Guidelines for Sealing Geotechnical Exploratory Holes

A three year research project was sponsored by the Transportation Research Board (TRB) in 1991 to determine the best materials and methods for sealing small diameter geotechnical exploratory holes. A key requirement of the research project was to verity the effectiveness of the in-place seals. Seal verification studies were conducted at two sites, one in the USA and one in Canada. Seals consisting of various bentonite products and Portland cement were installed and allowed to age. Periodic in situ hydraulic conductivity tests were performed at the Canadian site. Seal exhumation studies were conducted at the USA site. Upon completion of the research in 1994-5, hole sealing guidelines were published by the National Cooperative Highway Research Program (NCHRP). This paper provides an overview of the research project and describes the hole sealing guidelines