Test 28 - Load Capacity of Individual Piles

Question 1 ప్రశ్న 1

A circular pile carries axial compression in a soil profile where both positive shaft resistance and toe resistance can develop. Which expression correctly represents the idealized ultimate geotechnical resistance of the individual pile?

A Qu = Qb - Qs, where both resistances are positive. B Qu = Qb + Qs, subject to the adopted mobilization assumptions. C Qu = Qb/Qs, irrespective of units. D Qu = Qs alone whenever the pile passes through sand.

Question 2 ప్రశ్న 2

In the alpha-method for estimating the ultimate positive shaft resistance of a pile embedded in saturated clay under undrained loading, what does the adhesion factor alpha represent?

A A factor multiplied by the pile elastic modulus to obtain toe stress. B The ratio of pile diameter to its embedded length. C A factor used exclusively to obtain groundwater uplift. D A coefficient relating unit shaft adhesion to undrained shear strength, so that fs = alpha cu.

Question 3 ప్రశ్న 3

A circular pile of diameter 0.60 m is embedded 10 m in uniform saturated clay. For this idealized undrained calculation, use cu = 50 kPa along the shaft and at the toe, alpha = 0.60, Nc = 9, and Qu = (pi d²/4)Nc cu + pi d L alpha cu. If factor of safety = 2.5 and pi = 3.1416, what is the allowable axial compression resistance?

A 346.4 kN. B 692.7 kN. C 277.1 kN. D 225.0 kN.

Question 4 ప్రశ్న 4

A circular pile of diameter 0.40 m passes through 4 m of clay having cu = 40 kPa and alpha = 0.80, followed by 6 m of clay having cu = 70 kPa and alpha = 0.50. The undrained toe strength is 70 kPa, and Nc = 9. Using Qu = (pi d²/4)Nc cu,toe + pi d sum(alpha_i cu,i Li), with pi = 3.1416, what is the ultimate axial resistance?

A 503.9 kN. B 424.7 kN. C 583.1 kN. D 629.7 kN.

Question 5 ప్రశ్న 5

An individual pile has a toe area of 0.20 m² in saturated clay with undrained toe strength cu = 90 kPa. If the specified undrained toe bearing factor Nc = 9, what is its idealized ultimate toe resistance Qb = Ap Nc cu?

A 18 kN. B 90 kN. C 162 kN. D 810 kN.

Question 6 ప్రశ్న 6

An instrumented pile in uniform clay has an ultimate positive shaft resistance of 360 kN over a contributing shaft area of 12 m². The representative undrained strength is cu = 50 kPa. Under the uniform alpha-method relation Qs = alpha cu As, what is the inferred adhesion factor?

A 0.30. B 0.60. C 1.20. D 1.50.

Question 7 ప్రశ్న 7

A designer applies the alpha-method to piles in two clays with different undrained strengths. Which statement about predicting shaft resistance is technically correct?

A The adhesion factor may vary with clay consistency and pile installation, so it should not automatically be held constant solely because cu is known. B The adhesion factor must equal the effective-stress earth-pressure coefficient K for every clay. C Unit shaft resistance is independent of clay strength under undrained conditions. D A pile in clay can develop only toe resistance and no shaft resistance.

Question 8 ప్రశ్న 8

A cylindrical pile with diameter d = 0.50 m mobilizes shaft friction along 10 m of sand. Using the prescribed effective-stress expression Qs = pi d L K sigma_v,avg tan(delta), take K = 1.20, average vertical effective stress = 100 kPa, and tan(delta) = 0.50. What is the ultimate positive shaft resistance? Use pi = 3.1416.

A 471.2 kN. B 754.0 kN. C 1200.0 kN. D 942.5 kN.

Question 9 ప్రశ్న 9

A 0.50 m diameter pile has two 5 m shaft segments in sand. In both layers K = 1.0 and tan(delta) = 0.50, but average vertical effective stresses are 50 kPa and 150 kPa, respectively. Using Qs = pi d sum(Li Ki sigma_v,i tan(delta_i)) and pi = 3.1416, calculate total ultimate shaft resistance.

