FA520525R0002_Atch6_Geotechnical Investigation Report_10Oct23.pdf

Geotechnical Investigation Report

Design – Add/Repair Fitness Center B620 & B622, Misawa Air Base, Japan

35th Contracting Squadron ESC Project No.8218

10 October 2023

Prepared For:

Prepared By:

1392090220U Text Box Attachment 6 to RFP No. FA520525R0002

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Geotechnical Investigation Report i Design-Add/Repair Fitness Center B620 and B622, MAB

EXECUTIVE SUMMARY

OTIE tasked Environmental Science Corporation (ESC) to conduct a geotechnical investigation in support of the Design-Add/Repair Fitness Center, B620 and B622 projects at the United States Air Force (USAF) Misawa Air Base (MAB) in Aomori Prefecture, Japan. These projects were awarded to OTIE by the MAB 35th Contracting Squadron to complete Ready-To-Advertise design packages for Opportunity No. 1072225 (Legacy No. QKKA 161026) and Opportunity No. 1072264 (Legacy No. QKKA 171017) for Buildings (Bldgs.) 620 and 622, respectively.

The project site is located south of the MAB airfield within the existing Potter Fitness Center, which is comprised of three interconnected buildings (Bldgs. 620, 622, and 625).

This geotechnical report addresses the results of investigative soil borings, field testing and soil laboratory analysis performed for this project and provides geotechnical recommendations in support of the design of the foundations for the new building additions and associated infrastructure at the existing Fitness Center Bldgs. 620 and 622.

The geotechnical investigations included 2 soil borings, and several field and laboratory tests. In total, approximately 36 meters (m) of soil boring/soil investigation were conducted along with soil sampling of representative soil layers in order to determine their engineering characteristics.

Geologic Site Hazards and Site Class

Subsurface and terrain conditions indicate that the site soil is not susceptible to liquefaction and slope failure hazards are not expected at project site.

Soil laboratory results and guidelines from the Soil Investigation Testing Results Interpretation and Analysis Manual published by the Japan Geotechnical Society (JGS) and the US National Association of Corrosion Engineers (NACE), suggest that severe corrosive environments for concrete and ferrous materials are not anticipated at the site.

The seismic site class for the soils in the project site is “D”. This determination was based on shear wave velocities (Vs) measured by ESC in a past project in MAB and published Vs data for MAB.

Details on geological site hazards and site class determination are described in Sections 5.2 and 5.3 of this report, respectively.

Site Subsurface Conditions

Exploratory borings showed that the site soils consist mainly of fill layers composed of silty clay, organic soils locally known as “kuroboku”, sandy loam, and fine sand soils.

Fill layers were composed of silty clay mixed with organic material locally known as “kuroboku”.

Underlying the fill was a thin layer of kuroboku soil characterized by medium water content and high plasticity. Dark brown loam was encountered beneath the kuroboku layer and consisted of

Geotechnical Investigation Report ii elastic silts with low SPT N-values ranging from 1 to 3 which indicates very soft to soft consistencies for fine-grained soils. The soil classification is Elastic Silt with Sand (MH) according to ASTM D2487.

Underlying the loam, thick layers of sand soils were encountered from 6 m below ground surface (bgs) which extended to the bottom of the borings. SPT N-values ranged from 14 to greater than 50 which indicates medium dense to very dense densities for granular soils.

Groundwater was not observed in the conducted soil borings.

Foundation Recommendations

Recommendations presented in this report assume that the finish floor elevation (FFE) for the new building additions may be similar to the existing building’s FFE. Similarly, it is assumed that the new ground elevation will not be changed and be maintained at an elevation of approximately between 38.5 to 39 m above mean sea level (MSL). These assumptions imply that no significant loading due to new fill placement will be applied to the site soils.

It is our understanding that the project’s structural engineers want to match the foundation types of the new building additions to the foundation types of the existing buildings.

As-built drawings for the gymnasium addition in Bldg. 620 dated January 1977 indicate that the additions are supported on shallow foundations.

As-built drawings for the original gymnasium building dated January 1986 show that the building is supported on pile foundations.

Along with recommendations for shallow and pile foundations, recommendations for soil improvements by means of soil-cement columns (SCC) are also presented in this report.

Details for foundation recommendations are included in Sections 7.1 to 7.5 of this report.

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CONTENTS

EXECUTIVE SUMMARY ............................................................................................................ i

ACRONYMS AND ABBREVIATIONS ..................................................................................... vi

1.0 INTRODUCTION

2.0 SITE OVERVIEW

3.0 SITE GEOGRAPHICAL AND GEOLOGICAL FEATURES

4.0 PROJECT CONSIDERATIONS

5.0 SITE CONDITIONS

5.1 Subsurface Conditions

5.1.1 Subsurface Profile of the Site

5.1.2 Groundwater

5.2 Geological Site Hazards

5.2.1 Soil Liquefaction

5.2.2 Potential Slope Failures

5.2.3 Corrosive Soil Environments

5.3 Site Class Designation

5.4 Subsurface Variations

6.0 FIELD AND LABORATORY TESTING EFFORTS

6.1 Soil Borings and Standard Penetration Testing (SPT)

6.2 Geotechnical Field Testing

6.2.1 Soil Electrical Resistivity Test

6.2.2 Pressuremeter Test (Lateral Loading Test [LLT])

6.3 Soils Laboratory Testing

7.0 CONCLUSIONS & RECOMMENDATIONS

7.1 Considerations for Foundation Recommendations for Building Additions

7.2 Foundation Recommendations for Building Additions at Bldg. 620

7.3 Foundation Recommendations for Building Additions at Bldg. 622

7.4 Soil Improvements Option

7.5 General Recommendations for Foundations, Slab-on-Grades and Subgrade

Preparation

7.6 Pavement Recommendations

7.6.1 Rigid and Flexible Pavement Recommendations

7.7 Soil Materials for Pavements

7.8 Site Drainage

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8.0 CONSTRUCTION CONSIDERATIONS

