Model Tests On Long-term Capacity Properties Of Expansive Stressed Grouted Clamp

Expansive stressed grouted clamp is a new type technology of repair andreinforcement, which is mainly used for repairing underwater damaged members ofoffshore structures, and has the advantages of a high tolerance of imperfection, goodfatigue properties, a high construction efficiency and low construction costs.Long-term capacity is a key performance indicater which affects the applicationprospects in engineering of this clamp. This paper researches the long-term capacityof expansive stressed grouted clamp, and three research works are carried out:Firstly, factors affecting the long-term capacity of the clamp are researched.Long-term capacity of expansive stressed grouted clamp is mainly affected by twofactors: shrinkage and creep of the grouting cement and performance of the expansiveagent. The research shows that shrinkage and creep will decrease the expansivepressure inside the clamp, which is bad for the long-term capacity; expansive agentcan provide a good long-term expansive pressure and increase compactness of thegrout, which is good for the long-term capacity. After grouting is completed, whethercreep will decrease the long-term expansive pressure and whether expansive agentwill eliminate this adverse effect have a very important influence to the long-termcapacity of expansive stressed grouted clamp, and this is also the theory starting pointof experiment research to the long-term capacity.Secondly, long-term capacity of the clamp is experimentally researched. In thephysics experiment, clamp models are grouted and maintained in water tanks for oneyear. Slip capacity is tested by the universal testing machine, and then slip stresscould be calculated; Length of the stub bolts should be regularly measured so that wecan calculate expansive pressure. It shows that, compared with the results ofshort-term specimens after28days of maintain, expansive pressure and slip stress of long-term specimens after1year of maintain don’t decrease, on the contrary,long-term slip stress increases by an average of more than30%especially. By analysis,it is mainly because that long-term compactness of grout is enhanced by calciumoxide in the expansive agent and expansion of grout is well limited by the clampconstruction. It is demonstrated that the expansive stressed grouted clamp has a gooddurability and load capacity, so it is suitable for underwater repair and reinforcementof offshore constructions.Thirdly, the expansive pressure distribution on the outer surface of damagedinner tube is tested. we test the stain of different places in damaged inner tube inexperimental method, then calculate expansive pressure. The result shows thatexpansive pressure distribution on the outer surface of damaged inner tube is notuniform.This paper shows that long-term capacity property of expansive stressed groutedclamp isn’t influenced by shrinkage and creep of the grouting cement, instead,because that long-term compactness of grout is enhanced by calcium oxide in theexpansive agent and expansion of grout is well limited by the clamp construction,long-term capacity is better than short-term capacity. This shows that grouted clampshave a good durability and load capacity. It meets the demand of most underwaterstructures and pipelines reinforcement, so this type of expansive agent is suitable forunderwater repair of offshore constructions.