27 Atch J7a Question No. 48 Geotechnical Investigation Report for B906.pdf

DESIGN ANALYSIS

FY18 ZNRE061207 Repair Failed C130 Hangar Doors System, B906, Yokota Air Base, Japan

Appendix E. Geotechnical Report

Geotechnical Investigation Report

ZNRE06-1207, Repair Failed C130 Hangar Door Systems, B906

Yokota Air Base, Tokyo, Japan

ESC Project 6084

FINAL

03 September 2018

Prepared For:

Jacobs 949 E. 36th Avenue, Suite 500

Anchorage, AK 99508, USA

Prepared By:

Geotechnical Investigation Report i

Repair Hangar Doors, B906, YAB

EXECUTIVE SUMMARY

Environmental Science Corporation (ESC) was tasked by Jacobs to conduct a geotechnical investigation for the preparation of design documents for the repairs of the hangar door for

Building 906 located at Yokota Air Base (YAB), Tokyo, Japan.

The purpose of this geotechnical investigation is to provide geotechnical recommendations in support of the foundation design of the new hangar door and surrounding hangar pavements.

The geotechnical investigation included 2 soil borings conducted to an average depth of 9 m bgs to confirm subsurface site conditions and depth of the bearing layer for the foundations of the proposed structures, with SPTs performed per each meter drilled. All soil borings terminated at depths where very dense gravel soils were encountered. These layers presented SPT N-values of

50+, continuously for the last 5 meters of soil boring. In total, approximately 18 m of soil boring was conducted along with disturbed and undisturbed soil sampling of representative soil layers.

Soils samples were analyzed at a local soils laboratory for basic engineering characteristics. In addition, hand auger soil sampling for CBR and Proctor testing at 2 locations and 1 plate bearing test were conducted in order to provide pavement and earthwork recommendations.

Investigative drilling and soils analysis were performed in accordance with relevant Japan

Industrial Standards (JIS) and Japan Geotechnical Standards (JGS) by a certified soils laboratory in the Kanto area.

Geologic Site Hazards and Site Class

Screening for geological site hazards, including susceptibility to liquefaction and slope failure was conducted at the existing site.

Subsurface and terrain conditions indicate that the potential for liquefaction and slope failure are low.

Field investigation and laboratory test results indicate that the site soils fit the Site Class “D” designation for seismic considerations. Dense to very dense gravel soils encountered within the top 30 m were factors in selecting a Site Class “D” designation for this site.

Details on geological site hazards and site class determination are described in Sections 5.2 and

5.3 of this report.

Site Subsurface Conditions

Distribution of soils is very consistent throughout the site. Site conditions consist mainly of concrete paved surfaces with granular base courses overlying native soft elastic silt and loose silty sand soils followed by layers of dense to very dense gravels. Elastic silt and silty sand soils are composed of volcanic ash mixed with clays and sands and are commonly called loam soils

(Kanto loam), which are widely distributed across the Kanto plain region. The existing concrete pavement structure presents thicknesses of 300 and 400 mm for the PCC slab and the granular base course, respectively.

Geotechnical Investigation Report ii

Signs of environmental contamination of site soils were not noted during geotechnical investigations.

Groundwater was not observed at any of the conducted soil borings.

Foundation Recommendations

Based on the geotechnical investigation results, layers composed of the competent dense to very dense gravel soils are the most suitable bearing layers for the foundations of the new hangar door, which are, located at a depth of approximately 3 m bgs.

The recommended bearing layer has SPT N-values greater than 25. However, in order to implement a shallow foundation system and to reach the recommended bearing layers, soil improvement of in-situ soils by means of soil-cement slurry (SCS) is recommended. Soils to be improved are the layers composed of native soft elastic silt and loose silty sand soils.

Allowable bearing pressures for shallow foundations with soil improvements are recommended to be 200 kN/m

An additional increment of 1/3 of this allowable bearing pressure can be considered for resisting short-term loads such as earthquake and short-time wind loads.

For cost estimating purposes, an average SCS depth of approximately 0.50 meters may be assumed, considering a depth of penetration for footings of 2.5 m bgs..

Hangar Floor Slab and Access Apron Recommendations

Based on the project’s Statement of Work (SOW), the hangar’s airfield operational requirements correspond to an airfield traffic area of C with a medium loading type. Recommendations for the hangar floor slab and access apron consider plain (non-reinforced) concrete for rigid concrete pavements. Flexural strength for PCC is recommended to be 4.5 N/mm

(650 psi).

Recommendations for the hangar floor slab and access apron are based on UFC 3-260-02, “Pavement Design for Airfields”, dated 30 June 2001 and were generated using PCASE

(Pavement-Transportation Computer Assisted Structural Engineering) software developed by

USACE.

HANGAR FLOOR SLAB AND ACCESS APRON RECOMMENDATIONS

Area Type of

Pavement

Airfield

Loading

Type

Recommended Pavement Structure

Hangar Floor Slab /

Hangar Access

Apron

Rigid PCC Medium

PCC Surface = 380 mm

Base Course = 150 mm

Total Pavement Thickness = 530 mm

Geotechnical Investigation Report iii

CONTENTS

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

ACRONYMS AND ABBREVIATIONS ............................................................................................. v

