Bored cast-in-situ piles are generally preferred for most of the industrial structures coming up on marshy or agricultural lands where the ground water table is high and top layers of soil offer very low load carrying capacity. Under such conditions, bored cast-in-situ piles enable the loads to be transferred to hard stratum available at greater depths. However, to carry out proper piling either by rotary or percussion method, existing ground water level can have a detrimental effect on piling process if proper precautions are not followed.
The most fundamental precaution that is often ignored during piling is to provide adequate bentonite head of at least 1.5-2m above the existing ground water level. Maintaining proper bentonite head during piling operation
· Avoids necking of pile as the collapse of soils on the sides is prevented
· Reduces the extra consumption of concrete
Moreover, to provide the additional head the working ground level has to be increased by around 2m using gravelly soils. Such a raise in working platform may reflect additional cost of filling and excavation of soil initially. However, it must be remembered that the cost offsets can be recovered in material savings and by ensuring a much better quality of pile while providing a better working platform devoid of marshy soils.
The most fundamental precaution that is often ignored during piling is to provide adequate bentonite head of at least 1.5-2m above the existing ground water level. Maintaining proper bentonite head during piling operation
· Avoids necking of pile as the collapse of soils on the sides is prevented
· Reduces the extra consumption of concrete
Moreover, to provide the additional head the working ground level has to be increased by around 2m using gravelly soils. Such a raise in working platform may reflect additional cost of filling and excavation of soil initially. However, it must be remembered that the cost offsets can be recovered in material savings and by ensuring a much better quality of pile while providing a better working platform devoid of marshy soils.