California Department of Transportation
 

Office of Geotechnical Design

The Offices of Geotechnical Design provide their state highway transportation project clients with expert soils and foundations recommendations. Responsibility for transportation projects is divided primarily upon the basis of region- North, South, or West. The engineers and geologists provide geological investigations, analyses and recommendations to the districts during all phases of a project as highlighted below:

Project Planning

Assess the scope and cost of project alternatives for the Project Study Report, including literature searches, field reconnaissance, geologic mapping and subsurface exploration.Prepare geologic hazard commentary and data for use in project environmental documents. Address geologic hazard issues at public hearings, on request.

Project Design

Conduct geotechnical explorations and analyses needed to provide the project design engineer with recommendations for bridges, transportation structures, embankments, fill and cut slope design, expansive and soft soil treatment, groundwater control, seismic stability and potential liquefaction, retaining walls, alternative earth retaining structures, overhead signs, sound walls, pipe jacking, changeable message signs, landslide repair, and culvert foundations. Provide liaison with the project engineer during design so that the project design accommodates the geotechnical constraints, accurately reflects the Foundation or Geotechnical Design Report, and can be bid and built. The Geotechnical Design Report establishes a baseline understanding of geotechnical behavior and conditions and will be provided to bidders.

Provide preliminary assessment of expected site geology, seismic factors (nearest active fault and magnitude, predicted maximum horizontal bedrock acceleration, anticipated depth to bedrock, liquefaction potential) and scour potential. This information is used in initial stages of structure design. For each project, conduct all detailed geologic, seismic and geotechnical explorations and analyses needed to provide the Structures project design engineer with soil and rock engineering parameters and other recommendations for foundation design. If drilling is required, coordinate the effort with the Office of Drilling Services. If Cone Penetrometer Testing or Geophysical Testing are required, coordinate the testing with the Office of Geotechnical Support. Typical activities include:

  • Literature search
  • Surface geologic investigation
  • Subsurface geologic and geotechnical investigation
  • Submittal of a written report that includes a log of test borings.

Provide technical support to project design engineers and project managers during design so that the completed project will accommodate the site geological, seismic, and geotechnical constraints and can be cost-effectively constructed. This support is provided in the form of recommendations in Structures Foundation Reports and close personal communication with design team members during all phases of project design. The recommendations address pertinent site geological, seismic, and geotechnical factors and include any special provisions (i.e., potential construction problems, anticipated difficulties in placement of tiebacks, etc.). Included with the report is the "Log of Test Borings" (LOTB), which is a collection of all available boring data covering the site, prepared in cooperation with the Office of Geotechnical Support.

For geotechnical earthquake engineering, the geotechnical deisgn offices perform:

  • Geotechnical site characterization for dynamic soil properties
  • Dynamic site response analysis
  • Design earthquake ground motions (time histories or response spectrum) using deterministic and probabilistic methods
  • Fault rupture hazard
  • Ground failure analysis including liquefaction flow, lateral spreading, and mitigation measures
  • Soil-foundation-structure interaction (soil springs/foundation stiffness and damping matrices) analysis
  • Lateral load analysis of foundations
  • Dynamic slope stability analysis
  • Development of geotechnical earthquake engineering guidelines and standards
  • Review consultant reports regarding geotechnical earthquake engineering issues

Construction

Provide support to the Resident Engineer during construction of the geotechnical portion of projects to resolve urgent and emergency situations resulting from soils and foundation problems. Support Caltrans Construction personnel in executing change orders and resolving claims. Review significant features exposed during construction to compare actual conditions to those anticipated by the design, and to make corrective recommendations as necessary. If Foundation Testing is required, coordinate the testing with the Office of Geotechnical Support.

Maintenance

Evaluate chronic, urgent and emergency situations resulting from geotechnical problems, such as landslide repairs. Assist in development of plans, specifications and estimates for projects to correct such conditions. Contract/Externally Financed Project Oversight Assist in setting the scope of geotechnical studies for the roadway portions of projects done by consultants, work with the consultant in selecting appropriate analyses and design options, provide ongoing geotechnical review during the consultant’s work, and provide general technical oversight to assist local entities or Caltrans Consultant Services staff.

Legal

Provide expert witness testimony and support to the department in geotechnical claims and litigation cases involving the geotechnical considerations of structure foundations.