Tishk International University

Tishk International University _______________________________________________________________

0


1

Course layout • Water content • Specific gravity • Sieve analysis • Amount of material in soils finer than sieve No. 200 • Hydrometer analysis • Liquid Limit test • Plastic limit test • Organic matter

References • Braja M. Das “Soil Mechanics laboratory manual” • Dante Fratta et al. “introduction to soil mechanics laboratory testing” • John T. Germaine and Amy V. Germaine “Geotechnical Laboratory Measurements for Engineers”


2

Introduction v Laboratory testing of soils is performed to determine their physical properties for

• The design of foundations and other geotechnical structures, • Quality control of soil compaction works.

v Natural soil deposits often exhibit a high degree of non-homogenity. The physical properties of a soil deposit can change to a great extent even within a few hundred feet. v Learning to perform laboratory tests of soils plays an important role in the geotechnical engineering profession. Use of Equipment v For accurate experimental results, the equipment should be properly maintained and calibrated from time to time, such as balances and proving rings. v It is necessary to see that all equipment is clean both before and after use. Better results will be obtained when the equipment being used is clean.

Figure 1-1 Laboratory devices and equipments Recording the Data v Record all data in the proper table immediately after it has been taken. Oftentimes, scribbles on scratch paper may later be illegible or even misplaced, which may result in having to conduct the experiment over, or in obtaining inaccurate results. Report Preparation v The laboratory report should be written by each student individually. This is one way for students to improve their technical writing skills. v Each report should contain: 1. Cover page-This page should include the title of the experiment, name, and date on which the experiment was performed. 2. Following the cover page, the items listed below should be included in the body of the report: a. Purpose of the experiment.


3

b. Equipment used. c. A schematic diagram of the main equipment used. d. A brief description of the test procedure. 3. Results-This should include the data sheet(s), sample calculations(s), and the required graph(s). 4. Conclusion-A discussion of the accuracy of the test procedure should be included in the conclusion, along with any possible sources of error. Graphs and Tables Prepared for the Report v Graphs and tables should be prepared as neatly as possible. Always give the units. v Graphs should be made as large as possible, and they should be properly labeled. Examples of a poorly-drawn graph and an acceptable graph are shown in Figure 1-2.

Figure 1-2. (a) A poorly drawn graph for dry unit weight of soil vs. moisture content (b) The results'given in (a), drawn in a more presentable manner Standard Test Procedures

v Most soil laboratories follow the procedures outline by the American Society for Testing and Materials (ASTM) and the American Association of State Highway and Transportation Officials (AASHTO). v The procedures and equipment for soil tests may vary slightly from laboratory to laboratory, but the basic concepts remain the same. v The test procedures described in this manual may not be exactly the same as specified by ASTM or AASHTO; however, for the students, it is beneficial to know the standard test designations and compare them with the laboratory work actually done. For this reason some selected AASHTO and ASTM standard test designations are given in Table 1-1.


4

Table (1-1) Some important AASHTO and ASTM test designation Name of Test AASHTO Test

Designation ASTM Test Designation

Water content T-265 D-2216 Specific gravity T-100 D-854 Sieve analysis T-87 T-88 D-421 Hydrometer analysis T-87 T-88 D-422 Liquid limit T-89 D-4318 Plastic limit T-90 D-4318 Shrinkage limit T-92 D-427 Standard Proctor compaction T-99 D-698 Modified Proctor compaction T-180 D-1557 Field density by sand cone T-191 D-1556 Permeability of granular soil T-215 D-24:34 Consolidation T-2l6 D-2435 Direct shear (granular soil) T-236 D-3080 Unconfined compression T-208 D-2166 Triaxial T-234 D-2850 AASHTO Soil Classification System M-145 D-3282 Unified Soil Classification System -- D-2487


5

Introduction Most laboratory tests in soil mechanics require the determination of water content. Water content is defined as � = ��ℎ� �� ℎ� �� • Water content is usually expressed in percent. • For better results, the minimum size of the most soil specimens should be approximately as given in Table 2-1. • These values are consistent with ASTM Test Designation D-2216. Table 2-1. Minimum Size of Moist Soil Samples to Determine Water Content Maximum particle size in the soil (mm) U.S. sieve No. Minimum mass of soil sample 0.425 40 20 2.0 10 50 4.75 4 100 9.5 3/8 in. 500 19.0 ¾ in. 2500 Equipments 1. Moisture can(s). Moisture cans are available in various sizes.

2. Oven with temperature control. • For drying, the temperature of oven is generally kept between 105°C to 110°C. • A higher temperature should be avoided to prevent the burning of organic matter in the soil.

