Test 26 - Types and Selection of Foundations

Question 1 ప్రశ్న 1

Which statement best distinguishes shallow foundations from deep foundations in terms of their load-transfer mechanisms and engineering selection?

A A shallow foundation must transfer loads entirely through skin friction, whereas a deep foundation transfers loads only through end bearing. B Shallow foundations generally transfer loads to soil relatively close to the ground surface through their bases, while deep foundations can transfer loads to deeper ground through shaft resistance, base resistance or both. C A foundation is automatically classified as deep whenever groundwater occurs above its founding level. D A foundation is classified solely by its construction material, irrespective of embedment and load transfer.

Question 2 ప్రశ్న 2

A single interior column of a lightly loaded building rests above a thick, reasonably uniform deposit of competent soil. Adjacent columns are sufficiently far apart, and calculations indicate acceptable bearing pressure and settlement. Which foundation arrangement is generally most economical to examine first?

A A full-building raft foundation regardless of loading. B A group of long piles terminating in an uninvestigated stratum. C An isolated spread footing centred approximately beneath the column. D A combined footing connecting every column in the building.

Question 3 ప్రశ్న 3

A continuous masonry wall imposes a service vertical load of 540 kN per metre of wall length. Assuming a centrally loaded continuous strip footing and allowable GROSS soil contact pressure of 180 kPa, what minimum footing width is required from the uniform-pressure criterion alone? Neglect any additional foundation self-weight.

A 3.0 m. B 2.0 m. C 2.5 m. D 3.5 m.

Question 4 ప్రశ్న 4

A proposed isolated footing can bear on a dense sand layer near the surface, but investigation reveals a thick compressible clay layer beneath it within the significant stress-influence zone. Which foundation-selection principle is most appropriate?

A Select a shallow footing using only the dense sand's bearing resistance and ignore the clay. B Assume that dense sand completely prevents stress transmission to deeper soil. C Select a raft automatically because all clay deposits prohibit isolated footings. D Assess both bearing resistance and settlement of the layered profile before comparing enlarged shallow footings, a raft, ground improvement or deeper foundations.

Question 5 ప్రశ్న 5

Two adjacent building columns are spaced 2.6 m centre-to-centre. Preliminary bearing calculations suggest individual square footings each requiring a plan dimension of 3.0 m along the line joining the columns. If each footing is centred beneath its column, what is the plan overlap along that line, and which alternative deserves consideration?

A There is a 0.4 m clear gap, so overlapping is not a concern. B The footings overlap by 0.4 m, making a combined footing or another integrated arrangement worth evaluating. C The footings overlap by 2.6 m, so only pile foundations can be used. D The footings remain independent because centre-to-centre spacing never affects footing layout.

Question 6 ప్రశ్న 6

Two vertical column loads of 600 kN and 900 kN act at positions x = 1 m and x = 5 m, respectively, along a proposed combined-footing axis. Neglect footing self-weight and other loads. At what position x, measured from the same origin, does their resultant act?

A 3.0 m. B 3.2 m. C 3.4 m. D 4.0 m.

Question 7 ప్రశ్న 7

A rectangular combined footing extends from x = 0 to x = 8 m along its longitudinal axis and has uniform width. Two vertical column loads act at x = 2 m and x = 6 m, with magnitudes 900 kN and 600 kN, respectively. Neglect all other loads. What is the location of the resultant relative to the rectangular footing's geometrical centre?

A The resultant is 0.4 m to the left of the footing centre. B The resultant coincides exactly with the footing centre. C The resultant is 0.4 m to the right of the footing centre. D The resultant is 1.0 m to the left of the footing centre.

Question 8 ప్రశ్న 8

Two columns with unequal vertical loads require one combined footing, but property-boundary and layout restrictions make it impractical to centre a rectangular footing beneath the load resultant. Which design approach is most appropriate?

A Assume the soil reaction is uniform under any arbitrary rectangular layout regardless of resultant eccentricity. B Ignore the larger column load when proportioning the footing area. C Provide two overlapping isolated footings without any structural connection. D Consider a suitably proportioned trapezoidal combined footing or another arrangement whose contact-pressure and structural behaviour satisfy the design requirements.

Question 9 ప్రశ్న 9

Two columns are to be supported by a rectangular combined footing carrying a total GROSS vertical load of 2400 kN, including the applicable footing and backfill weights. The allowable GROSS contact pressure is 200 kPa. If the preliminary footing width is 3.0 m and the load is assumed centrally applied with uniform pressure, what minimum footing area and length satisfy the pressure requirement?

A Area = 8 m2 and length = 2.67 m. B Area = 10 m2 and length = 3.33 m. C Area = 12 m2 and length = 4.0 m. D Area = 15 m2 and length = 5.0 m.

