Green Apple Foundation Rpt

Draft Geotechnical Data

OR FS ERFO 2007(1)-11(1)

Highway 35 Betterment

This document is a draft and should NOT be relied upon to determine final conditions for bidding.

Final documents will be available during the advertisement period.

Preliminary Geotechnical Report No. 07-09

Oregon Highway 35 Green Apple Creek Bridge

OR FS ERFO 2007(1)-11(1), Mount Hood National Forest

Hood River County, Oregon September, 2009

Draf t

CONTENTS

(“Contents” to be revised for final report.)

PAGE

1. Introduction 1

2. White River Debris Flows at Green Apple Creek 1 3 Surface Conditions 2

4. Subsurface Investigations 2

4.1 Drilling Investigations 2

4.2 Investigation Results 2

4.3 Subsurface Water Levels 4

5. Laboratory Materials Testing 6

5.1 Soil Classification, Atterberg Limits, and Natural Moisture 6

5.2 Shear Strength Testing 6

6. Bridge Foundation Considerations 7

7. Lateral Loading by Debris Flow Impacts 7

8. Drilled Shaft Foundation Analysis and Design 8

8.1 Scour Recommendations 8

8.2 Earthquake Effects 8

8.3 SPT N-value Corrections 9

8.4 Liquefaction 10

8.5 Subsurface Soil Profile and Soil Strength Parameters 11

8.6 Drilled Shaft Analysis and Design 12

8.6a Design Loads 12 8.6b Preliminary Drilled Shaft Recommendations 12 8.6c Settlement 14 8.6d Lateral Analysis 15

9. Drilled Shaft Construction Considerations 15

10. Approach Embankments and Abutment Backfill 16

11. Use of this Report 18

12. References 19

FIGURES

FIGURE 1. Project Location Map iii FIGURE 2. Green Apple Creek Culverts after November 2006 Debris Flow 1 FIGURE 3. 5-Percent-Damped-Design Response Spectrum 9 FIGURE 4. Corrected SPT (N1)60 Values Plotted Versus Depth 10 ii

TABLES

TABLE 1. Boring Locations, Elevations, and Subsurface Water Levels 3 TABLE 2. Summary of Seismic Parameters (7% PE in 75 years) 8 TABLE 3. Subsurface Layers and Strength Parameters 11 TABLE 4. Preliminary Drilled Shaft Recommendations 14 TABLE 5. Recommended Soil Parameters for Lateral Analysis 15 TABLE 6. Recommended Soil Parameters for Abutment Wall Design 17

APPENDICES

APPENDIX A: Preliminary Bridge Layout with Boring Locations APPENDIX B: Boring Logs APPENDIX C: Unified Soil Classification System APPENDIX D: SPT N-Value Corrections APPENDIX E: Drilled Shaft Design Charts iii

Figure 1. Green Apple Creek Bridge Project Location Map.

GREEN APPLE CREEK

GOVERNMENT CAMP

1 MILE

N

1. INTRODUCTION

This report provides geotechnical investigation results, analysis, and foundation recommendations for a bridge over Green Apple Creek on Oregon Highway 35 on the southeast side of Mount Hood (Figure 1). Construction of a bridge at Green Apple Creek is part of a larger project encompassing sections of Highway 35 located at White River and between Clark and Newton Creeks about three miles north of White River.

This report provides preliminary foundation recommendations for initial bridge design based on preliminary loading information. A second report containing finalized foundation recommendations will be provided to the WFLHD Structures Section once the bridge design process has begun and the actual bridge geometry and design loads of the new structure have been determined.

2. WHITE RIVER DEBRIS FLOWS AT GREEN APPLE CREEK

Green Apple Creek is located about 400-600 feet north of White River and is affected by White River debris flows to the same extent as White River. The creek occupies two, closely-spaced channels that are currently carried beneath Highway 35 by two large pipe culverts about 110 feet apart. The culverts suffered major damage during the major flood event of November, 2006, as shown in Figure 2. During the design process for construction of a new bridge at White River, a decision was made to replace the twin Green Apple Creek culverts with a bridge.

