International Journal of Geomechanics

Based on conventional triaxial compression tests, the influence of joint inclination (α) and opening width (t) on rock strength, deformation, and failure mode will be analyzed. Combining particle flow discrete–element (PFD) analysis, the fracture mechanism of jointed rock will be further investigated from the perspectives of microscopic crack evolution and energy conversion. The results show that as α increased, its peak strength (σ_c) presented a U-shaped change of first a decrease and then an increase, and it reached a minimum at approximately 60°, and its elastic modulus (E) exhibited an approximately linear monotonic increasing trend, and the ability to resist deformation gradually increased. For joint specimens with different opening widths, the strength and E exhibited similar evolution, and both decreased with the increase in opening width. As α increased, the failure mode changed from single inclined plane shear failure to an X-shaped conjugate inclined plane shear failure, and the increase in t resulted in a wider fracture zone. During rock failure, the number of microcracks accumulated in an S-shape, and its mutation point was consistent with the elastic, plastic, and failure characteristic points of the stress–strain curve. As the α angle enlarged, the external driving energy (E_w) first decreased and then increased, the ratio of dissipated energy (E_d) to E_w (E_d/E_w) decreased and tended to become stable. In triaxial compression, the frictional energy consumption of the microstructure surface accounted for ≤5%–20% of the total input energy, which indicated it should be considered during the analysis of fractures.

The gradual accumulation of permanent deformation in unbound granular material layers is one of the main reasons for flexible pavement rutting. The accurate determination of permanent deformation behavior in pavement materials is critical for the successful design of pavement systems. However, predicting the permanent deformation is complex, and the available empirical regression models have limited accuracy and applicability. In this study, multistage repeated load triaxial tests were carried out under different stress levels in order to evaluate the permanent strain and shakedown ranges of crushed waste rock. The plastic shakedown limit and plastic creep limit were determined so as to estimate the shakedown range of crushed waste rock under certain stress conditions. The Rahman and Erlingsson model (extended using a time-hardening approach) performed better than other models at fitting the accumulated permanent strains (R² > 0.92), although the prediction accuracy of the shakedown range was relatively low (<85%). An artificial neural network (ANN) model was therefore developed, based on the experimental results, to predict the permanent strain of crushed waste rock. The ANN model consisted of three hidden layers (50 neurons per layer) with Tanh activation function and could predict the permanent strain (R² > 0.97) and shakedown ranges (accuracy >93%) satisfactorily.

This paper aims to compare the dynamic response of the vertical pile group (VPG) and batter pile group (BPG) subjected to machine-induced-type loading. For this purpose, an experimental investigation is carried out on a 2 × 2 VPG and a 2 × 2 BPG subjected to horizontal excitation for four different eccentric moments (W · e = 0.225, 0.885, 1.454, and 1.944 N · m) under the static loads (W_s) of 12 and 14 kN. The batter piles in the BPG are inclined at an angle of 20° with the vertical in a unilateral direction. The piles used are 3.3-m-long driven steel pipes with an outer diameter of 0.114 m and thickness of 3 mm and 3d spacing (center to center) between the piles. The comparison in the dynamic behavior of VPG and BPG depends on the dynamic test results, which include the frequency–amplitude response, soil–pile separation length, and distribution of the dynamic bending moment. The test results show that the resonant frequencies of the BPG are higher, whereas the resonant amplitudes are lower when compared with the VPG. Moreover, the influence of the loading direction regarding the batter pile inclination is also evaluated, and the results show the difference in the dynamic behavior as a consequence of unilateral inclination of the batter piles. The soil–pile separation length estimated is less in BPG compared to that in VPG. The result also shows that the magnitude of the maximum dynamic bending moment of BPG is lower than that of VPG. The frequency–amplitude responses from the field tests were compared with the theoretical prediction based on the continuum approach and superposition method. It is found that the theoretical analysis with precise boundary zone parameters predicted the dynamic response of both the pile groups reasonably well in comparison to the dynamic field test results. Furthermore, the study highlights the normalized plots on the effect of pile batter angle and loading direction on the resonant frequency and resonant amplitude based on the theoretical and experimental study.

