GENERAL ASPECTS UNDERPINNING DEFINED PAYMENT FOR UNDERPINNING
WHEREVER the foundation of a building or structure is endangered by a neighboring excavation, the need for underpinning arises. Most frequently, the excavation endangering the neighboring structure is that for a new building planned to go deeper than its old neighbor. But the excavation which endangers the largest number of buildings along a street is that for subways or tunnels.
Indeed, were it not for the recent developments in underpinning methods, many such
subways would not be possible, except, perhaps, at almost prohibitive cost and inconvenience to property owners. Methods and costs of underpinning have a vital
bearing on many engineering problems, as railroads and tunnels can now be placed close to very costly buildings resting on any kind of foundation, and on almost any material, without seriously endangering them or adding a prohibitive amount to the cost of construction.