Trench Backfill With Lime Modified Soils

[irishman77]

Our local ordinance specifies a 12 inch soil cap for trench backfill over storm/sanitary sewers due to the requirement of lime modified soils. Our state sewer specifications do not address lime modified soils, but specify select granular backfill (sand), mechanically compacted in 6 in. lifts for final backfill, to the top of the subgrade. The contractor has been allowed to "jet" under paved areas. We are having real problems with "dips" in the road. Any suggestions on backfill/compaction options or the use of flowable fill? Keep in mind this is silty clay soil in Illinois with a relatively high water table.

 

[dirtsqueezer]

What does "jet" mean? Is that some form of compaction? I've heard of compaction by means of a water hose, but it only works for a very clean (silt and clay free) sand. Is this what you mean by "jetting"? If so, then that could be your problem right there.

 

[kenvlach]

'The contractor has been allowed to "jet" under paved areas. We are having real problems with "dips" in the road.'

1) Isn't that water jet horizontal boring?
2) Would pressure grouting work in such situations?