Although certain achievements have been made in desertification control in China, the fragile ecological attributes of sandy lands have not been fundamentally altered. This study systematically investigates the bio-reinforcement mechanism and engineering applicability of desert sand based on Enzyme-Induced Calcium Carbonate Precipitation (EICP) technology using soybean urease. Through regulating soybean powder solution concentration, standing time, temperature, and pH, we revealed the regulation mechanism of urease activity. Single-factor experiments with varying enzyme-to-gelatin ratios, cementing solution concentrations, and spraying volumes of reaction solution were conducted to examine their effects on surface strength, calcium carbonate content, and cured layer thickness of desert sand. Finally, water retention tests were performed to evaluate the application performance of EICP-treated aeolian sand. Results demonstrate that soybean powder concentration, temperature, and pH significantly influence urease activity, with maximum activity achieved at 100 g/L soybean powder concentration, 45°C, pH=7, and 12 hour standing time. The effects of enzyme-to-gelatin ratio and cementing solution concentration on reinforcement indicators (surface strength, CaCO₃ content, cured layer thickness) followed an initial increase followed by decrease pattern, peaking at enzyme-to-gelatin ratio 1∶1, cementing solution concentration 1.25 mol/L, and reaction solution spraying volume 5 L/m². Water retention tests revealed that cementing solution concentration and spraying volume are critical factors in controlling CaCO₃ crystal formation to fill sand particle pores, achieving maximum water retention enhancement of 42% and significantly inhibiting water evaporation.

With the promotion of the national policy of developing the western region, the shortage of building materials in the surrounding areas of the northwest desert in China has become increasingly severe, making wind blown sand the main building choice an urgent need. This study innovatively utilized local waste drilling mud and lignin composite materials to improve aeolian sand, exploring the effects of different ratios of composite solidification materials on the unconfined compressive strength and impermeability characteristics of sand samples. The research results show that: ① Drilling mud and lignin as solidifiers can significantly improve the unconfined compressive strength of sand samples, and its strength shows a linear increasing trend, and with the extension of curing time, it first decreases and then tends to stabilize. ② With the addition of curing agent, the impermeability of the sample has been significantly improved, and this trend shows an initial decrease followed by a stabilization over time. The appropriate proportion of drilling mud and lignin fills the pores inside the sample, wraps around soil particles, and optimizes their structure, making the soil more compact. At the same time, combined with the bonding effect of ion curing agents, it can effectively reduce the size and connectivity of pores, thereby enhancing their ability to resist water infiltration. ③ A composite wind blown sand solidifier was proposed, with an optimal ratio of 3% drilling mud and 8% lignin. This solidifier is economical and environmentally friendly. This study can provide a new idea for the improvement of building materials and the resource utilization of drilling mud in the northwest wind blown sand area.

To enhance the erosion resistance of loess slopes, urease-induced calcium carbonate precipitation (EICP) technology was introduced to strengthen the loess slope in this study. Through permeability, disintegration, slope model erosion, and microscopic tests, the water stability and erosion resistance of EICP-treated loess under different treatment conditions were systematically studied, and its treatment mechanism was discussed. The results indicate that the permeability and anti-disintegration characteristics of loess can be significantly improved after two rounds of EICP treatment when the soybean urease concentration is 80 g/L, the cementation solution concentration is 1.0 mol/L, and the mixture ratio is 1∶1. Under simulated extreme rainfall conditions, no splash erosion pits or gullies developed on the solidified slope. The runoff rate remained stable, sediment concentration in the runoff was negligible, and the water content of the slope increased significantly less than that of an unsolidified slope. Additionally, the difference in elevation between the two types of slopes after erosion follows the normal distribution approximately. Microscopic analysis shows that the cementation solution concentration dominates the effect of EICP treatment by regulating the size and spatial continuity of calcium carbonate crystals. This technology forms a dense three-dimensional network structure within the loess, which effectively divides the pore structure of soils. Therefore, EICP technology has good engineering application potential in improving the impermeability and erosion resistance of loess slopes.

Shallow fine roots enhance soil shear strength and play a critical role in vegetated slope stability. While prior research focused on factors like soil type, moisture, root arrangement, and plant species, the relationship between root characteristics and root-soil composite strength remains underexplored. This study employs direct shear tests on saturated Amorpha fruticosa root-loess composites to systematically investigate the influence of root content, root length, and key parameters (root area index - RAI, root length density - RLD, root volume ratio - R_v) on shear strength. Results show: ①under low vertical loads, shear strength increases significantly with root content, but this effect weakens under higher loads; ② reinforcement primarily enhances cohesion, with minimal impact on internal friction angle; ③ for root length ≥2 cm, an optimal root content (1%-1.5%) maximizes cohesion; ④ shear strength correlates strongly positively with RAI and R_v, but weakly with root content, biomass, RLD, and specific root length, indicating dominance of root-soil interface friction under saturation. This work clarifies the mechanical mechanisms of root reinforcement in saturated loess, identifies a specific optimal root content, defines key root characteristic-strength relationships (RAI, R_v, average diameter), and provides a new theoretical basis for the comprehensive understanding of the mechanical effects of vegetation slope protection in loess areas and the scientific design of ecological slopes.

