HomeMy WebLinkAboutPD 2021-0013; 3367 APPIAN ROAD; SOIL NAIL WALL SHORING DESIGN; 2020-12-11GeoStructural
December 11, 2020
FROM:
TO:
RE:
Andre Hawks, PE
Principal & Founder
Mr. Bruce Blandy
Owner
3367 Appian Road Carlsbad CA
Soil Nail Wall Shoring Design REV 0
Dear Mr. Blandy:
Engineering Inc
P. 1 of 10
I am pleased to present my Soil Nail Wall design for your project in Carlsbad, CA. The intent of the
Soil Nail Wall is to stabilize the sloped surficial soils from any future sliding.
Provided herein are structural design calculations, soil nail testing procedures, and construction drawings
for the Soil Nail Wall. Geotechnical design parameters were derived from the Limited Geotechnical
Investigation of Minor Slope Failure by Advanced Geotechnical Solutions Inc, dated July 23, 2020.
The Soil Nail Wall design is based on engineering methods typically employed by the Federal Highway
Administration (Service Load Design Method) for Soil Nail Walls. The design and the allowable factors
of safety on various components of the shoring system are per the recommendations contained in the
Federal Highway Administration (FHWA) "Manual for Design and Construction Monitoring of Soil
Nail Walls", Report No. FHWA-SA-96-069. Soil Nail facing design was performed in accordance with
FHW A guidelines.
Listed below is an outline of the pages included in this design package:
Pages 1-2:
Pages 3-6:
Page 7:
Pages 8-10:
Cover Letter
Soil Nail Testing Procedure
Stability Analysis
Drawings
www.geostructuralengineering.com
7172 Regional St #440 ~ Dublin, CA 94568
Email: andre.hawks@geostructuralengineering.com ~ Cell: 707-322-3507
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GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
If questions arise regarding my Soil Nail Wall design please contact me via email at
andre.hawks@geostructuralengineering.com
Best Regards,
EXP: 3-31-22
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Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Soil Nail Testing Procedures
Test Nail U nbonded Length
3
Provide temporary unbonded lengths for each test nail. The minimum unhanded length shall be 3 feet.
Isolate the test nail bar from the shotcrete facing and/ or the reaction frame used during testing.
Isolation of a test nail through the shotcrete facing shall not affect the location of the reinforcing steel
under the bearing plate.
Testing Equipment
Testing equipment shall include dial or digital gauges, gauge support, jack and pressure gauge, and a
reaction frame. The testing reaction frame shall be sufficiently rigid and of adequate dimensions such
that excessive deformation of the testing equipment does not occur. If the reaction frame will bear
directly on the shotcrete facing, it shall prevent cracking of the shotcrete. Independently support and
center the jack over the nail bar so that the bar does not carry the weight of the testing equipment.
Align the jack, bearing plates, and stressing anchorage with the bar such that unloading and
repositioning of the equipment will not be required during the test.
Apply and measure the test load with a hydraulic jack and pressure gauge. The pressure gauge shall be
graduated in 100 psi or less increments. Jack ram travel shall be sufficient to allow the test to be done
without resetting the equipment.
Measure the nail head movement with a dial or digital gauge capable of measuring to 0.001 inches. The
gauge shall have a travel sufficient to allow the test to be done without having to reset the gauge.
Visually align the gauge to be parallel with the axis of the nail and support the gauge independently from
the jack, wall or reaction frame.
Verification Testing
Perform one sacrificial verification test. The verification test nail location shall be selected by the
Contractor or as directed by the Engineer in the field.
Test nails shall have both bonded and unhanded lengths. The unbonded length of the test nail shall be
a minimum of 3 feet. The bonded length of the test nail shall be approximately 10 feet.
The maximum bar structural load during testing shall not exceed 90% of the yield strength for grade 75
bars or 80% of the ultimate strength for grade 150 bars.
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The Design Test Load (DTL) during verification testing shall be detennined by the following equation:
DTL = Design Test Load (kips) = LBL x Qd
LBL As-built bonded test length (feet)
Qd Allowable pullout resistance (see plans)
MTL = 2.0 x DTL = Maximum Test Load (kips)
Verification tests shall be performed by incrementally loading the test nail to a maximum test load of
200 percent of the Design Test Load (DTL). The nail movement at each load shall be measured and
recorded by the Engineer. The test load shall be monitored by a jack pressure gauge with a sensitivity
and range meeting the requirements of pressure gauges used for verification test nails. At load
increments below 1.5 DTL, the load shall be held long enough to obtain a stable reading. Incremental
loading for tests shall be in accordance with the following loading schedule. The soil nail movements
shall be recorded at each load increment.
VERIFICATION TEST LOADING SCHEDULE
LOAD HOLD TIME
AL (.10 DTL) Until Stable
0.25 DTL Until Stable
0.50 DTL Until Stable
0.75 DTL Until Stable
1.00 DTL Until Stable
1.25 DTL Until Stable
1.50 DTL 60 minutes
1.75 DTL 10 minutes
2.00 DTL 10 minutes
The alignment load (AL) should be the minimum load required to align the testing apparatus. Dial
gauges should be set to "zero" after the alignment load has been applied.
All load increments shall be maintained within 5 percent of the intended load. A 60-minute creep test
shall be performed at 1.50 DTL. The creep period shall start as soon as the test load is applied and the
nail movement shall be measured and recorded at 1, 2, 3, 5, 6, 10, 20, 30, 40, 50, and 60 minutes.
Proof Testing of Production Nails
Perform sacrificial proof testing for 5 percent (1 in 12) of the production nails in each nail row and a
minimum of 1 per row and 1 per distinct soil type. The proof test nail locations of each test nail shall be
detennined in the field by a Soil Nail contractor's representative.
