Engineering Presentation

Basic Soil Mechanics Soil type classification Gravel, sand, silt, clay Soil strength classification Granular soils (sand and gravel) Loose Dense Cohesive soils (silt and clay) Soft - toothpaste Hard – difficult to mark with your fingernail

Investigations Soil borings Drill holes, take samples Types of samples Undisturbed – Driven Tubes Disturbed - Bags Logs Soil tests N-Values – Drive Blow Counts Shear Strength – Direct Shear Test Moisture/density Compressibility – Consolidation Test Expansion Index Chemical Tests - Corrosion

Standard Penetration Test Standard Test Penetration Test Video

Bucket Auger Drill Rig Bucket Auger Drill Rig Video

Typical Soil Problems Fill Settlement Expansive Soil Movement Slope Creep Land Slides Liquefaction

Fill Settlement Thickness Age Soil type

Expansive Soil Shrinks when dry – summer Swells when wet – winter Plumbing leaks Timing of movement Maintenance

Examples of Poor Site Maintenance Lift and Separation Separation Between Sidewalk and Wal l

Examples of Poor Site Maintenance Separation Between Landing and HousePavement Damage

Examples of Poor Site Maintenance Pavement Damage

Examples of Poor Site Maintenance Pavement Damage Wall Damage

Examples of Poor Site Maintenance Wall DamageWall Tilt

Examples of Poor Site Maintenance Wall Damage Slope Between Building and Wall

Slope Creep Upper 5 to 10 feet – 3:1 (horizontal: vertical) or steeper slopes Usually expansive soils Slope maintenance

Slope Creep

Effect of Poor Slope Maintenance Wall is Tilted Crack in Seam Between Ceiling and Wall

Effect of Poor Slope Maintenance Wall is Tilted Cracks in Foundation

Effect of Poor Slope Maintenance Crack in Wall Crack Radiating From Window

Landslides Deep (typically more than 5 feet) Large, affecting more than one property Different types mud flows – very fast Circular – slow – 1inch per year or less

Landslides Landslide Video

Signs of Movement

Slope Movement

Foundation Clearances From Slope

Examples of Lateral Movement

Liquefaction Loose sand below water table during earthquake. Liquefaction Potential Maps Definition of Water Table

Pier Spacing Pier spacing is usually 5 feet to 7 feet, depending on foundation loads. Some buildings are heavier than others (masonry v. wood frame, multi-story vs. single-story). Some buildings have interior and exterior spread footings that support heavy loads. Most footings are designed to support 1500 psf – 2500 psf. 5’ x 5’ footing could support 62,500 lbs. 2’ wide perimeter footing could support up to 5,000 lbs/ft.

Typical Residential Building Loads

Types of Building Loads Line Loads – Along exterior walls 1000 lbs/ft./floor (typical) Concentrated Loads – Below columns 2000 lbs/sq. ft. (typical) 5 ft. square footing = 50,000 lbs

Pier Spacing Pier Design Capacity 75 kips to 87 kips ultimate 37 kips to 43 kips allowable Helical Piers – tension or compression 52 to 249 kips ultimate 23 to 131 kips allowable

Pier Spacing Foundation Strength During Lift Depends on concrete strength Steel placement Dimensions 7 ft. Typical for single story – spacing usually dependent on concrete strength 6 ft. Typical for two-story – spacing usually dependent on concrete strength

Test Piers Test piers provide very useful information. Sometimes better than borings.

Push Pier Graph

Helical Pier Graph

Push Pier Graph

Compaction Grouting Injecting grout into loose soils will densify the soils Denser soils are stronger, less likely to settle 10% - 20% increase in density is usually the goal.

Compaction Grouting

Soil Densification Using Foam Similar to grouting – install material in the ground to displace and densify soils. Works best in loose fills, with voids Need to do DCP or other testing to estimate foam quantities.

Typical Example Foam Injection

Corrosion Electro-chemical attack on buried metal Some soils are more corrosive than others Usually not an issue if galvanized piers are used Some jurisdictions require a study

Battered Helical Anchors To resist lateral loads Different angles –different combination of lateral and vertical loads

Lateral Loads

When Should You Always Call An Engineer? Buildings less than 10 years old Hillsides affecting structure More than 2-story buildings Buildings with irregular footprints Buildings with more than 3 inches differential Buildings with a history of plumbing leaks Properties with post construction engineering reports Buildings that have been part of litigation

Is the recommended scope of repair appropriate? Are there risks that EagleLIFT and the owner would like to know about? Are you “over-selling” the job? “We won’t cause any cracks”. “There will be no further movement”. “Our system is guaranteed”. “All the existing cracks will close up or disappear”. All estimates should be subject to results of engineering. An engineer can help you be more clear about potential risks with the client.

Industry Standards Foundation and Slab Tilt Construction Tolerance¼”/20 ft. = 1/960 Human Perception2”/20 ft. = 1/125 Structural Damage1”/20 ft. = 1/240

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