Untitled Flashcards Set

SITE EXPLORATION & CHARACTERIZATION – STUDY GUIDE (FULL)

🔹 PURPOSE & OBJECTIVES

• Subsurface conditions are mostly unknown and not visible

• Exploration informs design and construction decisions

• Reduces risk of failures and construction delays

Main Objectives:

• Determine soil/rock stratigraphy

• Locate groundwater table

• Collect samples for lab testing

• Evaluate soil properties (strength, compressibility, etc.)

• Identify hazards like soft zones or collapsible soils

🔹 TYPES OF TESTING: IN-SITU VS. EX-SITU

🧪 In-Situ Testing (on-site)

• Soil tested in its natural position without removal

• Useful in clean sands, difficult-to-sample soils

• Usually cheaper, allows for more data points

• Examples:

  • Standard Penetration Test (SPT)

  • Cone Penetration Test (CPT)

  • Pressuremeter Test (PMT)

  • Vane Shear Test (VST)

  • Dilatometer Test (DMT)

  • Plate Load Test

  • Field Density Tests (FDT)

  • Pocket Penetrometer

⚗ Ex-Situ Testing (laboratory)

• Soil is extracted and tested in lab conditions

• Higher control, more precise

• Some tests require undisturbed samples

🔹 COMMON IN-SITU TESTS

🔹 COMMON EX-SITU (LAB) TESTS

🔹 5-STAGE SITE EXPLORATION WORKFLOW

1⃣ DESK STUDY

• Collect existing data (maps, past reports, aerial photos)

• Assess geology, groundwater, previous construction

2⃣ SITE RECONNAISSANCE

• Visual inspection (erosion, vegetation, old structures)

• Mark boring locations

• Identify access & logistical issues

3⃣ SUBSURFACE EXPLORATION

Boreholes & Sampling

• Use flight augers, casing, slurry, or hollow-stem augers

• Retrieve disturbed or undisturbed samples

• Maintain boring logs

Groundwater

• Use observation wells

• Look for perched water tables

• Use electronic probes

Exploratory Trenches

• Good for shallow (<3m) investigations

4⃣ LABORATORY TESTING

• Classify soils (grain size, plasticity)

• Determine strength, compressibility, permeability

• Match test type to sample quality (undisturbed vs disturbed)

5⃣ GEOTECHNICAL REPORT

Includes:

• Subsurface profiles & cross-sections

• Lab and field test data

• Groundwater observations

• Recommendations: foundations, grading, retaining walls, etc.

📐 NSCP REQUIREMENTS (Section 303)

🔹 ECONOMIC OPTIMIZATION

• Cost of Exploration vs Risk of Failure

• Handy’s Rule:

  • Uniform soil: few precise tests

  • Variable soil: many cheaper tests

🧠 QUICK RECALL TERMS

• SPT = Blow counts (N-value), standard test for sands

• CPT/CPTU = Continuous resistance & pore pressure

• PMT/DMT = Expansion-based stress-strain behavior

• Atterberg Limits = Soil consistency states

• Proctor Test = Optimum moisture content

• Triaxial/Direct Shear = Strength parameters
  
  SITE EXPLORATION & CHARACTERIZATION

  📍 Objectives of Site Investigation

  • Determine soil/rock profile

  • Assess groundwater conditions

  • Evaluate geotechnical properties

  • Identify hazards (e.g., landslides, liquefaction)

  • Inform foundation design

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  🧪 IN-SITU TESTING METHODS

  1. Standard Penetration Test (SPT)

  • Measures resistance to driving of a split spoon sampler

  • Conducted in boreholes

  • Gives N-value (number of blows for 30 cm penetration)

  • Used for density, strength, and bearing capacity

  • Corrections: overburden pressure, energy efficiency

  2. Cone Penetration Test (CPT)

  • Cone pushed at 2 cm/s

  • Measures:

    • qc: cone resistance

    • fs: sleeve friction

    • u2: pore water pressure (if piezocone)

  • Used for stratigraphy, soil classification, undrained shear strength

  3. Vane Shear Test

  • For soft clays

  • Measures undrained shear strength

  • Vane inserted into soil, rotated to cause failure

  4. Pressuremeter Test

  • Measures lateral deformation

  • Cylindrical probe expands against borehole walls

  • Obtains modulus of subgrade reaction, pressure-strain curve

  5. Dilatometer Test (DMT)

  • Flat blade with expandable steel membrane

  • Measures horizontal stress, modulus, undrained shear strength

  6. Plate Load Test

  • Steel plate loaded on site

  • Measures bearing capacity, settlement characteristics

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  🧪 EX-SITU (LABORATORY) TESTING METHODS

  1. Moisture Content (Oven Drying Method)

  • Measures water content by drying sample at 105–110°C

  2. Atterberg Limits Test

  • Determines:

    • Liquid Limit (LL)

    • Plastic Limit (PL)

    • Shrinkage Limit (SL)

  • Used for soil classification

  3. Sieve Analysis

  • Determines grain size distribution for coarse-grained soils

  4. Hydrometer Test

  • Used for fine-grained soils (clay/silt)

  • Measures particle size using sedimentation

  5. Unconfined Compression Test

  • Measures unconfined compressive strength (for cohesive soils)

  • Simple, quick method

  6. Triaxial Compression Test

  • Measures shear strength parameters

  • Types: UU, CU, CD

  • Can simulate drainage conditions

  7. Direct Shear Test

  • Shear force applied along a plane

  • Measures friction angle (φ) and cohesion (c)

  8. Proctor Compaction Test

  • Determines optimum moisture content (OMC) and maximum dry density (MDD)

  • Standard & Modified methods

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  GEOLOGICAL MATERIALS USED IN CONSTRUCTION

  1. Building/Dimension Stone

  • Examples: granite, limestone, sandstone, marble

  • Properties: strong, durable, visually appealing

  • Uses: walls, columns, cladding, monuments

  • Local (PH): Romblon marble, Bicol andesite

  2. Roofing and Facing Materials

  • Properties: lightweight, durable, weather-resistant

  • Rocks: slate, schist, phyllite

  • Used for: tiles, panels, external facings

  3. Armourstone

  • Large, angular rocks for coastal protection

  • Must resist weathering, abrasion

  • Local: basalt, andesite

  4. Crushed Rock & Road Aggregates

  • Derived from quarrying and crushing hard rocks

  • Uses: base/sub-base for roads, concrete aggregate

  • PH: Basalt (Rizal), granite (Ilocos)

  5. Gravels and Sands

  • Naturally occurring (riverbeds, beaches)

  • Used for: concrete, mortar, backfill

  • Types:

    • Fine aggregate: <4.75 mm

    • Coarse aggregate: >4.75 mm

  6. Lime, Cement, Plaster

  • Derived from limestone and chalk

  • Lime: soil stabilization, mortar

  • Cement: binding agent

  • Plaster: interior/exterior finishing

  7. Clays and Clay Products

  • Fine-grained soil used for:

    • Bricks, tiles, pipes, ceramics

  • Must be plastic, moldable when wet, hard when fired

  • Local clay: Batangas, Iloilo, Bulacan