Test nails shall have both bonded and unbonded lengths. The unbonded length of the test nail shall be
at least 3 feet and the bonded length of the test nail shall be 10 feet.
The allowable bar structural load during testing shall not exceed 90% of the yield strength for grade 75
bar and 80% of the ultimate strength for grade 150 bar.
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The Design Test Load (DTL) during proof testing shall be determined by the following equation:
DTL = Design Test Load (kips)= LBL x Qd
LBL As-built bonded test length (feet)
Qd Allowable pullout resistance (see plans)
MTL = 1.5 x DTL = Maximwn Test Load (kips)
Proof tests shall be performed by incrementally loading the proof test nail to a maximwn test load of
150 percent of the Design Test Load (DTL). The nail movement at each load shall be measured and
recorded by the Contractor. The test load shall be monitored by a jack pressure gauge. At load
increments other than maximum test load, the load shall be held long enough to obtain a stable reading.
Incremental loading for proof tests shall be in accordance with the following loading schedule. The soil
nail movements shall be recorded at each load increment.
PROOF TEST LOADING SCHEDULE
LOAD
AL (.10 DTL)
0.25 DTL
0.50 DTL
0.75 DTL
1.00 DTL
1.25 DTL
1.50 DTL (Max. Test Load)
HOLD TIME
Until Stable
Until Stable
Until Stable
Until Stable
Until Stable
Until Stable
See Below
The alignment load (AL) should be the minimwn load required to align the testing apparatus. Dial
gauges should be set to "zero" after the alignment load has been applied.
All load increments shall be maintained within 5 percent of the intended load. Depending on
performance, either 10 minute or 60 minute creep tests shall be performed at the maximum test load
(1 .50 DTL). The creep period shall start as soon as the maximwn test load is applied and the nail
movement shall be measured and recorded at 1, 2, 3, 5, 6, and 10 minutes. Where the nail movement
between 1 minute and 10 minutes exceeds 0.04 inch, the maximwn test load shall be maintained an
additional 50 minutes and movements shall be recorded at 20 minutes, 30, 50, and 60 minutes.
Test Nail Acceptance Criteria
A test nail shall be considered acceptable when:
1. A total creep movement ofless than 0.04 inch is measured between the 1 and 10 minute
readings, or a total creep movement of less than 0.08 inches is measured between the 6 and 60
minute readings. The creep rate must be linear or decreasing throughout the creep test load hold
period.
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2. A pullout failure does not occur at the maximum test load. Pullout failure is defined as the load
at which attempts to further increase the test load simply result in continued pullout movement
of the test nail. The pullout failure load shall be recorded as part of the test data.
Test Nail Rejection
If a test nail does not satisfy the acceptance criterion, the Contractor shall determine the cause. The
need for design and/ or construction procedure modifications shall be determined by the design
engineer. The Design Engineer may require additional nails in the area of the failed verification tests
and/ or in the next lower row of nails, longer nails, the installation of additional test nails, increased drill
hole diameters, modified installation or grouting methods, or closer nail spacings. Alternatively, the
Design Engineer may require the installation and testing of additional verification or proof test nails to
verify that adjacent previously installed production nails have sufficient load carrying capacity. All
necessary adjustments shall be submitted to the Building and Inspection Division for review and
approval prior to carrying out the work.
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Stability Analysis
Approach: The length of Soil Nails beyond the 32 degree from vertical failure plane prescribed by
the Soils Report must provide sufficient bonding capacity to provide a Safety Factor of at least 1.5.
CalEx Engineering the Temporary Soil Nail Wall contractor has reviewed the borings and estimates
to obtain an Ultimate grout to soil bond strength of 30 psi ( 15 psi allowable). The borings show
an average unit weight of approximately 125 pcf which will be used to calculate the weight of the
wedge of soil to be held back by the Soil Nails.
Tallest Section of Soil Nail Wall
Image below is taken form Auto CAD to calculate the area of the wedge and length of Soil Nails.
D I
(\J
Area of Wedge= 50 ft''2 Soil Nail Spacing= 4 ft x 5 ft
Volume of Wedge= 50 fi'-2 x 5 ft= 250 ft:"'3
Weight of Wedge = Volume of Wedge x PCP of Soil = 250 ft:"'3 x 125 PCP = 31,250 LBS
Design Wedge= 1.25 ( for variability) x Weight of Wedge= 39,100 LBS
Therefore, Design Load= (39,100 LBS/ 3 Nails) x 1.5 = 19.6 kips
Total L of Soil Nails Past Failure Plane= Design Wedge/ ( 2 x PI x Rx Allowable Skin Friction)
Total L of Soil Nails Past Failure Plane= 39,100 LBS / ( 2 x PI x 3 inches x 15 psi)
Total Length of Soil Nails Past Failure Plane = 139 inches = 12 ft
Bond Length Needed For 1 '\ 2nd & 3rd Row Nail= 12' / 3 = 4 ft each
Minimum Soil Nail Embedment = 10ft ( From Soils Report)
Therefore 1st Nail Length= 4ft Bonded ft+ 5.67 ft Wedge= 10 ft
Therefore 2nd Nail Length= 4ft Bonded+ 3.5 ft Wedge= 7.5 ft➔ 10ft
Therefore 3rd Nail Length= 4ft Bonded+ 1.5 ft Wedge= 5.5ft➔ 10ft
Facing Design Loading = ( 10' x 12) x 2 x PI x 3" x 15 psi= 34 kips
Grade 75 #7 Bar Min Yield= 45 kips> 34 kips Therefore OK
7
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