The history and nature of debris flows in the White River Valley were comprehensively addressed in the report “White River Highway 35 Betterment Project, OR FS ERFO 2007 (1)-11(1): Geomorphic Assessment (December, 2007)”, prepared for the WFLHD’s Hydraulic Section by Pacific Water Resources, Inc., and R. W. Beck. The reader is referred to that report for additional geological, geomorphological, and hydrological information regarding White River debris flows.

Figure 2. Green Apple Creek after Nov. 2006 Debris Flow (taken by Doug Jones, Mount Hood National Forest, who estimated about 2/3 of White River flowing here at the time).

3. SURFACE CONDITIONS

The project site is located on the north side of the alluvial flood plain of White River, which is approximately 3000 feet wide where it is crossed by Highway 35. The flood plain is an aggrading deposit consisting predominantly of poorly-graded, fine to coarse silty sand, gravel, cobbles, and boulders that is classified as SM, SP-SM, and GP-GM soil in the Unified Soil Classification System (USCS).

The aggrading nature of White River Valley is the result of periodic debris flows that are unleashed from glacial moraines high on the slopes of Mount Hood following “rain-on-snow” events in the headwaters of White River.

4. BRIDGE FOUNDATION INVESTIGATION

4.1 Drilling Investigation

Three foundation investigation borings were drilled for the Green Apple Creek bridge at the appproximate abutment and center pier locations of the new bridge. All three borings were advanced by HQ wireline coring. Standard Penetration Tests (SPT) were performed at depth intervals of 5 feet with a 2 inch diameter split spoon sampler.

Boring locations are shown on the Green Apple Creek Preliminary Bridge Layout in Appendix A. The approximate design centerline locations, ground surface elevations, and water levels observed in the borings are summarized in Table 1 below:

Table 1. Boring Locations, Elevations, and Groundwater Levels

Boring No. Station and Offset

Ground Surface

Elevation1 (ft)

Boring Depth

(ft) Water Depth

(ft)

Water Elevation

(ft) GA-13 45+65, 29 ft. rt. 4241.5 99.5 ft 12.6 ft 4228.9

GA-14 46+75, 5 ft. lt. 4248.5 80 ft. 18 ft. 4230.5

GA-15 48+10, 2 ft. rt. 4242.5 100 ft. 13.5 4229.0

NOTES:

1Determined from contours on Preliminary Layout.

4.2 Investigation Results

Boring logs for the Green Apple Creek Bridge foundation investigation are contained in Appendix B. The materials encountered in the Green Apple Creek borings consisted predominantly of damp to wet, loose to very dense, silty, fine to coarse gravelly sand with cobbles and boulders, and were nearly identical to the materials encountered in the White River Bridge investigation borings (see discussion in Geotechnical Report No. 01- 09, “Oregon Highway 35 White River Bridge Replacement Foundation Investigation”, March, 2009”).

Because of their similarity to the White River subsurface materials, laboratory testing was not performed on samples obtained from the Green Apple Creek foundation investigation. The subsurface materials were visually classified as “SP-SM - poorly graded sand with silt and gravel”, “SM – silty sand and silty sand with gravel”, and “GP- GM – poorly graded gravel with silt and sand” in the Unified Soil Classification System

(USCS).

Boulders ranging from 12-25 inches in cored dimension were encountered in boring GA-13. A 12 inch boulder was encountered in boring GA-14, and several boulders ranging in cored dimension from 20-26 inches in size were encountered in boring

GA-15.

Observations of the surface cobbles and boulders in the flood plain of White River indicate that material is primarily andesite lava and pyroclastic volcanic rock typical of the Cascade volcanoes. Boulders up to 10 feet or more in longest dimension are visible on the surface of the White River and Green Apple Creek alluvial fan and boulders of that size may be encountered in the drilled shaft foundation excavations. The drilled shaft construction contractor for this project should be prepared to reduce boulders to a manageable and removable size should boulders of any size be encountered during shaft excavation and construction.

