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BASIC SOIL MECHANICS PRACTICAL REPORTMODULE 3HYDROMETER ANALYSIS

INTERNATIONAL PROGRAM GROUP 1Asti Diar Safitri - 1206292414Christopher Kevinly - 1206223846Wednesson Lawijaya - 1206230593

Date of Practicum: 2/11/2013Practicum Assistant: Felix CahyoDate of Approval: Score:Assistants Signature:

SOIL TESTING LABORATORYCIVIL ENGINEERING DEPARTMENTFACULTY OF ENGINEERINGUNIVERSITY OF INDONESIADEPOK 2013

MODULE 3HYDROMETER ANALYSIS

3.1. INTRODUCTIONObjectivesDetermining the distribution of soil grains with diameter of less than 0.074 mm (sieve no. 200 ASTM) using hydrometer method.Materials and Apparatus Hydrometer (type 152 H) Hydrometer jar (1080 ml) Measuring glass Dispersion liquid 4% (water glass) Sample of soil passed through sieve no. 4 ASTM, each has weight of 50 gram for 3 samples Mixer Oven Thermometer (Celsius) Belimbing glass Sieve no. 200 ASTM Scales with a precision of 0.01 gram

Theory and FormulasThis practicum is based on the relation between the velocity of a falling grain in the liquid, diameter of grain, specific gravity of grain, specific gravity of liquid, and concentration of liquid. This relation can be elaborated by Stokes Law as stated below:

where: = velocity of falling grain (cm/s)= specific gravity of grain (gr/) = specific gravity of liquid (gr/) = concentration of liquid (dyne.s/) = diameter of grain (cm)

Limitations of Stokes Lawa. This law is only applied if: 0.0002 mm < D < 0.2 mmb. Grain which has diameter of more than 0.2 mm will cause turbulence in liquid, while grain which has diameter of more than 0.0002 mm tends to do Browns movement due to attraction and repulsion forces between each particles.c. Amount of samples used must be less than amount of grains used (). This is done in order to prevent interference during precipitation. In accordance with Bowles, hydrometer type 152 H is calibrated for suspension of liquid, which contains 60 gram in 1000 ml of water.d. Soil grains are assumed to be round-shaped, although this assumption is not 100% correct. Soil used must be expended with these dispersion materials: For base soil, use sodium metaphosphate (NaPO3) with trade name Calgon For acid soil, use sodium silicate (Na2SiO3) with trade name Water Glass

Velocity of grain falling:(3.2)(3.3)

where: = velocity of grain falling= height of grain falling = time= volume of bulb hydrometer = cross-sectional area of hydrometer = shown at table 3.6 (attachment) according to hydrometer type 152 H reading and corrected by meniscusCorrection:Rc = Ractual Zero Correction + CT(3.4)

where:CT = correction in respect to temperature shown at Table 3.6 (attachment)For Gs = 2.65 : (3.5)

while for Gs 2.65 :(3.6)

where: (3.7)

or value of a can be obtained from table 6.2 (attachment)To make calculations easier:

(3.8)explanation: Unit in L (cm) and t (minute) Coefficient K is shown at table 3.7 (attachment)* all attached tables (3.4-3.7) are from Engineering Properties of Soil and Their MeasurementAfter % finer and D, which are attached to each other, have been calculated, the graph of grain distribution is obtained. From this graph, D10, D30, and D60 can be obtained as well by using procedures below:D10 = diameter corresponding to 10% of grain passing (%finer = 10%)D30 = diameter corresponding to 30% of grain passing (%finer = 30%)D60 = diameter corresponding to 60% of grain passing (%finer = 60%)So that the coefficient of uniformity (Cu) can be obtained using formula as stated below: (3.9)

Definition of coefficient of uniformity (Cu) for several values: Cu = 1, soil only has one size of grain 2 < Cu < 3, soil has bad gradation Cu > 15, soil has good gradation

Moreover, coefficient of curvature (Cc) can be obtained using formula as stated below:(3.10)

If 1 < Cc < 3, it can be assumed that a certain range for soil has good gradation.

