The traditional cement-based stabilization cannot effectively stabilize the marine soft clay under submerged conditions. In order to solve this problem, the enhancement of cement-stabilized marine soft clay was investigated in this study by adding the ionic soil stabilizer (ISS) and polyacrylamide (PAM). For this purpose, varying contents of ISS and PAM (ISS-P) were added into cement-stabilized marine soft clay and subjected to curing under submerged conditions. Atterberg limits tests, direct shear tests, unconfined compression strength (UCS) tests, water-stability tests, scanning electron microscopy analysis, and X-ray diffraction analysis were carried out. The results show that using 1.8% ISS and 0.9% PAM as the optimal ratio, the cohesion, internal friction angle, UCS, and water-stability of the samples increased by 182.7%, 15.4%, 176.5%, and 368.5% compared to the cement-stabilized soft clay after 28 d. The increment in soil cohesion with increasing ISS-P content was more apparent than that in the internal friction angle. The combined action of ion exchange attraction and electrostatic adsorption altered the failure characteristics of the samples, resulting in localized micro-cracking and multiple failure paths. Increasing the content of ISS-P strengthened the skeletal structure of soil, reduced inter-particle spacing, and enhanced the water-stability. Additionally, ISS promotes the hydration of cement and compensates for the inhibitory effect of PAM on early cement hydration. ISS-P can effectively enhance the strength and stability of submerged cement-based stabilized marine soft clay.

Sulfate saline soils are widely distributed in Xinjiang, where salt expansion often leads to road cracking and damage. This study investigated the effectiveness of a method that combines fly ash, slag, and polyacrylamide (PAM) in treating saline soils. Various tests, including salt expansion, boundary moisture content, pH, total dissolved solids (TDS), electrical conductivity (EC), sulfate ion concentration, unconfined compressive strength, and freeze-thaw cycle tests, were conducted to evaluate the mechanical and physicochemical properties of the solidified soil. Moreover, scanning electron microscopy (SEM) was utilized to explore the enhancement mechanism and microscopic features. The results indicate that the inorganic-organic combination of fly ash, slag, and polyacrylamide effectively suppresses salt expansion in sulfate saline soil, enhancing its mechanical properties, plasticity, and frost resistance. Considering economic feasibility and practicality, the optimal ratio was determined: a mixture of fly ash, slag, and PAM at 15%, with PAM at 2%. Under these conditions, the treatment exhibits the most efficient inhibition of salt expansion and improves structural integrity. The 7-day unconfined compressive strength of the treated soil reaches 993 kPa, three times higher than that of natural soil. Additionally, the soil demonstrates a significant enhancement in freeze-thaw resistance.

Currently, soil-borne fungal disease (SBFD) have caused a huge damage in agriculture, and small molecule soil disinfectants have been widely used for the prevention and control of SBFD, which could not only kill the chlamydospore of pathogenic fungi, but also completely destroy the microbial community and its functional diversity in the soil, and is not conducive to subsequent plant planting. Therefore, how to effectively inhibit plant pathogenic fungi while maintaining the general balance of microbial population in the soil to facilitate subsequent plant planting come to be critical problem in the prevention and control of SBFD. In this work, a series of polyacrylamide containing quaternary ammonium salts (PAM-X) were synthesized based on the radical copolymerization of acrylamide (AM) and acrylamide containing different quaternary ammonium salts groups (AMX). Owing to the entanglement between polymer chains and soil, PAM-X could be stably absorbed in the soil, thus effectively delaying the free migration of PAM-X chains in soil, and reducing the probability of being leached from soil, which might be the key to obtain novel polymeric quaternary ammonium salts that have less impact on the environment. Banana Fusarium wilt, also known as banana cancer, caused by Fusarium oxysporum f. sp. cubense (Foc), was chosen as a typical soil-borne pathogen disease to verify the rationality of the above thoughts. The results showed PAM-X had well anti-Foc4 activities in soil, and could maintain the general balance of microbial population in the soil, which are almost non-toxic to earthworms in soil and fish, thus provides a new prevention and control method for SBFD.

Climate change and the intensification of extreme weather events constantly pose new threats to all human activities, damaging roads and communication networks, as well as economical activities and threatening human lives. Recently new materials are being considered as potentially useful tools in the prevention of land degradation leading to slope instabilities; among them polymers such as anionic polyacrylamide (PAM) are gaining more and more interest. PAM is known and employed as an additive in agriculture, in the prevention of irrigation -connected erosion, to maximize irrigation and fertilization efficiency and to enhance agricultural yield. Samples were reconstructed in laboratory using kaolin clay and silty sand, respectively, without mixing them to observe the effects of application of anionic polyacrylamide (PAM) on their physical, volumetric, mechanical, and hydrological properties. Fixed values were dry density (1.2 g/ cm 3 for kaolin clay and 1.4 g/cm 3 for silty sand), initial water content (20% and 25% respectively) and polymer application rates (moving from the original 0%, 0.003%, 0.03%, 0.3%, 1% by weight for both parent materials to 0.01%, 0.03% and 0.05% for kaolin clay and 0.1%, 0.3% and 0.5% for silty sand, based on the results of previous analysis). Additional samples consisting of kaolin clay and quartz powder and polyacrylamide (with a concentration of 5% and 50%) were reconstituted specifically for ESEM analysis. The polymer, a granular anionic polyacrylamide provided by Micronizzazione Innovativa Srl, has been manually applied and mixed with the samples, reconstituted in pvc cylinders with a diameter of 9.5 cm and 5 cm high (although some were reconstituted in different cases for specific tests). Samples were then submitted to Atterberg limits with different curing times, hyprop and filter paper tests, WP4C, shear tests, and the record of volumetric characteristics. Results showed that the increase of PAM percentage in samples generally coincided with a widening of samples plasticity range, as well as with the increase of liquid limit and plasticity index; PAM influence was also a matter of time, being more relevant few days after the treatment and then slowly decreasing. Rise in PAM percentage coincided with an increase in samples porosity, and with a higher water retention, although it was impossible to identify a polymer characteristic structure with SEM analysis. These results can shed light on the potential application of polymers such as anionic polyacrylamide as a useful additive for the improvement of soil characteristics that impact on soil stability, in a frame of sustainable solutions for reduction of landslides hazard and risk.