Canadian Geotechnical Journal

Embankment dams primarily serve as structures for water containment. However, there is a growing demand for alternative usage, particularly from energy, mining, and forestry sectors. Allowing heavy vehicle transit on dam crests would improve access to the structures and the surrounding areas. Nonetheless, concerns arise regarding the safety and efficiency of embankment dams under heavy vehicle loads. There is a demand for innovative tools to facilitate decision-making processes by assessing the performance of embankment dams when subjected to heavy vehicle traffic. In the realm of unpaved road engineering, it is firmly established that the accumulation of permanent deformation under repeated loading is a key indicator of the performance of granular materials and soils. The paper aims to establish a model predicting the plastic strain rate in dam cores subjected to repeated heavy traffic, utilizing field measurements and laboratory testing of permanent deformation.

The genetic algorithm (GA) has been employed to perform the inversion considering the predominant modal curve in the dispersion image using the MASW technique. Using the stiffness matrix method (SMM) for a given layered medium, the predominant modal curve was generated by imposing the criterion of the maximum vertical displacement at the free surface. The current study involves the MASW based (i) synthetic experiments on four different geologic profiles using the finite elements (FE) analysis, and (ii) in-situ tests on five different sites. From the FE based MASW dispersion images, it is revealed that the modal plot in the dispersion image matches closely with the corresponding theoretically generated predominant modal curve which is obtained using the SMM. For the experimental data, the inverted geological profiles, derived from the observed predominant dispersion plot and with the usage of the SMM, were subsequently used for performing the wave propagation simulation using the FE analysis. The simulated dispersion images using the FE analysis showed a great match with the corresponding observed experimental images. It is found that the current predominant mode based GA inversion approach is more accurate as compared to the fundamental/multiple modes based inversion method.

Wind wave erosion on reservoir slopes is an important problem that seriously threatens the safety of reservoirs and soil conservation. This paper proposes a method of calculating wind wave erosion and bank failure based on the empirical formulas and the principle of bank slope stability, which simulates the evolution of bank slope stability in the process of wind wave erosion. Two seriously eroded bank slopes of Huangbizhuang Reservoir in Hebei Province, China, are selected as the study cases. The erosion and bank failure process are simulated between 1968 and 2020, and the computed width of wind wave induced failure of bank slopes is compared with that of field measured one. The result showed that the proposed method can simulate the amount of wind wave erosion of the reservoir bank and the process of bank failure well. The proposed method provides guidance for the design, protection, and reinforcement of bank slope.

The instability of quick clay is a contributing factor for landslides within Scandinavia, Canada, and Russia. The addition of salts into quick clay is known to improve the remoulded shear strength and liquid limit. In this study, the mixing of salts recycled from waste incineration fly ash into remoulded quick clay was studied and compared with the incorporation of pure salts for applications in salt wells and for excavation applications. The salts were added as solutions at low concentrations and as solids at high concentrations and stored for 1, 28 or 90 days before testing. Nearly all samples with added salts had a liquid limit that exceeded the water content and a remoulded shear strength, which exceeded 0.5 kPa. The pure potassium chloride had the largest effect, followed by the recycled chloride mixture with the highest concentration of K⁺. While a change in the geotechnical properties was immediately evident upon the mixing, the effect on the shear strength increased further with increasing storage time. The findings imply that the recycled salts may be used to improve the geotechnical properties of excavated soft clays during the handling and transport to landfills as a viable and low-emission alternative to cementitious binders.

In the present study free field and pile group models were experimented in a sloping ground using centrifuge modelling. A 2 × 2 pile group model was inserted in Toyoura sand and results were compared with that of free field model ground. Tapered sinusoidal waveform was inputted at a constant 1 Hz shaking frequency, whereas acceleration amplitude and shaking duration for the mainshocks were considered twice that of foreshocks and aftershocks. Two different seismic sequences with six shaking events were imparted to the model grounds to investigate the influence of slope and presence of pile group on sand reliquefaction behavior. The time history responses were recorded in the form of acceleration, excess pore pressure (EPP), bending moment, and lateral displacement and presented. The response indicates that sloping ground was stable under the action of foreshocks, whereas it collapsed during mainshocks, primarily due to liquefaction. The mainshock has transformed the gently inclined sloping ground to levelled ground model. Presence of slope has resulted in higher EPP response and bending moment values compared to levelled ground. GeoPIV analysis and visualization show the flow of sand particles from upside to downside due to lateral spreading at shallow depths that initiated the slope failure.

