3 Compaction Problem Set SOLN

CIV E 381 Fall 2022 Topic 2: Compaction 1 | P a g e Question 1. A series of Standard Proctor compaction tests have been performed on a soil sample. The test results are presented in Table 1. Table 1. Results from Standard Proctor compaction tests. Data point number 1 2 3 4 5 Mass of compacted soil+mold (kg) 3.672 3.921 4.034 4.091 4.04 Mass of can (g) 20.11 21.24 19.81 20.3 20.99 Mass of can +wet soil (g) 240.85 227.03 263.45 267.01 240.29 Mass of can +dry soil (g) 231.32 212.65 241.14 238.81 209.33 The mass of the compaction mold was 2.031 kg. The moisture content tests were performed on small portions of the compacted soil samples. a) Compute dry density ( 𝜌 ? ) and water content ( ω ) for each data point and plot these results. b) Develop and plot curves for 𝑆 = 80% and 𝑆 = 100% using a specific gravity ( G s ) of 2.69 on the sample plot as part a. c) Using the data from parts a and b, draw the Proctor compaction curve and determine 𝜌 ?(???) and 𝑤 ???𝑖??? . (Reference: Assignment2, 2018) Solution : a) Compute dry density ( 𝜌 ? ) and water content ( ω ) for each data point and plot these results. Table 1. Results from Standard Proctor compaction tests. Data point number 1 2 3 4 5 Mass of compacted soil+mold (kg) 3.672 3.921 4.034 4.091 4.04 Mass of can (g) 20.11 21.24 19.81 20.3 20.99 Mass of can +wet soil (g) 240.85 227.03 263.45 267.01 240.29 Mass of can +dry soil (g) 231.32 212.65 241.14 238.81 209.33 Bulk density ( 𝝆 ) ( 𝒌?/𝒎 ? ) 17.38 20.02 21.22 21.82 21.28 Water content ( 𝒘 ) (%) 4.51 7.51 10.08 12.91 16.44 Dry density ( 𝝆 ? ) ( 𝒌?/𝒎 ? ) 16.63 18.62 19.28 19.33 18.28

CIV E 381 Fall 2022 Topic 2: Compaction 2 | P a g e b) Develop and plot curves for S = 80% and S =100% using a specific gravity ( G s ) of 2.69 on the sample plot as part a. Hint: Estimate the water content for the ranges of dry density values using the equation: 𝑤 = ( 𝐺 ? 𝜌 ? 𝜌 ? − 1) 𝑆 𝐺 ? Accordingly, the calculated values of water contents ( 𝑤 ) for S = 80% and S = 100% are tabulated in the table below: Dry density ( 𝝆 ? ) ( 𝒌?/𝒎 ? ) 16.33 18.28 18.92 18.97 17.94 𝒘 (%) at 𝑺 = ??% 18.36 13.22 11.76 11.65 14.03 𝒘 (%) at 𝑺 = ???% 22.95 16.52 14.71 14.56 17.54 c) Using the data from parts a and b, draw the Proctor compaction curve and determine 𝜌 ?(???) and 𝑤 ???𝑖??? . 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 0 2 4 6 8 10 12 14 16 18 Dry Density (kN/m3) Water Content (%) Standard Proctor Curve

CIV E 381 Fall 2022 Topic 2: Compaction 4 | P a g e Solution: a) Using a nuclear densometer, you have determined the field dry density is above the laboratory determined compaction curve (lab dry density vs moisture content). Explain what may contribute to this difference? The larger density than predicted on the standard proctor curve derived in the lab may be due to thinner lifts begin placed in-situ. Larger amounts of compaction effort will be delivered to a thinner layer of material, allowing increased density to occur than what was derived in the laboratory. The soil in tested in the laboratory may have a different particle size distribution than the soil actually compacted in the field. There may also be oversized particle in the field soils that were removed during the lab-testing phase. The larger particles would contribute to greater dry density in the field. b) Using the nuclear densometer, you have determined the field dry density is below the Relative Compaction specification and the field moisture content is greater than the acceptable range of moisture contents. What might you recommend as a corrective action to the contractor in order to meet the specifications? A correction measure to this lower density and increased moisture content would be to: • Allow the lift to dry out and then compact further. This will allow for increase in density and reduction of moisture content (moving backwards on the proctor curve). Could also be assisted by scarifying the compacted soil to increase the evaporative surface and allow more water to evaporate. • Use a sheepsfoot roller to further compact lift. Sheepsfoot rollers churn the soil that can reduce water contents while increasing density through increased compaction in clay soils. Question 3. You are the QA/QC engineer on a road construction project tasked with checking field compaction of a layer of soil. The laboratory compaction curve for the soil is shown in Figure 1 . Specifications call for the field compacted dry density to be at least 95% of the maximum lab value and within ± 2% of the optimum water content. When you conducted a sand cone test on the soil in the field, the volume of soil excavated was 1165 cm 3 . It weighed 2230 g wet and 1852 g dry. (Assume specific gravity ( 𝐺 ? ) = 2.7) a) What is the field compacted dry density? b) What is the field water content?