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

5.1.3 Subsurface Variations

5.2 Geological Site Hazards

5.2.1 Soil Liquefaction

5.2.2 Potential Slope Failures

5.3 Site Class Designation

5.3.1 Seismic Design Parameters

6.0 FIELD AND LABORATORY TESTING EFFORTS

6.1 Soil Borings and Standard Penetration Testing

6.2 Geotechnical Field Testing

6.3 Soils Laboratory Testing

7.0 CONCLUSIONS & RECOMMENDATIONS

7.1 Foundation Recommendations for Hangar Door

7.2 Hangar Floor Slab and Access Apron Recommendations

7.3 Soil Materials for Pavements

7.4 Site Drainage

8.0 CONSTRUCTION CONSIDERATIONS

8.1 Earthwork and Grading

8.2 Excavation and Trenching

8.3 Soil Improvements for Buildings and Pavements

9.0 DISCLAIMER

10.0 REFERENCES

Geotechnical Investigation Report iv

TABLES

TABLE 1: SOIL BORINGS SUMMARY

TABLE 2: AIRFIELD OPERATIONAL REQUIREMENTS

TABLE 3: PROJECT’S DESIGN GROSS WEIGHTS AND PASSES LEVELS FOR

AIRFIELD PAVEMENTS

TABLE 4: HANGAR FLOOR SLAB AND ACCESS APRON RECOMMENDATIONS

TABLE 5: COMPACTION REQUIREMENTS

TABLE 6: LIFT THICKNESS REQUIREMENTS FOR BACKFILL AND FILL

COMPACTION

FIGURES

FIGURE 1: PROJECT SITE LOCATION MAP

FIGURE 2: GEOLOGICAL MAP IN THE PROJECT VICINITY

FIGURE 3: SOIL BORINGS, SOIL SAMPLING AND PLATE BEARING LOCATIONS

FIGURE 4: JIS DESIGNATED ENGINEERED BASE & SUBBASE MATERIALS FOR

PAVEMENTS

APPENDICES

A SOIL BORING LOGS

B SOIL PROFILES

C GEOTECHNICAL LABORATORY REPORTS

D FIELD WORK PHOTOGRAPHS

E PCASE OUTPUT FOR HANGAR FLOOR SLAB AND ACCESS APRON PAVEMENT

RECOMMENDATIONS

F CATALOG FOR SOIL IMPROVEMENT METHODS, CEMENT and LIME MATERIALS

Geotechnical Investigation Report v

ACRONYMS AND ABBREVIATIONS

ASL Above sea level

ASTM American Society for Testing and Materials

AC Asphalt concrete

B Minimum width of foundation bgs Below ground surface

Bldg Building

CBR California Bearing Ratio cm Centimeter

EL Elevation of top of borehole in meters

ESC Environmental Science Corporation

H: V Horizontal: Vertical

IBC International Building Code

JGS Japan Geotechnical Society

JIS Japan Industrial Standards

JV Joint Venture kg/m

Kilograms per cubic meter km Kilometer km Square kilometer kN Kilo Newton kN/m Kilo Newton per square meter kPa Kilopascals m Meter m Square meter mm Millimeter

MPa Mega Pascal

MPa/m

Mega Pascal per cubic meter

MSL Mean sea level

Mw Earthquake moment magnitude

N Blow count of the Standard Penetration Test

OSHA Occupational Safety & Health Administration

PCC Portland cement concrete pci Pounds per cubic inch

SOW Scope of Work

SPT Standard Penetration Test

UFC Unified Facilities Criteria

UG Underground

US United States

USACE US Army Corps of Engineers

YAB Yokota Air Base

Geotechnical Investigation Report 1

1.0 INTRODUCTION

Environmental Science Corporation (ESC) was tasked by Jacobs to conduct a geotechnical investigation for the preparation of design documents for the repairs of the hangar door for Building

906 located at Yokota Air Base (YAB), Tokyo, Japan.

The purpose of this geotechnical investigation is to provide geotechnical recommendations in support of the foundation design of the new hangar door and surrounding hangar pavements.

The following report addresses the results of investigative soil borings and geotechnical laboratory analysis performed for this project.

The following describes the major work tasks associated with the contracted geotechnical investigation at the site:

Performed exploratory borings and soils investigation within the project site from June 11 to

22, 2018.

Completed 2 soil borings to an average depth of 9 meters (m) below ground surface (bgs) which confirmed the competent bearing layer for foundations of the hangar door. Standard penetration tests (SPT) were conducted per each meter drilled.

Soil samples were taken at characteristic soil layers at each boring location. In total, 5 disturbed soil samples and 2 undisturbed soil samples were taken and analyzed for physical and engineering soil properties. All samples were taken under the supervision of the project geotechnical engineer. Soil samples were tested for the following geotechnical parameters:

Density of Soil Solid particles (Japan Industrial Standard [JIS] A 1202)

Soil Moisture Content (JIS A 1203)

Soil Particle Size Distribution (JIS A 1204, JIS A 1223)

Atterberg Limits (JIS A 1205)

Unconfined Compression Test (JIS A 1216, Japan Geotechnical Society [JGS]

JGS 0511)

Consolidation Test (JGS 0411) (natural water content and saturated conditions)

Soil samples within the project site were collected and the following geotechnical tests were conducted:

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

Geotechnical Investigation Report 2

Modified Proctor tests (JIS A 1210, JGS 0711)

In addition, the following geotechnical field tests were conducted:

Plate Bearing Test (750 mm diameter plate) (JIS A 1215)

Conducted laboratory tests (unconfined compression, CBR, Modified Proctor, Hexavalent

Chromium leachate) for soil-cement and soil-lime mixtures to provide recommendations for soil improvements.

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

Provided recommendations for allowable soil support capacities based on the existing soil characteristics and conditions, in support of the foundation design for the new proposed hangar door.

Provided pavement design recommendations for the hangar floor slab and access apron.

Provided construction considerations pertinent to earthwork, site grading, site drainage and soil improvements.