The stability of coal–rock composite structures is essential for the safety of coal mine production. To explore the failure characteristics and energy evolution law of coal–rock composite structures, uniaxial cyclic loading–unloading tests of gypsum–rock combination specimens are conducted. Test results show that the peak stress and elastic modulus of combination specimens increase linearly with increasing the rock strength, as well as the failure intensity. When the rock strength increases, the energy accumulation rate of a combination specimen decreases, but the total accumulated energy increases before the prepeak stress. The energy evolution processes of rock component and gypsum component are similar to the combination specimen. During the loading process, the energy stored in the rock is low due to the small deformation, but the energy stored in the gypsum is high due to the large deformation, which is almost equal to the combination specimen. Finally, the energy-driven failure mechanism of the coal–rock composite structure is revealed as, in the failure process of the composite structure, the coal will fail first and release elastic strain energy, accompanied with the release of the elastic strain energy of the rock. The energy released by the rock will compensate the coal, which can intensify the coal failure.

This paper presents a comprehensive study on the effect of spatial variability of the elastic modulus on vertical stress distribution in an elastic half-space due to strip loading. The modulus of elasticity is considered as a random variable which follows a log-normal probability distribution. A random field theory based on a Cholesky decomposition technique is used to generate a two-dimensional random field in the elastic half-space. Monte Carlo simulation is performed to generate various random fields with spatially varying elastic modulus. A two-dimensional random finite-element model is developed for a strip loading on an elastic half-space by coupling the random fields generated by Monte Carlo simulation with finite-element analysis. A detailed investigation of the effect of statistical variables defining spatial random variation of the elastic modulus on the vertical stress distribution and the settlement analysis in random elastic half-space is performed. The present study indicates that the spatial random variation of elastic modulus of the soil has a significant effect on the vertical stress distribution and the settlement analysis in the elastic half-space.

The load-transfer mechanism of tensioned anchors is primarily concerned with in-service performance, which depends on the bond–slip behavior of anchoring interface. Because the interface bond–slip behavior is conventionally modeled using epistemic experience of specific researchers and/or back analysis of specific in situ testing results, it is challenging to develop a straightforward load-transfer analysis with extensive applicability. A generalized load-transfer modeling framework was implemented in this work by incorporating a versatile interface bond–slip model that can be derived from experimental characterization of respective types of element-anchoring interface. The adhesion and friction were modeled with interface slip to constitute the interface bond using rational and exponential functions, respectively. The pullout tests on element-scale and large-scale specimens of a typical anchor type (i.e., tensioned steel tube embedded in cemented soils) were carried out to calibrate the parameters of the interface model and to validate the predicting capability of the modeling framework, respectively. In addition, the versatility of this load-transfer modeling framework was examined for two other anchor types reported in the literature (i.e., tensioned rock anchor and tensioned GFRP anchor embedded in sands). The consistent good agreements between predictions and measurements of these anchor types verified the effectiveness and applicability of the generalized load-transfer modeling framework. Based on the load-transfer analysis for the tensioned steel tube in model testing, a parametric study was performed to investigate the impact of axial stiffness and bond length on load-transfer responses of the tensioned anchor.

Advanced constitutive models require several input parameters, some of which represent intrinsic soil properties and some mathematical fitting parameters. Calibrating these modeling parameters is often a challenging component of using a constitutive model in numerical analyses, especially when models are to be calibrated against several data sets simultaneously and/or when there is no conventional geotechnical relation for some parameters. The calibration of constitutive models for cyclic loading is an even more challenging task compared with monotonic loading due to the nonlinearity of soil behavior with stress/strain reversals, amplitude, and the number of loading cycles. In this study, the efficiency of the Gauss–Newton trust-region optimization (GNO) algorithm for calibrating constitutive models for cyclic behavior is evaluated by applying it to three recently developed advanced bounding surface plasticity constitutive models for clays and sands and comparing the outcomes with laboratory test results. The GNO algorithm is shown to be an accurate and time-efficient alternative tool for calibrating the cyclic constitutive models studied.

