Methods of test for soils, Part 28: Determination of dry density of soils, in-place, by the sand replacement method

IS 2720 Part 28 - Scope: Key Specifications & Formulas

Scope:
This part covers determination of dry density of soil in-place by sand replacement method, using standard apparatus like pouring cylinders, core cutters, and calibrating containers.

Key Apparatus Dimensions (mm)

Essential Formulas

• Bulk Density of Sand, γ (kg/m³):
  [ \gamma = \frac{W}{V} \times 1000 ]
  Where:

  • (W) = weight of sand (g)
  • (V) = volume of calibrating container (ml)

• Dry Density of Soil, (\rho_d) (kg/m³):
  [ \rho_d = \frac{W_s \times \gamma}{100 + w} ]
  Where:

  • (W_s) = weight of wet soil (g)
  • (w) = water content (%)
  • (\gamma) = bulk density of sand (kg/m³)

Notes

• Essential dimensions have ±0.1 mm tolerance (±1 mm for large cylinders).
• Alternative designs allowed if essential requirements are met.
• Sand used must be clean, uniformly graded natural sand (1.00 mm to 600 micron IS sieve), oven dried, free from organic matter.

flowchart TD
    A[Start: Soil Hole Excavation] --> B[Weigh Wet

IS 2720 Part 28 (1974) — Apparatus Specifications and Calibration

Key Apparatus Dimensions & Specifications

Calibration Clauses

• Clause 4.1 & 10.1: Emphasize calibration of apparatus before use to ensure accuracy.

Notes:

• Essential dimensions are underlined in the original figures.
• Tolerances: ±1 mm for major dimensions; ±0.1 mm for precision tools.
• Alternative designs allowed if essential requirements are met.

Summary Diagram of Sand Pouring Cylinder Dimensions

graph TD
A[Top Diameter (A)] --> B[Height (C)]
B --> C[Base Diameter (B)]
C --> D[Handle (E)]
D --> E[Capacity (Litres)]

This ensures precise volume measurement critical for soil density determination.

IS 2720 Part 28: Sampling and Preparation - Key Formulas & Specifications

1. Water Content Determination (Clause 2.5 & Appendix B)

• Water content ( w % ) of soil fraction passing 4.75 mm IS Sieve:

[ w = \frac{W_{\text{wet soil}} - W_{\text{dry soil}}}{W_{\text{dry soil}}} \times 100 ]

• Oven dry representative sample at 105-110°C until constant weight.

2. Sand Specifications (Clause 9.1)

• Use clean, uniformly graded natural sand passing 1.00 mm and retained on 600 micron IS Sieve.
• Free from organic matter.
• Oven dried and equilibrated with atmospheric humidity before use.

3. Sand Pouring Cylinder Dimensions (Clause 2.8 & Figures)

4. Dry Density Calculation (Appendix A)

• Bulk density of sand:

[ \gamma = \frac{W}{V} \times 1000 \quad \text{(kg/m}^3\text{)} ]

• Dry density of soil:

[ \rho_d = \frac{\rho}{1 + \frac{w}{100}} \quad \text{where } w = \text{water content %} ]

5. Typical Test Data Table (Appendix A)

IS 2720 Part 28: Calibration of Apparatus - Key Points

1. Cylindrical Calibrating Container (Clause 8.3)

• Internal diameter: 200 mm
• Internal depth: 250 mm
• Flange: 75 mm wide, ~5 mm thick
• Volume accuracy: ±0.15%
• Purpose: Used for calibration of pouring cylinders.

2. Metal Tray with Hole (Clause 2.8)

• Dimensions: 300 mm × 300 mm × 40 mm deep
• Hole diameter: 100 mm at center

3. Sand-Pouring Cylinder Dimensions (Fig. 1)

• Tolerance on essential dimensions: ±1 mm
• All dimensions in mm

4. Calibration Formula for Volume of Cylinder

[ V = \pi \times \left(\frac{d}{2}\right)^2 \times h ]

• (d) = internal diameter
• (h) = internal depth

Summary

• Use the calibrating container for volume calibration with ±0.15% accuracy.
• Dimensions and tolerances are strictly followed for pouring cylinders.
• Alternative designs allowed if essential requirements are met.

flowchart LR
    A[Calibrating Container] --> B[Measure Volume Accurately ±0.15%]
    B --> C[Calibrate Pouring Cylinder Volume]
    C --> D[Use in Density Determination]

This ensures precise volume measurement crucial for soil density tests.

