International Journal of Geomechanics

There are various methods for reinforcing a railway track subgrade, but the greater challenge lies in improving an existing railway track in the least possible time with minimum disruption to rail traffic. Micropiles can provide an alternative solution for the improvement of existing railway tracks. The application of micropiles does not require blocking of rail traffic or dismantling of existing tracks. This study aims to evaluate the effectiveness of micropiles as a ground improvement technique for existing railway tracks. Micropiles were tested on two types of soil–clay and silt. A complete parametric study varying the geometrical configurations of micropiles was conducted using the FEM. Variation of micropile geometry in terms of, for example, diameter, length, spacing, and angle of inclination was also discussed. The results of FEM analysis were further utilized to train a genetic programming (GP) model. Empirical equations for the prediction of track displacement were drawn up using GP analysis; the behavior of tracks for different reinforcement conditions was also discussed. The resultant equations can also be effectively used for predicting track performance under given conditions.

Moist tamping (MT) is likely the most common sample preparation technique used in the study of tailings, owing to the ability of MT to produce loose, contractive specimens. While the preparation of such loose samples to identify the critical state line is well established, MT is also frequently used to study trends of tailings behavior across a range of states. Preparation of dense states using MT may require significant compactive effort, the effects of which have not been studied in detail. A series of triaxial compression tests were carried out on two gradations of tailings to assess the effect of compacting to dense initial states on the resulting undrained shear behavior. This indicated that the process of compacting a specimen to a dense initial state may result in significant increases to peak undrained shear strength compared to samples prepared initially loose that achieved the same state at a range of consolidation stresses. This outcome emphasizes the importance of applying caution during sample preparation to avoid potentially unrealistic peak undrained strengths occurring during testing that are artifacts of the preparation procedure and unlikely to be relevant to in situ conditions.

Arch dam abutment stability is regarded as a prominent part of designing concrete dams. In the present study, the seismic stability of the rock wedges in the foundation of the concrete arch dams is studied using limit state and finite-element methods. For this purpose, a double-curvature arch dam (the Bakhtiari dam), is taken into consideration. Each abutment has six wedges. The finite-element model (FEM) includes the dam, reservoir, wedges, and the rest of the foundation. The dam abutment seismic safety is analyzed using the time history analysis along with the Londe method. Subsequently, the wedges in the proximity of the critical state are identified. Afterward, the analysis of the critical wedges’ joints has been conducted via FEM, and the damage propagation in the dam body has been investigated. Moreover, the effects of the grout curtain efficiency, hazard level, and foundation flexibility on the nonlinear behavior of the arch dam with integrated foundation and foundation with joints are scrutinized. The outcomes reveal the remarkable effect of joints considered in the foundation on the dam behavior.

This paper aims to study the three-dimensional (3D) tunnel heading pressure of twin circular tunnels in a drained cohesive–frictional soil using a stability factor approach and finite-element limit analysis (FELA). The primary concept adopted will be the use of a conventional equation that is similar to the traditional bearing capacity factors (e.g., N_c, N_s, and N_γ) in Terzaghi’s bearing capacity equation. For various spacing ratios (S/D) between the tunnels, the stability of the tunnels is expressed in terms of nondimensional tunnel stability factors (e.g., F_c, F_s, and F_γ), which are functions of the depth ratio (C/D) and soil internal friction angle (ϕ). For conciseness, the results will be presented in charts and tables with the tunnel stability factors that used the rigorous FELA upper (UB) and lower bound (LB) solutions.

This study presents a simplified analytical design and numerical modeling of the pile group foundation for a wind turbine tower on multilayered soil. The pile group foundation obtained from the analytical design is modified to study the possibility of developing an innovative foundation configuration through biomimicry of the tree root system. The initial dimensions of the pile group foundation were obtained from the analytical geotechnical design, which resulted in 40 closed-end steel pipe piles of length 30 m arranged along the circumferences with radii 5.3 and 6.7 m. The pile cap is considered to have a radius of 7.5 m and a thickness of 1.2 m. These dimensions were used to develop a three-dimensional numerical model of the pile group foundation in GROUP software. Inspired by the load-carrying mechanism of the natural foundation, i.e., tree root system, the initial model was modified by altering the inclination of the outer piles, which resulted in an additional ten models. The results from GROUP indicated that the differential settlement and rotation are the lowest for the model with outer piles inclined at an alternate 60° and 45° with the horizontal plane. Further, the pile configuration was modified by arranging the same number of piles along three circumferences keeping the length of the pile constant. This configuration was modified by changing the inclination of middle and outermost piles, which resulted in additional 14 models. These models were analyzed in GROUP, and the results showed that the lowest differential settlement and rotation are observed in the model with piles inclined at an angle of 90°/90°/60° (innermost/middle/outermost pile) and 90°/90°/45°. Moreover, the stress, axial force, shear force, and bending moment were obtained from GROUP for each configuration, which can be used to ensure the structural safety of the foundation.