Rockfill strength parameters are important indicators of the stability of a rockfill dam slope. Therefore, a rational representation of the distribution characteristics of these parameters is extremely important to accurately assess the stability of the dynamic response and reliability of the three-dimensional (3D) slope of a rockfill dam. A joint distribution model of the rockfill strength parameters is constructed in this study using the copula function. In addition, a dynamic reliability analysis method for slope stability is proposed using a number-theoretical method and the generalized probability density evolution method (GPDEM). First, the method is validated by comparing the results for a numerical example with those obtained by Monte Carlo simulation (MCS). Second, the traditional and proposed joint distribution models are comparatively analyzed in terms of the dynamic response and reliability. Finally, the effect of the type of copula function on the dynamic reliability of the slope is investigated. The results show that the copula theory, the number-theoretical method, and the GPDEM provide an effective approach to analyze the dynamic response and reliability of slope stability. The randomness of rockfill strength parameters is sensitive to the safety factor of the slope stability of rockfill dams. The reliability analysis method can reasonably characterize the influence of strength parameter uncertainty on dam slope stability, which makes up for the deficiency of using a single safety measurement standard in the deterministic analysis method. The copula function can reasonably characterize the nonnormal distribution characteristics of rockfill strength parameters, improve the calculation accuracy of the slope stability reliability of rockfill dams, and provide an important scientific basis for the accurate safety assessment of dam slope stability. The type of copula function has an important impact on the dynamic reliability results for slope stability. Thus, it is extremely important to build a joint distribution model of rockfill strength parameters based on a rational selection of the optimal copula function.

In the present study, a new method for designing the cantilever sheet pile wall having a strip load present on the backfill is proposed in cohesionless soil. The method uses the limit-equilibrium approach by establishing the partial mobilized earth pressure diagram in static and seismic conditions. The partial mobilization of earth pressure has been taken as a function of amount and type of wall movement and associated mobilized soil–wall friction angles. Analytical expressions are derived for the cantilever sheet pile wall to determine the earth pressure, shear force, and bending moment. It is observed that the earth pressure diagram of cantilever sheet pile walls varies with the displacement at the dredge level. Furthermore, the shifting of strip load of magnitude 20 kPa away from the cantilever sheet pile walls reduces the maximum bending moment by 10% when the width of the strip load is 1.6 m. A parametric study is carried out and presented in the nondimensionalized form of bending moment, penetration depth, and location of the pivot point. The results of the present study are compared with the existing conventional solutions available in the literature.

A better understanding of the interaction between shield supports, roof, and coal strata, along with the prediction of roof deformation and caving behavior is essential for successful longwall mining operations. The stability of a longwall face can be improved by caving of the roof strata, which can lead to decreasing the load on the powered supports and the magnitude of stress on the abutment pillar of the longwall face. This paper presents the application of the synthetic rock mass (SRM) numerical modeling approach for the simulation of the roof caving mechanism and the load on shield supports in a longwall coal mine in Iran. Using geological and geotechnical data from the mine, a two-dimensional SRM, based on the incorporation of a discrete fracture network into a bonded particle model, was used to simulate the coal seam and the jointed roof strata. The results of the numerical models were validated by comparing the span of first caving, caving height, and load on the support shields to field measurements, observations, and previous studies. The proposed numerical approach can be utilized as a reliable tool in the design and safe operation of a longwall panel with a better understanding of the caved, damaged, and deformed zones above it.

Stiffened deep cement mixing (SDCM) piles have been applied in practice for decades. The bearing capacity of this kind of pile is closely related to the compaction and expansion of the deep cement mixing (DCM) pile and surrounding soil during penetration of the core pile. However, studies on driving behavior are scarce in the literature. Two sets of laboratory model tests will be conducted to facilitate the understanding of the response of an SDCM pile. The penetration depth of the core pile and the excess pore water pressure of the surrounding soil will be monitored using a string potentiometer and pore pressure transducers (PPTs). Diameter changes in the DCM pile before and after penetration of the core pile will be analyzed. Unconfined compressive strength (UCS) tests will be performed to investigate the mechanical properties of cement-treated soil with different densities. The results show that the excess pore water pressure of the surrounding soil increased during penetration of the core pile until the end of the core pile reached the depth of that position. The radius of influence was <7.90 times the diameter of the core pile. The normalized diameter of the DCM pile by its original diameter after penetration of the core pile was <1.05 at a depth of two times the core pile diameter below the end of the core pile, which indicated that the expansion effect that was caused by the penetration of the core pile was insignificant below that depth. In addition, the UCS and elastic modulus of the cement-treated soil increased linearly with density and the peak strain decreased.

