To investigate the actual working mechanism of anti-slide piles, an integrated monitoring system combining distributed fiber Bragg grating (FBG) sensors and flexible inclinometers was deployed in a highway landslide control project. FBG cables and inclinometer tubes were implanted in one single-row cantilever pile (No.20) and two double-row portal-frame piles (No.48 front-row and No.71 rear-row) with anchor cables, allowing for simultaneous measurement and comparative study of the internal force (bending moment) and deformation (displacement) fields. The results reveal that single-row piles exhibit a tightly coupled internal force-deformation relationship, with coincident bending moment and displacement inflection points. In contrast, double-row piles display a systematic decoupling: peak bending moments shift to greater depth while maximum displacements remain shallow, caused by load redistribution through the capping beam. Safety evaluation shows that the measured maximum bending moments utilize only 7.06%–10.75% of the design capacity, confirming linear elastic behaviour and substantial safety reserves. The study demonstrates the value of multi-source data fusion for structural diagnosis and performance optimization in slope engineering.

Based on a mountainous expressway slope reinforcement project, this paper develops a multi-source three-dimensional monitoring system that includes distributed fiber Bragg grating (FBG) stress monitoring, deep horizontal displacement monitoring with a flexible inclinometer, and tilt monitoring with a wireless inclination sensor. A 2-year joint monitoring of the micropile group-anti-slide pile composite construction in three representative sections was conducted. In conjunction with the field anchor cable tension test, the stress and deformation characteristics, sliding surface distribution, and construction disturbance impact of the micropile group were thoroughly investigated. The micropile group exhibits modest stress levels, with a maximum bending moment of −28.14 kN·m and enough safety reserve. After unloading, the bending moment of the two-section tonne bag changes from positive to negative, demonstrating the anchor cable mechanism’s transition from passive force to active constraint. The anti-slide pile’s bending moment is consistent with the anchoring pile’s properties. The inflection point closely matches the mutation point of the inclinometer displacement and the FBG thrust concentration area. The primary sliding surface is placed between 16 and 20 m, with multi-layer sliding surfaces in three portions. The anchor cable’s tensile additional stress increment accounts for just 1.05%–1.37% of the allowed stress, leaving residual strain after the anchor is withdrawn. The multi-source monitoring data indicate a substantial relationship between sliding surface identification and deformation trends. The crown beam strain and pile top tilt angle are sensitive to rainfall, but they do not exceed the warning level, suggesting that the structure is in elastic functioning condition. The study presents a data-driven analysis approach and measurement basis for evaluating performance, optimizing managing construction of a micropile group composite structure.

This paper addresses the technical problem that prestressed anchor cables on highway slopes often become too short during operation due to steel strand reservation and the failure of traditional compensation tensioning equipment. To solve this issue, a contact mechanics‑based calculation method for slip fixture parameters is proposed. The approach converts the three‑dimensional frictional contact problem into a plane strain problem by equating the discrete slip teeth to an infinite contact body. A friction contact model is developed using Hertz contact theory to predict the total tensile force of the fixture. A yield strength model is established using the Johnson stress solution and the Von Mises yield criterion to assess the yield risk and safety factor of the slip teeth. Systematic parametric numerical analysis is performed to reveal the influence of key geometric factors (slip center distance, contact length, curvature radius) on tension concentration and contact stress. The method is then applied to design a slip clamp for a four‑beam anchor cable on a Guangdong roadway, using 45CrNi alloy steel, and a field compensation tension test is conducted. The field test successfully achieved a tension of 600 kN. The plastic “tooth marks“ and the bearing capacity formed on the anchoring surface agreed well with the theoretical predictions. The close agreement between experimental outcomes and theoretical calculations demonstrates the reliability and engineering practicability of the proposed method. This study provides a systematic solution—from theory to practice—for the core fixture design of compensation tensioning equipment.

