Which of the following is considered to be a non-soil component in geotechnical engineering?

A non-soil component in geotechnical engineering refers to materials that do not fall under the traditional classification of soil, which primarily consists of soil particles, organic matter, water, and air. Gas is indeed classified as a non-soil component. In the context of geotechnical engineering, gas, such as air pockets or other gases found in soil or rock formations, can have significant implications on soil behavior and stability.

Understanding this distinction is critical in geotechnical studies and applications, as the behavior of gas within soil matrices can affect porosity, permeability, and compaction characteristics. In contrast, materials like water, rock, and minerals are integral to the soil composition, encompassing both saturated conditions (water) and the physical forms that soil particles take (rock and minerals). Hence, gas stands out as the non-soil component among the options provided.