Crossing major active faults is often unavoidable for pipelines in earthquake-prone regions. This study explores a finite difference analytical solution for continuous pipelines subjected to normal faulting. The effectiveness of the proposed method is evaluated by comparing the calculated results with the data from centrifuge and full-scale laboratory tests. Combining with the Lasso regression machine learning technique, multi-parameter probabilistic risk assessment of pipelines can be performed to generate fragility curves. Probability density function (PDF) curves of normalized location of pipe failure are also computed. Results show that pipelines with a larger pipe wall thickness and a smaller pipe diameter buried at a shallower depth in soils with a lower elastic modulus are less prone to failure. The dominant failure mode of pipelines transits from local buckling to tensile strain, depending on the exceedance of critical diameter-to-thickness (D/t) ratio and burial depth. Greater attention should be placed on the failure mode of local buckling, and the normalized location of pipe failure moves away from the fault plane, when a shallow burial depth is selected. The fragility relations help to understand the relative vulnerability of pipelines with different parameters, and provide implications for the design and repair of pipelines in seismic-prone regions.

The water retention curve (WRC) and relative permeability are of great importance for performing saturated-unsaturated seepage analysis in soils. The bimodal WRC can better reflect the difference in water retention capacity between macropores and micropores in dual-porosity media compared with the unimodal WRC. Traditional testing methods cannot effectively measure the macropore region in municipal solid waste (MSW) as the water is discharged rapidly under gravity. In this study, an implementation framework for determining the bimodal WRCs and segmented relative permeabilities of MSW was proposed, and it was applied on the synthetic sample under sequential levels of overlying stresses. First, a calculation method for dividing the size boundaries of macropores and micropores was proposed from the perspective of energy analysis. Then, the computed tomography (CT) scanning combined with the maximal inscribed spheres (MIS) algorithm was used to obtain the WRC data for the macropore region, while the traditional pressure plate test was used to obtain the WRC data for the micropore region. Finally, a modified Van Genuchten model was proposed to fit these data to yield the bimodal WRCs, and the segmented relative permeabilities were further obtained. In addition, the bimodal probability density curves of pore-size distribution were obtained. A horizontal well draining test conducted at Tianziling landfill was used as the case study. The numerical results indicated that the bimodal WRC model performed better than the unimodal WRC model when simulating the draining test.

To evaluate the seepage erosion during the installation of suction caissons, this study developed a seepage erosion-interface shear test system to simulate the erosion phenomena. First, a parametric analysis was conducted to systematically investigate the effects of main factors (consolidation pressure, particle size distribution, inhomogeneous pressure) on sand erosion characterization, vertical deformation, seepage characterization, as well as the interface strength of suction caisson. Following this, interface shear tests were performed to compare and analyze the changes in caisson-sand interface strength before and after soil erosion. It is indicated that the soil erodibility initially increases and then decreases when increasing fine particles. Seepage channels form first at the bottom and become dominant near the caisson wall, enhancing the sand hydraulic conductivity. In addition, the soil inside the caisson is less stable under smaller consolidation pressure. After the erosion, changes in sand particle distributions significantly reduce the caisson-sand interface strength with the maximum reduction of approximately 50%. This study emphasizes the influence of seepage erosion on caisson in-service capacity, which needs more attention in practice.

This study adopts a flow-path energy-based approach to evaluate the effectiveness of mitigation measures for debris flows, focusing on the Favazzina area. Given the area's topography, which limits the construction of large debris flow barriers, permeable racks were chosen to dissipate the kinetic energy of the March 2005 landslide. The method continuously quantifies kinetic energy along the flow propagation path, enabling an assessment of how different rack configurations affect energy dissipation. By calculating the variation in the kinetic energy, the number and positioning of permeable racks were determined, considering both the location of exposed elements and the area's morphology. A two-phase smoothed particle hydrodynamics-finite difference numerical model was used to simulate the 2005 event and the presence of permeable racks placed at various sections. Results demonstrate the potential of the energy-based approach, as it allows for a rapid assessment of the energy content of a given landslide while guiding the selection of the most appropriate mitigation measure.

The soil behavior is rate-dependent as observed in the laboratory and field tests, and the undrained shear strength of clay is shown to increase with the strain rate in different shear modes. In practical situations, the foundations can be loaded at various time and rate scales, which will result in a wide range of magnitudes and inhomogeneous distribution of strain rates in the surrounding soil. This may cause difficulties in calculating the undrained bearing capacity of clay using the undrained shear strength from standard laboratory and field tests at a reference strain rate. In addition, the rate-dependent soil behavior will also affect the interpretation of in-situ tests conducted at different loading rates using procedures based on rate-independent soil models. This paper investigates the effect of loading rate on the undrained bearing capacity of clay using finite element analyses and a rate-dependent constitutive model, the MIT-SR, based on two classical problems in soil mechanics. Computed results suggest that the undrained bearing capacity of clay is strongly affected by the loading rate of foundations. It also highlights the difficulty to select appropriate undrained shear strength used for practical design, and the uncertainty to interpret field tests using bearing capacity factors.

