Please keep at least one language enabled. || కనీసం ఒక భాషను ఎంచుకోండి.
Question 1
ప్రశ్న 1
According to Bligh's creep theory, how is seepage beneath an impervious hydraulic structure idealized?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh idealized seepage as following the contact between the impervious structure and the pervious foundation. The total distance travelled along this bottom contour is called the creep length. Horizontal floor portions and the faces of vertical cutoffs are therefore included in that length. This is a simplifying conceptual model rather than the actual curved streamline pattern in the soil. The simplification is one of the major limitations that led to later seepage theories.
వివరణ:
Question 2
ప్రశ్న 2
Which assumption about head loss is fundamental to Bligh's creep theory?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh assumed that seepage head is lost uniformly in proportion to creep distance. Consequently, a straight hydraulic-gradient line can be constructed along the idealized creep path. The average loss of head per unit creep length is H/L. Residual uplift head at an intermediate point is then estimated from the remaining proportion of the creep path. Actual seepage pressure variation is not generally linear, so this assumption limits the accuracy of the theory.
వివరణ:
Question 3
ప్రశ్న 3
How does Bligh's original theory treat horizontal and vertical portions of the seepage path?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh made no distinction between a metre of horizontal creep and a metre of vertical creep. Both are added directly when computing the total creep length. Thus the two faces of a vertical cutoff of depth d contribute approximately 2d to the creep path. Later investigations showed that vertical creep is more effective than horizontal creep in controlling seepage. The equal-weight assumption is therefore a well-known limitation of Bligh's method.
వివరణ:
Question 4
ప్రశ్న 4
A horizontal impervious floor has horizontal length b and three vertical cutoffs of depths d1, d2 and d3. Under Bligh's conceptual treatment, what is the total creep length?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The horizontal part contributes its full length b to the creep path. For a thin vertical cutoff, seepage is idealized as travelling down one face and up the other face. Each cutoff of depth d therefore contributes approximately 2d. Adding the three cutoff contributions gives L = b + 2(d1 + d2 + d3). This expression follows directly from Bligh's equal-weight treatment of horizontal and vertical creep.
వివరణ:
Question 5
ప్రశ్న 5
A Bligh creep profile has 36 m of horizontal floor and vertical cutoffs 4 m, 6 m and 3 m deep. What total creep length is obtained?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh's creep length is the horizontal floor length plus twice the sum of the cutoff depths. Here the cutoff contribution is 2(4 + 6 + 3) = 26 m. Adding the 36 m horizontal floor gives 62 m. The calculation assumes that every horizontal and vertical metre is equally effective. Therefore the total Bligh creep length is 62 m.
వివరణ:
Question 6
ప్రశ్న 6
If the total seepage head causing flow is H and the Bligh creep length is L, what average hydraulic gradient does the theory use?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh defines the average hydraulic gradient as the total head loss divided by total creep length. The corresponding expression is i = H/L. Because the theory assumes linear loss of head, the same average loss per unit creep length is applied throughout the idealized path. Increasing L for the same H therefore decreases the calculated average gradient. The method does not accurately represent the concentrated exit gradient that occurs near the downstream end.
వివరణ:
Question 7
ప్రశ్న 7
According to Bligh's piping criterion, how is the required creep length related to seepage head H and the soil-dependent creep coefficient C?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh expressed the required creep length for piping safety as L = C H at the limiting design condition. In practical interpretation, the provided creep length should be at least this required value. The corresponding average hydraulic gradient is approximately 1/C at the limiting condition. A larger C represents a soil requiring a longer seepage path for the same head. The coefficient is empirical and was obtained from experience rather than a fundamental soil-seepage derivation.
వివరణ:
Question 8
ప్రశ్న 8
For fine micaceous sand, take Bligh's creep coefficient C = 15. If the maximum seepage head is 4.8 m, what minimum creep length follows from L = C H?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Bligh design relation is L = C H. Substituting C = 15 and H = 4.8 m gives L = 15 × 4.8. The result is 72 m. This is the limiting creep length under the assumptions of Bligh's theory. A modern design of an important structure would require a more rigorous seepage and exit-gradient assessment.