4.3 Subsurface Water Levels

Subsurface water levels were measured at depths of 12.6, 18, and 13.5 feet in borings GA-13, 14, and 15, respectively. The ground elevations corresponding to the water levels are 4228.9, 4230.5, and 4229.0 for borings GA-13, 14, and 15, respectively. Reference to the preliminary bridge layout in Appendix A shows that the the subsurface water elevations are slightly lower than the streambed elevation of 4231 at the downstream face of the proposed bridge. Subsurface water is likely to be encountered during drilled shaft construction at or near the elevation of the streambed and water elevations are likely to fluctuate with fluctuations of Green Apple Creek, particularly during spring thaw and following periods of heavy precipitation.

5. LABORATORY MATERIALS TESTING

5.1 Soil Classification, Atterberg Limits, and Natural Moisture

Due to the observed consistency and similarity of the samples from the White River investigation borings, it was not considered necessary to perform laboratory testing of samples from the Green Apple Creek borings. A discussion of White River material properties can be found in the previously-referenced geotechnical report for the White River foundation investigation.

5.2 Soil Shear Strength

Direct shear strength testing was performed by Cornforth Consultants of Portland, Oregon on a test sample comprised of seven combined SPT samples from two of four borings drilled on the upstream side of Highway 35 in 2007. The tested sample was classified as “SP-SM; poorly graded sand with silt and gravel” in the Unified Soil Classification System (USCS). The peak strength parameters obtained for the sample were cohesion = 0 and friction angle = 46 degrees. These are the shear strength values recommended for use in bridge foundation design at Green Apple Creek.

6. BRIDGE FOUNDATION CONSIDERATIONS

Due to scour depth and constructability, drilled shafts were selected over spread footings or driven piles for foundation support at the White River Bridge and drilled shafts are the recommended foundation at Green Apple Creek Bridge. The design and construction methodology for drilled shafts at White River Bridge are applicable to the design and construction of drilled shafts at Green Apple Creek. The following discussions regarding shaft design and construction were excerpted from Geotechnical Report No. 01-09 and modified as appropriate for the site conditions at Green Apple Creek.

7. LATERAL LOADING BY DEBRIS FLOW IMPACTS

The potential for debris flows to exert significant lateral loads on structures in the White River Valley was addressed during the design process for the new White River Bridge. It was determined that the existing White River Bridge had not sustained damage due to lateral loads from past debris flows. It was also determined that, due to the 3000 foot width and 6-8 percent gradient of the White River Valley at the bridge location, the energy available in debris flows by the time they reach the bridge to exert significant lateral loads is relatively low and not sufficient to control the foundation design.

Green Apple Creek Bridge will be located approximately 400 feet north of White River Bridge, on the north side of White River Valley. The potential for debris flow lateral loading to occur at Green Apple Creek Bridge is considered to be the same as or possibly less than the potential for debris flow loading at White River Bridge; therefore, lateral load forces exerted by debris flows debris are not expected to be sufficient to control the foundation design for Green Apple Creek Bridge.

8. DRILLED SHAFT FOUNDATION ANALYSIS AND DESIGN

8.1 Scour Recommendations

The Preliminary Bridge Layout for the Green Apple Creek Bridge shows the channel elevations at the upstream and downstream ends of the bridge to be 4236 and 4231 feet, respectively. Based on analyses performed by the WFLHD’s Hydraulics Section, the following scour depths and elevations were recommended for both the White River and Green Apple Creek Bridge drilled shaft foundations:

• Scour elevation at bridge piers: 4200 feet.

• Scour elevation at bridge abutments: 4225 feet.

The estimated scour elevation of 4200 feet at the pier locations is based on a glacial outburst of 20,000 cfs, past debris removal operations, and a qualitative assessment of debris-related erosion (Browning, 2008).

8.2 Earthquake Effects

Seismic sources that contribute to the regional seismic hazard include shallow crustal sources (local faults and gridded seismicity) and Cascadia Subduction Zone interplate (mega-thrust) earthquakes.

