Effective erosion mitigation in the Pisha sandstone region is crucial for soil and water conservation in the Yellow River Basin, yet existing vegetation measures are inadequate in water-limited environments. This study examines the application of drought-tolerant biological soil crusts (biocrusts) for erosion control on sandstone slopes and evaluates their erosion-reducing effects under varying coverage and slope conditions through controlled artificial rainfall experiments. Key findings include: (1) biocrusts coverage demonstrated a linear relationship with initial runoff generation time and an exponential relationship with stable runoff generation time. On average, biocrusts delayed initial runoff generation by 396.32 % and extended stable runoff generation time by 153.93 %, thereby increasing the threshold for both initial and stable runoff generation on Pisha-sandstone surfaces. (2) biocrusts reduced runoff volume by an average of 23.89 %, enhanced infiltration volume by 69.19 %, decreased sediment yield by 64.24 %, and lowered the soil erosion modulus by 68.98 %. These results indicated significant promotion of water infiltration and reduction of water erosion. Both effects were positively influenced by coverage and negatively impacted by slope gradient. A critical slope angle of 15 degrees and a critical coverage of 60 % were identified. When the slope was gentle (S 15 degrees), the negative impact of slope predominated, diminishing the positive effect of biocrusts. Additionally, when coverage reached or exceeded 60 %, further increaseing in coverage accelerated the enhancement of infiltration and erosion reduction. Below this threshold, the rate of improvement gradually diminished with increasing coverage. (3) The structural equation model further elucidated that biocrusts mitigate erosion by enhancing the coverage, thereby reducing runoff velocity and modifying the runoff regime. This mechanism effectively dissipates runoff energy, leading to a decreased soil detachment rate and alleviation of soil erosion. Additionally, the relationship between runoff energy and soil detachment rate follows a power function curve, providing an effective method for predicting erosion in Pisha sandstone area. Consequently, biological soil crust technology shows considerable potential for preventing water erosion damage on Pisha sandstone slopes across various gradients.

This study investigates the mechanical properties and damage processes of cement-consolidated soils with Pisha sandstone geopolymer under impact loading using the Hopkinson lever impact test. The mechanical properties of cement-cured soils containing Pisha sandstone geopolymer were examined at various strain rates. The relationship between strain rate and strength of the geopolymer-cemented soil was established. As the strain rate increased, the coefficient of power increase for the Pisha sandstone geopolymer cement-cured soil initially rose before gradually stabilizing. The pore structure of the crushed specimens was analyzed using Mercury intrusion porosimetry. Based on the observed pore changes under impact loading, the pore intervals of the geopolymer-cemented soil were defined. A fitting model linking strain rate and porosity was developed. As strain rate increased, the porosity of the specimens first increased and then decreased, with larger internal pores gradually transforming into smaller ones. The highest porosity was observed at a strain rate of 64.67 s- 1. Crushing characteristics of the cement-cured soils under impact loading were determined through sieving statistics of the crushed particles. The average particle size of the fragments decreased as the strain rate increased. The fractal dimension initially decreased and then increased with the rise in strain rate, reaching its lowest value at a strain rate of 64.67 s- 1. Based on the dynamic mechanical properties, microscopic porosity, and fracture characteristics, the critical strain rate and damage form for cement-consolidated soils with Pisha sandstone geopolymer under impact loading were determined. This study offers valuable insights for the practical application of Pisha sandstone geopolymer cement-cured soils in engineering.

Enhancing the structural stability of Pisha sandstone soil is an important measure to manage local soil erosion. However, Pisha sandstone soil is a challenging research hotspot because of its poor permeability, strong soil filtration effect, and inability to be effectively permeated by treatment solutions. In this study, by adjusting the soil water content to improve the spatial structure of the soil body and by conducting unconfined compressive strength and calcium ion conversion rate tests, we investigated the effect of spatial distribution differences in microbial-induced calcium carbonate deposition on the mechanical properties of Pisha sandstone-improved soil in terms of the amounts of clay dissolved and calcium carbonate produced. The results demonstrate that improving the soil particle structure promotes the uniform distribution of calcium carbonate crystals in the sand. After microbial-induced carbonate precipitation (MICP) treatment, the bacteria adsorbed onto the surface of the Pisha sandstone particles and formed dense calcium carbonate crystals at the contact points of the particles, which effectively enhanced the structural stability of the sand particles, thereby improving the mechanical properties of the microbial-cured soils. The failure mode of the specimen evolved from bottom shear failure to overall tensile failure. In addition, the release of structural water molecules in the clay minerals promoted the surface diffusion of calcium ions and accelerated the nucleation and crystal growth of the mineralization products. In general, the rational use of soil structural properties and the synergistic mineralization of MICP and clay minerals provide a new method for erosion control in Pisha sandstone areas.

