Louisiana Pile Driving

Pile and Caisson Drilling and Foundation Preparation (30 Questions / 60% of Exam)

Key Concepts

Pile Types and Classification

• Timber piles: Used in low-load, marine, or temporary applications; susceptible to decay above waterline; must be treated (AWPA standards) for permanent use.
• Concrete piles: Precast (reinforced or prestressed) or cast-in-place (Franki, Raymond); high compressive capacity; prestressed preferred for driving stress resistance.
• Steel piles: H-piles (end-bearing in rock), pipe piles (open or closed end); high strength-to-section ratio; susceptible to corrosion in aggressive soils.
• Composite piles: Combine two materials (e.g., concrete upper/timber lower); used where water table varies.
• Sheet piles: Interlocking steel, concrete, or vinyl; used for lateral earth retention, cofferdams, and seepage cutoff — not primarily for vertical load transfer.

Pile Resistance Mechanisms

• End-bearing: Load transferred to firm stratum (rock or dense soil) at pile tip; dominant in H-piles driven to refusal.
• Skin friction: Load transferred along pile shaft through adhesion/friction; dominant in cohesive soils (clay) and friction piles in sand.
• Most piles rely on a combination of both; design must identify which mechanism controls.

Pile-Driving Hammers

• Drop hammer: Simple, slow; used for small projects.
• Single-acting air/steam hammer: Ram lifted by air/steam, falls by gravity.
• Double-acting hammer: Air/steam powers both upstroke and downstroke; higher blow rate.
• Diesel hammer: Self-contained; most common in field; open-end (single-acting) or closed-end (double-acting).
• Vibratory hammer: Drives via vibration rather than impact; ideal for sheet piles and granular soils; not suitable for establishing bearing capacity by driving formulas.
• Hammer selection must match pile type, soil conditions, and required energy; over-driving causes pile damage.

Bearing Capacity Determination

• Dynamic formulas (Engineering News formula): Estimate capacity from hammer energy and set per blow; simple but imprecise.
• Wave equation analysis (WEAP): More accurate; models stress wave through pile; used for hammer selection and driveability analysis.
• Static load test: Most reliable; required when design loads are high or soil conditions are variable.
• Test pile programs: Establish driving criteria before production piles; include indicator piles and load tests.

(8 questions, 16% of exam)

Key Concepts

Concrete Mixture Components

• Cement types: Type I (general), Type II (moderate sulfate resistance), Type III (high early strength), Type IV (low heat), Type V (high sulfate resistance)
• Water-cementitious (w/cm) ratio: Lower ratio = higher strength and durability. Typically 0.40–0.50 for structural concrete
• Supplementary cementitious materials (SCMs): Fly ash (Class C or F), slag cement, silica fume — reduce permeability, control heat of hydration
• Admixtures: Water reducers, retarders (hot weather), accelerators (cold weather), air-entraining agents (freeze-thaw protection)

Fresh Concrete Field Testing (ASTM Standards)

• Slump – ASTM C143; measures workability/consistency
• Air content – ASTM C231 (pressure meter) or C173 (volumetric, for lightweight/porous aggregate)
• Compressive strength cylinders – ASTM C31 (making/curing) and C39 (testing); standard cylinder = 4×8 in. or 6×12 in.; test at 7 and 28 days
• Unit weight/yield – ASTM C138; used to verify concrete yield and air content

Concrete Placement Methods

• Truck chute, pump, crane and bucket, conveyor, buggy — each method has consolidation requirements
• Consolidation by internal vibration: vibrator spacing ≤ 1.5× vibrator radius of action; do not use vibrator to move concrete horizontally
• No employee shall ride concrete buckets (§1926.701(d)); no work under elevated buckets (§1926.701(e))

Formwork (§1926.703)

• Definition: Total system — forms, shores, reshores, braces, hardware (§1926.700(b)(2))
• Must be designed by or reviewed by a qualified person capable of supporting all vertical and lateral loads
• Lateral pressure on forms depends on concrete unit weight, rate of placement, temperature, and admixtures (ACI 347)
• Shoring/reshoring: Reshoring required when original shores are removed before concrete reaches design strength (§1926.700(b)(6))
• Stripping: Only after concrete reaches adequate strength — determined by qualified person; construction loads require qualified structural determination (§1926.701(a))
• Formwork drawings and plans must be available at the jobsite (§1926.703(a)(2))

(6 questions, 12% of exam)

Key Concepts

Estimating & Bidding - Underground utility work estimates must account for trench depth, soil classification, dewatering needs, shoring requirements, and surface restoration — all of which affect unit costs significantly. - The bid price builds upward: direct costs → labor burden → equipment costs → overhead → markup → bond.