The procedures outlined in Section 3.10 of the 4th Edition of the LRFD Manual with the 2008 Interims were followed to characterize the seismic hazard. (Note that these procedures use a design earthquake with a return period of 1000 years, or a 7 percent probability of exceedance (PE) in 75 years. This is a departure from previous AASHTO Specifications which used a design earthquake with a return period of 500 years, or a 10 percent PE in 50 years.) The USGS interactive deaggregation website was used to determine the peak ground acceleration and spectral accelerations. The results of the hazard analysis are presented in Table 2.

Table 2. Summary of Seismic Parameters (7% PE in 75 years).

Site Class (by Soil Type and Profile) C – very dense soil

Horizontal Peak Ground Acceleration (PGA) 0.166g

Horizontal Response Spectral Acceleration at Period of 0.2 sec (Ss) 0.392g

Horizontal Response Spectral Acceleration at Period of 1.0 sec (S1) 0.142g

As 0.199 g

SDS 0.470 g

SD1 0.236 g

Seismic Zone 2

The values in Table 2 were used to develop the 5-percent-damped-design response spectrum shown in Figure 3 below.

Figure 3. 5-Percent-Damped-Design Response Spectrum.

The Green Apple Creek foundation report from this point on has not been completed; however, boring locations, boring logs, and core photographs for the Green Apple Creek foundation investigation are contained in Appendices A, B, and C, respectively.

The reader may refer to Preliminary Geotechnical Report No. 01-09, “Oregon Highway 35 White River Bridge Replacement Foundation Investigation”, for a discussion of foundation conditions at White River Bridge that are anticipated to be similar to the foundation conditions at Green Apple Creek Bridge, and preliminary foundation considerations at Green Apple Creek Bridge can be based on the preliminary White River foundation report;

however, the user of the White River foundation report is cautioned that the foundation recommendations for Green Apple Creek Bridge may differ substantially from the recommendations presented in Preliminary Geotechnical Report No. 01-09.

8.3 SPT N-Value Corrections

The SPT N-values obtained from the Green Apple Creek subsurface borings were corrected for hammer energy and overburden pressure to determine the N60 values and the (N1)60 values. N60 values were corrected for hammer efficiency only. (N1)60 values were corrected for hammer efficiency and overburden pressure. The corrected N60 and (N1)60 values are contained in spreadsheet format in Appendix D. The (N1)60 values were averaged in 5-foot layers to produce a chart of average (N1)60 versus depth shown in Figure 4 below.

Figure 4. Corrected SPT (N1)60 Values Plotted Versus Depth.

8.4 Liquefaction

The procedures outlined in Subsection 6.5.2 of the Oregon Department of Transporation (ODOT) Geotechnical Design Manual (2008) were generally followed in order to assess the liquefaction potential at the site.

8.6 Drilled Shaft Analysis and Design

The proposed bridge will be a three span structure with a 115 foot-long main span and an 86 foot-long span at each end. The distance from the proposed bridge deck elevation to the scour elevation is about 50 and 75 feet at the abutments and piers, respectively. As discussed in Section 6, drilled shafts were selected over spread footings and driven piling as the preferred foundation type because drilled shafts can be more easily constructed to transmit loads below the scour elevation and they have relatively higher lateral load capacity than driven piles.

8.6.a Design Loads

8.6.b Preliminary Drilled Shaft Recommendations

Table 5. Preliminary Drilled Shaft Recommendations.

8.6.c Settlement

The estimated settlement at the top of the drilled shafts due to the working loads (DL + LL) listed in Subsection 8.6.a is up to 0.5 inches for the diameters and uppermost tip elevations of drilled shafts presented in Table 5. Charts of settlement versus load are presented in Appendix G following each bearing capacity chart. The settlement charts include scour and present settlement estimates for both the uppermost and lowest tip elevation listed in Table 5.

8.6.d Lateral Analysis

Lateral loads were not provided, but they are anticipated to be significant due to the seismic hazard at the site. Seismic lateral load analysis is an extreme event limit state so scour is not included in the analysis.

Table 6 provides the soil parameters that are recommended to analyze lateral foundation loads. The values in Table 6 do not include factors of safety or load factors. A resistance factor of 1.0 is specified in AASHTO (2008) for horizontal geotechnical resistance of a single shaft or shaft group.

Table 6. Recommended Soil Parameters for Lateral Analysis.

