Bionic Design to Reduce Jacking Force for Trenchless Installations in Clay Soil

Abstract

The application of trenchless technology is the trend of underground public facilities’ installation, replacement and repairing. As the soil-engaging component during penetrating bore, the working resistance of penetration head has remarkable effect on energy consumption of the whole working process. Some typical soil-digging animals, like pangolin and earthworm, they own special micro structures on their surface. It has been widely proved that some micro geometrical structures can effectively reduce adhesion resistance. Four kinds of bionic penetration heads were designed by imitating micro geometrical structures inspired by the soil animals. In this work, the real time jacking forces of the bionic penetration heads were measured and compared with a smooth penetration head (control group) without micro geometrical structures. The result indicated that the jacking forces of the bionic penetration heads were smaller than that of the smooth penetration head. This proved that the bionic penetration heads have the ability of reducing adhesion resistance. The vertical concave penetration head got the smallest jacking force, of which the average jacking force was 18.7% lower than that of the smooth penetration head. The interaction between soil and bionic surface of penetration head was discussed on the condition of wet friction. The bionic surface reduced the adhesion resistance by disturbing the soil and braking the continuous water film between soil and the surface of the penetration head.