In conventional consolidation theories, a boundary is simulated as either perfectly pervious or impervious, where the time-dependent drainage capacity at the boundary is ignored. Using the time-dependent impeded boundary condition, it is very difficult to derive solutions analytically. A continuous drainage boundary is proposed in this investigation to characterize the time-dependent drainage behavior at the boundary. The interface parameter is of physical significance, which depends on the properties of both the consolidating soil and the adjacent medium. In this study, two methods are developed to estimate the interface parameter. Back-analysis can be conducted to evaluate the interface parameter based on the variations of excess pore-water pressure from experimental or field measurements. Alternatively, an empirical approach is derived to correlate the interface parameter with the ratio of the coefficient of consolidation and the thickness ratio between adjacent media. The solution is further employed to analyze layered soils with a horizontal drain. It is found that both the plane of maximum excess pore-water pressure and the optimal position of horizontal drain move toward the boundary with a lower drainage capacity with time. A simplified design chart is finally presented to optimize the layout of the horizontal drain in layered clay–drain systems.

Based on the self-developed axisymmetric test apparatus for hollow cylinder specimens, an experimental study on the thermal consolidation behavior of saturated silty clay with different overconsolidation ratios under different confining pressures and temperature paths was carried out. The evolution of pore-water pressure caused by undrained heating/cooling and thermal volumetric strain caused by drained consolidation was analyzed, which is related to confining pressure, temperature path, and overconsolidation ratio. In addition, the experimental results were simulated based on a modified thermodynamic constitutive model proposed by the author. The model captures the important aspects of thermo-hydro-mechanical coupling characteristics of saturated soil. By comparing the model with the experimental results, its ability to describe the thermal consolidation behavior of saturated silty clay under different temperature paths was verified.

Traditional earth pressure theories are based on the assumption of semi-infinite space. The existence of intermediate principal stress and soil arching effects is ignored, which will cause significant errors in the application of finite width soil. This study introduced the intermediate principal stress based on the twin-shear unified strength theory; the stress deflection caused by soil arching and the uniform surcharge on the retained soil surface were also considered. An improved calculation method for cohesive soil’s lateral earth pressure coefficient, an analytical solution for active earth pressure of finite width soil, the resultant force, and its action point were proposed. The lateral earth pressure distribution of finite width cohesive soil was studied by calculation examples. In addition, relevant parameters were also analyzed. The results indicate that due to the influence of the intermediate principal stress and soil arching effects, the resultant active earth pressure is lower than the traditional method. The lateral earth pressure coefficient gradually increases with the depth, but it is always lower than the traditional one. As the soil width increases, the resultant force action point presents a nonlinear trend that first decreases, then rises, and stabilizes. The proposed method was compared with the previous studies and got better results; it can provide a new idea for estimating the active earth pressure of finite width soil.

It is essential to know the topography–soil–structure interaction (TSSI) for buildings adjacent to slopes. In the present study, the seismic response prediction of two midrise buildings located in the vicinity of slopes was evaluated using 3D numerical simulations to examine the effects of topography–structure–soil–structure interaction (TSSSI). The performance of the slope topography without any buildings and responses of a single building (TSSI cases) near the crest was also simulated. This study includes nonlinearity in both soils (through the elastoplastic hysteretic constitutive model with anisotropic hardening, the HSS model) and buildings (using the inelastic hinges). The effects of parameters such as the slope geometry (angle and height), soil type, and the distance of two adjacent buildings were considered based on the average of seven earthquake records. Results showed that in TSSSI cases, displacements, and shear forces varied greatly in the lower stories compared with the TSSI and soil–structure interaction (SSI) models. Besides, the neighboring impacts must be taken into consideration for a distance between buildings less than the foundation’s dimensions in the same plane.