Question 10 ప్రశ్న 10

An exterior column is close to a property boundary, making it difficult to provide a centrally loaded isolated footing. An interior column is available nearby, and the engineer proposes connecting their separate footings with a strap beam. Which statement describes a conventional strap-footing arrangement correctly?

A The strap beam is assumed to provide all soil bearing pressure along its entire length. B The footings remain structurally independent, and the connecting member transmits no bending moment. C The strap beam is used only to distribute groundwater pressure and does not affect column-load eccentricity. D The strap beam connects the footings structurally and transfers forces and moments, while its own direct soil bearing contribution is normally neglected in the conventional design idealization.

Question 11 ప్రశ్న 11

In an idealized strap-footing system, two downward column loads of 500 kN and 700 kN act at x = 0 and x = 4 m. The upward soil reactions are concentrated at the footing reaction centres x = 0.5 m and x = 4.5 m. Neglect strap self-weight, other loads and external couples. From vertical force and moment equilibrium, what are the reactions at x = 0.5 m and x = 4.5 m, respectively?

A 500 kN and 700 kN. B 650 kN and 550 kN. C 600 kN and 600 kN. D 550 kN and 650 kN.

Question 12 ప్రశ్న 12

A heavily loaded multistorey building has many closely spaced columns, and preliminary individual footings would occupy a substantial portion of the building footprint. The supporting soil is moderately compressible, and differential settlement is a significant concern. Which foundation alternative should be evaluated seriously?

A A raft or mat foundation capable of supporting multiple columns through a connected foundation slab. B A separate isolated footing for every column without considering their interaction. C A strip footing beneath only the outer boundary walls while leaving interior columns unsupported. D A shallow unreinforced pad designed without checking differential settlement.

Question 13 ప్రశ్న 13

A rectangular raft measures 10 m by 12 m and transfers a total GROSS vertical service load of 18000 kN to the soil, including applicable permanent loads. Assuming the load is centrally applied and the average contact pressure is uniform, what is the average gross bearing pressure? The specified allowable gross pressure is 160 kPa.

A 120 kPa; satisfies the stated pressure criterion. B 180 kPa; fails the stated pressure criterion. C 150 kPa; satisfies the stated pressure criterion, subject to other design checks. D 160 kPa; exactly reaches the allowable pressure.

Question 14 ప్రశ్న 14

A rigid raft and a flexible raft of identical plan dimensions carry comparable column loads on the same nonuniform soil deposit. Which statement concerning contact pressure and settlement is most appropriate?

A Contact pressure must be perfectly uniform under both rafts regardless of soil stiffness and column positions. B Both foundations must settle by exactly the same amount at every location because their plan areas are identical. C The flexible raft necessarily carries all loads through friction along its vertical edges. D Raft stiffness, column loading and subgrade variability affect the distribution of contact pressure and differential deformation.

Question 15 ప్రశ్న 15

A buried raft is subjected to an estimated upward hydrostatic resultant of 1500 kN. Its total stabilizing downward permanent load is 1200 kN, and no anchors or other uplift resistance are included in this preliminary comparison. What is the resulting unbalanced vertical force and the appropriate design interpretation?

A 300 kN upward; additional uplift resistance or a revised design must be evaluated. B 300 kN downward; the raft is automatically stable against uplift. C 2700 kN upward; all vertical forces must be added without considering direction. D Zero net force because groundwater uplift cannot affect raft foundations.

Question 16 ప్రశ్న 16

A foundation is proposed on sloping ground with competent rock occurring at different elevations beneath adjacent columns. Which approach is most appropriate before deciding between stepped shallow footings and deep foundations?

A Found all columns at the shallowest possible level without checking rock continuity or slope stability. B Assess rock quality, founding elevations, differential movement, excavation effects and sliding stability before selecting an appropriate stepped or deeper foundation system. C Use identical foundation depths based solely on the highest ground elevation. D Assume that every rock exposure provides the same bearing resistance and stiffness.

Question 17 ప్రశ్న 17

A pile foundation transfers an axial compression load through both its shaft and base. Which statement correctly identifies these two resistance mechanisms?

A Shaft resistance develops only at the pile tip, while end bearing acts along the entire embedded surface. B Both mechanisms depend entirely on structural steel reinforcement rather than surrounding ground conditions. C Shaft resistance develops through interaction along the pile-soil interface, while end bearing acts at the pile base against supporting soil or rock. D End bearing is generated only by groundwater pressure and is independent of the pile-bearing stratum.

