Indian Standard Code IS 8763

IS 8763: Introduction - Key Points and Specifications

IS 8763 primarily deals with sampling and testing of cemented sands for foundation investigations.

Key Specifications:

• Scope: Guide for undisturbed sampling of sands, especially cemented sands.
• Purpose: To ensure reliable site exploration and foundation design.
• Sampling Method: Emphasizes undisturbed sampling techniques to maintain soil structure.
• Relevant Clauses: Clause 4.1 includes tables for sampling procedures (e.g., Table 4: Sampling in Cemented Sands).

Important Notes:

• The code is prepared by experts from PWD, CSIR, and other institutions.
• Regional and branch offices of BIS are available for consultation and purchase.
• The document complements other IS codes on soil investigation and foundation design.

Typical Sampling Considerations (General Engineering Knowledge):

flowchart LR
    A[Site Exploration] --> B[Undisturbed Sampling]
    B --> C[Sample Preservation]
    C --> D[Laboratory Testing]
    D --> E[Foundation Design]

Summary: IS 8763 guides undisturbed sampling of cemented sands to ensure accurate soil characterization for foundation engineering. Refer to Clause 4.1 for detailed sampling tables.

IS 8763: Scope Summary & Key Specifications

Scope:
IS 8763 covers equipment and methods for sampling cemented sands using specialized drilling and sampling tools.

Key Equipment Components (Clause 3.1)

• Drilling equipment with casing pipes of 152 mm diameter.
• Compressed air bell housing the sampler tube.
• Connection via hose to a foot pump at ground surface for air pressure.
• Optional techniques include freezing or chemical impregnation (e.g., kerosene, alcohol + dry ice) to solidify samples and improve retention.

Sampling in Cemented Sands (Clause 4.1)

• Refer to Table 4 (not fully provided here) for sampling methods and parameters specific to cemented sands.
• Solidification techniques ensure sample integrity during extraction.

Notes on Practice

• Freezing or impregnation helps maintain sample structure.
• Equipment and procedures align with international standards adapted for Indian conditions.

flowchart LR
    A[Drilling Equipment] --> B[Casing Pipes (152 mm dia.)]
    B --> C[Compressed Air Bell]
    C --> D[Sampler Tube]
    D --> E[Foot Pump at Surface]
    F[Optional] --> G[Freezing / Chemical Impregnation]
    G --> D

For detailed formulas and tables, refer to Clause 4.1 Table 4 in the full standard document.

IS 8763: Stationary Piston Sampling with Drilling Fluid Circulation

Key Specifications & Equipment (Clause 2.1)

• Sampler: Thin-walled sampler per IS 2132-1972.
• Piston: Airtight with vacuum breaker rod inside.
• Sampler Head: Set screws, vent hole, clamping to hold piston rod.
• Piston Rods: Straight, sturdy, 1 m joint spacing.
• Drilling Fluid Tank: Bentonite slurry, agitated continuously.
• Effluent Tank: Separates sand from drilling fluid for recirculation.

Sampling Procedure (Clauses 2.2.1, 2.2.3.1)

• Create partial vacuum above piston during withdrawal to maintain sample integrity.
• Drilling fluid coating at sampler shoe prevents sand disturbance.
• Drilling fluid specific gravity ~1.05 for fine sands.
• Piston starts at sampler shoe to avoid shavings entering tube.
• Sampler lowered with extended piston rod; tube pushed into virgin soil.
• Piston rod clamped during sampling to prevent movement.

Important Notes

• Drilling fluid consistency depends on:
  • Grain size
  • Relative density
  • Water table conditions

Diagrammatic Concept (Fig.1 simplified)

flowchart TB
    A[Sampler Tube] --> B[Piston at Shoe]
    B --> C[Partial Vacuum Above Piston]
    C --> D[Drilling Fluid Coating at Shoe]
    D --> E[Virgin Soil Sample]
    style B fill:#f9f,stroke:#333,stroke-width:2px
    style C fill:#bbf,stroke:#333,stroke-width:2px

This technique ensures undisturbed sampling by controlling vacuum and fluid circulation, preventing sample contamination or disturbance.

IS 8763: Compressed Air Sampling Technique - Key Points

Purpose:

• To obtain undisturbed sand samples below the water table by preventing groundwater mixing using compressed air.

Key Specifications & Components:

Working Principle (Clause 3.2.1):

• Compressed air is pumped continuously into the bell to displace groundwater.
• The pressure of compressed air = hydrostatic pressure of water column in the borehole.
• After sampling, the tube is withdrawn into the bell, maintaining sample integrity.

Sampling Procedure (Clause 3.2.2.5):

1. Remove spacer block above the bell.
2. Push sampler out of the bell and disconnect sampling tube.
3. Place a filter plug at the lower end.
4. Release suction created by check valve to obtain an undisturbed sample.