9. DRILLED SHAFT CONSTRUCTION CONSIDERATIONS

Based on both surface observations of the White River channel and adjacent flood plain and the subsurface investigation borings, it is anticipated that boulders at least as large as 6 feet in diameter may be encountered during the drilling and installation of drilled shaft foundations at the new White River bridge. The contractor should be prepared to remove boulders that are encountered during shaft installation that impede or prevent advancement of the shaft by approved methods.

The soils encountered in the borings will cave if excavated with an open hole. Full depth temporary casing or drilling slurry must be used to protect the side walls of the drilled shaft excavation during construction. The drilled shaft design includes a significant amount of skin friction along the sides of the drilled shaft. Therefore, any temporary casing must be removed from the completed drilled shaft. Very permeable layers of coarse gravel, cobbles and boulders are likely to be encountered which may exclude the use of drilling slurry. The contractor should consider the subsurface conditions carefully when choosing the method of drilled shaft construction. Wet methods of construction will be necessary. An adequate head of water (casing method) or drilling slurry should be maintained inside of the drilled shaft excavation to prevent heaving of the soils at the bottom of the excavation.

Cross-hole Sonic Logging (CSL) should be completed on each drilled shaft to insure the integrity of the shaft. Each rebar cage should include one CSL access tube per foot diameter of drilled shaft (i.e., at least 8 CSL access tubes for an eight-foot diameter drilled shaft). The access tubes should be spaced evenly on the rebar cage and securely fastened to either the inside or outside of the cage.

The WFLHD Geotechnical Team should be part of the reviewing effort of the contractor’s drilled shaft submittals to evaluate shaft design and construction appropriateness based on the subsurface conditions. A member of the Geotechnical Team should also be present during excavation of the drilled shafts to ensure that the subsurface conditions are consistent with the materials encountered in the subsurface exploration.

10. APPROACH EMBANKMENTS AND ABUTMENT BACKFILL

The approach embankment will likely be constructed with nearby material deposited during the 2006 debris flow event consisting of gravelly sand and cobbles or with shot rock material from a nearby Forest Service quarry. These materials are adequate for use as backfill and fill behind abutments and wing walls; however, the material should be screened with a grizzly or by other means to remove particles greater than 6 inches in size. A perforated corrugated polyethylene drain should be installed behind walls to ensure drainage. The soil parameters listed in Table 7 may be used to determine the lateral earth pressures exerted on the abutment walls and wing walls.

Table 7. Recommended Soil Parameters for Abutment Wall Design.

Parameter Design Value* Moist Unit Weight 130 pcf

Angle of Internal Friction 34 degrees

Active Earth Pressure Coefficient, Ka 0.28

Active Equivalent Fluid Pressure 36 psf/ft

At-Rest Earth Pressure Coefficient, K0 0.44

At-Rest Equivalent Fluid Pressure 57 psf/ft

Passive Earth Pressure Coefficient, Kp 3.54

Passive Equivalent Fluid Pressure 460 psf/ft

Wall-Backfill Interface Friction Angle, δ 26 degrees

*Design values based on a drained condition behind the wall.

The above values do not include factors of safety or load factors. Appropriate factors of safety or load factors should be used with these parameters. It is generally assumed that compacted backfill creates at-rest lateral earth pressure behind unyielding walls and that a slight movement at the top of the wall (0.002 x wall height) creates active lateral earth pressures behind walls. When passive lateral earth pressures are applicable, wall movements of 0.02 x wall height at the top of the wall are necessary to reach the earth pressures listed above.

The procedures outlined in Appendix A11 of LRFD (2008) should be used to determine the seismic forces exerted on the walls. Once the wall geometry is determined, the Geotechnical Team can assist in development of the seismic active pressure.

Embankments constructed with these materials can safely be constructed as steep as 1V:1.5H. However, embankments constructed 1V:2H or steeper with the nearby sandy gravel material will be highly susceptible to erosion and shallow failures during spring thaw and periods of heavy precipitation. Embankment protection (riprap or shot-rock) or aggressive revegetation and erosion control will be needed to protect slopes 1V:2H or steeper.