వివరణ:
Question 9
ప్రశ్న 9
A structure has a creep length of 72 m and a seepage head of 5.0 m. For coarse-grained sand take C = 12. What does Bligh's average-gradient criterion indicate?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The calculated average gradient is H/L = 5/72, which is approximately 1/14.4. For C = 12, the limiting Bligh gradient is about 1/12. Since 1/14.4 is smaller than 1/12, the provided path satisfies this simplified average-gradient criterion. Equivalently, the required creep length is C H = 60 m, which is less than the provided 72 m. This conclusion is only a Bligh-theory check and does not establish modern exit-gradient safety.
వివరణ:
Question 10
ప్రశ్న 10
What does a larger value of Bligh's creep coefficient C imply for a given seepage head?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh's limiting relation is L = C H. For a fixed seepage head, increasing C directly increases the required creep length. The corresponding limiting average hydraulic gradient is approximately 1/C. A larger C therefore means a smaller permissible average gradient under the theory. This is why relatively erodible fine sands are assigned larger creep coefficients than more resistant coarse mixtures.
వివరణ:
Question 11
ప్రశ్న 11
Under Bligh's theory, what creep-length contribution is assigned to a thin vertical cutoff of depth d that seepage passes down and then up?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The idealized seepage path travels down one face of the cutoff and up the other. Each face contributes approximately the cutoff depth d. The two faces therefore contribute a total length of about 2d. Bligh gives this vertical path the same weight per metre as a horizontal floor length. Later methods showed that this equal treatment does not represent the real seepage field accurately.
వివరణ:
Question 12
ప్రశ్న 12
A Bligh design requires a total creep length of 72 m. If two vertical cutoffs of depths 4 m and 6 m are provided, what horizontal floor length is required under the idealized relation L = b + 2(d1 + d2)?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The two cutoffs contribute 2(4 + 6) = 20 m of Bligh creep length. The remaining creep length must be supplied by the horizontal floor. Hence b = 72 - 20 = 52 m. This calculation treats horizontal and vertical creep as equally effective, exactly as Bligh assumed. A Khosla-based design would not obtain floor and cutoff effectiveness through this simple arithmetic alone.
వివరణ:
Question 13
ప్రశ్న 13
Under Bligh's linear head-loss assumption, what expression gives the residual seepage head after a creep distance x from the upstream entry, when total head loss is H and total creep length is L?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh assumes that the head lost after a creep distance x is Hx/L. The remaining or residual seepage head is therefore H - Hx/L. Factoring H gives h_r = H(1 - x/L). This residual head is used to estimate the hydraulic-grade-line elevation and uplift pressure at the location. The expression follows from the assumed linear loss and is not a general potential-flow solution.
వివరణ:
Question 14
ప్రశ్న 14
The total seepage head is 6 m and the Bligh creep length is 80 m. What residual seepage head remains after 30 m of creep from the upstream entry?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The fraction of total creep already traversed is 30/80 = 0.375. Under Bligh's linear assumption, the same fraction of the total head has been lost. The residual head is therefore 6(1 - 30/80). This equals 3.75 m. The value represents the Bligh estimate of residual seepage head at that creep location.
వివరణ:
Question 15
ప్రశ్న 15
In Bligh's treatment, what does the ordinate of the subsoil hydraulic-gradient line above the floor represent?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The subsoil hydraulic-grade line represents the piezometric level of the seepage water. Its vertical distance above the relevant floor level is related to the residual water head. That residual head creates an upward hydrostatic pressure on the impervious floor. The floor must have adequate weight and structural capacity to resist the resulting net uplift. Bligh obtains this pressure distribution from his assumed linear loss of head along the creep path.
వివరణ:
Question 16
ప్రశ్న 16
If the residual uplift head at a point beneath a floor is 3.75 m of water, what uplift pressure intensity corresponds to it when the unit weight of water is 9.81 kN/m³?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Hydrostatic pressure intensity equals unit weight of water multiplied by the pressure head. Therefore u = 9.81 × 3.75 kN/m². The result is 36.7875 kN/m². Since one kN/m² is one kPa, the uplift pressure is approximately 36.79 kPa. This converts the residual head obtained from the seepage model into an actual pressure intensity.
