Civil Engineering Test - 4

Explanation:

The load carrying capacity of a bored cast in-situ pile in sandy soil is much less than that of a driven pile of similar dimensions because A driven pile generates much more point bearing resistance than a bored pile.

Bored piles transfer the load through friction only whereas driven piles transfer the load by both point bearing as well as friction. 

Bored Pile Advantages: 

• Piles of variable lengths can be extended through soft, compressible, or swelling soils into suitable bearing material.
• Piles can be extended to depths below frost penetration and seasonal moisture variation.
• Large excavations and subsequent backfill are minimized.
• Less disruption to adjacent soil occurs.
• Vibration is relatively low, reducing the disturbance of adjacent piles or structures.
• For many design situations, bored piles offer higher capacities with potentially better economics than driven piles.

Driven Pile Advantages:  

• Piles can be precast to the required specifications.
• Piles of any size, length, and shape can be made in advance and used at the site. As a result, the progress of the work will be rapid. 
• A pile driven into granular soil compacts the adjacent soil mass and as a result, the bearing capacity of the pile is increased. 
• The work is neat and clean. The supervision of work at the site can be reduced to a minimum. The storage space required is very much less. 
• Driven piles may conveniently be used in places where it is advisable not to drill holes for fear of meeting groundwater under pressure. 
• Driven piles are the most favoured for works over water such as piles in wharf structures or jetties.

Explanation:

Critical path:

It is defined as the longest sequence of tasks that must be completed in order to complete the project or the minimum time in which the project can be complete and is denoted as a dark line in the diagram given below ie ABEF.

Explanation:

The rupture of a finite slope may take place along one of the following surfaces:

1) Planer surface:

• This type of failure commonly occurs in a soil deposit or embankment with a specific plane of weakness.
• Occurs in non cohesive soil
• Excavation in stratified deposit quite often leads to a planar failure surface along a plane parallel to the strata.
• Similarly in composite earth dams with sloping cores, planes of weakness within the bank may consist of two or three planar surface

2) Circular failure surface:

• For simple idealized problems, the assumption of a circular failure surface is significantly accurate.
• In this the failure surface have arcs somewhat flatter at the ends and sharper at the centre.
• Collin observed that the rupture mass slides down a sliding surface, in a definite pattern resembling that of the a cycloid and circular failure was first introduced by Peterson

3) Non circular (Composite) failure surface: 

Condition for composite failure in homogenous surface:

1. Foundation of infinite depth
2. Rigid boundary planes of maximum or zero shear
3. Presence of relatively stronger or weaker layer

Condition for composite failure in non homogenous surface:

1. Presence of soft layer in foundation
2. Use of different type of soil or rock in the dam section with varying strength and pore pressure condition
3. Use of drainage blankets to facilitate dissipation of pore pressure

Concept:

The length of the transition curve is designed on the basis of a maximum of two criteria and the length of the transition curve should not be less than the minimum length of the transition curve.

Case-1: As per the rate of change of centrifugal acceleration,

Important Point:

While drawing perpendicular bisectors, the bisectors should not cross any station.

Concept:

In the interval of -ℓ to +ℓ, the Fourier series is represented as

Fourier series of f(x)

Concept:

For different roots of the auxiliary equation, the solution (complementary function) of the differential equation is as shown below.

Concept:

Taylor series Method: Consider the first-order differential equation as:

Concept:

The standards of disposal into marine coasts are described in IS 1968 of 1976.

1. The sewage must be disposed of at the time of low tides.
2. The sewage should be released at least 3 - 5 m below the water level.
3. The sewage should be disposed of at least 1.5 - 2 km away from the shore to prevent its backing up on the shore.