The sliding block model is widely used to evaluate the stability of slopes under earthquakes. In this model, the horizontal ground motion is usually applied to the parallel to the slope, whereas the vertical ground motion is commonly ignored. This study investigated the effects of different excitation-applied methods (EAMs) on slope permanent displacements (PDs) using a general sliding block model. For this purpose, three types of ground motion records selected from the NGA-West2 database were applied with six different EAMs to a series of gentle/steep slope sliding systems whose critical accelerations a_c ranges from 0.01 to 0.40g. Comparison of the PDs obtained from the two-dimensional (2D) EAM and the other five systems reveal the following: (1) the common practice of applying a one-dimensional (1D) input motion excessively underestimates the PDs of sliding systems, particularly for those with large slope angles and large critical accelerations; and (2) the effects of the vertical component on the arithmetic mean of PDs are ignorable although the impact can reach several times for some cases in which the slopes are located in near-fault areas and affected by pulse-like ground motions. Besides, it is demonstrated in this study that applying the horizontal and vertical base motions simultaneously to the slope can be the most suitable excitation-applied manner for seismic slope stability analysis in the near-fault zone.

A stiffened deep cement mixing (SDCM) pile is a type of composite pile that has a rigid pile at the core that reinforces the deep cement mixing (DCM) pile. An SDCM pile combines the advantages of both a DCM pile (i.e., high lateral friction resistance) and a rigid pile (i.e., high stiffness and strength). This work presents four sets of laboratory model tests that were aimed at investigating the vertical bearing capacity of SDCM piles with different cement contents by monitoring the pile top load, the axial force, the pile settlement, and the pile end resistance. Two failure modes of the SDCM piles were observed during the tests––pile failure (the pile ruptured at the section below the core pile) and punching failure (the pile penetrated into the underlying soil). It was found that the vertical bearing capacity of the SDCM piles increased with cement content, up to the point of punching failure. The pile end resistance increased with the pile top load. When the ultimate bearing capacities of the SDCM piles were reached in the model tests, the ratio between pile end resistance and pile top load ranged from 19.4% to 54.2%, indicating that pile end resistance cannot be ignored.

Energy piles are a profitable solution for extracting shallow geothermal energy and have recently attracted increasing attention. However, the thermomechanical response of energy piles considering shaft resistance softening has not been sufficiently studied, which hinders the perfection of design methods for energy piles. To this end, an improved generalized nonlinear softening model was first developed to describe the thermomechanical loading–unloading–reloading response of energy piles. The parameters of the improved model can be easily calibrated using an interface direct shear test. We then proposed a nonlinear load-transfer approach for the thermomechanical analysis of energy piles considering the softening behavior of skin resistance by continuously describing the nonlinear load-transfer regime. The proposed approach was validated by comparing it with experimental measurements and other numerical methods. Finally, a parametric study was performed to assess the effects of various related parameters on the thermomechanical response of the energy pile. The results indicate that the proposed approach enriches the current methods for energy pile design and provides a helpful tool for obtaining the thermomechanical behavior of energy piles in the case of softening.

Excavation of spillways at dam crest is one of the most commonly utilized and effective engineering practices to mitigate the risk of landslide dams. The influence of spillway section shape on the breaching process of landslide dams was examined in this research via the flume tests using dams with one triangle and two trapezoid spillways. A smart and green testing system was proposed to simulate the overtopping breach process of landslide dams. The experimental results showed that the triangle spillway had the best performance to reduce the peak breach discharge and delay the occurrence time of peak breach discharge. Due to the worst seepage erosion and the formation of scarp, the peak breach discharge of the wide trapezoid spillway was the largest and occurred most quickly. The performance of the deep trapezoid spillway was between those of the triangle and wide trapezoid spillways. Considering the inconvenience of triangular spillway excavation for rapid construction, the cross-section shape of a deep trapezoid was suggested in the excavation of spillways.

Understanding the cracking characteristics of shale is significant for tunnel engineering and exploitation of oil and gas in shale. Unconfined compression tests were conducted on prismatic shale specimens with a horizontal prefabricated flaw. The angle between the bedding plane and the vertical compression direction changes from 0° to 90° at an interval of 30°. A high-speed camera was used to capture the cracking behavior, and the moment tensor inversion method of acoustic emission waveform was adopted for the source location and evaluation of the microfailure mechanism. The cracks compete to initiate due to stress-state dynamic redistribution, which determines the cracking behavior. The different bedding plane angles and prefabricated flaws significantly influence the cracking characteristics of shale specimens in unconfined compression tests. Five cracking modes and four main failure mechanisms were observed. The bedding planes greatly reduce shear cracks when their direction approaches the loading direction. This study provides a further understanding of the failure modes and mechanisms of shale specimens, which provides some references for projects involving shale.

