International Journal of Geomechanics

Measurement of the soil-water characteristic curve (SWCC) is time-consuming for soils such as bentonites. It is desirable to develop a first-hand estimate of SWCC from a statistical generalization of the available data. A database for SWCCs of bentonite was compiled from the literature. The proposed approach entails the parameterization of SWCCs and constructing a multivariate probability distribution for the SWCC parameters. The choice of parameter constraints has a significant impact on SWCC quantification, which has not been studied for bentonites. Therefore, a database from this study was used to investigate the effect of van Genuchten (vG) model constraints on SWCC parameter statistics of bentonite. The three-parameter vG model with parameters $\alpha ,n$, and $m$ provided the best choice. Subsequently, trivariate probability distributions of parameters $\alpha ,n$, and $m$ were constructed using Gaussian and $t$ copulas. The proposed trivariate copula is suitable for modeling the asymmetric dependence structure of vG parameters. It was demonstrated that the proposed approach can be used to construct the confidence intervals for SWCCs of bentonites. In the absence of measured data, the trivariate distribution provides a first-hand estimate of the SWCC. It also can be used as an informative prior for updating site-specific limited data using a Bayesian approach.

A series of confined compression tests and triaxial tests under different test conditions were carried out on two types of calcareous sand from the South China Sea. Notably, drained and undrained tests under monotonic, cyclic, and creep testing conditions were conducted. This study was focused on the relationship between the relative breakage and total input energy under different test conditions. The influences of grain size were also investigated. The test results showed that a large number of particle breakages occurred in the calcareous sand under different modes of loading, which has a significant influence on the mechanical properties of the material, and increasing the confining pressures resulted in increases in the particle breakage of the calcareous sand. The relationship between the relative breakage and total input energy was unique regardless of the testing conditions in this study, and larger grain size resulted in more significant particle breakage.

Strong dynamic disturbances constitute an important problem threatening the safety of deep underground engineering projects. The mechanical mechanisms responsible for such disturbances in deep rock masses can be revealed by studying stress waves propagating across them. In this study, the propagation of P-waves across a deep rock mass was investigated both numerically and theoretically. The Hoek–Brown (HB) model, which is able to account for the stress state and nonlinear failure of the rock mass, was employed. In particular, the time-domain recursive method was extended to analyze the propagation of P-waves across the rock mass following the HB failure criterion. Good agreement is found between the theoretical results and simulations, which demonstrates that using the Universal Distinct Element Code (UDEC) with the HB model to study the transmission of P-waves across rock masses is eminently feasible. The effects of the disturbance factor, confining pressure, incident amplitude, and coupling of joints and rock mass quality on wave propagation were also studied using the UDEC in a systematic manner. The results show that for an incident P-wave of given amplitude, the greater the rock mass quality and smaller the disturbance factor, the greater the transmission coefficient. In addition, there is an upper limit to the effect the confining pressure has on the transmission coefficient. The amplitude of the incident wave also has an important influence on the transmission coefficient. Finally, if the quality of the rock mass is good and the disturbance slight, then the attenuation of the wave is primarily caused by the joints.

This paper presents an analytical model for the estimation of the ultimate pullout capacity of vertical anchors embedded in frictional soils. The analytical model developed using the principle of limit equilibrium will be capable of capturing more realistic variations in pullout capacity because of its inherent capability to consider three-dimensional failure scenarios, anchor roughness, and anchor material effects. The analytical model was verified with three-dimensional numerical simulations. In addition, the predictions from the proposed model were compared to several pullout capacity prediction models using 86 experimental data points from literature. Results show that the present model can predict the pullout capacity of shallow and intermediate anchors with more accuracy and reliability than the available pullout capacity prediction models. In addition, a comprehensive parametric analysis is also presented. Some of the basic conclusions are: the demarcation aspect ratio between a single and continuous anchor is 10 rather than 5; the omission of the contribution from side flanks to the ultimate pullout capacity resulted in a discrepancy of as much as 37.4%; and $\delta /{\phi }^{\prime }$ does not remain constant, irrespective of the embedment depth ratio and anchor aspect ratio.

One of the most important features of soil behavior is the dependence of stress path. A series of large-scale triaxial compression tests was conducted to investigate the effect of stress path on critical state and particle breakage–induced grading evolution of rockfill material. All tests were first consolidated under constant principle stress ratio condition, and then sheared under three different stress paths, including constant lateral stress ${\sigma }_3$, constant mean effective stress $p^{\prime }$, and constant vertical stress ${\sigma }_1$. Test results indicate that the mean effective stress $p^{\prime }$, deviatoric stress $q$, and void ratio $e$ along different stress paths reached the consistent critical state line (CSL) in the $p^{\prime }\text{-}q\text{-}e$ space. There was a power function between $p^{\prime }$ and $q$, and a linear relation between $e$ and ${(p^{\prime }/p_a)}^{\xi }$ with $\xi =0.5$ at the critical state. The particle breakage under different stress paths was found to be consistent at the same critical state, and a unique relation among $e$, $p^{\prime }$, and the particle grading parameters at the critical state existed irrespective of stress paths. The test results at the critical state formed a straight line in the $e\text{-}{(p^{\prime }/p_a)}^{0.5}\text{-}{I}_G$ space.

