What is a concrete monolith in this context?

A large, hollow concrete box-like structure, often with internal cells, that is sunk into the ground to act as a foundation or part of a heavy marine structure like a quay wall.

How is a monolith sunk into the ground?

It is sunk under its own weight by excavating soil from within its hollow cells, a process detailed in Clause 6.3. Sometimes, additional weight (kentledge) is added to assist sinking.

What are the primary design checks for a monolith?

The main stability checks involve ensuring an adequate factor of safety against overturning and sliding under all design load combinations, and verifying that the bearing pressure on the foundation soil is within permissible limits (Clause 5.3).

What is 'hearting' of a monolith?

Hearting is the process of filling the hollow cells of the monolith with a suitable material (like sand, gravel, or lean concrete) after it has been sunk to its final depth, to provide mass and stability (Clause 6.4).

IS 9527

: 1974

Code of practice for design and construction of port and harbour structures, Part 1: Concrete monoliths

CurrentSpecializedCode of PracticeStructural Engineering · Ports and Harbours

Download PDF BIS Portal Google

This code of practice outlines the design and construction procedures for concrete monoliths used in port and harbour structures. It covers aspects like material selection, design loads, stability analysis (overturning and sliding), and construction methodologies including casting, sinking operations, and hearting (filling).

Code of practice for design and construction of port and harbour structures, Part 1: Concrete monoliths

Quick Reference Values

Minimum factor of safety against overturning1.5

Minimum factor of safety against sliding1.2

Minimum grade of concrete for cutting edgeM15

Minimum grade of concrete for steiningM15

Typical height of a single lift for casting steining1.5 m to 2.5 m

Key Formulas

Factor of Safety (Overturning) = Σ Resisting Moments / Σ Overturning Moments

Factor of Safety (Sliding) = (μ * Σ Vertical Forces) / Σ Horizontal Forces

Practical Notes

Controlling the verticality and position of the monolith during sinking (known as 'well sinking') is the most critical and challenging aspect of construction, requiring careful and balanced excavation from internal dredge wells.

The design and strength of the 'cutting edge' at the base of the monolith is crucial as it must penetrate the soil and withstand high stresses during sinking.

A thorough geotechnical investigation of the seabed is essential to predict sinking behavior and ensure the final founding stratum provides adequate bearing capacity.