What is the impact of Horizontal Directional Drilling Machine crossing construction on soil layer

The Horizontal Directional Drilling Machine will have a certain disturbing effect on the soft soil layer, but when the drilling rig is drilling, due to the penetration of the wall-fixing mud and the influence of the wall-building performance, the soil structure around the passing pipeline will be strengthened, and the sandy soil around the pipeline will It is impossible to liquefy; at the same time, due to the wall-fixing and hole-stabilizing effect of the mud, a mud skin is formed around the wall of the passing well, and the wall-fixing and hole-stabilizing of the mud skin will also greatly reduce the permeability of the passing space. In addition, during the crossing construction process, the drill cuttings cut by reaming and the clay particles of the mud will also be squeezed into the formation gap around the annulus, thereby enhancing the compactness of the annulus. Therefore, the working characteristics of the drilling rig itself will eliminate the disturbance effect of drilling construction on the soft soil layer, and the impact on the hard rock layer will be smaller.

Directional drilling requires stable traversing holes during the process of drilling pilot holes, reaming, and pulling back pipelines. Its technological characteristics determine that the existence of directional drilling through the pipeline only changes the seepage characteristics of the local soil around the pipeline. As long as the buried depth of the pipeline under the embankment is small, it has little effect on the seepage near the embankment body and the inner foot of the embankment, making it unlikely that the embankment will lose stability and resist sliding. Directional traversal itself will not be successful if the ground collapses due to the instability of the hole walls.
After the horizontal directional crossing is completed, the airport interface between the pipeline and the crossing hole is filled with mud. In a short period of time, due to the effect of mud dehydration and sedimentation and the earth's gravity field, plus the density of mud used for directional crossing is about 1.1 to 1.2 times that of water, the annular space will basically be filled with mud dehydrated clay particles, and the lower density is higher than Upper, localized small collapse holes will not have adverse effects. In the range >15m near the directional drilling excavation site, in order to meet the connection requirements of buried pipelines, trenches need to be excavated. The trench excavation depth is generally about 2m. When backfilling, use 3:7 lime soil to backfill. During backfilling, the layers are compacted. The crossing holes within a certain depth can also be filled and compacted, and the soil structure can be improved within a certain range.