2015

Permanent URI for this collectionhttps://hdl.handle.net/1807/67556

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Centrifuge modelling of an instrumented free-fall sphere for measurement of undrained strength in fine-grained soils
(Canadian Science Publishing, 2015-11-17) Morton, John Philip; O'Loughlin, Conleth; White, David
This paper describes centrifuge tests in which a model free-fall sphere was allowed to free-fall in water before dynamically embedding within reconstituted samples of kaolin clay and two offshore natural clays. Instrumentation within the sphere measured accelerations along three orthogonal axes. The resultant acceleration was used to calculate sphere velocities and displacements. This allowed the penetration resistance acting on the sphere to be expressed in terms of a single capacity factor that captures soil resistance from both shearing and drag, and varies uniquely with the non-Newtonian Reynolds number. Undrained shear strength profiles obtained from a simple inverse analysis of the acceleration data show good agreement with those obtained using conventional push-in penetrometer tests.
A laboratory test study on effect of freeze–thaw cycling on strength and hydraulic conductivity of high water content stabilized dredged sediments
(Canadian Science Publishing, 2015-12-21) Makusa, Gregory Paul; Mácsik, Josef; Holm, Göran; Knutsson, Sven
Dredged sediments with initial water content between 200% and 400% were treated with single and composite binders. Samples were subjected to open and semi-closed freeze-thaw (f-t) cycles to investigate the impact of f-t cycling on hydraulic conductivity (HC) and unconfined compressive strength (UCS). A grace period (GP) for thaw consolidation is included to assess healing potential of the affected stabilized mass. The findings of this study show that the impact of f-t cycles depend on initially achieved UCS and HC values prior to the f-t cycling and time of testing after f-t cycles. The HC of specimens with initially UCS value of 87 kPa increased with number of f-t cycles. The UCS values decreased in the range of 50%-80% when specimens were tested directly after the thaw period and values decreased in the range of 14%-60% when specimens were tested at the end of GP. The HC of specimens with initial UCS value of 299 kPa remained almost the same. These samples experienced permanent loss in the UCS values, irrespective of time of testing. Detrimental effects of the freezing action on the UCS were greater under semi-closed than open freezing conditions.
The Influence of Structure on the Behavior of a Saturated Clayey Loess
(Canadian Science Publishing, 2015-11-12) Xu, Ling; Coop, Matthew
An intensive experimental investigation by means of triaxial and oedometer tests was performed on a clayey loess that was retrieved from two depths at a location on the southern Chinese Loess Plateau. Intact and reconstituted samples were used to identify the effects of the natural structure on soil behavior in saturated conditions. The behavior in compression was clearly affected by structure with the intact samples reaching well-defined gross yield points outside the intrinsic compression line of the reconstituted soil, after which the compression paths converged towards the intrinsic compression lines, behavior which is consistent with destructuration. However, very high stresses were required to give complete convergence. Similarly the triaxial tests that were carried out at lower stress levels also did not give convergence of the critical states so that different critical state lines could be defined for the intact and reconstituted soils. This was consistent with qualitative observations from scanning electron micrographs that natural elements of fabric and possibly bonding persisted even after triaxial shearing. The effects of structure at the two depths on the compression and shearing behavior were slightly larger for the shallower samples. Despite the very different genesis of the soils, it was found that similar frameworks could be applied to those used for sedimentary clays and that the degree of structure was equivalent to a clay of medium sensitivity.
Modelling Long Term Hydraulic Conductivity Behaviour of Zero Valent Iron Column Tests for PRB Design
(Canadian Science Publishing, 2015-12-22) Moraci, Nicola; Ielo, Domenico; Bilardi, Stefania; Calabrò, Paolo Salvatore
In this paper a numerical model to simulate the hydraulic conductivity reduction observed during long term laboratory column tests is proposed. The column tests are carried out in order to study dissolved heavy metals removal by using granular zero valent iron (ZVI). The proposed model is also used to analyse the main causes of hydraulic conductivity reduction observed during laboratory column tests. Expansive iron corrosion, precipitation of reaction products and gas formation are the processes considered in the proposed model. Numerical simulations results show that in order to reproduce the hydraulic behaviour of the experimental systems the change of pores geometry due to expansive iron corrosion and precipitation of reaction products, which determines a possible stop of gas bubbles, should be considered. Furthermore, model results show that only a small percentage of the iron available is corroded during the tests (from 0.4 to 1.9 %). According to the model, the average diameter of gas bubbles that better fit the experimental results is variable between 0.16 and 0.19 mm. While, assuming gas absence (or its possible escape) higher values of iron corrosion rate should be considered in order to fit the experimental results.
