Standard proctor test
- 1. University of Sulaimani College of Engineering Civil Engineering Department (Soil Mechanics Lab) Name of the Test: Standard Proctor Compaction Test Test No. : Students Name: 1- Raz Azad Abdullah 2- Zhyar Abu-Bakr 3- Rawezh Saady Group & Sub-Group: A1-A6 Date of the Test:
- 2. 1 Introduction: Compaction is a method of mechanically increasing the density of soil, and it’s especially valuable in construction applications. If this process is not performed properly, soil settlement can occur, resulting in unnecessary maintenance costs or failure of the pavement or structure. For construction of highways, airports, and other structures, it is often necessary to compact soil to improve its strength. Proctor (1933) developed a laboratory compaction test procedure to determine the maximum dry unit weight of compaction of soils, which can be used for specification of field compaction. This test is referred to as the Standard Proctor Compaction Test. It is based on compaction of soil fraction passing No. 4 U.S. sieve. Purpose: The testing first determines the maximum density achievable for the soil and uses it as a reference for field testing. It also is effective for testing the effects of moisture on the soil's density. There are a variety of different benefits to soil compaction, including: prevention of soil settlement and frost damage, increased ground stability, reduced hydraulic conductivity and mitigating undesirable settlement of structures, such as paved roads, foundations and piping.
- 3. 2 Equipment: Compaction mold No.4 U.S. sieve Standard Proctor hammer (5.5lb)(24.5N) Balance sensitive up to 0.01 lb Balance sensitive up to 0.1 g Large flat pan Jack Steel straight edge Moisture cans Drying oven Plastic squeeze bottle with water
- 4. 3 Procedure: 1. Obtain about 10 lb (4.5 kg) of air-dry soil on which the compaction test is to be conducted. Break all the soil lumps. 2. Sieve the soil on a No.4 U.S. sieve. Collect all of the minus-4 material in a large pan. This should be about 6lb (2.7 kg) or more. 3. Add enough water to the minus-4 material and mix it in thoroughly to bring the moisture content up to about ~. 4. Determine the weight of the Proctor mold + base plate (not the extension), WI' (lb). 5. Now attach the extension to the top of the mold. 6. 'Pour the moist soil into the mold in three equal layers. Each layer should be compacted uniformly by the standard Proctor hammer 25 times before the next layer of loose soil is poured into the mold. 7. Remove the top attachment from the mold. Be careful not to break off any of the compacted soil inside the mold while removing the top attachment. 8. Using a straight edge, trim the excess soil above the mold (Fig. 12-3). Now the top of the compacted soil will be even with the top of the mold. 9. Determine the weight of the mold + base plate + compacted moist soil in the mold, W2 (lb). 10. Remove the base plate from the mold. Using a jack, extrude the compacted soil cylinder from the mold. 11. Take a weight of can (g). 12. From the moist soil extruded in Step 10, collect a moisture sample in the moisture can (Step II) and determine the mass of the can + moist soil, (g). 13. Place the moisture can with the moist soil in the oven to dry to a constant weight. 14. Break the rest of the compacted soil (to No.4 size) by hand and mix it with the leftover moist soil in the pan. Add more water and mix it to raise the moisture content by about 2%.
