Investigation of the stability of submarine sensitive clay slopes underwave-induced pressure

The exploration and exploitation of marine georesources ordinarily disturbs the submarine soft clay surrounding construction areas and leads to a significant decrease in the shear strength of structured and sensitive clayey soils in submarine slopes. Under wave action, local slides can even trigger large-scale submarine landslides, which pose a serious threat to offshore infrastructure such as pipelines and footings. Therefore, accurately evaluating the stability of submarine sensitive clay slopes under wave-induced pressure is one of the core issues of marine geotechnical engineering. In this paper, a kinematic approach of limit analysis combined with strength reduction technique is presented to accurately evaluate the real-time stability of submarine sensitive clay slopes based on the log-spiral failure mechanism, where external work rates produced by wave-induced pressure on slopes are obtained by the numerical integration technique and then are applied to the work-energy balance equations. The mathematical optimization method is employed to achieve the safety factors and the critical sliding surfaces of submarine slopes at different time in a wave cycle. On this basis, the stability of submarine sensitive clay slopes under various wave parameters is systematically investigated. In particular, extreme wave conditions and special cases of slope lengths no more than one wavelength are also discussed. The results indicate that waves have some negative effects on the stability of submarine sensitive clay slopes.     

An improved particle swarm optimization algorithm with harmony strategy for the location of critical slip surface of slopes

The determination of optimal values for three parameters required in the original particle swarm optimization algorithm is very difficult.It is proposed that two new parameters simulating the harmony search strategy can be adopted instead of the three parameters which are required in the original particle swarm optimization algorithm to update the positions of all the particles.The improved particle swarm optimization is used in the location of the critical slip surface of soil slope,and it is found that the improved particle swarm optimization algorithm is insensitive to the two parameters while the original particle swarm optimization algorithm can be sensitive to its three parameters.     

Discrete Element with Flexible Connector for Dynamic Analysis of 3-D Beam Structures

Combined multi-body dynamics with structural dynamics,a new discrete element with flexibleconnector,which is applicable for 3-D beam structures,is developed in this paper.Both the generalizedelastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diag-onal in a general case.The zero-length rigid element is introduced to simulate the node at which multiple el-ements are jointed together.It may also be effective when the axes of adjacent elements are not in the sameline.The examples for eigenvalue calculation show that the model is successful.It can be extended to thegeometric nonlinear response analysis.     

A finite element method for dynamic analysis of long slender marine structures under combined parametric and forcing excitations

This paper presents a numerical analysis of lateral responses of a long slender marine structure under combined parametric and forcing excitations. In the development of the 3-D numerical program, a finite element method is implemented in the time domain using the Newmark constant acceleration method. Some example studies are performed for various water depths, environmental conditions and vessel motions. The relative amplitudes of combined excitations to a conventional forcing excitation are examined. The response amplitude of a combined excitation is much greater than that of a forcing excitation in the even number of instability regions of the Mathieu stability chart. The results demonstrate that a combined excitation needs to be considered for the accurate dynamic analysis of long slender marine structures subjected to a surface vessel motion.