3.2. PRACTICUM3.2.1. Practicum Preparation1. Preparing 50 gram of oven-dried soil 2. Weighing 40 gram water glass as dispersion material and adding water glass to hydrometer jar, then mixing it with distilled water until it reaches 1000 ml and homogenous. This mixture is called dispersion liquid.3. Pouring 125 ml of dispersion liquid into a belimbing glass, which has been filled with 50 gram of soil and leaving it for about 18 hours.4. Preparing a cylindrical tube (1000 ml), then adding 125 ml of dispersion liquid and 1000 ml of distilled water into cylindrical tube, this tube has a function as control tube.

3.3.2. Practicum Preparation1. Checking meniscus and zero correction at hydrometer type 152 H by putting it into control tube and recording the reading.2. Adding soil mixture and dispersion liquid which have been soaked for about 18 hours into mixer cup gently by using pipet so that all the small grains go into mixer cup. Afterwards, adding some distilled water by using piper until it reaches approximately 2/3 of mixer cup. Next, mixing it for about 10 minutes by using mixer.3. Moving mixture from mixer cup into hydrometer jar by using pipet so that all soil grains flow into hydrometer jar. After that, adding distilled water until it reaches 1000 ml.4. Closing the tube with rubber cover and shaking it horizontally for about one minute until the mixture of water, soil grains, and water glass is homogenous.

Figure 3.1. Process of mixing hydrometer jar5. After tube being put, putting hydrometer type 152 H immediately and gently as shown at figure 3.2. Next, waiting for hydrometer to be stable to do scale reading. Reading hydrometer (R1) exactly at minute 1, and then at minute 2 , the reading is being conducted again (R2). Afterwards, lifting up the hydrometer again.

Figure 3.2. How to put hydrometer into hydrometer jar properly

6. At minute 3, putting hydrometer back and record the reading again (R3) likewise for minute 4.7. Doing the hydrometer reading for minute 8, 15, 30, 60, 120, 240, 480, 960, and 1440.8. At each hydrometer reading, temperature reading is also being conducted.9. After the sample has been recorded, pouring liquid of each sample into sieve no. 200 ASTM (do not mix it together). Soil grains, which are retained at this sieve, are used for sieve analysis practicum.

Comparison with ASTMIn the ASTM procedure, hydrometer reading is not conducted at minute 120, 240, 480, and 960.

3.3 PRACTICUM RESULT3.3.1. Practicum Result DataZero correction: 0.5Meniscus correction: 0Table 3.1 Practicum Data ResultDateTime of ReadingElapsed Time (min)Temperature ()Actual Hyd. Reading

Oct 209.00128.720

Oct 209.02228.719

Oct 209.03328.718

Oct 209.04428.817

Oct 209.08828.816

Oct 209.151528.814.5

Oct 209.303029.113

Oct 210.006029.512

Oct 211.001203011

Oct 213.0024031.58

Oct 217.0048029.57.5

Oct 301.0096029.57

Oct 401.00144029.56.5

3.3.2. Data ProcessingFrom specific gravity practicum, Gs average= 2.637From table 3.4, a= 1.0026Zero correction= 0.5Meniscus correction= 0Finding the value of a at Gs= 2.637 by using interpolationGs= 2.60, a= 1.01Gs= 2.65, a= 1.00

Example of calculation from minute 1 reading:T= 28.7Finding the value of CT for temperature of 28.7 using by interpolation (from table 3.5)T= 28, CT = +2.50T= 29, CT = +3.05

Ra= 20Rc= Ra zero correction+ CT= 20 0.5 + 2.885= 22.385

R= Ra + meniscus correction= 20 + 0 = 20At R= 20 the value of L= 13.0 (from table 3.6)Finding the value of k at T= 28 by using interpolationGs= 2.60, k= 0.01264Gs= 2.65, k= 0.01244Gs practicum= 2.637

Finding the value of k at T= 29 by using interpolationGs= 2.60, k= 0.01249Gs= 2.65, k= 0.01230Gs practicum= 2.637

