 The digging of test pits and trenching (particularly for locating faults and slide planes) may also be used to learn about soil conditions at depth.Large diameter borings are rarely used due to safety concerns and expense but are sometimes used to allow a geologist or engineer to be lowered into the borehole for direct visual and manual examination of the soil and rock stratigraphy.A variety of soil samplers exists to meet the needs of different engineering projects.