3. Balance. The balance should have a readability of 0.01 g for specimens having amass of 200 gm or less. If the specimen has a mass of over 200 g, the readability should be 0.1 g.


6

Procedure 1. Determine the mass (gm) of the empty moisture can plus its cap (W1) and also record the number. 2. Place a sample of representative moist soil in the can. Close the can with its cap to avoid loss of moisture. 3. Determine the combined mass (gm) of the closed can and moist soil (W2). 4. Remove the cap from the top of the can and place it on the bottom (of the can). 5. Put the can (Step 4) in the oven to dry the soil to a constant weight. In most cases, 24 hours of drying is enough. 6. Determine the combined mass (gm) of the dry soil sample plus the can and its cap (W3). Calculation 1. Calculate the mass of moisture = W2 - W3 2. Calculate the mass of dry soil = W3 – W1 3. Calculate the water content �(%) = �2−�3�3−�1 × 100 Report the water content to the nearest 1 % or 0.1 % as appropriate based on the size of the specimen. A sample calculation of water content is given in Table 2-2. Table 2-2 Determination of water content Description of soil:……Brown silty clay…………………….……………………… Sample No. ………………… Location: …………………………………………………………………………………………………………………………………… Tested by:………………………………………………………………………………………… Date: / / Item Test No. 1 2 3 Can No. 42 31 54 Mass of can, W1 (gm) 17.31 18.92 16.07 Mass of can + wet soil, W2 (gm) 43.52 52.19 39.43 Mass of can + dry soil, W3 (gm) 39.86 47.61 36.13 Mass of moisture, W2-W3 (gm) 3.66 4.58 3.3 Mass of dry soil, W3-W1 (gm) 22.55 28.69 20.06 Moisture content, �(%) = �� × 100 16.2 16.0 16.5 Average moisture content: 16.2 % General Comments 1. Most natural soils, which are sandy and gravelly in nature, may have water contents up to about 15 to 20%. In natural fine-grained (silty or clayey) soils, water contents up to about 50 to 80% can be found. However, peat and highly organic soils with water contents up to about 500% are not uncommon. Typical values of water content for various types of natural soils in a saturated state are shown in Table 2-3.


7

2. Some organic soils may decompose during oven drying at 110°C. An oven drying temperature of n 0° may be too high for soils containing gypsum, as this material slowly dehydrates. According to ASTM, 'a drying temperature of 60°C is more appropriate for such soils. Table 2-3 typical values of water content is a saturated state Soil Natural water content in a saturated state (%) Loose uniform sand 25-30 Dense uniform sand 12-16 Loose angular-grained silty sand 25 Dense angular-grained silty sand 15 Stiff clay 20 Soft clay 30-50 Soft organic clay 80-130 Glacial till 10


8

Description of soil:…………………………….…………………….……………………… Sample No. ………………… Location: …………………………………………………………………………………………………………………………………… Tested by:………………………………………………………………………………………… Date: / / Item Test No. 1 2 3 Can No. Mass of can, W1 (gm) Mass of can + wet soil, W2 (gm) Mass of can + dry soil, W3 (gm) Mass of moisture, W2-W3 (gm) Mass of dry soil, W3-W1 (gm) Moisture content, �(%) = �� × 100 Average moisture content:


9

Introduction • In order to classify a soil for engineering purposes, one needs to know the distribution of the size of grains in a given soil mass. • Sieve analysis is a method used to determine the grain size distribution of soils. • Sieves are made of woven wires with square openings. • Note that as the sieve number increases the size of the openings decreases. • Table 3-1 gives a list of the U.S. standard sieve numbers with their corresponding size of openings. • For all practical purposes, the No. 200 sieve is the sieve with the smallest opening that should be used for the test. Table 3-1. U.S. Sieve Sizes Sieve No. Sieve size Sieve No. Sieve size 4 4.750 35 0.500 5 4.000 40 0.425 6 3.350 45 0.355 7 2.800 50 0.300 8 2.360 60 0.250 10 2.000 70 0.212 12 1.700 80 0.180 14 1.400 100 0.150 16 1.180 120 0.125 18 1.000 140 0.106 20 0.850 200 0.075 25 0.710 270 0.053 30 0.600 400 0.038


10

The method of sieve analysis described here is applicable for soils that are mostly granular with some or no fines. Equipment Sieves, a bottom pan, and a cover Note: Sieve numbers 4, 10, 20, 40, 60, 140, and 200 are generally used for most standard sieve analysis work A balance sensitive up to 0.1 g

Oven

Mechanical sieve shaker

Procedure 1. Collect a representative oven dry soil sample. Samples having largest particles of the size of No. 4 sieve openings (4.75 mm) should be about 500 grams. For soils having largest particles of size greater than 4.75 mm, larger weights are needed. 2. Break the soil sample into individual particles using a mortar and a rubber-tipped pestle. (Note: The idea is to break up the soil into individual particles, not to break the particles themselves.).


