Comparison of Effect of Different Embedment of BCIS Pile in Competent Soil Strata

Normally the resistance of pile for compressive loads is mainly through interface friction on a pile shaft and end bearing resistance of pile. In locations where the soil strata or type of soil varies drastically along the length of the project scope, to have proper end bearing resistance it is required to terminate the pile into a competent strata (SPT N > 100) with minimum embedment of 1× diameter. For a marine project in Gujarat, India, 1,200 mm diameter BCIS piles were proposed to support the outfall jetty structure. Geotechnical investigation was carried out to understand the stratification along the length of structure; it was observed that top 6−9 m is filled up soil with fly ash, and the strata vary drastically along the structure location. Due this uncertainty in variation of strata, the pile was mainly designed to take the resistance from end bearing. Therefore, initial load tests were proposed with various embedment depths into competent strata to arrive at the required pile length. Total five numbers of initial compression load test were conducted. The pile embedment adopted for initial load test were 1 times/2 times/3 times/5 times diameter into competent strata. Piles were provided with 8 mm thick permanent MS liner as the structure is located near the sea. Bentonite was used as stabilizing fluid for five test piles, and water was used for another test pile. This paper describes the stratification at the project location, initial load test results for various embedment depths into competent strata, influence of various factors like type of stabilizing fluid, liner depth, method of liner driving, concrete timing on the pile capacity.