IS 2720 Part 28: Key Formulas & Specifications for Sand Replacement Test

1. Test Procedure Overview

• Two methods: Small Pouring Cylinder (fine & medium soils) and Large Pouring Cylinder (fine, medium & coarse soils).
• Record weights before and after pouring sand to calculate volume and density.

2. Key Formulas

Where:

• ( W_1 ) = Weight of sand + cylinder before pouring
• ( W_2 ) = Weight of sand + cylinder after pouring
• ( W_3 ) = Weight of sand in calibrating container
• ( V ) = Volume of calibrating container (ml)
• ( W_s ) = Weight of sand filling hole
• ( w ) = Water content (%)

3. Pouring Cylinder Dimensions (mm)

Essential dimensions underlined; tolerance ±1 mm.

4. Recording Format (Appendix A)

IS 2720 Part 28: Reporting of Results - Key Points

• Dry Density (ρd):

  • Report in kg/m³ (nearest whole number) or g/cm³ (to 2 decimal places).
  • Formula:
    [ \rho_d = \frac{\rho}{1 + w} ] where
    (\rho) = bulk density (kg/m³),
    (w) = water content (decimal).

• Water Content (w):

  • Report as a percentage to two significant figures.

• Special Note for Gravelly Soils:

  • For soils with gravel (>4.75 mm), determine water content & dry density as per Appendix B.

• Method Declaration:

  • State the test method used, e.g., Large Pouring Cylinder Method (Clause 12.1).

• Recording:

  • Use the pro forma in Appendix A for consistent documentation.

Summary Table for Reporting

flowchart TD
    A[Soil Sample] --> B[Determine Bulk Density (ρ)]
    A --> C[Determine Water Content (w)]
    B & C --> D[Calculate Dry Density (ρd = ρ/(1+w))]
    D --> E[Report Results]
    E --> F[Include Test Method & Use Pro Forma (Appendix A)]

This ensures clarity, accuracy, and uniformity in reporting soil density and moisture content as per IS 2720 (Part 28).

Key Calculations from IS 2720 Part 28 (Measurement of Soil Density)

1. Water Content (w%)

For soil fraction passing 4.75 mm sieve:
[ w = \frac{W_{\text{wet}} - W_{\text{dry}}}{W_{\text{dry}}} \times 100 ]

• (W_{\text{wet}}) = Weight of wet soil sample
• (W_{\text{dry}}) = Weight of oven-dried soil sample

2. Bulk Density of Sand (γ)

[ \gamma = \frac{\text{Weight of sand}}{\text{Volume of calibrating container}} \times 1000 \quad \text{(kg/m}^3\text{)} ]

3. Bulk Density of Soil in Hole (ρ)

[ \rho = W \times \gamma ]

• (W) = Weight of sand filling the hole (difference before and after pouring)
• (\gamma) = Bulk density of sand

4. Dry Density of Soil (ρ_d)

[ \rho_d = \frac{\rho \times 100}{100 + w} ]

Tabulated Data for Calculations

Summary Diagram

flowchart TD
    A[Measure sand weight before pouring (W1)] --> B[Pour sand into hole]
    B --> C[Measure sand weight after pouring (W2)]
    C --> D[Calculate

IS 2720 Part 28: Tools for Excavating Holes

Key Tools (Clauses 2.2 & 8.2)

• Bent spoon
• Dibber (Fig. 3): Steel rod, 300 mm length, 5–10 mm diameter, wooden handle
• Large screwdriver
• Pointed steel rod (~300 mm long, 5–10 mm dia)
• Scraper tool (Fig. 2) for leveling surface

Specifications for Dibber (Fig. 3)

• Essential dimensions underlined (tolerance ±0.1 mm)
• Hardened cutting edge, corner rounded off
• Design is a guideline; alternatives allowed if essential requirements met

Formula for Weight of Sand to Fill Hole (Clause 5.3)

[ W = W_1 - W_2 - W_3 ]

Where:

• (W) = Weight of sand required to fill hole (g)
• (W_1) = Weight of cylinder + sand before pouring (g)
• (W_2) = Weight of cylinder + sand after pouring into hole and cone (g)
• (W_3) = Mean weight of sand in cone (g)

Summary Diagram: Tools for Excavating Holes

graph LR
A[Excavation Tools] --> B[Bent Spoon]
A --> C[Dibber (Fig.3)]
A --> D[Large Screwdriver]
A --> E[Pointed Steel Rod]
A --> F[Scraper Tool (Fig.2)]

This ensures precise hole excavation for soil density tests as per IS 2720 Part 28.

