Methods used in the excavation of shafts supported by artificial ground freezing

Artificial Ground Freezing has been used as a method of providing temporary earth support and ground water control for shaft construction for well over 100 years. Design analyses of the thermal and structural methods for evaluating the freezing method and systems have been presented extensively in the literature during the past 25 years, while the excavation methods and procedures are often neglected. This paper evaluates the methods of shaft excavation used on several shafts in North America. Consideration is given to the initiation of excavation related to surface water control and initial shaft alignment. Excavation techniques such as drilling and blasting, raise boring and road header operations are discussed.