A series of benched excavations are typically carried out on bedrock slope surfaces to improve the stability of soil–rock mixtures (SRMs) on the fill slopes. In this paper, the shear characteristics and micromechanisms of SRMs–bedrock interphases were studied by means of large direct shear tests and discrete-element numerical simulation. In the process, this study also investigated the influences of rock block content and interface roughness by combining the direct shear test and discrete-element method (DEM) numerical simulation results. This showed that the samples exhibit obvious bulk shrinkage during shearing. As the rock block content increases, fluctuations in the postpeak shear stress–displacement curves become more obvious. Cohesion is more sensitive to roughness, while internal friction angle is insensitive to roughness. Also, the internal friction angle is very sensitive to rock block content. Moreover, the shear strength and cohesion of the interphase increase along with the superficial roughness, demonstrating a quadratic correlation with rock block content. However, this increase in roughness also increases the fracturing of rock blocks in the interphase. Within a certain interval, the shear strength of SRMs–bedrock interphases can be estimated according to a fitted empirical formula.

The purpose of this study was to explore the influence and action mechanism of the stress amplitude on the evolution of the deformation behavior of sandstones during multilevel triaxial cyclic loading and unloading (CLU) under varying lower limits of stress (VLLS). To realize this purpose, a conventional triaxial compression test under a confining pressure of 5 MPa and multilevel triaxial CLU tests under VLLS and stress amplitudes of 5, 10, and 15 MPa were independently carried out. By summarizing and analyzing the change patterns of the deformation parameters of sandstones under the different stress amplitudes, the influence law and potential action mechanism of the stress amplitude on sandstones were illustrated. The test results indicated that the increase in stress amplitude provided more opportunity for grain slippage and crack formation in sandstones, causing further softening. As a result, the ratio of the stress at the point when the bearing capacity of the tested sandstones was lost at the postpeak stage to the peak stress decreased, and the elastic modulus decreased while the Poisson’s ratio increased. Based on an analysis of the evolution trend of the incremental irreversible strain, the aforementioned phenomena occurred because the change curve of the incremental irreversible strain gradually steepened with increasing stress amplitude, transitioning from a horizontal linear curve to a U-shaped curve. However, during the observed volumetric strain change, stress amplitude increase caused a reduction in cohesion in the sandstones, thus shortening the transition period from expansion to contraction. The sandstones were directly damaged without a transition period when the stress amplitude reached a certain level. Additionally, by generalizing and determining the typical deformation parameters, the process before rock failure was divided into four stages, each with a threshold. When reaching the different thresholds, hardening and softening mechanisms influenced the loading and unloading process in different ways. Combined with fracture analysis, the influence mechanism of the stress amplitude on the deformation behavior of the sandstones entailed that with increasing stress amplitude, the stress threshold was eventually reached. Therefore, the accumulated degradation rate of the mechanical properties attributed to the softening mechanism varied, further changing the microscopic evolution characteristics of sandstone deformation. The research results provide construction guidance in geotechnical engineering.

The primary focus of the present article is to evaluate the bearing capacity of ring footing placed over two-layered soils and subjected to vertical loadings applied over certain portions of the footing, namely, inner half, middle half, and outer half. The layered soils are chosen as (i) sand over sand and (ii) undrained clays overlying on another layer of undrained clays. The combined effect of layer strength, ring geometry, top layer thickness, soil–footing roughness, surcharge loading, and loading positions are extensively verified by using axisymmetric lower-bound theorem of limit analysis in conjunction with finite elements and nonlinear optimization. An interior-point method based on logarithmic barrier function is employed to carry out the nonlinear optimization. The sand and the clay layers are modeled with the smoothened Mohr–Coulomb and Tresca yield surfaces, respectively. The results are reported in terms of normalized bearing capacity and efficiency factor. The magnitude of normalized bearing capacity appears to be highly influenced by the position of applied loading, whereas the efficiency factor and the optimum upper layer thickness are found to be unaffected by the zone of loading positions. Failure patterns are drawn for several cases.

