Historical note in soil mechanics: Who is credited with coining and popularizing the term “soil mechanics” and establishing its modern scientific basis?

Introduction / Context:
Soil mechanics emerged as a modern discipline in the early 20th century. Knowing key contributors helps contextualize foundational theories used every day in geotechnical practice.

Given Data / Assumptions:

• Question seeks the principal figure associated with the term and field of soil mechanics.
• Emphasis is on the origin and consolidation of the discipline as a coherent science.

Concept / Approach:
Karl Terzaghi is widely regarded as the father of soil mechanics. His pioneering work on effective stress, consolidation theory, and earth pressure laid the foundations of geotechnical engineering. His 1925 book “Erdbaumechanik” unified disparate observations into a systematic framework and popularized the terminology and methods.

Step-by-Step Solution:

Verification / Alternative check:
Textbooks routinely begin with Terzaghi’s contributions; professional societies (e.g., ASCE) honor him through Terzaghi Lectures and awards.

Why Other Options Are Wrong:

• Kray, Leygue: lesser-known figures without foundational roles in defining the field.
• Fellenius: notable for pile capacity methods and slope stability developments, but not credited with originating “soil mechanics.”
• Casagrande: made major advances in classification and consolidation, yet Terzaghi remains the primary originator.

Common Pitfalls:
Confusing early contributors; remembering that “effective stress” is central to Terzaghi’s legacy.

Final Answer:
Karl Terzaghi