With the continuous progress of contemporary science and technology and the increasing requirements for marine vehicles in various fields, the intelligence and automation of ships have become a general trend. The autonomous control of surface Unmanned Surface Vessel (USV) generally covers the USV path planning, path tracking control, and autonomous collision avoidance control. But in the whole navigation process of USV, autonomous berthing is also a crucial part. And the research on the algorithm of the automatic berthing process of the USV is less. Mature USV autonomous berthing technology can effectively reduce the cost of human and material resources and financial resources while reducing the accident rate reasonably and safely. Therefore, it is of great importance to comprehensively promote the development of USV autonomous berthing technology.

A number of discrete element analyses of undrained triaxial shear tests on crushable assemblies are performed using 3-dimensional particle flow code (PFC3D). The undrained shear of the samples is simulated by assigning different velocities at the boundaries to control the constant volume of the samples during the shear. Particle breakage is studied using the octahedral shear stress breakage criterion and the fragment spawning mode satisfying an Apollonian sphere packing. The microparameters of the soils are obtained by simulating the test results reported on a Nansha calcareous sand. The effects of particle breakage and drainage condition on the critical state behaviours of the sand are intensively examined. It is found that particle breakage and drainage condition do not affect the slope of the critical state p′−q line. In the e_cs−(p′_cs/p_a)^0.7 space, the critical state line translates downward and rotates clockwise when particle breakage is considered, whilst drainage condition does not affect the critical state line. The intrinsic macro–micro correlations underlying the critical state behaviours are explored by analysing the evolution of representative micromechanical indicators such as coordination number, redundancy ratio, and fabric and force anisotropies.

Analyzing the working conditions of a dam using safety monitoring indices (SMIs) is a relatively intuitive and effective method for dam safety evaluation. Therefore, a reasonable and accurate method for determining the SMIs of a dam is of vital importance for dam safety assessment. However, the current methods for determining the SMIs of dams, especially roller-compacted concrete (RCC) dams, have many shortcomings, such as ignoring the construction process of the dam, the coupling effect among multiple physical fields, etc. In this paper, a novel SMI determination method considering the seepage–stress coupling effects was proposed for RCC dams with the assistance of a constructed seepage and stress coupling model so as to address the deficiency of existing RCC dams in determining SMIs. The coupled mathematical model was developed in COMSOL Multiphysics to establish a finite element analysis model of an RCC gravity dam in Henan Province, China. Moreover, the seepage anisotropy of the RCC construction layers was also considered in the model. Finally, the seepage, stress, and deformation characteristics of the RCC dam were analyzed based on the model, and the seepage and deformation SMIs of the dam were determined and compared with traditional methods. The results show that seepage, stress, and displacement fields are distributed similarly for both coupled and uncoupled models. However, in contrast to the uncoupled model, the hydraulic head contour distribution is more dispersed in the coupled model. Additionally, the stress and displacement simulated by the coupled model increase at different rates, with a more pronounced stress concentration near the dam heel. Comparing the seepage and stress SMIs of RCC dam obtained from different methods, it was found that the indices of dam seepage discharge and crest displacement that are calculated by considering the seepage–stress coupling effect and anisotropic characteristics of RCC construction layers are 34.78% and 31.98% lower than results obtained by ignoring these two effects, respectively. Therefore, it is crucial to consider the seepage–stress coupling effect and the anisotropic characteristics of RCC when determining the SMIs for RCC dams.

This paper presents a probabilistic approach for evaluating the lifetime of reinforced concrete (RC) pipe piles subjected to chloride environments. A predictive model is developed for modeling the deterioration process of RC pipe piles in order to estimate the probabilistic lifetime of RC pipe piles subjected to chloride environments. The time-dependent probabilistic lifetime analysis of RC pipe piles is carried out in the framework of Monte Carlo simulation. An illustrative example of the proposed approach is demonstrated to estimate the probabilistic lifetime of RC pipe piles, and subsequently the sensitivity analysis of governing parameters is conducted to study the effect of the random variables on the probabilistic lifetime of RC pipe piles. The analysis results show that the lifetime depends highly on the governing parameters for corrosion initiation. The failure probability over the lifetime is more sensitive to variations of the governing parameters for corrosion initiation than to variations of the governing parameters for crack initiation.

In the process of oil exploitation, subseatrees sometimes vibrate. In this paper, fluid–structure coupling software was used to study the causes of subsea tree vibration. First, the complex subsea tree model was simplified, and ageometric grid model was established for software calculation. Then, under the given two working conditions, the software Fluent was used to analyze the pressure and velocity distribution of the subsea tree pipeline’s flow field. It was found that the pressure of the flow field changed greatly at the variable diameter and right-angles. Using Ansys Workbench software, flow-structure coupling calculations and modal analysis of the subsea tree were carried out. The results showed that the vibration of the long straight pipeline section was severe. Finally, the paper puts forward the measures to reduce the vibration of subsea tree pipelines and provides construction advice for the safe production of subsea trees.