Why certain center to center distance is required for the piles in a group?

Why certain center to center distance is required for the piles in a group?

In the case of friction piles, the spacing must be such a way that the zone of the influence lines on the surrounding soil must not overlap each other. This will hence reduce the bearing values and reduce the settlement.

Is efficiency of group piles less than single pile explain?

However, if the spacing between piles is too close, the zones of stress around the pile will overlap and the ultimate load of the group is less than the sum of the individual pile capacities especially in the case of friction piles, where the efficiency of pile group is much less.

How do you determine the group efficiency of piles?

Feld proposed a rule of thumb to determine the efficiency of a pile group. In his method, the capacity of a pile group is defined as the summation of the capacities of the individual piles in the group multiplied by a factor ranging between 0.72 and 0.94 according to the number of piles.

What is grouping of piles?

Group of piles means when we have more than 1 pile in a row. The efficiency factor Eg is defined as the ratio of the ultimate group capacity to the sum of the ultimate capacity of each pile in the group. It is this factor which is mostly used to express the ultimate load considerations.

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. The pile cap would normally be in contact with the ground. The piles would be designed to share the pile load at ultimate state. A piled raft is a raft foundation that has piles to reduce the amount of settlement.

Which type of pile is termed as simplex pile?

Simplex pile is useful for both soft and hard soils. To obtain simplex pile, a steel tube with cast iron shoe is driven into the ground up to desired depth. After that, reinforcement is provided in the tube and then filled it with concrete. Then, the tube is slowly removed and cast-iron shoe is left at the bottom.

How many types of piles are there in construction?

There are three types of pile foundations according to their construction methods which are driven piles, cast-in-situ piles, and driven and cast-in-situ piles.

What is group efficiency?

For the meaning of group efficiency, because the group efficiency is literally defined as the ratio of the average axial load per pile in the group at the failure state, divided by the ultimate bearing capacity of a single pile and that static load test is always not planned to reach the ultimate state, so the group …

What is group efficiency of pile group?

For piles in sand, the efficiency of the pile group is more than 100\% when the piles are at a close spacing and become equal to 100\% when the pile spacing is about 5-6 times the diameter. Pile group efficiency of 1 is assumed for pile groups in sand.

How do you estimate the group capacity of piles in sand and clay?

Piles in clays or cohesive soils carry most of the load by skin friction resistance of the pile shaft. The load-carrying capacity using static formula is computed on the basis of total stress approach taking ɸu = 0, assuming undrained conditions. The load capacity is a function of the reduction factor, α.

What is the load capacity of the pile group?

The load capacity of the pile group is taken as – Q ug = NQ u … (20.48) For bored piles in sand and gravel, group efficiency is about 2/3 to 3/4. In the case of piles deriving their support mainly from friction and connected by a pile cap, the group may be visualized to transmit load to the soil as if from a column of soil enclosed by the piles.

What are the disadvantages of using piles in groups?

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.

What is the density of sand in bored piles?

Their group capacity adopts as 2/3 to 3/4 time the sum of individual capacities for both the end-bearing ad the friction piles. Thus, In bored piles, there limit densification of the sand surrounding the pile’s group.

How do the piles drive in soil?

For high group efficiency, the piles drive in loose and medium dense cohesionless soils. During the driving operation, the soils compacted around and between the piles due to vibration. For better results, it is essential to start driving the piles themselves to move together as a unit when subject to loads.