A 392.7 kN. B 785.4 kN. C 1178.1 kN. D 1570.8 kN.

Question 10 ప్రశ్న 10

A circular pile with diameter D = 0.60 m is founded in sand. For the specified static toe-resistance expression Qb = Ap[0.5 D gamma_eff Ngamma + sigma_v,toe Nq], take gamma_eff = 10 kN/m³, Ngamma = 20, sigma_v,toe = 150 kPa and Nq = 25. Using pi = 3.1416, what is the ultimate toe resistance?

A 1077.3 kN. B 942.5 kN. C 750.0 kN. D 3810.0 kN.

Question 11 ప్రశ్న 11

A 0.50 m diameter pile penetrates 8 m into sand. Use Qb = (pi d²/4)[0.5 d gamma_eff Ngamma + sigma_v,toe Nq] and Qs = pi d L K sigma_v,avg tan(delta). Take gamma_eff = 10 kN/m³, Ngamma = 15, sigma_v,toe = 120 kPa, Nq = 20, K = 1.0, sigma_v,avg = 70 kPa, tan(delta) = 0.50, and factor of safety = 2.5. What are the ultimate and allowable compression resistances, respectively?

A 478.6 kN and 191.4 kN. B 439.8 kN and 175.9 kN. C 918.4 kN and 367.4 kN. D 918.4 kN and 918.4 kN.

Question 12 ప్రశ్న 12

At a pile site the water table is 3 m below ground level. The upper 3 m of sand has bulk unit weight 18 kN/m³, and the next 5 m has saturated unit weight 20 kN/m³; take gamma_w = 10 kN/m³ and hydrostatic conditions. What is the vertical effective overburden stress at 8 m depth?

A 104 kPa. B 154 kPa. C 100 kPa. D 54 kPa.

Question 13 ప్రశ్న 13

The water table rises around a pile in sand while the relevant total overburden and interface parameters remain otherwise comparable. Which statement about the effective-stress method is most defensible?

A Shaft resistance must increase because pore pressure contributes directly to effective normal stress. B The interface friction angle becomes zero as soon as water reaches the pile. C Rising pore pressure can reduce effective normal stress and hence the shaft and toe resistance predicted from effective-stress relationships. D The shaft resistance remains strictly unchanged for every sand and pile type.

Question 14 ప్రశ్న 14

In a simplified sand-pile calculation, the adopted method explicitly caps the effective overburden pressure used in its unit shaft-friction formula once a specified critical depth is reached. Which procedure is correct below that depth?

A Continue increasing the specified effective overburden linearly without limit, regardless of the stated cap. B Use the stipulated limiting effective overburden in the capped calculation, while recognizing that the critical-depth assumption is model-specific. C Set all shaft resistance below the critical depth to zero. D Replace shaft resistance automatically by Nc cu without checking whether the soil is clay.

Question 15 ప్రశ్న 15

A circular pile has a diameter of 0.80 m and a specified ultimate unit toe resistance of 1500 kPa. Assuming uniform toe pressure and pi = 3.1416, what ultimate end-bearing resistance does the pile develop?

A 471.2 kN. B 942.5 kN. C 1200.0 kN. D 754.0 kN.

Question 16 ప్రశ్న 16

A cylindrical pile has diameter 0.60 m, a 12 m contributing shaft length and uniform ultimate positive unit shaft resistance of 45 kPa. Neglect toe resistance and use an explicit factor of safety of 3.0. What allowable axial compression resistance is obtained using Qs = pi d L fs?

A 1017.9 kN. B 339.3 kN. C 565.5 kN. D 254.5 kN.

Question 17 ప్రశ్న 17

A pile has calculated ultimate geotechnical compression resistance of 1400 kN, for which the project specifies a factor of safety of 2.5. The separately assessed allowable structural resistance is 500 kN, and the serviceability analysis limits working load to 450 kN. What is the governing allowable working compression load?