Shear failure of rock structural planes, a critical trigger for rock mass instability, is determined by coupled effects of roughness and normal stress. Existing studies have not thoroughly investigated the multiparameter synergistic regulatory mechanism of structural plane shear mechanical signal [acoustic emission (AE)] and failure evolution. This study examines multifactor synergistic control using structural plane shear testing, AE monitoring, and digital image techniques. The results show that AE counts increase linearly with increasing roughness, while AE escalation becomes nonlinear with growing normal stress. The prepeak nonlinear stage has the most AE energy per signal, followed by the linear elastic stage with the lowest. AE energy per signal constantly rises with increasing roughness and normal stress. The duration time per AE signal is greatest in the prepeak nonlinear stage, increasing gradually with increasing roughness; however, the rate of increase slows with increasing normal stress. The b value has an inverse association with normal stress magnitude but has a positive correlation with roughness features. Under low stress and roughness, shear failure is mostly wear-based, with concomitant AE signals manifesting as high-frequency, low-energy events. In contrast, at high stress and roughness levels, gnawing becomes the major failure mechanism, as seen by AE signals with low-frequency, high-energy bursts. These findings reveal that roughness and normal stress collaborate to govern AE signs via interfacial contact mechanics change, and they provide important insights for forecasting shear-induced structural plane failures in rock engineering situations.

With the gradual depletion of shallow geological resources, their development has increased. However, it is difficult to control the stability and bearing capacity of deep-stratum fissure rock bodies under static and dynamic load coupling. To study the relationship between the mechanical properties of anchor-reinforced fissured rock bodies under static and dynamic loading conditions, this study performed a static compression test and dynamic impact test on anchor-reinforced prefabricated fissured red sandstone with different inclination angles. Research has revealed that under static loading conditions, the mechanical properties of anchor-reinforced specimens are stable, and the peak strength fluctuates between 23-27 MPa. Under dynamic loading conditions, the peak strength and deformation decreased with increasing inclination angle. The peak strength decreased from 47.3 MPa at 15 degrees inclination angle to 35.4 MPa at a 90 degrees inclination angle, and the peak strain and dynamic cut line modulus were 1.28 times and 1.23 times of the static loading, respectively. Under static loading, the specimen cracks mainly developed along the prefabricated cracks to shear damage, and the increase in the inclination angle led to the damage spreading to the specimen ends, forming combined tensile-shear damage. Under dynamic loading, the damage was primarily tensile-shear combination damage parallel to the impact direction. Based on the linear uniaxial strength criterion, a new relationship between dynamic peak strength, strain rate, and static peak strength was established, and the correlation coefficients were 0.90-0.98, indicating a good correlation.

Amidst the escalating scarcity of resources and the burgeoning accumulation of construction waste, it is imperative to investigate the performance of carbonized recycled coarse aggregate concrete to enhance the utilization of construction solid waste and advance the adoption of environmentally sustainable low-carbon building materials. In this study, comparative effects of direct carbonation and pre-soaking limewater carbonation on the physical and mechanical properties of the recycled coarse aggregate (RCA) and recycled concrete are systematically analyzed. The carbonation mechanism is elucidated through the water absorption, crushing value, apparent density test, XRD, TG, SEM, and other microscopic characterization techniques. The results indicate that pre-soaking limewater carbonation surpasses direct carbonation, yielding more significant improvements in the water absorption (reduced by 22.9 %), crushing value (reduced by 17.7 %), and apparent density (increased by 4.1 %). These enhancements are attributed to the additional Ca2+ provided by limewater, which facilitates calcium carbonate precipitation to filling pores and optimizing the interface transition zone (ITZ). Regarding recycled concrete performance, the compressive, axial compressive, splitting tensile, and flexural strengths of recycled concrete prepared with pre-soaking limewater carbonized RCA are superior to those of direct carbonation group at both 7 d and 28 d ages, which is more obvious at high replacement rate. The underlying mechanism involves the carbonation products strengthening ITZ bonding and refining pore structure. The study confirms that pre-soaking limewater carbonation is an efficient technology for enhancing the properties of recycled aggregates, providing theoretical support for the development of high-performance and sustainable recycled concrete applications.

The anchor injection joint reinforcement technique effectively deals with fissured rock masses in underground engineering. The current research on the mechanical properties and damage modes of fissured rock mass under static and dynamic loads with combined anchor-injection reinforcement is insufficient. For this reason, the present study adopts the method of combined anchor-injection reinforcement to carry out dynamic and static load tests under three-dimensional stress states on red sandstone masses containing prefabricated fissures to reveal the differences in the mechanical properties of the rock masses under dynamic and static stresses. The test resulted in the following: since the loading rates of the two loading tests and the simulated stress states are different, it leads to differences in the stress–strain curves under static and dynamic loads. Based on the strength evolution characteristics, a power function prediction model is proposed, in which the dynamic peak strength is represented by the static peak strength and strain rate. As the confining pressure increases, the dynamic peak strain decreases, the static peak strain increases, and both the dynamic and static secant modulus increase. The failure mode of the static load test samples is shear damage, and the failure mode of the dynamic load test samples is compression-shear damage.