Cubic specimens of three rocks—granite, marble, and sandstone, representing very strong rock, moderately strong rock, and weak rock, respectively—were tested under polyaxial stress. The objective was to determine the optimal strength criteria for these rocks by using the polyaxial test data. Experimental results indicated that the failure strength considerably depended on ${\sigma }_2$ and ${\sigma }_3$ for all the rocks. Seven well-known rock-strength criteria were employed to examine the true-triaxial data with regard to the predictability in practical applications, comparison between the best-fitting functions (experimental data) and theoretical (predicted) solutions, stress trajectories on the deviatoric plane, and stress trajectories on the meridian plane and ${\tau }_{\mathrm{oct}}-{\sigma }_{\mathrm{oct}}$ space. A detailed analysis and comparison of these criteria showed that the Mogi–Coulomb criterion, modified Wiebols–Cook criterion, and modified Lade criterion provided a better prediction of the polyaxial strength for the three rocks in most cases, which is attributed to the high ${\sigma }_2$ dependence and sensitivity of the selected rocks. The Mogi 1971 and 1967 criteria could not be correlated to the strength parameters (cohesion and frictional angle) and failed to predict the real strength values of an in situ rock mass without complex polyaxial compression tests. Furthermore, the stress trajectories on the deviatoric plane illustrated their disadvantages in theoretical interpretation and numerical implementation. The inferiority of the Mohr–Coulomb criterion and Drucker–Prager (DP) criterion in describing the rock strength under polyaxial stress was verified by the higher deviation between the theoretical (predicted) strength values and experimental strength values. The nonconformity between the stress trajectories and experimental data for the Mohr–Coulomb criterion and DP criterion on the meridian plane and in the ${\tau }_{\mathrm{oct}}-{\sigma }_{\mathrm{oct}}$ space validates the preceding viewpoint.

Particle crushing contributes significantly to the time-dependent compression behaviors of crushable granular soils. It also is widely accepted that flooding aggravates the breakage level of soil particles. This study investigated the combined behavior. A crushable granular soil was chosen for one-dimensional compression tests, i.e., constant rate of strain tests and multistage loading oedometer tests, under dry and saturated conditions. The crushing mechanism of particles was investigated by measuring the microhardness of soil particles. The shape characteristics (circularity, aspect ratio, roundness, and solidity) of particles before and after tests were analyzed by digital image processing (DIP) methods. The results showed isotach behavior for the tested soil in saturated condition. The compression curve, creep behavior, and level of particle breakage of initially dry specimens evolved in the same manner in which the initially saturated specimens behaved. The microhardness test clearly attributed the breakage of particles to the disaggregation of clay minerals which are the bonding materials between microquartz particles. This disaggregation became more severe after the moisturization of soil particles. The plastic work done to each specimen and the corresponding breakage ratio were correlated by two hyperbolic functions, which define two characteristic curves, for dry and for saturated/flooded conditions. The results from DIP analysis indicated that the average values of shape descriptors of all the particles in one specimen changed during compression, with a greater level under saturated or flooded condition than under dry condition.

Abutment walls in integral abutment bridges (IABs) move in a cyclic pattern in response to temperature-induced expansion and/or contraction of the bridge superstructure. The repetitive abutment movements cause an active-wedge slumping and passive-wedge densification of the retained backfill in the vicinity of the wall. These effects develop progressively with the number of abutment movements and eventually result in escalation of lateral soil pressure acting on the wall in addition to settlement in the approach adjacent to the wall. This paper investigated and gained further insight into the aforementioned effects on the performance of the integral abutments by means of numerical and experimental studies of an abutment wall retaining soil backfill and subjected to passive and active horizontal displacements. This paper also examined the application of expanded polystyrene (EPS) geofoam as a fill material to alleviate the lateral earth pressure ratcheting and the soil settlement in the IAB approaches.

A total of five model nondisplacement piles tests were conducted to analyze the different volumes of tip grouting on the pile load-displacement response. The ultimate compressive bearing capacity of single piles with different tip grouting volumes is higher than that of the nongrouting test pile by 37.5%–112.5%. In addition, the height of the grouting returned is approximately 14 times the pile diameter (approximately 0.65 m) above the pile tip. A simple analytical method is presented for nonlinear analysis of the load-displacement response of a single postgrouting pile, considering different tip grouting volumes and grouting returned heights. Two models are adopted in the proposed approach. One model uses a modified hyperbolic model, which introduces the enhancement coefficients ${\alpha }_s$ and ${\beta }_s$ to describe the contribution of the grouting returned on the pile shaft resistance-displacement relationship. The other model is based on test results that capture the pile tip resistance-displacement response at the pile tip. In addition, a highly effective algorithm is proposed for the analysis of the load-displacement behavior of a single postgrouting pile based on the two models. Comparisons are made among the results of the present method, model test measurements, another analytical method, and two field cases study measurements. The comparisons show that the results of the present method are in good agreement with the measured results of the model tests, the measured results of two field case studies, and the calculated results derived from the other analytical method. A parametric study was conducted to analyze the influence of grouting volume on the pile shaft resistance enhancement coefficient and parameters related to the proposed model on the load-displacement response.

