Geotechnical Investigation Methods

Following topics to be discussed for Geotechnical Engineering Investigation.

6.1 Field Reports
6.2 Preliminary Report
6.3 Final Report
7.1 General
7.2 Underground Utilities
7.3 Field Work
7.4 Laboratory Testing
APPENDIX – A Geotechnical Services

1. Scope

This procedure (article) is for geotechnical engineering investigations for project site.

2. Geotechnical Engineering References

Reference is made in this specification to the following documents. 

American Society for Testing and Materials (ASTM)

D 420 Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes
D 698 Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort (600 kN-m/m3 (12,400 ft-lbf/ft3))

D 1557 Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort  (2700 kN-m/m3 (56,000 ft-lbf/ft3))

D 1883 Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils
D 2166 Test Method for Unconfined Compressive Strength of Cohesive Soil
D 2435 Test Method for One-Dimensional Consolidation Properties of Soils
D 2487 Test Method for Classification of Soils for Engineering Purposes
D 2850 Test Method for Unconsolidated, Undrained Compressive Strength of Cohesive Soils in Triaxial Compression
D 4253 Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table
D 4254 Test Method for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density
D 5434 Guide for Field Logging of Subsurface Explorations of Soil and Rock

Occupational Safety and Health Administration (OSHA) of U.S.A.

29 CFR 1926 Code of Federal Regulations
1910 Standards and Compliance Guidelines

3. Geotechnical Services

3.1 Investigations shall consist of subsurface exploration, field and laboratory testing of soil samples, as needed, analyses, evaluation of test results, preparation of report(s), and engineering recommendations for design and construction of foundations. 

3.2 Required geotechnical services will be specified by  in Appendix A.

3.3 SI units shall be used in accordance with International Standards.

4. Project Data

Company generally provide contractor with the following:
a. Site location plan
b. Plans showing the proposed locations of soil borings (coordinates and elevations)
c. Loading conditions for the major equipment, structures and buildings required for the project

5. Geotechnical Investigation Project Requirements 

5.1 Contractor shall inspect the site, to become familiar with the existing conditions and to evaluate the suitability of both proposed design/construction of facilities, and plan of work.

5.2 Contractor shall submit the following to Company for approval.

a. Either a statement supporting the adequacy of proposed geotechnical investigation,  including project data from 3.3 for field/laboratory testing, or suggested modifications to the geotechnical investigation
b. A detailed proposed program of field exploration, and field and laboratory testing, when one is not provided. Program shall contain:

(i) Plan showing locations and depths of proposed borings and any other proposed exploration

(ii) Proposed field sampling and testing program, including types and frequency of samples and  tests
(iii) Proposed laboratory testing program, including types and numbers of tests
(iv) Descriptions of any proposed methods/tests not referenced in this specification

c. A schedule of beginning and completion dates of field and laboratory work, and dates for  submittal of preliminary and final reports
d. Descriptions of any structures, equipment, utilities, vegetation or other facilities that will require
removal, or that will be damaged due to equipment access to boring locations

5.3 Contractor shall obtain all work, excavation and other permits or authorizations required or regulatory agency, for example authorizations for borings, soundings, test pits, wells, piezometers, and transportation of samples.

5.4 Contractor shall provide a full time geotechnical contractor in the field during exploration activities. Geotechnical contractor shall supervise and observe all subsurface exploration operations, classify samples and prepare logs of borings, soundings, and pits.

5.5 Contractor shall perform the geotechnical investigation, exploration, testing, analyses and reporting in accordance with this specification and ASTM D 420.

6. Geotechnical Investigation Reports

6.1 Field Reports

The following field reports shall be maintained, and submitted if required by Company:

a. Field logs of borings, soundings, test pits, wells and other field exploration/testing activities, in accordance with ASTM D 5434.
b. Progress reports, summary of work completed, and description of unusual or unanticipated conditions encountered
c. Assessment of adequacy of work scope, and any recommended modifications
d. Statement of progress relative to planned schedule

6.2 Preliminary Report

Preliminary report shall be submitted for review and comments which shall consist of findings,  conclusions and recommendations for 3.1, and the following:
a. Logs and location plan of borings, soundings, test pits, wells, and other field exploration/testing activities
b. Subsurface cross-sections
c. Discussion of groundwater, and impact on proposed construction

d. Results and interpretations of field testing
e. Allowable soil bearing capacity and recommended foundation type(s) and design parameters
f. Discussion of foundation settlements
g. Discussion of potential problems that may affect project planning, schedule, cost, design or construction

6.3 Final Report

After incorporation of requirements, contractor shall submit a final report.

