HomeMy WebLinkAbout03443 Cory and Tess Wesson
October 13, 2000
Page 2
presented on Fig. 3, indicate low to moderate compressibility under conditions of
loading and wetting. No free water was observed in the pits at the time of excavation
and the soils were slightly moist to moist.
Foundation Recommendations: Considering the subsoil conditions encountered in the
exploratory pits and the nature of the proposed construction, we recommend spread
footings placed on the undisturbed natural soil designed for an allowable soil bearing
pressure of 1,500 psf for support of the proposed residence. The soils tend to compress
after wetting and there could be some post - construction foundation settlement. The
amount of settlement would depend on the depth and extent of subsurface wetting.
Footings should be a minimum width of 18 inches for continuous walls and 2 feet for
columns. Loose and disturbed soils encountered at the foundation bearing level within
the excavation should be removed and the . footing bearing level extended down to the
undisturbed natural soils. The exposed subgrade should be moistened and compacted
prior to placing concrete. Exterior footings should be provided with adequate cover
above their bearing elevations for frost protection. Placement of footings at least 36
inches below the exterior grade is typically used in this area. Continuous foundation
walls should be reinforced top and bottom to span local anomalies such as by assuming
an unsupported length of at least 12 feet. Foundation walls acting as retaining
structures should be designed to resist a lateral earth pressure based on an equivalent
fluid unit weight of at least 55 pcf for the on -site soil as backfill.
Floor Slabs: The natural on -site soils, exclusive of topsoil, are suitable to support
lightly loaded slab -on -grade construction. The soils are compressible when wetted. To
reduce the effects of some differential movement, floor slabs should be separated from
all bearing walls and columns with expansion joints which allow unrestrained vertical
movement. Floor slab control joints should be used to reduce damage due to shrinkage
cracking. The requirements for joint spacing and slab reinforcement should be
established by the designer based on experience and the intended slab use. A minimum
4 inch layer of sand and gravel (such as road base) could be placed beneath slabs for
subgrade support. This material should consist of minus 2 inch aggregate with less than
50% passing the No. 4 sieve and less than 12% passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of
maximum standard Proctor density at a moisture content near optimum. Required fill
can consist of the on -site soils or a suitable imported sand and gravel devoid of
vegetation, topsoil and oversized rock.
Surface Drainage: The following drainage precautions should be observed during
construction and maintained at all times after the residence bas been completed:
1) Inundation of the foundation excavations and underslab areas should be
H-P GEOTECH
. •
Cory and Tess Wesson
October 13, 2000
Page 4
construction to review and monitor the implementation of our recommendations, and to
verify that the recommendations have been appropriately interpreted. Significant design
changes may require additional analysis or modifications to the recommendations
presented herein. We recommend on -site observation of excavations and foundation
bearing strata and testing of structural fill by a representative of the geotechnical
engineer.
If you have any questions or if we may be of further assistance, please let us know.
Sincerely,
HEPWORTH - PAWLAK GEOTEC , .I„;,,‘..1,
INC.
_
:''o °; •
Jordy Z. Adamson Jr., . . 0 29 07 D+
Reviewed by: O sit �9 p�.,, tolplw : #''/
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A ...„ „. .-j( 1 ""0 , ..............-0- -
Daniel E. Hardin, P.E.
JZA /tl
attachments
cc: Demco Construction - Attn: Gary Heisel
H -P GEOTECH
•
Moisture Content = 21.3 percent
Dry Density = 100 pcf
Sample of: Slightly Sandy Silty Clay
From: Pit 1 at 6 Feet
K 0
1
No movement
a upon
A 2 wetting
0.1 1.0 10 100
APPUED PRESSURE — ksf
Moisture Content = 17.9 percent
Dry Density = 103 pcf
Sample of Sandy Silty Clay
From: Pit 2 at 3 Feet
0.
1 No movement
upon
a wetting
2
U
3
0.1 1.0 10 100
APPUED PRESSURE — ksf PAWLA 100 793 I GEOWECHNICAL INC. SWELL — CONSOLIDATION TEST RESULTS I Fig. 3