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

Geotechnical Investigation Report 3

2.0 SITE OVERVIEW

YAB is located between Fussa and Musashi-Murayama cities, which are located on the western central portion of Tokyo metropolis near the boundary between Tokyo and Saitama prefecture. The site covers a total area of approximately 3,500 square meters (m ) of land and it is located at the southwest side adjacent to the YAB airfield area.

Figure 1: Project Site Location Map

Geotechnical Investigation Report 4

3.0 SITE GEOGRAPHICAL AND GEOLOGICAL FEATURES

The project site is located in the southwest portion of YAB in a terrace area at an approximate elevation of 127.4 m above mean sea level (MSL). The location of the project site is shown in

Figure 1.

YAB is located approximately 31 kilometers (km) northwest from central Tokyo and within the

Kanto plain area, which is the most extensive lowland in Japan, located in central Honshu, facing the Pacific Ocean. The Kanto plain covers an approximate area of 16,200 square kilometers (km contains Japan’s capital city, Tokyo, and constitutes the most productive and populous area of the country. The Kanto plain is located to the east of the Japanese mountain arc, where it bends from a north-south trend to an east-west direction and is walled by mountains (north and west) and hills

(south). YAB is in the west edge of the Kanto plain area on a large diluvium terrace locally called the Musashino plateau. The Musashino plateau is approximately 50 km (from east to west) by 20 km (from north to south) and is dissected by the Tama River in the south and by the Ara and Iruma

Rivers in the north. This plateau originated from the erosion processes of the Tama River in the early Quaternary Pleistocene period and formed an apex at the Oume City area where the Tama

River flows out from the mountainous region of Okutama.

Strata composed of very dense gravel soils from the Oume or Kasumi formations are considered the bedrock of the project area. Surface geology of the project site is composed mainly of layers of elastic silt soils locally called “Kanto Loam”, which are aeolian volcanic ash layers composed of a mixture of silt, sand and clays. The Kanto loam is followed by the Tachikawa formation, which is composed of very dense gravels.

Kanto loam deposits and medium to very dense gravel layers from the Tachikawa formation were confirmed in all the conducted soil borings. However, soil borings did not reach a sufficient depth to confirm the bedrock layer of the site.

Japan is located in the so-called “Ring of Fire”, which is responsible for the considerable earthquake and volcanic activity in the region. Beneath the Kanto area lie three major tectonic plates: the North American Plate, the Philippine Sea Plate and the Eurasian Plate. Offshore, to the east, the Pacific Plate descends beneath these tectonic plates and Japan. The relative deformation between these plates is the major source of seismic activity in this area. In addition, the Japan trench subduction zone is located along the eastern coast of Japan. The epicenters for most of the significant earthquakes occurring in Japan are located along this zone. Strong earthquakes with magnitudes between 7 to 8 can be expected in Kanto area. For instance, the 1923 Great Kanto earthquake registered a moment magnitude (Mw) of 7.9.

Figure 2 shows a geological map and a typical section indicating subsurface formations in the vicinity of the project site.

Geotechnical Investigation Report 5

Figure 2: Geological Map in the Project Vicinity

Low Land

Narimasu formation

Tachikawa formation

Ravine

Hilly

Sueyoshi Lower formation

Project Site

Hongou formation

Aoyagi formation

Tokyo Bay

Tama River

Ara River

Kanto Loam (Volcanic deposit)

Sandy Gravel

Sand (N-value more then 30)

Alluvium

Legend

Tachikawa Gravel

Another terrace gravel layer

Haijima gravel, Aoyagi Gravel

Shirakogawa Gravel

Oume Gravel

Project Site

Tachikawa Plane Haijima Plane

Yokota Air Base

Tama River

JR

Oume

Rail Line

JR

Hakko

Rail Line

Geotechnical Investigation Report 6

4.0 PROJECT CONSIDERATIONS

This project is to design a new “MEGADOOR” vertical lifting fabric door system from ASSA

ABLOY Entrance Systems to replace existing hangar doors system with new system at Hangar

Building 906 in YAB.

New foundations will be required to support the new door system. In addition, it is expected that the existing hangar floor slab and access apron may be affected during the construction of the new door foundations. It is assumed that the finished floor elevations (FFE) of the hangar and access apron will not change. Based on this assumption, cut and fill earthwork to grade the site is not expected.

Recommendations for the hangar floor slab and access apron consider rigid pavements for airfields composed of non-reinforced Portland cement concrete (PCC) surface with granular subbase and base layers. It is assumed that the pavement structures for the hangar floor slab will be the same to the parking apron.

Soil borings at 2 locations, CBR sampling at 2 locations and 1 field plate bearing test were conducted within the project site.

Figures 3 shows approximate soil borings, CBR sampling and field plate bearing locations in relation to current site conditions.

Geotechnical Investigation Report 7

Figure 3: Soil Borings, Soil Sampling and Plate Bearing Locations

Geotechnical Investigation Report 8

5.0 SITE CONDITIONS

5.1 SUBSURFACE CONDITIONS

A general description of the subsurface conditions and various soil materials encountered during the field exploration are presented in this section.

5.1.1 Subsurface Profile of the Site

Distribution of soils is very consistent throughout the site. Site conditions consist mainly of concrete paved surfaces with granular base courses overlying native soft elastic silt and loose silty sand soils followed by layers of dense to very dense gravels. Elastic silt and silty sand soils are composed of volcanic ash mixed with clays and sands and are commonly called loam soils (Kanto loam), which are widely distributed across the Kanto plain region.

The existing concrete pavement structure presents thicknesses of 300 and 400 mm for the PCC slab and the granular base course, respectively.