7. Execution of Work Activities

7.1 General

7.1.1 Contractor shall conform to HCIS SSD 29, and OSHA 29 CFR 1926 and 1910.
7.1.2 Contractor shall conform to safety programs and policies.
7.1.3 Contractor shall conform to ASTM standards referenced in section 2. Use of other applicable ASTM standards shall require prior Comp. approval.
7.1.4 If initial field work or testing indicate a need for modifications in the work scope, shall be informed within 24 hours.

7.2 Underground Utilities

7.2.1 Prior to commencing field work, contractor shall request to provide the latest as-built drawings detailing existing underground utilities. Geotechnical contractor shall check for underground utilities at every bore hole by using underground detection equipment.
7.2.2 Prior to start of borings, test pits up to 1.5 m depth shall be performed, to identify underground utilities.
7.2.3 Contractor shall perform all work a sufficient distance away from underground and above ground utilities to protect personnel and utilities.

7.3 Field Work

7.3.1 Unless specified otherwise in the contract, contractor shall perform and provide any site modifications, improvements, special equipment, or clearing required for access to locations of borings, soundings and pits.
7.3.2 If any indication of soil or groundwater contamination is detected, all work shall be suspended immediately, and Comp. shall be informed. Work shall not be resumed until notification to proceed is received from.
7.3.3 In each test boring, soil sampling shall be performed at intervals of no greater than 75 cm (2.5 ft) in the upper 3 m (10 ft), and thereafter at every 1.5 m (5 ft), and at changes in soil strata.

7.3.4 Tubes of minimum 76 mm (3 in) diameter shall be used for thin-walled tube sampling.

7.3.5 Groundwater levels shall be determined by installing minimum one piezometer in four bore holes.

Samples of water shall be collected for testing.

7.3.6 Comp. shall be notified at least three days prior to completion of field work, or removal of equipment from the site, or both.

7.3.7 Completed boreholes and soundings shall be grouted from the bottom of the hole up, using a grout mixture of portland cement with between 4 to 15 percent by weight addition of bentonite. Potable water, or water from a approved source shall be used.

7.3.8 Contractor shall restore site to original condition, or as specified in the contract.

7.4 Laboratory Testing

7.4.1 Contractor shall perform the laboratory testing required for the services specified in the contract.
7.4.2 Classification of soils shall be in accordance with ASTM D 2487.
7.4.3 Other soil properties shall be determined in accordance with ASTM D 698, D 1557, D 1883, D 2166,
D 2435, D 2850, D 4253, and D 4254.
7.4.4 Comp. shall be notified within 24 hours of any modifications to the testing program.

Geotechnical Services

Contractor shall submit findings, conclusions and recommendations on items checked as required in the following list.

1. Introduction

 1.1 Description of proposed construction.
 1.2 Purpose and scope of investigation.
 1.3 Abstract of findings and recommendations.

2. Site Conditions

 2.1 Site geology, general description.
 2.2 Potential geological hazards.
 2.3 Site surface description.
 2.4 Site topography, general description.
 2.5 Description of above ground obstructions.

3. Subsurface Conditions

 3.1 Stratigraphy.
 3.2 General description of subsurface material properties.
 3.3 Groundwater elevations and expected variations.
 3.4 Description of underground obstructions encountered or otherwise identified.
 3.5 Corrosion potential for underground utilities and storage tanks.
 3.6 Chemical attack potential for concrete and underground utilities.

4. Field Geotechnical Investigation

 4.1 Summary of operations.
 4.2 Description of sampling procedures.
 4.3 Description of field tests.
 4.4 Logs of borings, soundings, test pits, and wells, in accordance with ASTM D 5434 and  containing:

a. Minimum number of borings, soundings, test pits and wells
b. Complete descriptions and thicknesses of all strata, including near-surface materials, for example paving, base course, topsoil, and fill
c. Locations referenced to plant coordinate system
d. Ground surface elevations referenced to plant datum, if available; if not, then referenced to Royal Commission datum
e. Standard penetration test (SPT) values in blows per 150 mm (6 in) increments
f. Results of all field tests

 4.5 Location plan, containing as a minimum:
a. Scale plan with locations of borings, soundings, test pits, and wells
b. Plant coordinate system

5. Laboratory Tests of Geotechnical Investigation

 5.1 Description of tests.
 5.2 Test results.

6. Hydrology

 6.1 Erosion potential.
 6.2 Surface run-off coefficients.
 6.3 Percolation.

7. Seismic Analysis

 7.1 Seismicity based on seismic risk map.
 7.2 Soil profile type and site coefficient(s).
 7.3 Site specific seismic risk study.

