Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
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- 5.2.1 Geotechnical Responsibilities in Lateral Loading Analysis
| 5.2 DESIGN TEAM ROLES The design team for deep foundations consists primarily of the geotechnical and structural engineers. Additional team members include hydraulic and civil engineers, architects, or other disciplines who may provide secondary input with regard to the design process for laterally loaded deep foundations. Because the analysis of laterally loaded deep foundations involves soil-structure interaction, it requires coordination of the combined expertise of the geotechnical and structural engineers. It is not appropriate for the geotechnical engineer to analyze laterally loaded deep foundations without a complete understanding of the structural response of the foundation or the connection of the foundation to the structure. Similarly, it is not appropriate for the structural engineer to analyze laterally loaded deep foundations without a complete understanding of how the foundation section, depth, or spacing may impact the geotechnical response under the applied loads, or how external system loads, such as seismic loads, may affect the geotechnical parameters or the surrounding soils. Therefore, a proper design of laterally loaded deep foundations must involve adequate coordination between the geotechnical and structural engineers. Often this may require an iterative process between the two disciplines, rather than simply one discipline providing input, parameters, or a check of the results of the other discipline. Typical roles for the design professionals are discussed below. These roles are based on general industry practice, including practice by some agencies. However, the roles on a specific project may vary due to local practice, contractual arrangements, or other considerations. 5.2.1 Geotechnical Responsibilities in Lateral Loading Analysis The geotechnical engineer has primary responsibility for tasks relating to the subsurface conditions. The geotechnical engineer has secondary responsibility for tasks relating to the structural design. Primary responsibility for some tasks maybe allocated to either the geotechnical engineer or the structural engineer, depending on the project type, team roles, experience or qualifications of individual team members, contractual arrangements, or other considerations. 60 The tasks relating to the subsurface conditions include defining the preliminary project geotechnical conditions, planning and executing the subsurface investigation and testing program, characterizing subsurface conditions, and development of resistance factors (which are based in part on considerations regarding the characterization of subsurface conditions. The geotechnical engineer is also primarily responsible for determining external geotechnical loads such as loads due to external soil loads (retained earth pressure, slope movement, and possible change to soil conditions (liquefaction, lateral flow or lateral spreading. In some cases, the geotechnical engineer may simply provide the required input parameters (unit weight, earth pressure coefficient, etc) for the structural engineer to develop the loads. Development of the loads also includes axial loads related to geotechnical conditions, such as downdrag, as well as assessment of load effects, such as ground settlement at the deep foundations (individual or group. Development of geotechnical design for axial loads, assessment of constructability issues, and development of construction inspection and testing requirements will also be the primary responsibility of the geotechnical engineer. Responsibilities for other tasks may vary depending on project type. For projects that are geotechnical in nature or where the loads are primarily geotechnical, such as slope stabilization or cantilevered retaining walls, the geotechnical engineer maybe primarily responsible for additional analysis and design tasks. Similarly, if projects include unusual or challenging geotechnical conditions or require specialty geotechnical construction, the geotechnical engineer may have primary responsibility definition of the project type and needs, selection of the deep foundation type and preliminary size, determination of initial foundation layout and head fixity conditions, and determination of performance criteria. Analysis of a single pile/shaft maybe the primary responsibility of the geotechnical engineer or the structural engineer. The geotechnical engineer should have primary responsibility if the analysis involves Broms method or strain wedge theory. The soil-structure interaction analysis (p-y method) involves both geotechnical and structural inputs and considerations. In some cases, these analyses are performed by the geotechnical engineer the structural engineer then reviews the results for reasonableness, and/or may perform the Structural Strength Limit State analysis. In other cases, the geotechnical engineer develops the geotechnical inputs, such as the subsurface profile for analysis and geotechnical parameters for soil and rock layers, including p-y curves or input parameters for development of p-y curves the structural engineer then performs the analyses fora single pile, including the Geotechnical Strength and Service Limit State analyses. Similarly, analysis of group behavior involves specialty computer software that includes both geotechnical and structural inputs and considerations, and maybe performed by either the geotechnical or structural engineer depending on the project roles. The geotechnical engineer will likely also have a lead role in the constructability review and development of construction documents. The geotechnical engineer should lead the development of specifications for construction or installation of foundation elements and construction inspection and testing related to foundation elements. The geotechnicap-yl engineer may also lead the development of plans or details for geotechnical construction such as slope stabilization of specialty foundation details such as micropiles or CFA piles. For other plans, details, or specifications that are primarily structural, such as pile layout for bridge foundations or structural details for drilled shafts, the geotechnical engineer should have secondary responsibility (review of work developed by others disciplines. 61 The geotechnical engineer should be responsible for aspects of construction related to geotechnical conditions or construction, such as review of submittals by specialty geotechnical contractors (installation plans, equipment, etc, oversight or review of foundation inspection and testing, and review and approval of foundation installation records. For projects that are geotechnical in nature, such as slope stabilization, the geotechnical engineer should lead the preparation of as-built records. For most other projects, the geotechnical engineer will generally have a secondary responsibility for development of construction records or as-built drawings, such as providing input or review. Download 6.03 Mb. Share with your friends:
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