A 450 kN. B 500 kN. C 560 kN. D 1400 kN.

Question 18 ప్రశ్న 18

For two geometrically similar circular piles in the same idealized soil, assume identical mobilized average unit shaft friction, identical embedded length and identical unit toe resistance. If pile diameter doubles, how do ultimate shaft and toe resistances change?

A Shaft resistance quadruples and toe resistance doubles. B Both resistances double. C Both resistances quadruple. D Shaft resistance doubles and toe resistance quadruples.

Question 19 ప్రశ్న 19

At a point near the neutral plane of a pile affected by downward-moving fill and consolidating clay, the compressive axial force transmitted from the superstructure is 700 kN, and the accumulated downward dragload above that point is 160 kN. Neglect other forces. What axial compressive force must be carried at that location?

A 540 kN. B 700 kN. C 860 kN. D 1120 kN.

Question 20 ప్రశ్న 20

A 0.50 m diameter pile has 6 m of contributing shaft in sand. Use the beta-method fs = beta sigma_v,avg, where beta = K tan(delta). Given K = 0.80, tan(delta) = 0.50, and average vertical effective stress = 150 kPa, calculate ultimate shaft resistance for the segment, using pi = 3.1416.

A 282.7 kN. B 565.5 kN. C 754.0 kN. D 942.5 kN.

Question 21 ప్రశ్న 21

In the effective-stress shaft-friction method for piles in sand, which interpretation of K and delta is correct?

A K reflects an applicable horizontal-to-vertical effective-stress relationship at the interface, while delta represents pile-soil interface friction and need not universally equal the soil friction angle phi. B K is the undrained clay adhesion factor, and delta is the compression index of clay. C K and delta always take the same numerical value regardless of construction method. D The method does not require effective stress because groundwater has no influence on sand shaft resistance.

Question 22 ప్రశ్న 22

A pile passes through thick clay and its toe rests in a dense sand layer. Which approach to evaluating its axial compression resistance is technically most appropriate?

A Use the sand friction angle to calculate undrained adhesion along the entire clay shaft. B Evaluate the clay shaft contribution using appropriate clay parameters and the sand toe contribution using suitable sand bearing parameters, with other relevant strata assessed separately. C Use only the cohesion of the clay at the ground surface for both shaft and toe. D Ignore the dense sand because the pile has previously passed through clay.

Question 23 ప్రశ్న 23

For bored cast-in-situ concrete piles whose ultimate geotechnical capacity is estimated by a static formula under IS 2911 (Part 1/Sec 2):2010, what is the specified minimum factor of safety for arriving at the safe capacity?

A 1.5. B 2.0. C 3.5. D 2.5.

Question 24 ప్రశ్న 24

Static pile-capacity calculations predict that an individual pile has sufficient ultimate resistance, but a project requires confirmation of actual load-settlement response. Which investigation provides the most directly relevant performance evidence?

A A low-strain integrity test alone, because it directly determines safe axial load. B An SPT blow count from an unrelated soil horizon without any other analysis. C A properly specified axial compression pile-load test with measured load and pile-head movement, interpreted under the applicable testing criteria. D A concrete slump test, because fresh-concrete workability uniquely determines geotechnical capacity.

Question 25 ప్రశ్న 25

A 0.50 m diameter pile has 5 m of shaft in clay with cu = 40 kPa and alpha = 0.80, followed by 5 m of shaft in sand with K = 1.0, tan(delta) = 0.50 and average vertical effective stress 110 kPa. Its toe is in sand with sigma_v,toe = 200 kPa, gamma_eff = 10 kN/m³, Nq = 20 and Ngamma = 20. Using Qs,clay = pi d L alpha cu, Qs,sand = pi d L K sigma_v,avg tan(delta), Qb = (pi d²/4)[0.5 d gamma_eff Ngamma + sigma_v,toe Nq], a factor of safety of 2.5, and pi = 3.1416, what is the allowable axial compression resistance?

A 591.4 kN. B 431.0 kN. C 795.2 kN. D 1478.5 kN.

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