In this study, the bearing capacity coefficients N_γ were calculated for strip footings by considering different friction angles along the soil–footing interface (δ) using the numerical algorithm based on the method of stress characteristic lines. Changes in the geometric properties of plastic and nonplastic regions were also evaluated under the influence of footing roughness for different internal friction angles. The results revealed that the N_γ coefficient gradually increases with increasing roughness. At least 85% of the N_γ coefficient was achieved by mobilizing only 50% of the footing roughness. In addition, the magnitudes of N_γ under a full roughness state for φ > 25° were obtained, which were almost twice that of the smooth footing case. It was found that increasing the values of φ and δ/φ resulted in the expansion of the width and depth of plastic and nonplastic domains. Similar to the observed trend for the N_γ coefficient, the major part of the maximum width and depth values of plastic and nonplastic regions obtained under complete roughness state were provided for φ ≥ 0.5. By increasing both φ and δ/φ, the curvature of the outer boundary of the nonplastic curved wedge increases and affects a deeper layer of the soil. Further, the emergence point of the curve tends toward the footing edge, therefore the wedge covering a wider part of the footing base.

Three-dimensional (3D) modeling of soil–geogrid interaction is a numerical challenge when simulating reinforced soil systems. Modeling the soil–geogrid interaction requires an appropriate consideration of the geogrid geometry, the materials’ model, and the interface properties. In this study, a series of 3D models were developed using the finite-element method (FEM) to investigate the response of geogrid under confined and unconfined conditions focusing on geogrid tensile stiffness effects. In this regard, a modeling approach for the geogrids whose configuration is complex was proposed. The validity of the models was also justified by the good agreement between calculated numerical results and measured experimental data. Moreover, particular emphasis was placed on visualizing the soil–geogrid interaction and load transfer mechanisms. The load transfer mechanisms were embodied not only through the distributions of displacement, strain, and tensile force along the geogrid but also through the displacement fields inside the soil domain. The results from two series of tests showed that the proposed approach was capable of reasonably capturing the geogrid response, whether under unconfined or soil-confined conditions.

Guidelines on the response analysis of rocking shallow foundations considering material uncertainties under earthquake loading are not available in any great detail. In this study, a reliability analysis of a bridge pier with a rocking shallow foundation (RSF) was performed, using the Monte Carlo simulation technique, applied on the performance functions of the bridge pier, approximated using the response surface method. The soil–structure interaction was modeled using a beam on the nonlinear Winkler foundation approach. Two ground motions, corresponding to moderate and strong seismic intensities, were used in the study. Four model configurations of the bridge pier–RSF system were considered, and the probabilities of failure were evaluated, corresponding to three performance levels. It was concluded that the probabilities of failure changed drastically with the performance level of the bridge pier. The results showed that the bridge pier–RSF system suffered minimal damage during the moderate earthquake and was effective in enhancing seismic performance during the strong earthquake.

This paper documents the development of low stress and fracture zones in the core of the 177-m-high Masjed-E-Soleyman rockfill dam––which has a clay core and was built in a relatively narrow canyon––using three-dimensional (3D) numerical modeling and analyses during both the construction and impounding of the dam. The analysis was based on effective stress parameters, which enabled the computation of pore water pressures in the core caused by the construction and impounding loadings. The analysis was successfully verified by comparing the results to data measured by dam instruments. Two criteria for assessing the low stress and fracture zones in the core were utilized: (1) zones in which the minimum effective principal stresses were under tension conditions, irrespective of the water-content-related characteristics of the core; and (2) zones in which combinations of the stress ratio and liquidity index––based on the principles of critical-state soil mechanics––caused the soil to fracture. The results of the analyses indicated that the core of the dam in its upper elevations and in the vicinity of the abutments suffered tensile stresses and fracturing, based on both criteria. This finding compares favorably with what happened to the prototype in the field after impounding.

In this paper, upper bound limit analysis that includes a horizontal pseudostatic seismic force is used for the first time to obtain the limit load on strip footings seated on cohesive-frictional soils reinforced with a single geosynthetic layer. Reinforcement tensile rupture and sliding failure modes for the geosynthetic layer are included in the analyses. Results of analyses are presented as optimum reinforcement depths and a bearing capacity equation with a single term and different bearing capacity factors for tensile rupture and sliding failure modes. The bearing capacity factors are presented in tables and capture the combined influence of the reinforcement strength, soil frictional strength and cohesion, soil unit weight, footing geometry, uniform surcharge, and magnitude of horizontal ground acceleration.

