JNTU B.Tech II ENGINEERING GEOLOGY Previous Question Paper (August/September - 2022 - R16)

Physical Geology deals with the study of geological processes such as weathering, erosion, sedimentation, and volcanic activity. Its importance in civil engineering lies in understanding how these surface processes modify the landscape, which is critical for site selection, slope stability analysis, and assessing the durability of construction materials.

Petrology is the study of rocks, including their origin, composition, and classification. It is essential for engineers to evaluate the suitability of rocks as building stones, aggregates, or foundation materials. Understanding the mineralogical and textural properties of igneous, sedimentary, and metamorphic rocks helps in predicting their strength, porosity, and permeability.

Structural Geology focuses on the study of rock deformations, such as folds, faults, joints, and unconformities. This branch is vital for identifying potential zones of weakness in the Earth's crust. Knowledge of structural features is mandatory for the safe design of dams, tunnels, and bridges, as these features can significantly influence rock mass stability and groundwater movement.

Case histories of engineering failures highlight the necessity of geological investigations. Notable examples include:

1. Malpasset Dam Failure (France): The dam collapsed due to the presence of a thin, undetected fault zone in the foundation rock. The geological investigation failed to identify the weakness, leading to catastrophic flooding when the foundation gave way under water pressure.
2. Vaiont Dam Disaster (Italy): This tragedy was caused by a massive landslide into the reservoir. The geological study failed to recognize the unstable nature of the limestone strata and the presence of clay layers that acted as a slip plane when saturated, triggering a displacement wave that overtopped the dam.
3. St. Francis Dam Failure (USA): The dam was built on a foundation of schist and conglomerate. The geological survey overlooked the fact that the rock would lose its strength and disintegrate when saturated. The resulting seepage and loss of foundation integrity led to the dam's total collapse.

These cases demonstrate that ignoring geological features like faults, weak bedding planes, and rock permeability can result in structural failure, emphasizing that geological site characterization is as important as structural design.