Question 18 ప్రశ్న 18

A proposed elevated reservoir rests above a thick deposit of very soft compressible clay. A competent bearing stratum is encountered at greater depth, and calculations indicate that practical isolated footings would experience excessive settlement. Which foundation alternative is most appropriate to investigate?

A Increase column loads so that the soft clay becomes denser immediately. B Use shallow isolated footings without assessing settlement because the groundwater table is high. C Provide an unreinforced raft and assume it will eliminate settlement regardless of clay thickness. D Consider piles or another engineered ground-improvement and foundation solution capable of satisfying bearing and settlement requirements.

Question 19 ప్రశ్న 19

A pile passes through a recently placed fill and a soft clay stratum that may consolidate under additional loading. Which effect should be considered when comparing pile foundations with shallow foundation alternatives?

A All shaft friction along the pile must always act upward and assist in supporting structural load. B Pile settlement is impossible when the tip reaches a dense layer. C Downward movement of surrounding consolidating soil may generate negative skin friction, adding dragload to the pile. D Soil settlement around piles cannot influence axial-force distribution within the piles.

Question 20 ప్రశ్న 20

A preliminary pile-group design contains six identical piles, each assigned an allowable axial compression resistance of 350 kN. For this exercise, group efficiency is specified as 0.80 and allowable group resistance is calculated as eta × n × allowable resistance per pile. If the applied axial service load is 1600 kN, what is the calculated group resistance and preliminary decision?

A 2100 kN; passes because group efficiency must be ignored. B 1680 kN; passes the stated axial-resistance check, subject to other group and settlement checks. C 1680 kN; fails because the applied load exceeds 1680 kN. D 1400 kN; fails the stated axial-resistance check.

Question 21 ప్రశ్న 21

A foundation investigation identifies a thick, reasonably uniform deposit in which no distinct strong end-bearing layer is available within the practical pile length. Adequate shaft resistance can nevertheless be developed along embedded pile surfaces. Which interpretation is most appropriate?

A Friction or floating piles may be considered, with their resistance and settlement verified using the relevant soil-pile interaction model. B Pile foundations cannot be used unless every pile tip rests directly on hard rock. C An isolated footing and a friction pile must always carry identical working loads at identical settlements. D Pile shaft resistance is impossible unless the soil is completely dry.

Question 22 ప్రశ్న 22

A low-rise pumping-station building is proposed on expansive clay exhibiting seasonal swelling and shrinkage. Which foundation-selection approach is most technically defensible?

A Use a shallow footing entirely within the active moisture-change zone without considering uplift or differential movement. B Assume that greater concrete strength alone prevents movements caused by expansive ground. C Use the same foundation depth as a nearby building without investigating moisture variation or soil behaviour. D Investigate the active zone and consider suitable deep or under-reamed pile solutions, moisture-control measures or other engineered alternatives based on the structural and geotechnical requirements.

Question 23 ప్రశ్న 23

A heavily loaded building is planned immediately beside an old vibration-sensitive structure in a congested urban area. Piles are considered necessary based on the ground investigation. Which construction-related selection is most appropriate?

A Select driven displacement piles without assessing vibration or movement effects on the neighbouring structure. B Assume all piling methods produce identical noise, vibration and groundwater impacts. C Compare bored cast-in-situ and other suitable piling methods while evaluating vibration, noise, ground movement, borehole stability, spoil handling and groundwater control. D Avoid any assessment of adjacent foundations because the new pile loads act below ground.

Question 24 ప్రశ్న 24

A water-supply pipeline crossing requires a support foundation within an area exposed to possible riverbed scour and seasonal groundwater variation. Which principle should govern selection between shallow footings and deeper pile foundations?

A A shallow footing is always satisfactory if its average pressure is less than the allowable bearing pressure before scour. B The foundation system should be evaluated for anticipated scour depth, loss of soil support, lateral loads, groundwater effects and remaining bearing and stability conditions. C Pile foundations are automatically unaffected by scour regardless of exposed length or lateral loading. D Groundwater conditions are irrelevant once the proposed foundation is made of reinforced concrete.

Question 25 ప్రశ్న 25

A proposed elevated water-storage structure imposes substantial concentrated vertical loads together with horizontal forces and overturning moments. Site investigation identifies variable near-surface soils and a stronger stratum at greater depth. Which foundation-selection procedure is most appropriate?

A Choose the footing type solely from the largest column load without considering overturning or ground variability. B Use the smallest possible footing area because a higher contact pressure always improves foundation stability. C Select piles automatically without checking group response, lateral resistance or construction feasibility. D Compare viable raft, combined-footing, pile or other systems by evaluating load combinations, bearing resistance, settlement, overturning, lateral behaviour and constructability.

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