Hello All, New member here. I am a layman as far as engineering goes and was hoping for some guidance, from an expert Geotechnical engineer. The topic I am interested in is the installation of pipes by Trenchless Drilling - i.e. Horizontal Directional Drilling. Specifically, I am interested in resources/ information/ case studies that pertains to the effect HDD, when applied incorrectly (say in uncontrolled fill), can have on soil and the formation of subsurface voids and the process by which these manifest into surface sinkholes/ depressions. Any information that relates to this, from a layman's perspective, would be helpful. I will need to be able to have enough data points to translate this into my field to construct a position. Thanks in advance.