EXPLORATORY BORING DRILLING
Drilling was executed by wash boring method. A hole was started by driving vertically a 10cm diameter steel casing into the ground to some depth and then the formation ground casing was broken up by repeated drops of a chopping bit attached to the lower and of drilling pipe. In this way drilling is advanced up to a level of 15cm above the depth, where Standard Penetration Test (SPT) has to be executed.
STANDARD PENETRATION TEST
The Standard Penetration Test (SPT) is widely used to determine the in-situ properties of soil. The test is especially suited for cohesion less soils as the correlation between the SPT value and f is now well established. The standard test methods are provided in ASTM D1586, D1587 and ASTM D6066. The test consists of driving a split spoon sampler, into soil through a borehole of 55 to 100 mm in diameter at the desired depth. It is done by a hammer weighing 63.5 kg (140 lb) dropping onto a drill rod from a height of 750 mm (30 inch). The number of blows N required to produce a penetration of 300 mm (12 inches) is regarded as the penetration resistance.
COLLECTION OF DISTURBED SAMPLE (DS)
These are the samples in which the natural structure of the soil gets disturbed during sampling. However, these samples truly represent the composition and the mineral content of the soil. The disturbed samples were collected with the help of split spoon sampler used during standard penetration test as per ASTM D 1586 standard at every 5 feet (1.50m).
COLLECTION OF UNDISTURBED SAMPLES (UD)
These are the samples in which the natural structure of the soil and the water content are retained. The Undisturbed Samples of cohesive soils were obtained with the help of thin walled Shelby Tubes of 3″ (76mm) diameter penetrated in to the undisturbed soil formation by applying rapid but continuous force as per ASTM D 1587 standard.
MEASURING GROUND WATER TABLE LOCATION
Ground Water Levels along the project alignment were measured during drilling operation and 24 hours afterwards by rope or rod sounding. Specific ground water level readings are indicated on the Boring Logs. It is noted; however, ground water levels fluctuate seasonally, climatically and due to other factors not evident at the time of field explorations.