Underneath the pavement structure, site soils generally consist of native soft elastic silt and loose silty sand soils. These soils are in an over-consolidated state and present high water contents

(maximum water content was observed to be 133%) and high liquid limits (maximum liquid limits was observed to be 178%). Based on CBR testing results, these soils are non-expansive. Stratum containing these soils has a layer thickness of approximately 2 m with SPT N-values ranging from 2 to 5.

Elastic silt soils in the Kanto plain area (Kanto loam) present similar characteristics to sensitive fine-grained soils. Kanto loam soils are capable of supporting low to medium loads if they are not disturbed. In contrast, once loam soils are disturbed, the strength of the soils is compromised and the soil stiffness decreases. This characteristic was verified by results of unconfined compression tests in remolded samples from previous projects at YAB and current CBR test results, which show lower shear strength and modulus values after soil sample preparation disturbance.

Elastic silt and silty sand soils overlay thick layers of dense to very dense gravels. Gravel layers are located at a depth of approximately 3 m below ground surface (bgs). Gravel layers are well graded, presenting matrices of silts and sands. The size of gravel particles vary from 25 mm to 75 mm.

Typically, gravel soils have SPT N values ranging from 30 to 50. This layer is considered a candidate bearing layer to support the foundations of the proposed structures.

Also, during the extraction of soil samples, no visual or olfactory indication of soil contamination was observed by investigative personnel.

Distribution of the site subsurface soils can be referenced in soil profiles included in Appendix B of this report.

Geotechnical Investigation Report 9

5.1.2 Groundwater

Groundwater was not observed at any of the conducted soil borings. Based on local geology and field observations from previous projects at YAB, groundwater may be located at depths greater than 10 m bgs. At these depths, the influence of groundwater is considered negligible for this project. However, although the probability to encounter groundwater perched at shallow depths is low, fluctuations in groundwater level could occur due to change in seasons, rainfall and tidal variations. Therefore, care shall be taken during construction to control groundwater accumulation in trenches, excavations and pits, if water accumulation occurs.

5.1.3 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 boring locations.

5.2 GEOLOGICAL SITE HAZARDS

Screening for geological site hazards, including susceptibility to liquefaction and slope failure, was conducted at the site.

5.2.1 Soil Liquefaction

Generally, soils that are most susceptible to liquefaction are clean, loose, saturated, uniformly graded sands and/or coarse silts that lie below the groundwater table within a depth of 0 to 20 m bgs.

Based on the soil exploration conducted at the site, site soils consist mainly of unsaturated, soft elastic silts, loose silty sands and dense to very dense well graded gravels. Due to the relative absence of saturated clean and loose sands and/or coarse silts in observed subsurface soils, the potential for liquefaction at the site is low. As a result, laboratory testing and detailed modeling analysis specific to liquefaction is not required for this site.

5.2.2 Potential Slope Failures

The project site is located in a relatively flat terrace area at an approximate average elevation of

127.4 m above MSL adjacent to the existing airfield area. Site observations and a topographic survey conducted by ESC in June 2018 indicate that there are not critical slopes at the site.

Geotechnical Investigation Report 10

5.3 SITE CLASS DESIGNATION

Based on our field investigations and the International Building Code (IBC) 2015, SPT results indicate that the site soils fit into Site Class “D” designation for seismic considerations. Thick layers of dense to very dense gravel soils with SPT N-values ranging from 30 to 50, encountered within the top 30 m, were factors in selecting a Site Class “D” designation for this site.

5.3.1 Seismic Design Parameters

Seismic design coefficients corresponding to Site Class “D” were determined based on UFC 3-301 -

01, Structural Engineering, dated 1 June 2013, Change 3, 12 September 2016 and ASCE 7-10, Minimum Design Loads for Buildings and Other Structures.

Mapped spectral response acceleration: Ss = 2.10g, S1 = 0.99g

Site Class parameters: Fa = 1.0, Fv = 1.5

Maximum Considered Earthquake (MCE) spectral response acceleration:

SMS = 2.10g, SM1 = 1.485g

Design spectral response acceleration: SDS = 1.40g, SD1 = 0.99g

Geotechnical Investigation Report 11

6.0 FIELD AND LABORATORY TESTING EFFORTS

6.1 SOIL BORINGS AND STANDARD PENETRATION TESTING

Project field activities began with determining the locations for each boring by a registered surveyor. Boring locations were placed adjacent to the existing hangar door. Benchmarks were established as part of a topographic survey of the site conducted by ESC in June 2018. The vertical and horizontal datum utilized for this survey is the Japan Geodetic Datum (JGD) 2011 Zone 9.

Soil borings and SPT were conducted at the site using an Eco1VIII drilling rig equipped with a 66-millimeter diameter tube bit and split spoon sampler. In total, 2 soil borings were conducted at the site advanced to an average depth of 9 m bgs to confirm subsurface site conditions and depth of the bearing layer for the foundations of the proposed structures, with SPTs performed per each meter drilled. 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.

All soil borings terminated at depths where very dense gravel soils were encountered. These layers presented SPT N-values of 50+, continuously for the last 5 meters of soil boring. In total, approximately 18 m of soil boring was conducted along with disturbed and undisturbed soil sampling of representative soil layers. Soils samples were analyzed at a local soils laboratory for basic engineering characteristics.

Refer to Figure 3 and Table 1 that show the boring locations and depths. SPT N-values were evaluated along with soil testing data to provide foundation recommendations for the new hangar door. Foundation recommendations can be found in Section 7 of this report.