Interpolating the value of k at T= 28.7At T= 28, k= At T= 29, k=

Finding the value of D mmwhere:Ra= actual hydrometer readingRc= correction hydrometer readingR= hydrometerCT= temperature correction factorL= values of effective deptht= elapsed time

Table 3.2 Calculation ResultsMinTemp ()RaRc%finerRL L/tkD (mm)

128.72022.38544.8862013.013

228.71921.38542.8811913.26.60.03183

328.71820.38540.8761813.34.4330.02609

428.81719.4438.9811713.53.3750.01135120.02085

828.81618.4436.9751613.71.71250.01135120.01485

1528.814.516.9433.96814.513.90.9260.01135120.01092

3029.11315.62531.3311314.20.4730.01233640.00848

6029.51214.92529.9271214.30.2380.01228440.00599

120301114.328.671114.50.1200.01221940.00423

24031.5812.42524.914815.00.06250.012619750.00315

48029.57.510.42520.9047.515.10.03140.01228440.00217

96029.579.92519.901715.20.01580.01228440.00154

144029.56.59.42518.8996.515.350.01060.01228440.00126

3.4 ANALYSIS3.4.1. Analysis of ProcedureThis practicum is conducted to determine the distribution of soil grains with diameter of less than 0.074 mm (sieve no. 200 ASTM) using hydrometer method. A day before practicum, some preparations are done. In preparation, students prepare 50 grams of sample of soil. Afterwards, students put the sample into the oven until its perfectly dry so that the weight of the sample is consistent. Next, the dispersion liquid is prepared. This liquid consists of 40 grams of water glass and 1000 ml of water, which are mixed altogether until the mixture is homogeny. This dispersion liquid has a function to create colloid between water glass and some dirt in the soil grains. This colloid makes the dirt doesnt precipitate with soil. Once the dispersion liquid is ready, the next step is pouring 125 ml of dispersion liquid into a glass, which is filled with 50 gram of soil. Later on, this sample is kept for approximately 18 hours. Besides preparing this sample of soil, students also make a control tube. To make a control tube, student fill one cylinder with 125 ml of dispersion liquid, which is subsequently mixed with distilled water until it reaches 1000 ml. Next is hanging the thermometer on the inside of the cylinder and carefully placing the hydrometer in the cylinder. When the hydrometer has stopped bobbing, read the value along the top of the meniscus and also along the bottom and recording the readings. The reading from the top of the meniscus is called the zero correction (C0) and the difference between the two readings is called the meniscus correction (CM ). This tube is used to determine zero correction and calibrate the zero scale of hydrometer if there is dispersion liquid in the water with the same concentration and meniscus scale as relative error that may occur during hydrometer reading due to adhesion.In the implementation of this practicum, sample of soil that has been prepared in the dispersion liquid is poured into mixer container and added with some water until 2/3 height of the container. Students also make sure theres no soil left in the glass to prevent the decreasing of sample of soil mass. Later on, the container is placed into mixer and mixed for about 10 minutes. After mixing, sample of soil is poured into hydrometer jar. To make sure if theres no soil left, a squirt bottle filled of distilled water is used to help transfer all of the mixture to the hydrometer jar. Afterwards, the next step is adding some distilled water into hydrometer jar that has been filled with sample of soil until it reaches 1000 ml. Next, students place the rubber stopper on the cylinder containing the soil mixture using a side-by-side motion for about 60 seconds, making sure that no soil remains stuck to the sides or bottom. While one team member is mixing, another needs to make sure the stopwatch is set to zero and ready to start. Once mixing is complete, the timer is started immediately. The next step is taking the hydrometer and gently placing it in the soil mix so that the hydrometer wont sink. After the hydrometer is stable, students take the reading above the meniscus and also read the temperature in the control tube. This step is done at minute 1, 2, 3, 4, 8, 15, 30, 60, 120, 240, 480, 960, and 1440. Temperature reading is important to find temperature correction at hydrometer reading, which is subsequently used to find the value of k and CT factor. After all steps are conducted, sample of soil in hydrometer jar is sieved using no. 200 ASTM and washed until its clean. Sample of soil retained at the sieve will be used at sieve analysis practicum.3.4.2 Analysis of ResultAfter