CIE 334 SOIL MECHANICS LABORATORY REPORT Lab 1

CIE 334
SOIL MECHANICS LABORATORY REPORT
Lab 1:Atterberg Limits
Peng SuLab Section F,9/13/2018 17:00-18:50
Teaching Assistant: Michael Murphy
9/20/2018
Contents
Table of Contents Introduction …………………………………………………………………………………………………..………….. 2 Methodology ……………………………………………………………………………………………………………….. 2 Results and Discussion ………………………………………………………………………………………………….. 2 Coefficient of Consolidation …………..…………………………………………………………….. 2 Consolidation Curve ……………………….…………………………………………………………….. 7
Empirical Values ……………………………………………………………………………………… 8 Conclusion ……………………………………………..……………………………………………………………….. 10 References ……………………………………………..……………………………………………………………….. 11 Appendix ……………………………………………..……………………………………………………………….. 12 TOC o “1-3” h z u

IntroductionThe engineers used the Atterberg limits tests to evaluate the engineering property of soil. In this lab, we did two kinds of experiments. One is liquid limit test, another is plastic limit test. In this lab, we studied four factors of the soil. They are liquid limit, plastic limit, plastic index and flow index of the soil. And we used ASTM D-4318 to determine Atterberg limits.

MethodologyLiquid limit testFor testing the liquid limit, Casagrande’s percussion cup method are used. In this method, the mass of the soil at different states and the number blows on the cup are recorded. Then, the moisture content can be found from equation 1.

w%=M2-M3M3-M1×100% Eq.1Where:
M1=Mass of canM2=Mass of can+mass of moist soilM3=Mass of can+mass of dry soilBy plotting the graph of moisture content vs. number of blows from four sets of data, the liquid limit of the soil are found. According to ASTM: D-4318, liquid limit test-percussion cup method, the moisture content (w) corresponding to 25 blows is the liquid limit of the soil.

31369012700 25
Number of blows?log scale?
w
Moisture content (%)
00 25
Number of blows?log scale?
w
Moisture content (%)

right9525Figure 1: simple plot of moisture content vs. number of blows
0Figure 1: simple plot of moisture content vs. number of blows

Also, the flow index FI can be found from the slop of the line by equation 2.

FI=w1(%)-w2(%)logN2-logN1 Eq.2Where:
w1%=moisture content at point #1w2%=moisture content at point #2N1=Number of blows correspoding to point #1N1=Number of blows correspoding to point #2Plastic limit testIn the laboratory, the plastic limit is defined as the moisture content at which a thread of soil will just crumble when rolled to a diameter of 1/8 in. (3.2mm).(ASTM: D-4318). In this test, the mass of the wet soil and the mass of the oven-dry soil are needed. Using these two data can calculate the plastic limit of the soil easily from equation 3.

PL=mass of moisturemass of dry soil=M2-M3M3-M1×100% Eq.3Where:
M1=Mass of canM2=Mass of can+mass of moist soilM3=Mass of can+mass of dry soilThen, the plasticity index can be found by subtracting the liquid limit and the plastic limit from equation 4.

PI=LL-PL Eq.4Where:
LL=liquid limit of the soilPL=plastic limit of the soilMethodsLiquid limit testAccording to the ASTM: D4318, Casagrande’s percussion cup method were used to determine the liquid limit of the soil. Weighting four empty cans on the balance sensitive. Record the mass of each can. Using No.40 sieve to filtrate about 250g of air-dry soil on the soft board. Then, add water from the plastic squeeze bottle to the finer soil on the soft board and using spatula to make a uniform paste. Take a portion of the paste into the cup of the liquid limit device by using spatula. Then, using spatula to make the surface of the pat flat and smooth. Using grooving tool to make a centerline of the soil pat in the cup. The centerline should around 2mm width. Using the liquid limit device to rise and drop the cup about 10mm height for one drop at the rate of two drops per second. Record the number of drop until the soil close through a distance of 13mm. Take a portion of the soil in one of the pre-weighted empty can. Weighting the can with the soil on the balance sensitive and record the data. Take the remaining soil from the cup to the soft board. Add water on it. It helped to increase the moisture content of the soil. Repeat the process to get four sets of data. Then, using the oven to dry the 4 samples. The cans with dry soil were weighted again by using balance sensitive. The 4 sets of oven-dry soil were recorded.

Plastic limit testThe plastic limit test was performed according to ASTM: D4318. Using the U.S. No.40 sieve to filtrate approximately 30 g of an air-dry soil sample. Weighting an empty cans on the balance sensitive. Record the mass of the can. Then, add water from the plastic squeeze bottle to the finer soil on the soft board. Each members in the group took a portion of the wet soil and rolled it at the rate of about 80 strokes per minute. Break the thread when the diameter of the thread reached 3.2mm. Collect the samples from each member. Put the samples into the pre-weighted can. Using sensitive balance to get the mass of the can with wet soil. Record the data. Using the oven to dry the soil. The mass of the can with dry soil was recorded using the sensitive balance.

ResultsFigure 2 shows the result of liquid limit test by plotting the moisture content of each sample and the corresponding number of blows. Table 1 shows the result of the liquid limit and plastic limit test.
.
Figure 2: mositure content vs. number of blows with trend line.

Table 1:
Liquid limit 24.90
Plastic limit 15.10
Plastic index 9.80
Flow index 4.98
DiscussionIn this experiment, the liquid limit and plastic limit of the soil were found. It is reasonable because liquid limit is always higher than plastic limit. In the plot of liquid limit test, the data from the sample of soil in can#3 has some error comparing with other points. In practice, the plot should approximate a straight line. And the soil with higher moisture content should achieve the target distance at lower number of blows. The data from the sample of the soil in can #3 had 23.36% moisture content, but it just needed 20 blows to achieve the target distance. A lot of factors can affect the result. For example, during the experiment, the soil in can#3 was explored in the air for a long period. The water inside the soil was evaporated. I t will cause the water content from that sample is less than the true value. Besides, the error can happen on the liquid limit device because the speed of rotation is controlled by human. It is hard to control the rotation at constant speed. The speed of rotation will affect the rate of collapse.
ConclusionIn conclusion, the goal of this experiment was completed. The engineering property of the sample of soil, liquid limit, plastic limit, plastic index and flow index, were determined.
To improve the experiment, the sample of wet soil should not be explored in the dry air for a long period. The experiment can be performed in an environment with high relative humidity to reduce the evaporation. Also, the liquid limit device can be improved. If the device can be run by electronic, the result will be more accurate.

ReferenceAmerican Society for Testing and Materials. Standard Test Methods for Liquid Limit, Plastic Limit, Plasticity Index and Flow Index of Soils, ASTM, West Conshohocken, PA, 1998.

AppendixTable 2: Data obtained from Liquid and Plastic Limit Tests
Can # Mass of Can (g) Mass of Soil+Can (g) Mass of Dry Soil+Can (g) # of blows w (%)
1 12.08 22.11 20.2 41 23.52
2 11.96 21.63 19.71 33 24.77
3 11.25 19.54 17.97 20 23.36
4 11.75 25.54 22.55 10 27.69
5 21.00 50.35 46.5 – 15.10