Boring logs are included in Appendix A of this report. Boring logs include the coordinates and elevations of the boring locations, which were determined by ESC’s surveyors.

TABLE 1: SOIL BORINGS SUMMARY

Soil

Boring

Top of borehole elevation

(m MSL)

Depth of boring

(m bgs)

Approx. depth of recommended bearing layer (m bgs)

B-1 127.364 9.40 2.80

B-2 127.344 8.40 2.80

Note:

Depths are from existing ground surface elevation. Recommended bearing layer for the hangar door foundations is the dense/very dense gravel layer. See Section 7 for details.

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

Geotechnical Investigation Report 12

6.2 GEOTECHNICAL FIELD TESTING

In order to provide recommendations for rigid pavements, 1 plate bearing test (750 mm diameter plate) were conducted in native subgrade soils to determine the modulus of subgrade reaction of soils. Tested subgrade was properly prepared prior to the test and extreme care was taken in order to not disturb soils in the test area. Plate bearing test location can be referenced in Figure 3 of this report.

6.3 SOILS LABORATORY TESTING

In total, 5 disturbed soil samples and 2 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 project geotechnical engineer. Disturbed samples were extracted using the SPT split spoon sampler, an excavator or hand auger tools. Undisturbed samples were extracted from block samples using tube samplers. Consolidation tests were conducted in saturated samples obtained by submersion of undisturbed samples in water for 4 days.

Samples of typical layers were tested in a certified local soils laboratory in accordance with relevant

JIS and JGS testing procedures, as indicated in Section 1 of this report.

Two bulk samples were collected to a depth of within 1 m bgs to obtain soil samples for CBR and compaction (Proctor) testing to provide pavement and earthwork recommendations. CBR sampling locations can be referenced in Figure 3 of this report.

In addition, laboratory testing for site soils with cement and lime mixings were conducted in order to provide recommendations for soil improvements. Unconfined compression, CBR, Modified

Proctor and Hexavalent Chromium leachate tests were conducted for different soil-cement and soil-lime ratios.

A summary of field test results and soil laboratory test reports can be referenced in Appendix C of this report.

Geotechnical Investigation Report 13

7.0 CONCLUSIONS & RECOMMENDATIONS

7.1 FOUNDATION RECOMMENDATIONS FOR HANGAR DOOR

Based on the geotechnical investigation results, layers composed of the competent dense to very dense gravel soils are the most suitable bearing layers for the foundations of the new hangar door, which are, located at a depth of approximately 3 m bgs.

The recommended bearing layer has SPT N-values greater than 25. However, in order to implement a shallow foundation system and to reach the recommended bearing layers, soil improvement of in-situ soils by means of soil-cement slurry (SCS) is recommended. Soils to be improved are the layers composed of native soft elastic silt and loose silty sand soils.

Allowable bearing pressures for shallow foundations with soil improvements are recommended to be 200 kN/m . If the recommended bearing layer of dense gravels is encountered at shallow depths, shallow foundations can bear directly on this layer. In this case, the recommended allowable bearing pressure is also 200 kN/m . Recommended allowable bearing pressures are based on a

100% coverage ratio under the footings by means of SCS improvements. Based on discussions with Jacobs design team, bottom of footings may be installed to a depth of approximately 2.5 m bgs. In general, for new foundations that will be located adjacent to existing ones, it is recommended to place the bottom of new footings at the same elevations of the existing footings. If new foundations are deeper than the existing ones, SCS will facilitate their installation since it can avoid undermining the existing foundations due to SCS mixes the in-situ soils inside the excavation trench.

An additional increment of 1/3 of this allowable bearing pressure can be considered for resistance of short-term loads such as earthquake and short-time wind loads.

In order to achieve the recommended bearing pressure, soil improvement (SCS) or shallow foundations must extend to depths where competent dense gravel layers with SPT N-values greater than 25 are encountered. SCS shall extend horizontally at least 150 mm from the edge of the continuous footings. A thin layer of 50 mm of lean concrete is recommended between the shallow foundations and SCS or the recommended bearing layer in order to provide a workable surface for steel reinforcement placement. Minimum 28-day compressive strength for lean concrete is recommended to be 18 N/mm

For cost estimating purposes, an average SCS depth of approximately 0.50 meters may be assumed, considering a depth of penetration for footings of 2.5 m bgs.

The minimum 28-days design compressive strength for SCS shall be 600 kN/m

. Laboratory mix design shall be based on the requirements indicated in "Guidelines for Design and Quality Control of Ground Improvement for Building Foundations" or "Recommendations for Design of Ground

Improvement for Building Foundations", published by the Building Center of Japan and the Japan

Architectural Institute, respectively. Based on the above guidelines and laboratory testing performed for previous projects at YAB for elastic silt soils, laboratory mix designs are expected to have minimum 28-days compressive strengths of approximately 3 times the design compressive

Geotechnical Investigation Report 14 strength with cement amounts of about 300 to 350 kg/m and water-cement ratio of approximately

70%. Type of cement shall comply with local environmental regulations in order to not exceed the limits for hexavalent-chromium leaching.

The estimated total and differential settlements of shallow foundations with soil improvement or shallow foundations resting on the recommended bearing layers is expected to be less than 25 mm and 10 mm, respectively.

In addition, the contribution of earth passive pressures and friction acting on footings and the slab-on-grade can be considered for the lateral load resisting system of the proposed structures.

Recommended equivalent fluid density in order to calculate passive pressures is 22 kN/m

Ultimate friction coefficient between concrete and soils underneath the floor slab and footings is recommended to be 0.45. This friction coefficient does not apply where a plastic vapor barrier or radon barrier is placed beneath the concrete slab.

