University of Texas at Arlington Geotechnical Engineering Laboratory Test Procedure In-situ Density Determination by Sand Replacement Method Lecture Note 7 (Thursday 03-04-04) 1
Definitions, Objectives and Applications Figure 1. Methods of determining the unit weight of soils in the field 2
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Equipment Sand cone apparatus which consists of a one-gallon plastic bottle with a metal cone attached to it. One-Gallon plastic can with cap. Balance sensitive to 1 g. Base plate Tools for excavating a hole in the ground Clean, uniformly graded sand ranging from #20 to #30 sieve such as Ottawa Sand Proctor compaction mold without attached extension (used for calibration) Plastic air-tight bag for carrying wet excavated soil from field to the lab. Metal tray with a hole in the centre. Oven with temperature kept at about 105-110 o Test procedure 1- Measure the weight of Proctor mold + Base, W 1 (Go to row 1 of table) 2- Fig. (a). Pour the sand into the compaction mold Fig. (b). Level the surface (Do not disturb the mold as the sand may rearrange and get compacted) Fig. (c). Compaction mold filled with sand Fig. (d). Measure the weight of proctor mold+ base + Sand, W 2 (Go to row 2 of table) 4
(a) (b) (c) (d) 3- Measure the weight of plastic Gallon+Cone+Sand, W 3 (before use) (Go to row 5 of table) 4- (a). Close the valve attached to the cone (b).turn the cone and gallon upside down on the tray (c).open the valve, sand flows from the gallon to the cone, after the flow stops and take the gallon+cone from the tray close the valve (d). Measure the weight of plastic Gallon+Cone+Sand, W 4 (after use) (Go to row 6 of table) 5
(a) (b) (c) (d) 5- Weight of plastic Gallon+Cone+Sand, W 5 (before use) (Go to row 8 of table) Let s go to the Field. A little time out! 6
6- Go to the field where the soil's unit weight is to be measured, place the metal tray and fasten the 4 screws. 7- Dig up a 10 to 15 cm deep hole. 8- As you are digging the hole put the retrieved soil into the plastic bag in order that the soil does not lose moisture. All of the soil including the soft soil at the bottom of the hole is poured into the bag as well. 9- Having the valve closed turn the gallon+cone upside down and place the cone in the center hole of tray and open the valve so that sand flows down to the hole. 10- After flow of sand stops close the valve and pick the assembly up, the sand in the cone will be poured into the tray. This sand will be left there in the field. (Notice, Unlike this picture, the plastic bag should be kept closed while transferring to the lab to avoid moisture loss and consequently weight of the soil) 7
11- Measure the weight of plastic Gallon+Cone+Sand, W 6 (after use) (Go to row 9 of table) 12- Measure the weigh the evaporating dish, W 7 (Go to row 11 of table) 8
13- Measure the weigh the evaporating dish + wet soil from the field, W 8 (Go to row 12 of table) 14- Put the evaporating dish + wet soil in the oven and after 24hrs weigh it again, W 9 (Go to row 13 of table). In the sample test we did for you W 9 turned out to be 2.251 Kg. 15- Having the information you got so far in the table, Calculations can be carried out easily. Do the calculations, fill out the table and include the answers to the following questions in your reports. Questions for further study; 1. Suppose the soil of test # 6 Standard and Modified Compaction tests was taken from the exact same point in the field where you performed Sand Cone test, what will the Compaction Ratio in this test be? Can compaction ratio ever be greater than 1 or 100%? Why? 2. Name any two other methods for obtaining the In-situ density of soils? 9
Sample table Test Steps Quantity Obtaining the unit weight of the sand used 1. Weight of Proctor mold + Base, W 1 4.178 kg 2. Weight of proctor mold + Base + Sand, W 2 5.609 kg 3. Volume of the mold, V 1 0.00095 m 3 4. Dry unit weight, γ d (sand) = (W 2 - W 1 ) / V 1 1506 kg/m 3 Calibration cone 5. Weight of plastic Gallon+Cone+Sand (before use), W 3 5.466 kg 6. Weight of plastic Gallon+Cone+Sand (after use), W 4 3.755 kg 7. Weight of the sand to fill the cone, W c = W 3 - W 4 1.711 kg Results from field tests 8. Weight of plastic Gallon+Cone+Sand (before use), W 5 7.387 kg 9. Weight of plastic Gallon+Cone+Sand (after use), W 6 3.919 kg 10. Volume of hole, V 2 = (W 5 -W 6 -W c )/ γ d (sand) 0.00117m 3 11.Weight of evaporating dish, W 7 0.507 kg 12. Weight of evaporating dish + wet soil from the field, W 8 2.334 kg 13. Weight of evaporating dish + dry soil after 24hrs, W 9 2.251 kg 14. Moist unit weight of the soil in the field, γ t (in-situ soil) = (W 8 - W 7 ) / V 2 1561 kg/m 3 15. Water content in the field, w(%)= (W 8 - W 9 ) / (W9- W7)*100 4.76% 16. Dry unit weight in the field, γ d (in-situ soil) = [γ t (Row 14) ] / [1+ w(%) / 100] 1490 kg/m 3 Conversion factors (Unit weight): 1000 kg/m 3 = 9.81 KN/m 3 = 62.4 lb/ft 3 10
Use this table for your reports Test Steps Obtaining the unit weight of the sand used Quantity 1. Weight of Proctor mold, W 1 2. Weight of proctor mold + Sand, W 2 3. Volume of the mold, V 1 0.00095 m 3 4. Dry unit weight, γ d (sand) = (W 2 - W 1 ) / V 1 Calibration cone 5. Weight of plastic Gallon+Cone+Sand (before use), W 3 6. Weight of plastic Gallon+Cone+Sand (after use), W 4 7. Weight of the sand to fill the cone, W c = W 3 - W 4 Results from field tests 8. Weight of plastic Gallon+Cone+Sand (before use), W 5 9. Weight of plastic Gallon+Cone+Sand (after use), W 6 10. Volume of hole, V 2 = (W 5 -W 6 -W c )/ γ d (sand) 11.Weight of evaporating dish, W 7 12. Weight of evaporating dish + wet soil from the field, W 8 13. Weight of evaporating dish + dry soil after 24hrs, W 9 14. Moist unit weight of the soil in the field, γ t (in-situ soil) = (W 8 - W 7 ) / V 2 15. Water content in the field, w(%)= (W 8 - W 9 ) / (W9- W7)*100 16. Dry unit weight in the field, γ d (in-situ soil) = [γ t (Row 14) ] / [1+ w(%) / 100] Conversion factors (Unit weight): 1000 kg/m 3 = 9.81 KN/m 3 = 62.4 lb/ft 3 11