CELE Geotechnical Engineering — Foundations (Shallow and Deep)Concept Map

Concept

Shallow Foundations

Sub Concepts

• Isolated (Spread) Footing
• Combined Footing
• Strap Footing
• Mat/Raft Foundation
• Bearing Capacity Analysis
• Settlement Estimation
• Footing Sizing Formula

Relationship To Central

Primary category of surface-based load transfer methods

Concept

Deep Foundations

Sub Concepts

• Driven Piles
• Drilled Shafts
• End Bearing Capacity
• Skin Friction Resistance
• Pile Capacity Calculation
• Pile Installation Methods
• Negative Skin Friction

Relationship To Central

Primary category of subsurface load transfer methods

Concept

Pile Capacity Components

Sub Concepts

• Ultimate Point Bearing (Qp)
• Ultimate Skin Friction (Qs)
• Total Ultimate Capacity (Qu)
• Allowable Capacity (Qa)
• Safety Factor Application

Relationship To Central

Core calculation method for deep foundations

Concept

Soil Parameters & Methods

Sub Concepts

• Undrained Shear Strength (cu) — Clay
• Angle of Internal Friction (φ) — Sand
• Effective Stress (σ'v)
• Adhesion Factor (α)
• Lateral Earth Pressure Coefficient (K)
• Pile Friction Angle (δ)

Relationship To Central

Input data for foundation design calculations

Concept

Bearing Capacity Equations

Sub Concepts

• End Bearing — Clay: Qp = 9cu·Ap
• End Bearing — Sand: Qp = (cNc* + q'Nq*)·Ap
• Skin Friction — Clay (α-method): fs = α·cu
• Skin Friction — Sand (β-method): fs = K·σ'v·tan(δ)
• Group Efficiency: Qgroup = η·n·Qsingle

Relationship To Central

Mathematical framework for capacity prediction

Concept

Group Behavior & Interactions

Sub Concepts

• Group Efficiency (η)
• Overlapping Stress Zones
• Block Failure Analysis
• Individual Pile Versus Group Capacity
• Spacing Effects

Relationship To Central

Performance modification for multiple piles

Concept

Geotechnical Site Conditions

Sub Concepts

• Clay Soil Profiles
• Sand Soil Profiles
• Mixed Soils
• Consolidation Potential
• Negative Skin Friction Risk
• Recent Fill or Embankments

Relationship To Central

Environmental factors influencing foundation selection

Concept

Design Standards & Codes

Sub Concepts

• NSCP 2015 (National Structural Code)
• ACI 318 (Reinforced Concrete)
• AISC 360 (Steel Construction)
• RA 544 (Philippine Building Code)
• Safety Factors and Load Combinations

Relationship To Central

Regulatory framework for foundation design

Concept

Structural Considerations

Sub Concepts

• Footing Flexure Design
• Footing Shear Design (one-way, two-way, punching)
• Pile Head Connection
• Load Distribution Through Pile Group

Relationship To Central

Above-ground design implications of foundation choice

Concept

Special Conditions & Phenomena

Sub Concepts

• Negative Skin Friction (Downdrag)
• Consolidation Settlement
• Differential Settlement
• Liquefaction Risk
• Environmental Fill Effects

Relationship To Central

Complicating factors requiring additional analysis

To

Bearing Capacity Analysis

From

Shallow Foundations

Strength

strong

Relationship

Shallow foundations are sized and verified using bearing capacity equations and allowable bearing pressure qa

To

Pile Capacity Components

From

Deep Foundations

Strength

strong

Relationship

Deep foundation capacity is computed as the sum of end bearing and skin friction; pile capacity is the fundamental design parameter

To

Soil Parameters & Methods

From

Pile Capacity Components

Strength

strong

Relationship

Calculation of Qp and Qs depends critically on soil strength parameters (cu for clay, φ for sand) and design method (α-method or β-method)

To

Pile Capacity Components

From

Group Behavior & Interactions

Strength

strong

Relationship

Group capacity is derived from individual pile capacity multiplied by group efficiency factor η; block failure is an alternative limit state

To

Pile Capacity Components

From

Special Conditions & Phenomena

Strength

strong

Relationship

Negative skin friction (downdrag) reduces the effective skin friction contribution, lowering overall capacity

To

Bearing Capacity Analysis

From

Footing Sizing Formula

Strength

strong

Relationship

The area required is determined by A = P/qa; this connects applied load to allowable bearing pressure

To

Shallow Foundations

From

Settlement Estimation

Strength

moderate

Relationship

Settlement must be checked for shallow foundations to verify serviceability; excessive settlement may require a mat or switch to deep foundation

To

Soil Parameters & Methods

From

Bearing Capacity Equations

Strength

strong

Relationship

Bearing capacity factors and equations (Nc*, Nq*, fs) are derived from soil mechanics theory and depend on soil type and properties

To

Soil Parameters & Methods

From

End Bearing Capacity

Strength

strong

Relationship

End bearing is calculated using soil strength (cu for clay) and bearing capacity factors; it is depth-dependent and controlled by tip conditions