If basement walls or underground structures (vaults and underground tanks) are planned, they may be designed assuming at-rest earth conditions as long as the walls are restrained by the floor slabs.

At-rest earth pressure may be computed using an equivalent fluid having a density of 10.5 kN/m

If movements of the walls on the order of 0.01 to 0.02 times the height of the wall are allowed, active earth pressures can be used. In that case, active earth pressures may be computed as an equivalent fluid having a density of 8.5 kN/m

Graphical representations of the target bearing layer are shown in soil boring logs and soil profiles included in Appendices A and B, respectively.

7.2 HANGAR FLOOR SLAB AND ACCESS APRON RECOMMENDATIONS

Based on the project’s Statement of Work (SOW), the hangar’s airfield operational requirements are indicated in Tables 2 and 3. Recommendations for the hangar floor slab and access apron are shown in Table 4, which consider plain (non-reinforced) PCC surfaces for rigid concrete pavements. Flexural strength for PCC is recommended to be 4.5 N/mm

(650 psi).

TABLE 2: AIRFIELD OPERATIONAL REQUIREMENTS

Type of

Pavement

Airfield

Traffic Area Airfield Loading Type

Hangar Floor /

Hangar Access

Apron

Rigid PCC Type C Medium

Geotechnical Investigation Report 15

TABLE 3: PROJECT’S DESIGN GROSS WEIGHTS AND PASSES LEVELS FOR AIRFIELD PAVEMENTS

Requirements for number of aircraft passes and design aircraft information are based on airfield traffic area and loading type, respectively, and are in accordance with Table 3-1 of UFC 3-260-02, “Pavement Design for Airfields".

TABLE 4: HANGAR FLOOR SLAB AND ACCESS APRON RECOMMENDATIONS

Type of

Pavement

Airfield

Loading

Type

Recommended Pavement Structure 1, 4

Hangar Floor Slab /

Hangar Access

Apron 2, 3

Rigid PCC Medium

PCC Surface = 380 mm

Base Course = 150 mm (M-30 or M-40)

Total Pavement Thickness = 530 mm

Notes:

Recommended rigid pavement structures are based on an improved modulus of subgrade reaction of 27 MN/m , as a result of soil stabilization with lime or cement for the top 300 mm of the subgrade.

Effective modulus of subgrade reaction on top of base course is 40 MN/m

Effective modulus of subgrade reaction on top of base course is recommended to be field verified by means of 750mm diameter plate bearing tests.

Recommended JIS standardized soils are shown in parenthesis.

Recommendations for the hangar floor slab and access apron are based on UFC 3-260-02, “Pavement Design for Airfields”, dated 30 June 2001 and were generated using PCASE (Pavement-

Transportation Computer Assisted Structural Engineering) software developed by USACE.

Rigid pavement recommendations are based on modulus of subgrade reaction values obtained from the plate bearing test conducted at the site.

Similarly, field plate bearing test indicated a low modulus of subgrade reaction of 8.3 MN/m therefore the subgrade should be stabilized. A minimum thickness of 300 mm of soil stabilization for the top of the subgrade with cement or lime may result in an improved modulus of subgrade reaction of approximately 27 MN/m

Based on actual laboratory testing for soil improvements using cement and lime performed for elastic silts, it is expected that approximately 225 kg/m and 200 kg/m of cement and lime may be

Airfield Loading Type Design Aircraft

C Traffic Area

Weight

(Pounds) Passes

Medium

F-15 E 60,750 100,000

C-17 435,000 400,000

B-52 300,000 400

Geotechnical Investigation Report 16 required to improve the subgrade soils to a minimum improved modulus of subgrade reaction of 27

MN/m , respectively. It was also observed, that soil improvements with cement and lime greatly contribute in decreasing the very high water contents of native elastic silt soils, which as result will aid compaction operations. Based on laboratory test results, stabilized subgrade may be compacted to a minimum 90% compaction, as determined by ASTM D1557 or equivalent JIS A1210. In addition, it is highly recommended that improved modulus of subgrade reaction be verified during construction by means of field plate bearing tests.

Granular base courses shall be compacted to 100% compaction in accordance with ASTM D1557 or equivalent JIS A1210 (Modified Proctor). Recommended materials for locally available granular base materials should be similar to mechanically stabilized materials such as JIS standardized M-30 or M-40 (or their recycled equivalent, RM-30 or RM-40, respectively), as shown in Figure 4, and should be inorganic, non-expansive and free of debris. Due to their very high natural water contents and based on laboratory testing results, in-situ subgrade soils composed of elastic silts, may be compacted to a minimum 80% compaction of modified Proctor. Improved elastic silts may be compacted to 90% compaction of modified Proctor.

7.3 SOIL MATERIALS FOR PAVEMENTS

In general, base and subbase soil materials shall have minimum CBR values of 80 and 20, respectively. The recommended materials for base and subbase courses are the JIS standardized M-

30 or M-40 (for base courses) and C-40 (for subbase courses) soils.

The recycled equivalents of these soils (RM-30, RM-40 and RC-40) may be also acceptable. CBR values for these materials are generally greater than 80, are non-plastic and contain less than 15% fines. These materials are commonly used in local pavement construction and their properties are regulated in accordance with JIS A5001.

Properties of these materials were verified against UFC 3-260-02 requirements for subbase and base course materials for airfield pavements which may apply for the hangar pavements. The recommended subbase course material (C-40) meets the UFC requirements. However, there are discrepancies between the recommended base course materials (M-30 or M-40) and UFC requirements. To meet UFC requirements, M-30 and M-40 particles larger than 4.75 mm (No.4 sieve) must be slightly adjusted to meet UFC 3-260-02 requirements of between 20 to 50 percent passing 4.75 mm or No. 4 sieve.