This paper presents a framework for the incorporation of the gradation curve in the description of mechanical behavior of unsaturated soils at low to medium degrees of saturation. Unsaturated soils have self-equilibrating initial stresses arising from surface tension forces acting on water menisci, which depend on the microstructure of saturation, particle surface contact characteristics, and pore size distribution (POSD). The latter, in turn, can be related to gradation curve. Unsaturated soil is treated here as a three-phase composite material, and its mechanical response is derived from that of its constituents: soil skeleton, water, and air. This approach leads to an analytical expression for the soil water retention curve (SWRC) in which the critical parameter to be determined is the water menisci area per unit volume ($S_{\mathrm{wma}}$) of the soil. This parameter can be identified from the gradation curve using well-established methodologies in soil science and agricultural engineering. Numerical simulations of triaxial tests show that deformation and strength of unsaturated soils, at a given degree of saturation and confinement, are influenced by the gradation curve, and its incorporation in the description of mechanical behavior of unsaturated soils is rational.

Highway pavements with longitudinal cracks are often seen on expansive subgrade soil. This paper proposes a model using the Winkler foundation theory to analyze the pavement by considering it as a beam resting on expansive soil. To integrate the heave/shrinkage of expansive soil in the model, the concept of virtual load is introduced by expressing it as a Fourier series. The virtual load is formulated following the inverse theory of mathematics by taking the Fourier constants as material parameters from the beam deflection equivalent to the heave/shrinkage of expansive subgrade soils. As an example of the model application, a case study was performed by incorporating the measured field moisture contents from research Roadway FM 2 in Texas. The extreme heave or shrinkage displacement of the expansive subgrade soil was estimated from the calculated moisture contents, which were obtained using software VADOSE/W. Locations of the cracks observed in the field matched well with the locations where the maximum bending moments were discovered from the established model.

To capture the nonassociated state-dependent constitutive behavior of soils subjected to different initial densities and pressures, a novel approach, the fractional-order ($\alpha$) plasticity, was developed, which extends the previous $\alpha$ plasticity model for more general loading conditions by using the transformed stress method. The developed model was found to have the following key features: (1) state dependence of the three-dimensional (3D) stress-dilatancy relationship was simulated without using empirical state parameters; (2) 3D nonassociated plastic flow rule was captured without using additional plastic potentials; and (3) state-dependent plastic hardening and softening was characterized without using state parameters and plastic potentials. To validate the extended 3D model, a series of laboratory test results of different soils, for example, rockfill, sand, and clay, under different loading paths were simulated, where a good agreement between the model predictions and the corresponding test results can be found.

Pressure buildup induced by geological carbon sequestration (GCS) will decrease the effective stresses in the storage formation, and geomechanical effects of overpressure may affect fault stability, possibly resulting in felt induced seismicity. Predicting the geomechanical stability of faults is of crucial importance for the safety of GCS. We applied a numerical approach to evaluate the potential magnitude of fault slippage for a specific stress regime. Next, we focused on the geometry and structures of fault zones through comprehensive analyses of the thickness of the overburden ($H$), the fault dip ($\mathrm{\Phi }$), and the distance between the fault and the injection well ($D$). Based on the relationships of $D$, $H$, and $\mathrm{\Phi }$ with the corresponding fault behavior, we obtained a traffic light indicator diagram to assess the risk of induced seismicity at a specific level of each factor. To overcome the complicated relationship between factor variations and the corresponding fault slippage, we introduced a danger surface in the traffic light indicator diagram with a security threshold of inducing moderate to strong seismicity to distinguish the danger zone. This approach provides physically sound outcomes for prioritizing the well location to avoid the risk of inducing strong seismicity.

