Which drilling method maintains undisturbed porosity and permeability of the soil?

The method that maintains undisturbed porosity and permeability of the soil is Direct Push Technology. This technique involves the use of a mechanical device that drives a sampling tool into the ground without the use of drilling fluid, such as water or air. This is significant because traditional drilling methods can disturb the soil structure, causing alterations in porosity and permeability.

Direct Push Technology allows for the collection of soil samples while preserving the sample's in-situ conditions. The method minimizes disturbances, allowing for more accurate assessments of subsurface conditions, which is crucial for applications such as environmental assessments, geotechnical investigations, and groundwater studies where the characteristics of the soil need to be preserved for accurate analysis.

This approach contrasts with drilling methods like rotary drilling, reverse circulation drilling, and auger drilling, which typically disrupt the soil during the process, potentially altering its properties and rendering the samples less representative of the undisturbed condition. Therefore, Direct Push Technology is the preferred method when the goal is to obtain samples that accurately reflect the original state of the soil.