The railway network in the Loess Plateau routinely traverses high-density farmland irrigation corridors, where the subgrade continuously accumulates excessive post-construction settlement, severely threatening the millimeter-level smoothness control requirements of railways and posing significant challenges to train operation safety. This study addresses the prominent conflict between routine farmland irrigation practices and the stability requirements of railway subgrades in this region. Through field investigations at a typical site along the Baoji-Zhongwei Railway and dynamic triaxial laboratory tests, the causes of subsidence in loess subgrades under irrigation were identified, and the dynamic residual deformation characteristics of loess after wetting were revealed, along with proposed prevention-control thresholds. The research demonstrates that periodic irrigation-induced moisture fluctuations in the subgrade soil, combined with long-term cyclic train loads, are the primary drivers of severe settlement. By conducting comparative simulation tests of train load waveforms under varying drainage conditions, it was found that the residual strain under semi-sinusoidal wave loads decreased by 15%~20% compared to conventional sinusoidal waves, confirming that semi-sinusoidal waves better reflect real-world train dynamic load characteristics. A dynamic residual strain model for loess was established, incorporating consolidation stress, dynamic stress amplitude, and vibration cycles. Preliminary predictions of subsidence in actual irrigation zones using this model aligned well with field observations. The findings provide a theoretical foundation for long-term settlement prediction of railway subgrades in loess regions and hold significant engineering value for advancing lifecycle safety assessments of subgrade defects under coupled vibration-seepage interactions.

The identification and measurement of rock joint cracks is an important basis for the characteristics of rock structural planes and the evaluation of rock quality. The traditional identification of rock joint cracks in boreholes is mainly manual and inefficient. In this paper, the deep learning convolution neural network Mask R-CNN algorithm model is used to construct the data set by labeling and standardizing the features of the image joints and cracks. The Mask R-CNN model is trained to construct the intelligent recognition and segmentation model of rock joints and cracks, so as to realize the intelligent recognition and segmentation of the observed image. The rock joint cracks are skeletonized by binarization and sine wave fitting, and the occurrence of rock joint cracks is calculated, so as to realize the statistics of rock joint cracks on the borehole wall by digital means. The technology is compared and verified by project examples. The results show: ①the non-directional rock joint fracture can be extracted by a specific algorithm model, and its corresponding occurrence can be calculated by multi-point fitting of sine curve. ②The accuracy of the measurement results can reach more than 85 %. ③With the increase of the number of different morphological samples of joint cracks, the recognition accuracy can be increased. ④The intelligent identification and measurement results of rock joint cracks can describe the rock structural plane in detail and be applied to the evaluation of rock integrity and quality grade.

In response to the complex formation mechanism of loess landslide disasters and the insufficient accuracy of traditional investigation methods, this study proposes a "space ground number" collaborative analysis method. The typical loess landslide body that occurred in Yangjiagou Town Industrial Park, Mizhi County on September 14, 2023, is taken as the research object. Three dimensional terrain data with centimeter level resolution is obtained through unmanned aerial vehicle aerial survey technology to reconstruct the geometric shape characteristics of the landslide body; Reveal the characteristics of controlling structural planes and stratigraphic combinations through on-site geological surveys. Based on the mixed finite element discrete element numerical simulation (Y-Mat), a dual scale model considering the real geometric shape and structural plane distribution is constructed. Through simulation, it is revealed that due to the influence of terrain and crack water conduction, the slope foot softens when encountering water, the strength decreases, and the upper loess body is pulled to deform. When the deformation accumulates to a certain extent, it collapses downwards along the original through water conduction cracks. During the falling process, some loess disintegrates and accumulates within a certain range of the slope foot, forming loess blocks and loose soil of different sizes, which impact the buildings at the slope foot and cause them to collapse. The research results can provide multi-source data fusion analysis methods and technical support for the study of the evolution mechanism of landslide geological hazards in the Loess Plateau.

