Soft Soil Around UG Pipe in Parking Lot

[layfieldman]

My customer wants to use a geogrid or geotextile to help with a soft wet silty clay around a underground gas pipe over which his parking lot is being built. There is 200mm of this soil over which 200mm of granular fill with a 50mm asphalt pavement will be placed. I know the calculations for embankments or for roads but not for this situation in which the parking lot extends for meters on either side of the soft soil. Can anybody tell me whether there are calculations published out there for this situation or a good rule of thumb for strength and embedment lengths required?

 

[Grouser]

layfieldman

How long has the pipe/soft clay been there? Is the clay consolidating and taking the gas pipe with it? Are you trying to bridge the soft clay or prevent overstressing the gas pipe, or both?
Since the pipe doesn't seem to be very deep, why not remove & replace the soft clay with granular roadbed material, at least above the gas pipe? A cost comparison with the geotextile/geogrid option seems worthwhile.