8. Soil Zoning of Plant Site

 8.1 Plant site shall be zoned based on the allowable soil bearing capacity with respect to a depth established by project and soil contractor.
 8.2 Cross sections of bore holes of each zone showing soil profile type.

9. Foundation Recommendations

 9.1 Type(s) of foundation recommended.
 9.2 Basis for selecting recommended foundation type(s).
 9.3 Recommendations for foundation type(s) selected.
 9.4 Recommendations for deep foundations regardless of foundation type selected.
 9.5 Recommendations for shallow foundations regardless of foundation type selected.
 9.6 Soil strength parameters used in determining design bearing capacities specified in section 8 of this specification.

10. Shallow Foundation Recommendations

 10.1 Spread footings: depth below grade, size and shape restrictions.
 10.2 Mat foundations: depth below grade, modulus of subgrade reaction.
 10.3 Tank foundations: Recommendations and restrictions, excavation and backfill, ringwall  or mat considerations, and extended hydro tests for tanks.

10.4 Vibratory equipment foundations:

 10.4.1 Dynamic shear modulus, Poisson’s ratio, damping ratio based on:

a. Correlations from published literature
b. In-situ testing

 10.4.2 Effect of vibrating equipment dynamic loading on soil.

a. Densification of loose cohesionless soil
b. Liquification of loose saturated cohesionless soil

10.5 Ultimate and allowable net soil bearing capacity.

 10.5.1 On natural soils.
 10.5.2 On structural fill.
 10.5.3 As a function of the shape and size of foundation, depth of embedment, and soil strength.
 10.5.4 Any increase in net allowable bearing capacity for hydrotest loads, and short term loads, for example wind and earthquake.

 10.6 Foundation settlement considerations.

10.6.1 As a function of loading, shape and size of foundations, and compressibility of sub-soils.
10.6.2 Immediate settlement during construction.
10.6.3 Long term settlement.
10.6.4 Time rate of settlement.
10.6.5 Adjacent foundation settlement.
10.6.6 Differential settlement for tanks.

a. Along the perimeter
b. Center of tank to perimeter
c. Slope of tank bottom after anticipated settlement
d. Limitations or recommendations for hydrotest procedures to minimize differential settlement
e. Anticipated settlement and rebound during hydrotest and specific measurements during hydrotest
f. Settlement values at one (1) meter intervals for a depth equal to the diameter of tank

 10.7 Resistance to lateral loads.

11. Deep Foundation Recommendations

 11.1 Type of pile or drilled pier, and basis for recommendation.
 11.2 Ultimate and allowable axial compression capacity through end bearing and skin  friction.

11.2.1 Capacity versus length.
11.2.2 Any increase in capacity for hydrotest loads, or for short term loads, for example wind and earthquake.

 11.3 Minimum and maximum tip elevations, when applicable.

 11.4 Ultimate and allowable axial uplift capacity.

11.4.1 Uplift capacity versus length.
11.4.2 Any increase in capacity for hydrotest loads, or for short term loads, for example wind and earthquake.

11.5 Allowable lateral load capacity.

 11.5.1 Applied lateral loading versus deflection of pile head.
 11.5.2 Pile moment versus depth.
 11.5.3 P-Y curves.
 11.5.4 Recommendations for generation of P-Y curves and required parameters (cohesion,  friction angle, and modulus of elasticity of soil).

 11.6 Consideration of down drag forces.
 11.7 Spacing, group action, and use of batter piles.
 11.8 Settlement considerations.
 11.9 Vibratory equipment foundations, spring constants in each direction for recommended  pile type.
 11.10 Driven pile installation considerations.

 11.10.1 Driving criteria, including refusal criteria.
 11.10.2 Wave equation analysis.
 11.10.3 Pre-drilling requirements/restrictions.
 11.10.4 Potential problems and recommended solutions.
 11.10.5 Pile installation near existing facilities.