Rockbursts are a common form of disaster that occur during the construction of deep tunnels in hard rock. This is especially the case in the breakthrough stage of excavation, when even more attention should be paid to the risk of rockburst in order to ensure construction safety. This work studied the characteristics of the microseismicity associated with 10 breakthrough cases in the deep tunnels (maximal depth 2,525 m) of the Jinping-II Hydropower Station in China. The results showed that the microseismicity was relatively more active in the breakthrough period (compared with that in adjacent sections) due to the effect of working two faces in tandem and was concentrated in the breakthrough section. Furthermore, the characteristic $c$-value associated with the seismic energy–potency relationship was larger, indicating that the apparent stress was greater in the breakthrough section. Spatiotemporal changes in microseismicity that are associated with rockburst development were found in the breakthrough section which can be used to qualitatively warn of the risk of rockburst. Rockburst risk can be quantitatively assessed during tunnel breakthrough based on the monitored microseismicity and a quantitative method of rockburst warning. Based on results thus obtained, the rockburst risk in the breakthrough section was found to increase continuously as the distance between the two working faces decreased. When both working faces are excavated in the breakthrough section, the quantitative risk of rockburst increases significantly. However, when only one working face is in action, the quantitative risk of rockburst increases only slightly. The results of this work will be helpful in warning of impending rockbursts, and thus improving the safety of the construction process, when breakthrough is carried out in deep tunnels excavated in hard rock.

The main factors that make longwall mining projects economical are roof control and prediction of roof behavior in roof caving and face advance. Sudden and unexpected roof fall not only endangers the safety of employees but also destroys and damages the extraction equipment and components. In addition, there are financial and economic impacts because the extraction operation is interrupted. Therefore, determining the first roof weighting effect interval (FRWEI) and the periodic roof weighting effect interval (PRWEI) are very important in longwall mining. There are several methods to determine the FRWEI and PRWEI. This paper investigated the behavior of steep layers during the roof caving process in the gob space by numerical modeling, and then estimated the value of the FRWEI and PRWEI at the E3 panel of the Tabas Parvadeh coal mine. The roof failure criterion was based on the Sakurai equations. According to the numerical modeling results, the FRWEI value is 11 m and the PRWEI value is between 2.5 and 4.5 m.

A simple fully coupled constitutive model for unsaturated soils is presented and used to simulate the behavior of unsaturated soils subjected to undrained conditions. The mechanical model is based on the modified critical state model and the effective stress concept. This mechanical model is coupled to a hydraulic model able to simulate the soil–water retention curves during wetting-drying cycles. The hydraulic model uses the grain and pore size distributions to approximately reproduce the structure of soils. Plastic volumetric strains modify the pore size distribution of soil, which in turn modifies the retention curves. The result is a simple general fully coupled constitutive model for unsaturated soils able to simulate different stress paths. The simulation of undrained triaxial tests requires the correct simulation of the hydromechanical coupling phenomenon. Some comparison between numerical and experimental results of undrained triaxial tests show the adequacy of the model.

Geomembranes are thin polymeric sheets used as barriers to liquid or gas intrusion in earth structures due to their low permeability. The mechanical behavior of geomembrane-soil interfaces plays an important role in the stability analysis of geomembrane structures under cyclic loading caused by an earthquake or traffic. In this study, a series of cyclic shear tests were conducted using a large-scale direct shear apparatus to observe the cyclic shear response of geomembrane-sand interfaces, with emphasis on vertical displacement and cyclic shear stiffness. The influences of vertical pressure, geomembrane texture, and cyclic shear loading form on the cyclic shear behavior of geomembrane-sand interfaces were examined. The cyclic shear stiffness showed an increasing trend with increasing vertical pressure, but significantly decreased with increasing shear-displacement amplitude. Textured geomembranes can effectively improve the cyclic shear strength of geomembrane-sand interfaces. The volumetric behavior of geomembrane-sand interfaces is evidently dependent on the form of cyclic shear loading and the magnitude of applied vertical pressure. The cyclic shear behavior of pure sand was also compared with that of geomembrane-sand interfaces.

This paper reports a comprehensive study including detailed experimental, theoretical, and numerical analyses to evaluate the performance of two predominant soil-structure interaction models, that is, the Winkler model and Pasternak model, in predicting the predominant natural frequency (PNF) of structures partially embedded in soils. For the evaluation, PNF-based scour detection, a nondestructive testing technique that has been receiving increasing attention, was adopted. First, a series of lab experiments was conducted using idealized piers partially embedded in two representative soils, that is, a sand and a clay, to measure the PNF-scour depth relationship. Next, a mathematical model was established and numerically implemented to predict the PNF of the idealized piers for scour detection. The soil-structure interaction was formulated using the Winkler model, which only considers the modulus of subgrade reaction for soils, and the Pasternak model, which considers the shear interaction in addition to the modulus. The numerically computed PNFs were then compared with those from the experiments in this study and a documented field test. Our results clearly show that when structures are partially embedded in soils, the Winkler model yields a better PNF prediction than the Pasternak model, regardless of the types of test piers and soils. This finding is different from those obtained in the dynamic response of structures resting on or fully embedded in an elastic foundation (i.e., not partially embedded), where the Pasternak model yields more realistic results than the Winkler model because of its consideration of the continuity of foundation media via the shear interaction. Because of the shear interaction, the PNFs predicted with the Pasternak model in this study are about 24%–38% and 31%–39% higher than the predictions with the Winkler model and the measured PNFs, respectively.