వివరణ:
Question 17
ప్రశ్న 17
A vertical cutoff is 5 m deep in a Bligh creep profile having total creep length 80 m and total seepage head 6 m. What head loss does Bligh assign to the down-and-up path along that cutoff?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The two faces of the 5 m cutoff contribute 2d = 10 m of creep length. Bligh's assumed head loss per metre of creep is H/L = 6/80 = 0.075. Multiplying by the 10 m vertical creep contribution gives 0.75 m. This calculation follows directly from the theory's linear-loss and equal-weight assumptions. Actual pressure changes around sheet piles are not distributed in this simple manner.
వివరణ:
Question 18
ప్రశ్న 18
If h is the net residual uplift head measured above the top of a floor and G is the specific gravity of the floor material, what simple Bligh-based expression gives the theoretical floor thickness before applying any additional factor of safety?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The floor must provide sufficient submerged weight to resist the net upward water pressure. If h is measured above the top of the floor, the submerged unit-weight factor of the floor material is proportional to G - 1. Balancing the net uplift head against this submerged floor weight gives t = h/(G - 1). Practical design traditionally applies an additional safety allowance and other structural checks. The formula is therefore only the simple gravity-balance expression associated with the Bligh treatment.
వివరణ:
Question 19
ప్రశ్న 19
At a point on a downstream floor, the net residual uplift head above the top of the floor is 2.8 m. If the floor material has specific gravity G = 2.4, what theoretical thickness follows from t = h/(G - 1), before any additional safety allowance?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The submerged specific-gravity factor is G - 1 = 2.4 - 1 = 1.4. The theoretical thickness is t = 2.8/1.4. This gives exactly 2.00 m. The question deliberately excludes any additional safety factor so that only the basic equilibrium relation is tested. An actual floor design must also satisfy structural, hydraulic and construction requirements.
వివరణ:
Question 20
ప్రశ్న 20
Which operating condition commonly produces the maximum seepage head for a Bligh-type uplift and piping check at a diversion structure?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The seepage-driving head is the difference between upstream and downstream water levels. The largest difference generally occurs when upstream water is held high while the downstream side is at a low level. Traditional Bligh design therefore examines this severe static condition for uplift and piping. Equal water levels would produce essentially no net seepage head. The exact governing condition must still be selected from the credible operating combinations of the particular structure.
వివరణ:
Question 21
ప్రశ్న 21
Which statement identifies a major limitation of Bligh's treatment of horizontal and vertical creep?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh simply adds horizontal and vertical path lengths on an equal basis. Field experience and later seepage analysis showed that vertical cutoffs have a different and generally stronger influence on the seepage field than an equal horizontal length. Equal weighting therefore does not represent the actual hydraulic effectiveness of the different path components. Lane's weighted-creep idea was one later attempt to address this deficiency. Khosla's theory subsequently treated seepage through a potential-flow framework rather than a bottom-contour creep path.
వివరణ:
Question 22
ప్రశ్న 22
Why can Bligh's assumed straight hydraulic-gradient line give inaccurate uplift pressures beneath a floor?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh assumes that head falls uniformly with creep distance. Real seepage through soil follows a two-dimensional or three-dimensional potential-flow field. Pressure distribution is strongly influenced by cutoff depth, floor geometry, foundation boundaries and the location considered. The actual uplift curve is therefore not generally a straight line. This discrepancy can be especially important on the downstream part of a hydraulic structure.
వివరణ:
Question 23
ప్రశ్న 23
Which limitation of Bligh's piping criterion is most important near the downstream end of a hydraulic structure?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh's piping check is based largely on the average gradient H/L over the entire idealized creep path. Piping, however, is particularly sensitive to the local upward gradient where seepage emerges at the downstream exit. Later analyses showed that this local exit gradient can be much more severe than an average-gradient picture suggests. Bligh's theory also fails to emphasize adequately the special importance of a downstream cutoff in controlling this exit condition. This is a key reason important modern structures are not designed solely by Bligh's creep criterion.
