Different types of abutment and their properties
Abutment stands for a structure. The ends of a bridge is supported with it.
Retaining Wall is considered as the most recognized abutment structure. Even though other types of Abutments can also be set up and used. The purpose of a retaining is to retain an earth embankment or water.
Abutment offers the following functionalities
Transmits the loads from Bridge Ends to the ground.
Resists any loads which are enforced on it directly.
Offers entry to the vehicular and pedestrian into the bridge.
For Retaining wall, bearing strength of abutment and sliding endurance of the foundation materials and overturning strength should be examined properly.
Types of Abutments: According to standard specifications, the abutments are categorized as follow :-
Stub abutments, Partial-depth abutments, Full-depth abutments, Integral abutments, Partial-Depth Abutment
How to choose perfect abutments: On the basis of the following factors, the most perfect abutments can be chosen :-
a. Construction and maintenance cost
b. Cut or fill earthwork situation
c. Traffic maintenance throughout construction
d. Construction period
e. Protection of construction workers
f. Accessibility and cost of backfill material
g. Superstructure depth
h. Size of abutment
i. Horizontal and vertical alignment alterations
j. Area of excavation
k. Attractiveness and conformity with adjoining structures
l. Prior knowledge with the type of abutment
m. Ease of use for assessment and maintenance.
n. Predicted life, loading condition, and acceptability of deformations.
Forces operative on Abutments: Earth pressures applied on an abutment are categorized with regards to the direction and the magnitude of the abutment movement.
1. At-rest Earth Pressure: It the wall is set firmly and becomes stagnant, the pressure applied by the soil on the wall is known as at-rest earth pressure.
2. Active Earth Pressure: When a wall is shifted from the backfill, the earth pressure is reduced. (active pressure).
3. Passive Earth Pressure: If it is shifted toward the backfill, the earth pressure is raised (passive pressure).