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As a new support structure system, the double-row pile is widely used in foundations in pit engineering, slope engineering, water conservancy engineering, and other fields. It has a big horizontal stiffness and strong anti-overturning ability and has less impact on the surrounding neighboring existing buildings (structures) when it is applied. It must be mentioned that the design experience of the double-row pile is ahead of the theory, and some research has been carried out on double-row pile support structures. This work reviews and evaluates the force deformation and earth pressure on piles of double-row piles, including pile deformation damage mechanism, soil pressure distribution law, and double-row pile structure form. In addition, the problems and shortcomings of the current double-row pile research are concluded. These results have enriched the study of the mechanism of double-row piles, provided the theoretical guidance for double-row pile support structures, and laid the foundation for further theoretical research.

In order to reveal the biological diversity and the evolution of microbial community structure in the process of sludge cultivation and acclimation at the start-up stage of simultaneous partial nitrification and denitrification (SNAD) process, polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the microbial community structure in different operating periods. And molecular cloning was used for species identification and phylogenetic analysis. The 16S rDNA sequence analysis of the characteristic bands of the DGGE profile of total bacteria showed that the bacterial populations in the sludge were rich in diversity, and β- proteobacteria were slightly more abundant and maintained a relatively stable dominant position. With the operation of the reactor, the secondary populations were strengthened and became new dominant communities, such as Firmicutes, γ- proteobacteria, Bacteroides and so on. The 16S rDNA sequence analysis of the characteristic bands of the DGGE profile of ammonia-oxidizing bacteria showed that the strains obtained by sequencing basically belonged to Nitrosomonas of β-proteobacteria. The fast growth rate of this genus made it the dominant ammonia-oxidizing bacteria (AOB) in the activated sludge systems. [ABSTRACT FROM AUTHOR]