This paper presents a case study of geotechnical investigation including geophysical investigation carried out at a typical power plant site, in different stages. Under each stage the subsurface has progressively been examined in greater detail than earlier stage of investigation. Due to high water table and dense over-burden, sampling in boreholes has been difficult. In-situ tests like dynamic cone penetration tests (DCPT), plate load tests (PLT) and pressuremeter tests (PMT) were also conducted to evaluate the soil parameters. With the accumulation of data and understanding of the sub-soil, the design of foundation system has been continuously improved. The data also helped in selection of most appropriate materials like cement, reinforcement and grade of concrete. The geotechnical data helped in proper planning of relatively deep excavations with stable slopes, excavation tools to reach the desired depth under high water table, measures for dewatering. All this information has resulted in an economical foundation system and thus reducing the construction time and avoiding surprises on account of soil strata variation.
One of the major requirements in planning, design and construction of power plants is proper and adequate sub-soil investigation. The object of the investigation is to provide the engineer with as much information as possible about the substrata and other geotechnical features of the area to enable him to design the foundations of the structures economically and ensure its stability. The site of the proposed coal fired power plant (2×500 MW), plot measuring about 3.0 sq.km, is located on the east coast of India. Geotechnical investigation, comprising of various in-situ soil tests, geophysical investigation and laboratory tests has been carried out in different stages. This paper describes the geotechnical investigation to characterise the sub-surface for foundation design of light and heavy structures under static loading of the Main Power House.