CIV E 381 Fall 2022 Topic 2: Compaction 5 | P a g e c) Does the soil layer meet the design specifications, why or why not? d) What is the degree of saturation of the field sample? e) What would be the moisture content if the soil layer became fully saturated at constant dry density? Note: this is an example of a past exam question. Figure 1. Laboratory compaction curve of the soil Solution: a) What is the field compacted dry density? Volume of soil excavated ( 𝑉 ) = 1165 cm 3 Wet mass of the soil ( ? ) = 2230 g Bulk density ( 𝜌 ) = 𝑀 𝑉 = 1.914 𝑔/?? Dry mass of the soil ( ? ? ) = 1852 g Water content ( 𝑤 ) = 𝑀− 𝑀 𝑑 𝑀 𝑑 = 20.41 % Dry density ( 𝝆 ? ) = 𝝆 ?+𝒘 = ?. ?? 𝒈/?? b) What is the field water content? Field water content ( 𝒘 ) = ?− ? ? ? ? = ??. ?? %

CIV E 381 Fall 2022 Topic 2: Compaction 7 | P a g e Question 4. A standard Proctor test was performed on a soil. Test results are recorded in Table 2. Table 2. Results from Standard Proctor compaction tests. Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 W (%) 7 10 12 15 18 𝜸 ? (kN/m3) 17 18 20 19 17.5 This soil is going to be used for the construction of an embankment with the design specification of 90% relative compaction and optimum moisture content. Two following sources are available in this project. Calculate the volume of soil that needs to be provided from each of these sources (without adding any more water) to construct one cubic meter of this embankment. Source A: 𝛾 =18 (kN/m3) w=20% Source B: 𝛾 =16.8 (kN/m3) w=5% 𝛾 ? ?𝑖?? = 𝛾 ? ??? × 90% = 20 × 0.9 = 18 𝑘? 𝑚 3 ⁄ ???? ????? → 𝜔 = 10% 𝛾 ? ?𝑖?? = 𝑤 ? ?𝑖?? 𝑉 ?𝑖?? → 18 = 𝑤 ? ?𝑖?? 1 → 𝑤 ? ?𝑖?? = 18 𝑘? 𝜔 = 𝑤 ? ?𝑖?? 𝑉 ? ?𝑖?? → 0.1 = 𝑤 ? ?𝑖?? 18 → 𝑤 ? ?𝑖?? = 1.8 𝑘? ?? ?𝑖?𝑒 ⇒ 𝑤 ? = 𝑤 ? ? + 𝑤 ? ? = 𝜔 ? 𝑤 ? ? + 𝜔 ? 𝑤 ? ? → 1.8 = 0.2𝑤 ? ? + 0.05𝑤 ? ? (𝐼𝐼) 𝑤 ? = 𝑤 ? ? + 𝑤 ? ? → 18 = 𝑤 ? ? + 𝑤 ? ? (𝐼) (𝐼) & (𝐼𝐼) → 𝑤 ? ? = ? 𝑘? 𝑤 ? ? = 12 𝑘? 𝑉 ? = 𝑤 ? ? 𝛾 ? ? → 𝛾 ? = 𝛾 ? 1 + 𝜔 ? = 18 40.2 = 15 → 𝑉 ? = 6 15 = 0.4 𝑚 3 𝑉 ? = 𝑤 ? ? 𝛾 ? ? → 𝛾 ? = 𝛾 ? 1 + 𝜔 ? = 16.8 1 + 0.05 = 16 → 𝑉 ? = 12 16 = 0.75 𝑚 3 So in order to construct 1 𝒎 ? of the embankment, we need ?. ? 𝒎 ? of source A and ?. ?? 𝒎 ? of source B.

CIV E 381 Fall 2022 Topic 2: Compaction 8 | P a g e Question 5. The void ratio ( e ) of a soil is 8%. 1200 m 3 of this soil was excavated and transported to a construction site for use in a compacted fill. How many cubic meters of compacted fill with a void ratio ( e ) of 5%, can be constructed using this amount of soil? 𝑉 ? = 1 ⇒ 𝑉 1 = 1 + 𝑒 1 𝑉 2 = 1 + 𝑒 2 𝑉 1 𝑉 2 = 1 + 𝑒 1 1 + 𝑒 2 ⟶ 𝑉 2 1200 = 1 + 0.05 1 + 0.08 ⇒ 𝑽 ? = ????. ? 𝒎 ?