3D finite element analysis of the behaviour of cross passage between cast-iron tunnels
(Canadian Science Publishing, 2015-12-03) Li, Zili; Soga, Kenichi; Wright, Peter
The behaviour of cast-iron cross passages in London Underground was investigated using 3D finite element models. Unlike the behaviour of a full tunnel ring, the structural integrity of a tunnel cross passage opening relies on the support from adjacent linings. In clayey soils, the opening may deform further as the soil stiffness changes from undrained to drained conditions. The degradation of circumferential bolts and trackbed may also lead to further tunnel movement. A parametric study was conducted to examine the influence of soil stiffness and structural components (e.g. bolts and lintel) on the structural integrity of a tunnel opening. Results show that a lintel effectively transfers the load above the opening to the adjacent linings, and its distortion affects tunnel deformation significantly. If a lintel is not present, both bolts and friction between tunnel segments provide shear resistance to the lining deformation at the tunnel opening against soil loading. The results are compared to the field observations made at a critical cross passage in one of the London Underground tunnels. The findings contributed to identifying the critical deformation mechanisms of cast-iron tunnel cross passages, which can be useful during inspection of such structures.
Interpretation of the loading/wetting behaviour of compacted soils within the MPK framework: Part II Dynamic compaction
(Canadian Science Publishing, 2015-11-03) Kodikara, Jayantha; Islam, Tanvirul; Rajeev, Pathmanathan
Dynamic compaction is commonly used to construct structural fills for various geo-infrastructures. Current practice is to specify a minimum dry density and moisture content criterion to be used in the field on the basis of Proctor compaction carried out in the laboratory. Nonetheless, we still do not have practical methods for predicting the compacted clay behaviour under expected mechanical and environmental loadings. Current theories are difficult to apply in practice due to difficulty in determining the necessary parameters. In this paper, the recently developed MPK framework is extended to cover dynamically compacted soils, with significant supporting experimental evidence. Two types of soils are used; lightly reactive kaolin and reactive Merri Creek clay. Since the compaction stress was unknown for dynamic compaction, recompression of soil specimens from compacted soil was used to establish the Loading Wetting State Boundary Surface (LWSBS). Independent tests showed that the framework can predict well the behaviour of compacted soils under loading/unloading and yielding, collapse during wetting, change of loading yield stress after wetting, and swelling pressure development during constrained wetting. The value of the approach is that the testing methods are straight-forward, do not require specialised equipment and the testing times are much shorter. In addition, the uncertainty that laboratory dynamic compaction may not relate directly to field roller compaction can be addressed with the developed framework. Soil specimens obtained from field soil pads compacted by actual rollers can be used to establish the LWSBS. This information will allow the prediction of the likely behaviour of field compacted fills under expected environmental and mechanical loadings under one-dimensional conditions. Extension to triaxial conditions would require further experimental work and theoretical modelling.
Interpretation of the loading/wetting behaviour of compacted soils within the MPK framework: Part I Static compaction
(Canadian Science Publishing, 2015-11-03) Islam, Tanvirul; Kodikara, Jayantha
Depending on the state paths, loading/wetting of compacted unsaturated soils can exhibit complex volumetric behaviour such as swelling, collapse, collapse followed by swelling, swelling followed by collapse, and swelling pressure development. Microscopically, these behaviours arise from complex interactions among applied stresses, air-water pressure deficit or suction at the water menisci, moisture content or degree of saturation in the voids and the nature of the micro- and macro-soil aggregates of compacted soils that depend on the level of suction (Alonso et al., 1999). While significant advances have been made in modelling the hydromechanical behaviour of compacted unsaturated soils taking these interactions into account, input parameter determination requires advanced testing equipment and the testing processes can be very time-consuming. Recently, a relatively simple and practical framework within the void ratio-moisture ratio (volume of water/volume of solids)-net stress space (referred to as the MPK framework) was proposed by Kodikara (2012) to explain/predict these state paths. A desirable feature of this framework is that it identifies a direct link between the well-known compaction curve and the compacted soil constitutive behaviour. The current paper presents a comprehensive series of tests on statically-compacted soils, the results of which are in close agreement with this framework. Two soil types, namely lightly reactive kaolin and more reactive clay, referred to as Merri Creek soil, were used in the testing. The soils were prepared with different moisture contents from the dry state and statically compacted at constant water content to obtain void ratio-moisture ratio-net stress constitutive surfaces, as well as soil specimens for state path tests. The state path test results of yielding under loading, collapse under wetting, swelling pressure development and change in yield pressure due to wetting are explained within this framework. In addition, some published data on a silty soil mixture were also analysed, highlighting that the framework is valid, regardless of the degree of reactivity of the soil. Suction was not measured in the authors’ experiments, as it was not required to explain the above state paths according to this framework. However, it is recognised that suction is the conjugate state variable to the moisture content. Therefore, in future experiments, suction will be measured and its role will be fully explained within the framework, adding more generality.