8.1 Earthwork, Grading and Backfill

8.2 Excavation and Trenching

9.0 DISCLAIMER

10.0 REFERENCES

TABLES

TABLE 1: SUMMARY OF TESTS FOR SOIL CORROSIVITY POTENTIAL

TABLE 2: CORROSIVITY RATINGS ACCORDING TO NACE GUIDELINES

TABLE 3: SOIL BORING AND SAMPLING COORDINATE LOCATIONS SUMMARY

TABLE 4: SUMMARY OF FIELD SOIL RESISTIVITY TEST RESULTS

TABLE 5: SUMMARY OF LLT RESULTS

TABLE 6: SOIL PHYSICAL PROPERTIES LABORATORY TEST RESULTS

TABLE 7: UNCONFINED COMPRESSION TEST RESULTS

TABLE 8: UNCONSOLIDATED UNDRAINED (UU) TRIAXIAL TEST RESULTS

TABLE 9: DESIGN CBR RESULTS

TABLE 10: ALLOWABLE AXIAL CAPACITY FOR HELICAL STEEL PILES

TABLE 11: TRAFFIC CONSIDERATIONS FOR FLEXIBLE PAVEMENT

RECOMMENDATIONS

TABLE 12: TRAFFIC CONSIDERATIONS FOR RIGID PAVEMENT RECOMMENDATIONS

TABLE 13: AC AND PCC PAVEMENT RECOMMENDATIONS

TABLE 14: COMPACTION REQUIREMENTS

TABLE 15: LIFT THICKNESS REQUIREMENTS FOR BACKFILL COMPACTION

FIGURES

FIGURE 1. SITE LOCATION MAP

FIGURE 2. GEOLOGICAL MAP OF SITE

FIGURE 3. GEOTECHNICAL INVESTIGATIVE LOCATIONS MAP

FIGURE 4. CONCEPT SITE PLAN – B620

FIGURE 5. CONCEPT SITE PLAN – B622

FIGURE 6: HELICAL PILE INSTALLATION PROCEDURE

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FIGURE 7: JIS DESIGNATED ENGINEERED BASE & SUBBASE MATERIALS FOR

PAVEMENTS

APPENDICES

A SOIL BORING LOGS

B PRESSUMETER (LLT) TEST RESULTS

C GEOTECHNICAL LABORATORY TEST REPORTS

D GEOTECHNICAL FIELD WORK PHOTOGRAPHS

E Vs SUPPORTING DATA

F PCASE OUTPUTS

G PRODUCT CATALOG OF HELICAL PILES

H PRODUCT CATALOG OF SOIL-CEMENT COLUMNS (SCC)

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ACRONYMS AND ABBREVIATIONS

ASTM American Society for Testing and Materials bgs Below ground surface Bldg Building CBR California Bearing Ratio cm Centimeter ESC Environmental Science Corporation FFE Finish Floor Elevation FY Fiscal Year H:V Horizontal : Vertical JGD Japan Geodetic Datum JGS Japan Geotechnical Society JIS Japan Industrial Standard JRA Japan Road Association km Kilometer km2 Square kilometer MAB Misawa Air Base KN Kilo Newton KN/m2 Kilo Newton per square meter KPa Kilopascals m Meter m2 Square meter mi Mile mi2 Square mile MN/m3 Mega Newton per cubic meter mm Millimeter MPa Mega Pascal MSL Mean sea level (Above) MPa/m3 Mega Pascal per cubic meter N Blow count of the Standard Penetration Test NACE US National Association of Corrosion Engineers NAVFAC Naval Facilities Engineering Command OSHA Occupational Safety & Health Administration QC Quality Control SOW Scope of Work SPT Standard Penetration Test

sq. m Square meters SCC Soil-Cement Columns UFC Unified Facilities Criteria UFGS Unified Facilities Guide Specifications US United States

Geotechnical Investigation Report 1

1.0 INTRODUCTION

OTIE tasked Environmental Science Corporation (ESC) to conduct a geotechnical investigation in support of the Design-Add/Repair Fitness Center, B620 and B622 projects at the United States Air Force (USAF) Misawa Air Base (MAB) in Aomori Prefecture, Japan. These projects were awarded to OTIE by the MAB 35th Contracting Squadron to complete Ready-To-Advertise design packages for Opportunity No. 1072225 (Legacy No. QKKA 161026) and Opportunity No. 1072264 (Legacy No. QKKA 171017) for Buildings (Bldgs.) 620 and 622, respectively.

This geotechnical report addresses the results of investigative soil borings, field testing and soils laboratory analysis performed for this project and provides geotechnical recommendations in support of the design of the foundations for the new building additions and associated infrastructure of the existing Fitness Center Bldgs. 620 and 622

The following describes the major work tasks associated with the contracted geotechnical investigation for this project:

• Completed 2 non-core soil borings with Standard Penetration Tests (SPT), field testing and soil sampling in order to verify subsurface conditions at the site from 04 to 07 October 2022.

• Soil samples were taken at characteristic soil layers from the conducted soil borings. In total, 9 disturbed and 3 undisturbed soil samples were taken and analyzed for physical and engineering soil properties. All samples were taken under the supervision of the ESC project’s geotechnical engineer. Soil samples were tested for the following characteristics by applicable American Society for Testing and Materials (ASTM), Japan Industrial Standard (JIS) and Japan Geotechnical Society (JGS) methodologies:

Classification of Soils (ASTM D 2487 / JGS 0051) Particle Size Analysis (JIS A 1204, JIS A 1223) Density of Soil Solid particles (JIS A 1202) Moisture Content (JIS A 1203) Liquid and Plastic Limit (JIS A 1205) Unconfined Compression Test (JIS A 1216, JGS 0511) Unconsolidated Undrained Triaxial Compression Test (JGS 0521) pH (JGS 0211) Water Soluble Chlorides and Sulfates (JGS 0241) Soil Electric Conductivity (JGS 0212)

• One bulk soil sample within the project site was collected for the following geotechnical test:

California Bearing Ratio (CBR) (JIS A 1211, JGS 0721)

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• In addition, the following geotechnical field tests were conducted:

One-dimensional (1-D) electric resistivity using the Four Point Wenner Method Pressuremeter (Lateral Loading Test [LLT)]) (JGS 1531)

• Review of as-built drawings and other available geotechnical information near the project site.