This research analyzed the characteristics of the microscopic pore structure of the soil cured with Pisha sandstone geopolymer composite cement under dry and wet cycling conditions. And the internal microstructure of the eroded Pisha sandstone geopolymer composite cement-cured soil was carried out by XRD physical phase analysis and simultaneous thermal analysis-Fourier infrared spectrometry. XRD and simultaneous thermal analysis Fourier infrared spectroscopy were used to analyze the internal microstructure of the cement-cured soil with a Pisha sandstone ground polymer composite under the erosion of magnesium salt, and to obtain the mineral evolution mechanism of the soil. The internal void structure was measured using the mercury intrusion method.The results show that, under the action of magnesium chloride, dry and wet coupled erosion. The strength of the cement-cured Pisha sandstone geopolymer composite soil decreases faster after 7 cycles of dry and wet salt erosion coupling and there is a tendency to soften the load. The porosity of Pisha sandstone geopolymer composite cement-cured soil has increased by 3.88% after 30 cycles of the action of total porosity, of which the percentage of pores in the interval of 10-100 nm decreases. The percentage of pores in the 1000 nm interval decreases. The percentage of pores in the > 1000 nm interval increased significantly. The increase in the proportion of large pores and the decrease in the proportion of small pores caused the specimen structure to become loose, which in turn led to a decrease in strength. The structure of potassium A-type zeolite and dolomite of Pisha sandstone ground polymer composite cement cure soil was damaged under erosion of magnesium salt, and less stable Sepiolite was generated and the CaCO3 content in the system decreased, which gradually evolved into the MgCa (CO3)(2) composite system. This study can provide a theoretical basis for the cement-cured soil of Pisha sandstone geopolymer composite for the construction of agricultural water conservancies in a salt-magnesium environment.

Pisha sandstone (PS) rapidly collapses in water and its performance deteriorates seriously, and its special engineering properties have always been the focus of researchers. In areas where fillers are scarce, it is of great significance to use PS as roadbed fillers to slow down soil erosion and green environmental protection. However, the long-term deformation characteristics after construction need further study. To reveal the long-term dynamic characteristics of Pisha sandstone fillers (PSF) under vehicle load, this study conducted the cyclic loading test of PSF by using the GDS triaxial test system. The deformation characteristics of PSF under different cyclic stress ratios (zeta) and load frequencies (f) were studied. The grey correlation analysis method was used to obtain the correlation degree of each influencing factor to the cumulative plastic strain (CPS) of the PSF. Finally, the grey GM (1,1) model is used to predict the CPS data of PSF. Based on this, the classical semi-logarithmic strain model is modified, and the CPS prediction model of PSF is established. The results reveal that the zeta and f will promote the development of axial deformation of PSF. The axial elastic deformation (epsilon(e)) and CPS of PSF increase with the increase of zeta, and the zeta has a great influence on the CPS. The influence of f on epsilon(e) is more significant at high stress levels and less significant at low stress levels. The influence of f on CPS is opposite to that of epsilon(e), that is, the influence of high stress level is small, and the influence of low stress level is large. According to the degree of correlation, the factors are sorted according to the degree of influence: static strength (sigma(f)) > confining pressure (sigma(3)) > dynamic static stress ratio (eta) > load frequency (f) > cyclic stress ratio (zeta). The GM (1,1) model has high accuracy and reliability for the quantitative description and prediction of the CPS of PSF. At the same time, according to the test and GM (1,1) model prediction results, the CPS prediction model of PSF was established. The research can provide insights and references for the establishment of cumulative deformation and prediction model of PSF under cyclic loading.

Currently, utilization of hydrophilic polyurethane (W-OH) materials for slope protection in arid areas has proved to be a cost-effective protocol. The treatment effect highly depends on the interfacial performance between the W-OH treated and the original sandstone. This study aims to investigate the corresponding shear strength and its long-term performance under dry-wet cycles under the arid environment. The results from the direct shear test indicate the interface shear strength increases with W-OH solution concentration and decreases with the increase of water content of the Pisha sandstone. Further investigations under dry-wet cycles indicate the interface cohesion is obviously weakened by the dry-wet cycles, while the influence on the internal friction angle is not obvious. The correlation between the degradation level and the dry-wet cycles can be well fitted with the inverted Scurve using two combined exponential functions. Furthermore, the ethylene-vinyl acetate (EVA) content is utilized to enhance the durability performance under dry-wet cycles. It is found the EVA can obviously improve the bonding property and the resistance to dry-wet cycles. This study's results can serve as a solid base for the application of W-OH materials to resolve the soil erosion in the arid region.