11

3. Determine the mass of the sample accurately to 0.1 g. 4. Prepare a stack of sieves. A sieve with larger openings is placed above a sieve with smaller openings. The sieve at the bottom should be No. 200. A bottom pan should be placed under sieve No. 200. As mentioned before, the sieves that are generally used in a stack are Nos. 4, 10,20,40,60, 140, and 200; however, more sieves can be placed in between. 5. Pour the soil prepared in Step 2 into the stack of sieves from the top. 6. Place the cover on the top of the stack of sieves. 7. Run the stack of sieves through a sieve shaker for about 10 to 15 minutes. 8. Stop the sieve shaker and remove the stack of sieves. 9. Weigh the amount of soil retained on each sieve and the bottom pan. 10. If a considerable amount of soil with silty and clayey fractions is retained on the No. 200 sieve, it has to be washed. Washing is done by taking the No. 200 sieve with the soil retained on it and pouring water through the sieve from a tap in the laboratory (Fig. 3-2).

Figure 3-2. Washing of the soil retained on No. 200 sieve. When the water passing through the sieve is clean, stop the flow of water. Transfer the soil retained on the sieve at the end of washing to a porcelain evaporating dish by back washing. Put it in the oven to dry to a constant weight. (Note: This step is not necessary if the amount of soil retained on the No. 200 sieve is small.) Determine the mass of the dry soil retained on No. 200 sieve. The difference between this mass and that retained on No. 200 sieve determined in Step 9 is the mass of soil that has washed through.


12

Calculation 1) Determine the mass of soil retained on each sieve (i.e., M�, M�, . . . M�) and in the pan (i.e., M�). 2) Determine the total mass of the soil: ΣM = M� + M�+. . . M�+. . . M� + M� 3) Determine the cumulative mass of soil retained above each sieve. For the i(��) sieve, it is ΣM�(��) = M� + M�+. . . +M� 4) The percent of soil retained on the i(��)sieve is Rt �(��) = ΣM�(��)/ΣM 5) The percent of soil passing the i(��) sieve (or percent finer) is Finer �(��) = 100− Rt �(��) Note: If soil retained on No.200 sieve is washed, the dry unit weight determined after washing (Step 10) should be used to calculate percent finer (than No. 200 sieve). The weight lost due to washing should be added to the weight of the soil retained on the pan. A sample calculation of sieve analysis is shown in Table 3-2.


13

Table 3-2. Sieve Analysis Description of soil: Sand with some fines Sample No. 2 Mass of oven dry specimen: 500 gm Location: Tested by: Date: Sieve No. Sieve opening size (mm)

Mass of soil retained on each sieve (gm) Cumulative mass on each sieve, R cumulative percentage of retained percentage of finer 4 4.75 0 0 0.0 100.0 10 2 40.2 40.2 8.1 91.9 20 0.85 84.6 124.8 25.0 75.0 30 0.6 50.2 175 35.1 64.9 40 0.425 40 215 43.1 56.9 60 0.25 106.4 321.4 64.5 35.5 140 0.106 108.8 430.2 86.3 13.7 200 0.075 59.4 489.6 98.3 1.7 pan -- 8.7 498.3 100.0 0.0 Graphs The grain-size distribution obtained from the sieve analysis is plotted in a semi-logarithmic graph paper with grain size plotted on the log scale and percent finer plotted on the natural scale. Figure 3-3 is a grain-size distribution plot for the calculation shown in Table 3--2.

From laboratory Calculations


14

Figure 3-3. Plot of percent finer vs. grain size from the calculation shown in Table 3-2. . The grain-size distribution plot helps to estimate the percent finer than a given sieve size which might not have been used during the test. . Other Calculations Determine ��, �� and ��. (from Fig. 3-3), which are, respectively, the diameters corresponding to percents finer of 10%, 30%, and 60%. Calculate the uniformity coefficient (��) and the coefficient of gradation (��) using the following Equation �� = �� and �� = (��)�� × ��

0

10

20

30

40

50

60

70

80

90

100

0.010.1110

Fine

r (%

)

Particle diameter (mm)


