Jiaqi Zhang

Pile tip post-grouting technology has been widely adopted in pile foundations to improve its bearing characteristics. Grouting in the pile tip leads to the grouting cement spreading along the pile body to a certain extent. To better understand the grout diffusion mechanism along the pile body returned, a total of 45 groups of laboratory model tests were carried out on sand, with different grouting pressures, grout volumes, and soil stress histories taken into account. By comparing the characteristics of the grouted bulbs, the grout diffusion mechanism along the pile body returned was revealed. Combined with the test results, a simplified model to describe the grout diffusion pattern and the corresponding grouting mode of grouting cement along the pile body returned during the process of pile tip post-grouting was proposed. This model can comprehensively reflect the grout diffusion characteristics along the pile body, with different grouting conditions and soil stress histories taken into account.

In order to ensure that the robot has good mechanical properties, stability and hydrodynamic characteristics in underwater motion, and to protect the ROV core control module, battery compartment and other internal precision systems, this paper develops and designs a streamlined underwater robot shell, operating at a depth of 50m, with an overall theoretical linear design, regular shape using strength theory calculations and stress simulation analysis methods, and irregular shape using Solidworks Simutian numerical simulation method, based on Fluent for the overall shell in the fluid stress analysis. The results show that the stress σ₁= 9.33MPa and yield pressure pCR₁ = 13.368MPa for the large spherical shell; the stress σ₂ = 6.67MPa and yield pressure pCR₂ = 13.44MPa for the small spherical shell, both of which are less than the theoretical stress of 42.5MPa and yield pressure P_j=0.8MPa to meet the design requirements for strength and stability; the circular table shape and parabolic The maximum equivalent stress is 0.728MPa ≤ σ_s=50MPa, which meets the physical properties of ABS material; by simulating the stress changes in the three degrees of freedom of the ROV shell in and out, lift and rudder, 527.202Pa, 535.1Pa and 529.1Pa respectively, The yield strength of ABS material is 50MPa, which is much higher than the stresses in the three degrees of freedom of the ROV shell inlet and outlet, dive and rudder, indicating that the ROV meets the stress design requirements in the water.

The selection of grouting methods and parameters significantly affects the improvement in the pile-bearing capacity of cast-in-place bored piles. This study proposes a comprehensive set of test methods for constructing model piles, performing grouting at the pile tip and pile side. A series of single-pile grouting and static load tests were conducted using these test methods. The results reveal that pile-side grouting is more effective in controlling pile settlement compared to tip grouting. Furthermore, tip-side-combined grouting exhibits superior reinforcement effects compared to the other two grouting methods. After grouting, a grout bubble is formed at the outlet, consisting of a compact diffusion zone internally and a split diffusion zone externally. Additionally, a vertical diffusion of grout occurs along the pile body, establishing a lateral friction resistance enhancement region. Within this region, the lateral friction resistance of the pile shows a negative correlation with the distance from the grouting outlet. The test results emphasize the significance of grouting volume and its impact on the bearing capacity, settlement control, lateral friction resistance, and grout bubble size in grouted piles, while the influence of variation in grouting pressure in a small range on bearing characteristics is not significantly apparent.

Central pattern generators (CPGs) inspired from neural system of animal are widely used for the control of locomotion in robots. The objective of this paper is to modeling a CPG-network formed by a set of mutually coupled Van der Pol (VDP) oscillators to generating rhythmic movement patterns for multi-joint robot. Firstly, a VDP-CPG network is made up by four coupled VDP oscillators, which can produce multiple phase-locked oscillation patterns that correspond to the four basic quadrupedal gaits. Then the gait transitions between the different gaits are generated by altering the internal oscillator parameters. At last, we use VDP-CPG network to produce the joints trajectories for AIBO to control the locomotion. The simulation and experimental results demonstrate that the designed VDP-CPG network is effective to control the quadruped locomotion.