Structural planes play an important role in controlling the stability of rock engineering, and the influence of structural planes should be considered in the design and construction process of rock engineering. In this paper, mechanical properties, constitutive theory, and numerical application of structural plane are studied by a combination method of laboratory tests, theoretical derivation, and program development. The test results reveal the change laws of various mechanical parameters under different roughness and normal stress. At the pre-peak stage, a non-stationary model of shear stiffness is established, and three-dimensional empirical prediction models for initial shear stiffness and residual stage roughness are proposed. The nonlinear constitutive models are established based on elasto-plastic mechanics, and the algorithms of the models are developed based on the return mapping algorithm. According to a large number of statistical analysis results, empirical prediction models are proposed for model parameters expressed by structural plane characteristic parameters. Finally, the discrete element method (DEM) is chosen to embed the constitutive models for practical application. The running programs of the constitutive models have been compiled into the discrete element model library. The comparison results between the proposed model and the Mohr-Coulomb slip model show that the proposed model can better describe nonlinear changes at different stages, and the predicted shear strength, peak strain and shear stiffness are closer to the test results. The research results of the paper are conducive to the accurate evaluation of structural plane in rock engineering.

Autoclaved aerated concrete (AAC) is widely used for its lightweight, high thermal insulation, and superior machinability. However, its loose and porous microstructure can cause a significant decrease in compressive strength after carbonation and the mechanism of the deterioration remains uncertain. This study delved into the alteration trends of AAC's compressive strength and dry density within carbonation environments. Additionally, a variety of testing techniques were employed to elucidate the microscopic mechanisms. The results showed that when the calcium/silicon ratio (Ca/Si ratio) stood at 0.75, AAC exhibited its highest degree of resistance against carbonation. Microscopic analysis revealed a progression in hydration product characteristics as the Ca/Si ratio increased. The transformation journey encompassed a shift from the initial structure to a needle-like tobermorite configuration and, subsequently, to a flaky structure. The study offers invaluable insights that furnish guidance for enhancing the durability of AAC and broaden the horizons of its potential applications.

With the development of underground engineering, dynamic disasters, such as rock bursts, are becoming increasingly serious. Bolt-grouting combined support is one of the common support methods, aiming at the prevention and control of dynamic disasters in fractured surrounding rock of underground engineering. However, the design of bolt-grouting supports is based mainly on experience, and the antishock characteristics need further study for fractured rock masses reinforced by bolt-grouting, which provides a scientific basis for the design of surrounding rock roadway reinforcement. Therefore, we carried out an experimental study on the dynamic mechanical properties of bolted and grouted red sandstones containing prefabricated fractures with different dip angles. The test results show that the dynamic peak strength and the deformation capacity decrease with increasing of fracture dip angle. Compared with the unreinforced samples, the dynamic peak strength and dynamic peak strain of bolt and grouting reinforced samples are improved, and the reinforced rock samples have higher impact resistance and deformation capacity. As the fracture dip angle increases, the incident energy, reflection energy, and transmission energy all show a decreasing trend. Bolt and grouting play the role of energy absorption and increasing antishock, and the dissipation rate of bolted-grouted rock samples is improved. The failure mode of the unreinforced samples is shear failure, the damage of which is more severe than that of bolt and grouting reinforced samples. For the bolt-grouting samples, tensile failure is observed at a low strain rate, and shear failure occurred at a high strain rate.

The nonlinear constitutive model of the structural plane is very important for the stability evaluation of the geotechnical engineering, and is also the key to the accuracy of the numerical analysis. In this paper, the shear tests are carried out under different roughness and normal stress, and the change laws of the mechanical properties are revealed under the influence of two factors. The relationship equations, with the normal stress (σn) and the roughness (JRC), are established for various mechanical parameters. Then, on the basis of the statistical damage mechanics, the shear damage nonlinear constitutive model is established, and the accuracy and practicability are verified by different shear test results. The empirical relationships are established for the model parameters (a and r) with the normal stress, roughness and rock wall strength (JCS), by the multi-factor optimization analysis method. Finally, the discrete element is selected, and the C++ is used to compile the running program of the constitutive model to realize numerical application. Different numerically simulated shear tests are carried out to verify the feasibility of the numerical application. The research results are beneficial for the stability evaluation in the geotechnical engineering.