Subgrade long-term deformation was investigated by taking the effects of both traffic load and drying–wetting cycles into consideration on the basis of numerical calculation and laboratory experiments. The total subgrade long-term settlement is composed of three parts: traffic load induced cumulative plastic deformation derived by calculated dynamic stress, deformation generated by dissipation of pore water pressure and attenuation of subgrade modulus due to drying–wetting cycles, and vertical deformation induced by weather cycles. The effects of the number of drying–wetting cycles and cycle amplitude, subgrade soil static shear strength, confining pressure, compaction degree, static constant load above the subgrade, and number of load cycles were taken into account to establish the subgrade deformation model. The layerwise summation method was also used to calculate the subgrade cumulative plastic deformation. Furthermore, a selection of computation results of the three deformation components was shown in detail and the impacts of number of load cycles, degree of compaction, subgrade depths, and the characteristics of drying–wetting cycles on the long-term deformation were discussed using the proposed model.

For a foundation to perform safely, the ultimate strength of each pile must satisfy the structural and geotechnical requirements. Pile load testing is considered to be a direct method for determining the ultimate geotechnical capacity of piles. In this paper the dynamic and static response of a driven steel pipe pile monitored as part of a highway bridge construction project in New South Wales, Australia, has been simulated and then numerically analyzed using the finite-element method. A continuum numerical model has been established to simulate the dynamic load testing of steel pipe piles with unplugged behavior in which adopting measured soil properties resulted in a reasonable match between the measured and predicted results and without needing random signal matching in an iterative process. Settlement at the head and toe of the pile was then calculated when a static load represented by a dead load plus a heavy platform load of a bridge was applied over the pile head. During the dynamic and static load testing simulation, a hardening soil model with small strain stiffness was used to obtain the best correlation between the large and small strains, which occurred while the pile was under static load and being driven. The numerical predictions obtained using continuum finite-element simulations were then compared with the corresponding predictions obtained from the Case Western Reserve University (CASE) method and CASE Pile Wave Analysis Program (CAPWAP) to evaluate the predictions. The results show that the hardening soil model with small strain stiffness exhibits a reasonable correlation with the field measurements during static and dynamic loading. Moreover, parametric studies have been carried out in the established continuum numerical model to evaluate how the interface properties between the pile and soil and the reference shear strain define the backbone on the velocity at the head of the pile and traces of its displacement. Evaluation of dynamic pile load testing based on the continuum-based finite-element model has many advantages for geotechnical engineers dealing with pile design because an established continuum numerical model can assess pile testing under more realistic conditions. This model can also be used to evaluate the performance of piles under different loading conditions, such as combined vertical and lateral loading on a single pile or group of piles and piles near existing structures. Furthermore, this method retains the continuity of different stages of modeling from simulating pile driving, quality control, and investigating settlement, while all these analyses are carried out using one software.

Barriers are commonly used to intercept landslide flows or debris flows. The presence of a barrier changes the flow condition and leads to a buildup of earth pressure in a zone behind the barrier. Investigating this buildup process is essential to understand the landslide–barrier interaction and the stress evolution inside the earth flow. This study used an explicit integration program to simulate earth pressure buildup in the impacting earth flow in a series of two-dimensional (2D) and three-dimensional (3D) impact cases. In the idealized 2D flow cases, the stress state of earth flow reached the active limit state after the flow started and maintained the stress state until impact. During impact, horizontal earth pressure buildup occurred and propagated backward to the continuing flow; a dead zone thus formed. When the material ceased flow, a static earth pressure distribution was achieved. Starting from the distance at which the static lateral earth pressure coefficient was close to that in the greenfield case, the coefficient increased toward the barrier due to the earth pressure buildup, approaching the passive mode in the dead zone immediately behind the barrier. The static earth pressure on the back of the barrier was not uniform, with a passive mode in the dead zone and an active mode in the run-up zone in which the earth pressure was more easily released after impact. In the 3D flow cases, the opening spaces at both sides of the barrier affected flow conditions and weakened the buildup process.

Alluvial silt is widely distributed in the Yellow River basin, especially in its largest alluvial plain, the Yellow River delta. In this area, owing to the wet and soft characteristics of the alluvial silt, cumulative settlement often occurs under traffic loads. To reduce the settlement, various methods are applied to improve the subgrade bearing capacity in this area. Among them, the use of calcium oxide (burnt lime) to treat shallow subsoil is a common selection. However, the effect and mechanism of this method have not been fully determined. Therefore, a large integrated device was developed for an in situ test so that the comparative analysis of the short-term settlement of the natural and burnt-lime-treated ground under traffic loads can be achieved. For the long-term cumulative settlement, a numerical method using a cumulative deformation model was applied to analyze the settlements after 10 years. Furthermore, the numerical method respectively predicted the settlement after 1 and 2 years to compare with the in situ test. The in situ test results demonstrate that the wave impedance of the alluvial silt subsoil treated with burnt lime grows and both the dynamic stress caused by wheel load and the excess pore water pressure are reduced. These indicated that the short-term cumulative settlement was significantly reduced after the alluvial silt subsoil was treated with burnt lime. Moreover, the results obtained by the numerical method are similar to those in the in situ test. For the long-term cumulative settlement, the calculation results of the numerical method indicated that the use of burnt lime to treat the ground is effective. In detail, 10 years later, the settlement of the burnt-lime-treated ground decreased by about $1/5$.

