Specific gravity of soil solids

Jordan University of Science and Technology Civil Engineering Department Geotechnical lab CE 463 EXP. # 1 Specific gravity of soil solids Name: reema zamil ID: 106296 Date: 2/6/2018 Introduction: Specific gravity of soil generally refer to the specific gravity of mineral (grains (soil solids)). We calculate the specific gravity by compute the ratio of the weight of soil to unit weight of an equal volume of water. And this water was distilled water (no voids). From equation the specific gravity in unit-less and we calculate it to convert the weight to volume (weight-volume relationship). Abstract: We want to calculate the specific gravity for sand which passes sieve #4 (4.75 mm) and granular, non-cohesive soil by means of a water pycnometer. Before that we know the specific gravity for sand is between (2.63-2.67), Soil solids for these test methods do not include solids which can be altered by these methods, contaminated with a substance that prohibits the use of these methods, or are highly organic soil solids, such as fibrous matter which floats in water. The specific gravity of a soil solids is used in calculating the phase relationships of soils, such as void ratio and degree of saturation, and used for used to calculate the density of the soil solids. This is done by multiplying its specific gravity by the density of water (at proper temperature). Objectives: To calculate the specific gravity of sand, and to know the effect of temperature and vids of specific gravity. Equipment: 1- Volumetric flask (500ml) 2- Thermometer 3- Balance sensitive up to 0.1 g 4- Distilled water 5- Vacuum pump or aspiration 6- Spatula 7- Plastic squeeze bottle 8- Drying oven. Procedure: 1. Carefully fill the flask with de-aired distilled water to the 500 ml mark. 2. Determine the weight of the flask and the water filled to the 500 ml mark (W1). 3. Insert the thermometer into the flask with water and determine the temperature of the water. 4. Weight approximately 100 grams of soil (sand) (W3). 5. Transfer the sand into the volumetric flask. 6. Add distilled water to the volumetric flask containing the soil to make it about two-thirds full. 7. Remove the air from the soil-water mixture by applying vacuum by a vacuum pump until the entrapped air is out (about 10 min.). 8. Add de-aired distilled water to the volumetric flask until the bottom of the meniscus touches the 500 ml mark. Also dry the outside of the flask and the inside of the neck above the meniscus. 9. Determine the combined weight of the bottle plus soil plus water (W2). Results and calculation: Gs=100/ ((100+677.51)-738.9) = 2.59 A @ 18°C= 1.004 Gs (at 20°C) =Gs (at T1°C) *A =2.59*1.004 = 2.6 Test no. 1 Weight of flask + water filled to mark (w1 (g)). 677.51g Weight of flask +soil +water filled to mark (w2 (g)). 738.9g Weight of dry sand.(w3 (g)) 100g Temperature of test T1 (°C). 18 (°C) Gs @18 (°C) 2.59 A 1.004 Gs (at 20°C) 2.6 Discussion: As shown in the results and calculation, the specific gravity of the soil is slightly affected by temperature so we had to multiply the result we get at certain temperature with a correction factor to get the accurate specific gravity at room temperature. However, the effect of temperature is minimal and that can be noticed from the correction factor (A) which is very close to 1.004 Since we know the range of specific gravity for sand we can tell that the test results are accepted and the values are accurate since we get a value of Gs = 2.59 and the typical values of Gs for sand ranges from 2.63 to 2.67. In this test we used sand which is considered a non-cohesive soil, however if we used a cohesive soil we should add de-aired distilled water to the soil and mix it to the form of a smooth paste. Keep it soaked for about one-half to one hour in the evaporating dish. This process is to be done before transferring the soil (soil paste in this case) to the volumetric flask. Although our value is within the typical range of values, errors may occur in the test, and they can be from: * Entrapped air may be not fully removed. This can largely affect the results. * Human errors in taking readings and weighing the test specimens. At least two to three specific gravity tests should be conducted. For correct results, these values should not vary by more than 2 to 3%. Conclusion: * Specific gravity of soils is affected by temperature at which the test is being held. * Specific gravity of soils is largely affected by the entrapped air in the test specimen. * Most of errors in the results are due to entrapped air which is not removed. * The benefit of specific gravity is to find the relationship between weight and volume. * The range of specific gravity for sand is (2.63-2.67) References: * Soil Mechanics Laboratory Manual. 4th Ed. Braja M.Das * Lab notes. * ASTM.