Lab Report #3: Standard Proctor Test for Soils Abstract Soil Compaction is the process in which stress is applied to a soil which causes densification as the voids are filled with solids. This plays a vital part in construction for soils are mainly used as supports for a lot of infrastructures. Compaction is greatly affected by soil type, moisture content, and compaction effort and is usually test using ASTM D698. In this report it is concluded that the soil sample reaches its highest compact state when the dry unit weight is as its maximum value of 16kN/m3 and 15% moisture content. Submitted by: Nur-Ranji Jajurie Group Mates: Prince Charlie Intal Vanessa Gale Marie Natividad Carl Joshua Rebutiaco Xerxes Tupag Date Performed: April 11, 2016 Date Submitted: April 29, 2016 1 I. Objectives To determine the optimal water content at which the soil sample can reach its maximum dry density in accordance to ASTM D698: 12 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort To discuss the relevance of the results of the experiment in Civil Engineering practices and to compare it with other soils that exhibit different compaction property II. Materials 4-in. Mold Assembly Manual Rammer Balance Drying Oven Sieve no. 4 Containers and Mixing Apparatus 2 III. Methodology 3 4 IV. Data and Results Table 1 shows the recorded mass and dimensions of the cylindrical mold that was used for the computation for its volume as shown in Equation 1: [Equation 1] , Measurements on the Mold Mass Diameter Height 3.5145 kg 0.1016 m 0.1164 m 3 Volume 0.000943692 m Table 1: Recorded masses and dimension of the mold used The initial mass of the air dried soil sample that was used in the experiment was 5.002 kg in which 5% (or 0.25 kg) moisture was added and was used in the first trial. For each of the succeeding trials, 2% (or 0.1 kg) moisture was added. Table 2 presents the data on the masses of the mold after the addition and compaction of the soil as indicated in Section III. Note that the mass of the empty mold is 3.5145 kg. Trial 1 2 3 4 5 6 7 Mass of Mold + Soil, kg Mass of Soil, kg 5.0945 5.1315 5.2215 5.274 5.327 5.314 5.293 1.58 1.617 1.707 1.7595 1.8125 1.7995 1.7785 Table 2: Mass of the Soil Sample inside the mold in each trial The moisture content of the soil sample in each of the trials is determined using Equation 2: , In which is the moisture content of the compacted soil sample in percent, mass in kg, and [Equation 2] is its wet is its mass after drying in kg. Table 3 presents the data used in order to determine the moisture content of each trial using Equation 2. 5 Trial 1 2 3 4 5 6 7 Mass of Container, kg 0.015 0.0115 0.012 0.012 0.0065 0.006 0.006 Mass of Container + Soil Sample (wet), kg 0.1205 0.055 0.1495 0.1595 0.1135 0.0615 0.0715 Mass of Container + Soil Sample (dry), kg Mass of Soil Sample (wet), kg 0.1055 0.0435 0.1375 0.1475 0.107 0.0555 0.0655 0.111 0.0505 0.1325 0.1395 0.097 0.0515 0.0582 Mass of Soil Sample (dry), kg Moisture Content, % 0.096 0.039 0.1205 0.1275 0.0905 0.0455 0.0522 9.0047 10.3448 12.3636 13.5593 15.4206 18.018 20.3053 Table 3:.Moisture content of the compacted soil in each trial Next is to present the moist (total) and dry density, and dry unit weight of the compacted soil in each trial. First to calculate the total density, Equation 3 is used: [Equation 3] , Where is the moist density of the compacted specimen in kg/m3, is the mass of the moist compacted soil in kg, and V is the volume of the mold which is equal to 0.000943692 m3. Using trial 1 as a sample computation: ⁄ Moist density of all the trials is then presented in Table 4. Trial 1 2 3 4 5 6 7 Mass of Soil (kg) 1.58 1.617 1.707 1.7595 1.8125 1.7995 1.7785 Moist Density (kg/m3) 1674.275 1713.483 1808.853 1864.485 1920.648 1906.872 1884.619 Table 4: Moist Density of the Compacted Soils The dry density of the compacted soil sample can be computed using Equation 4: , In which is the dry density of the compacted soils in in kg/m3, density of the compacted soil in kg/m3 shown in Table 4, and [Equation 4] is the moist is the moisture content of the soil in percent as shown in Table 3. Using trial 1 for sample computation we then have: 6 ⁄ Dry density of all the trials is presented in Table 5: Trial Moist Density (kg/m3) Moisture Content (%) Dry Density (kg/m3) 1 2 3 4 5 6 7 1674.275 1713.483 1808.853 1864.485 1920.648 1906.872 1884.619 9.004739 10.34483 12.36364 13.55932 15.42056 18.01802 20.30534 1535.965 1552.844 1609.821 1641.86 1664.043 1615.747 1566.53 Table 5: Dry Density of the Compacted Soils Finally, the dry unit weight of the compacted soil sample can now be acquired using Equation 5: , Where is the dry unit weight of the compacted specimen in kN/m3, and [Equation 5] is the dry density in kg/m3, computing the dry unit weight of trial 1: Table 6 contains all the computed values for the computed dry unit weight of all the trials. Trial Dry Density (kg/m3) Dry unit weight (kN/m3) 1 2 3 4 5 6 7 1535.965 1552.844 1609.821 1641.86 1664.043 1615.747 1566.53 15.0626 15.22812 15.78687 16.10107 16.3186 15.84498 15.36233 Table 6: Dry Unit Weight of the Compacted Soil The compaction curve is then generated by plotting the dry unit weight versus the moisture content graph as shown in Table 7. 