Test 27 - Pile Foundations and Classification

Question 1 ప్రశ్న 1

A proposed elevated water-service structure rests on thick soft clay, and investigation finds a stronger stratum at a greater depth. Shallow footing calculations fail the specified settlement criterion. What is the principal geotechnical reason for considering piles?

A Piles always eliminate settlement regardless of length and group arrangement. B Piles make subsurface investigation unnecessary once a hard stratum is suspected. C Piles can transfer loads into deeper ground through shaft or base resistance and may provide an alternative where shallow foundations perform inadequately. D Piles increase the allowable contact pressure of the topsoil without transferring force to deeper material.

Question 2 ప్రశ్న 2

A pile extends through weak deposits and terminates on competent rock, with most of its design compression resistance mobilized beneath its toe. Which functional classification best describes the pile?

A Predominantly end-bearing pile. B Compaction pile installed solely to improve adjacent loose sand. C Tension pile designed only for upward load. D Friction pile supported exclusively by upward shaft resistance.

Question 3 ప్రశ్న 3

A long pile is installed in a thick deposit with no distinct strong bearing layer near its toe. Its principal axial compression resistance is developed along the pile-soil interface. What is its most appropriate functional classification?

A Pure end-bearing pile. B Sheet pile used only for earth retention. C Compaction pile that does not carry a structural load. D Friction or floating pile.

Question 4 ప్రశ్న 4

For a compression pile, the geotechnical resistance calculation includes both mobilized shaft resistance and toe resistance. Which equation correctly represents their additive ULTIMATE axial compression resistance under the stated simplified model?

A Qu = Qs - Qb, with both terms treated as positive resistances. B Qu = Qs + Qb, where Qs is shaft resistance and Qb is base resistance. C Qu = Qs/Qb, independent of the units used. D Qu = Qb only, because a pile cannot mobilize shaft and base resistance together.

Question 5 ప్రశ్న 5

A pile is assigned a calculated ultimate shaft resistance Qs = 650 kN and ultimate base resistance Qb = 450 kN. In this exercise, assume that the two ultimate components may be added and that a factor of safety of 2.0 is applied to their sum. What are the total ultimate and allowable axial compression resistances?

A 1100 kN and 1100 kN. B 450 kN and 225 kN. C 1100 kN and 550 kN. D 1300 kN and 650 kN.

Question 6 ప్రశ్న 6

At a specified ultimate compression state, a pile mobilizes 700 kN through shaft resistance and 300 kN through toe resistance. What percentage of the combined ultimate resistance is supplied by shaft resistance?

A 30%. B 50%. C 100%. D 70%.

Question 7 ప్రశ్న 7

A lightly loaded underground tank may be subjected to groundwater uplift exceeding its stabilizing dead weight. Which pile function is directly relevant when piles are connected to the tank foundation to resist the remaining upward load?

A Tension or uplift resistance developed primarily through soil-pile interface action together with other justified uplift-resisting components. B End-bearing compression resistance alone, assumed to act upward automatically at the toe. C Ground densification only, with no force connection to the tank. D A rigid pile cap that creates uplift resistance without transferring forces to ground.

Question 8 ప్రశ్న 8

A preliminary uplift pile group contains six piles, each having an ALLOWABLE individual uplift resistance of 180 kN. For this exercise, the allowable group resistance is specified as group efficiency 0.80 times the sum of individual allowable values. A net uplift service load of 840 kN acts on the group, and pile self-weight is already included in the given resistances. Which conclusion follows from the stated calculation?

A Calculated resistance = 1080 kN, so group efficiency can be neglected. B Calculated resistance = 864 kN; the specified group-resistance check passes, subject to other checks. C Calculated resistance = 720 kN; the check fails. D Calculated resistance = 864 kN; the check fails because 840 kN is greater than 864 kN.

Question 9 ప్రశ్న 9

A ground-improvement contractor installs displacement-type granular compaction piles in loose sand mainly to densify the surrounding soil rather than to carry isolated column loads as conventional structural piles. What is the primary intended function?