As a common geological structure, rock joints have a great influence on the mechanical properties and stability of rock mass engineering. The shear constitutive model of the rock joint and its calculation methods have played an important role in theoretical and experimental research. Most of the existing elastic–plastic shear constitutive models of the rock joint are simplified to linear form or only considering hardening behavior, while the shear test results show that the post-peak nonlinear softening curve is the most common form for shear curves. Therefore, based on Barton shear strength criterion, the shear stress softening is characterized by the change of the post-peak joint roughness coefficient (JRC), and an increment elastic–plastic constitutive model reflecting the shear stress softening is established. According to the constraint condition of constant normal stress, the increment model of the normal deformation with shear deformation is obtained. Based on principle of the implicit return mapping algorithm, an algorithm for the shear softening elastic–plastic constitutive model in the stress space is established. The applicability and rationality of the model and algorithm are verified by a large number of the joint shear experiment results under different conditions. The established elastic–plastic constitutive model provides an effective reference for correctly evaluating the shear deformation characteristics of the joint.

Creep characteristics of rock mass are related not only to the confining pressure but also to the degree of internal fracture damage. Revealing the creep characteristics of rock mass under different confining pressures and degrees of damage is of great significance for selecting a reasonable supporting time and optimum supporting strategy in engineering. Sandstone is the main medium of the coal seam roof in the Jushan Mine and has poor physical and mechanical properties. To study the creep behavior of sandstone, triaxial creep tests and simulations are conducted under different confining pressures and degrees of damage. The results show that the appearance of the creep stage is related not only to the stress but also to the confining pressure and the degree of damage. With an increase in the confining pressure or the degree of damage, the creep parameters will have clear change, especially under high stress level. The creep parameters and confining pressures show different changing laws, and there are also different relationships between the creep parameters and the degrees of damage. Three surface equations are proposed to visually describe the variation in the creep parameters with the confining pressure and the degree of damage. The sudden increase in cracks is affected by both the confining pressure and the degree of damage, and it can be used as an early warning of rock failure. Thus, the influence of the confining pressure and damage should be simultaneously considered in the long-term stability of rock mass.

The description of rock creep by existing rheological models mainly focuses on the first two stages of creep. However, the description of the accelerated creep stage is rare, which is contrary to the common study of soft rock failure in engineering applications. Therefore, the study of the accelerated creep stage is an important research direction at present. In this paper, a new model that can describe accelerated creep is proposed on the basis of the Nishihara model, and creep constitutive relation of the model is deduced via relevant laws. The parameters of the model are obtained by the whole rheological curves of the sandy mudstone of the diversion tunnel of a hydropower station and the strongly weathered sandstone in the bottom of the Xiangjiaba dam foundation. A fitting analysis of the theoretical results and experimental data indicates that the fitting results are highly consistent; the correlation coefficients are all above 0.98, which shows the rationality and correctness of the model. The nonlinear viscoelastic-plastic model proposed in this paper can accurately describe the accelerated creep stage of rock, and its applicability is obviously broader than that of the traditional Nishihara model. This nonlinear viscoelastic-plastic model can be used to not only predict the critical sliding of a rock mass in slope, tunnel and hydraulic engineering but also enrich the theory of rock rheology.

Taking the concrete as an example, this paper studies the shear characteristics of the cohesive soil and rigid base. A series of shear tests are conducted by the refitted DSJ-2 electric four-joint equal stress direct shear apparatus. The results in the shear tests are contrastively analyzed. The results show that under the condition of simple shear tests, the constitutive relation of structural interface between the clay and concrete is rigid, and the residual strength is obvious. Under the condition of direct shear tests, the shear stress-displacement curves present hyperbolic connection. There is obvious strain hardening phenomenon, no obvious peak strength and residual strength. Under the two experimental conditions, the peak shear strength of the interface increases with an increase in the normal stress. With increasing moisture content, the peak shear strength of the interface decreases. The internal friction angle and cohesion of the structural interface decrease with increasing moisture content, and the relationship between internal friction angle, cohesion of the structural interface and moisture content are nonlinear. The peak shear strength of the direct shear tests is greater than that of the simple shear tests.