Depth-independent cone penetration mechanism by a DEM-based stress normalization approach
(Canadian Science Publishing, 2015-11-12) Liu, Su; Wang, Jianfeng
Abstract A two dimensional discrete element model of driven piles in crushable sand was developed and validated against laboratory data. Numerical experiments are conducted to investigate the effects of initial sample porosity, particle crushability, initial stress state, the ratio of pile diameter to median particle diameter and the ratio of model width to pile diameter on the pile penetration behavior. A new stress normalization method is adopted to synthesize the data at different driven depth from the simulations. The normalized vertical and horizontal stress fields surrounding the pile show invariable pattern of stress distribution, suggesting a unique penetration mechanism independent of the penetration depth. The validity of the DEM simulation results is verified by comparing the stress distributions to those observed from calibration chamber tests on model pile installation in sands. Key Words: pile penetration; crushable sand; particle breakage; DEM simulation; stress normalization
Influence of cross-correlation between soil parameters on probability of failure of simple cohesive and c-phi slopes
(Canadian Science Publishing, 2015-11-12) Javankhoshdel, Sina; Bathurst, Richard J.
The paper focuses on the calculation of probability of failure of simple unreinforced slopes and the influence of the magnitude of cross-correlation between soil parameters on numerical outcomes. A general closed-form solution for cohesive slopes with cross-correlation between cohesion and unit weight was investigated and results compared with cases without cross-correlation. Negative cross-correlations between cohesion and friction angle and positive cross-correlations between cohesion and unit weight, and friction angle and unit weight were considered in the current study. The factors of safety and probabilities of failure for the slopes with uncorrelated soil properties were obtained using probabilistic slope stability charts previously reported by the writers. Results for cohesive soil slopes and positive cross-correlation between cohesion and unit weight are shown to decrease probability of failure. Probability of failure also decreased for increasing negative cross-correlation between cohesion and friction angle, and increasing positive correlation between cohesion and unit weight, and friction angle and unit weight. Probabilistic slope stability charts presented by the writers in an earlier publication are extended to include c-Φ soil slopes with and without cross-correlation between soil input parameters. An important outcome of the work presented here is that cross-correlation between random values of soil properties can reduce the probability of failure for simple slope cases. Hence, previous probabilistic charts by the writers for simple soil slopes with uncorrelated soil properties are conservative (safe) for design. This study also provides one explanation why slope stability analyses using uncorrelated soil properties can predict unreasonably high probabilities of failure when conventional estimates of factor of safety suggest a stable slope.
Preliminary geotechnical assessment of the potential use of mixtures of soil and acid mine drainage neutralisation sludge as material for the moisture retention layer of covers with capillary barrier effects
(Canadian Science Publishing, 2015-11-15) Mbonimpa, Mamert; Bouda, Médard; Demers, Isabelle; Benzaazoua, Mostafa; Bois, Denis; Gagnon, Mario
Lime treatment of acid mine drainage (AMD) generates sludge that is commonly stored in ponds for dewatering. The use of soil-aged sludge-based mixtures for mine site rehabilitation can allow emptying existing basins, extending their storage capacity, reducing the volume of borrow soil pit required for mine site rehabilitation, and consequently reducing the mine footprint. The authors investigated the geotechnical properties of silty soil–sludge mixtures (SSM) as possible component of covers with capillary barrier effects (CCBE) to prevent AMD generation from mine waste. SSM with 10, 15, 20, and 25% sludge (= wet sludge mass/wet soil mass) were studied. Two water contents were considered for each of the mixture components: 175 and 200% for the sludge and 7.5 and 12.5% for the soil. Results indicated that saturated hydraulic conductivity values ksat were in the range of 10-5 cm/s for the soil and SSM mixtures at void ratios ranging from 0.28 to 0.53, with values slightly decreasing when β was increased from 0 % to 25%. The air entry value (AEV) increased from 20 kPa for the soil alone to 35 kPa for the SSM with β= 25%. These values of ksat and AEV are comparable to those of materials used in the moisture retention layers of existing efficient CCBE. However, the volumetric shrinkage increased from about 2% for the soil alone to values ranging between 24 and 32% for the SSM with β = 25%, depending on the initial water contents of the components. Tools are provided to estimate to which extent the use of sludge in SSM can reduce the volume of borrow natural soil required for a moisture retention layer of a CCBE.
