Study guide
Driven Piles: Axial Capacity and Settlement
PE Civil: Structural Exam
Track your progress as you read
Finished sections get a check mark.
1 Exam Identity and Reference Workflow
2026 PE Civil: Structural Identity, Format, and Scoring Electronic Handbook, Design Standards, Units, and Version Control
2 Chapter 2: Gravity and Construction Loads
2.1 Dead Loads and Self-Weight 2.2 Live Loads, Reduction, and Load Placement 2.3 Construction-Stage Loads
3 Environmental Loads
Wind Loads and Pressure Paths Seismic Loads and Lateral Force Distribution Snow, Rain, and Ice Loads
4 Moving, Impact, and Lateral Soil Loads
Vehicular, Crane, and Other Moving Loads Impact and Dynamic Allowances Earth Pressure and Surcharge Loads
5 Chapter 5: Load Paths and Combinations
5.1 Tributary Areas and Complete Vertical/Lateral Load Paths 5.2 Strength and Service Load Combinations
6 Reactions, Diagrams, and Basic Axial Effects
Free-Body Diagrams, Reactions, Shear, and Moment Qualitative Diagrams, Influence Lines, and Critical Placement Axial Tension, Compression, and Deformation
7 Chapter 7: Axial Systems and Shear Effects
7.1 Trusses, Braces, and Column Axial Force 7.2 Shear Stress, Shear Flow, and Built-Up Sections 7.3 One-Way, Two-Way, Punching, and Interface Shear Effects
8 Flexure
Section Properties and Elastic Flexural Stress Beam and Slab Flexural Load Effects Biaxial and Unsymmetrical Flexure
9 Combined Stress and Deflection
Combined Axial and Flexural Stress Principal Stress, Mohr's Circle, and Combined Shear Elastic Deflection Methods
10 Chapter 10: Serviceability, Torsion, and Stability
10.1 Serviceability: Deflection, Drift, Vibration, and Ponding 10.2 Torsion and Warping Effects 10.3 Buckling, Effective Length, and Second-Order Stability
11 Fatigue, Robustness, Thermal, and Bearing Effects
Fatigue and Progressive-Collapse Concepts Thermal Deformation and Bearing/Contact Stress
12 Inspections, Submittals, and Adjacent Facilities
Special Inspections and Verification Duties Shop Drawings, Submittals, RFIs, and Delegated Design Construction Effects on Adjacent Facilities
13 Chapter 13: Temporary Works and Safety
13.1 Formwork, Falsework, Scaffolding, Shoring/Reshoring, Bracing, and Anchorage 13.2 Construction, Roadside, and Work-Zone Safety
14 Soils and Core Concrete Properties
Soil Phase Relationships and Classification Soil Strength, Permeability, and Compressibility Fresh and Hardened Concrete Properties
15 Chapter 15: Prestressed Concrete and Steel Properties
15.1 Reinforced, Precast, Pretensioned, and Post-Tensioned Concrete Materials 15.2 Structural and Cold-Formed Steel Properties 15.3 Steel Toughness, Weldability, Corrosion, and Temperature Effects
16 Timber, Masonry, and Material Conformance
Timber Properties and ASD Design Values Masonry, CMU, Mortar, Grout, and Brick Veneer Properties Concrete and Masonry Test Methods Steel, Timber, and Other Material Specification Conformance
17 Horizontal Members I
Steel Beams and Girders Reinforced Concrete Beams and Slabs Timber and Masonry Horizontal Members
18 Chapter 18: Diaphragms and Vertical Members
18.1 Diaphragms, Collectors, Struts, and Composite Slabs 18.2 Steel Columns and Beam-Columns 18.3 Concrete Columns and Bearing Walls
19 Shear Walls, Trusses, and Frames
Shear Walls and Vertical Lateral Members Trusses and Braced Systems Moment Frames and Stability Systems
20 Composite/Bridge Systems and Bolted Connections
Composite Construction and Structural System Selection Bridge Systems and Load Distribution Bolted Steel Connections
21 Chapter 21: Welded, Embedded, and Anchored Connections
21.1 Welded Steel Connections 21.2 Bearing, Embedded, and Precast Connections 21.3 Anchors, Post-Installed Anchors, and Wood/Masonry Connections
22 Shallow Foundations
Isolated, Spread, and Strip Footings Combined and Strap Footings Mat Foundations and Foundation Slabs
23 Deep Foundations
Driven Piles: Axial Capacity and Settlement Drilled Shafts, Piers, and Caissons Pile Groups, Caps, and Lateral Deep-Foundation Response
24 Chapter 24: Retaining Structures
24.1 Lateral Earth/Water Pressure and Drainage 24.2 Sliding, Overturning, Bearing, and Global Stability 24.3 Concrete Cantilever, Gravity, and Basement Walls 24.4 Sheet-Pile, Anchored, and Mechanically Stabilized Earth Walls
Driven Piles: Axial Capacity and Settlement
Key Takeaways Explain This Topic AI
Driven-pile geotechnical resistance combines usable positive shaft resistance and toe resistance, while structural pile resistance is a separate material check
Negative skin friction or downdrag acts downward as load and must not be added to positive shaft resistance
Effective stress, soil layering, groundwater, pile displacement, and the neutral plane control the sign and magnitude of shaft transfer
Driving resistance, setup, relaxation, restrike, and load testing provide different evidence; initial refusal alone is not final axial capacity
Settlement includes pile elastic shortening and soil deformation at the shaft, toe, and group scale even when a strength check passes
Last updated: July 2026
Driven Piles: Axial Capacity and Settlement
Sign checkpoint: Positive shaft resistance and toe resistance resist downward compression. Negative skin friction acts downward with the superstructure load. Adding downdrag to resistance reverses its physical role.