This paper investigates the effect of the soil moisture evaporation rate on the soil water retention curve (SWRC) of clays obtained using the high-capacity tensiometer (HCT) technique and following the continuous drying (dynamic) method. SWRC measurements, with and without soil moisture evaporation rate control, were carried out on reconstituted London clay specimens using 12 performance-improved HCTs recently developed at the University of Warwick. Furthermore, the HCTs' performance in terms of the maximum attainable suction (s_max) and maximum measurement duration (t_max) was evaluated. Moreover, the suitability of a curve-fitting-based model, available in the literature, for attaining the entire retention curve (beyond the capacity of HCTs) was evaluated. The SWRCs for the tests with a controlled evaporation rate were found to generally exhibit higher suction at a given water content, hence inducing air-entry values that were on average 16% higher than those obtained from tests without evaporation rate control. It was also found that for suction in excess of 2 MPa, the curve-fitting-based model predictions of data obtained from tests with a controlled evaporation rate exhibited significantly lower suction at a given water content than those without evaporation rate control, suggesting that such curve fitting correlations should be used with caution.

In general, the traditional Sarma method is two-dimensional (2D). In nature, slopes are three-dimensional (3D) problems. However, the 3D Sarma method is rarely proposed and used in rock slope engineering. In this paper, the 3D Sarma method will be used to study the stability of a slope with an intercolumn force of nonzero at the nonfree face boundary. The relationship between the safety factor (F_s) and the horizontal earthquake acceleration coefficient will be determined by an optimization method and F_s will be obtained when the horizontal earthquake acceleration coefficient equals zero. Two examples will be illustrated to validate the feasibility of the proposed method. The results obtained by the proposed method agreed well with those obtained using other methods.

Comprehending the rainfall infiltration process in rockfill is essential for estimating the strength and unsaturated wetting deformation behaviors of rock structures. This paper presents an experimental study on the rainfall infiltration characteristics and water-retention capacity of a weakly weathered granite rockfill using a newly developed instrument that can generate artificial rainfalls with controllable intensities (0–500 mm/h) and sufficient uniformities. A group of rainfall infiltration tests and drainage tests were carried out using rockfill specimens with a diameter of 600 mm and a height of 1,200 mm. Results show that rainfall infiltration, which is characterized by the downward movement of the wetting front, experiences an unsaturated process even under heavy rainfall conditions. Both the steady-infiltration water content and the velocity of the wetting front increase nonlinearly with increasing rainfall intensity. The unsaturated hydraulic conductivity of rockfill material can be acceptably estimated by classic models for medium-to-fine grained soils. In addition, the drainage process in rockfill is divided into two stages of quick-drainage and slow-drainage by the turning water content. The quick-drainage stage typically lasts for a brief time (e.g., a few minutes), followed by the slow-drainage stage with small decreases (about 2%–3%) in water content. In the end, the concept of water transmission in medium-to-large pores and water retention in small pores were used to characterize the rainfall infiltration and drainage characteristics. The rockfill possesses good seepage/drainage qualities owing to the excellent connectivity of relatively large pores, whereas the water-retention capacity is mainly attributed to the small pores.

Multiple hazards such as rainfall, earthquake, and excavation may occur simultaneously, and the stability (factor of safety) and deformation (movement) behaviors must be investigated to prevent loss of life and properties. In this study, the stability and deformation behaviors of earth slopes subjected to the individual and simultaneous occurrence of these events are investigated using a coupled Geotechnical–Hydrological finite-element method (FEM). First, the finite-element model was validated against a case history and a widely used limit-equilibrium method (LEM) considering site-specific soil properties and rainfall records. The shape and the size of the critical failure surface obtained from the field investigation coincided well with those calculated using FEM and LEM. Also, the predicted onset of slope failure (after eight days of rainfall) coincided well with the real-time occurrence of the slope failure. The validated finite-element model was then used to predict the stability and deformation responses of earth slopes subjected to several possible scenarios, including individual and simultaneous occurrences of these events. The rainfall–excavation scenario indicated that the slope would have failed two days before the recorded time if the slope had a vertical cut width of 4.25 m. The rainfall–earthquake hazard scenario caused the slope to move horizontally by 799 mm. The parametric study conducted by varying the friction angle of the slope soil by ± one standard deviation (STD) with 10% covariance showed that the slope would have failed one day later and two days prior to the mean friction angle, respectively, when subjected to rainfall. Also, varying the friction angle by +1 STD and −1 STD failed the slope for 0.5 m above and 0.4 m below the cut width for the slope with mean friction angle when subjected to excavation, respectively. Further, the percent increase in the horizontal movement of the slope soil with friction angle by +1 STD and −1 STD compared to mean friction angle was 56% and 18%, respectively, when subjected to earthquake.

