What is a trial pit investigation?
Trial pits are carried out in order to recover large bulk samples of soil or if detailed visual examination of the strata is required. The main advantage of this method compared with light-cable percussion drilling or window sampling is the relative speed with which the work can be carried out. The disadvantage is the level of surface disturbance and the difficulty in carrying out effective reinstatement of the excavations.
Trial pits are usually carried out when the ground is able to stand temporarily unsupported. Where there is water present in the excavation, problems may be encountered due to instability of the side walls. There can also be difficulty obtaining representative samples of the ground due to fine material washing out with the water as the sample is recovered.