15

As an example, from Fig. 3-3, �� = 0.095 �� , �� = 0.21 �� and �� = 0.46 ��, so �� = �� = 0.460.095 = 4.84 and �� = (��)�� × �� = (0.21)�0.46 × 0.095 = 1.01


16

Data sheet/ Sieve Analysis Description of soil: Sample No. Mass of oven dry specimen: Location: Tested by: Date: Sieve No. Sieve opening size (mm)

Mass of soil retained on each sieve (gm) percentage of mass on each sieve, R cumulative percentage of retained percentage of finer


17

Introduction • This test method covers determination of the amount of material finer than a 75-μm (No. 200) sieve by washing. • Material finer than the 75-μm (No. 200) sieve (clay and silt) can be separated from larger particles much more efficiently and completely by wet sieving than with dry sieving. • The mass of the test specimen, after drying, shall conform with the following: Maximum Particle Size Standard sieve size Minimum mass of test sample 2.0 mm No.10 20 gm 4.75 mm No.4 100 gm 9.5 mm 3/8” 500 gm 19.0 mm ¾” 2.5 kg 37.5 mm 1½“ 10 kg 75.0 mm 3” 50 kg Equipments Sieves, a bottom pan, and a cover

Note: Sieve numbers 4, 10, 20, 40, 60, 140, and 200 are generally used for most standard sieve analysis work


18

A balance sensitive up to 0.1 g Oven

Mechanical sieve shaker

Procedure 1. Dry the test specimen to a constant mass at a temperature of (105-110)°C and determine its mass, ��. 2. Place the specimen on the uppermost (coarsest) sieve. 3. Wash the specimen (material) on the sieve(s) by means of a stream of water. 4. Continue the washing until the water coming through the sieve(s) is clear. 5. Dry the residue from each sieve to a constant mass using a temperature of (105-110)°C and determine the mass, ��. 6. Perform sieve analysis for the material retained on sieve No.200, as we learnt before in chapter 4. Keep in mind that the total weight for sieve analysis is ��.

Figure 4-1. Washing of the soil finer than sieve No.200.


19

Calculation Calculate the amount of material passing the 75-μm (No. 200) sieve, ��, by washing using the following formula: ��(%) = �� −�� × 100 A sample calculation is shown below, �� = 500 �� and �� = 350 �� (%) = 500− 350500 × 100 = 30% Step 1: Washing of the soil finer than sieve No.200 Sieve No. Sieve opening size (mm) Mass of soil retained on each sieve (gm) Cumulative mass on each sieve, R cumulative percentage of retained percentage of finer 4 4.75 10 2 20 0.85 30 0.6 40 0.425 60 0.25 140 0.106 200 0.075 ��From washing>> 350 pan -- ��,Total mass>> 500 Step 2: sieve analysis Sieve No. Sieve opening size (mm) Mass of soil retained on each sieve (gm) Cumulative mass on each sieve, R cumulative percentage of retained percentage of finer 4 4.75 0 0 0.0 100.0 10 2 20.7 20.7 4.1 95.9 20 0.85 74.2 94.9 19.0 81.0 30 0.6 30.5 125.4 25.1 74.9 40 0.425 27.3 152.7 30.5 69.5 60 0.25 75.2 227.9 45.6 54.4 140 0.106 83.9 311.8 62.4 37.6 200 0.075 350 70.0 30.0 pan -- 500 100.0 0.0


20

Figure 4-2. Plot of percent finer vs. grain size 0

10

20

30

40

50

60

70

80

90

100

0.010.1110

Fine

r (%

)

Particle diameter (mm)


21

Data sheet/ Sieve Analysis by washing on sieve No.200 Description of soil: Sample No. Mass of oven dry specimen: Location: Tested by: Date: Sieve No. Sieve opening size (mm)

Mass of soil retained on each sieve (gm) percentage of mass on each sieve, R cumulative percentage of retained percentage of finer


22

Introduction When a cohesive soil is mixed with an excessive amount of water, it will be in a somewhat liquid state and flow like a viscous liquid. However, when this viscous liquid is gradually dried, with the loss of moisture it will pass into a plastic state. With further reduction of moisture, the soil will pass into a semisolid and then into a solid state. This is shown in Fig. 5.1

Fig. 5.1 Atterberg limits • The moisture content (in percent) at which the cohesive soil will pass from a liquid state to a plastic state is called the liquid limit of the soil. • The moisture contents (in percent) at which the soil changes from a plastic to a semisolid state is referred to as the plastic limit • The moisture contents (in percent) at which the soil changes from a semisolid state to a solid state and the shrinkage limit. These limits are referred to as the Atterberg limits. In this chapter, the procedure to determine the liquid limit of a cohesive soil will be discussed.