10. USE OF THIS REPORT

Professional judgments and recommendations are presented in this report. They are based partly on evaluation of the technical information gathered, partly on historical reports and partly on the WFLHD Geotechnical Team’s general experience with subsurface conditions in the area. It should be noted the borings might not represent potentially unfavorable subsurface conditions between borings. If, during construction, soil conditions are encountered that vary from those discussed in this report or historical reports, or if design loads and/or configurations change, the Geotechnical Team should be notified immediately in order that it may evaluate effects, if any, on foundation performance.

For questions regarding this report, please contact WFLHD Engineering Geologist Dave Lofgren at 360-619-7706 (david.lofgren@fhwa.dot.gov) or WFLHD Geotechnical Engineer Brian Collins at 360-619-7657 (brian.collins@fhwa.dot.gov).

11. REFERENCES

AASHTO LRFD Bridge Design Specifications 2008 Interim Revisions (2008) American Association of State Highway and Transportation Officials, Washington, D.C.

Briaud, J.-L. (1989) The Pressuremeter Tests for Highway Applications, Report No.

FHWA-IP-89-008, Federal Highway Adminsitration, McLean, Virginia, 156p.

Browning, M.C. (2008) November 6 Memorandum to Khoa Nguyen, Bridge Engineer, with subject heading “Hydraulic Information, White River Bridge, Highway 35, PFH 49, Oregon”, 8p.

ODOT Geotechnical Design Manual (2008) Oregon Department of Transportation, Technical Services Branch, Geo-Environmental Section, 325 p.

O’Oneil, M. W., and Reese, L. C. (1999) Drilled Shafts: Construction Procedures and Design Methods, FHWA Report No. FHWA-IF-99-025, Federal Highway Administration, Washington, D.C., 758 p.

Reese, L.C., Wang, S.T., Isenhower, W.M., and Arrellage, J.A. (2004) Computer Program LPILE Plus Version 5.0 Technical Manual, Ensoft, Inc.

U.S. Geological Survey, USGS Earthquake Hazards Program website, 2002 Interactive Deaggregations, http://eqint.cr.usgs.gov/deaggint/2002/index.php, accessed August 4, 2008. Draf

APPENDIX A

Preliminary Bridge Layout with Boring Locations

PLAN

SHEET

NUMBER

OR

FS ERFO 2007(1)-11(2)

_DATE_" + "_FILE_C:\Myfiles\PW_Production\dms06131\Green_Apple_Bridge_Borings.dgn

PROJECTSTATE

Checked by:Designed by:

PRELIMINARY GREEN APPLE

BRIDGE LAYOUT

SHOWING APPROXIMATE

BORING LOCATIONS

Scale in feet

30 0 30 60

N

GA-13

GA-14

GA-15

APPENDIX B

Boring Logs

APPENDIX C

Core Photographs

Green Apple Creek Boring GA-13, 0.0-29.5 feet depth

Green Apple Creek Boring GA-13, 29.5 – 44.5 feet depth

Green Apple Creek Boring GA-13, 44.5 – 59.0 feet depth

Green Apple Creek Boring GA-13, 59.0 – 79.5 feet depth

Green Apple Creek Boring GA-13, 79.5 - 99.5 feet depth

Green Apple Creek Boring GA-14, 0.0 – 34.5 feet depth

Green Apple Creek Boring GA-14, 34.5 – 50.0 feet depth

Green Apple Creek Boring GA-14, 50.0 – 61.0 feet depth

Green Apple Creek Boring GA-14, 61.0 – 80.0 feet depth

Green Apple Creek Boring GA-15, 5.0 – 34.0 feet depth

Green Apple Creek Boring GA-15, 34.0 – 49.5 feet depth

Green Apple Creek Boring GA-15, 49.5 – 62.0 feet depth

Green Apple Creek Boring GA-15, 62.0 – 80 feet depth

Green Apple Creek Boring GA-15, 80.0 – 100.0 feet depth

APPENDIX E

Unified Soil Classification System (USCS)

APPENDIX F

SPT N-Value Corrections

APPENDIX G

Drilled Shaft Design Charts