Various multimegawatt capacity offshore wind turbines (OWTs) are constructed globally to fulfill increasing energy demand. Many of these structures have already been and will continue to be constructed in seismically active areas. Hence, these structures are at probable risk of an earthquake. The dynamic behavior of monopile-supported various multimegawatt OWTs in liquefiable sand deposit under combined action of operational and seismic loads are investigated in this study. A three-dimensional beam on a nonlinear Winkler foundation model is developed in OpenSees. The monopile and the tower are modeled as a linear Euler–Bernoulli beam. The lateral and vertical pile–soil interfacing behavior is modeled by using p-y, t-z, and q-z spring elements. The strong ground motion is utilized as free-field displacement at spring supports. The effect of the vertical component of seismic motion on the performance of the OWT structure in liquefied soil is examined.

The time-dependent behavior of soft and problematic soils is a major concern as constructional fill geomaterial. Several researchers have been utilizing different admixture to stabilize soft soil. In this study, fly ash (FA) has been used as an admixture to investigate the time-dependent behavior of Indian montmorillonitic clay (BC) by considering its elastic-viscoplastic behavior. A series of oedometer tests have been carried out on the test specimens at different FA contents. Microstructural arrangement of the BC–FA matrix was investigated using scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The results indicate that the addition of FA increases the compression stiffness of the matrix and that the unloading–reloading index decrease continuously. Time-dependent parameters, that is, creep coefficient, swelling coefficient, and strain limit, are significantly reduced by the addition of FA. Results show that hydrated FA contents, which encounters BC soil, produce calcium silicate hydrate (C-S-H) gel due to pozzolanic reaction and form a dense BC–FA matrix. Microscopic study exhibits the contribution of specific minerals toward its elastic, plastic, and viscous behaviors. The results show that the constitutive elastic-viscoplastic model considering swelling (EVPS model) works well in predicting the long-term compressibility behavior of FA-blended soft soils.

An experimental study was performed to investigate the effects of an acid solution on the mechanical strength and the microstructure of biocemented sand. The tests were performed on small triaxial samples extracted from a large-scale model. An acid solution composed of hydrochloric acid and Tris buffer with an initial pH of 6.6 was injected in the triaxial apparatus in different amounts. The changes of the physical and mechanical properties of the sample were studied afterwards. Triaxial drained tests with constant confining pressures were performed on the chemically treated samples in order to determine the remaining strength of the samples. Moreover, several scanning electron microscope (SEM) and X-ray microtomography observations were performed on small subsamples in order to identify the changes in the microstructure due to the chemical dissolution. The experimental results point out that the strength of the treated specimens decreases dramatically compared with that of the initial untreated specimens. Typically, a 50% strength reduction has been found for 10% of total calcite dissolution. Furthermore, the microstructural observations have shown uniform calcite dissolution at the pore scale (no preferential locations). The calcite crystal structures were damaged randomly by the chemical solution. A reduction of the spatial densities and sizes of these crystals were found from SEM and X-ray microtomography observations. Overall, no hysteretic effects were observed on the mechanical (strength) and microstructural (contact surface area) properties between the biocementation and dissolution paths.

