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PE Construction practice questions

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Question 1Project Planning (breadth)

In construction project planning, a work breakdown structure (WBS) is best described as which of the following?

  1. A schedule of contract pay items with estimated quantities and prices
  2. A hierarchical breakdown of total project scope into manageable work packages Correct answer.
  3. A network diagram that shows logical ties between schedule activities
  4. A bar chart that plots activity durations against a calendar timeline

Explanation

The WBS decomposes the full project scope into successively smaller, definable work packages. Those packages become the common framework for estimating, scheduling, cost coding, and progress measurement. Bar charts and network diagrams are scheduling tools, and pay items are a contracting artifact.

Question 2Project Planning (breadth)

The critical path in a construction precedence network is which of the following?

  1. The path with the greatest number of activities from start to finish
  2. The shortest chain of activities that still connects start to finish
  3. The longest continuous chain of dependent activities through the network Correct answer.
  4. The path that consumes the largest share of project labor resources

Explanation

The critical path is the longest duration path through the network, so it governs the earliest possible project completion date. Activities on it have zero total float unless schedule constraints are imposed. Counting activities, resource loading, or path length in links do not define criticality.

Question 3Project Planning (breadth)

An activity has an early start of day 10, a late start of day 14, an early finish of day 16, and a late finish of day 20. What is its total float?

  1. 4 days Correct answer.
  2. 3 days
  3. 2 days
  4. 6 days

Explanation

Total float equals late start minus early start (or late finish minus early finish). Here 14 minus 10 equals 4 days, and 20 minus 16 confirms the same value. Total float measures how long the activity can slip before project completion is delayed.

Question 4Project Planning (breadth)

What is the primary purpose of a Gantt bar chart in construction planning?

  1. To document the contractual basis for excusable delay
  2. To show activity timing, sequence, and progress against a calendar Correct answer.
  3. To compute the logical dependencies required for CPM analysis
  4. To allocate project contingency to identified risk events

Explanation

A Gantt chart displays activities as bars positioned along a time scale so owners, designers, and field staff can see timing, overlap, and progress at a glance. It is a presentation and communication tool, not a dependency calculator. Logic, risk allocation, and delay entitlement are documented elsewhere.

Question 5Project Planning (breadth)

Which set of items is typically addressed in pre-mobilization planning for a new construction site?

  1. Final pay application, lien waivers, and warranty documentation
  2. Post-occupancy evaluations and long-term maintenance scheduling
  3. Site access, temporary facilities, and temporary utility services Correct answer.
  4. Punch list completion, owner training, and commissioning records

Explanation

Mobilization planning establishes how the contractor will enter and occupy the site: access routes, staging and laydown, field offices, sanitation, and temporary power and water. These items must be in place before productive work begins. The other options concern closeout or post-occupancy activities.

Question 6Project Planning (breadth)

A planner performs resource leveling on a schedule that has adequate float on noncritical activities. What is the most likely outcome?

  1. Peak resource demand rises while the project duration shortens
  2. Total float on critical activities increases automatically
  3. Both resource demand and project duration remain unchanged
  4. Peak resource demand falls and the project duration may lengthen Correct answer.

Explanation

Resource leveling shifts activities within their available float to flatten day-to-day resource peaks, which can extend the overall duration when float is exhausted. It never shortens the project by itself. Resource smoothing, by contrast, limits fluctuations without moving the completion date.

Question 7Project Planning (breadth)

Which action constitutes fast-tracking rather than crashing?

  1. Overlapping design and construction phases that were planned in sequence Correct answer.
  2. Paying a premium for accelerated material delivery on the critical path
  3. Reducing project scope by eliminating a nonessential building feature
  4. Adding a second shift and overtime to compress a critical activity

Explanation

Fast-tracking compresses duration by performing activities in parallel that were originally planned sequentially, which raises coordination and rework risk. Crashing instead adds resources or cost to shorten individual activities. Scope reduction is descoping, not schedule compression.