Two Capacity Questions
A pile must be adequate both geotechnically and structurally. Geotechnical axial resistance is commonly organized as
Q_n = Q_s + Q_p ,
where Q_s is usable positive shaft resistance and Q_p is toe or end-bearing resistance. Structural resistance depends on the pile material and section: steel yielding/buckling/corrosion allowance, concrete compression/reinforcement and driving damage, or timber strength and durability. The smaller compatible design/allowable resistance governs.
- Quantity Direction in compression case Keep separate from
- Positive shaft resistance Upward resistance Negative skin friction
- Toe resistance Upward resistance Structural end bearing in pile cap
- Downdrag Downward load Usable side resistance
- Superstructure load Downward demand Pile self-weight/buoyancy treatment
Use one design format. Compare factored demand with factored resistance under the applicable AASHTO 8th-edition method, or service demand with allowable resistance under the stated IBC 2018 approach; do not mix them. For a 2026 exam, use the active PE Civil handbook and AASHTO LRFD 8th edition with its May 2018 errata.
Shaft Resistance and Effective Stress
Shaft resistance depends on soil type, effective stress, pile surface, installation, and relative pile–soil movement. A problem may provide unit resistance directly or an effective-stress relation such as f_s = βσ'_v . Integrate layer by layer:
Q_s = Σ(f_s p ΔL) ,
where p is pile perimeter. Use submerged unit weight below groundwater when building effective overburden; do not use total saturated weight and ignore pore pressure. Different methods apply to cohesive and cohesionless soils, so use the supplied parameters rather than blending an adhesion factor with a beta method.
Toe resistance is Q_p = q_p A_p with the applicable limiting resistance, bearing stratum, pile type, and settlement criterion. A strong thin layer over weak soil may punch or settle; a calculated high point resistance is not automatically usable.
Negative Skin Friction and the Neutral Plane
If surrounding soil settles more than the pile—because of new fill, consolidation, groundwater lowering, or another cause—it drags the pile downward. Above the neutral plane , soil movement relative to the pile creates negative skin friction. Below it, the pile can move downward relative to soil and mobilize positive resistance. The neutral plane is also important for settlement and maximum axial force in the pile.
Downdrag is not necessarily applied like a transient live load. Follow the governing load combination and resistance model. Coatings or sleeves may reduce drag only when their performance is justified. Group installation and fill placement can change the stress field.
Worked Compression Check
A square driven pile has perimeter p = 4.0 ft and toe area A_p = 4.0 ft² . Below the neutral plane, 30 ft of bearing soil provides problem-given positive unit shaft resistance f_s = 1.2 ksf . Toe unit resistance is q_p = 75 ksf . An upper 15-ft settling layer develops negative unit friction 0.60 ksf .
Positive shaft resistance is
Q_s = 1.2(4)(30) = 144 kips .
Toe resistance is
Q_p = 75(4) = 300 kips .
Thus geotechnical nominal compression resistance is
Q_n = 144 + 300 = 444 kips .
With a problem-given resistance factor φ = 0.45 ,
φQ_n = 0.45(444) = 199.8 kips .
Downdrag is a load:
D_D = 0.60(4)(15) = 36 kips .
If the factored superstructure demand is 150 kips and the stated 36-kip downdrag is already at the compatible factored level, total demand is 186 kips . Utilization is
186/199.8 = 0.931 ,
so this geotechnical screen passes. If structural pile design strength is a problem-given 260 kips, structural utilization is 186/260 = 0.715 ; geotechnical resistance controls. Settlement remains to be checked. Adding 36 kips to 444 kips as “skin resistance” would produce the wrong sign.
Driving, Setup, and Verification
Driving equipment must install the pile to the required elevation/resistance without overstressing or damaging it. Hammer energy, cushion, pile impedance, soil quake/damping, and stroke affect driving response. A wave-equation analysis addresses drivability and estimated stresses; a dynamic measurement interprets installation or restrike response; a static load test directly observes load–movement behavior under its procedure.
Some soils exhibit setup , an increase in resistance after driving as excess pore pressure dissipates and soil structure recovers. Others can relax. End-of-driving resistance therefore may differ from restrike or long-term resistance. Refusal can reflect a hard layer, inadequate hammer energy, plugged toe, damage, or temporary pore-pressure conditions; it is not a universal proof of capacity.
Settlement and Workflow
Pile-head settlement can include elastic pile compression PL/(AE) , shaft-load-transfer deformation, toe movement, and settlement of underlying layers. A group can create a broad stress bulb and settle more than one isolated test pile. Evaluate service-level movement with the stated load-transfer or settlement method.
Draw layers, groundwater, pile geometry, and neutral plane.
Calculate positive shaft and toe resistance with compatible parameters.
Add superstructure load, downdrag, and other demands with correct signs.
Apply one resistance/load format and compare geotechnical and structural capacities.
Check driving stresses, installation criteria, setup/relaxation, and verification data.
Check single-pile and group settlement at service load.
A strength pass does not erase an installation defect or an excessive settlement.