Soil texture are the medium-sized (0.05 - 0.002 mm) and sink to the bottom of the cylinder after the sand. Clay particles are the smallest (<0.002 mm) and separate out above the silt layer. Measurements are taken using a soil hydrometer. A soil hydrometer measures that relative density of liquids (density of a liquid to the density of water). The hydrometer is lowered into the cylinder containing the soil mixture at different times, forty-five seconds to measure sand content, one and a half hours to measure silt content and between six and twenty-four hours (depending on the protocol used) to measure clay.
Soil nailing is also acceptable as long as the rock is weathered evenly throughout (meaning no weakness planes). Finally, glacial soils work well for soil nailing. A list of unfavorable or difficult soil conditions for soil nailing can include dry, poorly graded cohesion-less soils, soils with a high groundwater table, soils with cobbles and boulders, soft to very soft fine-grained soils, highly corrosive soils, weathered rock with unfavorable weakness planes, and loess. Other difficult conditions include prolonged exposure to freezing temperatures, a climate that has a repeated freeze-and-thaw cycle, and granular soils that are very loose. Soil nailing evolved from the New