Geotechnical Investigations Overview

Geotechnical Investigations

• Borehole Drilling is a common method to collect soil samples for analysis.
• Borehole Logs are detailed records of soil types, penetration resistance values, and moisture content.
• Standard Penetration Resistance (N-value) is used to estimate soil strength (bearing capacity) during borehole drilling.
• N-value is measured by driving a split-barrel sampler into the soil with a hammer.
• Higher N-values indicate greater soil bearing capacity.
• Number of Boreholes and spacing is determined by the project scope and expected soil variations.
• Cone Penetration Testing (CPT) is a modern alternative to borehole drilling, providing a continuous profile of soil properties.
• CPT involves pushing a cone-shaped penetrometer into the ground at a constant rate and measuring resistance.
• Borehole Drilling provides information at specific depths, while CPT offers a continuous profile, allowing for detailed profiling.
• CPT is generally more cost-effective and faster than borehole drilling.
• CPT provides more accurate and precise data compared to potentially inaccurate borehole samples.

Geotechnical Report Recommendations

• The Geotechnical Report provides recommendations for pavement types, thicknesses, and compaction equipment based on soil conditions.
• Municipalities review geotechnical reports for project approval, ensuring adequate investigation scope and implementation of recommendations in design.
• Site Superintendents must be vigilant during grading and excavation works, as significant soil variations can occur.
• Additional Geotechnical Testing is crucial to confirm bearing capacity at various locations before placing footings.
• Site Superintendents should coordinate with geotechnical consultants during construction for review and inspection.

Environmental Site Assessment (ESA)

• ESA aims to identify and assess potential environmental contamination on a site.
• Financial Implications of site contamination include loss of property value and remediation costs.
• Prospective Purchasers can use ESA to avoid unforeseen financial liabilities.
• ESA is often required by banks to ensure no hidden contamination liability exists.
• ESA is conducted in three phases:
  • Phase 1: Visual investigation without sampling.
  • Phase 2: Detailed investigation based on sampling and laboratory analysis.
  • Phase 3: Remedial measures and Remedial Action Plan (RAP).
• Phases must proceed sequentially, with further phases triggered by the recommendations of prior phases.

ESA Phase 1

• Phase 1 investigates visible signs of past or present contamination through:
  • Site Inspection: Observing property use, hazardous materials, unidentified substances, storage tanks, odors, and other signs.
  • Review of Historical Databases: Obtaining information about past and present site uses.
  • Interviews: Gathering information from relevant persons.

Soil Chemical Analysis

• Chemical Analysis determines the quantity of each chemical constituent of soil by testing samples in a laboratory.
• Certificate of Analysis (CoA) is a tabular form summarizing the chemical analysis results.
• MOE Tables are used to compare the chemical analysis results with permissible contaminant levels for different land uses.

Onsite Soil Management

• MOE Guidelines determine the relevant MOE Table based on current and intended uses of the site.
• Soil Conforming to the MOE Table is permissible for onsite use.
• Non-Conforming Soil must be remediated, replaced, or disposed of at a designated dump site.
• Imported Soil must also comply with the applicable MOE Table for the site.

ESA Phase 3

• Phase 3 is triggered when Phase 2 identifies contamination and remediation is required.

This quiz covers the fundamental aspects of geotechnical investigations, focusing on borehole drilling techniques and cone penetration testing. Key concepts such as borehole logs, the N-value, and soil sampling methods will be explored. Assess your understanding of soil properties and testing methods used in geotechnical engineering.