Analysis of consolidation with constant rate of displacement
(Canadian Science Publishing, 2015-10-20) Muir Wood, David
The `constant rate of strain' consolidation test has been widely used for several decades to provide a continuous load:displacement response. An exact theoretical solution can be obtained for this problem. Two other solution techniques have pedagogic advantage in their simplicity, their ability to clarify the phases of response of the consolidating sample, and their ability to be extended to incorporate additional details of material response or testing configuration. The parabolic isochrone technique imposes a particular mode shape on the isochrones at all times. Treating the sample as a single system, and applying the boundary conditions at the system level, the governing equation becomes an ordinary differential equation. For more elaborate soil properties or experimental procedures a finite difference description of the problem is readily programmed and solved. These solution techniques are used to illustrate the importance of distinguishing between the observed response of the system - the soil specimen under test - and the behaviour of the soil elements that make up this system. Examples are given of erroneous conclusions that might be drawn if this distinction is not recognised.
Improved image-based deformation measurement for geotechnical applications
(Canadian Science Publishing, 2015-10-19) Stanier, Sam A.; Blaber, Justin; Take, W. Andy; White, David
This paper describes and benchmarks a new implementation of image-based deformation measurement for geotechnical applications. The updated approach combines a range of advances in image analysis algorithms and techniques best suited to geotechnical applications. Performance benchmarking of the new approach has used a series of artificial images subjected to prescribed spatially-varying displacement fields. An improvement by at least a factor of ten in measurement precision is achieved relative to the most commonly used particle image velocimetry (PIV) approach for all deformation modes, including rigid body displacements, rotations and strains (compressive and shear). Lastly, an example analysis of a centrifuge model test is used to demonstrate the capabilities of the new approach. The strain field generated by penetration of a flat footing and an entrapped sand plug into an underlying clay layer is computed and compared for both the current and updated algorithms. This analysis demonstrates that the enhanced measurement precision improves the clarity of the interpretation.
Influence of freeze–thaw cycles on the performance of covers with capillary barrier effects made of crushed rock–bentonite mixtures to control oxygen migration
(Canadian Science Publishing, 2015-10-27) Boulanger-Martel, Vincent; Bussière, Bruno; Côté, Jean; Mbonimpa, Mamert
In temperate climates, covers with capillary barrier effects (CCBEs) are successfully used to control oxygen flux from reaching the covered potentially acid mine drainage (AMD) generating mine tailings. In northern climate, the more attractive option for mine site reclamation is insulation covers, which are designed to keep reactive materials frozen. This article suggests that CCBEs can simultaneously control oxygen migration and mine waste temperature to inhibit AMD generation. However, in northern conditions, where natural fine-grained materials needed for the CCBE moisture-retaining layer are not always available, soil–bentonite mixtures could be used instead. This laboratory study assessed in instrumented columns the effects of freeze–thaw cycles on the performance of three CCBEs made with crushed rock–bentonite mixtures. An oxygen diffusion test was developed to determine the effective diffusion coefficient of oxygen (De) and its sensitivity to freeze–thaw cycles. The results show good initial performance for the saturated CCBEs. However, the tested CCBEs are significantly affected by freeze–thaw cycles and have limited oxygen limiting ability.
