Model Tests Study On Penetration Depths Of Hall Anchor And Speke Anchor

In order to protect the anchor chain and the structures in riverbed/seabed,anchoring velocity can not be too large,anchoring process is completed by the operation of towing.But in the case of extreme weather or mooring errors,the anchoring velocity would increase,in which submarine pipelines and other submarine structres has the risk of destroying caused by the anchor.In order to reduce the occurrence of ship anchoring accidents,reducing economic losses,ensuring a good marine environment,and providing greater security for the staffs,it is necessary to study the depth and velocity of anchoring during the whole anchoring process in detail,as well as the trajectory of the anchor in the process of penetrating into the soil.This paper mainly studies the influence of penetration velocity and soil strength of Hall anchor and Speke anchor on penetration depth in case of emergency anchoring.In this paper,the characteristics of the surface soil of a river in a city are determined by analyzing the engineering situation.Considering the strength of soil and the weight and shapes of prototype anchor,a series of smale scale model tests were carried out.The influence factors of penetration depth of Hall anchor and Speke anchor on clay and sandy riverbed were discussed respectively.In this paper,32 model tests of Hall anchor and Speke anchor penetrating into soil at different vertical velocities are carried out in clay samples with different undrained strengths.The effects of soil strength,anchoring velocity and horizontal velocity on the penetration depth are considered in the model tests.The results show that the penetration depth of both Hall anchor and Speke anchor increases with the increasing of anchoring velocity and decreases with the increasing of soil strength.Under the same anchor velocity and soil strength,the penetration depth of Hall anchor is greater than that of Speke anchor.Horizontal velocity has little influence on the vertical penetration depth of anchor,but it will cause the anchor to have a certain displacement in the horizontal direction.According to the tests data,the empirical formulas which can guide the application of Hall anchor and Speke anchor in-situ are fitted respectively,and the penetration depth of anchor into the river bed with known strength under the extreme velocity is predicted.The additional mass analysis method is established based on the Newton’s second law,and the relationship between penetration depth and penetration velocity of Speke anchor is calculated based on principle of energy conservation programming.The calculation results of this method are in good agreement with the tests results,and the maximum error is less than 10% comared with tests data.For sandy riverbed,the anchoring penetration process of Hall anchor is simulated by small scale model tests with 23 tests in total.The effects of anchoring velocity(1.15-4.4 m/s)and relative density of sandy soil(0.45-0.65)on anchoring penetration depth are considered respectively.The experimental results are analyzed by using the improved empirical formula presented by Sandia National Laboratory.The shortcoming of this empirical formula is pointed out.Then,based on the theory of foundation bearing capacity and the principle of energy conservation,the influence of relative density of sand and anchoring velocity on penetration depth is calculated by programming,and the influence of the selection of bearing capacity coefficients on the calculation results are discussed.