What does 'effective stress' signify in soil mechanics?

Prepare for your GERTC Hydraulics, Pneumatics, and Geotechnical Engineering Test. Study with multiple choice questions, detailed hints, and explanations. Get set for the HPGE exam!

Effective stress is a critical concept in soil mechanics, representing the stress that contributes to the strength of the soil. This principle, introduced by Karl Terzaghi, is fundamental in understanding how soil behaves under load. Effective stress is defined as the difference between the total stress acting on a soil mass and the pore water pressure within that soil.

When soil is subjected to external loads, the effective stress determines the soil's ability to support those loads, influencing its strength, compressibility, and overall stability. As effective stress increases, the soil particles are brought closer together, which enhances the inter-particle friction and cohesion. This results in increased shear strength, thereby allowing the soil to effectively resist deformation and failure.

The other options touch upon significant aspects of soil behavior but do not encapsulate the core meaning of effective stress. The total weight of soil on a given area represents total stress, while moisture pressure pertains to pore water pressure. The pressure exerted by soil particles alone is not a complete representation either, as it does not account for the effects of pore water on soil behavior. Therefore, the response describing the stress that contributes to the strength of soil aptly captures the essence of effective stress in soil mechanics.

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