Sewer infrastructures that are backfilled with available onsite expansive soils may be exposed to damages due to seasonal ground movements. Therefore, for deep excavated trenches located in nontrafficable areas, the suitability of utilizing mixtures of recycled materials as alternative backfilling materials with lower sensitivity to moisture variations was studied. Extensive environmental and geotechnical testing programs were carried out on the performance of four proposed blends comprising different proportions of recycled glass, plastic, and tire aggregates in order to determine an optimum mix design. First, potential environmental hazards of the individual recycled materials were assessed. The investigation was advanced by the development of an application-specific geotechnical testing program utilizing geomechanics theories and methods associated with granular materials. The program included the determination of the maximum dry density achieved using a sand-rain technique (SRT) to simulate the real-life backfilling procedure of excavated trenches, and the determination of the compressibility of the blends using a modified oedometer test. In addition, the potential for the migration of finer particles within the recycled material blends and the possible long-term settlement of the backfilled area were studied. The environmental test results showed that the blends could safely be used as fill materials. The SRT test results revealed that the dry density increased as the moisture content and the height of drop increased and the tire content of the mixture decreased. At moisture contents ≥ 15%, the maximum dry densities obtained through the SRT and the standard Proctor compaction were close, achieving relative densities greater than 80%. Furthermore, by simulating precipitation, inconsiderable segregation of particles was observed in the proposed blends. Based on the results of the developed experimental program, two blends were recommended as the optimum mixtures.

Abandoned ash pond beds have been considered for their reclamation through the construction of lightweight structures. Under static conditions, an ash pond bed can sustain these structures but its stability must be ascertained under seismic conditions. This paper presents the results of geotechnical characterization and dynamic properties of pond ash samples that were collected from three different locations ranging from the inflow point to the outflow point of the ash pond of the Ropar thermal power plant (India). Strain-controlled cyclic triaxial tests were conducted on collected samples, considering the effect of various parameters, such as shear-strain amplitude, confining pressure, frequency, and density. The shear modulus of the coarser pond ash sample near the inflow was observed to be greater than that of the finer pond ash near the outflow. The shear-strain amplitude and frequency of cyclic loading increases with a decrease in the shear modulus. The damping ratio is greater in the case of finer ash. Moreover, damping ratio increases with an increase in strain amplitude and frequency of loading. The dynamic behavior of the pond ash sample was also compared with that of sand. The area near the inflow of the ash pond, where there is coarser ash was found to be more suitable for reclamation of the ash pond bed under seismic conditions.

The dilatancy equation plays an important role in establishing the elastoplastic model for sand–gravel composites. However, the equation is not comprehensive in its considerations. In this paper, experimental investigations of the dilatancy behaviors of saturated sand–gravel composites are carried out through a series of drained triaxial compression tests. The influence of density as well as confining pressure on the dilatancy characteristics of sand–gravel composites is analyzed, and a nonlinear relationship between the stress ratio η and the dilatancy d is suggested. A new and practical dilatancy equation that can accurately model the stress–dilatancy relationship of sand–gravel composites during the whole process of shearing is established. The equation is applicable whether the material is strain softening or strain hardening. The improved accuracy of the proposed equation in describing the stress–dilatancy relationship of sand–gravel composites is highlighted through comparison to the predictions of five widely used dilatancy equations. In addition, the generality of the proposed dilatancy equation is verified through analyzing the stress–dilatancy relations of six rockfill and gravelly materials found in published literature.

This article is concerned with the design of steel baffles embedded in soil to contain fallen boulders rolling down a hill slope, with the buried segment of the baffles cast into concrete. Analytical solutions presented in the form of closed-form expressions based on a standardized static model enable optimized design solutions to be found readily. Dynamic testing of baffles has been undertaken to verify the accuracy of the proposed analytical model. Numerical simulations employing the program LS-DYNA have also been undertaken to extend the database of test results to track the trends and to provide further support of the calibrated model. This article presents the finding that the required depth of embedment of the baffle to achieve “long pile” behavior is scale-dependent, contrary to the commonly held notion based on observations from studies that have been undertaken on laterally loaded piles. The proposed analytical model, which is ideally suited to the design of steel baffles, will result in significant cost savings while maintaining acceptable performance.

A void can be formed or expanded in a weakly cemented in situ soil because of multiple reasons such as abandoned old pipes and eroding of fine particles caused by pipe leakage. Such void formation can develop into various directions and amounts of volumes, which can influence the engineering behavior of in situ soils. In this study, a distinct element method was employed to quantitatively investigate the effect of such void formation on the strength of cemented soil. An empty capsule was vertically or horizontally embedded in cemented sand for void simulation, which was tested for its unconfined compressive strength (UCS). The experiment result was used to calibrate the built-in bonded particle model in PFC^2D computer code. The effect of void formation direction and volume on the strength of cemented soils was numerically investigated in terms of UCS. Consequently, the UCS of cemented sand significantly decreased up to 64% as embedded capsules changed from the vertical to the horizontal direction. The UCS of cemented sand linearly decreased down to 63.2% as the number of capsules increased from 1 to 4. The decrease in strength was because the void area disconnected the shear bands—explicitly represented as broken bonds—and trapped the distributed stress inside the layers between capsules, resulting in a lower strength of the specimens.