A mathematical model was designed to analyze the propagation characteristics of Love waves traversing through an orthotropic visco-elastic FGM layer under initial stress lying over a half-space with void pores. The uppermost surface layer and common interface between the layer and half-space are considered irregular in nature. Using Biot’s theory, the governing equations of motion were obtained, and further displacement components for the layer and half-space were derived with the aid of the variable separable method. After applying the suitable boundary conditions, the complex form of the velocity equation was derived. In order to study the propagation and damping characteristics of Love waves in the present model, the velocity equation was expanded into its real and imaginary parts. From the imaginary part, damped velocity characteristics were analyzed, whereas from the real part, the phase velocity characteristics are discussed in detail. A comparative study was conducted in which the curves were plotted for two cases: one when both boundaries are corrugated and another when boundaries are planar. The study reveals the fact that Love waves propagate faster in a stratified medium with corrugated boundaries than a medium with planar boundaries. The presence of corrugated surfaces minimizes the damping characteristics of Love waves. Curves were plotted to analyze the impact of initial stress, heterogeneity, and visco-elasticity on the amplitude and frequency content of Love waves. Moreover, in order to strengthen the validity and applicability of the considered model, error analysis was carried out graphically.

For tunneling in squeezing rock, large deformation induced by tunnel excavation and creep of squeezing rock has been a great challenge during construction. This large deformation would keep growing for a long time, significantly threatening the stability of the tunnel. In this study, a new foamed concrete is introduced. Relative to conventional foamed concrete, the new foamed concrete has the characteristics of good ductility (it maintains its integrity and is not easy to crack), high compressive strength (the uniaxial compressive strength is 3.12 MPa, whereas for the conventional concrete it is about 0.9 MPa), and tight adhesion with cement concrete (proven by shear strength at interface between the foamed concrete and the cement concrete) as shown by laboratory tests. To evaluate its performance as a cushion material in the yielding support for a tunnel, the foamed concrete was applied in a yielding support for a deep-buried tunnel in squeezing rock by numerical simulation. Compared with the results of the stiff support, the contact and shear stress at the interface between the cushion layer and the second lining are very small, resulting from the capacity of the foamed concrete to endure great loads and absorb energies from the creep of surrounding rock, thereby improving the stress state of the second lining and reducing the deformation of the second lining.

Based on the statically indeterminate beam model for fully grouted bolts proposed by others and taking into account the combination of the axial and shear forces activated in the bolt, an improved method was developed for predicting the shear resistance contribution of passive fully grouted bolts to jointed rock. An algorithm for calculating the length of the transverse deformation section of a passive fully grouted bolt under shearing was derived by incorporating the minimum total potential energy principle, and parametric investigations were carried out to evaluate the effect of the anchoring parameters, such as bolt diameter, rock strength, bolting angle, and joint friction angle on the bolt contribution. Comparisons were made between the developed method and laboratory shear test results as well as between the developed method and other analytical predictions proposed by previous studies. The results showed that the theoretical model presented in this paper is in good agreement with the experimental results and, thus, provides a better prediction of the shear resistance provided by rock bolts. The presented analytical method can be used to improve the bolting design for the reinforcement of jointed rock.

Unsaturated soils over a wide suction range are widespread in nature. The shear strength of unsaturated soils is a fundamental property in various geotechnical designs. In this paper, a systematic study was conducted to investigate the effect of soil type on the shear strength of unsaturated soils. Shear strength for different types of soil over a wide suction range can be roughly classified into three types. Numerous existing shear-strength equations of unsaturated soils were used to predict the shear strength of different types of soil over a wide suction range, and the advantages and limitations of those equations were discussed. In addition, new equations for the shear strength of unsaturated soils were proposed based on the relationship between the average skeleton stress and the suction over a wide suction range. The results showed good agreement between the predicted and measured shear strengths results over a wide suction range for sand and silty soils.

In this paper the study of FEMA-P695 on collapse performance of moment frames is extended to take soil–structure interaction into account. Special reinforced concrete moment frames being 4, 8, 12, and 16 stories tall resting on firm, medium, and soft soils are considered. The incremental dynamic analysis is performed under several strong ground motions to determine the fragility curves of the same structures both on rigid and flexible bases. Modeling of the flexible base is performed using the beam-on-nonlinear-foundation method in which the underlying soil is replaced with materially nonlinear no-tension springs. The comparative study reveals that for keeping the collapse probability lower than a certain value, the maximum acceptable design spectral acceleration including soil–structure interaction has to be considerably smaller than that on a fixed base. The reason is shown to be happening because of larger drifts in the lower stories of a building when its base is flexible. Moreover, modified fragility curves are developed for fixed-base structures in which effects of soil–structure interaction are included. A simple tool for performing such a correction is also presented. The correction is shown to be quite distinctive in certain cases.

