UNIT III - Geotechnical Site characterization .pptx

It describes the various methods involves in geotechnical site investigation

1. UNIT III: SITE CHARACTERIZATION Module Tutor: Karma Dema

2. Outline Introduction The need for site characterization Objectives of site characterization Site characterization process: an integrated approach Site characterization flowchart Reporting Planning and design of characterization study Role of codes of practice and guidelines Quality management of site investigation Scope of investigation Selection of field equipment and test methods Cost considerations Offshore investigations Contractual aspects

3. Introduction Site characterization may be defined as the three-dimensional engineering geologic description of the surface and subsurface of the location for intended construction of engineering works, for habitation, commerce, resource development, mitigation of natural hazards or conduct of groundwater protection, waste management or environmental remediation. Site exploration and site characterization are related but they serve different purposes and involve distinct processes. While site explortation focuses on gathering initial subsurface data to determine the suitability of a site , site characterization goes deeper into understanding the detailed geotechnical properties necessary for design and construction .

4. The Need for Site Characterization Site/soil exploration provides a preliminary overview of subsurface conditions, whereas site characterization is needed for a thorough and detailed understanding. It is needed for: Accurate design : ensuring that the soil and rock properties are well understood so that the design parameters for foundations, earthworks, and other structures are accurate. Risk mitigation : Identifying and understanding potential geotechnical hazards, such as liquefaction or slope instability, that might not be apparent during the exploration phase. Project optimization : optimizing construction methods and materials based on a detailed understanding of the subsurface environment.

5. Goals/objectives of site characterization: Identification of sites likely to experience ground displacement from fault movement; Identification of the stability of a site's configuration; Establishment of the need to improve the engineering characteristics of the ground so as to resist damaging deformation ; Establishment of the need to control groundwater to prevent excess pore pressure and subsequent failure under the involved structural loads; and Identification of the potential for creating green space not only for soical gain but also to incorporate active faults and existing geohazards.

6. Purpose and Scope of Site Characterization There are published guidance on site characterization, but it is the responsibility of the engineering geologist in charge of each project to define the scope of the characterization in order to meet the design needs of the planner and engineer. The needs fall into seven basic categories: a 3-dimensional description of the project site to the depth of influence (i.e. where the maximum applied (live and dead) static load from the intended use of the site has dropped to 10%); a description of the length and breadth of the proposed site and of the area beyond the property boundaries to such a distance as will encompass any anticipated effect of the activities contemplated at the site;

7. Purpose and Scope of Site Characterization the identification of ground that may be affected by displacement, volumetric change (shrinkage or swelling), or other forms of loss of physical support or chemical integrity relating to the intended construction; the discovery or prediction of ground instability above, below, on, or adjacent to the site; the detection and measurement of groundwater conditions (including perched and transient conditions) that may affect the construction, operation, or maintenance of the proposed works (including the estimation of annual variations and chemical composition, and in particular the potential to harm human health or the environment);

8. Purpose and Scope of Site Characterization the discovery or prediction of conditions that may adversely affect the rate, progress, or method of construction of the project; and the detection or prediction of ground conditions that may be unsafe or endanger the health of people engaged in construction, or in work, visitation, occupancy of the developed site.

9. Elements of site characterization

10. Elements of site characterization

11. Elements of site characterization

12. Elements of site characterization

13. Elements of site characterization

14. Key considerations of site characterization

15. Key considerations of site characterization

16. Site Characterization Process: An integrated approach Site Characterization Flowchart: The flowchart for site characterization is more detailed that that of site exploration, typically involving the following steps: Comprehensive desk study Site reconnaissance Detailed field investigation: borehole drilling, In-situ testing (SPT, CPT, pressuremeter and vane shear tests), Geophysical surveys (SRT, ERT, GPR) Laboratory testing Data integration and analysis: geotechnical modeling, engineering analysis, risk assessment Reporting: Geotechnical report

17. Site Characterization Process: An integrated approach Components of Geotechnical Report: Introduction - background, objectives, scope, study location & description. Methodology - desk study, site reconnaissance, & field investigation. Site conditions - geological & hydrogeological conditions, soil and rock material properties, groundwater conditions and monitoring results. Results and analysis: summarized results of in-situ, laboratory and geophysical tests. Interpretation and recommendations - foundation design (type, depth & dimensions) recommendations, earthwork & excavation guidance, groundwater management strategies, recommendations for dealing with geotechnical risks. Risk assessment and mitigation Appendices - borehole logs, test results data sheets, models and calculations, photographs, maps and drawings.