A Develop compression resistance exclusively through a rock socket at the toe. B Anchor a foundation against uplift by tensile steel reinforcement alone. C Increase the density and engineering performance of the surrounding granular soil through an appropriate compaction process. D Provide a continuous impermeable barrier against groundwater flow.

Question 10 ప్రశ్న 10

A bridge pier foundation must resist a substantial horizontal load as well as vertical load. Which statement best explains the use of batter or raker piles in an appropriate pile-group arrangement?

A Batter piles can resist only groundwater uplift and have no relevance to horizontal forces. B Batter piles eliminate all bending moments from a pile cap regardless of their geometry. C Batter piles are necessarily unsuitable whenever vertical gravity loads are present. D Inclined piles can mobilize axial forces having horizontal components, helping resist lateral actions where their use and connections are appropriate.

Question 11 ప్రశ్న 11

An inclined pile carries an axial compression force of 250 kN and is oriented at 30 degrees TO THE VERTICAL. Using cos 30 degrees = 0.866 and sin 30 degrees = 0.500, what are the magnitudes of its vertical and horizontal force components, respectively?

A 216.5 kN and 125.0 kN. B 125.0 kN and 216.5 kN. C 250.0 kN and 0 kN. D 176.8 kN and 176.8 kN.

Question 12 ప్రశ్న 12

An elevated transmission structure has load combinations involving both compression and uplift at different foundation supports. Which classification and design approach is most appropriate?

A Select end-bearing piles alone because every pile develops identical tension and compression capacities. B Identify compression, tension and lateral demands separately and select piles and connections designed for their governing load combinations. C Provide compaction piles without connections to the structure, since soil densification alone transfers every uplift load. D Assume upward and downward axial forces cancel at each pile irrespective of the load combination.

Question 13 ప్రశ్న 13

A reinforced-concrete pile is cast and cured before installation, then driven into the ground by a suitable hammer. Which installation classification describes it most accurately?

A Bored cast-in-situ concrete pile. B Driven cast-in-situ pile formed by placing fresh concrete in a driven casing. C Driven precast concrete pile. D Precast concrete pile installed in a prebored hole.

Question 14 ప్రశ్న 14

A steel casing or tube is driven to the required depth, concrete is placed within it, and the casing may be retained or withdrawn according to the selected system. Which pile method is being described?

A Driven cast-in-situ concrete piling. B Driven precast concrete piling using an already hardened concrete member. C Bored cast-in-situ piling with no driven hole-forming element. D Installation of a timber pile by water jetting alone.

Question 15 ప్రశ్న 15

A deep foundation is installed by drilling a borehole, providing temporary casing or support fluid where required, lowering reinforcement and placing concrete in the excavation. What is its most suitable classification?

A Driven steel H-pile. B Compaction pile installed only to densify the surrounding deposit. C Precast pile driven after hardening. D Bored cast-in-situ concrete pile.

Question 16 ప్రశ్న 16

A bored cast-in-situ pile extends below the groundwater table in unstable granular soil, and the borehole is maintained with a suitable support fluid. Which concreting method is appropriate to avoid uncontrolled segregation and mixing with water or slurry?

A Drop dry concrete freely from the surface through the full fluid-filled depth. B Use a properly operated tremie pipe so concrete is placed from below and the discharge remains embedded in fresh concrete as the pour rises. C Pump groundwater continuously into the fresh concrete to increase slump. D Withdraw the reinforcement cage and leave the borehole open until natural drainage occurs.

Question 17 ప్రశ్న 17

A lightly loaded structure is proposed on expansive clay subject to seasonal shrinking and swelling. Which pile arrangement is specifically associated with enlarged bulbs formed below the ground surface and can be considered where investigation and design justify it?

A Straight timber piles intended only for short temporary construction. B Sheet piles used primarily to retain excavated soil. C Under-reamed piles, with enlarged bases or bulbs and appropriate embedment relative to the active zone. D Ordinary surface strip footings whose width is reduced to prevent swelling.