Freeze–thaw (F-T) cycles are one of the main deterioration factors for the performance of expansive clay in seasonally frozen soil regions. This study designed a unidirectional environmental boundary loading device for F-T cycle tests. Laboratory tests were conducted to quantitatively evaluate the effects of the F-T cycle on volume change behavior and mechanical properties of expansive clay with different degrees of compaction below the canal in Xinjiang. The SEM image processing was performed with the Image-Pro Plus image processing software to get pore parameters. The results showed that during the F-T cycle, the volume change of the sample gradually changes from contraction to expansion as the degree of compaction increases. As the degree of compaction increases, the hardening characteristics of the expansive clay are weakened, and the F-T cycle promotes the softening of the stress–strain relationship. The first F-T cycle resulted in a significant decrease of failure strength, and the failure strength of different compaction degrees decreased by 56.07%–67.54% after seven cycles. The failure strain and resilient modulus of the samples are attenuated to varying degrees after F-T cycles. The correlation rate between the porosity and the attenuation rate of the failure strength is 0.719–0.882, the corresponding weight reaches 0.419–0.445, and there is an excellent linear relationship between them. The research offers some important insights into the construction and maintenance of expansive clay engineering such as the Xinjiang Canal.

When a retaining wall is adjacent to a natural slope, the overturning of the wall is usually caused by a yielding foundation. At the point of overturning, the narrow backfill behind the wall has reached the active limit state. However, in previous studies, the foundation conditions of the retaining wall were not fully considered when the earth pressure on the retaining wall with the narrow backfill was calculated. To comprehensively consider the stress state of the retaining wall, the finite-element limit analysis method was employed to study the failure mode of a retaining wall adjacent to a natural slope. The simulation results indicate that the sliding surface starts from the wall heel, with one side developing at the surface of the natural slope and the other developing in the ground in front of the wall. Based on this failure mechanism, a slip-line computational model for the retaining wall was established. When the slip-line solution was compared with the finite-element solution, the results were in good agreement. The plastic zone of the soil was determined by the slip-line field. In addition, the slip-line solution gave the active earth pressure of the narrow backfill, the passive earth pressure of the soil in front of the wall, and the foundation bearing capacity. Moreover, several extensive parametric studies were conducted. Thus, the shape of the narrow backfill, the rough soil–wall interface, and the low-strength backfill are all conducive to reducing active earth pressure on a retaining wall.

A surcharge preloading method with time-dependent loading is widely used for accelerating the consolidation process of soft soils, and different loading patterns have a great effect on the consolidation characteristics. For one-dimensional nonlinear consolidation of soft soils considering the variable compressibility and permeability, the general approximate analytical solutions for one-dimensional nonlinear consolidation under time-dependent loading are derived. Moreover, two forms of boundary conditions are considered according to engineering practice. With reference to the general analytical solutions presented, the expressions for the solutions under several common loading patterns, such as the multistage instantaneous loading pattern, multistage linear loading pattern, and cyclic loading pattern, are given. The accuracy and correctness of the approximate analytical solutions are proven by comparing the approximate analytical solutions with the finite-difference solutions and two experimental results with different boundary conditions. Based on the approximate analytical solutions proposed, the consolidation behaviors of soft soils under different loading patterns are analyzed. In conclusion, the proposed approximate analytical solutions have a simple and clear form, which is convenient for calculations in engineering applications.

The shear (τ_p), creep (τ_c), and long-term shear (τ_∞) strengths of moraine soil are mechanical properties of high concern during the engineering construction and management process and were obtained by conducting large-scale direct shear and shear creep tests on the soil layer at the Dadu river bridge in Luding, China. The size of the test samples was about 1.0 × 1.0 × 0.50 m (length × width × height). The shear strength and creep behavior under different normal (σ) and shear (τ) stresses were analyzed, and the long-term shear strength was obtained from stress-displacement isochronal curves during the creep process. The results indicate that the shear strength of moraine soil relates to the content and distribution of large particles. The shear strength parameter of moraine soil is 0.765 (φ = 37°) and the cohesion parameter (c) is 64.2 kPa. The moment of the maximum creep displacement rate at the primary creep stage depends on the shear stress. The step-like increasing and jumping of shear creep displacement are evident during the middle-process of the secondary creep stage (e.g., 20–60 h when τ is 411 kPa under σ of 300 kPa), due to large particles rotating or overturning under high shear stresses. The empirical Burgers model predicts the creep displacement well. The ratio (τ_∞/τ_p) of long-term to shear strength ranges from 0.53 to 0.92, indicating that the creep effect has decays in the shear strength of moraine soil. The ratio (τ_∞/τ_c) of long-term to creep strength ranges from 0.65 to 0.85, indicating that moraine soil could easily transfer from viscous creep deformation to shear failure when the loading stress is higher than long-term strength. The results provide a valuable reference for shear strength analysis and long-term strength assessment of moraine soil regions.

