CHAPTER III - GEOTECHNICAL ENGINEERING

January 2021CHAPTER III - GEOTECHNICAL ENGINEERING .4SECTION 301 INTRODUCTION . 4SECTION 302 ADMINISTRATIVE REQUIREMENTS . 6302.01 Safety .6302.02 Existing Utility Protection .6302.03 Landowner Notification .6302.04 Work on Railroad Property.10302.05 Traffic Control .10302.06 Work in Environmentally Protected Lands .11SECTION 303 MINIMUM GEOTECHNICAL INVESTIGATION REQUIREMENTS . 12303.01 Subsurface Exploration Program .12303.02 Subsurface Exploration Methods .13303.03 Ground Water Observation Wells .23303.04 Sampling Requirements .24303.05 Soil, Intermediate Geomaterial, and Rock Descriptions .26303.06 Boring Logs .38SECTION 304 LABORATORY TESTING . 39304.01 Soil Laboratory Testing .39304.02 Rock Testing .41SECTION 305 GEOTECHNICAL ANALYSES . 42305.01 Geotechnical Design for Substructures.42305.02 Soils for Embankments and Subgrades .42305.03 Geotechnical Design for Embankments and Cut Slopes (soil) .42305.04 Geotechnical Design for Rock Slopes and Rock Cuts .44305.05 Drainage Pipes and Culverts.52305.06 Stormwater Management Basins .53SECTION 306 GEOTECHNICAL WORK PRODUCTS . 54306.01 Preliminary Soil Survey.54306.02 Geotechnical Data Reports .55306.03 Geotechnical Engineering Reports .56306.04 Geotechnical Design References .58SECTION 307 MONITORING PERFORMANCE DURING CONSTRUCTION . 59SECTION 308 QUALITY ASSURANCE OF CENTRAL MIX SELECT MATERIAL AND DENSE-GRADEDAGGREGATE FOR SUBBASE AND BASE . 61308.01 General .61308.02 CMA Plant .61308.03 Approval of Job Mix.64308.04 Documentation of Tonnage Material .64308.05 Sampling, Testing, and Acceptance of CMA .64SECTION 309 PROJECT SAMPLING, TESTING AND INSPECTION . 70309.01 Density Control .71309.02 Depth Control .76309.03 Sampling, Testing, and Analysis of Resilient Modulus for Subgrade, Subbase, and Base .78309.04 Subgrade Chemical Stabilization .78309.05 Use of Crushed Hydraulic Cement Concrete for Embankment Fill, Subbase or Aggregate Base Material .79309.06 Compaction of #10 Tertiary Screenings (Stone Dust) .81309.07 Application of Calcium Chloride to Aid in Stabilizing Gravel Roads.81III-2

January 2021SECTION 310 PROJECT SAMPLING OF STABILIZED OPEN-GRADED BASE MATERIAL FORACCEPTANCE . 82310.01 General .82310.02 Frequency of Test Samples.82310.03 Reports.82SECTION 311 SUMMARY OF MINIMUM ACCEPTANCE AND INDEPENDENT ASSURANCE SAMPLINGAND TESTING REQUIREMENTS . 83Central Mix Aggregate (CMA) Pugmill Plant Inspection Report . 90Soils & Aggregate Density and Depth Independent Assurance (IA) Evaluation Checklist . 93III-3

June 2019CHAPTER III - GEOTECHNICAL ENGINEERINGSECTION 301 INTRODUCTIONThis Manual of Instructions (MOI) presents minimum requirements for conducting geotechnicalengineering studies for VDOT projects throughout the Commonwealth of Virginia. This document is thework product of the Materials Division and is prepared in conjunction with VDOT’s Structure and BridgeDivision, which relies on geotechnical data and interpretation for the design of structure foundations.Geotechnical engineering explorations and analyses within the Commonwealth of Virginia occur inwidely varying geologic terrain throughout the five physiographic provinces (i.e., Coastal Plain,Piedmont, Blue Ridge, Valley and Ridge and Appalachian Plateau). Work on VDOT projects is primarilycoordinated through nine district offices. This document is intended to establish typical requirementspertaining to state-wide geotechnical exploration and analyses. However, VDOT acknowledges that ininstances where unique field conditions or local practices warrant exceptions to this manual, suchexceptions shall be approved in advance by the District Materials Engineer.VDOT projects include the efforts of Central Office, district offices, on-call consultants, design-builders,PPTA concessionaires, localities, and developers. To develop conformity in those work products, thisMOI establishes minimum standards and design criteria for our projects.Depending on the nature of the project, geotechnical engineering studies for VDOT projects may includethe following:1. The various soil and/or rock types within the limits of the project.2. The effect of ground water on the proposed project.3. Soils in proposed cut areas (i.e., soil classification, moisture content and moisture-densityrelations) for proposed reuse as compacted fill.4. Representative samples of each soil or rock type or stratum for testing and classification in thelaboratory.a. Soil samples for testing to determine particle size distribution, moisture content, liquidand plastic limits, CBR (California Bearing Ratio), Mr (resilient modulus), etc.b. Undisturbed (e.g., Shelby tube) samples for testing to determine consolidation and shearstrength parameters under various loading conditions.c. Rock core samples for direct visual evaluation, RQD (rock quality designation), RMR(rock mass rating), GSI (Geological Strength Index), or strength testing.5. Soil and surface water sampling and test data to assess the potential for pipe corrosion (pH andresistivity).6. Samples of stream bed materials for testing to provide information for scour analysis when theproposed construction will bridge streams or rivers as part of the foundation evaluation.7. Physical/behavioral properties of soils using in-situ testing techniques and laboratory testingmethods.8. Seismic site classification as defined by AASHTO LRFD.9. The capacity for the bearing material to support loads at various depths beneath sites whereembankments, structures, and/or structural components (foundations) will be located.10. Stability of soil and rock slopes for cut and fill conditions, including the strength and settlementcharacteristics of the soil that is beneath proposed embankments.III-4