• Engineering analysis of the field exploration and results of field and laboratory testing data.

• Provided geotechnical recommendations to support the foundation design for the new additions of the existing Fitness Center Bldgs. 620 and 622.

• Provided pavement design recommendations for flexible and rigid pavements at the site.

• Provided construction considerations related to earthwork, site grading and site drainage.

Soil boring logs, soil laboratory testing reports, and field photographs are included in the report appendices.

2.0 SITE OVERVIEW

The project site is located south of the MAB airfield, Aomori, Japan. The site covers a total area of approximately 9,400 square meters (m2) of land and is located in a relatively flat area, with an approximate elevation of 39 meters (m) above mean sea level (MSL). The site location is shown in Figure 1.

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Figure 1. Site Location Map

Project Site

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3.0 SITE GEOGRAPHICAL AND GEOLOGICAL FEATURES

The project site is located in the Tohoku region of Japan, approximately 576 kilometers (km) northeast of central Tokyo in Misawa City, Aomori Prefecture, the northernmost prefecture of Honshu Island. Misawa City faces the Pacific Ocean and is bordered in the west-northwest by Lake Ogawara. The Ou Mountain range (also called Ou Backbone Range) is also west of Misawa City.

The Tohoku region has undergone numerous geomorphic changes due to plate tectonics, volcanic activity, fluvial dissection, and coastal inundation from glaciation-related global sea level changes (Miyauchi, 1987). The geology surrounding the site is composed of primarily several Pleistocene terrace formations on top of a pumiceous yellow sandstone and ash-blue-grey silty mudstone bedrock (Japan Ministry of Construction, 1970).

The highest of the terraces surrounding the site, known as the Tengutai terrace, formed during the middle Pleistocene period and ranges in elevation from 50-100 m above MSL. The deposits of the Tengutai terrace are approximately 15 m thick and consist of sand with trace fossils. The project site is situated on this terrace.

The middle terrace is known as the Takadate terrace and ranges in elevation from 20 to 50 m above MSL. This terrace is younger than the Tengutai, having formed in the late Pleistocene. The deposits of the Takadate terrace consist of approximately 15 m of thick sand and gravel with trace fossils. In the northern portion of the terrace, oyster bed fossils have been observed within mud layers and are presumed to be associated with rapid sea-level rises throughout the Pleistocene period (Miyauchi, 1987).

The lower terrace, known as the Shibayama terrace, formed in the late Pleistocene to early Holocene period and is found along the shores of the surrounding water bodies and even adjoins the Pacific Ocean on the eastern side of the Takadate terrace. The deposits of the Shibayama terrace are composed of several layers of both marine and non-marine sediments (Miyauchi, 1987). The Shibayama terrace elevations range from 10 to 30 m above MSL but typically do not exceed 10 m.

The mud and clay layers in this terrace are rich in organic colors from dark yellowish browns to greys and blues and contain trace fossils of humic plants and shellfish. These mud and clay layers are deposited above a coarse sandy-gravel layer that resides on top of the older bedrock.

Throughout the local river basins and along Ogawara Lake, an older sandy layer can be found below the deposits of the Takadate terrace called the Numasaki Formation. This sandy layer can reach thicknesses of up to 150 m and is believed to have formed during the Pliocene to early Pleistocene period as a result of erosion due to regional and glaciation-related global sea level changes.

A site geological map is shown in Figure 2.

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Figure 2. Geological Map of Site

(Source: Geological Survey of Japan, AIST 2015)

Takadate Terrace

Shibayama Terrace

Site

Tengutai Terrace

Numasaki Formation

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4.0 PROJECT CONSIDERATIONS

According to the DD Form 1391 for Bldgs. 620 and 622, dated April 2022, these projects will address various facility deficiencies due to deteriorating conditions and obsolescence.

The renovations to each building will accommodate Air Force Services Activity physical fitness standards and modern design standards. The building renovations will include architectural improvements such as installation of new insulation assemblies, replacement of all interior walls and floor and ceiling finishes, removal and replacement of all existing doors, door frames, door hardware, caseworks, and cabinetries, and removal of all floor finishes including substrate to reveal the floor structure.

The existing footprint will also be expanded to accommodate mechanical equipment (Bldg. 620) and storage (Bldg. 622). The new mechanical room addition will be constructed at the southwest corner of Bldg. 620 after the demolition of the existing metal building and exterior stairs. The new storage room will be constructed in an open space area at the northwest corner of Bldg. 622. A seismic isolation joint will be installed between the new building additions and the existing buildings. Additionally, the foundation of both buildings will be investigated where concerns exist over poor soil conditions due to earthquakes.

As-built drawings for the gymnasium addition for Bldg. 620 dated January 1977 indicate that the additions are supported on shallow foundations designed with a low allowable bearing pressure of 1,200 psf (58 kPa). The embedment depth of footings is approximately 1.2 m below the existing grade or the finish floor elevation (FFE). The gymnasium addition is a steel frame structure with a metal roof.

As-built drawings for the original gymnasium at Bldg. 622 dated January 1986 show that the building is supported on pile foundations. Piles are precast concrete piles of 300 mm diameter.

Pile lengths are 6 m with a top of the pile located at approximately 1.5 m bgs (toe of the pile at approximately 7.5 m bgs). Allowable pile capacity is 35 metric tons (350 kN). It appears that the piles were designed considering end-bearing conditions only. Piles were installed using pile driving methods. The gymnasium building is a 2-story concrete frame building with a metal roof supported on concrete beams. Administrative office areas are 1-story concrete frame buildings with concrete roofs.

Soil borings at 2 locations (one for each building), CBR sampling at 1 location, and field and laboratory tests were conducted within the project site. Figure 3 shows the approximate geotechnical investigative locations in relation to current site conditions. Figures 4 and 5 show the concept site plans for both buildings prepared by the OTIE design team.

