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Re: Need advise for special foundation and soils problems

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I think you have a strike-slip fault (slow mover).  I know of a building
locally that has the same problem - constructed about 1910 and if you look
at the interior it is trapezoidal having displaced close to a foot.  You
might triangulate and get a measurement from the corners.  If they are not
90 deg. then it is a fault.  They put turnbuckles on the building that I
cited back in the 40's but it didn't really help.  Just guessing, I would
look at a deep vertical (thin) trench filled with rigid styrofoam placed
normal to the direction of the fault (I am not 100% on how effective this
would be and was thinking about submitting it as an abstract for higher risk
zones and importance) but didn't because I'm not 100%.
                                                                Greg
-----Original Message-----
From: Seaintonln(--nospam--at)aol.com <Seaintonln(--nospam--at)aol.com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Saturday, March 20, 1999 12:33 PM
Subject: Need advise for special foundation and soils problems


>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
>
>