Experimental Study on Clogging Characteristics of Silt Soft Soil in Nansha District of Guangzhou

The silt soft soil in Nansha District of Guangzhou was the softest soft soil in China. It had the characteristics of high natural water content, high compressibility, long consolidation time, and complex layered distribution of soil layers. These characteristics formed the clogging characteristics of silt soft soil, which greatly increased the construction difficulty and hindered the construction progress. Therefore, based on the basic physical and mechanical properties of silt soft soil in Nansha District of Guangzhou, this paper evaluated the clogging characteristics of three silt soft soil areas in Nansha District of Guangzhou through long-term permeability test, and carried out scanning electron microscope test to explore the influence of different parameters and microstructure on the clogging difficulty of silt soft soil. The results showed that the silt soft soil Zone I and Zone II (shallow layer) in Nansha District of Guangzhou were divided into slight siltation levels, and the silt soft soil Zone III (deep layer) was mild siltation level. Large pores were widely distributed in shallow silt soft soil, while the continuity of large pores in deep silt soft soil was poor. The migration of fine particles that failed to establish contact with surrounding particles in the soil blocks the small pores of seepage and thus produces siltation.

Mechanism Analysis of Pore Water Pressure Fluctuation During Clay Precompression Consolidation

Pore water pressure fluctuations are an inherent phenomenon during the consolidation process of clayey foundations, and understanding its mechanism is crucial for comprehending the consolidation process and addressing issues such as drainage blockage during consolidation. This study investigates the consolidation behavior of clay, particularly focusing on pore water pressure fluctuations during the consolidation process of dredged marine sedimentary mud from Daya Bay, Guangdong Province. Given the prevalent use of clay in large-scale construction projects in southern China, understanding the factors influencing pore water pressure is crucial for optimizing consolidation times and improving construction efficacy. Using a custom vacuum preloading model, the research explores the impact of sodium hydroxide on the bound water content and its subsequent effects on pore water pressure dynamics. Experimental findings reveal a distinct inflection point in pore water pressure dissipation, suggesting that particle migration and bound water interactions contribute to the observed fluctuations. These results provide valuable insights for enhancing engineering applications in clay consolidation and mitigating drainage issues, ultimately informing construction practices and reducing project timelines.

Towards understanding the brittle–ductile transition in the extreme manufacturing

The brittle–ductile transition(BDT) widely exists in the manufacturing with extremely small deformation scale, thermally assisted machining, and high-speed machining. This paper reviews the BDT in extreme manufacturing. The factors affecting the BDT in extreme manufacturing are analyzed, including the deformation scale and deformation temperature induced brittle-to-ductile transition, and the reverse transition induced by grain size and strain rate. A discussion is arranged to explore the mechanisms of BDT and how to improve the machinability based on the BDT. It is proposed that the mutual transition between brittleness and ductility results from the competition between the occurrence of plastic deformation and the propagation of cracks. The brittleness or ductility of machined material should benefit a specific manufacturing process, which can be regulated by the deformation scale, deformation temperature and machining speed.

Deformation and removal of semiconductor and laser single crystals at extremely small scales

Semiconductor and laser single crystals are usually brittle and hard,which need to be ground to have satisfactory surface integrity and dimensional precision prior to their applications.Improvement of the surface integrity of a ground crystal can shorten the time of a subsequent polishing process,thus reducing the manufacturing cost.The development of cost-effective grinding technologies for those crystals requires an in-depth understanding of their deformation and removal mechanisms.As a result,a great deal of research efforts were directed towards studying this topic in the past two or three decades.In this review,we aimed to summarize the deformation and removal characteristics of representative semiconductor and laser single crystals in accordance with the scale of mechanical loading,especially at extremely small scales.Their removal mechanisms were critically examined based on the evidence obtained from highresolution TEM analyses.The relationships between machining conditions and removal behaviors were discussed to provide a guidance for further advancing of the grinding technologies for those crystals.