Computed seismic responses of an earth dam founded on alluvial deposits are compared with the instrumented data. Three numerical models, in increasing order of complexity, are used to analyze the dam response. The computed results from each of the three numerical models are compared with the instrumented data at the dam site. The computer programs used are SHAKE, SHAKEM, and FLAC. These computer programs are widely used for seismic analysis in dam engineering practice. Vibration characteristics of the dam based on measured wave forms and numerical models are included. Practical implications of the results in dam engineering practice are included.

In this paper, the limit-state and direct probability-based design responses of modern geotechnical codes are characterized according to parametric analyses of geotechnical uncertainty. The reliability levels (β) of the limit-state design (LSD) responses are compared with the prescribed minimum target reliability indices (β_T,min) of the codes for a case study that involves the design of an embedded sheet pile structure subjected to water pressure, seepage pressure, and no retained earth pressure. The effect of soil uncertainty, represented by the variabilities of the effective soil friction and the soil unit weight, on the direct probabilistic-based design responses, is analyzed at small- and high-reliability levels (0 ≤ β ≤ 5). The results show that the reliability levels of the LSD responses of the North American and European codes do not fulfill the prescribed β_T,min for the overturning and structural failure limit-states. In contrast, for the hydraulic heave limit-state, the prescribed β_T,min of the North American codes are widely exceeded. The effects of the uncertainties of the effective soil friction COV_ϕ′ and the soil unit weight COV_γ on the normalized embedment depth (D/H) and the normalized maximum structural bending moment (M_max/γH³) are also explored relative to the principles of the North American and European codes.

This work presents the implementation of a simplified three-dimensional Hoek–Brown strength criterion using a multiyield-surface plasticity approach. The adopted three-dimensional simplification of the strength criterion accounts for the intermediate principal stress influence, maintaining the simplicity in the numerical implementation. This criterion corresponds to a paraboloid surface of circular cross section in the principal stress space. The introduction of multiple yield surfaces allows for a smooth definition of the nonlinear stress–strain behavior of the material. In addition, a kinematic hardening rule is adopted, allowing yield surfaces to translate with loading, enabling a hysteretic and path-dependent stress–strain response.

This research paper aims to comprehensively investigate the effectiveness and sensitivity of fiber inclusion on the behavior of a clayey soil subjected to desiccation. A series of laboratory experiments including desiccation shrinkage and cracking tests were performed for both unreinforced and reinforced specimens. Polypropylene fiber was used in this study to reinforce the soil, with different fiber contents (FCs; 0.1%, 0.2%, and 0.3%) and fiber lengths (FLs; 6, 12, and 18 mm). The results showed that the desiccation cracking behavior of the soil was significantly affected by the addition of fibers. Desiccation cracking was found to be reduced effectively with increasing the FC; however, interestingly the effect of varying FL was not significant. In addition, the relevant underlying mechanism is discussed.

A common conflict of objectives for shield tunneling is to provide sufficient support pressure to maintain the stability of the tunnel face while avoiding blow-out of the tunnel face. Slurry-induced hydraulic fracturing, which is an important cause of blow-out failure in slurry-type shield tunneling, is investigated in this study. A fracture initiation mechanism for soft soils is developed and the fracturing pressure is described using a combined shear and tensile failure criteria within the cavity expansion theory framework. A slurry-induced fracture propagation model, coupled with the fracture initiation mechanism, is then proposed for predicting the fracture length and growth rate in front of tunnel face. The model is successfully applied to test data from the literature, and used in a parametric analysis. The results show that a fracture may easily extend to the ground surface when tunneling in ground with low strength parameters or shallow depth, and hydraulic fracture can be mitigated by using a high-density slurry. Finally, some design charts are provided to guide engineers in selecting a reasonable range of slurry pressure during shield tunneling, thus mitigating the risks of blow-out as well as maintaining face stability.