A rational approach to the selection of soil and rock properties for engineering design can be summarized as a logical twelve-step process consisting of 3 primary steps.
- site investigation and field testing,
- laboratory testing and interpretation, and
- Engineering design
This step-by-step process flow chart is presented on Figure 1, A brief description of each step of this process is presented below.
first stage Site check and field test
step 1 [Review Available Information
The best place to start the process of material property selection is to review any and all information that may be available. There are several sources for this information, many of the sources being in the public domain and readily available at modest expense.
Step-2 [Identify Required Material Properties]
No investigation should be initiated without establishing specific goals that relate to design and construction issues that must be considered (i.e., performance requirements), engineering properties required, and the type of structure to be constructed. Is.
step 3 [Plan Site Investigation]
Historical information, which will provide estimated subsurface conditions, combined with knowledge of the specific design will allow an efficient site specific investigation strategy to be developed. Contingency plans should be considered based on the anticipated variability in subsurface conditions. Sampling gaps should be identified and an in situ testing program developed.
step 4 [Conduct Site Investigation and Field Testing]
After the strategy of investigation is prepared, it is ready to be implemented. During field work the Geotechnical Design Engineer should be informed of the findings and the number and types of samples should be amended and tests scheduled as needed.
Step-5 [Describe Samples]
The results of the field test program and subsequent laboratory identification of samples should be compared with anticipated conditions based on historical information. Selected laboratory samples may be reviewed by the design engineer to obtain first-hand observations. These samples should be used to perform simple laboratory index tests.
step rate 6 [Develop Subsurface Profile]
Using the results of field investigations and laboratory index tests, a detailed subsurface profile should be developed by a geotechnical design engineer. It is helpful at this stage to review the initial site check objectives and expectations that the content is in line with expectations.
Step-7 [Review Design Objectives]
An ongoing assessment of the area and available laboratory data relative to the design objectives should be carried out during the implementation of the site investigation. If adjustments are needed or if additional data requirements are identified, procedures should be initiated to obtain the required information.
Phase 2 Laboratory Testing and Test Interpretation
Step-8 [Select Samples for Performance Testing]
Before starting a project-specific laboratory test program, the design engineer should review the recovered samples and confirm the test (i.e., type, number and required test parameters). If possible, selected samples should be extracted in the laboratory and reviewed by the design engineer.
Step-9 [Conduct Laboratory Testing]
Once the samples are reviewed and the test program confirmed, it is time to continue with the index test and start the performance-testing program (with index test correlation for quality assurance). Preliminary results should be provided to the design engineer for review.
Step-10 [Review Quality of Laboratory Data]
If the data and interpreted laboratory test results are not in line with expectations or if the results indicate that the sample was tampered with, it is necessary to review progress and make adjustments. On some projects, the results at this stage can be used to plan and initiate a more detailed and focused phase of investigation. A phased investigation approach is particularly helpful on large projects and in cases where there are many unknowns about subsurface conditions or specific project requirements before a proposed site investigation program can be conducted.
Step-11 [Select Material Properties]
Laboratory and field test results should be interpreted and compared to project expectations and requirements. The role of the design engineer is important at this stage as the full integration of field and laboratory test results must be combined with site-specific design. If test results are not completely consistent, causes should be evaluated, poor data eliminated, and similarities and trends identified in the data. It may be necessary to return to the laboratory and take out the sample, additional review of selection and testing.
step 3 Engineering design
Step-12 [Perform Design]
In this final stage, the design engineer has the necessary information regarding the properties of the soil and rock to complete the design. In addition, the design engineer also has a direct knowledge of the variability of deposits and material properties. Design activities can proceed with knowledge of these properties and variability.
In particular, the selection, laboratory testing, and summarization of the correct engineering assets are often poorly performed. This twelve-step process requires rigorous attention to assure efficient and thorough testing and testing programs, especially since many projects are fragmented in which drilling, testing and design is done by different parties.