23

Equipments 1. Casagrande liquid limit device 2. Grooving tool

3. Moisture cans 4. Porcelain evaporating dish. 5. Spatula 6. Oven 7. Balance sensitive up to 0.01 g 8. Plastic squeeze bottle 9. Paper towels The Casagrande liquid limit device essentially consists of a brass cup that can be raised and dropped through a distance of 10 mm on a hard rubber base by a cam operated by a crank (see Fig. 6-2a). Fig. 6-2b shows a schematic diagram of a grooving tool.

Fig. 5.2 schematic diagram of Casagrande f Liquid Limit device.


24

Procedure 1. Determine the mass of three/four moisture cans (��). 2. Put about 250 gm of air-dry soil, passed through No. 40 sieve, into an evaporating dish. Add water from the plastic squeeze bottle and mix the soil to the form of a uniform paste. 3. Place a portion of the paste in the brass cup of the liquid limit device. Using the spatula, smooth the surface of the soil in the cup such that the maximum depth of the soil is about 8 mm. 4. Using the grooving tool, cut a groove along the center line of the soil pat in the cup (Fig. 6-3). 5. Turn the crank of the liquid limit device at the rate of about 2 revolutions per second. • By this, the liquid limit cup will rise and drop through a vertical distance of 10 mm once for each revolution. • The soil from two sides of the cup will begin to flow toward the center. • Count the number of blows, N, for the groove in the soil to close through a distance of (12.7 mm) as shown in Fig. 6-3.

o If N = about 25 to 35, collect a moisture sample from the soil in the cup in a moisture can. Close the cover of the can, and determine the mass of the can plus the moist soil (��)· o Remove the rest of the soil paste from the cup to the evaporating dish. Use paper towels to thoroughly clean the cup. o If the soil is too dry, N will be more than about 35. In that case, remove the soil with the spatula to the evaporating dish. Clean the liquid limit cup thoroughly with paper towels. Mix the soil in the evaporating dish with more water, and try again. o If the soil is too wet, N will be less than about 25. In that case, remove the soil in the cup to the evaporating dish. Clean the liquid limit cup carefully with paper towels. Stir the soil paste with the spatula for some time to dry it up. The evaporating dish may be placed in the oven for a few minutes for drying also. Do not add dry soil to the wet-soil paste to reduce the moisture content for bringing it to the proper consistency. 6. Repeat Steps 3, 4 and 5 for different water contents. 7. Put the three/four moisture cans in the oven to dry to constant masses (��).


25

Figure 5.3 illustration of soil placement in the brass cup Calculation Determine the moisture content for each of the three/four trials (Steps 5, 6 and 7) as �(%) = �� −�� −�� × 100 Graph o Plot a semi-log graph between moisture content (arithmetic scale) versus number of blows, N (log scale). This will approximate a straight line, which is called the flow curve. o From the straight line, determine the moisture content � (%) corresponding to 25 blows. This is the liquid limit of the soil. o The magnitude of the slope of the flow line is called the flow index, ��, or �� = �� −��log�� − log�� Typical examples of liquid limit calculation and the corresponding graphs are shown in Table 5.1 and Fig. 5.4.


26

Table 5.1 Liquid Limit Test Description of soil: Gray silty caly Sample No. 4 Location: Tested by: Date: Item Test No. 1 2 3 Can No. 8 21 25 Mass of can, ��(gm) 15.26 17.01 15.17 Mass of can+ moist soil, ��(gm) 29.30 31.58 31.45 Mass of can+ dry soil, ��(gm) 25.84 27.72 26.96 Moisture content, �(%) = �� × 100 32.7 36.04 38.10 Number of blows, � 35 23 17 Liquid Limit= 35.2 Flow Index=�� = ��.�� = 18.74

Figure 5.4. Plot of moisture content (%) vs. number of blows for the liquid limit test results reported in Table 5.1. 32

33

34

35

36

37

38

39

wat

er co

nten

t (%

)

No. of blows

10 15 20 25 30 35 40

N=25

LL=35.2


27

General Comments ASTM also recommends this equation for determining the liquid limit of soils �� = �� 25��.�� where �� = moisture content, in percent, for 12.7 mm groove closure in the liquid limit device at � number of blows. To use this equation the values of � should be in the range (20 ≤ � ≤ 30).