In-situ monitoring of frost heave pressure during cross passage construction using ground freezing method
(Canadian Science Publishing, 2015-09-11) Han, Lei; Ye, Guan-lin; Li, Yuan-hai; Xia, Xiao-he; Wang, Jian-hua
The artificial ground freezing method has the dual effect of ground reinforcement and waterproof sealing, and the frozen curtain can be designed flexibly. It is widely used in the construction of cross passages for shield tunnels in soft ground with high groundwater levels. However, due to the lack of in-situ monitoring data, it remains difficult to determine the frost heave pressure acting upon a tunnel. In this study, based on the use of an anti-freezing pad-type earth pressure gauge, in-situ monitoring was carried out to measure the frost heave pressure acting upon tunnel segments during the construction of cross passages for the Shanghai Yangtze River Tunnel. The monitoring results show that the earth pressure acting upon the tunnel could decrease dramatically during freezing, and this kind of decrease can take place suddenly and unpredictably, which can be illustrated using the finite element method. The maximum measured frost heave pressure during freezing and cross passage excavation was approximately 0.2MPa, which was much smaller than the predicted value. Combining the distribution of temperature in the ground and construction countermeasures, the observed phenomena are mainly related to three factors: water migration during the freezing process, the tunnel-ground interaction and the countermeasure of pressure release holes. The tunnel showed a horizontal extension deformation, which was consistent with the releasing frost heave pressure acting upon it.
Collapsibility, composition, and microstructure of a loess in China
(Canadian Science Publishing, 2015-10-05) Liu, Zhen; Liu, Fengyin; Ma, Fuli; Wang, Mei; Bai, Xiaohong; Zheng, Yonglai; Yin, Hang; Zhang, Guoping
The collapse potential, mineralogy, microstructure, and particle morphology of a loess from the Loess Plateau, China, were characterized by double oedometer testing, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and image analysis to elucidate the origin of its collapse behavior. Results show that the loess is highly collapsible with a maximum collapse index of 6.7% at a vertical stress of ~200 kPa. The deposit contains both non-clay (i.e., quartz, albite, muscovite, and calcite) and clay (i.e., two chlorites) minerals. Microstructural, chemical, and image analyses indicate that interparticle calcite and clay cementation and silt particle morphology render the intact soil a metastable structure. Wetting-induced collapse is attributed to both primary and secondary microstructure features. The former is the abundance of weakly cemented, unsaturated, porous pure clay and clay-silt mixture aggregates whose slaking upon wetting initiates the overall structural collapse, while the latter consists of high porosity, unstable particle contacts, and clay coating on silt particles that act synergistically to augment the collapse. A conceptual microstructural model of a four-tiered hierarchy (i.e., primary clay and silt particles, clay aggregates and clay-coated silt particles, clay-silt mixture aggregates, and cemented aggregate matrix) is proposed to represent its structural characteristics and to account for its high collapsibility.
Field Study of Residual Forces Developed in PHC Pipe Piles
(Canadian Science Publishing, 2015-10-27) Kou, Hai-Lei; Chu, Jian; Guo, Wei; Zhang, Ming-Yi
A large-scale field testing program for the study of residual forces in Pre-stressed High-strength Concrete (PHC) pipe piles is presented in this paper. Five open-ended PHC pipe piles with 13 or 18 m embedded length were installed and used for static loading tests at a building site in Hangzhou, China. All the piles were instrumented with Fiber Bragg Grating (FBG) strain gauges. The residual forces in these piles were recorded during and after installation. The measured load transfer data along a pile during the static loading tests are reported. The effect of the residual forces on the interpretation of the load transfer behavior is discussed. The field data show that residual forces along the installed piles increase approximately exponentially to the neutral plane and then reduce towards the toe. The residual force decreases with time to a stable value after pile jacking due to the secondary interaction between the pile and the disturbed soil around the pile and other factors. The large residual forces along the PHC pipe piles affect significantly the evaluation of the pile load distributions, and thus the shaft and toe resistances. The conventional bearing capacity theory tends to overestimate the shaft resistance at positions above the neutral plane, and underestimate both the shaft resistance at positions below the neutral plane and the toe resistance for open-ended PHC pipe piles founded in stratified soils.