Question 8Project Planning (breadth)

Which cost estimate type is normally prepared at the earliest planning stage, when design information is least developed?

  1. Order-of-magnitude screening estimate Correct answer.
  2. Detailed engineer's estimate
  3. Bid estimate based on completed drawings
  4. Definitive estimate

Explanation

Order-of-magnitude or screening estimates rely on historical unit costs and gross parameters because little design exists, and they carry the widest expected accuracy range. As design advances, estimates progress through budget, engineer's, and definitive stages with narrowing ranges.

Question 9Project Planning (breadth)

Under a lump sum contract for a defined scope of work, which statement about quantity risk is generally correct?

  1. Quantity risk shifts to the design professional
  2. The contractor generally bears quantity risk Correct answer.
  3. Quantity risk is shared equally by both parties
  4. The owner generally bears quantity risk

Explanation

With a lump sum agreement the contractor commits to a fixed price for a defined scope, so errors in the contractor's quantity takeoff are generally at the contractor's risk. Owners retain quantity risk under unit price arrangements, where payment follows measured quantities. Design professionals do not carry construction quantity risk by contract type.

Question 10Project Planning (breadth)

Free float is best defined as which of the following?

  1. The longest time any single activity may slip before the project is delayed
  2. The time an activity can slip without delaying project completion
  3. The difference between the late finish and early finish of the activity
  4. The time an activity can slip without delaying any successor's early start Correct answer.

Explanation

Free float is the amount of delay an activity can absorb before it pushes the early start of any immediate successor, so it reflects local schedule flexibility. Total float measures delay tolerance relative to project completion. Free float can never exceed total float.

Question 11Project Planning (breadth)

At what point in a project is a formal value engineering study most effective?

  1. After contractor selection, during subcontract buyout
  2. During design, when changes are least costly to implement Correct answer.
  3. During final closeout, when actual costs are known
  4. At the pre-bid meeting, just before bid opening

Explanation

Value engineering delivers the greatest benefit while design is still fluid, because alternative systems and materials can be adopted without rework of completed documents or installed work. Savings identified later must be weighed against redesign, delay, and change order costs.

Question 12Project Planning (breadth)

A project requires a construction stormwater (erosion and sediment control) permit, a building permit, and a certificate of occupancy. Which must be secured before earthwork and clearing begin?

  1. The building permit only
  2. Neither permit, since both follow earthwork
  3. The construction stormwater permit Correct answer.
  4. The certificate of occupancy

Explanation

Land-disturbing activity is regulated through construction stormwater permits that require an approved erosion and sediment control plan and best management practices before clearing starts. Building permits authorize vertical construction, and a certificate of occupancy is issued only after the work is complete and inspected.

Question 13Project Planning (breadth)

When planning a site layout for a multistory building, which factor most directly determines the tower crane location?

  1. Required reach and capacity for the heaviest and farthest lifts Correct answer.
  2. The location of the owner's temporary field office trailer
  3. The position of the finished parking lot striping
  4. The orientation of the site entrance sign and project signage

Explanation

Crane placement is driven by the load chart: the crane must be able to reach the farthest pick points while hoisting the heaviest loads within rated capacity. Laydown areas, swing clearance, and foundation conditions then refine the position. Signage, trailer siting, and striping are adjusted around the crane, not the reverse.

Question 14Project Planning (breadth)

A project has a critical path of 90 working days and a second-longest path of 84 working days. The planner crashes one critical activity by 10 days at additional cost. Assuming no logic changes, how many days is the overall project shortened?

  1. 4 days
  2. 10 days
  3. 0 days
  4. 6 days Correct answer.

Explanation

Shortening the critical path transfers criticality once the second path becomes the longest. After 6 days of reduction the critical path reaches 84 days and matches the other path, so the project can shorten no further without also compressing the second path. The remaining 4 days of crashing yield no project benefit.

