 - Grain Size Ranges for Different Treatment Methods (Annex B, Clause 6.1.6.2)

Summary Notes:

• Vibro-compaction is effective for granular soils with low fines (<20%).
• Grouting methods vary by grout type: particulate for coarser soils, displacement for fine soils.
• Electro-osmosis targets fine-grained, saturated soils.
• Maximum effective depths vary by method (up to ~30 m for vibro-compaction and heavy tamping).

Visual Summary

graph LR
A[Soil Grain Size (mm)] -->|>4.75| Gravel
A -->|0.075-4.75| Sand
A -->|<0.075| Silt & Clay

Sand --> VibroComp[Vibro-compaction]
Sand --> PartGrout[Particulate Grouting]
SiltClay --> ElectroOs[Electro-osmosis]
SiltClay --> DisplaceGr[Displacement Gr