Kansas City, Missouri
2010-2011
ECO designed a grouting program to stop a substantial inflow into two declines in the “deep mine”. The tunnels intersect water bearing strata. The inflow of brackish water into the declines was laden with hydrogen sulfide gas which presented the challenge of creating durable grouts since the mine is expected to have a life of 100+ years. The formation pressure of the inflow is 300 psi. Challenges for the remedial grouting under flow conditions included following stringent in-house safety protocol and working on a continuous slope of 17%. In addition, the hydraulic conductivity of the rock matrix was governed by matrix porosity. As a result even microfine cement had a very poor amenability coefficient.
The inflow was pronounced throughout both tunnels (including crosscuts) along a 600 foot section (per tunnel). The Phase 1 (post excavation) grouting program consisted of reducing/stopping the inflow into the existing tunnels. The Phase 2 grouting program consisted of pre-excavation grouting to facilitate the tunnelling operations through the second and the lower part of the first water bearing zone.
A combination of different grouts and grout formulations was successfully used: acrylamide in conjunction with polyurethane, cement based grouts with polyurethane, acrylamide in conjunction with cement based grouts. A variety of grouting techniques was implemented stop the inflow throughout a very fractured and heterogeneous rock formation. Prior to grouting, all holes were stimulated with acid to open up the porous rock matrix and dissolve the cuttings. There was a continuous need to perform crack injection (polyurethane) to prevent/minimize wash-out of the acrylamide grout during the permeation grouting. Squeeze grouting (thixotropic cement based grouts) was needed to abandon the grouted holes properly. In addition the grouting program required the installation of wedges and polyurethane drench grout pads and barrier bags.
This project was designed by ECO and successfully executed by the miners under the direction and hands-on engineering of ECO.