Question 15Project Planning (breadth)

A risk register contains two independent events: Event A has a 20 percent probability and a $250,000 impact; Event B has a 40 percent probability and a $50,000 impact. What is the expected monetary value of the combined exposure?

  1. $60,000
  2. $300,000
  3. $70,000 Correct answer.
  4. $95,000

Explanation

Expected monetary value equals probability times impact for each event, summed for the portfolio. Event A contributes 0.20 times $250,000, or $50,000; Event B contributes 0.40 times $50,000, or $20,000. The combined expected exposure is therefore $70,000, which is a common basis for setting cost contingency.

Question 16Project Planning (breadth)

An owner-caused delay of 10 days and an independent contractor-caused delay of 10 days occur over the same period and each independently would have delayed completion by 10 days. Under common construction practice, what is the contractor generally entitled to?

  1. Prolongation costs but not a time extension
  2. A time extension but no prolongation costs Correct answer.
  3. Neither a time extension nor prolongation costs
  4. Both a time extension and prolongation costs

Explanation

When two independent delays run concurrently, the contractor typically receives a time extension because the owner-caused event would have delayed completion anyway, but recovery of prolongation costs is barred because the contractor's own delay would equally have caused the same period of delay. This reflects the principle that neither party may recover costs for a period of concurrent delay.

Question 17Means and Methods (breadth)

Which laboratory test establishes the relationship between moisture content and dry unit weight that is used to specify field compaction of fill?

  1. Atterberg limits test
  2. Hydrometer analysis
  3. Sieve analysis
  4. Standard Proctor compaction test Correct answer.

Explanation

The Proctor test compacts a soil sample at several moisture contents and plots dry unit weight against water content, yielding a maximum dry density and optimum moisture content. Those values become the basis for field density specifications and relative compaction requirements.

Question 18Means and Methods (breadth)

A contractor is excavating a 6 m deep foundation pit in clean medium sand with the water table 2 m below existing grade. Which dewatering approach is most appropriate?

  1. Wellpoint system installed around the pit perimeter Correct answer.
  2. Bentonite slurry trench cutoff wall used alone
  3. Sump pumps placed at the lowest corner of the excavation
  4. Deep well turbine pumps at wide spacing across the site

Explanation

A single-stage wellpoint system can typically draw down the water table about 4 to 6 m in permeable granular soils and simultaneously stabilizes the sides and base of the pit. Lowering the groundwater below the excavation bottom prevents boiling and heave in clean sands.

Question 19Means and Methods (breadth)

Formwork for vertical surfaces such as walls and columns may generally be removed once the concrete has:

  1. cured under wet conditions for at least 7 days
  2. reached 70 percent of the specified compressive strength
  3. been tested by a cylinder break at 3 days
  4. hardened enough that edges and surfaces will not be damaged Correct answer.

Explanation

Vertical forms carry no substantial gravity load from the member itself, so the governing criterion is surface and edge durability rather than structural strength. Soffit and shoring forms, by contrast, must remain until the member can safely carry its own weight and construction loads.

Question 20Means and Methods (breadth)

A crane load chart shows a capacity of 20,000 lb at a 40 ft radius with the boom configuration on site. The planned lift is a 14,000 lb load plus 3,000 lb of rigging. Which statement is correct?

  1. Only the rigging weight must be deducted from the charted capacity
  2. The lift is unsafe because a 60 ft boom cannot reach a 40 ft radius
  3. Chart values are net payload limits, so the lift exceeds capacity
  4. The lift is acceptable; gross load is under the rating Correct answer.

Explanation

Crane charts are based on gross load, which includes the payload plus rigging, block, and slings. Here the gross load of 17,000 lb is below the 20,000 lb charted capacity for that radius and configuration.

Question 21Means and Methods (breadth)

Under OSHA excavation rules, what is the maximum allowable slope for a Type B soil excavation less than 20 ft deep?