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Figure 3. Geotechnical Investigative Locations Map

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Figure 4. Concept Site Plan – B620

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Figure 5. Concept Site Plan – B622

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5.0 SITE CONDITIONS

5.1 SUBSURFACE CONDITIONS

A general description of the subsurface conditions and various geo-materials encountered during our field exploration at the site are presented in this section.

5.1.1 Subsurface Profile of the Site

Exploratory borings showed that the site soils consisted of upper layers of silty clay fill followed by organic soils and loam overlying thick layers of sand soils.

Fill layers were composed of silty clay mixed with organic material locally known as “kuroboku”.

The thickness of the fill soil layers is 1.5 m on average. SPT N-values were less than 10.

Underlying the fill was a thin layer of kuroboku soil characterized by medium water content and high plasticity. According to ASTM D2487, the soil is classified as Sandy Elastic Silt (MH). The soils in this layer were dark brown in color with an average unit thickness of 0.38 m.

Dark brown loam was encountered beneath the kuroboku layer and consisted of silts with low SPT N-values ranging from 1 to 3 corresponding to very soft to soft fine-grained soils. The soil classification is Elastic Silt with Sand (MH). Pebble gravel (4.75 to 5 mm size particle) and fine sand were encountered at depth. Layer thicknesses were approximately 4.3 m.

A thick layer of sand was underlying the loam soils. The sand layer was encountered below 6 m bgs and extended to the bottom of the borings. The sand was mostly fine and included a thin layer of pumice at depth (at 12 m and 15 m bgs in soil borings B-1 and B-2, respectively). The sand layer was poorly graded at soil boring B-1 and well-graded at soil boring B-2. SPT N-values ranged from 14 to greater than 50 corresponding to medium dense to very dense granular soils. At soil boring B-2, the upper section of the sand layer was composed of fine and medium sands mixed with gravels. Based on the ASTM D2487 soil classification, sand soil layers exhibit soils classified as Well-Graded Sand with Silt (SW-SM), Silty Sand (SM) and Poorly Graded Sand with Silt (SP-SM).

During the extraction of SPT soil samples, no visual or olfactory indication of soil contamination was noted by investigative personnel.

Distribution of the site subsurface soils can be referenced in soil boring logs included in Appendix A of this report.

5.1.2 Groundwater

Groundwater was not encountered in the conducted soil borings. However, due to the low permeability of the upper silty soils, perched groundwater may be encountered trapped within the silty soil layers after long and heavy rainfall events. Therefore, care shall be taken during construction to control groundwater in trenches, excavations, and pits. Minor dewatering operations may be required to drain these areas if water accumulation occurs.

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5.2 GEOLOGICAL SITE HAZARDS

Screening for geological site hazards to include site susceptibility to liquefaction, slope failure and soil corrosivity potential is analyzed in this section.

5.2.1 Soil Liquefaction

Liquefaction is defined as the phenomenon in which a cohesionless (generally sand) soil mass, generally within 20 m of the ground surface, suffers a substantial reduction in shear strength due to the development of excess pore water pressures. During earthquakes, excess pore water pressures in saturated loose cohesionless soil deposits may develop as a result of induced cyclic shear stresses, resulting in liquefaction. Soils that are most susceptible to liquefaction are clean, loose, saturated, uniformly graded, fine-grained sands that lie below the groundwater table with a depth ranging from 0 to 20 m bgs.

Based on the results from the exploratory soil borings, the site soils are mainly composed of soft to very soft loam layers overlying medium dense to very dense sand layers. Groundwater was not encountered in the conducted soil borings. Based on these soil conditions, the potential for liquefaction at the site is very low.

5.2.2 Potential Slope Failures

The site is located on a relatively flat terrace and does not present potential for slope failures. The project area is located at approximately 39 m MSL on a grassy area with no signs of slope failures or surface erosion.

At Bldg. 620 site, there is an existing retaining wall on the west side of the building. The elevation of the top of the wall is similar to the elevation of the building’s ground level. The difference in elevation between the top of the wall and the adjacent sidewalk is approximately 1.5 m. Site observations indicate that this retaining wall has been performing adequately and presents good structural conditions.

5.2.3 Corrosive Soil Environments

Environmental laboratory analyses to verify soil corrosivity potential were conducted for soil samples collected at representative soil layers located within 3 m bgs. Within this depth, it is expected that most utilities and concrete structures related to the foundations (footings, pile caps and grade beams) may be installed. Testing was performed by a local certified environmental laboratory located in Chiba Prefecture. Table 1 shows the laboratory test results for pH, chlorides and sulfates, and soil conductivity which were used to evaluate the corrosivity potential of the site soils. The soil corrosivity test results are referenced in Appendix C of this report.

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TABLE 1: SUMMARY OF TESTS FOR SOIL CORROSIVITY POTENTIAL

Boring Location / Depth

(m) bgs / Soil Type 2 pH

Water soluble chlorides (mg/kg)

Water soluble sulfates (mg/kg)

Soil conductivity 1

(mS/m)

Soil resistivity1 (ohm-cm)

B-1/ 1.5m bgs / Fill Material 7.5 22 57 2.47 40,486

B-1/ 1.35m-1.80m bgs / Organic Material

(Kuroboku)

7.2 11 56 2.65 37,736

B-1/ 2.15m-2.45m bgs/ Loam Soil 7.1 15 140 4.19 23,866

Notes:

1 Soil conductivity values were obtained from laboratory tests. Soil resistivity values were calculated using the measured soil conductivity values. Soil resistivity is the inverse of soil conductivity.

2 Soil description based on visual inspections.

The Soil Investigation Testing Results Interpretation and Analysis Manual published by the JGS in 1979 describes corrosive environments as those with the following characteristics:

a) Soil with soil conductivity values of greater than 200 mS/m

b) Soil with total chlorides exceeding 1mg/g (1000 mg/kg)

c) Soil with total sulfates exceeding 0.5mg/g (500 mg/kg)

d) Soils with pH values below 6 or over 9

The US National Association of Corrosion Engineers (NACE) provides guidelines for soil corrosivity ratings as indicated in the table below.

