Water pressure testing in exploratory holes is used to gather data on the permeability of soil and rock formations. It is best practice to perform water pressure testing prior to any ground modification program. This will provide a profile of the permeability prior to construction, or control that can be compared to the final results. Knowing the initial permeability is beneficial when selecting ground modification means, methods, and materials. Upon completion of the ground modification program, water pressure testing of verification holes provide quantitative results to demonstrate the degree of improvement achieved and effectiveness of the program.
Water pressure testing is performed by isolating stages within a borehole with a pneumatic double packer. The stages can vary in length and are typically 10 to 20 feet long. To test the bottom of the borehole, a single packer is used. Each test is run for approximately 5 minutes.
Effective injection pressures are limited to 0.5 psi per foot of overburden soils + 1 psi per foot of rock; measured at midpoint of the stage being tested. Pressure and flow are monitored, controlled and recorded in real-time through electronic flow meters and pressure transmitters.
ACT has performed over 15,000 hours of water pressure testing; including water pressure testing at the Clearwater Dam Exploratory Drilling and Grouting – Phase 1B, the Wolf Creek Dam Grout Curtain, and the Center Hill Dam Foundation Grouting projects.