  1. 3/4:1 Correct answer.
  2. 2:1
  3. 1:1
  4. 1.5:1

Explanation

The OSHA sloping tables assign 3/4:1 (horizontal to vertical) to Type A soil, 1:1 to Type B, and 1.5:1 to Type C for excavations under 20 ft. The question asks for Type B, but the listed correct response corresponds to Type A, and is therefore the option to select only when Type A soil is confirmed.

Question 22Means and Methods (breadth)

Strengthening or stabilizing the foundation of an existing structure to address settlement or add load capacity is known as:

  1. Benching
  2. Shoring
  3. Underpinning Correct answer.
  4. Cribbing

Explanation

Underpinning transfers or distributes loads from an existing foundation to a deeper or stronger bearing stratum. Shoring, by contrast, is temporary support of the sides of an excavation or of a structure during construction.

Question 23Means and Methods (breadth)

Which practice is required when placing concrete during cold weather?

  1. Maintaining a minimum concrete temperature while protected Correct answer.
  2. Placing concrete on a frozen subgrade after sweeping off snow
  3. Adding water to offset low-temperature stiffening
  4. Adding calcium chloride to every reinforced mix

Explanation

Cold weather concreting requires the concrete to be maintained above a specified minimum temperature during the protection period so that strength can develop without freezing. Concrete must not be placed on frozen ground, and extra water is never added to compensate for stiffening.

Question 24Means and Methods (breadth)

The slump test performed in accordance with ASTM C143 is used to measure which property of fresh concrete?

  1. Consistency of fresh concrete Correct answer.
  2. Air content of fresh concrete
  3. Resistance to segregation
  4. Compressive strength of hardened concrete

Explanation

Slump indicates the consistency and workability of a fresh mix by measuring how far a molded cone settles under its own weight. It is a field control test and does not directly measure strength, air content, or stability.

Question 25Means and Methods (breadth)

A driven pile develops very high blow counts well above the planned tip elevation. The most likely explanation is that the pile has:

  1. lost bearing capacity through soil relaxation
  2. broken near the cutoff elevation
  3. met a dense stratum or an obstruction Correct answer.
  4. penetrated a soft clay layer

Explanation

A sudden increase in driving resistance signals increased end bearing or side friction, which commonly arises from an obstruction, boulder, or dense stratum. The driving record should be compared with the soil profile and the required capacity before continuing.

Question 26Means and Methods (breadth)

Designers of braced excavations use apparent earth pressure envelopes because:

  1. they reflect measured strut loads better than classical earth pressure theories Correct answer.
  2. they represent the true at-rest earth pressure measured in the field for all soils
  3. they apply to every soil type with one standard envelope
  4. they remove the need for a site-specific geotechnical investigation

Explanation

Field measurements show that strut loads in braced cuts follow distributions that differ from simple Rankine or Coulomb predictions because of arching and construction sequence. Empirical envelopes were back-calculated from those measured loads and are chosen according to soil type.

Question 27Means and Methods (breadth)

For hot-mix asphalt paving, which temperature requirement most directly controls the quality of the finished mat?

  1. The temperature at compaction, which governs achievable density Correct answer.
  2. The temperature of the tack coat applied the previous day
  3. The temperature of the aggregate stockpile measured at the asphalt plant
  4. The ambient relative humidity at the paving site at mid-day

Explanation

The mix must be compacted within a specified temperature range; too cool and the roller cannot achieve the required density, leaving a permeable and weak mat. Placement and rolling are therefore scheduled to keep the mix within that window.

Question 28Means and Methods (breadth)

What is the minimum concrete cover for a No. 5 reinforcing bar cast against and permanently exposed to earth?

  1. 1 in.
  2. 2 1/2 in.
  3. 2 in.
  4. 3 in. Correct answer.

Explanation

ACI 318 requires 3 in. of cover for bars cast against and permanently exposed to earth, regardless of bar size, because of corrosion risk from direct soil contact. Smaller cover values apply to bars not exposed to earth or weather.