TABLE 2: CORROSIVITY RATINGS ACCORDING TO NACE GUIDELINES

Soil Resistivity (ohm-cm) Corrosivity Rating

>20,000 Essentially non-corrosive

10,000 to 20,000 Mildly corrosive

5,000 to 10,000 Moderately corrosive

3,000 to 5,000 Corrosive

1,000 to 3,000 Highly corrosive

<1,000 Extremely corrosive

Based on the JGS and NACE guidelines, the results of soil corrosivity potential falls within the threshold range for non-corrosive soils for project site.

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Additional information and final determination of the soil corrosivity potential at the sites are included in Section 6.2.1 which includes the results of field electrical resistivity tests conducted at the site.

5.3 SITE CLASS DESIGNATION

The seismic site class for this site was determined in accordance with UFC 3-220-01, Geotechnical Engineering, dated 3 November 2021 and UFC 3-301-01, Structural Engineering, dated 1 October 2019.

UFC 3-220-01 requires the verification of the seismic site class by assessing the strength and stiffness of the subsurface profile to a depth of 30.5 m (100 ft) using one or more methods specified in the American Society of Civil Engineers (ASCE) 7-16 (Minimum Design Loads and Associated Criteria for Buildings and Other Structures). Per ASCE 7-16, the seismic site classification can be determined by the verification of the average Shear Wave Velocities (Vs), SPT N-values or Undrained Shear Strengths (Su) for a depth of 30 m.

Based on previous geotechnical investigations conducted in MAB, since it was noted that the SPT introduces disturbance in soils which may underestimate the soil parameters, the seismic site classification for this project was based on the average Vs measured by ESC at a previous site close to the MAB Apple Gate (New Airfield Damage Repair [ADR] Facility – USACE JED project in 2019-2020). It can be noted that the project site and the ADR site present similar geologic settings and subsurface conditions. Laboratory testing performed for both projects confirmed that the type of soils and stratigraphy for both sites are very similar. The measured Vs obtained at the ADR site was consistent with published average Vs data in the upper 30 m of the soil profile from the Japan Seismic Hazard Information (J-SHIS). Vs data from the ADR site and the J-SHIS is included in Appendix E of this report.

The average Vs measured from the ADR site shown was approximately 296 m/s. The published Vs data by the J-SHIS shows a Vs of 246 m/s at the ADR site. The published Vs data by the J-SHIS at the MAB Fitness Center site shows a Vs value of 236 m/s. For an average Vs between 183 m/s and 366 m/s, ASCE 7-16 gives a seismic site classification of D.

Therefore, based on the above considerations, a seismic site class of D is recommended for this project.

5.4 SUBSURFACE VARIATIONS

Based on results of the subsurface exploration and our experience, some variations in the continuity and nature of subsurface conditions within the project site should be anticipated. Due to uncertainties in the nature and depositional characteristics of the earth material at the site, caution and engineering judgment must be exercised in interpolating or extrapolating subsurface conditions between or beyond the investigated boring locations.

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6.0 FIELD AND LABORATORY TESTING EFFORTS

6.1 SOIL BORINGS AND STANDARD PENETRATION TESTING (SPT)

Project field activities began with determining soil borings, soil sampling and field testing locations by the ESC field team. Approximate locations were positioned and staked at the site using a GPS equipment based on the concept design plans and discussions with the OTIE design team. The vertical and horizontal datum utilized for recording the geotechnical investigative locations is the Japan Geodetic Datum (JGD) 2011 Zone 10.

Soil borings and SPT were conducted at the site using a rotary drilling rig equipped with a 66-millimeter diameter hollow tube bit and a split spoon sampler. Wash boring drilling methods were used for this investigation. In total, 2 soil borings were conducted at the site, conducted to variable depths to confirm subsurface site conditions, with SPTs performed at one meter intervals. SPT was conducted in accordance with JIS A 1219 (the JIS equivalent to ASTM D1586), recording the total amount of blows required for the SPT tube bit to penetrate 30 cm of soil as a result of the impact of a 63.5 kg hammer from a free drop height of 76 cm.

In total, approximately 36 m of soil boring/soil investigation were conducted along with disturbed and undisturbed soil sampling of representative soil layers. Soils samples were analyzed at a local certified laboratory to determine their engineering characteristics.

Refer to Figure 3 and Table 3 which show the boring locations and depths. SPT N-values were evaluated along with soil testing data to provide foundation recommendations for the new expanding building. Foundation recommendations can be found in Section 7 of this report.

Boring logs and fieldwork photographs are included in Appendix A and D, respectively.

TABLE 3: SOIL BORING AND SAMPLING COORDINATE LOCATIONS SUMMARY

Soil Boring Location

Northing 1 (m)

Easting 1 (m)

Top of borehole elevation 1 (m MSL)

Boring Depth (m below ground surface [bgs])

B-1 77,381.583 44,288.246 38.51 15.45

B-2 77,362.911 44,298.895 38.91 20.40

Notes:

1 Coordinates are based on JGD 2011 Zone 10 Datum.

http://ja.wikipedia.org/wiki/%E6%97%A5%E6%9C%AC%E5%B7%A5%E6%A5%AD%E8%A6%8F%E6%A0%BC

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6.2 GEOTECHNICAL FIELD TESTING

6.2.1 Soil Electrical Resistivity Test

One-dimensional (1-D) soil electrical resistivity tests were conducted near Bldg. 622 by means of the Four-Point Wenner method, in accordance with ASTM G57. Electrical resistivity was measured along two survey lines oriented perpendicular to each other, with an electrode spacing of 1.5, 3, 4.5, 6, 7.5, and 9 m which corresponds to an increase in the investigated depths.

A summary of soil resistivity test results is shown in Table 4.