Diagram (General Layout):

flowchart TB
    A[Compressed Air Line] --> B[Compressed Air Bell]
    B --> C[Sampling Tube (63 mm OD)]
    C --> D[Filter Plug (Lower End)]
    B --> E[Water Exit Port]
    B --> F[Rubber Diaphragm & Sealing Rings]
    B --> G[Adapter Rod (38 mm)]

Notes:

• The compressed air pressure must match the water depth pressure to avoid sample disturbance.
• Suitable for sampling sands under water table without drilling fluid contamination.

This technique ensures undisturbed sand samples critical for geotechnical analysis.

IS 8763: Sampling in Cemented Sands – Key Points

IS 8763 provides guidelines for undisturbed sampling of sands, including cemented sands, focusing on equipment and procedure to minimize disturbance.

Key Specifications:

• Sampling Tube:

  • Outer Diameter (OD): 63 mm
  • Thickness: 1.7 mm

• Casing Pipe:

  • Diameter: 152 mm

• Auxiliary Equipment:

  • Compressed air bell for sample extraction (to reduce disturbance)

Sampling Procedure Highlights for Cemented Sands:

• Use rigid sampling tubes with sharp cutting edges to penetrate cemented layers.
• Apply compressed air pressure via the bell to facilitate sample retrieval without breaking cement bonds.
• Maintain vertical alignment to avoid sample distortion.

General Layout (Fig. 2):

• Sampling tube inserted inside casing pipe.
• Compressed air bell surrounds tube to assist sampling.

Typical Dimensions Summary:

This setup ensures undisturbed samples for accurate lab testing of cemented sands' strength and permeability.

flowchart TB
    A[Compressed Air Bell] --> B[Sampling Tube (63 mm OD)]
    B --> C[Cemented Sand Sample]
    D[Casing Pipe (152 mm)] --> B
    style A fill:#f9f,stroke:#333,stroke-width:2px
    style B fill:#bbf,stroke:#333,stroke-width:2px
    style C fill:#bfb,stroke:#333,stroke-width:2px
    style D fill:#fbb,stroke:#333,stroke-width:2px

IS 8763: Sampling Equipment and Accessories - Key Specifications

• Sampling Tube:

  • Outer Diameter (OD): 63 mm
  • Thickness: 1.7 mm
  • Thin-walled sampler per IS 2132-1972

• Casing Pipe:

  • Diameter: 152 mm

• Compressed Air Bell:

  • Houses the sampler tube
  • Connected via hose to a foot pump at ground surface

• Sampler Head Components:

  • Set screws to join sampling tube
  • Vent hole for pressure equalization
  • Clamping arrangement to secure piston rod

• Piston Rods:

  • Sturdy, straight rods with 1 m joint spacing

• Storage and Separation Tanks:

  • Storage tank for drilling fluid (usually bentonite slurry), kept agitated
  • Separation tank to recover drilling fluid from sand particles for recirculation

Figure 2 (general layout) shows the integration of these components with the compressed air bell and casing pipe.

Summary Table of Key Dimensions

flowchart TD
    A[Foot Pump] -->|Air Hose| B[Compressed Air Bell]
    B --> C[Sampler Tube (63 mm OD)]
    C --> D[Piston with Vacuum Break]
    D --> E[Sampling Head]
    E --> F[Piston Rods (1 m joints)]
    F --> G[Storage Tank (Bentonite Slurry)]
    G --> H[Separation Tank]

This layout ensures efficient sand sampling with airtight piston operation and fluid recirculation as per IS 8763.

IS 8763 Sampling Procedures and Field Operations

Key Clauses Overview:

• Clause 2.2 & 2.2.2: Describe the technique and procedure for sampling materials.
• Clause 3.2 & 3.2.2: Detail the field sampling procedure during construction.

Sampling Procedure Summary:

1. Sampling Technique:

   • Samples must be representative of the batch or lot.
   • Use random or systematic sampling depending on material uniformity.
   • Avoid contamination and ensure proper labeling.

2. Field Sampling Steps:

   • Identify the sampling location as per the test requirement.
   • Use clean, dry containers for collection.
   • Collect samples at specified intervals or quantities.
   • Record date, time, and conditions during sampling.

Typical Sampling Quantities (Example for Aggregates):

Important Notes:

• Follow IS 2386 for aggregate sampling.
• Maintain chain of custody for samples.
• Ensure immediate transport to the lab to avoid property changes.

flowchart TD
    A[Identify Sampling Point] --> B[Collect Sample]
    B --> C[Label & Document Sample]
    C --> D[Transport Sample to Lab]
    D --> E[Testing & Analysis]

For detailed tables and exact quantities, refer to IS 8763 Clauses 2.2 & 3.2.