28

Data sheet/ Liquid Limit Test Description of soil: Sample No. Location: Tested by: Date: Item Test No. 1 2 3 4 5 Can No. Mass of can, ��(gm) Mass of can+ moist soil, ��(gm) Mass of can+ dry soil, ��(gm) Moisture content, �(%) = �� × 100 Number of blows, � Liquid Limit= Flow Index

wat

er co

nten

t (%

)

No. of blows

10 15 20 25 30 35 40


29

Introduction The fundamental concept of plastic limit was introduced in Chapter 6 Equipment 1. Porcelain evaporating dish 2. Spatula 3. Plastic squeeze bottle with water 4. Moisture can 5. Ground glass plate 6. Balance Equipments 1. Porcelain evaporating dish 2. Spatula 3. Plastic squeeze bottle with water 4. Moisture can 5. Ground glass plate 6. Balance Procedure 1. Put a representative, air-dry soil sample, passed through No. 40 sieve, into a porcelain evaporating dish. 2. Add water from the plastic squeeze bottle to the soil and mix thoroughly. 3. Determine the mass ofa moisture can in grams and record it on the data sheet (��). 4. From the moist soil prepared in Step 2, prepare several ellipsoidal-shaped soil masses by squeezing the soil with your fingers. 5. Take one of the ellipsoidal-shaped soil masses (Step 4) and roll it on a ground glass plate using the palm of your hand (as shown below)


30

6. If the thread crumbles into several pieces when it reaches a diameter of (3.2 mm), collect the small crumbled pieces in the moisture can put the cover on the can. 7. Determine the mass of the can plus the wet soil (��) in grams. 8. After about 24 hours, remove the can from the oven and determine the mass of the can plus the dry soil (��) in grams. Calculations �� ,�� = �� = �� −�� −�� (100) The results may be presented in a tabular form as shown in Table 6-1. If the liquid limit of the soil is known, calculate the plasticity index, ��, as �� = �� − ��


31

Table 6-1 Plastic Limit Test Description of soil Gray clayey silt Sample No. 3 Location: Tasted by: Date: Can No. A1 Mass of can, ��(gm) 13.33 Mass of can+ moisture soil, ��(gm) 23.86 Mass of can+ dry soil, ��(gm) 22.27 �� = �� −�� −�� (��) 17.78 General comments: Following are typical values of PI of several clay minerals. Clay minerals PI Kaolinite 20-40 Illite 35-50 Montmorillonite 50-100


32

Data sheet/ Plastic Limit Test Description of soil Sample No. Location: Tasted by: Date: Can No. Mass of can, ��(gm) Mass of can+ moisture soil, ��(gm) Mass of can+ dry soil, ��(gm) �� = �� −�� −�� (��)


33

Introduction The specific gravity of a given material is defined as the ratio of the weight of a given volume of the material to the weight of an equal volume of distilled water. In soil mechanics, the specific gravity of soil solids (which is often referred to as the specific gravity of soil) is an important parameter for calculation of the weight-volume relationship. Thus specific gravity, �� is defined as �� = �� ℎ� (�� )�� ℎ� (�� )�� = �� ⁄�� = �� where, ��= mass of soil solids (g) �� = volume of soil solids (cm3) �� = density of water (g/cm3). The general ranges of the values of ��, for various soils are given in Table 7-1. The procedure for determination of specific gravity, �� described here is applicable for soils composed of particles smaller than 4.75 mm (No.4 U.S. sieve) in size. Table 7-1 General Ranges of �� for various soils Maximum particle size in the soil (mm) U.S. sieve No. Sand 2.63-2.67 Silts 2.65-2.7 Clay and silty clay 2.67-2.9 Organic soil Less than 2


34

Equipments Volumetric flask (500 ml).

Thermometer graduated in 0.5°Cdivision scale.

Balance sensitive up to 0.01 g. Distilled water. Hot-plate heater (and/or vacuum pump) Evaporating dishes.

Spatula.

Plastic squeeze bottle.

Drying oven.


35

Procedure 1. Clean the volumetric flask well and dry it, then measure the mass of the empty flask, M��. 2. Carefully fill the flask with de-aired, distilled water up to the 500 ml mark (bottom of the meniscus should be at the 500 ml mark). 3. Determine the mass of the flask and the water filled to the 500 ml mark, M�� 4. Insert the thermometer into the flask with the water and determine the temperature of the water, T�. (Steps 1 to 4 are to calculate the exact volume of the volumetric flask) 5. Remove the water from the volumetric flask. 6. Transfer oven-dry soil into the volumetric flask. The mass of the soil sample should be in accordance with values shown in Table 7-2. 7. Add distilled water to the volumetric flask containing the soil (or the soil paste) to make it about two-thirds full. 8. Remove the air from the soil-water mixture. This can be done by: a. Gently boiling the flask containing the soil-water mixture for about 15 to 20 minutes. Accompany the boiling with continuous agitation of the flask. Or b. Apply vacuum by a vacuum pump or aspirator until all of the entrapped air is out. This is an extremely important step. Most of the errors in the results of this test are due to entrapped air which is not removed. 9. Bring the temperature of the soil-water mixture in the volumetric flask down to room temperature. 10. Add de-aired, distilled water to the volumetric flask until the bottom of the meniscus touches the 500 ml mark. Also dry the outside of the flask. 11. Determine the combined mass of the bottle plus soil plus water (M��). 12. Determine the temperature of the soil and water in the flask, T�.


