Sea trials of Sigma wave energy converter – slacking and snapping of TLP mooring lines

Sigma Energy has performed its foremost prototype tests of scaled wave energy converter in a real sea environment. The prototype was a point absorber with a cylindrical buoy, a mechanical power take-off system with a counterweight, moored to the seabed as a tension leg platform (TLP) with three equal tendons. In these extensive experiments, numerous device characteristics were measured and analysed. The present paper focuses on the dynamic forces in the mooring lines, and some unexpected and rare data obtained. It is well known that TLP tendons are prone to a brief loss of tension (the slacking) and that, after such events, high snapping forces of short duration can arise. Partly by intention, and partly due to underestimation of the dynamical forces, several such slacking-snapping incidents were recorded during the experiments. In some severe storms, the snapping forces were up to six times higher than the tendon pretension. The paper presents several recordings of dynamic forces and platform motion during these critical events. It analysis them, and gives a typical scenario under which they occur. It gives also some theoretical explanations, and numerical predictions of dynamical tendon forces, with their comparison to the experimental results.     

基于工程实践的接头箱被埋后处理措施研究

地下连续墙接头箱被广泛应用在地下连续墙施工，接头箱被埋事故时有发生。根据实际项目工程实践，对接头箱被埋原因进行综合分析，总结出包括技术、施工环境两类原因。提出接头箱被埋后的三种处理措施，分别为吊车顶拔、油顶配合吊车顶拔以及侧向剥离。并基于某水厂扩建工程接头箱被埋事故，给出该事故原因分析、实际处理措施以及处理结果，最后提出部分施工建议，以期为相关事故提供有效解决方法。