Physico-mechanical test


PHYSICO-MECHANICAL TEST

 

1. WATER CONTENT DETERMINATION 


Purpose: This test is performed to determine the water (moisture) content of soils.  The water content is the ratio, expressed as a percentage, of the mass of “pore” or “free” water in a given mass of soil to the mass of the dry soil solids. 
Standard Reference: ASTM D 2216 - Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil, Rock, and Soil-Aggregate Mixtures 
 

Significance: For many soils, the water content may be an extremely important index used for establishing the relationship between the way a soil behaves and its properties. The consistency of a fine-grained soil largely depends on its water content.   The water content is also used in expressing the phase relationships of air, water, and solids in a given volume of soil. 
 

Equipment: Drying oven, Balance, Moisture can, Gloves, Spatula. 

Test Procedure: 

(1) Record the moisture can and lid number. Determine and record the mass of an empty, clean, and dry moisture can with its lid (MC
(2) Place the moist soil in the moisture can and secure the lid. Determine and record the mass of the moisture can (now containing the moist soil) with the lid (MCMS). 
(3) Remove the lid and place the moisture can (containing the moist soil) in the drying oven that is set at 105 °C. Leave it in the oven overnight. 
(4) Remove the moisture can. Carefully but securely, replace the lid on the moisture can using gloves, and allow it to cool to room temperature. Determine and record the mass of the moisture can and lid (containing the dry soil) (MCDS). 
(5) Empty the moisture can and clean the can and lid.


Data Analysis:

(1) Determine the mass of soil solids.

          MS = MCDS  MSC

(2)Determine the mass of pore water.

          MW = MCMS MCDS

(3) Determine the water content.

          w = (MW /MS) x 100 

 

2. DENSITY (UNIT WEIGHT) DETERMINATIOM 

Purpose: This lab is performed to determine the in-place density of undisturbed soil obtained by pushing or drilling a thin-walled cylinder. The bulk density is the ratio of mass of moist soil to the volume of the soil sample, and the dry density is the ratio of the mass of the dry soil to the volume the soil sample. 
Standard Reference: ASTM D 2937-00 - Standard Test for Density of Soil in Place by the DriveCylinder Method 
 

Significance: This test is used to determine the in-place density of soils. This test can also be used to determine density of compacted soils used in the construction of structural fills, highway embankments, or earth dams. This method is not recommended for organic or friable soils. 
 

Equipment: Straightedge, Balance, Moisture can, Drying oven, Vernier caliper 


Test Procedure: 

(1)      Extrude the soil sample from the cylinder using the extruder. 
(2)      Cut a representative soil specimen from the extruded sample. 
(3)      Determine and record the length (L), diameter (D) and mass (Mt) of  the soil specimen. 
(4)      Determine and record the moisture content of the soil (w).  (See Experiment 1) 


Data Analysis: 

(1) Determine the moisture content as in Experiment 1
(2) Determine the volume of the soil sample

                V=(πD²L)/4    (cm³)  

(3) Calculate bulk density (ρt) of soil

            ρt  = Mt/V   (g/cm³) 

            or unit weight γt = ρtg

(4) Calculate dry density (ρd) of soil

            ρd = ρt /(1 + w)   (g/cm³) 

            or dry unit weight γd = ρdg

 

3. SPECIFIC GRAVITY DETERMINATION 

Purpose: This lab is performed to determine the specific gravity of soil by using a pycnometer. Specific gravity is the ratio of the mass of unit volume of soil at a stated temperature to the mass of the same volume of gas-free distilled water at a stated temperature. 
Standard Reference: ASTM D 854-00 - Standard Test for Specific Gravity of Soil Solids by Water Pycnometer. 

 

Significance: The specific gravity of a soil is used in the phase relationship of air, water, and solids in a given volume of the soil. 

 

Equipment: Pycnometer, Balance, Vacuum pump, Funnel, Spoon. 


Test Procedure: 
(1) Determine and record the weight of the empty clean and dry  pycnometer, WP
(2) Place 10g of a dry soil sample (passed through the sieve No.10) in the pycnometer. Determine and record the weight of the  pycnometer containing the dry soil, WPS
(3) Add distilled water to fill about half to three-fourth of the  pycnometer. Soak the sample for 10 minutes. 
(4) Apply a partial vacuum to the contents for 10 minutes, to remove  the entrapped air. 
(5) Stop the vacuum and carefully remove the vacuum line from  pycnometer. 
(6) Fill the pycnometer with distilled (water to the mark), clean the  exterior surface of the pycnometer with a clean, dry cloth. Determine the weight of the pycnometer and contents, WB
(7) Empty the pycnometer and clean it. Then fill it with distilled water  only (to the mark). Clean the exterior surface of the pycnometer  with a clean, dry cloth. Determine the weight of the pycnometer  and distilled water, WA
(8) Empty the pycnometer and clean it. 

Data Analysis: 

Calculate the specific gravity of the soil solids using the following formula: 

                       Specific Gravity,GS = W0/(W0 + (WA − WB ))


Where: W0 = weight of sample of oven-dry soil, g = WPS - WP 

            WA = weight of pycnometer filled with water 

            WB = weight of pycnometer filled with water and soil 

 

 


4. GRAIN SIZE ANALYSIS 

Purpose: This test is performed to determine the percentage of different grain sizes contained within a soil.  The mechanical or sieve analysis is performed to determine the distribution of the coarser, larger-sized particles, and the hydrometer method is used to determine the distribution of the finer particles. 
Standard Reference: ASTM D 422 - Standard Test Method for Particle-Size Analysis of Soils 

Significance: The distribution of different grain sizes affects the engineering properties of soil.  Grain size analysis provides the grain size distribution, and it is required in classifying the soil. 

 

Equipment: Balance, Set of sieves, Cleaning brush, Sieve shaker, Mixer (blender), 152H Hydrometer, Sedimentation cylinder, Control cylinder, Thermometer, Beaker, Timing device. 


 
Test Procedure: 

Sieve Analysis: 

(1) Write down the weight of each sieve as well as the bottom pan to beused in the analysis.
(2) Record the weight of the given dry soil sample.
(3) Make sure that all the sieves are clean, and assemble them in theascending order of sieve numbers (#4 sieve at top and #200 sieve atbottom). Place the pan below #200 sieve. Carefully pour the soilsample into the top sieve and place the cap over it.
(4) Place the sieve stack in the mechanical shaker and shake for 10minutes.
(5) Remove the stack