36

Table 7-2 Recommend mass for test specimen Soil type Specimen Dry mass (gm) when using 250 ml pycometer Specimen Dry mass (gm) when using 500 ml pycometer SP, SP-SM 60 ± 10 100 ± 10 SP-SC, SM, SC 45 ± 10 75 ± 10 Silt or clay 35 ± 10 50 ± 10 Calculations 1. Calculate the volume of the volumetric flask, �� as: �� = (�� −��)��,�� where: ��,�� = the mass density of water at �1, (see Table 7-3) 2. Calculate the mass of the volumetric flask and water, ��(��), at the test temperature, �2, as follows: ��(��) = �� + (�� × ��,��) where: ��,�� = the mass density of water at �2, (see Table 7-3) 3. Calculate the specific gravity at soil solids the test temperature, �2, as follows: �� (��) = ��(��) − (�� −��) where: ��= The mass of the oven dry soil solids (gm). The specific gravity, �� is generally reported on the value of the density of water at 20°�. so �� = �� (��) � ��,��,��°�� where: ��,��°�= the density of water at 20°�, (see Table 7-3).


37

Table 7-3 Density of water with temperature Temperature°� 15 15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9 Density gm/cm3 0.9991 0.99909 0.99907 0.99906 0.99904 0.99902 0.99901 0.99899 0.99898 0.99896 Temperature°� 16 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 16.9 Density gm/cm3 0.99895 0.99893 0.99891 0.9989 0.99888 0.99886 0.99885 0.99883 0.99881 0.99879 Temperature°� 17 17.1 17.2 17.3 17.4 17.5 17.6 17.7 17.8 17.9 Density gm/cm3 0.99878 0.99876 0.99874 0.99872 0.99871 0.99869 0.99867 0.99865 0.99863 0.99862 Temperature°� 18 18.1 18.2 18.3 18.4 18.5 18.6 18.7 18.8 18.9 Density gm/cm3 0.9986 0.99858 0.99856 0.99854 0.99852 0.9985 0.99848 0.99847 0.99845 0.99843 Temperature°� 19 19.1 19.2 19.3 19.4 19.5 19.6 19.7 19.8 19.9 Density gm/cm3 0.99841 0.99839 0.99837 0.99835 0.99833 0.99831 0.99829 0.99827 0.99825 0.99823 Temperature°� 20 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9 Density gm/cm3 0.99821 0.99819 0.99816 0.99814 0.99812 0.9981 0.99808 0.99806 0.99804 0.99802 Temperature°� 21 21.1 21.2 21.3 21.4 21.5 21.6 21.7 21.8 21.9 Density gm/cm3 0.99799 0.99797 0.99795 0.99793 0.99791 0.99789 0.99786 0.99784 0.99782 0.9978 Temperature°� 22 22.1 22.2 22.3 22.4 22.5 22.6 22.7 22.8 22.9 Density gm/cm3 0.99777 0.99775 0.99773 0.9977 0.99768 0.99766 0.99764 0.99761 0.99759 0.99756 Temperature°� 23 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 Density gm/cm3 0.99754 0.99752 0.99749 0.99747 0.99745 0.99742 0.9974 0.99737 0.99735 0.99732 Temperature°� 24 24.1 24.2 24.3 24.4 24.5 24.6 24.7 24.8 24.9 Density gm/cm3 0.9973 0.99727 0.99725 0.99723 0.9972 0.99717 0.99715 0.99712 0.9971 0.99707 Temperature°� 25 25.1 25.2 25.3 25.4 25.5 25.6 25.7 25.8 25.9 Density gm/cm3 0.99705 0.99702 0.997 0.99697 0.99694 0.99692 0.99689 0.99687 0.99684 0.99681 Temperature°� 26 26.1 26.2 26.3 26.4 26.5 26.6 26.7 26.8 26.9 Density gm/cm3 0.99679 0.99676 0.99673 0.99671 0.99668 0.99665 0.99663 0.9966 0.99657 0.99654 Temperature°� 27 27.1 27.2 27.3 27.4 27.5 27.6 27.7 27.8 27.9 Density gm/cm3 0.99652 0.99649 0.99646 0.99643 0.99641 0.99638 0.99635 0.99632 0.99629 0.99627 Temperature°� 28 28.1 28.2 28.3 28.4 28.5 28.6 28.7 28.8 28.9 Density gm/cm3 0.99624 0.99621 0.99618 0.99615 0.99612 0.99609 0.99607 0.99604 0.99601 0.99598 Temperature°� 29 29.1 29.2 29.3 29.4 29.5 29.6 29.7 29.8 29.9 Density gm/cm3 0.99595 0.99592 0.99589 0.99586 0.99583 0.9958 0.99577 0.99574 0.99571 0.99568 Temperature°� 30 30.1 30.2 30.3 30.4 30.5 30.6 30.7 30.8 30.9 Density gm/cm3 0.99565 0.99562 0.99559 0.99556 0.99553 0.9955 0.99547 0.99544 0.99541 0.99538 A sample calculation for specific gravity is shown in Table 7-4


