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Deep cement mixing piles are a key technology for treating settlement distress of soft soil subgrade. However, it is very challenging to accurately evaluate the quality of pile construction due to the limitations of pile material, large number of piles and small pile spacing. Here, we propose the idea of transforming defect detection of piles into quality evaluation of ground improvement. Geological models of pile group reinforced subgrade are constructed and their ground-penetrating radar response characteristics are revealed. We have also developed ground-penetrating radar attribute analysis technology and established ground-penetrating radar technical system for evaluating the quality of ground improvement. We further prove that the ground-penetrating radar results integrating single-channel waveform, multi-channel section and attributes can effectively detect the defects and stratum structure after ground improvement. Our research results provide a rapid, efficient and economic technical solution for the quality evaluation of ground improvement in soft soil subgrade reinforcement engineering. Subgrade settlement is a serious distress which poses a huge threat to the service life and operation safety of roads. Here, authors propose the application of ground-penetrating radar as technical solution for the quality evaluation of ground improvement in soft soil subgrade reinforcement engineering.

Loess slopes with steep gradients are particularly prone to vertical tension cracks at the crest, resulting from unloading and other factors. These cracks significantly affect the spatiotemporal distribution of moisture infiltration during rainfall, potentially leading to slope instability. This study investigates the impact of crest-tension cracks on moisture infiltration in loess slopes under extreme rainfall conditions, focusing on crack position, depth, and width. Soil moisture content and the dynamics of wetting fronts were monitored to assess how these tension cracks influence infiltration patterns. The results indicate that tension cracks at the slope crest act as preferential infiltration pathways, causing water retention within the cracks and forming a “U-shaped” preferential infiltration zone. The extent of this “U-shaped” wetting front is influenced by the crack’s width, depth, and proximity to the slope shoulder; wider, deeper cracks closer to the shoulder result in a more pronounced wetting front. Over time, as rainfall persists, the influence of preferential infiltration decreases, and the infiltration patterns of slopes with crest cracks begin to resemble those of homogeneous slopes. In both cases, wetting fronts exhibit intersecting patterns: one parallel to the slope crest and the other parallel to the slope surface. During the initial stages of rainfall, the migration speed of wetting fronts in slopes with crest-tension cracks was significantly higher than in homogeneous slopes. However, after prolonged rainfall, the migration speeds of wetting fronts in both scenarios converged. A strong linear correlation was observed between the average migration depth of the horizontal wetting front at the slope crest and the parallel wetting front on the slope surface, for both slope types. These findings deepen our understanding of moisture migration dynamics in loess slopes with crest-tension cracks, providing insights for developing effective slope hazard mitigation strategies.

The instability of slope blocks occurred frequently along traffic corridor in Southeastern Tibet (TCST), which was primarily controlled by the rock mass structures. A rapid method evaluating the control effects of rock mass structures was proposed through field statistics of the slopes and rock mass structures along TCST, which combined the stereographic projection method, modified M-JCS model, and limit equilibrium theory. The instabilities of slope blocks along TCST were then evaluated rapidly, and the different control factors of instability were analyzed. Results showed that the probabilities of toppling (5.31%), planar (16.15%), and wedge (35.37%) failure of slope blocks along TCST increased sequentially. These instability modes were respectively controlled by the anti-dip joint, the joint parallel to slope surface with a dip angle smaller than the slope angle (single-joint), and two groups of joints inclined out of the slope (double-joints). Regarding the control effects on slope block instability, the stabilization ability of double-joints (72.7%), anti-dip joint (67.4%), and single-joint (57.6%) decreased sequentially, resulting in different probabilities of slope block instability. Additionally, nearby regional faults significantly influenced the joints, leading to spatial heterogeneity and segmental clustering in the stabilization ability provided by joints to the slope blocks. Consequently, the stability of slope blocks gradually weakened as they approached the fault zones. This paper can provide guidance and assistance for investigating the development characteristics of rock mass structures and the stability of slope blocks.