Equipment Costs - Ownership costs include depreciation, interest/investment cost, insurance, taxes, and storage. - Operating costs include fuel, lubricants, tires, repairs/maintenance, and wear items. - Rental cost is an alternative to ownership; always compare total cost of ownership vs. rental rate × expected hours. - Equipment spreads (linked production systems) must be balanced — a bottleneck machine limits the entire system output.

Labor Burden - Labor burden = base wage + payroll taxes (FICA, FUTA, SUTA) + workers' compensation insurance + fringe benefits (health, pension, etc.). - Burden rates typically add 30–50% on top of base wages; always apply burden before calculating overhead and markup. - Overhead covers home office and field indirect costs; typically expressed as a percentage of direct costs (commonly 10–15%). - Markup (profit) is applied to the fully burdened, overhead-loaded cost; do not apply markup to bond premium.

Productivity Rates & Correction Factors - Baseline productivity assumes ideal conditions (good soil, operator efficiency = 1.0, favorable job conditions). - Correction factors adjust for: operator skill, job conditions (tight quarters, slopes), material type, altitude, and equipment age. - For pile driving: soil resistance, pile type, hammer energy, and set per blow all affect production rates. - Production = (ideal output) × (all applicable correction factors).

Bonding Requirements - Bid bond: guarantees contractor will enter contract if awarded (typically 5–10% of bid). - Performance bond: guarantees completion of work per contract terms (100% of contract value). - Payment bond (Labor & Material): guarantees subcontractors and suppliers will be paid (100% of contract value). - Louisiana public work contracts over $25,000 require both performance and payment bonds (La. R.S. 38:2216). - Bond premium is a direct project cost; it is not marked up for profit.

6 questions | 12% of exam | Reference: 29 CFR 1926

Key Concepts

Contractor Accident Prevention Responsibilities (§1926.20)

• The prime contractor retains overall responsibility for OSHA compliance even when work is subcontracted. Prime and subcontractors share joint responsibility for subcontracted work.
• Employers must initiate and maintain safety programs, including frequent and regular inspections by competent persons.
• Unsafe equipment must be tagged, locked out, or physically removed — not just flagged verbally.
• Only employees qualified by training or experience may operate equipment.
• PPE failures are cited per employee — each unprotected worker is a separate violation.

Safety Training (§1926.21)

• Employers must instruct each employee in recognition and avoidance of unsafe conditions specific to their work environment.
• Employees handling hazardous substances must receive instruction on safe handling, personal hygiene, and PPE requirements.

PPE Requirements for Pile Driving

• Hard hats, safety glasses, hearing protection, and steel-toed boots are standard for pile driving operations.
• PPE must be provided to each individual employee — a program alone is insufficient.

Fall Protection (Subpart M – §1926.500–503)

• Fall protection required at 6 feet or more above a lower level in construction.
• Three accepted systems: guardrail systems, safety net systems, and personal fall arrest systems (PFAS).
• Guardrails: top rail at 42 inches (±3 in.), mid-rail at 21 inches, capable of withstanding 200 lbs of force.
• Safety nets must be installed within 30 feet below the working surface.
• Personal fall arrest systems must limit free fall to 6 feet and arresting force to 1,800 lbs.

Crane & Dedicated Pile Driver Safety (Subpart CC – §1926.1400+)

• All cranes/derricks used in pile driving must be operated by a qualified/certified operator.
• A competent person must inspect the equipment before each shift.
• Cranes must not be used beyond their rated load capacity; load charts must be in the cab.
• Dedicated pile drivers (not cranes) are also covered under Subpart CC requirements.