On the continued Role of Water Pressure Testing in Grout Design and Implementation-PPT Presentation

PPT Presentation

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The paper argues that water pressure tests (WPTs) and grout Lugeon (GuL) tests serve different, complementary purposes in curtain-grouting programs. WPTs use water to assess fracture flow and ground permeability, making them the essential “acid test” for determining whether a completed curtain meets acceptability criteria. GuL tests use grout and are more useful for evaluating grout penetrability, rock-mass amenability, and quality control during injection. Because grout and water flow differently—and results also depend on fracture characteristics, grout mix, and rock-mass variability—GuL results alone cannot reliably demonstrate curtain closure.<br /><br />The authors recommend using both tests throughout a project. Iterative WPTs can measure changes from baseline conditions, while real-time GuL monitoring helps track injection and refusal. Fully tested verification holes, supported by geological and piezometric data, are important for assessing final curtain performance.<br /><br />A five-step approach is proposed: conduct site-wide WPTs to establish design targets; characterize fractures through mapping and downhole acoustic televiewer (ATV) surveys; design curtain layout around mapped fracture patterns; compare fracture-aperture distributions with WPT-derived transmissivities; and refine hole geometry and grout-mix sequencing accordingly.<br /><br />The paper also calls for better site investigation, greater use of ATV data, and routine downhole pressure measurement with instrumented packers to account for line losses and complex groundwater conditions. Overall, reliable curtain design and closure assessment require combining geological characterization, WPTs, GuL monitoring, and targeted verification—not relying on grout pressure testing alone.

Keywords

water pressure tests

grout Lugeon tests

curtain grouting

fracture permeability

grout penetrability

quality control

verification holes

downhole acoustic televiewer

transmissivity

groundwater conditions