The mechanics of soil-Laboratory testing


This lab report involved two experiments to determine particle size distribution through sieve analysis and plastic and liquid limit of a soil sample. The two tests are very important in soil classification for engineering purposes. Sieve analysis is one of the widely used tests to classify soils. The test data and results can be used in determining the suitability of soils for constructions and other engineering purposes. The purpose of the sieve analysis test is to grade a soil sample to be used as aggregates. In addition, the test is to determine and classify a soil sample in a standard specification that can be used in producing various aggregates for engineering use (ASTM International, 2014). The sieve analysis test is carried out using a set of sieves of varied sizes. A vibrator is used to shake a soil sample in the sieve stack to find soil distribution across sieve sizes. The retained soils are weighed and recorded in a table which is the used to draw a graph for soil classification. The accuracy of the test is maintained at 0.1% for accurate results.

Soil consistency is another crucial aspect of soil classification in civil engineering. Soil resistance can be defined as the ability of soil at varying moisture content to resist mechanical stress (Rai, 2012). There are three moisture content levels that are used to describe the soil consistency, and they include wet, moist, and dry level (Rai, 2012). Engineering uses Atterberg Limits to determine soil properties depending on the moisture content of the soil (Rai, 2012; Viswanadham, 2013). The three Atterberg Limits are shrinkage limit, liquid limit, and plastic limit (Rai, 2012; Viswanadham, 2013). However, the purpose of this experiment is to determine the soil consistency by determining only the liquid limit and plastic limit of a soil sample to determine its engineering properties. Different containers were used for testing liquid limit and plastic limit to achieve the desired result. The weight of the containers used was obtained and recorded. Subsequently, wet and dry soil samples were weighed and recorded separately in a table. The moisture content in the soil was then determined from the obtained data. Liquid limit and plastic limit are used to determine the plasticity index of the soil sample. The plasticity index indicates the moisture content range at which the soil remains plastics(Viswanadham, 2013).


Experiment one: Test procedure for sieve analysis

First, the group weighed the scale pan to know its exact weight before weighing the soil sample.

A sample size of 1831.9 g was used for the sieve analysis. The sample size was accurately weighed and recorded to an accuracy of a decimal point.

Set of sieves, as shown in the diagram below, was arranged in a descending order in terms of the sieve sizes with the largest one on top. The soil sample aggregate was then poured on the top sieve, and the sieve stack mounted onto the vibration machine,

A mechanical shaker was used to vibrate the stack two minutes, after which the machine was stopped, and the lid removed.

Each sieve was carefully removed, and any clogged particles were brushed into the next sieve to maintain the sample size.

Individual weights of soil retained on each sieve were on a tray covered with plastic, and the weight determined on the scale pan and recorded in a table as shown in the result section.

Weighing procedure was repeated for all sieves sizes.

The weights obtained for sieve size was reported in terms of percentages of the sample size to the nearest 0.1%.

The material loss was maintained at less than 0.2 percent.

The sieve size was then plotted against percentage passing on a graph paper provided.

Experiment two: Test procedure for liquid and plastic limit determination

Four containers were used for the liquid limit (LL) determination and three for the plastic limit (PL) determination. The containers were labeled 1 to 4 and 1 to 3 respectively.

Weight of each empty container was recorded in the table.

Weight of wet soil and the container was weighed and recorded in a table. The weighing procedure was repeated with a dry soil and recorded in a table as well.

Weight of dry soil was determined and recorded in the table and used to calculate moisture in the soil. The moisture content was then reported in terms of percentage.

The number of blows for LL container was recorded as well.

The values recorded in the table were then used to calculate the liquid limit, plastic limit, and plastic index of the soil for its classification.

Pictures of the equipments used.

Student’s Name

Picture 1: Sieve Stack on a vibrator

Student’s Name 1

Picture 2: Weighing balances

Student’s Name 2

Picture 3: Sample size in a container

Student’s Name 3

Picture 4: Weighing sample in respective containers

Results and Analysis

Particle Size Distribution Test

Result Table

The weight of the scale pan= 268.13

Sample Size= 2100.02-268.13=1831.9 g

Total mass after the analysis= 1823.48 g

Sieve Size (mm)

% on sieve

% Passing

The graph of particle size distribution (Percentage passing vs Particle sizes, mm)

Student’s Name 4

The results, as shown in the graph, indicate that the soil sample almost evenly distributed between particle size of 0.1 mm to 20 mm. The sample size range also indicates that the soil sample mostly contains sand and gravel (University of the West of England, 2014). The wide range of sizes makes the soil sample suitable for engineering use for varied purposes because different soil aggregates can be produced from the analysis of the sample.

Liquid and plastic limit determination

Group number-4

Student Name-Abda

Type of test

Container Number

Wt of wet soil + Cont.

Wt of dry soils + cont.

Wt of container

Wt of moisture

Wt of dry soil

Moisture Content

Number of Blows

The graph of Moisture contents vs. Number of blows

Student’s Name 5


Moisture content=Weight of moisture/weight of dry soil*100

For test LL container 1, moisture content=1.7/9.4*100=18.1%

Liquid Limit= 19.8% (As obtained from the graph)

Plastic Limit (LL)

LL= Average moisture content (ASTM International, 2014)


Plasticity Index (PI) (ASTM International, 2014)



Soil Classification= Low sand with clay

The values of plastic limit, liquid limit and plasticity index show that the soil sample has enough moisture content to withstand mechanical stresses applied to it. Plasticity index is also close to one percent an indication the value of plastic limit and liquid limit are near accurate.


In conclusion, the data obtained from sieve analysis can be used in producing varying soil aggregates from the sample site. The soil sample is mainly sand and gravels, and, therefore, can be used as sand and gravel after sieving. From the liquid limits and plastic limit, the soil is well moisture to be suitable for engineering construction purposes.


ASTM International, 2014. Standard test methods for liquid limit, plastic limit, and plasticity index of soils. Available at: <>[Accessed 23 March 2015]

ASTM International, 2014. Standard test method for sieve analysis of fine and coarse aggregates. Available at: <>[Accessed 22 March 2015]

Rai, R., 2012. Consistency of soil. Available at: <>[Accessed 24 March 2015]

University of the West of England, 2014. Soil description and classification. Available at: <>[Accessed 24 March 2015]

Viswanadham, B.V.S., 2013. Soil mechanics. Available at: <>[Accessed 24 March 2015]