What is block failure of pile group?
Block failure occurs generally when the spacing of piles is less than about three times the pile diameter. In this case, the soil, bound by a perimeter of the pile group over the embedded length, acts as a single unit or block. Individual pile failure occurs when the piles are spaced at about eight times the diameter.
How do you determine group pile?
If piles are spaced sufficient distance apart, then the capacity of pile group is the sum of the individual capacities of piles….Efficiency of Pile Group
- Spacing of piles.
- Total number of piles in a row and number of rows in a group, and.
- Characteristics of pile (material, diameter and length)
What are three causes of failure of piles?
Flowing strata caused by adjacent excavation or bank sloughing. Tension failure of concrete pile for lack of reinforcement. Eccentricity due to bowing or falling out of plumb. Decay due to lower ground water level.
What is group pile foundation?
A pile group is a set of piles that have a pile cap that means that they act together to carry the load. A major part of the bearing capacity comes from the raft rather than being dominated by the piles (as in a pile group).
How do you calculate the uplift capacity of a pile?
The ultimate uplift capacity, Qu of a pile of diameter d and length L is given by the expression, Qu = ½ Ks σv tanδ π d Zc + Ks σv tanδ π (L-Zc) (1) Or KS = Qu / [1/2 σv tanδ π d Zc + σv tanδ π d (L – Zc)] (2) Where Ks = coefficient of earth pressure σv = effective vertical stress at a depth of Zc = γd Zc γd = dry unit …
What do you mean by pile group efficiency?
The efficiency of a pile group r\g is defined as the ratio of the actual capacity of the group to the summation of the capacities of the individual piles in the group when tested as single piles. However, in dense sand, efficiency may be either greater or less than unity, although the trend is toward i\g > 1.
What is the reason of failure of pile foundation?
1- Inaccurate determination of the bearing capacity of the pile. 2- When the pile load is greater than the design load. 3- Poor and defective workmanship while casting the pile. 4- Corrosion of the timber pile because of assault by insects.
What are the causes of failure of piles?
11 Causes of Pile Foundation Failure
- Load implied on the pile is greater than designed load.
- Defecting workmanship.
- Dislocation of reinforcement of pile.
- End bearing pile resting on soft strata.
- Faulty soil investigation.
- Selecting the wrong type of pile.
- Under-reinforcement of the pile.
- A decay of piles.
What is the efficiency of pile group?
The efficiency of a pile group r\g is defined as the ratio of the actual capacity of the group to the summation of the capacities of the individual piles in the group when tested as single piles.
How long do treated pilings last?
It is reasonable to expect a properly treated round piling to last 30 years in water and much longer on land.
When does a block failure occur in a pile?
Block failure occurs generally when the spacing of piles is less than about three times the pile diameter. In this case, the soil, bound by a perimeter of the pile group over the embedded length, acts as a single unit or block. Individual pile failure occurs when the piles are spaced at about eight times the diameter.
What is the efficiency of a pile group?
The efficiency, which is defined as ratio of average load per pile in the group at failure to the load at failure of a single comparable pile, is less than unity at closer spacing and may reach to unity at a spacing of about 8 times the pile diameter. Again. ———- (5) The pile capacity is taken as the least of the values given by Equations 3 and 5.
What causes a pile group to fail in cohesive soil?
Experimental results have indicated that when a pile group installed in cohesive soil is loaded it may fail by one of the following ways. When piles are spaced at closer intervals, the soil contained between the pile move downward with the piles and at failure, pile and soil move together to give a typical “block failure”.
What happens when piles are used in a group?
1. When piles are used in a group at close spacing, the pressure bulbs of individual piles may overlap, causing more stress in the overlapping soil zones. This causes a reduction in the load capacity. 2.