Q. Shoes of prefabricated drains?
Shoes are generally installed in prefabricated drains for the below :
(i) It avoids the entry of soils in the mandrel by sealing it at the time of installation of drains.
(ii) It performs just like an anchor to retain the drains at designed depth and to stop the drains from being pulled out at the time of withdrawn of mandrels after driving the mandrels in ground.
Though the inclusion of shoes in prefabricated drains tends to aggravate the problem of smear effect since shoes are normally larger in size than mandrels.