వివరణ:
Question 24
ప్రశ్న 24
Which statement best describes the status of Bligh's creep coefficient C within the original theory?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Bligh's creep coefficient is not obtained from a rigorous mathematical solution of the seepage field. It was assigned from experience with different foundation materials and observed performance of hydraulic works. The coefficient therefore serves as an empirical safety parameter in the relation L = C H. It is not the same quantity as soil permeability and has different dimensions and meaning. Its empirical origin is another important limitation of the theory.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about Bligh's creep theory: I. Seepage is idealized as creeping along the foundation contact. II. Head loss is assumed proportional to creep length. III. Horizontal and vertical creep receive equal weight per unit length. IV. Safety against piping is assessed using a soil-dependent creep coefficient and an average-gradient concept. Which option is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement I is correct because the theory idealizes the seepage path along the bottom contour of the hydraulic structure. Statement II is correct because Bligh assumes linear loss of head with creep length. Statement III is correct because horizontal and vertical creep are counted equally in the total path. Statement IV is correct because the soil-dependent creep coefficient is used to specify the required creep length and associated average hydraulic gradient. All four statements describe the classical Bligh model, even though several of these assumptions are now recognized as limitations.
వివరణ:
Answer Key సమాధానాల పట్టిక
-
Question 1 ప్రశ్న 1Answer: B. The seepage water is assumed to creep along the contact or bottom contour of the impervious structure from upstream to downstream సమాధానం: B.
-
Question 2 ప్రశ్న 2Answer: A. Head loss is proportional to the length of creep traversed సమాధానం: A.
-
Question 3 ప్రశ్న 3Answer: C. Horizontal and vertical creep are assigned equal effectiveness per unit length సమాధానం: C.
-
Question 4 ప్రశ్న 4Answer: C. L = b + 2(d1 + d2 + d3) సమాధానం: C.
-
Question 5 ప్రశ్న 5Answer: B. 62 m సమాధానం: B.
-
Question 6 ప్రశ్న 6Answer: B. i = H/L సమాధానం: B.
-
Question 7 ప్రశ్న 7Answer: A. L should be at least approximately C H సమాధానం: A.
-
Question 8 ప్రశ్న 8Answer: C. 72 m సమాధానం: C.
-
Question 9 ప్రశ్న 9Answer: B. Safe by this criterion, because H/L = 1/14.4 is less than 1/12 సమాధానం: B.
-
Question 10 ప్రశ్న 10Answer: B. A longer required creep length and a smaller permissible average hydraulic gradient సమాధానం: B.
-
Question 11 ప్రశ్న 11Answer: C. 2d సమాధానం: C.
-
Question 12 ప్రశ్న 12Answer: C. 52 m సమాధానం: C.
-
Question 13 ప్రశ్న 13Answer: B. h_r = H(1 - x/L) సమాధానం: B.
-
Question 14 ప్రశ్న 14Answer: C. 3.75 m సమాధానం: C.
-
Question 15 ప్రశ్న 15Answer: B. The residual piezometric head responsible for uplift pressure beneath the floor సమాధానం: B.
-
Question 16 ప్రశ్న 16Answer: C. Approximately 36.79 kPa సమాధానం: C.
-
Question 17 ప్రశ్న 17Answer: B. 0.75 m సమాధానం: B.
-
Question 18 ప్రశ్న 18Answer: A. t = h/(G - 1) సమాధానం: A.
-
Question 19 ప్రశ్న 19Answer: C. 2.00 m సమాధానం: C.
-
Question 20 ప్రశ్న 20Answer: B. Maximum upstream pond level combined with the lowest credible downstream level సమాధానం: B.
-
Question 21 ప్రశ్న 21Answer: B. It gives equal effectiveness to horizontal and vertical creep even though vertical creep is actually more effective సమాధానం: B.
-
Question 22 ప్రశ్న 22Answer: A. Because actual seepage head loss is generally nonlinear and depends on the geometry of the floor and cutoffs సమాధానం: A.
-
Question 23 ప్రశ్న 23Answer: B. It relies mainly on an average hydraulic gradient and does not properly capture the controlling local exit-gradient concentration సమాధానం: B.
-
Question 24 ప్రశ్న 24Answer: B. It is an empirical soil-dependent coefficient obtained from experience and observation సమాధానం: B.
-
Question 25 ప్రశ్న 25Answer: D. I, II, III and IV సమాధానం: D.