 11.11 Drilled (non-driven) pile and pier installation considerations.

11.11.1 Installation equipment requirements.
11.11.2 Casing/slurry considerations.
11.11.3 Installation criteria and recommendations.
11.11.4 Potential problems and recommended solutions.

 11.12 Load test requirements, procedures, and acceptance criteria.

12. Geotechnical Investigation of Earth Pressures

 12.1 Active earth pressure, at-rest earth pressure.
 12.2 Ultimate and allowable passive soil resistance for on-site soils, and recommended fill  and backfill material.
 12.3 Groundwater considerations.
 12.4 Drainage requirements.

13. Geotechnical Investigation of Soil Properties

 13.1 Grain size distribution, unit weight, moisture content and relative density from SPT tests.
 13.2 Coefficient of friction or adhesion values between soil and concrete.
 13.3 Compressibility of soil and modulus of elasticity of soil.
 13.4 Cohesion and angle of internal friction.

 13.5 Chemical analysis and other properties of soil and groundwater at depths of proposstructural elements and utilities:

 13.5.1 pH value.
 13.5.2 Electrical conductivity (laboratory determination).
 13.5.3 Chloride ion (Cl + ) concentration.
 13.5.4 Sulfate ion (SO 4 ) concentration.
 13.5.5 Electrical resistivity of soil (field determination).
 13.5.6 Yearly average moisture content of soil.
 13.5.7 Thermal resistivity of soil.

13.6 Permeability.

 13.6.1 Laboratory determination.
 13.6.2 In situ determination.

 13.7 Dynamic soil test for values specified in 10.4 of this Appendix.

14. Slabs, Pavements and Roadways

 14.1 Natural soil and fill, subgrade suitability.

 14.2 Recommended California bearing ratio (CBR) value for pavement design.

 14.2.1 Based on correlations from published literature.
 14.2.2 Based on laboratory testing.
 14.2.3 Based on in-situ testing.

 14.3 Recommended modulus of subgrade reaction for slab design.
 14.4 Treatment for improving subgrade, if required.
 14.5 Base course, sub-base course, and shoulder recommendations.
 14.6 Surfacing recommendations.
 14.7 Base, sub-base, and subgrade drainage recommendations.
 14.8 Complete pavement system design.

15. Excavation

 15.1 Allowable excavation slope inclinations, temporary and permanent.

15.2 Groundwater control.

 15.2.1 Recommended dewatering method.
 15.2.2 Temporary and permanent groundwater control.
 15.2.3 Flow quantities.

15.3 Foundation subgrades.

 15.3.1 Heave control.
 15.3.2 Protection/preserving integrity of subgrade.
 15.4 Effects on existing facilities.
 15.5 Potential excavation problems.

15.6 Rock excavation.

 15.6.1 Rippability of rock.
 15.6.2 Definition of rock for contract documents.
 15.6.3 Rock quantity estimate guidance.

 15.7 Pressure diagrams for shoring design.
 15.8 Applicability of specialized shoring/stabilization procedures.
 15.9 Classification of soil types in accordance with OSHA (types A, B, C).

16. Dikes and Embankments

 16.1 Recommended slope inclination.
 16.2 Slope stability analysis.
 16.3 Settlement.
 16.4 Seepage analysis.
 16.5 Erosion protection of slopes.
 16.6 Foundation and subgrade preparation.
 16.7 Fill material: type, compaction, and moisture content control.

17. Railroads

 17.1 Natural soil and fill subgrade preparation.
17.2 Ballasting, with consideration of availability of local materials.

18. Earthwork

 18.1 Topsoil: thickness for stripping, definition for contract documents.
 18.2 Suitability of on-site material for structural and non-structural fill.
 18.3 Special preparations or other requirements for use of on-site material.
 18.4 Availability of imported fill.

 18.5 Subgrade preparation.
 18.6 Recommended compaction criteria and moisture content control.
 18.7 Potential compaction difficulties and recommended solutions.

19. Other Considerations

19.1 Pre-load considerations, for tanks, large mats, cooling tower structures.

 19.1.1 Pre-load magnitude, side slopes for soil pre-load.
 19.2 Liquefaction potential of soils.
 19.3 Swelling potential of soils, including zone depth of soil moisture content fluctuation.
 19.4 Collapsible or dispersive soils.
 19.5 Effects of proposed construction on existing facilities or adjacent property.
 19.6 Geological or other potential hazards.
 19.7 Sheet piling for temporary and permanent excavation protection, retaining wall construction.

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