Base and subbase courses shall be placed in 150 mm lifts when compacted. Each lift shall be compacted to 100% compaction, as determined by ASTM D1557 or equivalent JIS A1210.

Compaction verification should be conducted by means of field density tests (sand cone tests) in accordance with ASTM D1556 or equivalent JIS A1214.

Figure 4 shows the grading requirements for JIS designated engineered base and subbase materials.

Table 4 includes recommended JIS standardized soil materials for pavement structures.

Geotechnical Investigation Report 17

Figure 4: JIS Designated Engineered Base & Subbase Materials for Pavements

Notes:

1. M-30 and M-40 soil materials (or their recycled equivalent RM-30 and RM-40) are recommended for base courses.

2. C-40 soil material (or its recycled equivalent RC-40) is recommended for subbase courses.

Geotechnical Investigation Report 18

7.4 SITE DRAINAGE

Adequate positive drainage should be provided away from building pads, footing areas and pavements to prevent ponding and to reduce potential percolation of water into the foundation soils.

Planters and landscaped areas adjacent to the building perimeter should be designed and irrigated to minimize water infiltration into the subgrade soils.

Adequate drainage should also be provided for any cut/fill slopes, landscaped areas and paved areas, as applicable. Based on Table 3.1 of UFC 3-201-01, “Civil Engineering”, dated 01 June

2013, minimum drainage gradient is 1.5% for AC flexible pavements. In landscaped areas, a minimum drainage gradient of 2% is recommended. Surface drainage should be directed to suitable non-erosive drainage structures. Slopes should be covered or planted as soon as possible after construction.

In addition, since free water tends to attract birds that then pose a hazard to aircraft, the site must drain without accumulating free water anywhere in the airfield area. Drainage should be accomplished by proper sizing of drainage structures and construction of the drainage system with adequate gradient to facilitate movement of water from the site.

Final pavement grade should be designed such that ponding on or adjacent to the pavements is avoided, in order to reduce the potential for premature pavement distress and damage. Although a high water table at the site is not expected, capillary action may affect the pavement structure. In order to alleviate capillary action, subbase materials containing less than 10% fines (materials passing No. 200 or 0.075 mm sieve) are recommended. Based on particle size information indicated in Figure 4 of this report, the recommended subbase materials C-40 and RC-40 satisfy this requirement.

Geotechnical Investigation Report 19

8.0 CONSTRUCTION CONSIDERATIONS

8.1 EARTHWORK AND GRADING

Based on the project’s scope of work, extensive earthwork and grading operations are not expected at the site. Most of the earthwork operations will be related to subgrade preparation for the hangar door foundations, floor slab and access apron and placement of subbase and base courses for pavements.

Quality control for earthwork during the construction stage should include verification of the compaction requirements indicated in Tables 5 and 6. A testing program should be established at the beginning of the construction work. The recommended frequency of field density testing is based on NAVFAC DM-7.02 (1982) guidelines. At least one test for every 75 to 150 m of fill material is recommended. Based on Table 6, and considering a 150 mm compacted lift thickness, a minimum of one field density test is required for every 500 to 1,000 m , per lift. Field density testing shall be conducted in accordance with ASTM D1556 or equivalent JIS A1214 test method.

Since the strength of elastic silt soils can decrease after being disturbed, excavation operations for subgrade preparation shall be conducted carefully in order to produce the least possible disturbance of silt soils. This may be accomplished using adequate equipment (excavators with flat buckets rather than teeth buckets) and being careful to not excavate beyond depths specified in the design drawings.

On-site elastic silt soils are not recommended to be reused for backfill operations under building or pavement structures since their in-situ water contents are much higher than the optimum water content, and therefore proper compaction will be difficult to achieve. Loss of support strength of elastic silt soils after disturbance could be verified in previous projects based on CBR testing and unconfined compression tests in remolded samples. However, they may be used in landscaped areas or other non-loaded areas. Recommended soil improvements for in-situ soils (soil improvement by means of SCS for building foundations and soil stabilization for pavement subgrade) will minimize excess soil excavation and related disposal costs.

Off-site borrow soils should be tested for engineering properties and approved by the project geotechnical engineer prior to delivery on site. The off-site fill should be non-expansive (with a

CBR expansion potential no greater than 1% when tested in accordance with ASTM D1883 or equivalent JIS A1211) and free of organic matter and other deleterious material. Rocks larger than

200 mm in the largest dimension should not be placed as fill. Typical engineering properties of compacted fill soil can be referred to in Table 3-1 of UFC 3-220-04FA, “Backfill for Subsurface

Structures”, dated 16 January 2004. Values shown in this table may be used for initial evaluation of fill soil.

Prior to compaction, fill materials should be thoroughly mixed and moisture conditioned, when necessary, to within ±3 percent of optimum. It is recommended that all fill follows the compaction requirements indicated in Tables 5 and 6. Laboratory compaction tests (Modified Proctor tests) shall be conducted in accordance with ASTM D1557 or equivalent JIS A1210 test method.

Geotechnical Investigation Report 20

Compaction of backfill adjacent to structural walls can produce excessive lateral pressures.

Improper types and locations of compaction equipment and/or compaction techniques may damage the walls. The use of heavy compaction equipment should not be permitted within a horizontal distance of 1.5 m of structural walls. Backfill behind any structural wall within the 1.5m zone should be compacted using lightweight construction equipment such as handheld compactors to avoid overstressing the walls.