October 201711. The anticipated magnitude and time rate of settlement owing to the applied loads of the proposedearthwork and/or structure(s). If settlement determinations exceed VDOT’s requirements, thegeotechnical study shall provide site improvement design to limit settlement.12. Geologic constraints or conditions that may have an adverse effect on the project.Prior to conducting any subsurface exploration program, the scope of work for the project is typicallydefined by the project scoping report prepared by the Central Office L&D (Location and Design) Divisionor the district’s L&D Section. Such definition shall include a copy of any proposed structure layoutsindicating the proposed locations of bridge substructure elements and any retaining walls. The definitionof the scope of work will typically include the major project elements including proposed embankments,cut slopes, new pavements, pavement rehabilitation areas, retaining walls, sound walls, minor structures,stormwater management facilities, foundation elements and the need to address scour.It is the obligation of VDOT to coordinate with the on-call consultant to convey the design elements ofthe project to facilitate their execution of an appropriate geotechnical engineering program.It is the obligation of design-build contractors and PPTA concessionaires to fulfill the minimumrequirements of this MOI upon contract award. Background data provided in the RFP can beincorporated into such efforts, as deemed appropriate by the professional engineer in responsible chargeof the effort.Local Assistance Projects and private land development projects intended to be brought into the VDOTnetwork of roads shall also include geotechnical engineering studies that conform to the requirements ofthis MOI.III-5

July 2019SECTION 302 ADMINISTRATIVE REQUIREMENTSAdministrative requirements relate to all field explorations performed by or for VDOT.302.01 SafetyAll field exploration and other project-related activities shall conform to all applicable safetyrequirements of OSHA (U. S. Department of Labor, Occupational Safety & Health Administration),VOSH (Virginia State Occupational Safety and Health) and VDOT. On-call consultants are responsiblefor ensuring that all field personnel (including subconsultants), have the requisite training and/orcertifications to perform their assigned tasks safely.302.02 Existing Utility Protection“Miss Utility” shall be notified at least 72 hours in advance of any subsurface exploration. Miss Utility’smarking service includes public utilities. Many of VDOT’s utilities (i.e., culverts, wiring, etc.) andutilities on private land are considered “private” as they are not owned by designated public utilitycompanies. To protect the private utilities of VDOT or neighboring landowners, work on such land mayrequire the services of private utility locating companies.302.03 Landowner NotificationNo investigation shall be undertaken on any property that is not within VDOT’s right-of-way without firstnotifying the landowner in accordance with 33.2-1011 of the Code of Virginia. This restriction includescrossing of property by personnel and equipment to gain access to another property where aninvestigation will be conducted. Property belonging to other government bodies, agencies or institutions,and highway property that is not part of the public road system, is also included in this restriction.Advanced notification prior to entry onto such property is required.The right-of-entry notification process should begin at least 35 days prior to the estimated date forproperty entry. The 35 day timeframe allows for additional outreach and coordination with propertyowners that are either nonresponsive or deny permission to enter the property, as necessary.The first notification, entitled “Permission to Enter,” shall follow the provided template and contain thefollowing:a. Completed, “Permission to Enter” template letter on VDOT letterhead;b. Attachment 1 for the template letter: Entity List with the below project-specific information:1. specific dates of entry;2. name of the entities entering the property;3. number of persons per entity for whom permission is sought;4. purpose for which entry is made; and5. fieldwork to be performed by each entity; andc. Prepaid postcard with project information and mailing label. The Permission to Enter templatedirects property owners to return the prepaid postcard as an indication of their approval forVDOT to enter the property.As illustrated in Appendix A, the complete Permission to Enter notification (first notification) shall besent any one of the following three ways:(i)Certified mail with return receipt;(ii)Overnight courier; orIII-6