Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Need advise for special foundation and soils problems

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Grout is an excellent approach to your problem. What can be happening is
that the weight of this mass of grout is affecting a very recent
alluvial deposit of soils which is deeper than 15 feet and is located
towards your "drift". I would suggest exploratory borings to
approximately 40 feet minimum, with appropriate sampling. this would
provide a profile. The problem could be due to rapid deposits which have
never consolidated and combined with high organic content, ..well
This is just a thought for your consideration. Palm Springs is in an
area known to have problems due to very fast deposits of recent
alluvium.
Hope this helps.. it is  a very interesting situation. grouting or
densification of the soils should be an acceptable resolution.
Chris Lillback

Seaintonln(--nospam--at)aol.com wrote:
> 
> I have a problem that has been ongoing for about four years. I was called in
> to evaluate and resolve a problem with a post and beam building in a private
> Golf resort in La Quinta California. Here is some history.
> 
> The land was developed over fifty years ago -- dedicated by then President
> Dwight Eisenhower. From what I am able to tell, the site consisted of groves
> of Tamarisk trees. Tamarisks were not indigenous to this area and were brought
> in to be used as wind breaks. I also suspect that the site had a mixture of
> more indigenous varieties such as Palo Verde and Mesquites.
> I was told by one of the club members that little was done to ensure that
> clean fill was used during the creation of the golf course and I believe it
> was possible that not only roots were left, but that stumps where simply
> turned under.
> 
> The Club House was constructed in the early sixties -- at a time when the area
> was unincorporated. The structure is a one story post and beam (heavy timber)
> with plenty of glass and, in my opinion, lacking in lateral resistance.
> 
> The foundations, from what I can remember of the few original drawings I sway,
> consisted of a continuous shallow grade beam in the center of the building
> which carried the main 12x12 wood columns. The outer pads supporting the
> exterior wall columns are, I believe, tied from column to column, but are not
> tied back to the corridor foundation.
> 
> For about 25 years the building used a septic system until the city installed
> sewers in the mid 1990s.  Subsequent to the installation of the sewers,
> changes in the form of differential settlement started to be noticed
> throughout the building.  The property lies in the "flats" at the base of a
> residential section constructed in a Cove (surrounded on three sides by
> mountains). The cove is approximately one mile wide by three miles deep and
> contains approximately 1,500 homes. Sewers were installed within the last six
> years.
> 
> A culvert separates the Country club from the Cove and flooding has not been
> an issue in this area since the installation of the sewers / storm drains.
> 
> A soils company was brought in to investigate and try to find the cause of the
> settlement. Cores to 15 feet were taken throughout the building and at
> locations where damage was most notable.  A Manometer study was done and
> subsequent measurements were taken over the last three or four years.
> 
> Investigation of the sprinkling system and the existing plumbing and sewage
> system was done, but there was no indication (by pressure testing) of leakage.
> The leach field used by the old septic system is south of the building and far
> enough away from the structure to (by the soils engineers conclusion) not have
> been the cause of subsidence when the septic system was removed.
> 
> Soils
> The soil study indicated mostly sand. There is little if any clays on the site
> except those brought in to line a the golf course ponds which are more than
> 100 yards away from the building.  There are also natural wells on the
> property which we just learned about and we plan to do some static level
> monitoring to see if there is a dramatic changes.
> For the most part, the soil under the structure was confirmed to be moderate
> to high in organic which we are confident is causing the settlement.
> 
> A plan was created to pressure grout portions of the building and the phasing
> was done to coordinate both the clients budget and the seasonal timing around
> the members and tourists.
> 
> The main corridor was demolished in the 1997 in order to expose the
> foundations and to install some new footings under columns that became load
> bearing due to the settlement. Up until the time we pressure grouted, the tile
> along the main corridor would simply crack each time it was patched.
> Two years after the grouting of the corridor, the area has stayed level with
> little if any settlement.
> One exterior column was also pressure grouted. At the time, the soil below the
> column was so loose that almost three times the expected volume of gout was
> needed. Three years later, we are again noticing movement in this area.
> 
> Problem:
> We have plans to complete the pressure grouting of the building this spring
> and summer. My main problem is the following:
> The building site and surrounding grounds are level grade, however, the club
> has been noticing horizontal movement to the North and south of the corridor
> AND the exterior sidewalks and drives for golf cart use. Following the
> exterior curb lines, the displacement laterally is noticeable at each
> expansion joint. I do not see vertical displacements occurring on the exterior
> flatwork, however, I have suggested Manometer studies outside the structure
> and within say 25 feet of the building. The exterior flatwork is not
> continuously attached to the flatwork adjacent to the building as a planting
> area exists for grass. This would eliminate the idea that the with the
> subsidence of the soil below the column foundations that the columns and
> foundations are moving both vertically and horizontally (vector paths).
> I cannot find justification for the lateral movement when no major seismic
> events have occurred in the area, we are not on sloped or hillside property.
> 
> The movement is noticeable - 3/4" in less than three years.
> 
> I'm missing something here and can't figure out what it is. My only conclusion
> is that subsidence is occurring due to reduced compaction by the organic found
> in the soil. This would not account for the lateral movement.  The pond is too
> far from the structure to affect it and the soil between the building and pond
> is mostly sand -- very little clay was found.
> 
> I would appreciate any suggestions as to what I can do to search for a
> definitive answer for the lateral movement. Until then I am afraid to invest
> the Country Clubs money into more than resolving vertical subsidence.
> 
> Any suggestions, recommendations or comments would be greatly appreciated.
> 
> Sincerely,
> Dennis S. Wish PE
>