Experimental Study On The Holding Performance Of Anchors For Vessels

Marine anchors are important deck equipments for ship handling.The safety of the ship,when anchoring,depends on the stable holding power provided by the anchor to a large extent.However,the selection of anchor relies mainly on experience,in other words,the process of anchor selecting is a process of trial and error.Thus,the understanding of the performance of the anchors is closely related to the safety of the ships.The study of marine anchors helps maritime industry to increase the understanding of marine anchor performance,provides the basis of navigation practice and contributes to the popularization and application of the high-performance anchors and the development of new type anchors.Before researching of the performance of marine anchors,research contents and methods about holding performance of marine anchors were introduced,based on domestic and overseas literatures.4 models of different types of commonly used anchors(AC-14 type anchor,DA-1 type anchor,Pool anchor and Spek anchor)were manufactured.They were of the same quality.A testing program that can be implemented on the beach with comparatively less time and effort was designed,with lessons drawn from the existing research methods.Model test was carried out on coarse sand bottom,soft mud bottom and fine sand bottom.Comparative study of the holding power,stability and the embedment depth on soft mud bottom was performed.Holding efficiency of 4 model anchors on different bottoms were obtained respectively.The curve of holding power to time,according to which the stability could be determined,were graphically shown in force test software.Four anchors were all embedded under the mud bottom completely.The relationship between the embedment depth and holding power was examined by digging up the soil around the anchor,checking the posture of the anchor and measuring the depth of each part.Measurement of the trajectory of anchor in mud was made.The anchor holding power changes significantly in different bottoms.The factors affecting the anchor holding power are anchor type,embedment depth and the characteristics of the bottom.Anchor holding power increases with the embedment depth.When the maximum holding power is reached,the embedment depth no longer increases.In the mud bottom,the embedment motion can be divided into 3 stages as fluke rotating,shank rotating and stabilization.