Extensive research interest on lunar construction materials, represented by lunar geopolymers, has been driven by the worldwide programs of in-situ lunar exploration. This study comprehensively investigates different combinations between diverse lunar regolith simulants and activators at various curing temperatures, and their effects are revealed by the mechanical properties, microstructure, and composition of resulting lunar geopolymers. This study proposes that glass-rich lunar regolith should be activated by sodium hydroxide to ensure the aluminosilicate dissolution and form dense zeolitic products, whereas sodium silicate is more suitable for glass-free lunar regolith to assist the generation of amorphous products. Additionally, the temperature for the thermal curing of lunar geopolymers should exceed 60-80 degrees C for applicable 24-hour strength. Based on experimental characterizations and statistical analysis of existing data, three determinants of lunar geopolymer synthesis can be emphasized including the compatibility between activator and regolith activity, the calcium and alkali content of regolith, and the temperature of sealed thermal curing. These principles provide valuable guidance on the selection of regolith and activators along with the establishment of curing protocols towards future lunar constructions.

The development of restoration technology and meadows, improvement of run-down pastures, and productivity improvement of old crops of perennial grasses is an urgent problem in agriculture. The tillage traction force in seeder designing and manufacturing is an important indicator of energy efficiency. The objective of this work is to reduce traction force and ensure seeding depth uniformity by justifying the optimal chisel parameters of a grain-fertilizer-grass seeder for direct seeding in sod. The Box-Behnken method was applied to investigate the traction force dependence on the seeder velocity, seed embedding depth, chisel width, and mounting angle. The obtained optimal parameters of coulters were justified by the finite element method. Structural and technological parameters were checked using the smoothed-particle hydrodynamics method on the deformation and wear of the seeder working body. The revealed optimal coulter parameters were as follows: chisel width was 20-20.97 mm, chisel length was 145-148.9 mm, mounting angle was 75 degrees-81.6 degrees, and achieved minimum traction force was 720 N. These parameters ensure the quality of grass seed embedding in the sod. The theoretical data of traction force (8.27-8.39 kN) are in accordance with the experimental (8.28-8.63 kN) data under field conditions. These findings are efficient in agrotechnical and mechanical predictions regarding the occurrence of chisel residual stresses and the working lifetime of the part.

This study was focused on the correlations between the physical and mechanical properties and geostatistical analysis of the clay of high plasticity (CH) soil based on the experimental data and the data collected from various research studies. Four types of CH soil with liquid limit (LL) of 50, 62, 76 and 88% were collected from the field, tested, compared with the data from literature and qualified using hyperbolic model. X-ray diffraction analyses showed the major constituents of the CH soil with LL of 50% were calcium silicate (Ca2SiO4), aluminum silicate (Al2SiO5) and quartz (SiO2) and the major constituents of the CH soil with LL of 88% were montmorillonite (Na, Ca)0.33(Al, Mg)2(Si4O10)(OH)2 center dot nH2O, kaolinite (Al2Si2O5(OH)4 and quartz (SiO2). The index properties, compacted properties, free swelling and compressive strength of the CH soils were investigated and quantified with over 1000 data collected from the literature. Using the mean (mu), standard deviation (sigma), variation (sigma 2) and coefficient of variation parameters of CH soils properties such as density (gamma), index properties (LL and PL), compaction properties (OMC and gamma dmax), swelling index (FS), initial void ratio (eo), compression index (Cc) and undrained shear strength (Su) properties were also studied. Liquid limit (LL) of CH soils varied between 50 and 110% and plasticity index (PI) varied between 26 and 72%. The wet unit weight (gamma wet) for the CH soils varied from 1.30 to 2.19 gm/cm3. Undrained shear strength (Su) of CH soils were varied from 10 to 184 kPa and quantified very well as a function of liquid limit, plasticity index, moisture content and dry density using the experimental data and data collected from the literature.

A great concern for the construction surface cracks of large cross- tunnels, which are being or to be built in the loess strata of China, is attracted. The mechanism of surface crack formation is analyzed from both internal and external perspectives. Loess is a multi-phase porous medium and develops complex stress and strain variation while executing a tunnel project. The surface is highly susceptible to construction surface cracks in shallow sections. A statistical analysis of the constructed loess tunnels in China shows that the main factors affecting surface cracks are settlement deformation, construction scheme, and the surrounding soil environment. To gain an in-depth knowledge of the mechanism of action of factors influencing surface cracks in loess tunnel construction, we relied on the actual project engineering to conduct numerical simulations, which can reproduce the formation mechanism of surface cracks more intuitively. Through numerical simulation, the influence mechanism of tunnel surface cracks under different tunnel diameters, tunnel depths, excavation methods, and surrounding soil grades was obtained. Through the analysis of the factors affecting surface cracks, specific measures to prevent and deal with construction surface cracks are further optimized to provide new ideas for the selection of surface crack control routes in loess tunnels.

Globally, a large amount of phosphogypsum (PG) is produced every year. Most of the PG is stored directly without any treatment, posing a serious threat to the local soil, groundwater and human health. Current researches on the distribution of PG field posllution are all aimed at the surface soil, few studies focused on the distribution of contaminants in the soil under PG. This study used geochemical methods, Pearson'ss correlation analysis, principal component analysis and hierarchical clustering method to analyse the contaminant distribution characteristic in underground soil. This study found that contaminants in the soil can be classified into two categories. Fluoride, total phosphorus, sulfate, Cd, and Hg are one category, and Cu, Pb, As, Cr, Al, Fe, Ni, Zn, and Ba are another category. Each category of contaminants has the same source or similar physical and chemical behaviour, which can be more targeted for future site remediation. Based on the analysis of the mineral composition of the soil, it is found that a large part of the contaminants in the groundwater are caused by the strong acidity of the site. Therefore, the management and control of such acidic sites should pay more attention to the pH status of the site to avoid the release of more contaminants from the site.

In coastal regions of China, extensive areas are characterized by deep and thick silty clay deposits, necessitating excavation and support during engineering construction. This study gathers excavation examples from existing literature and aims to summarize and analyze the deformation characteristics of support structures and the soil behind these structures (supporting walls) resulting from excavation. The findings demonstrate a general trend of increasing maximum lateral displacement of the supporting wall with greater excavation depth. The ratio of maximum lateral displacement to excavation depth falls within the range of 0.18% to 0.64%, while the insertion ratio spans from 0.78 to 1.23. The ratio of maximum ground settlement behind the wall to excavation depth varies between 0.28% and 0.82%. Additionally, the ratio of maximum ground settlement behind the wall to the maximum lateral displacement of the wall ranges from 0.93 to 1.81. The statistical analysis results presented here offer valuable references for the design and construction of excavations in regions characterized by deep and thick silty clay deposits. Moreover, the statistical results can serve as qualitative verification for finite element analysis in specific cases.