ABSTRACT
In order to study how to control the proper mud pressure in the oval hole formed by horizontal directional drilling construction to maintain the stability of the soil around the hole and avoid the instability of the hole wall, this paper analyzes the stress field and displacement field of the hole and derived the theoretical solution of the limit value of mud pressure using the plastic increment theory combined with the column hole expansion theory. The research shows that the limit mud pressure of the elliptical hole is only 56% of the limit mud pressure of the circular hole, which indicates that when the hole ovalization deformation occurs from the circular hole, the hole wall is more prone to instability, and it is more necessary to reduce the mud pressure reasonably. The limit mud pressure difference between an elliptical hole and a circular hole decreases with the increase in cohesion and increases with the increase in internal friction angle. Improving cohesion is more important for preventing the instability of elliptical hole walls.
