Adding cement to soft soils may lead to brittle behavior and the occurrence of sudden damage. Methods to further improve the tensile and flexural properties of cemented clay are noteworthy topics. This paper mainly focuses on the effect of cement and moisture content on the strength and flexural properties of cemented clay reinforced by PVA fiber. The selected clayey soil was a kaolin with cement content of 5%, 10%, and 15% and moisture content of 50%, 56%, 63%, and 70%. The results show that the incorporation of 0.6% fiber can effectively improve the deformability of cemented clay in unconfined compression tests (UCS). The strengthening effect of fiber, as seen in the peak strength and post-peak strength of UCS, was significantly related to cement content. As the water content increased, the compressive strength of the fiber-reinforced cemented clay decreased, but its load-bearing capacity enhanced. When the cement content was 15%, the splitting tensile strength of fiber-reinforced cemented specimens increased by 11% compared to cemented soil, but the deformability of the specimens became poor. In the cement-content interval from 5% to 10%, the bending toughness was significantly improved. Sufficient cement addition ensures the enhancement of PVA fibers on strength and flexural properties of cement-stabilized clayey soil.

Subjected to continuous wave loading, the responses of pile foundations and seabed develop gradually, severely affecting the serviceability of piled structures. This paper presents the results of a series of flume experiments on pile foundations in fine sandy and silty seabed under regular wave loading. Pile-head displacement and pore water pressure were measured and the effects of pile diameter, cross-section, pile stiffness and wave height were investigated. The experimental results indicate that the pore pressure in fine sandy seabed varied only slightly even under 640 s of wave loading but showed an increase of 15.7–25.9% around a pile. In silty seabed with much lower permeability, pore pressure accumulated quickly due to piles and oscillated impressively at the depth of soil liquefaction. Based on the comparison between the calculated and measured pile-head displacement, we found that the response of smaller-diameter piles in lower-permeability seabed was much more easily magnified by the induced pore pressure. Increasing the pile diameter and attaching fins could lead to a smaller response of piles. Wave height was a major factor in the experiments that affected the development of response.

In this paper, we study the characteristics and components of mobile wireless mesh backbone networks (MWMBNs). How to maintain the heterogeneous network connectivity in mobile scenarios is important. We propose a topology control algorithm based on the group mobility model for MWMBN to maintain network connectivity in mobile scenarios. It includes the following work: MWMBNs is classified into the mobile wireless backbone node group (MWBNG) and unit groups (UGs). the MWBNG is composed of all the MWBNs while the UG is composed of a MWBN and several TNs connect it. In the MWBNG, we propose the reference points assignment algorithm (RPAA) based on the RPGM model. In the UG, the TNs has different communication radius with the MWBNs', we propose the topology control algorithm based on tolerate zone using nomadic community mobility, the control algorithm does not need to use any control information to maintain topology control or to change the routing table. The TNs change the self-position to maintain the connectivity with the MWBN. The simulation results show the topology control algorithm based on the group mobility model for MWMBN to maintain the heterogeneous network connectivity when they move together.

Negative skin friction induced by surcharge loading represents a critical geotechnical issue, compromising the performance of pile foundations and associated superstructures. Although surcharge-induced negative skin friction has been extensively investigated for single piles, the underlying pile group effect and the effectiveness of isolation piles in mitigating dragload development remain insufficiently understood. To address these gaps, controlled laboratory model tests were conducted on a single pile and a 3 $\times$ 2 pile group subjected to surcharge loading. Axial strains along the pile shafts and pile-head displacements were continuously monitored to quantify the distribution characteristics of negative skin friction, evaluate pile group interactions, and assess the influence of isolation pile spacing on the reduction of negative skin friction acting on engineering piles. The results demonstrated that a pronounced pile group effect was generated under surcharge loading. Relative to the single-pile condition, the average negative skin friction acting on corner piles and center piles was reduced by 10.04% and 15.36%, respectively, indicating that the center pile was more strongly influenced by the pile group effect. Furthermore, the installation of isolation piles was shown to effectively decrease pile-head displacement, pile-shaft stress, and surcharge-induced negative skin friction. The mitigation efficiency was found to be strongly dependent on isolation pile spacing, with closer spacing producing a more pronounced shielding effect. As the spacing between isolation piles and engineering piles was reduced from 6$D$ to 2$D$, the reduction rate of average negative skin friction increased from 7.55% to 20.13%. However, the incremental improvement became progressively less significant when the spacing was smaller than 4$D$. These findings provide experimental evidence for the pile group behavior of surcharge-induced negative skin friction and offer practical guidance for the design and optimization of isolation-pile systems intended to mitigate dragload effects in pile-supported structures.