18. Planning and Design of Characterization Study Role of codes of practice and guideline Codes of practice and guidelines provide standardized procedures and criteria for conducting SI, ensuring consistency and reliability in the data collected. Adhering to those codes ensures compliance with regulations, which is crucial for project approval. Codes incorporate safety and risk managemnt practices thus preventing accidents and mitigating geotechnical risks during investigation. Following the codes and guidelines keeps the investigators up-to-date with the latest & effective methods. E.g., ASTM (American Society for Testing and Materials) standards, IS (Indian standard) codes.

19. Planning and Design of Characterization Study Quality Management of Site Investigation Develop Quality Assurance plan to ensure that all phases of site investigation meets the required standards. Implementing Quality Control procedures (calibration of equipment, validation of test results) during data collection, testing and reporting. Ensure all the personnel involved in SI are adequately trained and competent. Engage independent auditors (third-party audits) to review the investigation process and outcomes to verify compliance with the quality assurance and quality control plans.

20. Planning and Design of Characterization Study Scope of Investigation Scope of the investigation is defined based on the specific requirements of the project, such as the type of structure being built, expected load, and environmental conditions. Depending on the site conditions, for example, a site with complex geology may require more extensive investigation. Depending on the depth of investigation and the extent of the area to be covered. Decide on the types and numbers of tests to be conducted to ensure comprehensive data collection.

21. Planning and Design of Characterization Study Selection of Field Equipment and Test Methods Based on factors like: Soil and rock types - For example, cohesive soils may require vane shear test, while non-cohesive soil might be better suited for SPT or CPT. Investigation depth Site accessibility - remote and difficult sites may require portable equipment Project complexity - Complex projects may require advanced geophysical methods in addition to standard borehole and in-situ testing.

22. Planning and Design of Characterization Study Cost Considerations Cost management Budget planning: estimation of costs for all phases of investigation Cost-benefit analysis: evaluating benefits of different investigation methods relative to their costs. Optimize investigation methods without compromising the quality of the data. Budget considerations Field investigation costs (equipment rental, personnel costs, logistics) Laboratory testing costs Allowances for unexpected site conditions, additional testing, or delays.

23. Planning and Design of Characterization Study Offshore investigations Offshore investigation are usually done in order to study the marine environments, typically for projects located on or beneath the seabed. They are crucial for the planning, design, and construction of offshore structures, such as oil and gasplatforms, pipelines, subsea cables. Due to challenges in accessibility, evironmental conditions, and logistics in offshore investigation, data collection becomes challenging and methods employed differ from ground investigation. Offshore investigations are more expensive due to the need of specialized eqipment and the complexity of operations.

24. Planning and Design of Characterization Study Contractual aspects Scope definition: to ensure all parties understand the extent and limitations of the investigation. Deliverables: specification of deliverables (e.g., reports, data sets, analysis) along with timeline for delivery. Quality requirements: to ensure the investigation meets the required standards. Liability and risk allocation: clarify who is responsible for risk associated with the investigation, e.g., equipment failure, unforseen site conditions etc. Payment terms: payment schedule and additional costs if the scope of work changes. Dispute resolution: mechanisms for resolving disputes that may arise during the investigation.

25. Planning and Design of Characterization Study Contractual aspects Types of contracts: Lump sum: A fixed price contract where the scope is well-defined, and the contractor is paid a lump sum upon completion. Cost-plus: The client reimburses the contractor for the actual costs incurred, plus an agreed-upon fee. This is common in investigations where the scope may evolve. Time and materials: The contractor is paid based on the time spent and materials used. This is often used when the scope is uncertain or likely to change.

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