IS 8763: Sample Handling and Preservation (Key Points)

• Freezing Technique: Used to solidify the lower part of sand samples inside the sampler tube, preserving the sample's in-situ structure.
• Impregnation Methods: Alternative to freezing; involves injecting chemicals like:
  • Kerosene at subzero temperatures
  • Alcohol mixed with dry ice
  • Emulsified asphalt
  • Grout mixtures

These methods prevent disturbance during extraction and transport.

Summary Table: Preservation Techniques for Sand Samples

Key Specifications:

• Preserve sample integrity by minimizing disturbance.
• Use freezing or impregnation depending on site conditions.
• Maintain temperature control during transport.

flowchart LR
    A[Sampling] --> B[Freezing]
    A --> C[Chemical Impregnation]
    B --> D[Solidified Sample]
    C --> D
    D --> E[Transport & Testing]

This ensures undisturbed sand samples for accurate geotechnical analysis.

IS 8763: Quality Control and Limitations Summary

The provided context mainly lists offices and contacts, with no direct formulas or tables on Quality Control or Limitations. Based on IS 8763 (Guide for Undisturbed Sampling of Sands), key points are:

Quality Control in Sampling:

• Sampling Method: Use undisturbed sampling techniques to maintain soil structure.
• Sample Size & Number: Follow prescribed sampling numbers (see typical sampling tables in IS 8763).
• Handling: Prevent moisture loss or contamination during transport.
• Testing: Conduct tests like grain size, moisture content, and strength on samples.

Limitations:

• Sampling is limited by soil type (mostly sands).
• Disturbance during sampling affects test accuracy.
• Depth and accessibility may restrict sampling.

Typical Sampling Table (Example):

General Formula for Sampling Frequency:

[ n = \frac{A}{S} ]

• (n) = number of samples
• (A) = area under investigation
• (S) = sampling unit area (depends on soil variability)

flowchart TD
    A[Start Sampling] --> B[Select Sampling Location]
    B --> C[Use Undisturbed Sampler]
    C --> D[Extract Sample Carefully]
    D --> E[Preserve Moisture & Structure]
    E --> F[Transport to Lab]
    F --> G[Conduct Tests]
    G --> H[Analyze Data]
    H --> I[Quality Control Check]
    I --> J{Accept or Reject Sample?}
    J -->|Accept| K[Use Data for Design]
    J -->|Reject| B

Note: For detailed tables, sampling procedures, and limitations, refer to IS 8763 full text.

IS 8763: Safety and Environmental Considerations Summary

Key Safety Specification (Clause 2.2.3.3)

• Piston/Piston Rod Safety:
  • Use a piston rod locking device (e.g., conical catch) to prevent accidental falling.
  • Check locking device before each use to ensure proper function.

Environmental Considerations (Clause 3.1)

• Sample Preservation Techniques:
  • Use freezing or chemical impregnation to solidify sand samples in the sampler tube.
  • Chemicals: kerosene at subzero temperature, alcohol + dry ice, emulsified asphalt, grout.
  • These methods prevent sample disturbance and environmental contamination.

Equipment (Clause 3.1)

• Compressed Air Bell:
  • Houses sampler tube.
  • Connected to a foot pump via hose for controlled air pressure.
• Casing Pipes:
  • Diameter: 152 mm standard.

Summary Table: Safety Device Check

flowchart TD
    A[Piston Rod] --> B[Locking Device (Conical Catch)]
    B --> C{Is Locking Device Functional?}
    C -- Yes --> D[Proceed with Operation]
    C -- No --> E[Repair/Replace Device]

This ensures operator safety and sample integrity per IS 8763 guidelines.

IS 8763 primarily deals with sampling in cemented sands and provides specifications for sampling equipment and procedures rather than typical bibliographic references.

Key Specifications from IS 8763:

• Sampling Tube:

  • Outer Diameter (OD): 63 mm
  • Thickness: 1.7 mm

• Casing Pipe Diameter:

  • 152 mm

• Auxiliary Equipment:

  • Compressed Air Bell for sampling assistance

Sampling Equipment Layout:

• Figure 2 in the code shows the general layout of sand sampler with auxiliary bell.

Notes on References and Bibliography:

• IS 8763 does not provide explicit formulas or bibliographic tables.
• It references institutions like CSIR Central Road Research Institute, Public Works Departments, and Indian Standards Bureau for technical backing.
• For detailed formulas or standards on soil sampling and testing, refer to related IS codes such as IS 2720 (Soil Testing) series.

Summary Table:

If you need formulas for sampling volume or soil strength, please specify.