Electrical resistivity values range from 5,880 ohm-cm to 12,260 ohm-cm putting the soils in the range of “moderately corrosive” to “mildly corrosive” according to NACE guidelines.

Considering the field electrical resistivity survey results and the chemical and electrical conductivity measurements on the soil samples conducted at the laboratory, the soils at project site may present low soil corrosivity potential.

TABLE 4: SUMMARY OF FIELD SOIL RESISTIVITY TEST RESULTS

Tested Location

Electrode Spacing

(m) Resistance (ohms, Ω) Apparent Electrical Resistivity

(ohm-cm)

North-South

1.5 8.25 7,775

3 11.1 7,846

4.5 14.7 9,236

6 16.6 9,778

7.5 19.2 10,857

9 22.3 12,260

East-West

1.5 8.04 7,578

3 9.64 6,814

4.5 10.7 6,723

6 11.5 6,774

7.5 12.3 6,955

9 10.7 5,883

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6.2.2 Pressuremeter Test (Lateral Loading Test [LLT])

Two pressuremeter tests (Lateral Loading Tests [LLT]) were conducted, in accordance with JGS 1531, inside the boreholes B-1 at approximately 1.5 and 3.5 m bgs in order to verify the lateral modulus of subgrade reaction and modulus of elasticity of site soils.

A summary of LLT results is shown in Table 5. Field testing results are included in Appendix B of this report.

TABLE 5: SUMMARY OF LLT RESULTS

Boring Location / Depth Soil Type Lateral modulus of subgrade reaction Km (MN/m3) Pressuremeter Modulus

Em (MN/m2)

B-1 / 1.5 m bgs Sandy Elastic Silt (MH) 61.25 3.419

B-1 / 3.5 m bgs Elastic Silt (MH) 70.00 3.832

6.3 SOILS LABORATORY TESTING

In total, 9 disturbed soil samples and 3 undisturbed soil samples were taken at representative soil layers at selected boring locations and analyzed for physical and engineering soil properties. All samples were taken under the supervision of the ESC project geotechnical engineer. Disturbed samples were extracted using the SPT split spoon sampler or hand auger tools. Undisturbed samples were extracted using a rotary double-tube sampler.

Hand auger tools were used to collect one bulk sample at a depth of approximately 1 m bgs for CBR testing to provide flexible pavement and earthwork recommendations. Bulk sample was collected in a grassy area in between Bldgs. 620 and 622.

Samples of typical layers were tested in a local certified soils laboratory in accordance with relevant JIS and JGS testing procedures, as indicated in Section 1 of this report.

Tables 6 to 9 show a summary of laboratory test results. Soil laboratory test reports can be referenced in Appendix C of this report.

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TABLE 6: SOIL PHYSICAL PROPERTIES LABORATORY TEST RESULTS

Boring Location / Depth (m) bgs

Soil Classification (based on

ASTM D2487)

Sieve Analysis Distribution

Atterberg Limits

Water Content

Gravel Sand Silt Clay

LL PL PI >4.75

mm

4.75- 0.075 mm

0.075- 0.005 mm

<0.005 mm

B-1 / 1.35~1.80 Sandy Elastic Silt (MH) 0 34.4 49.4 16.2 66.2 49.9 16.3 57.1

B-1 / 3.15~3.45 Elastic Silt (MH) 0 13.5 41.6 44.9 76.0 43.4 32.6 82.0

B-2 / 1.35~1.80 Sandy Elastic Silt (MH) 0 32.2 39.3 28.5 84.9 58.9 26.0 61.0

B-2 / 2.00~3.00 Elastic Silt with Sand (MH) 0 25.5 55.3 19.2 87.3 60.6 26.7 83.4

B-2 / 6.35~7.00 Well-Graded Sand with Silt

(SW-SM) 6.0 53.2 3.5 3.0 NP NP NP 11.5

B-2 / 8.15~8.44 Well-Graded Sand with Silt

(SW-SM) 8.4 82.9 5.7 3.0 NP NP NP 10.8

B-2 / 13.15~13.45 Silty Sand (SM) 1.3 74.0 17.6 7.1 NP NP NP 28.3

B-2 / 17.15~17.45 Silty Sand (SM) 0 71.6 10.8 7.5 NP NP NP 20.2

B-2 / 20.15~20.40 Poorly Graded Sand with Silt (SP-SM) 0 88.5 6.2 3.9 NP NP NP 17.6

Abbreviations: LL: Liquid Limit; PL: Plastic Limit; PI: Plasticity Index; NP: Non-Plastic

TABLE 7: UNCONFINED COMPRESSION TEST RESULTS

Depth (m) bgs

Soil Classification Avg. Unconfined

Compressive Strength qu (kN/m2)

Avg Secant Modulus;

E50 (MN/m2)

B-2 / 2.00~3.00 Elastic Silt with Sand (MH) 122.95 6.26

B-2 / 4.00~5.00 Elastic Silt with Sand (MH) 44.30 1.89

TABLE 8: UNCONSOLIDATED UNDRAINED (UU) TRIAXIAL TEST RESULTS

Depth (m) bgs

Soil Classification Cohesion (kN/m2)

Undrained Friction Angle (°)

B-1 / 2.00~3.00 Elastic Silt with Sand (MH) 16.2 3.8

TABLE 9: DESIGN CBR RESULTS

Sample Location Soil Description Swelling Ratio (%) Average CBR (%)

C-1 Fill Material / Loam soil 0.026 2.1

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7.0 CONCLUSIONS & RECOMMENDATIONS

7.1 CONSIDERATIONS FOR FOUNDATION RECOMMENDATIONS FOR BUILDING ADDITIONS

Recommendations presented in this section assume that the finish floor elevation (FFE) of the new building additions may be similar to the existing building’s FFE. Similarly, it is assumed that the new ground elevation will not be changed and be maintained at an elevation of approximately between 38.5 to 39 m MSL. These assumptions imply that no significant loading due to new fill placement will be applied to the site soils.

It is our understanding that the project’s structural engineers want to match the foundation types of the new building additions to the foundation types of the existing buildings.