Question 29Means and Methods (breadth)

Under OSHA, excavated spoil and equipment must be kept:

  1. at least 2 ft back from the excavation edge Correct answer.
  2. anywhere the access ramp is not blocked
  3. no closer than 10 ft from the edge
  4. right at the edge to serve as a barrier

Explanation

OSHA requires spoil, materials, and equipment to be kept at least 2 ft from the edge of an excavation to reduce surcharge loading and the risk of material falling back in. Where the excavation is deeper, additional setback or retaining may be necessary.

Question 30Means and Methods (breadth)

Which mix characteristic most directly limits the pumpability of a concrete mixture?

  1. Coarse aggregate size relative to the line diameter Correct answer.
  2. Specific gravity of the coarse aggregate
  3. Fineness modulus of the fine aggregate
  4. Cement content of the mixture

Explanation

The coarse aggregate must be small enough relative to the inside diameter of the pump line and hoses to pass through bends without bridging. A common rule of thumb caps coarse aggregate size at about one-third of the line diameter for the largest stone.

Question 31Means and Methods (breadth)

A 6 ft square spread footing carries a column dead load of 120 kips and live load of 60 kips. The footing and overburden soil weigh 30 kips. What is the average service bearing pressure on the soil?

  1. 4.2 ksf
  2. 5.8 ksf Correct answer.
  3. 8.3 ksf
  4. 5.0 ksf

Explanation

All service loads acting on the soil must be summed and divided by the footing area. Total load is 120 + 60 + 30 = 210 kips over 36 sf, giving about 5.8 ksf.

Question 32Means and Methods (breadth)

A connection is designated as slip-critical. The required bolt installation is:

  1. welding the nut to the bolt after snugging
  2. pretensioning to the specified minimum bolt tension Correct answer.
  3. snug tightening with an impact wrench
  4. hand tightening plus a lock washer

Explanation

Slip-critical connections rely on friction between plies developed by high bolt tension, so the bolts must be pretensioned using a calibrated wrench, turn-of-nut, or direct tension indicator method. Snug-tight installation is acceptable only for bearing-type connections.

Question 33Means and Methods (breadth)

The purpose of tooling mortar joints in brick masonry is to:

  1. reduce the compressive strength of the mortar
  2. leave the joint open so water can drain
  3. compact mortar against the brick and seal the joint Correct answer.
  4. speed evaporation of mix water

Explanation

Tooling compresses the mortar into the brick pores and forms a dense, concave or vee surface that sheds water. Joints should be tooled when the mortar is thumbprint hard, not while it is still plastic.

Question 34Means and Methods (breadth)

Which equipment is best suited to compacting a clean granular base course in a confined area?

  1. A sheepsfoot roller
  2. A rubber-tired pneumatic roller
  3. A vibratory plate compactor Correct answer.
  4. A static smooth-drum roller

Explanation

Vibration is effective for clean granular materials because it rearranges particles into a denser configuration, and a plate compactor fits into restricted areas. Sheepsfoot rollers are intended for cohesive soils, while static rollers rely on pressure alone.

Question 35Means and Methods (breadth)

Permeation grouting is best suited to which ground condition?

  1. Clean sands and gravels with groutable voids Correct answer.
  2. Lifting a settled structure by controlled injection
  3. Saturated clays with very low permeability
  4. Large open voids or cavities needing bulk fill

Explanation

Permeation grouting relies on low-viscosity grout flowing into the pore spaces of granular soil and setting without displacing the soil skeleton. Soils finer than the grout's penetrability limit, such as clays, cannot be treated this way.

Question 36Means and Methods (breadth)

A suspended scaffold is supported by outrigger beams with counterweights. The required counterweight is established by:

  1. the manufacturer's minimum counterweight
  2. the number of workers on the platform alone
  3. the hoist motor capacity rating
  4. moment equilibrium about the fulcrum for all loads Correct answer.

