1: GEOTECHNICAL SITE INVESTIGATION AND IN SITU TESTING
- Page ID
- 123357
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 1.1: Introduction to Part 1
- This page covers geotechnical engineering principles for analyzing and designing geostructures, emphasizing soil parameters from laboratory and in situ tests. It details the Geotechnical Site Investigation process involving geology evaluation, soil sampling, and tests to assess geotechnical properties. The Geotechnical Engineer's role in interpreting subsoil data, defining soil layers, and developing a "geotechnical model" for safe design is highlighted.
- 1.2: Preliminary site exploration
- This page emphasizes the significance of a desk study and field reconnaissance in subsurface investigations. The desk study compiles essential existing data on structures and geological conditions, utilizing diverse sources like utility maps. It is followed by a field visit to evaluate site accessibility and identify potential issues, ensuring a thorough geotechnical investigation. This method seeks to reduce construction delays and costs.
- 1.3: Site exploration plan
- This page discusses the importance of site investigations in geotechnical engineering, highlighting the balance between cost and thoroughness. It emphasizes that a well-executed investigation can avert expensive repairs and failures, with geotechnical engineers leveraging guidelines and experience to determine necessary sampling boreholes based on the structure's characteristics.
- 1.4: Boreholes and sampling methods
- This page discusses the importance of sampling boreholes in geotechnical investigations to assess subsoil properties and groundwater levels. It outlines minimum borehole requirements for various structures and emphasizes sampling techniques like auger boring and rotary coring.
- 1.5: The Standard Penetration Test (SPT)
- This page covers the Standard Penetration Test (SPT), an early 20th-century soil testing method, detailing its procedure and use of blow counts to estimate soil properties like shear strength and compressibility. It emphasizes the importance of corrected SPT values for accuracy, and provides formulas for estimating different soil types' properties based on blow count and plasticity index.
- 1.6: Establishing the Geotechnical Model of a site
- This page outlines the intricate process of establishing a geotechnical model, highlighting the importance of engineering judgment and knowledge. Different engineers may interpret test results differently, resulting in varied models. Key aspects include identifying uniform soil layers and balancing layer representation, which depend on the engineer's experience. An example related to bridge construction is provided to illustrate these concepts.
- 1.7: The Cone Penetration Test (CPT)
- This page discusses the Cone Penetration Test (CPT) and its advanced version, the piezocone test (CPTu), which measure soil resistance and pore pressure but lack direct sampling. It highlights CPT's efficiency in providing continuous soil profiles, while noting its limitations in gravelly soils and the need for skilled operation.
- 1.8: Interpretation of CPT measurements to derive soil parameters
- This page discusses the importance of CPT and CPTu measurements in determining soil mechanical properties like undrained shear strength, relative density, earth pressure coefficients, and compressibility parameters. It highlights how factors like stress levels and loading history affect these properties while emphasizing the need for accurate interpretation of results.
- 1.9: The Vane Shear test
- This page discusses the vane shear test for measuring undrained shear strength (Su) of soft-to-medium clays under 50 kPa, as per AS 1289.6.2.1. A four-blade vane is used to determine peak and remolded shear strengths, with sensitivity assessed through their ratio. While effective, the test can overestimate Su due to clay viscosity, requiring a reduction factor based on plasticity index.
- 1.10: The Flat Dilatometer (DMT) Test
- This page discusses the flat dilatometer test (DMT), a soil testing method adhering to ASTM D6635 standards, used to assess lateral soil stress and stiffness in sandy and clayey soils. The test involves a stainless-steel blade with a membrane that measures gas pressures (A and B) for analyzing soil behavior.
- 1.11: Geophysical methods for soil exploration
- This page discusses non-destructive geophysical methods that analyze soil and rock properties without excavation. These quick and cost-effective techniques, including seismic surveys, electrical resistivity, and ground penetration radar, provide qualitative insights for early project planning but lack precision in geotechnical parameters. Each method has unique advantages for assessing subsurface conditions and stratigraphy.
- 1.12: References
- This page outlines various soil testing and geotechnical engineering standards and methodologies, including Australian and ASTM standards. Key methods discussed include the vane shear test, standard penetration test (SPT), static cone penetration test, and flat dilatometer method. It references academic literature on topics such as soil behavior correlations, techniques for obtaining undisturbed samples, and result interpretation for engineering applications.
- 1.13: Additional problems
- This page addresses geotechnical investigations for slope stability and deep foundation design. It presents a model from three boreholes for a cut slope, delineating four soil layers and their characteristics. Additionally, it covers a study for a tall building’s foundation, incorporating data from two boreholes and CPT soundings, resulting in specific undrained shear strength for clay and effective friction angle for sand.
- 1.14: Example 1.1
- This page details the creation of a geotechnical model for a bridge foundation derived from soil analysis conducted via three boreholes. Key actions include drilling, SPT testing, and piezometer installation to identify various soil layers. The model emphasizes the treatment of unconfined fill and consolidation of similar layers for design. It outlines the derivation of geotechnical parameters using SPT data and empirical correlations, addressing uncertainties in parameter estimations.