The cumulative plastic deformation of a foundation associated with traffic loading causes subgrade instability, and eventually, failure of retaining structures. In the present study, hollow torsional shear tests were conducted on fiber-reinforced aeolian soil involving varying fiber contents, cyclic deviator stresses, cyclic shear stresses, and consolidation confining pressures using the Small-Strain Hollow Cylinder Apparatus, developed by GDS Instruments Ltd. (GDS SS-HCA). This enabled an investigation of the deformation characteristics and noncoaxial angle changes of fiber-reinforced aeolian soil under a heart-shaped stress path. The results indicate that fiber-reinforced soil deformation under cyclic loading involves axial (ɛ_z), radial (ɛ_r), circumferential (ɛ_θ), and shear (γ_zθ) strains, and deformation increases with increasing the cyclic number. The strain increases rapidly during the first 200 cycles and then gradually. The axial deformation decreases with increasing fiber content when the fiber content is less than 2‰ and increases when the content is more than 2‰. The plastic strain and total deformation decrease with increasing confining pressure but increase as the cyclic dynamic stress and cyclic shear stress amplitudes increase. Functional equations of the cumulative axial plastic strain and vibration numbers are proposed. The relationships between the model parameters, including the fiber content and cyclic torsional shear stress, are analyzed. The principal stress axis rotation causes variations between the major principal strain increment and the principal stress directions, representing the noncoaxial angle (β). The noncoaxial angle fluctuates during each loading cycle, exhibiting a V shape, for principal stress axis angles (α_σ) from −90° to −45° and −45° to 30°, and decreasing at angles varying from 30° to 90°, with a maximum noncoaxial angle of approximately 30° per cycle.

The bearing capacity of large strip foundations under combined loading is an important issue in geotechnical engineering, which is related to the design and stability analysis of foundations such as gravity dams, retaining walls, and ground anchorages of bridges. Herein, a new model for predicting the bearing capacity of large strip foundations under combined loading was proposed. First, a series of numerical simulation analyses of a large strip foundation resting on the surface of the soil were conducted to investigate the shape of the failure envelope in the V–M–H (vertical load, overturning moment, and horizontal load) loading space, and an improved form of failure equation was proposed. Second, the main factors influencing V_max (the vertical ultimate bearing capacity) and the shape of the failure envelope were determined. Last, an applicable empirical equation of the failure envelope in the V–M–H loading space was presented. The results show that the deflection angle of the ellipse (θ), which is considered as a certain constant by previous studies, varies with the vertical load (V); the width of the foundation (B), the depth of the foundation (D), the cohesion of the soil (c), and the internal friction angle of the soil (φ) are the main factors influencing V_max and the shape of the failure envelope; only parameters B, D, c, φ, and γ are needed to determine, in a unique way, the empirical equation of the failure envelope in the V–M–H loading space. The proposed model provides a convenient means of calculating the bearing capacity of large strip foundations on soil under combined loading.

Tunnel construction in mountain areas, especially in karst regions, is challenging due to complex hydrogeological conditions in such regions, such as water inrush disaster induced by water-bearing structures that may jeopardize tunnel construction safety. To identify potential water inrush sources, this study first analyzed regional hydrogeological conditions of the Yuelongmen tunnel that cross under the river. Then, the tunnel-induced polarization method was employed to probe three-dimensional (3D) spatial location and distribution of water-rich areas. Based on detection results, numerical simulation was carried out to study the corresponding velocity and pressure for each probing line set in the numerical model, and flow characteristics after water inrush were summarized. Finally, optimized evacuation routes were designed to minimize the potential damage caused by the water inrush. Research results may provide critical implications for water inrush analysis and reduce casualties during tunneling in karst regions in China.

Observed damages of bridge bearings in some engineering projects during high-temperature asphalt pavement paving has attracted more attention to the dramatic temperature effect during the paving process. In this research, field monitoring was conducted for measuring the temperature variations and temperature-induced responses of bridge components during the asphalt mixture paving, and the Jiujiang Yangtze River Bridge in China was used for illustration. Based on the transient temperature field theory, a temperature field model of steel beam picked out from Jiujiang Bridge was established using the commercial finite-element (FE) package Abaqus, and the element-deletion method was used to simulate the dynamic paving process of asphalt pavement. The temperature responses of steel beam were calculated by applying the temperature load during the pavement paving to the steel beam model, and the field monitoring data validated the numerical simulation method. Finally, the validated simulation method was used for safety analysis of a bridge bearing system during pavement paving. The results show that the temperature field and temperature responses of a steel bridge during the pavement paving present spatiotemporal variation characteristic, and these temperature effects are likely to cause damage in the bridge bearings. To ensure the structural safety of the bridge bearing system in Jiujiang Bridge, the width of each paving area should be no larger than 5.5 m.