The paper presents field pull-out tests on reinforcement anti-floating anchor rods for the jet grouting process and investigates the load transfer behavior of these anchor rods under this technique. A comparative study was conducted using field pull-out tests on reinforcement anti-floating anchor rods with the grouting process, revealing the differences in load transfer behavior between the two techniques. The results indicate that reinforcement anti-floating anchor rods formed by the jet grouting process exhibit superior bond strength at the mudstone interface and load transfer performance compared to the grouting process. Based on the ABAQUS finite element simulation software, a finite element simulation method for jet grouting expansion anchor rods was proposed and validated through experimental results. Additionally, the parameter analysis indicates that increasing the tensile strength of the anchor rod raises the ultimate bond strength by approximately 25% per 100 MPa, while increasing the anchorage depth beyond 9.5 m yields diminishing improvements in bearing capacity but reduces ultimate displacement significantly.

The long-term safety and durability of anchor systems are the focus of slope maintenance management and sustainable operation. This study presents the observed temperature, humidity, and anchor bolt stress at varying depths from four-year remote real-time monitoring of the selected loess highway cut-slope. The potential correlation between slope hydrothermal environment and anchor stress is analyzed. The anchor serviceability and durability were evaluated by establishing a time-dependent mathematical model of axial forces. The results show that the slope shallow loess exhibited hydro-thermal fluctuations annually during operation, subjecting the loess to continuous dry–wet cycles. Soil elastic deformation induces anchor axial force fluctuations due to hydro-thermo effects, while damage creep leads to the annual increase in axial force peaks and valleys. The increase in axial force is more significant at the upper slope and lower slope, thereby increasing the risk of retrogressive landslides in loess slopes. The time-dependent model of anchor axial force composing negative exponential and sine functions was proposed. The cyclic amplitudes, lower limits, and periods of temperature and humidity in slope can determine the model coefficients. The development patterns of axial force are classified into stable type, slow growth type, and accelerated growth type according to the characteristics of the model coefficients. Predicted results indicate that the anchor axial forces are lower than the landslide threshold within 30 years of slope operation, ensuring long safety and serviceability. Results provide a reference for the long-term safety evaluation and formulation of maintenance plans for loess slopes reinforced by anchor systems.

In order to explore the fracture mechanism of jointed Phyllite, the TAJW-2000 rock mechanics test system is used to carry out uniaxial compression tests on different joint inclination Phyllites. The influence of joint inclination of Phyllite failure mode is discussed, and the progressive failure process of Phyllite is studied. The test results show that the uniaxial compressive strength anisotropy of jointed Phyllite is remarkable. As the inclination increases, it exhibits a U-shaped change; When 30° ≤ α ≤ 75°, the tensile and shear failures along the joint inclination mainly occurs. the joint inclination controls the failure surface form of the Phyllite; The crack initial stress level of the joint Phyllite is 0.30–0.59σf, the crack failure stress level is 0.44–0.86σf. When α = 90°, the σ cd value is the largest, and σ cd with α = 90° can be used as the maximum reliable value of uniaxial compressive strength of Phyllite. Using the theory of fracture mechanics, it is analyzed that under uniaxial compression of the rock, the crack does not break along the original crack direction, but extends along the direction at a certain angle to the original crack. The joint effect coefficient is proposed to show the influence of the joint inclination on the uniaxial compressive strength of the phyllite. Both the test and simulation results show that when the joint inclination is 60°, the joint effect coefficient is the largest. The compressive strength is the smallest. Numerical simulation analyses the crack evolution law of phyllite under different joint inclination under uniaxial compression, which verifies that there are different failure modes of joint phyllite under uniaxial compression.

Research on monitoring and forecasting technology for slope stability is important for ensuring railway operation. This paper presents field investigation of force and displacement within a strata slope using a real-time remote monitoring system. Based on the interactions of the landslide body, the landslide bed and the monitoring anchor of slope, the mechanical principle of relative movement between the landslide body and the landslide bed can be found. This paper puts forward stress data obtained from a monitoring anchor as the main criterion for landslide stability. The stress will change continually inside the slope mass before the occurrence of a landslide. When the sliding force is larger than the anti-sliding force, deformation and landslides will occur; thus, the change in stress occurs before the change in displacement. In this study, the internal stress, deep displacement and surface strain of a railway slope were measured by a real-time remote-monitoring system, and a vibration metre was installed on the surface of the railway slope to study the influence of the train vibration load on the stability of the slope. The monitoring results are synthetically analysed temporally and spatially, then a railway slope forecasting model is proposed. According to the railway slope field application, the forecasting model makes successful predictions.