- 5. 4 Calculation: γ = moist unit weight = w2−w1 volume of mold γdry=Dry unit weight = γ 1+ w% 100 %(w)= weight of moist dry weight of soil × 100 = w(can+wet soil)−w(can+dry soil) w(can+dry soil)−w(can) × 100 γ zero air void = γ water w% 100 + 1 Gs Where:- w1=weight of mold+ base plate. w2=weight of mold+ base plate+ compacted moist soil in the mold. w%= moisture content (M.C). Volume of mold = π D2 4 × H = π 9.982 4 × 12.75 = 997.381 cm 1) Can #35: (γ) Moist unit weight = 6412−4626 997.381 = 1.790 g/cm3 𝑀. 𝐶 = 116−113.5 113.5−74.08 × 100 = 6.342% 𝛾𝑑𝑟𝑦 = 1.790 1+ 6.342 100 = 1.528 g/cm3 At same M.C: γ zero air void (γ zav) = 1 6.342 100 + 1 2.7 = 2.305 g/cm3 2) Can #31: (γ) Moist unit weight = 6558−4626 997.381 = 1.937g/cm3 M. C = 128−122.26 122.26−72.99 × 100 = 11.650%
- 6. 5 γdry = 1.937 1+ 11.650 100 = 1.734g/cm3 At same M.C: γ zero air void (γ zav) = 1 11.650 100 + 1 2.7 = 2.054g/cm3 3) Can#14: (γ) Moist unit weight = 6656−4626 997.381 =2.035g/cm3 M. C = 126−117.97 117.97−76.45 × 100 = 19.34% γdry = 2.034 1+ 19.34 100 = 1.704g/cm3 At same M.C: γ zero air void (γ zav) = 1 19.340 100 + 1 2.7 = 1.773 g/cm3 4) Can#17: (γ) Moist unit weight = 6600−4626 997.381 = 1.979g/cm3 M. C = 114−105.63 105.63−74.91 × 100 = 27.246% γdry = 1.979 1+ 27.246 100 = 1.555 g/cm3 At same M.C: γ zero air void (γ zav) = 1 27.246 100 + 1 2.7 = 1.555 g/cm3
- 7. 6 Table of Results: O.M.C=13.7% (from the graph) Maximum dry unit weight = 1.74 g/cm3 (from the graph) Test No. Wt. of Mold (g) Wt.of (wet soil+ mold)g Wet unit weight (g/cm3) 1 4626 6412 1.790 2 4626 6558 1.937 3 4626 6656 2.035 4 4626 6600 1.979 Can No. Wt. Of container(g) Wt. Of (wet soil+cont.)(g) Wt. Of (Dry soil+cont.)(g) W.C (%) Dry Unit weight (g/cm3) Max.theorotical dry unit weight (g/cm3) γ (zav.) (g/cm3) 35 74.08 116 113.5 6.341 1.681 2.232 2.305 31 72.99 128 122.26 11.65 1.734 1.995 2.054 14 76.45 126 117.97 19.34 1.704 1.73 1.773 17 74.91 114 105.63 27.246 1.554 1.523 1.555
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- 9. 8 Discussion& Conclusion: The Proctor compaction test is a laboratory method of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density., compaction of soil increases the shear strength of the soil, increase the bearing capacity, also reduces erosion and it will give the soil more stability, and reduces voids between the particles so that it makes the soil more difficult for water to flow through soil. In this soil sample, from the graph the soil has a maximum dry unit weight of (1.74 g/c𝑚3 ) with the optimum moisture content of (13.7%), but after calculation of zero-air-void curve and plotting on the graph we saw that the last point of the real soil curve intersects with the zero-air-void curve, which it means the soil sample became void less and goes beyond the theoretical curve which is not acceptable. Many errors could have occurred while performing the lab test. The most prominent error is human error. Someone could have miss counted while using the hammer or there could have been a miss calculation in the computation of the water needed for the desired water content. Another source of error could be from a hole in the tube used to mix the water and soil. The amount of soil in the mold may not have been exactly (997.381 cm3) either, throwing off the calculations. Compacting at water contents higher than the optimum water content results in a relatively dispersed soil structure that is weaker, more ductile, less porous, softer, more susceptible to shrinking, and less susceptible to swelling than soil compacted dry of optimum to the same density. The soil compacted lower than the optimum water content typically results in a flocculated soil structure (random particle orientations) that has the opposite characteristics of the soil compacted wet of the optimum water content to the same density In conclusion, the test has failed and the test should be done again using a correct balance with a sensitivity of (0.1g) or better, and more accuracy while mixing and compacting the soil for more accurate and dependable results.