Investigations on corrosion and mechanical properties of a 20-year-old ground anchor exhumed at a power station site
(Canadian Science Publishing, 2015-09-03) Wang, Yujie; Ren, Aiwu; Wang, Yanshu; He, Jiquan; Chen, Zuyu
This paper presents the observed findings and laboratory test results of an anchor exhumed from Manwan hydropower station, China which was installed 20 years ago. The prestressed cables are 25.6 m long with a working load of 1000 kN. It consists of eight strands, and each strand consists of seven wires. The anchor was installed using the ‘single protection’ technique (i.e., the steel strands without greased sheath and was backfilled directly with cement mortar). The anchor was unearthed by excavating a 1.5 m  1.7 m tunnel. Visual inspection shows that the steel strands in the free and fixed lengths are basically stainless except for a few places where the grout failed to cover the anchor completely, thereby allowing direct contact of the strands with air. The magnitude of rebound of the tendon during the advancement of the tunnel face was simultaneously measured indicating a gradual release of bonding force, which was up to 62 % of the prestressed load. This shows that the existence of the bonding force is provided by the bonding between the strand and the grout, while this bonding does not exist in the ‘double protection’ system. The results of the mechanical test confirm that the tensile strengths in all the 33 steel wires exceed the requirement as specified by current Chinese Standard (NBS 1985). The concentrations of various chemicals also satisfy the requirements as specified by CSBTS (1999). The results of the X-ray Diffraction test show that the stains taken from the surface of the strand are composed of FeO and FeOOH, both being oxide products of iron. This shows that exposure of the material to air is an important condition to initiate corrosion. By following ASTM test procedure (ASTM International 1999), the average corrosion rate is found to be between 3-6  10-4 mm/year. This investigation generally supports the use of unprotected steel strands in rock anchor.
A new approach to improve soil-water characteristic curve to reduce variation in estimation of unsaturated permeability function
(Canadian Science Publishing, 2015-10-05) Rahimi, Arezoo; Rahardjo, Harianto
Unsaturated permeability function is often estimated from soil-water characteristic curve (SWCC) of a soil. A complete SWCC measurement can improve the estimation of unsaturated permeability function. In most laboratories, SWCC can be measured up to 100 kPa suction using a Tempe cell. However, the complete measurement of SWCC is an expensive and time-consuming task. Therefore, this paper presents a new approach to estimate SWCC data points beyond 100 kPa suction in order to complement the measured SWCC up to 100 kPa suction. The new SWCC is then used to estimate the unsaturated permeability function. The proposed approach uses knowledge of grain-size distribution curve and the measured SWCC data at 100 kPa suction to estimate the SWCC data points beyond 100 kPa suction. In order to verify the proposed procedure, SWCC tests were conducted over a wide range of suctions for coarse kaolin and a triaxial permeameter system was used to directly measure the unsaturated permeability of the coarse kaolin. The proposed procedure is found to reduce the variation between unsaturated permeability functions estimated by various estimation models.
Pore pressures induced by piezocone penetration
(Canadian Science Publishing, 2015-09-14) Chai, Jin Chun; Hossain, Md. Julfikar; Yuan, Dajun; Shen, Shuilong; Carter, John
The excess pore water pressures (u) induced by piezocone penetration and their dissipation around the cone have been investigated by laboratory model tests and theoretical/numerical analyses. Based on the test results, a method for predicting the cone penetration induced distribution of u has been proposed. By numerical analysis using the predicted initial distribution of u it has been demonstrated that dissipation of the pore water pressure measured at the shoulder of the cone (u2-type cone) is a two-dimensional (horizontal radial and vertical) process. By comparing the simulated and laboratory-measured 2D dissipation curves, a back-fitted coefficient of consolidation in the horizontal direction (ch) can be obtained. It has also been shown that a published method for estimating ch from measured non-standard dissipation curves (in which u2 increases initially and then reduces) results in values of ch that agree well with values of ch deduced from the 2D analysis.
Measuring Unsaturated Soil Deformations during Triaxial Testing Using A Photogrammetry-Based Method
(Canadian Science Publishing, 2015-08-10) Li, Lin; Zhang, Xiong; Chen, Gang; Lytton, Robert
When characterizing an unsaturated soil using the triaxial test apparatus, it is required to measure the soil deformation during loading. Recently, a photogrammetry-based method has been developed for total and localized volume change measurements on unsaturated soils during triaxial testing. In this study, more in-depth discussions on the photogrammetry-based method are addressed such as system setup, measurement procedure, accuracy self-check, data post-processing, and differences from the conventional image-based methods. Also, an application of the photogrammetry-based method on unsaturated soil deformation measurements is presented through a series of undrained triaxial tests with different loading paths. After testing, three-dimensional (3D) models of the tested soils at different loading steps were constructed based on the 3D coordinates of measurement targets on the soil surface. Clear barreling processes for soils during deviatoric loading were observed through the constructed 3D models at different axial strain levels. Soil volume changes and volumetric strain non-uniformities during isotropic and deviatoric loadings were extracted based upon detailed analyses on different soil layers. Through a full-field strain distribution analysis, a shear band evolution process was captured for the soil during deviatoric loading at a low confining stress. The photogrammetry-based method proved to be very powerful for in-depth soil deformation characteristics investigation.

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