7 Trial Moisture Content (%) Dry unit weight (kN/m3) 1 2 3 4 5 6 7 9.004739 10.34483 12.36364 13.55932 15.42056 18.01802 20.30534 15.0626 15.22812 15.78687 16.10107 16.3186 15.84498 15.36233 Table 7: Points used in the Compaction Curve 16.4 Dry Unit Weigth (kN/m3) 16.2 16 15.8 15.6 15.4 15.2 15 14.8 0 5 10 15 20 25 Moisture Content (%) Graph 1: Compaction Curve of the Soil Sample The optimum water content and the maximum dry unit weight of the soil sample are acquired through analyzing the curve and getting the coordinate values of the maximum point, which is: Optimum Moisture Content: 15% Maximum Dry Unit Weight: 16.36 kN/m3 V. Analysis and Discussion The main purpose of compacting soils is to reduce subsequent settlement under working loads. Compaction also increases the shear strength of the soil, reduces voids ratio making it more difficult for water to flow through soil and prevent the buildup of large water pressures that cause soil to liquefy during earthquakes. Thus it is essential to identify the maximum unit weight of the soil in order to maximize the usages mentioned above through identifying the quantities or qualities of the factors that 8 affect compaction such as water content, the type of soil being compacted, and the amount of compactive energy that was used. To assess the degree of compaction, the dry unit weight is greatly attributed because we are more interested on the weight of solid soil particles in a given volume than the amount of solid, air, and water in a volume (in which is the bulk density). In order to analyze the effect of dry unit weight in the compaction let’s analyze Equation 6. [Equation 8] Where is the dry unit weight, gravity of the soil solids, and is the unit weight of water, is the specific is the ratio of voids. Rearranging this equation, we yield: [Equation 7] Since and are both constant it can then be inferred that the dry unit weight and void ratio are inversely proportional to each other, such that the higher the dry unit weight and lesser the voids which means that it is more compacted. Moisture content acts as the driving force in controlling the dry unit density such that if water is added to a soil (at low moisture content) it becomes easier for the particles to move past one another during the application of the compacting forces. As the soil compacts the voids are reduced and this causes the dry unit weight to increase. Initially then, as the moisture content increases so does the dry unit weight as what can be seen in Graph 1. However, the increase cannot occur indefinitely because the soil state approaches its saturation point which indicates that the voids are filled with water and prohibits the solids to compact with each other. Varying compactive effort also affects the compactibility of the soil such that increasing it causes greater dry unit weights to be achieved. This is because of the solid particles being forced to interlock with one another. Although that it should be noted that for moisture contents greater than the optimum the use of heavier compaction machinery will have only a small effect on increasing dry unit weights. Thus, it is really important especially in construction sites to be able to control the moisture content of the soil at its optimal value in order to ensure that the dry unit weight is at its greatest. By analyzing again the Graph 1, we could infer that it is best to achieve 15% moisture content in order to attain the highest compaction of soil possible. 9 Lastly, soil types affect compaction of the soil because of its particle sizes and characteristics. Table 8 presents the typical values of maximum dry unit weight and optimum moisture content for some common types of soils. Typical Values Type of Soil Well graded sand SW Sandy clay SC Poorly graded sand SP Low plasticity clay CL Non plastic silt ML High plasticity clay CH Dry Unit Weight (kN/m3) Optimum Moisture Content (%) 22 19 18 18 17 15 7 12 15 15 17 25 Table 8: Typical Values of Dry unit Weight and Moisture Content for Common Soils Although Table 8 only presents only typical values which must not be used in design because soils exhibits great variability, we can still compare the computed values of maximum dry unit weight of 16.36 kN/m3, and optimum moisture content of 15% to CL and ML type of soils as shown in Table 8. Looking back on the previous laboratory report, the soil sample was described to be clay with low plasticity which gives reliability to the results of the experiment and some typical values. VI. Conclusions and Recommendations After performing ASTM D698, it has been concluded that the maximum dry unit weight of 16.36 kN/m3 can be achieved using 15% moisture content and a standard effort of 600 kN-m/m3. The values attained can be of great use in construction using the test sample if maximum compaction is wanted in order to support the maximum load possible. There was no way in order to compute the error of the experiment and thus it is recommended to perform the experiment more than once in order to provide more precise and accurate data. VII. References 1. American Society for Testing and Materials. ASTM D698: 12 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12 400 ft-lbf/ft3 (600 kN-m/m3)). E-book. 2. Das, Braja M. Principles of Geotechnical Engineering. Published on 2002. Ebook. 10 3. Intelligentcompaction.com. Fundamentals of Compaction . retrieved www.intelligentcompaction.com/downloads/IC_RelatedDocs/SoilCmpct_Fundam entals%20of%20Soil%20Compaction.pdf on April 27, 2016. 4. McCarthy, David F. Essentials of Soil Mechanics and Foundations. E-book. 11