(2) Pressure changes. One policy on grouting pressures advocates the
adjustment of injection rates and mixes as necessary to reach and hold the
maximum allowable pressure for as much of the grouting period as possible.
While the adoption of this policy will result in denser grout, deeper penetra-
tion of groutable openings, and wider grout spread, it will also cause more
lifting, more grout leaks, and more wasted grout, especially if the maximum
allowable pressure is also the estimated maximum safe pressure. When the
maximum safe pressure is exceeded, lifting or grout breakout will take place
no matter how accurately or inaccurately it was estimated. Therefore, the
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