Planning and Performing Compaction Grouting

Abstract

Compaction grouting requires proper preinjection engineering which must include determination of the extent, scope, and objectives desired. The extent of the mass to be stabilized must be determined, with special attention given to depth of competent bearing material as grout placed above a weak zone could accelerate settlement due to increased overburden pressure. Equipment capable of mixing and pumping the very stiff, mortar-like grout at injection rates of 0.3 cu ft (0.008 m3)/min-2 cu ft (0.6 m3)/min and pressures to 1,000 psi (7,000 kN/m2) is desirable. Grout holes which are placed every 10 ft (3 m) on a basic grid are injected in vertical stages of 4 (1.2 m) - 8 ft (2.4 m) preferably advancing from the top down. Detailed grouting records should be kept and analyzed. The program must be flexible in order to take advantage of the important data obtained during injection. Evaluation of results can be by resistance to further injection, test hole data, or calculations based on quantity of grout pumped.