This paper presents the geotechnical challenges experienced while excavating two shaft stations at the depths of 2490 m and 2550 m in highly stressed grounds, along with engineering solutions that effectively reduce exposure and risk associated with the excavations and help improve safety. Although proactive measures were implemented to ensure the successful construction of the 2490 shaft station, adverse stress conditions and a localized geological fault resulted in damage to the shaft concrete liner and significant overbreak of the station floor, leading to the bowling of the station floor. These unanticipated conditions resulted in project delays and increased risk for the operators working at the face. Based on detailed observations made while excavating the 2490 shaft station, instrumentation, and microseismic monitoring data, the methodology for excavating the 2550 shaft station was modified to mitigate the risk and increase safety. The modifications include reinforcing the shaft concrete liner, reducing the size of the initial shaft station blast, and pre-sinking and supporting the shaft below the station floor before the excavation of the shaft station, leading to cost savings and valuable insights into the geotechnical intricacies and excavation strategies essential to improving the safety of deep mining projects.

There is substantial evidence that crushable soils (e.g., sands, gravels, rockfills, etc.) undergo particle crushing upon shearing or over creeping. To investigate the evolution of grading and particle crushing of coarse-grained materials, a series of consolidated and drained triaxial shearing and creep tests were conducted on rockfills using a large-scale triaxial apparatus. The test data from the sieve analysis test, both before and after the triaxial tests, were subjected to a comprehensive qualitative and quantitative analysis of the variation of grading or breakage index. Research findings indicate a decrease in the percentage of coarser particles in the particle components of rockfills, accompanied by an increase in the amount of particle crushing upon shearing or over creeping. Furthermore, a series of empirical expressions were proposed through nonlinear fitting of test data to characterize the relationship between the breakage index and two variables (i.e., the normalized plastic work and mean effective stress) under various confining pressures and stress levels upon shearing or over creeping. These findings can provide a scientific basis for the design, construction, and maintenance of rockfill dams or high rockfill embankments in the practical engineering application.

The performance of bentonite slurry in submarine tunnel construction is significantly deteriorated by high-salinity seawater intrusion, increasing the risk of excavation face instability. This study investigates the incorporation of the biopolymer gellan gum (GG) into the bentonite slurry, as a high salt resistant and eco-friendly additive. The mechanisms underlying seawater-induced deterioration and GG-imparted salt resistance were analyzed. Results demonstrate that seawater increases the bleeding rate and American Petroleum Institute (API) fluid loss while reducing the apparent viscosity and yield stress of bentonite slurry, thereby compromising its shear-thinning properties. The addition of GG mitigates these negative effects and improves the colloidal stability, rheological properties, and filter cake quality of the slurry. With 1.2% GG, the 24 h bleeding rate of slurry was reduced from 86.4% to 0%, and a low-permeability filter cake (5.6 × 10⁻⁹ m/s) was rapidly formed, as confirmed by sand infiltration tests. Scanning electron microscopy analysis revealed that GG re-disperses seawater-induced bentonite platelet aggregates, while Fourier transform infrared spectroscopy results highlight the synergistic effects of cation consumption and gel filling by GG. This study highlights the potential of GG as a sustainable additive for bentonite slurry in marine geotechnical engineering applications.

Construction of solar panel piles in the Northern US is challenging due to soil freezing in winter. Freezing causes volumetric expansion and movement of soil along the pile applying a tangential heave stress (THS) that jacks up the pile. Relying on averaged values of the THS in building codes based on state/county conditions can lead to inaccurate THS estimates at specific project sites. In this study, the THS and adfreeze shear strength (AFSS) of soil samples collected from Indiana were measured using a temperature-controlled direct shear device at different temperatures and normal stresses. AFSS refers to the strength of the initial bond between the frozen soil and a foundation, while the THS is the residual upward force that remains after this bond breaks. This distinction is vital as the use of the THS can result in more economical and realistic foundations. A decrease in temperature led to an increase in the AFSS due to the amount of unfrozen water available at the interface. The obtained THSs were lower than those recommended by codes. In addition, it was found that the AFSS stems from the bonding of the ice to steel, while the THS results from friction. AFSS was not significantly influenced by the normal stress, while the THS increased with an increase in the normal stress.

