PILE FOUNDATIONS UNDER LATERAL LOADS

1. Methods of calculating ultimate lateral resistance

2. Methods of calculating acceptable deflection at working lateral loads

Methods of Calculating Lateral Resistance of Vertical Piles

A. Brinch Hansen’s Method (1961): This method is based on earth pressure

theory and has the advantage that it is:

1. Applicable for c – Φ soils

2. Applicable for layered systems,

However, this method suffers from the disadvantage that it is

1. Applicable only for short piles

2. Requires trial-and-error solution to locate the point of rotation

B. Broms’ Method (1964% b): 

This is also based on earth pressure theory, but simplifying assumptions are made for the distribution of ultimate soil resistance along the pile length. This method has the advantage that it is:

1. Applicable for short and long piles

2. Considers both purely cohesive and cohesionless soils

3. Considers both free-head and fixed-head piles that can be analysed

However, this method suffers from disadvantages:

1. It is not applicable to a layered system

2. It does not consider c-4 soils

separately

Methods of Calculating Acceptable Deflection at Working Load

A. Modulus of Subgrade Reaction Approach (Reese and Matlock, 1956):

This method assumes that soil acts as a series of independent

linearly elastic springs. This method has the advantage that:

1. It is relatively simple

2. It can incorporate factors such as nonlinearity, variation of subgrade

3. It has been used in practice for a long time

Therefore, a considerable amount of experience has been gained in

applying the theory to practical problems. However, this method suffers

from disadvantages:

1. It ignores the continuity of the soil

2. The modulus of subgrade reaction is not a unique soil property but depends on reaction with depth, and layered systems on the foundation size and deflections.

B. Elastic Approach (Poulos, 1971a and b):

In this method, the soil is assumed to be an ideal elastic continuum.

The method has the advantage that

1. It is based on a theoretically more realistic approach,

2, It can give solutions for varying modulus with depth and layered

1. It is difficult to determine appropriate strains in a field problem and the

system. However, this method suffers from disadvantages that include: corresponding soil moduli

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