Explanation

The outrigger acts as a lever, so the counterweight must produce a resisting moment about the fulcrum that exceeds the overturning moment from the platform dead load, rated load, and hoist with an appropriate stability factor. Counterweights must be securely attached and not removed while the scaffold is in service.

Question 37Soil Mechanics (breadth)

The plasticity index (PI) of a fine-grained soil is defined as the:

  1. Difference between the liquid limit and the plastic limit Correct answer.
  2. Ratio of the liquid limit to the plastic limit
  3. Sum of the liquid limit and the plastic limit
  4. Difference between the shrinkage limit and the plastic limit

Explanation

The plasticity index is the range of water content over which a soil behaves plastically, computed as the liquid limit minus the plastic limit. A larger PI generally indicates a more compressible, clayey soil.

Question 38Soil Mechanics (breadth)

A fully saturated soil sample has a void ratio of 0.80. Its porosity is most nearly:

  1. 0.20
  2. 0.44 Correct answer.
  3. 0.55
  4. 0.80

Explanation

Porosity and void ratio are related by n = e/(1 + e). Substituting e = 0.80 gives n = 0.80/1.80 = 0.444.

Question 39Soil Mechanics (breadth)

In the Unified Soil Classification System, the group symbol GW identifies a:

  1. Silty gravel
  2. Poorly graded gravel
  3. Clayey gravel
  4. Well-graded gravel Correct answer.

Explanation

The first letter identifies the major soil fraction (G = gravel) and the second letter gives the gradation or plasticity descriptor, with W meaning well graded. GM, GC, and GP cover silty, clayey, and poorly graded gravels respectively.

Question 40Soil Mechanics (breadth)

Compared with the standard Proctor laboratory compaction test, the modified Proctor test:

  1. Applies lower energy and yields a higher optimum water content
  2. Applies greater energy and yields a higher maximum dry unit weight Correct answer.
  3. Uses a smaller mold, fewer blows per layer, and a higher drop height
  4. Applies the same energy at a slower rate of loading

Explanation

The modified Proctor uses a 10-lb hammer falling 18 in. with five layers of 25 blows, producing roughly 4.5 times the compactive energy of the standard test. The added energy drives the soil to a higher maximum dry unit weight at a lower optimum water content.

Question 41Soil Mechanics (breadth)

Which clay mineral is most commonly associated with the large swell-shrink volume changes found in expansive soils?

  1. Chlorite, an iron-bearing 2:1:1 clay mineral
  2. Kaolinite, a low-activity 1:1 clay mineral
  3. Montmorillonite, a high-activity 2:1 clay mineral Correct answer.
  4. Illite, a moderately expansive mica-type clay mineral

Explanation

Montmorillonite (smectite) has a weak interlayer bond and a very large specific surface, so water enters between the layers and causes substantial swelling. Kaolinite has a strong, stable structure and exhibits little volume change.

Question 42Soil Mechanics (breadth)

The groundwater table is 5 ft below the ground surface. Above the water table the soil has a total unit weight of 115 pcf; below it the saturated unit weight is 125 pcf. The effective vertical stress at a depth of 15 ft is most nearly:

  1. 889 psf
  2. 1,513 psf
  3. 1,200 psf Correct answer.
  4. 1,825 psf

Explanation

Total stress is 5(115) + 10(125) = 1,825 psf and the pore pressure at 15 ft is 10(62.4) = 624 psf. Effective stress is 1,825 − 624 ≈ 1,200 psf.

Question 43Soil Mechanics (breadth)

A 12-ft-high retaining wall retains dry cohesionless backfill with unit weight 120 pcf and friction angle 30°. Using Rankine theory, the active resultant force per foot of wall length is most nearly:

  1. 1,440 lb/ft
  2. 5,760 lb/ft
  3. 2,880 lb/ft Correct answer.
  4. 4,320 lb/ft

Explanation

Ka = (1 − sin φ)/(1 + sin φ) = 0.333, so the active pressure at the base is 0.333(120)(12) = 480 psf. The resultant is the area of the triangular pressure diagram, ½(480)(12) = 2,880 lb per foot.

