Settlement Analysis Of The Pile Foundations Of The Offshore Platform Based On Field Monitoring

The pile foundation is a type of foundation used widely in offshore structures. It supports nearly all the acting loads on the structure and is the basic guarantee for structure safety and serviceability. The design code and the theoretical research of the pile foundations on land tends towards mature gradually. However, there exist many potential safety hazards during the design and construction period of pile foundation of offshore platforms because of the uncertainty of the oceanic environment and the complicated relations among platform structure, pile foundation and soil. In order to reduce the hazards, the real-time monitoring techniques and protective measures have to be adopted. Nevertheless, it is difficult to set up a fixed basis of reference for the platform far from land and thus cause a technical difficulty in monitoring.In this thesis, an offshore jacket platform in Bohai Bay was taken as an example. The safety monitoring for the pile foundation was divided into the load monitoring and settlement monitoring respectively based on bearing capacity of the pile foundation. The monitoring technique was illustrated specifically and the scheme design of sensor placement for the on-site environment was given in detail. The load monitoring system and the settlement monitoring system for pile foundations was set up respectively. The real-time monitoring load data with high precision were obtained by means of temperature-drift compensation for fiber gratings. A relative settlement measure method was developed for the offshore jacket platform since the fixed reference did not exist in the oceanic environment. The amount of settlement of each pile was calculated according to the mass distribution of upper deck of the platform structure. An early warning value was selected on the basis of the monitoring data and the calculated results. At last, an evaluation for the settlement of the platform was carried out.The monitoring method proposed in this thesis can analyze and predict the platform settlement accurately. It provides scientific basis for safety early warning and life safety evaluation of platforms and ensures safety in production of the platforms in service. The analyses of loads and settlement of pile foundations based on monitoring also provide scientific basic guide for new pile foundation design.