7.2 FOUNDATION RECOMMENDATIONS FOR BUILDING ADDITIONS AT BLDG. 620

As indicated in Section 4.0 of this report, the gymnasium addition for Bldg. 620 was supported on shallow foundations using an allowable bearing pressure of 1,200 psf (58 kPa). It is assumed that the original Bldg. 620 is also supported on shallow foundations. Embedment depths are approximately 1.2 m below the existing grade or the FFE of the existing building. Based on the conducted soil investigations, the bearing layer of shallow foundations of the existing Bldg. 620 may be composed of medium stiff or soft elastic silts soils (loam soils).

Due to the presence of thick layers of very soft to soft elastic silt within 6 m bgs, a conventional shallow foundation system for the new building additions may be designed using low allowable bearing pressures. An allowable net bearing pressure of 60 kPa is recommended for the design of square and continuous footings. Recommended minimum depth of footings (bottom of footing) is 1 m bgs. The recommended allowable bearing pressure is applicable to footings with maximum widths of 3 m and 2 m for square and continuous footings, respectively. Maximum and differential settlements are expected to be less than 25 mm and 12 mm, respectively.

A mat foundation system may also be considered for the building additions at Bldg. 620. The mat foundation may be found within 1 m bgs. Typically, mat foundations allow for larger settlements than footings. Mat foundations may allow for 50 mm and 20 mm for maximum and differential settlements, respectively. Based on these considerations and assuming a maximum width of 20 m for the new mat foundation, an allowable net bearing pressure of 40 kPa is recommended. The expected maximum total settlement based on this recommended allowable bearing pressure is on the order of 35 mm. If total settlements for the mat foundation are limited to 25 mm, the recommended allowable net bearing pressure will be 30 kPa. A modulus of subgrade reaction of 25 pounds per cubic inch (pci) (6.8 MN/m3) may be used for the structural design of the mat foundation.

Subgrade preparation under footings and mat foundations shall consist of replacing the existing subgrade soils with 300 mm thick engineered granular fill. It should be noted that based on UFC 3- 301-01, Structural Engineering, dated 1 October 2019, the frost penetration depth at MAB is 762

mm. Therefore, if a mat foundation system is implemented at the site, the bottom of the engineered granular fill layer shall be placed to a depth of at least 762 mm bgs.

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If the structural loads for the new building additions at Bldg. 620 will require larger soil capacities than the capacities presented in this section, the foundation recommendations presented in the following sections (helical piles and soil improvements) can be considered.

7.3 FOUNDATION RECOMMENDATIONS FOR BUILDING ADDITIONS AT BLDG. 622

The original Bldg. 622 is supported on precast concrete piles of 300 mm diameter. The allowable capacity of the piles is 350 kN. The toe of the piles is located at approximately 7.5 m below the existing grade or the FFE of the existing building. Based on the conducted soil investigations, the toe of the piles is bearing on layers of dense to very dense sands. Existing piles were installed using pile driving methods.

Due to site spacing constraints and proximity of the new building additions to the existing building, the installation of new precast concrete piles to support the new additions at Bldg. 622 may be difficult since they will require a large piling rig

Helical steel piles require smaller piling rigs and smaller workspace than concrete piles and are recommended to support the building addition at Bldg. 622. Typical dimensions of piling rigs used for the installation of helical piles are 2.5 m wide and 5.3 m long. A path with a width space of at least 3.5 m may be needed to maneuver the piling rig.

Helical steel piles are considered non-displacement piles which during their installation do not exert lateral pressures to adjacent soils. Also, due to the small size of the installation equipment rig, helical steel piles can be installed close to the existing building and therefore foundation eccentricities could be minimized. Typical closest distances from the face of the structure to the center of the helical piles depend on the size of the pile and it is in the order of 700 mm.

Helical piles shaft diameters and lengths may vary between 140 mm to 350 mm and between 2 m to 12 m, respectively. The production of helical piles in Japan is standardized by JIS A 5525 for welded steel pipe piles products. Typical steel grades for helical piles are locally identified as STK 400 and STK 490 which exhibit yield strengths of 235 MPa and 325 MPa, respectively.

The installation method starts setting the piling rig which will align and rotate the first piece pile of pile called as lower pile into the ground. The lower pile has helical blades on the tip which will be rotated by the auger located on the top of pile driver machine. After the first piece of pile is penetrated on the ground, the following number of extensions will be connected and welded until to reach the required torque or depth. Figure 6 displays a view of the basic step by step procedures for the installation of helical steel piles method.

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Figure 6: Helical Pile Installation Procedure

The helical piles are recommended to be bearing on dense to very dense sand soil layers with SPT N-value of 40+. The expected piles lengths are approximately 8 m (measured from the existing ground elevation - approximately 38.5 m to 39 m MSL). The pile tip should penetrate into the very dense sand soil to a minimum distance equal to the helical plate diameter. Based on these considerations, pile tips may be placed at an elevation of approximately 30.5 m MSL. It is assumed that the toe of the existing precast concrete piles was installed at a slightly higher elevation.

Recommendations for helical pile capacities are indicated in Table 10. The pile capacities are estimated based on a bearing layer with a SPT N-value of 50 and using a factor of safety of 3. Total settlements of less than 25 mm are expected for foundations supported on helical piles. A catalog of helical pile is referenced in Appendix G of this report.

For group of helical piles, center to center spacing is recommended to be a minimum distance equal to the sum of the shaft diameter plus the helical plate diameter.

Similarly, minimum distance from the existing precast concrete piles to the new helical piles shall be a distance equal to the sum of the shaft diameter plus the helical plate diameter or 750 mm, whichever is greater.

A mat foundation can also be considered as an alternative to helical piles for the foundations of the new building additions at Bldg. 622. The recommendations included in Section 7.2 for the mat foundation at Bldg. 620 are also applicable to Bldg. 622. Additional soil information for the design of mat foundations at Bldg. 622 such as soil dynamics properties can be provided later as the design evolves.