During the construction of tunnels in the central and western regions of China, diorite is frequently affected by vibration, blasting and water which will lead to the questions of the quality and operational safety of project. However, there are few studies on the dynamic characteristics of diorite under the action of dry–wet cycles. Therefore, this paper selected the gray–green altered diorite from Ning shan County, Shaanxi Province, China, mainly composed of plagioclase, and used the Slit Hopkinson pressure bar (SHPB) to study the effect of dry–wet cycle on the dynamic characteristics of Diorite. The test results show that the strength decay rate of the peak strength of diorite is the maximum under 1–3 dry–wet cycles, then decreases gradually. The dynamic elastic modulus of diorite dropped by 35.02% after three dry–wet cycles, accounting for 98.45% of the total attenuation. Compared the test result of three dry–wet cycles, the decrease volumes of the stress growth rate of diorite are the largest after six dry–wet cycles. Because of the actions of the dry–wet cycles, the growth rate of the rapid growth stage of the reflected energy–time history curve reduces and the growth rate of the rapid growth stage of the transmitted energy–time history curve improves. Under the action of the dry–wet cycles, the dissipation energy ratio gradually decreases, and the decrease of energy consumption density follows a negative exponential function relationship. Under the action of multiple dry–wet cycles, the tension and compression stress frequently change between the particles of rock, resulting in a significant increase of micro-cracks and an obvious degradation effect on the dynamical properties of diorite.

Check dams are widely used for debris flow disaster mitigation, but their sediment-trapping effectiveness diminishes with multiple debris flow events. Exploring the evolution of the sediment-trapping ratio is crucial for planning check dam maintenance. This study uses physical model experiments to investigate how dam openings and sediment concentration (C v) affect this evolution. Results show that the sediment-trapping process of slit dams involves two phases: a slit-blocking controlled phase where the sediment-trapping ratio slightly increases, and a reservoir-filling controlled phase where it gradually decreases. The transition between these two phases occurs when the reservoir-filling ratio reaches 1.0–2.0. For solid-body dams, the slit-blocking phase is absent, and the sediment-trapping effectiveness is mainly controlled by the reservoir-filling state. The sediment-trapping ratio shows a linear negative correlation with the reservoir-filling ratio, and the correlation strengthens with increasing C v. Additionally, under the combined influence of debris flow dynamics (flow depth and Froude number) and rheological properties of the deposited sediment (excess pore water pressure dissipation), the average sediment-trapping ratio first increases then decreases with C v, peaking around C v = 0.3. Finally, we propose a conceptual model for the evolution of the sediment-trapping ratio under various check dam opening conditions.

Compared with plain soil, polypropylene (PP) fiber-reinforced soil has markedly improved mechanical properties and can be used in slope protection projects. To investigate the reduction law of the antierosion ability parameters of PP fiber-reinforced loess under dry-wet (D-W) cycles and freeze-thaw (F-T) cycles, we took loess from Yan’an, China, mixed them with PP fiber, and did shear strength tests, disintegration tests, and permeability tests under D-W cycles and F-T cycles. The experimental results show that D-W cycles or F-T  cycles had a less deteriorating effect on the cohesion, disintegration rate, and permeability coefficient of the fiber-reinforced samples than on plain loess; however, the reduction in their internal friction angle was more obvious. Under D-W cycles or F-T cycles, the cohesion and internal friction angle of the reinforced soil decreased as the number of cycles increased, while the disintegration rate and permeability coefficient increased as the number of cycles increased. The relation between the reduction in the antierosion ability parameters of reinforced soil and the number of D-W cycles or F-T cycles accorded with the hyperbolic function fitting results. The most obvious reduction effect the D-W cycles had on the reinforced soil was on the disintegration rate, followed by cohesion, internal friction angle, and permeability coefficient. The most obvious effect of F-T cycles was also on the disintegration rate, followed by cohesion, permeability coefficient, and internal friction angle. Compared with D-W cycles, F-T cycles had a stronger effect on the reduction in the cohesion, disintegration rate, and permeability coefficient of reinforced soil, but the reduction in the friction angle was greater in D-W cycles.