This paper presents a constitutive model for simulating the stress–strain behavior of overconsolidated structured soils. The model extends the scope of a previous 10-parameter constitutive model proposed by the authors for structured soils. It uses a variable normal compression index dependent on the degree of structure to simulate structure degradation during loading. The model also introduces the concept of subloading plasticity to prevent the peak shear strength of structured soils from being overestimated in the overconsolidated state. The performance of the proposed model in describing the mechanical behavior of structured soils with different initial overconsolidation ratios is assessed. The proposed model is verified using the experimental data available in the literature for both naturally and artificially structured soils under compression and shearing conditions. The results indicate that the proposed model simulates the mechanical response of structured soils reasonably well in both normally consolidated and overconsolidated conditions.

Experimental studies found that water flow in clay might not obey Darcy’s law. In some fine-grained soils, the water flow could occur only when the threshold gradient was exceeded. This study investigates the effects of threshold gradient on the consolidation profile. The well-established model CNDF2 is employed with some modifications. Verification examples demonstrate the accuracy of the numerical simulation in this study. Compared with the existing solution in the literature, modeling results in this study are more reliable because the criterion of seepage is independent of the position of the seepage front. Parametric studies find that the excess pore-water pressure cannot be fully dissipated if there is a threshold gradient. A larger value of normalized threshold hydraulic gradient R will result in a larger value of residual excess pore-water pressure. A permeable bottom boundary can contribute to the dissipation of residual excess pore-water pressure. The final settlement will also be affected by the threshold hydraulic gradient. A larger value of R will lead to a smaller final settlement due to the residual excess pore-water pressure. The average degree of consolidation will not be affected by the threshold hydraulic gradient.

The contribution of tensile cracks to the stability of cracked slopes is important. The tensile characteristics of tensile cracks have a significant influence on the stability of rock slopes. Therefore, in this paper, based on the upper-bound limit analysis method and modified M–C failure criterion, an improved failure mode of multislider of rock slopes is established by assuming that the first m − 1 sliders are shear failures and the other n − m + 1 sliders are tensile failures. The superior division of the tension zone and shear zone is realized through the optimized solution and the corresponding value of m. The influences of each parameter on the stability coefficient, failure region, tension zone, and shear zone are emphatically explored. The results show that the accuracy and superiority of the improved failure mode is verified by comparative analysis. The stability coefficient γH/c decreases nonlinearly with an increase in slope angle β and increases nonlinearly with an increase in dimensionless parameter u (the maximum increase in γH/c is up to 37.2%). The critical height of the slope, the whole failure region, and the ground failure length decrease sharply with an increase in β and increase nonlinearly with an increase in u (the critical height increases up to 20%). The critical height of the slope and the whole failure region increase nonlinearly with an increase in the internal friction angle φ. In addition, the ground overload weakens the effect of tensile strength, while seismic force strengthens this effect, but neither is conducive to rock slope stability. In addition, u is beneficial to slope stability, and the tensile characteristics are more significant for steep rock slopes with a small φ. In practical engineering, the energy dissipation and tensile strength characteristics of rock masses should be considered in the process of crack development, especially in the stability evaluation, reinforcement, and protection of high and steep slopes with frequent earthquakes.

Deep mixed (DM) columns are being increasingly used in regions that host thick saturated soft clays. Under such geotechnical conditions, partially penetrated DM columns are predominantly designed to improve shallow foundations. Ground settlement can develop gradually over decades, however, due to the consolidation and rheological behavior of the subsoil. This work developed an analytical solution for calculating the rheological consolidation of partially penetrated DM-column-reinforced ground under a rigid foundation following the rheological Burger’s model. Based on the equal strain assumption, the consolidation problem was converted into a simple problem of one-dimensional consolidation with a double-layered system. The derived solution revealed that the reduction in column permeability to less than 10% of the soil permeability had a minor influence on the consolidation rate. The consolidation rate increased slowly with increasing penetration depth.