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TABLE 10: ALLOWABLE AXIAL CAPACITY FOR HELICAL STEEL PILES

Helical Pile Shaft Diameter

(mm)

Available Wall Thicknesses of Pile Shaft (mm)

Helical Plate Diameter

(mm)

Allowable downward pile capacity

(kN)

Allowable uplift pile capacity

(kN)

139.8 4.5, 6.6 350 185 85

165.2 5.0, 7.1 400 245 110

190.7 5.3, 7.0, 8.2

400 260 100

450 315 135

500 375 175

7.4 SOIL IMPROVEMENTS OPTION

Besides the foundation systems recommended above, soil improvements may also be a foundation option that may be considered for both Bldgs. 620 and 622. For the soil improvement option, soil-cement column (SCC) is the recommended technique for soil improvements under the new building additions. Shallow foundations consisting of conventional footings can be installed on top of the SCC. Allowable bearing pressures for the design of shallow foundation supported on SCC are recommended to be 200 kPa. A factor of safety (FOS) of 3 was used for calculating the recommended allowable bearing pressure. The recommended allowable bearing pressures are net pressures which result in calculated total and differential settlements of shallow foundations to be less than 25 mm and 15 mm, respectively.

The bottom of the SCC shall reach the layers of dense to very dense sands (SPT N-values of 40+) which were observed at an average elevation of 31.5 m MSL. Assuming that the bottom of the footings may be placed at 1 m below FFE, the lengths of the SCC may be on the order of 6 m (measured from the bottom of the footings).

SCC consists of soil-cement mixing operations which will improve the in-situ soft elastic silt soils by mixing the soils with a cementitious binder slurry using a rig equipped with a hollow-stem rotating shaft with a cutting tool at the tip and mixing paddles above the tip. A column of improved soil is constructed by a single stroke (penetration and withdrawal) of the deep mixing rig. Soil-cement mixing is applied to create a group of solid soilcrete columns that will support a conventional footing foundation. A medium size cement plant is required at the site in order to prepare and provide the cementitious binder slurry.

The minimum design compressive strength of SCC may be between 1,000 to 1,200 kPa. The required cement amount to reach these design strengths may be ranging between 200 to 400 kg/m3 with a water-cement ratio of 80%. Anticipated in-situ curing period of the SCC is about 3~5 days.

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As the design evolves, the final design compressive strength of SCC and the associated cement amounts can be refined. Available SCC diameters range between 600 mm to 1,800 mm.

A thin layer of 50 mm of lean concrete is recommended between shallow foundations and SCC in order to provide a workable surface for steel reinforcement placement. Minimum 28-days compressive strength of lean concrete is recommended to be 18 N/mm2.

In addition, Quality Control (QC) during construction is essential to ensure that soil improvement requirements are achieved, therefore an extensive QC program for soil improvement operations is required during the construction phase, as well as environmental testing required under Government of Japan regulations to verify that toxic hexavalent chromium from the cement curing does not leach into the site soils (hexavalent chromium threshold limit for leaching tests is 0.005 mg/L).

Visual inspections and unconfined compression tests for soil-mixings during and after placement may be included as part of the QC efforts during construction. Both QC activities and environmental testing are conducted by the installer and shall be supervised during construction operations. SCC mix design and implementation and QC procedures shall be in accordance with Japanese guidelines for the “Shinso Kongoshori Kouhou” (Deep Soil Mixing Method in English language) construction method as indicated by the Architectural Institute of Japan (“Nihon Kenchiku Gakkai”), The Building Center of Japan (“Nihon Kenchiku Centa”) or the Japan Cement Association (“Nihon Cemento Kyoukai”).

A product catalog for SCC is included in Appendix H of this report.

7.5 GENERAL RECOMMENDATIONS FOR FOUNDATIONS, SLAB-ON-GRADES AND SUBGRADE

PREPARATION

An increase of 1/3 of the recommended allowable bearing pressures and pile capacities can be considered for short-term loads such as earthquakes and transient wind loads.

Small concrete pads or foundations for small structures are recommended to be supported on shallow foundations following the recommendations indicated in Section 7.2 of this report.

Resistance to lateral loading may be provided by friction acting at the base of the shallow and mat foundations, and by passive earth pressure acting on the buried portions of shallow foundations and grade beams. A coefficient of friction of 0.35 can be considered acting between the shallow foundations and in-situ soils. Passive earth pressure may be computed as an equivalent fluid density of 30 kN/m3.

Regarding floor slab recommendations, a conventional slab-on-grade may be used for this project.

A modulus of subgrade reaction of 25 pci (6.8 MN/m3) may be used for the design of the slab-on-grade system. A layer of engineered granular fill of 300 mm thick is recommended underneath the slab-on-grade.

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It is assumed that since the new building additions will be for mechanical and storage rooms, radon mitigation systems may not be required however, if radon mitigation systems are required underneath the floor slabs, the system will require gas-permeable layers (GPL) underneath the floor slab. Soil materials for GPL should follow Table 2 of ASTM E1465-08a (typically ASTM C33 #6 soil or equivalent JIS standardized S-20 or S-40 soils as shown in Figure 7 of this report) and will depend on the type of radon system (GPL underneath the entire floor slab area or trenches filled with GPL), size of the perforated radon piping and local availability of GPL materials. A GPL with a thickness of 300 mm may be used underneath the floor slab. However, this thickness should be verified by the radon designer for considerations of the size of the radon piping system. In addition, the GPL may also serve as a capillary break layer which may contribute to protecting the floor slab against moisture. The GPL layer may replace the 300 mm thick layer of engineered granular underneath the floor slabs recommended above.

GPL materials are uniformly graded clean gravels that cannot be compacted. Therefore, they should be vibrated in order to “interlock” gravel particles to provide adequate structural support to the slab-on-grade. Since field compaction tests cannot be performed on GPL materials, visual inspections as part of the construction quality control program shall be conducted during the placement of the radon mitigation GPL.

It is a common local practice to place a layer of 50 mm of lean concrete underneath the footings,…