The dynamic properties of rock under different strain rates and temperatures play an important role in the stability of rock mass. To investigate the dynamic behavior of granite specimens subjected to high strain rates and relatively low temperatures, dynamic compression tests were carried out using the split Hopkinson pressure bar (SHPB) experimental system. The strain rate effect on dynamic characteristics of granite at temperatures from 25°C to 150°C were studied and the relationships between dynamic failure modes and the energy absorption of granite specimens at different strain rates were revealed through rock fragment analysis. Meanwhile, the damage evolution was quantified by elastic moduli and porosity. The results indicate that the dynamic peak stress, peak strain, and specific energy absorption (SEA) have positive correlations with strain rates. The dynamic compression strength shows an increase when the temperature rises from 50°C to 110°C, then decreases with higher temperatures, while the elastic modulus is more sensitive to temperature than strain rate. The thermal damage decreases at low temperature and appears to be negative below 110°C. A power function relation between SEA and fragment size is found to exist at different strain rates. It denotes that 110°C is a critical temperature that induces changes in physico-mechanical properties and the relatively low temperature has an enhancement effect on the dynamic strength of granite samples.

The present study proposes a finite-element approach to focus on the load sharing and deformation aspects of combined pile–raft foundation (CPRF) in a serviceability-based framework. Soil nonlinearity was considered by depicting it as a two-parameter medium. Two concurrent analyses were carried out for raft and piles in CPRF, reckoning various soil–structure interactions and ensuring displacement compatibility at the pile–raft junction. A pivotal aspect of this approach is that under vertical loading it incorporates the effect of rotational resistance beneath the flexible raft as the second parameter of the soil medium. The proposed method was validated with available centrifuge test results. Parametric studies illustrate that with a decrease in pile spacing, the differential settlement of the system diminishes, although for higher pile load sharing optimization of spacing is vital. Raft flexibility predominantly governs the deformed shape of the system. Under lateral loading, trivial effect of pile spacing on horizontal pile load sharing is observed, while at higher lateral displacement usage of larger pile length becomes redundant.

The water retention curve is an important constitutive relation routinely incorporated into numerical stimulations of production from gas hydrate reservoirs. It has significant influences on the physical and mechanical behaviors of unsaturated sediments. In most existing simulators, the water retention curve models are assumed to be independent of hydrate saturation, or coefficients are incorporated that consider the influence of hydrate, which may not accurately and fully characterize the water retention curves of hydrate-bearing sediments. This paper proposes a new model that can be used to determine water retention curves for hydrate-bearing sediments. The model was developed based on the original van Genuchten model, introducing a gas-entry pressure and residual water saturation as a function of hydrate saturation. The proposed model was calibrated against several experimental and numerical data sets. Good agreement between the experimental data and simulated results indicates that the proposed model captures the essential water retention curve characteristics of hydrate-bearing sediments, such as the residual water saturation and gas-entry pressure.

The Weibull-distribution–based probabilistic damage model is widely used to represent the mesoscopic strength distribution of rock. However, it is unable to adequately describe the entire rock failure process. In this paper, based on the maximum entropy theory, a new probabilistic damage model is proposed to characterize the entire rock failure process. The reasonableness of this new model was verified against experimental data. The physical meaning of entropy, which is used to describe rock failure, was analyzed using the statistical method. It is demonstrated that when entropy is used to build the probabilistic damage model, an increase in the entropy corresponds to an increase in the rock damage, and the maximum entropy corresponds to the maximum probability of damage occurring. Thus, it is reasonable to use the maximum entropy to establish a probabilistic damage model. Finally, the effects of the constraint conditions on this maximum-entropy-based model are discussed.

Study on the mitigation of debris flows and rockfalls is a very challenging topic due to complex moving and impacting mechanisms. A large-scale physical model is preferred by researchers in the study of debris flow and rockfall, because large-scale tests can duplicate major phenomena of natural geohazard events. In the design of a large-scale physical model, how to initiate or release a certain volume of debris material or a giant rock boulder is the key technical issue. In current large-scale models for debris flow research, debris material is normally released from a reservoir with a trap door located at the upper end of the flowing path. It has been found that the door-opening methods utilized in models can interfere with the motions of the generated debris flows. In this paper, a new fast door-opening method is introduced in detail. This method has been implemented in a large-scale physical model built in Hong Kong to study the impacts of rockfalls and debris flows on a flexible barrier. With the utilization of this novel door-opening method, the impact tests of rock boulders, dry granular flows, and debris flows were successfully performed. From the observations of the impact tests, the unbalanced resisting forces and the disturbance from the door were avoided. The successes of large-scale tests using different testing materials demonstrated that the new fast door-opening method can be further utilized in a physical modeling study of geohazards.