To

Soil Parameters & Methods

From

Skin Friction Resistance

Strength

strong

Relationship

Skin friction is computed using adhesion factor α (clay) or lateral stress coefficient K (sand); it accumulates over the shaft length

To

Consolidation Potential

From

Negative Skin Friction

Strength

strong

Relationship

Negative skin friction occurs when surrounding soil (especially recent fill) consolidates more than the pile, creating downdrag load

To

Bearing Capacity Analysis

From

Design Standards & Codes

Strength

moderate

Relationship

NSCP 2015, ACI 318, and RA 544 provide load factors, safety factors, and design requirements for foundation calculations

To

Shallow Foundations

From

Structural Considerations

Strength

moderate

Relationship

Footing flexure and shear (per ACI 318) are designed after the area is determined; moment and shear depend on bearing pressure distribution

To

Deep Foundations

From

Structural Considerations

Strength

moderate

Relationship

Pile head connections and load distribution through pile groups require structural design; capacity governs layout and pile sizing

To

Overlapping Stress Zones

From

Group Efficiency

Strength

strong

Relationship

Group efficiency η < 1 accounts for the reduction in capacity due to overlapping stress bulbs from adjacent piles in the group

To

Group Behavior & Interactions

From

Block Failure Analysis

Strength

strong

Relationship

Block failure is an alternative failure mode where the entire pile group and surrounding soil move as one unit; controls capacity when it is lower than individual pile capacity

To

Footing Sizing Formula

From

Mat/Raft Foundation

Strength

moderate

Relationship

A mat is used when the total footing area exceeds ~50% of the building footprint; sizing follows the same A = P/qa principle but as a single large footing

To

End Bearing Capacity

From

Undrained Shear Strength (cu) — Clay

Strength

strong

Relationship

In clay, end bearing Qp = 9cu·Ap; cu is the primary soil parameter controlling tip capacity

To

Skin Friction Resistance

From

Adhesion Factor (α)

Strength

strong

Relationship

In clay, skin friction fs = α·cu; α typically ranges 0.5–1.0 and depends on cu magnitude and stress history

To

Skin Friction Resistance

From

Angle of Internal Friction (φ) — Sand

Strength

strong

Relationship

In sand, skin friction fs = K·σ'v·tan(δ); φ (and the derived δ) governs frictional resistance

To

Allowable Capacity

From

Safety Factor Application

Strength

strong

Relationship

Allowable capacity Qa = Qu/FS (typically FS = 2.5–3.0); safety factor converts ultimate to service-level design value

To

Soil Parameters & Methods

From

Clay Soil Profiles

Strength

moderate

Relationship

Clay strength profile (cu vs. depth) is obtained from boring, laboratory testing, or field tests (CPT); it drives pile capacity and bearing capacity calculations

To

Soil Parameters & Methods

From

Sand Soil Profiles

Strength

moderate

Relationship

Sand density and friction angle (from SPT N-value or triaxial) determine K and δ; these control skin friction and end bearing in sand

To

Pile Capacity Calculation

From

Mixed Soils

Strength

moderate

Relationship

Mixed soil profiles (clay + sand layers) require applying the appropriate method (α or β) to each layer and summing contributions; total Qs = Σ(fs·As)

To

Skin Friction Resistance

From

Effective Stress (σ'v)

Strength

strong

Relationship

In sand, effective stress σ'v is used in fs = K·σ'v·tan(δ); accounts for pore pressure and depth

To

Skin Friction Resistance

From

Lateral Earth Pressure Coefficient (K)

Strength

strong

Relationship

In sand, K represents lateral stress state; higher K (denser, more confined sand) increases skin friction

To

Skin Friction Resistance

From

Pile Friction Angle (δ)

Strength

strong

Relationship

In sand, δ is the pile-soil friction angle; typically 0.75φ to φ depending on pile roughness; directly enters fs = K·σ'v·tan(δ)

To

Special Conditions & Phenomena

From

Consolidation Settlement

Strength

moderate

Relationship

In soft clay, consolidation settlement occurs over time after construction; if surrounding soil settles more than the pile, negative skin friction develops

To

Negative Skin Friction

From

Recent Fill or Embankments

Strength

strong

Relationship

Recently placed fill undergoes consolidation; if it settles faster than a new pile, it creates downdrag loading on the pile shaft

To

Bearing Capacity Equations

From

NSCP 2015

Strength

moderate

Relationship

NSCP 2015 adopts Philippine-specific load factors and design criteria for bearing capacity; references ACI 318 and AISC 360 for structural design

To

Structural Considerations

From

ACI 318

Strength

moderate

Relationship

ACI 318 provides reinforced concrete design requirements for footing flexure, shear, and detailing; foundation design must comply

To

Structural Considerations

From

AISC 360

Strength

moderate

Relationship

AISC 360 governs steel pile design and connections; used when piles are steel H-piles or when steel pile caps are employed

To

Design Standards & Codes

From

RA 544

Strength

moderate

Relationship

RA 544 (Philippine National Building Code) sets the legal framework; foundation design must comply with its minimum standards