Question 18 ప్రశ్న 18

For a steel H-pile selected because it can be driven through difficult deposits and spliced to reach the required length, which design concern remains important?

A Steel piles cannot carry end-bearing resistance because their cross-section is open. B Steel H-piles are always immune to corrosion when partly above the water table. C Steel piles require no structural capacity check once a geotechnical pile capacity is obtained. D Potential corrosion and section loss, driving stresses, splice performance and relevant structural resistance must be evaluated.

Question 19 ప్రశ్న 19

Why might prestressed precast concrete piles be selected instead of ordinary reinforced precast concrete piles for a demanding driven-pile application?

A Prestressing can improve cracking resistance during handling and driving and can be beneficial under specified service actions, subject to suitable design. B Prestressing eliminates the need to assess pile-soil shaft resistance. C Prestressed piles need no consideration of tension, bending or driving impact. D Prestressing converts every pile automatically into a compaction pile.

Question 20 ప్రశ్న 20

Which statement is most appropriate when selecting timber piles for a site with a fluctuating groundwater table?

A Timber strength is completely independent of biological exposure and moisture changes. B Durability must be assessed carefully because timber in susceptible zones of variable moisture and aeration may deteriorate unless suitably protected. C Timber piles cannot resist compressive loads under any circumstance. D Timber piles are always preferred over concrete and steel for heavily loaded high-rise buildings.

Question 21 ప్రశ్న 21

A dense urban site contains vibration-sensitive buildings, while a separate undeveloped granular-soil site is being considered for pile installation. Which comparison of installation effects is most appropriate?

A Driven piles and bored piles always generate identical vibration and ground displacement. B Driven piles can never alter the density or excess pore pressure of surrounding soil. C Bored piles always improve granular soil by densifying it through large radial displacement. D Impact driving may create noise, vibration and displacement, whereas suitable bored methods often reduce these effects but introduce excavation and borehole-stability risks.

Question 22 ప్రశ్న 22

An idealized cylindrical friction pile has diameter 0.40 m and a 10 m long shaft segment with uniform ultimate unit shaft resistance of 50 kPa. Neglect end bearing and other segments. Using Qs = pi d L tau and pi = 3.1416, calculate the ultimate resistance mobilized along this shaft segment.

A 314.2 kN. B 500.0 kN. C 628.3 kN. D 1256.6 kN.

Question 23 ప్రశ్న 23

Piles support a tank structure while new fill and underlying soft clay consolidate downward relative to the pile shafts. Which geotechnical action must be considered in the pile axial-force and settlement analysis?

A The soil always creates an upward shaft force that reduces pile axial load. B The pile automatically loses all toe resistance once settlement starts. C The only possible consequence is an increase in concrete strength. D Negative skin friction may impose downward dragload along part of the shaft as the surrounding soil settles relative to the pile.

Question 24 ప్రశ్న 24

For concrete pile foundations under Indian practice, which mapping of IS 2911 provisions is correct?

A Part 1, Section 2 covers bored cast-in-situ concrete piles, while Part 4 addresses pile load testing. B Part 1, Section 2 covers driven precast concrete piles, while Part 4 governs bored-pile excavation support. C Part 1, Section 2 covers under-reamed concrete piles, while Part 4 governs pile shaft reinforcement detailing. D Part 1, Section 2 covers driven cast-in-situ concrete piles, while Part 4 specifies pile spacing and group layout.

Question 25 ప్రశ్న 25

A pile foundation is required beside an operating water-treatment plant containing vibration-sensitive equipment. The site has high groundwater, variable strata and restricted access. Which selection strategy is most defensible?

A Choose impact-driven piles automatically because installation effects never influence nearby equipment. B Select the cheapest material without examining load-transfer mechanism or borehole stability. C Specify bored piles without any plan for groundwater, spoil disposal or concrete placement. D Compare viable pile systems using load capacity, settlement, installation vibration, borehole stability, groundwater control, access and quality-assurance requirements.

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