A finite-difference modeling was performed to investigate the liquefaction-induced uplift of an underground structure. The liquefaction-induced uplift of a 5 m diameter underground structure buried at a depth of 5.5 m was analyzed. The soil was modeled using the elastic-perfectly plastic Mohr–Coulomb model by incorporating the Finn–Byrne pore-pressure formulation. The pore pressure and uplift response of the underground structure obtained using sinusoidal input motion were validated by comparing centrifuge tests and numerical analysis results reported in the literature. The responses obtained using a scaled-up 2015 Nepal-Gorkha earthquake accelerogram and equivalent sinusoidal motion were compared and were found to be similar. Further parametric analysis was carried out to study the effect of the characteristics of the input motion on the uplift of the structure. The numerical results revealed that the primary reason for the uplift of the underground structure was the generation of pore pressure at the invert of the structure. It also was found that significant liquefaction-induced uplift displacement of the underground structure occurred for input motion with a peak input acceleration more than $0.22g$ and a frequency less than 0.75 Hz.

Grouting is frequently used to prevent water-inrush disasters in tunnels and underground engineering. However, complex groundwater environment can significantly influence the grouting effect, especially the antiwashout performance. To accurately evaluate the antiwashout performance of grouting materials, a new method is proposed to design specific measurement devices and measurement procedures. This new method allows direct simulation of the injection of grout into water with different flow velocities. Thus, the antiwashout performance of grout under the scouring and diluting action of flowing water can be evaluated quantitatively. The grout retention ratio (GRR) is defined to quantitatively determine the antiwashout performance of grout. Taking widely used cement–sodium silicate (C-S) grout and polyurethane grout as test samples, a series of tests with different mixing ratios and water flow velocity conditions was carried out. The feasibility of the new method was evaluated in these tests and the influences of the grout mixing ratio and water flow velocity on the GRR were discussed. By analyzing the experimental data, a polynomial regression model for C-S grout was derived to provide guidance for optimizing its antiwashout performance. Compared with C-S grout, polyurethane grout has much better antiwashout performance at higher water flow velocity, indicating its advantage in controlling the flow rate of water and preventing water-inrush disasters.

A lack of joint specimens with the same natural surface morphology has limited detailed experimental study of the shearing performances of joints. In this technical note, we propose a way to batch-produce rock joints with the same natural surfaces by way of three-dimensional (3D) optical scanning of original rock joint specimens to gain their digitally natural geometry and then 3D rigid engraving. We also present a method for characterizing the shear damage of a natural rock joint. Manufacturing practice for sandstone, marble, and granite joints demonstrates its advantages in reliable precision for joint surface geometry and high efficiency for joint fabrication. At the same time, direct shear tests for the manufactured rock joint specimens indicate that the engraved rock joint can provide stable experimental results. Further analysis of microwearing damage to engraved natural rock joints after shear tests show that the wearing damage to natural rock joints under direct shear testing mainly happens at some local zones with high positive dip angles. These production examinations and experimental certifications indicate that our method can overcome the “bottleneck” difficulty in insufficient joint specimens with the same natural surface morphologies for experimental study, and provide a new way to quantitatively assess a joint’s shear damage.

Soil thrust acts as a reaction force that enables an off-road tracked vehicle to overcome motion resistance and move the vehicle forward. Thus, the estimation of soil thrust for a track system has great importance in the design and path planning of off-road tracked vehicles. In this study, we first present analytical solutions for the soil thrust of clayey ground by performing an upper-bound limit analysis, as a basis for the assessment of the tractive performance of off-road tracked vehicles. Two different failure modes (block and triangular wedge) are possible on a soil-track interface, and the resultant soil thrust is determined as an upper-bound solution for the most critical failure according to the principle of least action modes (i.e., the least-upper-bound solution). Based on the upper-bound solutions, parametric studies were conducted to explore the effects of the shear strength of clayey ground, geometry of a track system, and the weight of the vehicle on soil thrust. For practical use, this study also offers a soil thrust design chart for a single-track system.

For some two-layered slopes subjected to the surcharge load, the soil mass undergoes rotational or translational movement. Thus, the conventional failure mechanism of homogeneous slopes is no longer applicable. To overcome the difficulty in stability assessment of two-layered slopes, a rotational-translational failure mechanism is proposed, and it is composed of rigid blocks rotating around the center point or sliding along the layered boundary. Meanwhile, two rotational failure mechanisms (face and base failures) are modified to evaluate the stability of two-layered slopes with upper bound limit analysis. Case studies and stability charts are carried out on two-layered slopes with various surcharge loads, slope geometries, and soil strengths. The results are useful to address advantages and application differences of the three failure mechanisms in engineering practice. In addition, the comparison with the Spencer method indicates that the upper bound solution of the rotational or rotational-translational mechanism in different conditions is more rigorous because of the lower factor of safety and the more reasonable slip surface.