To reflect the influence of saturation effect, an improved strain-softening damage model is established to link the saturated rocks with the dry rocks. First, the original damage model is improved to describe the characteristics of each stage in the uniaxial compression. According to the change of the tangent modulus from the compression phase to the elastic stage, an improved strain-softening constitutive model reflecting the nonlinear change characteristics of the compression phase is established. According to the change of the energy during the uniaxial compression, the energy consumption coefficient (λ) is introduced to replace the damage ratio coefficient to describe the deformation characteristics of the rocks when the residual stress or failure is reached. The specific physical meaning and calculation method of the energy consumption coefficient are given to correct the shortcomings of the damage evolution in the original model. Then, the relationship between the parameters in the new model for the dry rocks and the saturated rocks is analyzed. Based on the constitutive model of the dry rocks, a new constitutive model which can reflect the influence of the water-weakening is established. Finally, the stress–strain curves of different rocks are fitted by the established model, and good results are obtained. The physical meaning of each parameter in the model is clear, and each parameter can be obtained by the test results. The improved constitutive model can be applicable to both the dry rocks and the saturated rocks.

To ensure the safe and effective application of deep geotechnical engineering, it is necessary to establish a suitable constitutive model of the rocks in thermal environment, including geothermal energy mining, and deep geological treatment of nuclear waste and tunnel fire. A strain-softening damage model of the rocks with defect growth is established based on damage evolution. According to the change in the tangent modulus from the compression phase to the elastic stage, we established a constitutive model reflecting the nonlinearity characteristics of the compression phase. According to the change in the energy conversion, the energy consumption coefficient is introduced to describe the deformation characteristics of the rocks when the residual stress is reached. The specific physical meaning and the calculation method of the energy consumption coefficient are given to correct the shortcomings of the evolution of the damage variable. We then analyzed the relationship between parameters in the constitutive model of the rocks at high temperature and normal temperature. Based on the constitutive model of the rocks at normal temperature, we established a constitutive model reflecting the influence of high temperature. Finally, the established model fit the stress-strain curves of several kinds of the rocks at different temperatures and generated desired results. The established model can be used to describe the stress-strain curve characteristics of the rocks at different temperatures.

The experimental results show that the creep properties of the rocks are affected by the initial damage, and the damage evolution also has a significant impact on the time-dependent properties of the rocks during the creep. However, the effects of the initial damage and the damage evolution are seldom considered in the current study of the rocks' creep models. In this paper, a new nonlinear creep damage model is proposed based on the multistage creep test results of the sandstones with different damage degrees. The new nonlinear creep damage model is improved based on the Nishihara model. The influences of the initial damage and the damage evolution on the components in the Nishihara model are considered. The creep damage model can not only describe the changes in three creep stages, namely, the primary creep, the secondary creep, and the tertiary creep, but also reflect the influence of the initial damage and the damage evolution on creep failure. The nonlinear least squares method is used to determine the parameters in the nonlinear creep damage model. The consistency between the experimental data and the predicted results indicates the applicability of the nonlinear damage model to accurately predict the creep deformation of the rocks with initial damage.

The mechanical properties of rocks are greatly affected by water action. Many underground structures can be failed by changes in the water environment. To reveal the mechanical properties of the rocks after saturation, a series of saturated sandstones are prepared to study the changes in the mechanical properties during post-peak cyclic loading and unloading. The results show that the strength characteristics of the sandstones decrease after saturation. There is an exponential function between the peak strength and the damage degree and between the crack damage stress and the damage degree. A new method for calculating the elastic modulus is proposed. The results of both calculation methods show that the elastic modulus of the saturated sandstones decreases. The relationship between the elastic modulus obtained by the two methods and the damage degree is quite different. After saturation, the dilatancy of the sandstones increases in the post-peak stage. The volumetric strain, the plastic shear strain, and the peak dilatancy angle all increase with increasing damage degree. Because of the filling by water molecules, the P-wave velocity increases. There is an exponential function relationship between the P-wave velocity and the damage degree. Because of the softening after saturation, more macroscopic failure cracks and fracture surfaces will be formed in the saturated sandstones. The research results of this paper can provide some guidance for excavation and engineering design in water-rich rock.