Do you know the impact of horizontal directional drilling on soil layer?

Horizontal directional drilling is divided into three processes: pilot hole drilling, pre reaming and pipe dragging. The geological conditions suitable for directional crossing are usually clay, loam, silt, silt, fine sand layer and whole rock layer. Only when there is a certain thickness of pebble layer on both sides of the entrance and exit, directional drilling crossing can be realized through casing, reinforcement, excavation and other measures. Do you know which horizontal directional drilling affects the soil layer? The following editor has sorted out some information to share with you, hoping to help you.

Directional drilling will disturb the soft soil layer to a certain extent, but when drilling, due to the penetration of solid wall mud and the influence of wall building performance, the soil structure around the pipeline will be strengthened, and the sand around the pipeline cannot be liquefied; At the same time, due to the wall fixing and hole stabilizing effect of mud, mud skin is formed around the crossing shaft wall, and the wall fixing and hole stabilizing effect of mud skin will also greatly reduce the permeability of the crossing space. In addition, during the crossing construction, the drilling cuttings cut by reaming and the clay particles of 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 impact of drilling construction on soft soil layer and have less impact on hard rock layer.

Directional drilling crossing requires stable crossing holes in the process of drilling pilot holes, reaming and pulling back pipelines. Its technological characteristics determine that the existence of directional drilling crossing the pipeline only changes the seepage characteristics of local soil around the pipeline. As long as the safe buried depth of the pipeline under the embankment is guaranteed, the seepage near the embankment body and the inner foot of the embankment will not be affected much, making the embankment unlikely to lose stability and resist sliding. If the ground collapses due to the instability of the hole wall, the directional crossing itself will not succeed.

After the horizontal directional crossing is completed, the airport interface between the pipeline and the crossing hole is full of mud. In a short time, due to the effect of mud dehydration and sedimentation and the earth's gravity field, and the mud density used for directional crossing is about 1.1 ~ 1.2 times that of water, the annular space will basically be filled with mud dehydrated clay particles, the compactness of the lower part is higher than that of the upper part, and local small collapse holes will not have adverse effects. Within >15m around the excavation site of directional drilling, in order to meet the connection requirements of buried pipelines, pipe trenches need to be excavated. The excavation depth of pipe trench is generally about 2m. When backfilling, use 3:7 lime soil for backfilling. During backfilling, each layer is compacted. The crossing hole within a certain depth can also be filled and compacted, and the soil structure can be improved within a certain range.