This paper presents a comprehensive case study of the construction of a 10 km long large-span underwater tunnel under Taihu Lake using the cut-and-cover method. The main challenges for the design and construction of the tunnel are limiting soil deformation and tunnel settlement, controlling the groundwater table, improving the construction efficiency, and meeting the environmental requirements. The strategies to address these challenges were summarized, including a four-zone staged excavation configuration, the use of piles for tunnel settlement control, and the use of cofferdams and waterproof curtains for groundwater control. The effectiveness of these strategies was validated by field observations, including deformations and stresses of cofferdams, retaining wall deflections, vertical and horizontal ground movements, groundwater table variations, and tunnel settlements. The observation results indicated that the measured values were smaller than the design limits, and no damage or leakage was observed during construction. This case history provides a valuable reference for the design and construction of similar tunnels.

To address the challenges in adopting intelligent compaction as the primary method for compaction quality control, this study investigated methods for determining appropriate target intelligent compaction measurement values (ICMVs) for compaction quality control and strategies to manage compaction quality considering the ICMV variability. Field tests revealed that the mean compaction meter value (CMV) increased with the number of roller passes. However, a high coefficient of variation was observed across all roller passes, indicating significant local variability in compaction quality. A 5 m region of interest was determined optimal for correlating CMV with plate-load-test results and determining CMV for compaction quality management. Uniform compaction could not address localized variability in compaction quality. Detecting weak areas during the compaction process and concentrating efforts in these regions improved the uniformity of the compaction quality. This study provides valuable insights for ICMV-based compaction quality control, assisting construction supervisors in setting target ICMVs, and developing effective strategies.

The hydraulic-electric pulsed discharge（HEPD） rock-breaking technology can generate plasma channels in liquid media and shock waves from the plasma channels to break rocks. Since the HEPD rock-breaking technology involves a multi-physical field coupling rock-breaking mechanism that is difficult to describe, the theoretical modeling of this technology is less studied. In this paper, we analyze the HEPD rock-breaking process by combining numerical models and experiments and establish a multi-physics numerical HEPD simulation model, which realizes the whole process of HPED rock-breaking from the five-field coupling. The obtained numerical simulations and indoor experiments show that the HEPD process is divided into three phases: the breakdown channel formation phase, the plasma channel formation phase, and the plasma shockwave bursting phase. With the increase of liquid medium conductivity, the rock's maximum penetration depth decreases, the rock's maximum damage depth increases, and the trend of rock crushing pits appears to decrease. The larger the liquid medium breakdown energy consumption, the faster the electric breakdown in the liquid medium is generated, which reduces the breakdown delay. When the liquid medium conductivity increases from 0.0125S/m to 5S/m, the liquid medium breakdown energy consumption increases by 13.87% and the breakdown delay decreases by 13.74%.

Capillary barrier systems (CBS) offer a sustainable solution supporting sustainable drainage systems (SuDS) to prevent urban flooding: The occurrence of flooding in urban areas is increasing in response to more intense precipitation, changes in land use that increase runoff (e.g., reduction of green spaces), and reduced water retention of soils. The need for adaptation to the impacts of extreme weather extends to buried assets (e.g., utilities, pavement subbases, and foundations) that are vulnerable to deterioration due to shrink–swell behaviour. Combined SuDS and capillary barriers offer a solution to these challenges. Here, small-scale (110 mm diameter, 1 m length) column experiments are used to test capillary barrier systems, also modelled in HYDRUS 1-D, to consider the impact of relative grain size between the two constituent materials, the use of geosynthetic filter fabrics, and the thickness of the water retention layer on combined sustainable drainage-capillary barrier system (SuDS-CBS) performance under a range of storm inflows. Recycled materials including crushed concrete and water treatment residual (a waste product of the water treatment industry) are shown to be effective for use in SuDS-CBS. Laboratory experiments and numerical modelling demonstrate the importance of antecedent moisture conditions for determining the performance of a SuDS-CBS during rainstorm events.

Contaminated sediment treatment typically requires both dehydration and decontamination, which are normally investigated separately. By integrating vacuum electro-osmosis with electrokinetic remediation technologies, this study demonstrates the potential for simultaneous consolidation and remediation. A novel experiment system for vacuum electro-osmosis was developed to treat sediments with varying initial copper concentrations. The electrical characteristics indicated that both vacuum pressure and copper ions significantly affected the maintenance of electrical conductivity. Vacuum membrane compression increased effective potential by 5–6 V, and there was a clear positive correlation between initial currents and initial concentration of contaminants. The consolidation properties revealed that as contaminants and moisture were removed, the pores between soil particles increased, causing sudden subsidence in the middle area. Higher initial concentration contributed to higher ultimate drainage volumes, peaking at 1950.25 mL, and more evenly distributed settlement. Copper content measurements suggested that excessively low or high initial concentrations of copper diminished remediation effectiveness, with the highest anodic decontamination efficiency at 60%, albeit at the detriment of the cathode region. Copper fractions analysis revealed that weak acid-extractable and water-soluble fractions accounted for over 85% of total copper, predominantly influencing consolidation and remediation.