Sand Pouring Cylinder Specifications (IS 2720 Part 28)

Key Dimensions & Capacity (Fig. 1)

• Small: For fine and medium-grained soils.
• Large: For fine, medium, and coarse-grained soils.

Procedure Summary (Clauses 10.2.4 & 10.1.2.2)

• Fill pouring cylinder with constant sand weight ( W_1 ).
• Place concentrically over hole on metal tray (300 × 300 × 40 mm with 100 mm hole).
• Close shutter during filling, then open to pour sand.
• Close shutter when sand stops flowing.
• Remove cylinder and weigh remaining sand to nearest 0.1% of ( W_1 ).

Notes

• Essential dimensions have ±1 mm tolerance.
• Handle provided only for large cylinder.
• Alternative designs allowed if essential requirements met.

Illustration of Setup

flowchart TD
    A[Pouring Cylinder filled with sand (W1)] --> B[Placed concentrically over hole]
    B --> C[Shutter opened, sand poured out]
    C --> D[Shutter closed when flow stops]
    D --> E[Cylinder removed]
    E --> F[Remaining sand weighed]

This ensures accurate density determination by measuring sand volume displaced.

IS 2720 Part 28: Bulk Density of Sand - Key Formulas & Tables

Method Summary (Clause 10.1.2, 4.1.2)

• Use small or large pouring cylinder to determine bulk density (Y).
• Calibrate container volume (V) in ml.
• Weigh sand before and after pouring.

Key Formulas

Typical Data Table (Appendix A)

Notes:

• Bulk density (Y) is mass per unit volume of sand.
• Dry density (Y_d)

IS 2720 Part 28: Water Content & Dry Density for Soils with Gravel

Key Points from Appendix B (Clause 11.2):

• Applicable for medium- and coarse-grained soils with gravel > 4.75 mm.
• Gravel volume (Vg) is determined by water displacement or weighing in air & water.
• Specific gravity of gravel (Gg) is calculated from volume and weight.
• Oven-dry weight (W'g) and water content (wg) of gravel are determined separately.
• Bulk density of soil is corrected by subtracting gravel volume and mass.

Formulas:

1. Gravel Specific Gravity: [ G_g = \frac{W_g}{V_g \times \rho_w} ] where
   (W_g) = oven-dry weight of gravel,
   (V_g) = volume of gravel,
   (\rho_w) = density of water (1000 kg/m³).

2. Water Content of Gravel: [ w_g = \frac{W_{wet,g} - W_{dry,g}}{W_{dry,g}} \times 100% ]

3. Dry Density of Soil (excluding gravel): [ \rho_d = \frac{W_{soil,dry} - W_{gravel,dry}}{V_{hole} - V_g} ]

4. Water Content of Soil: [ w = \frac{W_{wet,soil} - W_{dry,soil}}{W_{dry,soil}} \times 100% ]

Reporting Table (Summary):

IS 2720 Part 28: Key Formulas & Tables from Appendices

Appendix A: Dry Density by Sand Replacement

Appendix B: Water Content & Dry Density for Gravelly Soils

• Use metal tray with 100 mm hole (300 mm × 300 mm × 40 mm deep) for bulk density.
• Follow procedure for medium- and coarse-grained soils with gravel (>4.75 mm).

Sand Pouring Cylinder Dimensions (mm)

Summary Formula for Dry Density (Appendix A):

[ \rho_d = \frac{W_{soil}}{V_{hole}} \times \frac{100}{100 + w} ]

Where:

• ( W_{soil} ) = weight of wet soil from hole (g)
• ( V_{hole}

IS 2720 Part 28 (1974) - Key Formulas & Tables for Soil Density & Water Content

Key Formulas (Appendix B & Clause 3.1)

Sand Replacement Method (Appendix A)

• Bulk density of sand, γ = (Weight of sand in cone) / (Volume of calibrating container) × 1000 (kg/m³)
• Dry density of soil, ρ = Bulk density × 100 / (100 + water content %)

Apparatus & Specifications

• Core cutter: Hardened cutting edge, essential dimensions ±0.1 mm.
• Calibrating container: For sand volume calibration.
• Dibber: For digging density holes (20 mm conduit diameter).

Reference for detailed procedure:

• IS 2720 (Part 28): 1974, Appendix A & B
• Contact BIS offices for official copies and updates.

flowchart TD
    A[Measure Hole Volume] --> B[Weigh Wet Soil]
    B --> C[Calculate Wet Density]
    C --> D[Determine Water Content]
    D --> E[Calculate Dry Weight & Dry