## 3 Material and Method
### Afterberg's Limits  
The objective of testing for Atterberg's limits was to determine the basic index nature of the soil. This gives an idea of the strength and settlement characteristics of the material in-situ. It is also the primary form of classification of fine-grained soils. Atterberg's limits are used to determine the boundaries between the different states of fine-grained soils. The classical states associated with clay are liquid, plastic, semisolid, and solid. However, the laboratory tests were performed to determine only the plastic and liquid limits of fine-grained soil because of the logistical limitation of the laboratory.  
The liquid limit (LL) is defined as the water content at which a pat of soil in a standard cup and cut by a groove of standard dimensions' flows together at the base of the groove for a distance of 13 mm (1/2 in.) when subjected to 25 shocks from the cup being dropped 10 mm in a standard liquid limit apparatus operated at a rate of two shocks per second [28]. The liquid limit property of the fine-grained fractions of the samples was tested using a Casagrande liquid limit device, a grooving tool, a water bottle, mixing dishes, a spatula, and the Vacutec drying oven.  
The testing procedure began by cleaning up and calibrating the Casagrande equipment. The calibration involved the setting of the drop of the cup to a consistency drop height of 10 mm. The soil was then passed through a #40 sieve, collected, and air-dried. The fraction of soil was  
Figure 2: Topographical map of the study area with the designed traverses across the area of interest.  
thoroughly mixed with a small amount of distilled water until it turns into a smooth uniform paste. The moist sample was placed on the Casagrande's cup and smoothening to the maximum depth of 8 mm. The groove was cut at the centerline of the sample in the cup. Next, the device was cranked at 2 revolutions per second until the two halves of the soil pat come into clear contact of about 13 mm long at the bottom of the groove. The number of blows (N) that caused the closure was counted and recorded. The sample in the pat was collected, weighted together with the can, labeled, and dried in the oven at 110 \({}^{\circ}\)C for 6 h. The weight of the dried sample was also determined. The test was repeated 3 times at different moisture contents; this enabled the production of successively lower numbers of blows to close the groove. The number of blows in each trial was then plotted against the water content. The best-fit straight line through the plotted data points was constructed for which the liquid limit (LL) was determined as the water content corresponding to 25 blows.  
In plotting the limited liquid data, some samples do not conform well to the expected straight line. This may be ascribed to the inadequate mass of soil in the brass cup, inadequate rate of blows, or inadequate height of fall. To compensate for this, Equation (1) was used [28]:  
\[LL=W_{n}\left(\frac{N}{25}\right)^{0.121} \tag{1}\]  
where \(LL\) is the liquid limit of the soil, \(N\) is the number of blows in the liquid limit device, and \(W_{n}\) is the corresponding moisture content.  
The plastic limit testing of the soil samples was looked at next. The plastic limit (PL) of soil is defined as the water content at which the soil begins to crumble when rolled into a thread of 3 mm in diameter [28; 29].