Pisha sandstone is a kind of sandstone which is easy to collapse by water in Shanxi, Shaanxi and Inner Mongolia of China, and suffers from hydraulic erosion all the year round. In recent years, some scholars have used microbial induced calcium carbonate precipitation (MICP) technology to solidify Pisha sandstone to improve the water erosion resistance of Pisha sandstone. However, for the climate environment with low average temperature in Pisha sandstone area, the commonly used Sporosarcina pasteurii are not well adapted. The purpose of this study is to use the indigenous strainsto solidify the loose Pisha sandstone, and to compare the growth adaptability, mechanical properties and water erosion resistance of the solidified layer with Sarcina pasteurii at different temperatures, and to explore the mechanism of different temperatures and strains affecting the microbial solidification of Pisha sandstone from the micro scale. At the same time, a mixed bacterial liquid solidification test was also set up. The results showed that the solidified thickness of indigenous strains was 4.65 % higher than that of Sporosarcina pasteurii, and the thickness and strength of mixed strains were increased by 19.57 % and 36.62 %, respectively. The growth and solidification effect of indigenous strains were less affected by low temperature. Compared with Sporosarcina pasteurii, at low temperature, the bacterial concentration decrease of indigenous strains was reduced by 26.13 %, the thickness loss of solidified layer was reduced by 13.04 %, and the strength loss of solidified layer was reduced by 13.39 %. The effect of low temperature on the growth of bacteria is mainly reflected in affecting the maximum concentration of bacteria and the growth rate. The effect on MICP mainly reflected in affecting the life activities of bacteria and the crystal form and morphology of calcium carbonate. The research results provide a theoretical basis for the MICP technology application of indigenous strains and multistrains in Pisha sandstone area soil reinforcement and solidification slope.

This study explores the development of a novel alkali-activated cementitious material (APKC) using Pisha sandstone and slag as the main raw materials, offering a sustainable alternative to traditional cement. The APKC's flowability and mechanical properties are comparable to those of ordinary Portland cement (OPC), but it is significantly more cost-effective, with lower carbon emissions and energy consumption. Specifically, at a water-to-binder (w/b) ratio of 0.3, with an optimal activator content of 17.5 % and a Pisha sandstone-to-slag ratio of 1:1, APKC achieves excellent performance: a flowability of 195 mm, and 28-day compressive and flexural strengths of 59.1 MPa and 9.96 MPa, respectively. Moreover, the production of one ton of APKC reduces costs to 64.01 %, carbon emissions to 22.76 %, and energy consumption to 28.56 % of those associated with one ton of OPC, highlighting its potential as a viable replacement in engineering applications. The primary hydration products of APKC include hydrotalcite, C,N-A-S-H gels, C-S-H gels, and natrolines. It is crucial to maintain the alkali activator content and Pisha sandstone-to-slag ratio within optimal ranges, as insufficient alkali dosage or an excessive Pisha sandstone-to-slag ratio can diminish the mechanical properties by reducing hydration product content. Conversely, too much alkali activator can lead to high-porosity hydration products due to the dissolution of Al in C,N-A-S-H gels.

Pisha sandstone (PS) is a special interbedded rock in the middle reaches of the Yellow River that experiences severe weathering and is loose and broken. Due to severe multiple erosion events, the Pisha sandstone region is called the most severe water loss and soil erosion in the world and the ecological cancer of the earth. As a special pozzolanic mineral, PS has the potential to be used as precursors for the synthesis of green and low-carbon geopolymer gel materials and applied in ecological restoration. This paper aims to undertake a phase review of the precursors for geopolymer gel materials. The genesis and distribution, physical and chemical characterization, erosion characteristics, and advances in the ecological restoration of PS are all summarized. Furthermore, current advances in the use of PS for the synthesis of geopolymer gel materials in terms of mechanical properties and durability are discussed. The production of Pisha sandstone geopolymer gels through the binder jetting technique and 3D printing techniques is prospected. Meanwhile, the prospects for the resource application of PS in mine rehabilitation and sustainable ecology are discussed. In the future, multifactor-driven comprehensive measures should be further investigated in order to achieve ecological restoration of the Pisha sandstone region and promote high-quality development of the Yellow River Basin.