JNTU B.Tech III FOUNDATION ENGINEERING Previous Question Paper (February/March - 2022 - R18)

A soil investigation report is a comprehensive document that summarizes the findings of field and laboratory tests, providing essential data for the design and construction of foundations. The preparation of the report follows a systematic approach to ensure all geotechnical parameters are clearly communicated.

The report typically includes the following sections:

1. Introduction: States the purpose of the investigation, the scope of work, and details of the proposed structure, including its location and estimated loads.
2. Site Description: Describes the site topography, existing ground conditions, drainage patterns, and any visible surface features or geological hazards.
3. Field Investigation: Details the methods used, such as boreholes, trial pits, or cone penetration tests. It includes the number, location, and depth of explorations, along with groundwater table observations.
4. Laboratory Testing: Summarizes the tests performed on soil samples, such as grain size analysis, Atterberg limits, shear strength tests (triaxial or direct shear), and consolidation tests.
5. Subsurface Profile: Presents the soil stratification through borehole logs, which detail the sequence of soil layers, their thickness, and classification according to the Unified Soil Classification System (USCS).
6. Analysis and Recommendations: This is the core of the report. It provides calculations for bearing capacity, estimated settlement, and recommendations for the type of foundation (shallow or deep). It also suggests ground improvement techniques if the soil is unsuitable and provides advice on excavation support or dewatering requirements.
7. Appendices: Contains all raw data, including site plans, borehole logs, laboratory test result sheets, and relevant photographs of the site or samples.

The final report must be signed by a qualified geotechnical engineer, ensuring that all data is interpreted correctly to support safe and economical structural design.

Boring is the process of advancing a borehole into the ground to collect soil samples and determine the subsurface profile. Two common methods used in foundation engineering are Auger Boring and Wash Boring.

1. Auger Boring: This method is suitable for cohesive soils and soft to stiff clays above the water table. An auger, which is a helical screw-like tool, is rotated into the ground. As it penetrates, soil is collected in the flights of the auger. Once the auger is full, it is withdrawn to the surface to retrieve the soil sample.
Sketch description: A vertical rod connected to a helical auger bit at the bottom, with a handle at the top for manual rotation or a motor drive for mechanical operation.

2. Wash Boring: This method is effective in a wide range of soils, including sands and gravels. It involves using a chopping bit attached to a hollow drill rod. Water is pumped down through the drill rod, exits through the bit, and carries the loosened soil particles (cuttings) up to the surface through the annular space between the rod and the borehole wall. The water is then collected in a settling tank where the soil settles, and the clear water is recirculated.
Sketch description: A tripod setup with a pulley, a pump supplying water through a swivel connection to a hollow drill rod, a chopping bit at the base, and a return flow of water carrying soil to a settling pit.