You would have to grout the gaps. We are repairing a jetty shortly in Indonesia. Built with concrete piles and backfilled .Now washing out the backfill through the gaps.
Prepakt1 - where in Indonesia? I've been to the ports in Loeksumawe, Padang's Teluk Bayur, Sibolga. Currently in Indonesia's South Sulawesi - Balantang is the main port for the area along with Malili.