TABLE 5: COMPACTION REQUIREMENTS

Structure or location

Compaction Degree

(% of JIS A1210 or ASTM D1557)

Fine-grained

Material

Granular

Material

A. Fill, Embankment and Backfill

A.1. Under proposed structures, building slabs, steps and paved areas 90 95

A.2. Under sidewalks and grassed areas 85 90

B. Base and Subbase courses for pavements (Airfield) - 100

C. In-situ non-improved subgrade (elastic silt soils) 80 -

D. Improved subgrades with cement or lime 90 -

E. Engineered Granular Fill - 95

TABLE 6: LIFT THICKNESS REQUIREMENTS FOR BACKFILL AND FILL COMPACTION

Type of soil

Equipment used

Confined spaces

(Behind structural walls within 1.5 m zone) Open spaces

Small equipment

(rammers, tampers or similar)

Heavy equipment

(pneumatic tire rollers or similar)

Heavy equipment

(heavy vibratory equipment or similar)

Cohesive Max. 100 mm loose lift with rammer compactors

250 mm loose lift -

150 mm when compacted Minimum effect

Granular 100 mm to 150 mm loose lift with a vibratory plate or vibratory walk-behind roller

200 mm loose lift -

150 mm when compacted

300 mm loose lift - 150 mm when compacted

Geotechnical Investigation Report 21

The loose-lift thickness of controlled compacted fill will depend on the type of backfill material and the compaction equipment to be used. Generally, a loose-lift thickness that will result in a 150 mm lift when compacted is acceptable for most heavy compaction equipment.

Table 6 shows loose-lift thickness requirements for different type of soils and compaction equipment.

8.2 EXCAVATION AND TRENCHING

Based on the materials encountered in exploratory borings, temporary excavations may be sloped to an open excavation depth of 5 m maximum, at 1.5:1.0 (H:V) for granular soils and 1.0:1.0 (H:V) for cohesive soil matrices encountered at the site, and as appropriate for Type C and B soils, respectively; in accordance to US Occupational Safety & Health Administration (OSHA) regulations and USACE EM-385 safety requirements. Excavation and trenching cut slopes and benching should be re-evaluated by a qualified geotechnical engineer or other competent person when slopes are steeper than the recommended slope or excavations are greater than 6 m in depth during construction.

For steeper temporary construction slopes, or excavations in the proximity of existing utilities and existing roadway or structures, shoring should be provided by the Contractor as necessary to protect the workers and nearby structures during excavation. Where a trench side has a vertical cut, it should be adequately supported by temporary shoring to protect adjacent structures and withstand ground movement. The support necessary to protect the trench from adverse effects due to ground movement will depend on the load imposed by nearby structures and shall be evaluated by a qualified shoring designer, where required.

Adequate provisions should be made to protect slopes from erosion during periods of rainfall.

However, due to the expected depth of groundwater, extensive temporary dewatering systems are not anticipated during the construction stage.

Surcharge loads, including construction materials, should not be placed within 1.5 m of an unsupported slope edge. Stockpiled soils with a height greater than 1.8 m may require greater distance from trench edges.

Extensive cut operations are not expected at the site. However, if required, cut operations and excavations should not cause loss of bearing and/or lateral support of the existing structures or utilities. Excavations are expected to be mostly in elastic silt and gravel soils. Based on the observations from the exploratory subsurface borings and soils testing, conventional heavy-duty earth moving and trenching equipment should be able to excavate the soil materials at the site.

In addition, based on the soil investigations, it is anticipated that most of the natural soils encountered at the site are stable and may provide a firm foundation for utility pipes. However, any soft spots and/or unsuitable material encountered for the pipeline foundation should be removed and replaced with an adequate foundation soil material. Specifications for soil materials and backfill requirements surrounding the pipe (generally, 150 mm pipe bedding and 300 mm of

Geotechnical Investigation Report 22 pipe covering) should be specified by either the pipe manufacturer or design engineer. To provide uniform bedding and assure proper pipe performance, free-draining granular materials with little or no fines are recommended for the soils surrounding the pipe. For pipes 150 mm diameter and greater, it is recommended to use soils with a maximum particle size of 40 mm. For pipe diameters less than 150 mm, a maximum particle size of 20 mm is recommended. If long-term accumulation of water in the pipe trench occurs during construction, the trench should be pumped dry and properly prepared prior to installing utility pipes.

8.3 SOIL IMPROVEMENTS FOR BUILDINGS AND PAVEMENTS

As indicated in Section 7.0, soil improvements by means soil-cement slurry (SCS) is recommended to support conventional shallow foundations for the new proposed buildings.

Due to in-situ elastic silt soils loss their strength after being disturbed and their very high water contents which make compaction requirements difficult to achieve, excess soils from excavations cannot be reused as backfill underneath structures (building and pavements), and therefore; most of the excess soils will need to be disposed/wasted. In addition, overexcavation of in-situ elastic silts and consequent replacement with engineered granular fill may required some sort of temporary shoring systems (if sloped excavations cannot be done), due to the recommended bearing layer composed of dense to very dense gravel soils is located at approximate 3 m bgs in average.

Soil improvement methods by means of SCS mix cement slurry with in-situ soils. Its installation has been considered in order to minimize earthwork and soil disposal costs. In addition, SCS method is appropriate when the competent the bearing layer of gravel soils is located at intermediate depths where are too shallow for piles or deep soil mixing and too deep for shallow foundations.

This technique uses an excavator-mounted mixing tool and a pneumatically-delivered wet slurry binder to create a large stabilized mass. Cement slurry is introduced into in-situ soils from nozzles attached to the bucket of the excavator.