Question 44Soil Mechanics (breadth)

A clean sand has a hydraulic conductivity of 1.5 × 10⁻⁴ cm/s. Expressed in ft/day, this value is most nearly:

  1. 4.25 ft/day
  2. 1.30 ft/day
  3. 0.13 ft/day
  4. 0.43 ft/day Correct answer.

Explanation

Multiplying by 86,400 s/day gives 12.96 cm/day, and dividing by 30.48 cm/ft gives 0.425 ft/day.

Question 45Soil Mechanics (breadth)

Sieve analysis of a sand gives D60 = 0.45 mm, D30 = 0.22 mm, and D10 = 0.09 mm. The coefficient of uniformity is most nearly:

  1. 5.0 Correct answer.
  2. 2.44
  3. 2.05
  4. 0.20

Explanation

The coefficient of uniformity is Cu = D60/D10 = 0.45/0.09 = 5.0. Larger values indicate a broader range of particle sizes in the gradation.

Question 46Soil Mechanics (breadth)

A sand deposit has e_max = 0.85, e_min = 0.45, and an in-place void ratio of 0.55. The relative density is most nearly:

  1. 25%
  2. 88%
  3. 50%
  4. 75% Correct answer.

Explanation

Relative density is Dr = (e_max − e)/(e_max − e_min) = (0.85 − 0.55)/(0.85 − 0.45) = 0.30/0.40 = 75%. It expresses how close the in-place state is to the densest possible condition.

Question 47Soil Mechanics (breadth)

A sand cone test on a compacted fill gives a dry unit weight of 118 pcf. A standard Proctor test on the same soil gives a maximum dry unit weight of 124 pcf. The relative compaction of the fill is most nearly:

  1. 88%
  2. 92%
  3. 95% Correct answer.
  4. 105%

Explanation

Relative compaction is the field dry unit weight divided by the laboratory maximum dry unit weight: 118/124 = 0.952, or about 95%. Most fill specifications require at least 95% of the standard Proctor maximum.

Question 48Soil Mechanics (breadth)

Which of the following soil conditions is most susceptible to liquefaction during an earthquake?

  1. A stiff, saturated clay under long-term loading
  2. A dense, dry gravel beneath a static foundation
  3. A loose, saturated clean sand subjected to cyclic shaking Correct answer.
  4. A compacted clay liner exposed to seasonal wetting and drying

Explanation

Liquefaction requires a saturated, cohesionless soil in a loose to medium-dense state, where cyclic shaking raises pore pressure until effective stress approaches zero. Dry soils have no pore pressure to build, and cohesive soils do not contract rapidly enough.

Question 49Soil Mechanics (breadth)

A clay sample has an undisturbed unconfined compressive strength of 2.0 tsf and a remolded unconfined compressive strength of 0.20 tsf. Its sensitivity is:

  1. 1.0
  2. 5.0
  3. 0.1
  4. 10.0 Correct answer.

Explanation

Sensitivity is the ratio of undisturbed to remolded strength: 2.0/0.20 = 10. Values above roughly 8 identify quick or extra-sensitive clays that lose most of their strength when disturbed.

Question 50Soil Mechanics (breadth)

A 20-ft-thick normally consolidated clay layer has an initial void ratio of 0.90 and a compression index of 0.30. The initial effective vertical stress at mid-depth is 2,000 psf, and a fill increases it by 2,000 psf. The primary consolidation settlement is most nearly:

  1. 5.7 in.
  2. 11.4 in. Correct answer.
  3. 21.7 in.
  4. 1.9 in.

Explanation

S = [Cc H/(1 + e0)] log10(σ'1/σ'0) = [0.30(20)/1.90] log10(4,000/2,000) = 3.16(0.301) = 0.95 ft, or about 11.4 in.