Gravity Grouting and Its Future Alternative for Soil Reinforcement Systems

Abstract

Gravity grouting technique is commonly used in soil nailing and ground anchorage systems to increase pull out capacity of soil inclusions. Bond strength in between soil-grout interface estimates the pull out capacity of a grouted soil nail/anchor. The bond strength improvement due to gravity grouting and pressure grouting is very limited and grout likely shrinks after setting, resulting in reduction of skin friction between cement grout and surrounding soil of drill hole. One of the major concerns of soil nailing techniques is excessive lateral movement or creep behaviour over the service life and a case study of instrumented ground anchor wall reported that gravity grouted soil reinforcement technique experience excessive creep behaviours. The application of fracture grouting technique in soil nailing is very new and presumably it not only provides drill hole expansion but also provides mechanical interlocking between the penetrating grout and surrounding soil, which could resist the creep behaviour of soil-nails as well as enhance the bond resistance. The application of fracture grouting in soil nailing system could also be a cost-effective method since it likely to increase the pullout resistance of soil-nails, resulting in reduction of the number of soil-nails.