 The objective is to achieve greater overall economy, without compromising safety.The observational method was proposed by Karl Terzaghi and discussed in a paper by Ralph B. Peck (1969) in an effort to reduce the costs during construction incurred by designing earth structures based on the most-unfavorable assumptions (in other words, geological conditions, soil engineering properties and so on).Instead, the design is based on the most-probable conditions rather than the most-unfavorable.