38

Table 7-4 Specific gravity of soil solids Description of soil: …………………………………………..Sample No.:…………………… Location:………………………………………………………………………………………………… Tested by:……………………………………………………………….Date: …………………….. Item Value Obtain

ed in the

lab. Volumetric flask No. 2A Mass of dry soil, ��(gm) 38.65 Mass of flask, ��(gm) 171.05 Temperature �1 (°C) 25 Mass of flask + water at �1, ��(��)(gm) 667.88 Temperature �2 (°C) 23 Mass of flask + water + soil at �2, �� (gm) 692.05

Calculations

Volume of flask, �� (cm3) 498.3 Mass of flask + water at �2, ��(��) (gm) 668.12 Specific gravity at �2, �� (��). �� (��) = ��(��)�(��) 2.63 Specific gravity at 20°�, ��. �� = �� (��) � ��,��,��°�� 2.62


39

Data sheet/ Specific gravity of soil solids Description of soil: ………………………………………..Sample No.:……………………… Location:………………………………………………………………………………………………… Tested by:……………………………………………………………….Date: …………………….. Item Value Obtain

ed in the

lab. Volumetric flask No. Mass of dry soil, ��(gm) Mass of flask, ��(gm) Temperature �1 (°C) Mass of flask + water at �1, ��(��)(gm) Temperature �2 (°C) Mass of flask + water + soil at �2, �� (gm)

Calculations

Volume of flask, �� (cm3) Mass of flask + water at �2, ��(��) (gm) Specific gravity at �2, �� (��). �� (��) = ��(��)�(��) Specific gravity at 20°�, ��. �� = �� (��) � ��,��,��°��


40

Introduction Organic content by loss on ignition is typically determined on sandy soils as well Jas organic clay, organic silt for geotechnical purposes. Organic content can be determined by loss on ignition (LOI) or chemical oxidation methods. This chapter deals specifically with the loss on ignition method, which is more straightforward and is typically used in geotechnical practice. Equipments Porcelain crucible Balance sensitive up to 0.01 g.

Drying oven. Furnace

Spatula.


41

Procedure 1. Determine the mass of a porcelain crucible (��) to 0.01 g. 2. Add about 10 gm of oven-dried soil to the crucible and determine the mass (��) to 0.01 g. 3. Place the crucible and contents in a muffle furnace. Gradually bring the muffle furnace up to 440˚C. Hold the furnace at this temperature until there is no change in mass. This usually takes about 4 to 5 hours. 4. Remove the crucible from the furnace, cover with aluminum foil, and place in a desiccator to cool. 5. Record the final mass of the crucible and ash (��) to 0.01 g. Calculations Computer the ash content as �� = �� −�� −�� Computer the organic content as �� = 100− �� Note: It is important to note that the Unified Soil Classification System (USCS) does not use the organic content test for determining whether a soil is described as organic. Rather, the USCS uses criteria based on the ratio of the liquid limit of a soil after oven - drying to the liquid limit before oven - drying.


42

Data sheet/ Organic Content Description of soil: ………………………………………..Sample No.:……………………… Location:………………………………………………………………………………………………… Tested by:……………………………………………………………….Date: …………………….. Item Value mass of a porcelain crucible (��) Mass of oven-dried soil and porcelain crucible (��) mass of the crucible and ash (��) Ash content: �� = �� Organic content : �� = 100− ��

Tishk International University

Documents

Transcript of Tishk International University