Numerical Simulations On The Installation Of An Innovative Lightweight Gravity Installed Plate Anchor In C-? Soil

As offshore developments move into deeper waters,anchored floating facilities show greater reliance than fixed structures.The floating facilities are connected with the anchorage foundation buried in the seabed through the anchor chain.Therefore,capacity-efficient and cost-effective anchoring systems are required to fit the deepwater environments to tether floating structures.Recently,the dynamically installed anchor(DIA)has attracted more attention due to its economical and quick installation.The DIA is first released from a predetermined height above the seabed,allowing it to fall freely into the water column to obtain kinetic energy.Then the anchor penetrates into the seabed by its kinetic energy.Typical DIAs used in offshore engineering are the torpedo anchor and OMIN-Max anchor.However,the holding capacity of the torpedo anchor is relatively low,and the penetration depth of the OMNI-Max anchor is relatively shallow.Therefore,the research group designed an innovative lightweight gravity installed plate anchor(L-GIPLA)with large penetration depth,high capacity efficiency,diving property and low cost.In the present paper,the penetration depth and keying behavior of the L-GIPLA in sand and silt(c-? soil)were investigated through numerical analysis,which provides theoretical guidance for the application of the L-GIPLA.In the first part of the thesis,the penetration process of the L-GIPLA in sand was studied through large deformation finite analysis.The traditional Mohr-Coulomb model cannot simulate the strain softening property of dense sand,therefore a modified Mohr-Coulomb model was adopted in the present study.Then the influence of impact velocity,sand relative density,and frictional coefficient on penetration depth was analyzed using coupled Eulerian-Lagrangian(CEL)approach.The results show that with the aid of a booster,the anchor tip embedment depth of the L-GIPLA is 1.20-2.49 times the anchor length.According to the results of numerical analyses,an empirical equation for predicting the penetration depth of the L-GIPLA in sand was proposed based on the total energy method,which is convenient to predict the anchor penetration depth in engineering applications.In the second part of the thesis,the penetration depth of L-GIPLA in silt was studied,and the effect of softening and rate effect on the penetration depth was considered.The results show that with the aid of booster,the penetration depth of L-GIPLA is 0.73-4.65 times the anchor length.When the friction angle ? ? 40°,the anchor penetration depth is relatively shallow,and the anchor cannot provide sufficient capacity.In the third part of the thesis,the keying behavior of the L-GIPLA was studied using the CEL approach.The influence of the anchor chain was considered by the VUAMP subroutine,which avoids establishing the anchor chain model and increases the computational efficiency.By changing the soil strength parameter,the padeye offset,and the anchor embedment depth,the factor affecting the keying property of the L-GIPLA has been understood.When ? = 10°,the L-GIPLA can dive.With the increasing of embedment depth,the holding capacity of the anchor increases gradually,and the anchor moves to the horizontal direction.Therefore,the increasing of the anchor penetration depth is beneficial to improving the anchor capacity.