Land surface displacement is the most intuitive feature of the development, evolution and destruction of geological hazards. MT-InSAR technology can achieve long-term monitoring of land surface displacement, but its data processing process is time-consuming and requires specialized knowledge of processing personnel, which seriously hinders its widespread application. Based on this, the author introduces the characteristics of the data of the HyP3 cloud platform, analyzes the difficulties of land surface deformation monitoring based on this data with large phase unwrapping error and inconsistent deformation reference, and designs a technical route for MT-InSAR monitoring of surface deformation based on HyP3 cloud platform. This technical route suppresses the influence of phase unwrapping error on the deformation monitoring results by adding the automatic selection of the unwrapped interferogram and the correction step of the phase unwrapping error in the traditional SBAS-InSAR technology. In this paper, in the phase unwrapping error correction step, the phase non-closing problem is solved by restoring the reference phase, and the problem of no feasible solution in linear programming is solved by adding relaxation variables. The proposed technical route is used to obtain the surface deformation of Yan'an New District in 2020～2021, and the reliability of the technical route is verified by comparing with the calculation results based on the original SAR data.

In the grouting reinforcement of water-rich sand layers, the pore structure and spatial distribution of the cemented bodies directly influence reinforcement effectiveness and grout diffusion paths, serving as critical criteria for evaluating grouting quality and optimizing operational parameters. However, due to variations in sand grain size distribution and non-uniform grout diffusion, existing studies remain insufficient in characterizing multi-scale pore structures, particularly lacking systematic validation of the evolution and interrelation of micro–macro pore structures under different sand grain sizes. This study aims to reveal the evolution patterns and spatial distribution characteristics of pore structures in cemented bodies formed in water-rich sand layers with different grain sizes, providing references for understanding grouting mechanisms and selecting engineering parameters. Under consistent grouting materials and injection pressure, simulated grouting tests were conducted on fine, medium, and coarse water-rich sand layers to prepare typical cemented body samples. Micro-scale pore structures were quantitatively analyzed using mercury intrusion porosimetry, while macro-scale pore characteristics were extracted and binarized using MATLAB digital image analysis to calculate porosity. By integrating micro-scale and macro-scale data, a multi-scale pore structure analysis framework was established to systematically compare differences and spatial patterns in the pore structures of cemented bodies across different grain sizes. At the micro-scale, fine cemented bodies are dominated by slit-like and irregular medium-to-large pores, exhibiting high connectivity and the highest porosity; medium cemented bodies show a composite structure of slit-like and spherical pores, with a wide pore size distribution and the most complex structure; coarse cemented bodies mainly develop long columnar or small-to-medium spherical pores, with the lowest porosity, indicating that coarse-grained skeletons favor densification. At the macro-scale, porosity of all three cemented body types increases parabolically with distance from the grout outlet, reaching the minimum at X = 0 cm, with fitting coefficients R² ranging from 0.70 to 0.92, reflecting the spatial characteristics of saturated grout deposition. Micro-scale porosimetry and macro-scale image analysis results were highly consistent, all showing a porosity ranking of “fine > medium > coarse,” validating the reliability of the image analysis method. The study reveals the multi-scale pore structure characteristics and spatial distribution patterns of cemented bodies in water-rich sand layers under different grain size conditions, clarifying the control of grain size on pore morphology, porosity, and densification. The findings provide a scientific basis for understanding grout diffusion and deposition mechanisms, optimizing grouting materials and parameters, and improving reinforcement quality, offering significant engineering applications.

Tongwan City, which is located in Jingbian, Yulin, Shaanxi Province, is the only Xiongnu city site in China, carrying rich historical culture and scientific value. Despite over 1,600 years of weathering and freeze-thaw cycles, the heritage site has been preserved to this day. Therefore, it is important to study the material composition, mechanical properties and microstructure of the site soil for the restoration of heritage site. Taking the site soil at Tongwan City as the research object, this study conducted laboratory tests on physical and mechanical properties, X-ray diffraction(XRD), X-ray fluorescence(XRF) spectroscopy, scanning electron microscope (SEM) and computed tomography (CT) scanning to analyze the macro and micro characteristics of the site soil. Based on the above research, some conclusions are as follows. ① The primary mineral components of the site soil include quartz, feldspar, calcite and dolomite, and its calcium ion content is significantly higher than the surrounding soil samples, this indicates that lime material was intentionally added during the construction of Tongwan City. ② Compared with undisturbed loess in the surrounding area, the site soil has higher shear strength and low compressibility, the shear curve exhibits distinct brittle failure deformation characteristics, and the compression coefficient is smaller. ③ Microstructural analysis reveal that face-to-face contacts dominate the particle interactions in the site soil. Calcium carbonate cement interweaves densely among particles, adhering to particle surfaces and bridging interparticle spaces, which reduces the proportion of macropores, enhances particle interconnections, and increases the overall density of the soil structure.