all data is gathered, data processing is done in order to determine the distribution of soil grains. To calculate the distribution of soil particle size, data from hydrometer reading, temperature, and the value of specific gravity, which is obtained from module 2, are used. In the calculation, factor of conversion is also used to calculate the final result of diameter and %finer, such as a, CT, k, and L.First thing to do is finding the correction factor a for Gs of 2.637, which soon be used to calculate %finer. A correction factor a is used to fix the source of error and a table of values can be found at Table 3.4. As the value of Gs increases, so too does a and vice versa. Next, temperature correction (CT) is calculated for each tube control reading according to table 3.5. Once the value of CT is found, Rc can also be obtained. This value of Rc is used later on in finding the value of % finer which soon is plotted to the final curve. Thereafter, factor k and L is used to determine the diameter of soil grains. Factor k is obtained using table 3.7 contains k values corresponding to temperature and specific gravity while L is from table 3.6 contains L values corresponding to known R values. L/t is simply the velocity of the settling particles. This value is important because the two final values that are required for the curve are percent finer, which is already calculated, and the corresponding diameters, which can be calculated using Stokes Law. Stokes Law is a function of settling velocity, among other things. All calculations of finding factors are done using interpolation or extrapolation if the desired number is not shown in the table. This curve is subsequently combined with the final curve from sieve analysis to determine the type of soil.3.4.3 Analysis of Error Personal errorPersonal error is a systematic error in observations peculiar to the observer. This kind of error occurs due to the lack of experience of the observer that also affects personal mistakes and practical ability. Personal error that might happen in this practicum during hydrometer and thermometer reading. Student might read the hydrometer and thermometer inaccurately. Other occurs during the shaking process of hydrometer jar. Student might shake the hydrometer jar not horizontally so that there might be soil remains stuck at the bottom or top of the hydrometer jar so that the mixture is not homogenous. Because its not homogenous, the actual reading will decrease significantly in respect to time. Instrumental errorInstrument error refers to the combined accuracy and precision of a measuring instrument, or the difference between the actual value and the value indicated by the instrument. Some apparatus students used in this practicum might not properly. In this experiment, the mixer might do not mix the mixture until its homogenous. This will affects the actual reading of hydrometer due to changes in velocity of grain falling. Parallax errorThe definition of parallax error is an error that caused by both instrument and observer. This kind of error might happen when calculating the minute when we have to do the reading. Student might read the scale lately so that its not precisely corresponding to the time. The hydrometer and thermometer that do not show the scale clearly make the reading a lot harder and the possibility of wrong reading is quite high. This might cause inaccurate result of the practicum and later will lead to the incorrect calculation.

3.5 CONCLUSIONThis practicum has a purpose to determine the distribution of soil grains with diameter of less than 0.074 mm (sieve no. 200 ASTM) using hydrometer method. After all procedures are conducted, a %finer vs diameter is obtained. This curve represents the distribution of particle where the increasing of %finer is directly proportional to diameter. The diameter itself is found by using Stokes law equation.

3.6 ReferencesLambe T.W. Soil Testing for Engineers. John Willey and Sons. New York. 1951.Punmia, B.C. Soil Mechanic and Foundation. Standard Book House. Delhie. 1981Wesley, LD. Mekanika Tanah. Badan Penerbit Pekerjaan Umum. 1977.

3.7 ATTACHMENTSTable 3.4 Correction Factors a for Unit Weight of Solids

Table 3.5 Temperature Correction Factors CT

Table 3.6 Values of Effective Depth Based on Hydrometer and Sedimentation Cylinder of Specific Sizes

Table 3.7 Values of k for Use in Equation for Computing Diameter of Particle in Hydrometer Analysis

Figure 3.3 Mixing Sample of Soil

Figure 3.4 Hydrometer Jar

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