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The various method of site exploration can be grouped under, which of the following?
Open excavations and Borings
Soil strata
None of the mentioned
All of the mentioned
Open excavations and Borings
Methods of site exploration for geotechnical investigations are broadly categorized into direct and semi-direct physical inspection techniques, specifically open excavations and borings. Open excavations allow direct visual inspection of shallow soil strata, while borings enable subsurface sampling and field testing at greater depths.
Methods of site exploration for geotechnical investigations are broadly categorized into direct and semi-direct physical inspection techniques, specifically open excavations and borings. Open excavations allow direct visual inspection of shallow soil strata, while borings enable subsurface sampling and field testing at greater depths.
Drā=emaxāāemināemaxāāeāĆ100% ā Relative density of coarse-grained soil collected from exploration
Arā=D1āĀ°2D2āĀ°2āD1āĀ°2āĆ100% ā Area ratio of soil sampler to evaluate degree of disturbance
Site exploration aims to determine the sequence, thickness, and lateral extent of soil strata along with groundwater conditions. Open excavations (pitts or trenches) provide a direct view of undisturbed soil profiles up to limited depths, while boring methods (such as auger, wash, or rotary drilling) penetrate deeper layers to collect disturbed/undisturbed samples and assess engineering properties.
Open excavations (trial pits) are suitable for shallow depths up to about 3Ā m to 6Ā m.
Borings are essential for deeper exploration where trial pits become economical or structurally unsafe.
Boring types include displacement boring, auger boring, wash boring, percussion drilling, and rotary drilling.
Soil strata itself represents the ground profile being investigated, not a method of exploration.
Open excavations allow detailed visual inspection of natural soil macro-fabric and strata in situ.
Borings allow extraction of samples at significant depths below the ground surface and water table.
Open excavations are limited by depth and costly below the groundwater table without dewatering.
Borings may cause soil disturbance depending on the sampler type and drilling technique.
Foundation design for buildings, bridges, dams, and retaining walls.
Pavement subgrade evaluation and locate suitable borrow pit materials.
| Feature | Open Excavations | Borings |
|---|---|---|
Depth Range | Shallow (typically up to 3ā6 m) | Deep (can reach several tens to hundreds of meters) |
Visual Inspection | Direct visual exam of undisturbed strata wall | Indirect examination via retrieved samples |
Suitability Below Water Table | Requires extensive dewatering or side support | Easily executed using drilling mud/casing |
For undisturbed soil sampling, the sampler area ratio (Arā) should preferably be less than or equal to 10%.
Option B ('Soil strata') refers to the layers of soil present underground, which is the object of exploration rather than a method.
Option C and D are incorrect because open excavations and borings constitute valid, primary field exploration techniques.
A is correct ā Methods of site exploration are broadly classified into direct methods like open excavations and subsurface techniques such as borings.
Remember that an area ratio Arāā¤10% indicates an undisturbed sample, a frequent numerical question in geotechnical engineering exams like GATE and ESE.