Application of Biological Glue-Clay Composite Substrate in Slope Ecological Restoration.

Given the issues of soil cracking, poor water retention during drought, and erosion damage caused by rainfall, we conducted an in-depth study on the water retention properties, cracking resistance, and scouring resistance of biogel-amended clay using evaporation cracking and scouring tests. The hydrophysical properties and cohesive aggregation mechanism of biogel-amended clay were explored, and the results showed that the incorporation of biogel improved the water retention, cracking resistance, and scour resistance of the clay samples. With an increase in the biogel content, the biogel mucous membrane inside the samples improved the cohesion between soil particles, reduced the generation and development of cracks, and improved the cracking resistance. There was no significant cracking of the samples after the biogel content reached 0.3%, which changed the migration of water in the sample, prevented water evaporation, and improved the water retention of the clay samples. Biofilm can change the migration of water in the sample, prevent some evaporation, and reduce the evaporation rate. To a certain extent, it can enhance the water retention capacity of the sample. Enhanced biofilm content significantly reduced scouring in the process of rainfall and runoff erosion of the sample, and biofilm content of 0.2% significantly reduced the surface of the specimen damaged by erosion. The hydrophysical properties of the composite-adhesive-amended clay samples were significantly improved compared with those of the single-bioadhesive-amended clay samples.

Cracking and erosion behaviors of sand-clay mixtures stabilized with microbial biopolymer and palm fiber.

Drying-induced cracks and precipitation-induced erosion negatively impact the performance of soils in the context of extreme weather events. This study introduces two effective and sustainable materials, microbial biopolymer (MB) and palm fibers (PF), for cracking and erosion control in the sand-clay mixtures. A series of desiccation cracking tests, erosion tests, and SEM tests were conducted to evaluate the effectiveness of the treatment. The results showed that MB could significantly improve the resistance of the soil to cracking and scouring, and the improvement increased with increasing MB content. The optimum MB content was 0.15 % to achieve the maximum cracking and erosion resistance. For samples with varying sand contents, 0.15 % MB addition reduced the crack ratio, total crack length, and accumulative erosion ratio by 19.55 %-96.91 %, 4.22 %-99.58 %, and 57.88 %-89.53 %, respectively. In addition, PF positively affected the anti-crack and anti-erosion properties of the soil, and the application of 0.60 % PF had the best performance for both improvements. The cracks in the soils were mostly fine and shallow with the addition of 0.60 % PF, and therefore, the accumulative erosion ratio decreased by 44.18 %-62.76 % for samples with varying sand contents. Compared to the untreated soil, the degree of cracking and erosion was less due to the formation of a structure with more macropores and a sand skeleton in the treated samples with higher sand content. MB addition provides strong inter-particle bonding connections and a hydrophilic crust structure to improve the soils' resistance to cracking and erosion, while the fiber reinforcement effect benefits from interfacial friction and spatial restriction effects. This study provides mechanistic interpretations of desiccation cracking and erosion behavior in sand-clay mixtures under different treatments. It may guide the design of low-carbon technologies for geotechnical engineering applications.

Experimental Study on Interfacial Friction Characteristics of Reinforced Clay.

Clay is one of the important base materials in slope restoration. The adhesion of clay-rock interface plays a decisive role in the repairing effect on rock slopes. Fibers and polymers are widely used as a clay improvement method in rock slope repair. In this paper, the friction effect of sisal fiber and polyvinyl acetate (PVAc)-reinforced clay was studied through the design of an indoor rock-like interface sliding model test. Using modelled test results and scanning electron microscope (SEM) images, the reinforced clay was analyzed. The test results showed that the critical sliding angle and maximum static friction force of clay decreased with the increase of moisture content. An excess of fiber content and moisture content weakens the coupling effect of fiber-anchoring clay. Fiber content of 0.8% and PVAc content of 2% had the best effect on enhancing the sliding resistance of clay and provided good adhesion for dangerous interfaces of rock slope at 35° and 45°, respectively. PVAc formed a three-dimensional networked elastic membrane structure to improve the skid resistance and dynamic friction coefficient of the clay. The results provide an effective way for soil improvement and ecological restoration.

Using PVA and Attapulgite for the Stabilization of Clayey Soil.

Considering that, in the context of the ecological restoration of a large number of exposed rock slopes, it is difficult for existing artificial soil to meet the requirements of mechanical properties and ecological construction at the same time, this paper investigates the stabilization benefits of polyvinyl acetate and attapulgite-treated clayey soil through a series of laboratory experiments. To study the effectiveness of polyvinyl acetate (PVA) and attapulgite as soil stabilizer, a triaxial strength test, an evaporation test and a vegetation growth test were carried out on improved soil with different amounts of PVA content (0, 1%, 2%, 3%, and 4%) and attapulgite replacement (0, 2%, 4%, 6%, and 8%). The results show that the single and composite materials of polyvinyl acetate and attapulgite can increase the peak deviator stress of the sample. The addition of polyvinyl acetate can improve the soil strength by increasing the cohesion of the sample; the addition of attapulgite improves the soil strength mainly by increasing the internal friction angle of the sample. The strength of the composite is greatly improved by increasing the cohesion and internal friction angle of the sample at the same time. The effect of adding materials increased significantly with increasing curing age. Moreover, polyvinyl acetate and attapulgite improve the soil water retention of the soil by improving the water-holding capacity, so that the soil can still ensure the good growth of vegetation under long-term drought conditions. The scanning electron microscopy (SEM) images indicated that the PVA and attapulgite of soil affect the strength characteristics of soil specimens by the reaction of PVA and water, which changes the structure of the soil and, by the interweaving of attapulgite soil particles, acts as the skeleton of the aggregate. Overall, PVA and attapulgite can effectively increase clayey soil stability by improving the cohesive force and internal friction angle of clayey soil.