The nonlinear stress–strain behaviour of stiff clays and weak rocks at small and medium strains may be a critical consideration in the design of geotechnical structures. Empirical methods have been developed for estimating the maximum shear modulus and the normalised shear modulus reduction with strain of fine-grained soils. These are usually expressed as functions of the void ratio (or specific volume) and average effective (confining) stress, based on results from laboratory tests. However, the fidelity of these equations has not been widely evaluated in situ. This paper describes the use of in situ measurements from an instrumented embankment to calculate the operational in situ shear modulus of the underlying stiff clays and weathered mudstones at medium and large strains. It is shown that the shear modulus at very small strain of the weathered clays increased linearly with depth, consistent with empirical equations. The gradient of the normalised, nonlinear stiffnesses of the clays were comparable with those measured in laboratory tests of fine-grained soils, at a range of strains. However, the values for the reference strain, where the maximum shear modulus reduces by 50%, were lower than was predicted by the empirical equations.

Effective stabilization of expansive soils remains a challenge for transportation infrastructure. In line with the United Nations’ sustainability goals, most research on eco-friendly stabilizers is still in its early stages, focusing primarily on laboratory evaluations. This study aims to evaluate the efficacy of alkali-activated calcined clay-based geopolymers (CCBGPs) and investigate the most effective minerals contributing to its stabilization of expansive soils. Four locally available clays were used to synthesize CCBGPs, and based on unconfined compressive strength, two of them were selected for further stabilization of expansive soils. The treated soils underwent comprehensive engineering, microstructural, and mineralogical analyses. A machine learning (ML)-based regression model was developed and tested to examine the effects of CCBGP and soil mineralogy on engineering performance of the treated soils. Engineering tests on treated specimens showed improved performance with increasing CCBGP dosage and curing periods, while microstructural and mineralogical analyses revealed physical and chemical interactions with soil particles that enhanced engineering properties. The ML model identified kaolinite as the most influential factor, which enhanced geopolymerization by forming more binder gel, and improved engineering properties. Overall, the research indicated that selection of kaolinite-rich, locally available CCBGPs could serve as sustainable source for improving expansive soils in transportation infrastructure.

The constant volume behavior of sands is substantially influenced by the initial stress anisotropy. This research aims to investigate the stress anisotropy effect by conducting a series of bidirectional direct simple shear tests that can apply initial shear stress on a sample in different directions during the consolidation stage. The experimental program provides insights into the impacts of the initial shear stress and the subsequent principal stress rotation (PSR) on some critical aspects of soil behavior, including the onset of instability, brittleness index, phase transformation, and the critical state line. The findings show that the onset of instability and the brittleness indices are significantly dependent on the initial stress anisotropy. In contrast, the critical state and phase transformation lines are not influenced by the initial anisotropy of the stress state, even in the presence of PSR. Furthermore, the study gives particular attention to the non-coaxiality between the major principal stress and strain rates to illustrate how the non-coaxiality decreases with increasing shear strain. The research also explores the non-coaxiality between the resultant shear stress and shear strain rate and suggests a predictive flow rule accordingly. The results reveal that a substantial level of non-coaxiality may exist between the resultant shear stress and the shear strain rate.

Embankment widening alongside an existing embankment causes additional stress and differential settlement on the foundation beneath the embankment, which may have adverse effects on pavements. The settlement profiles of the existing and widened foundations beneath an embankment are governed by several geometric and physical parameters related to embankment widening. An accurate settlement evaluation method is essential for the determination of an appropriate ground improvement technique. In this paper, a simplified method for predicting the settlement of the soft foundation induced by embankment widening is proposed. A validated finite element method model was first employed to quantify the effect of geometric parameters and soil properties on the settlement characteristics. Furthermore, a simplified model based on the bi-Gaussian function was developed to illustrate the settlement profiles. The results obtained by the proposed model are in good agreement with previously reported centrifuge test results and a generated numerical database, demonstrating that the proposed model has satisfactory accuracy. The developed prediction model offers an alternative approach for the preliminary design of embankment widening.