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 Acta Geotechnica   [SJR: 1.818]   [H-I: 22]   [7 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1861-1133 - ISSN (Online) 1861-1125    Published by Springer-Verlag  [2352 journals]
• Field testing of one-way and two-way cyclic lateral responses of single
and jet-grouting reinforced piles in soft clay
• Authors: Ben He; Lizhong Wang; Yi Hong
Pages: 1021 - 1034
PubDate: 2017-10-01
DOI: 10.1007/s11440-016-0515-z
Issue No: Vol. 12, No. 5 (2017)

• Pile reinforcement mechanism of soil slopes
• Authors: Ga Zhang; Liping Wang; Yaliang Wang
Pages: 1035 - 1046
Abstract: Stabilizing piles are widely used as an effective and economic reinforcement approach for slopes. Reasonable designs of pile reinforcement depend on the understanding of reinforcement mechanism of slopes. A series of centrifuge model tests were conducted on the pile-reinforced slopes and corresponding unreinforced slopes under self-weight and vertical loading conditions. The deformation of the slope was measured using image-based analysis and employed to investigate the pile reinforcement mechanism. The test results showed that the piles significantly reduced the deformation and changed the deformation distribution of the slope, and prevented the failure occurred in the unreinforced slope. The pile influence zone was determined according to the inflection points on the distribution curves of horizontal displacement, which comprehensively described the features of the pile–slope interaction and the characteristics of reinforced slopes. The concepts of anti-shear effect and compression effect were proposed to quantitatively describe the restriction features of the piles on the deformation of the slope, namely the reduction in the shear deformation and the increase in the compression deformation, respectively. The pile reinforcement effect mainly occurred in the pile influence zone and decreased with increasing distance from the piles. There was a dominated compression effect in the vicinities of the piles. The compression effect developed upwards in the slope with a transmission to the anti-shear effect. The anti-shear effect became significantly dominated near the slip surface and prevented the failure that occurred in the unreinforced slope.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0543-3
Issue No: Vol. 12, No. 5 (2017)

• Vertical bearing capacity behaviour of single T-shaped soil–cement
column in soft ground: laboratory modelling, field test, and calculation
• Authors: Yaolin Yi; Songyu Liu; Anand J. Puppala; Peisheng Xi
Pages: 1077 - 1088
Abstract: The T-shaped soil–cement column is a variable-diameter column, which has an enlarged column cap at the shallow depth, resulting in the column shape being analogous to the letter “T”. In this study, 1-g laboratory and full-scale field loading tests were employed to investigate the vertical bearing capacity behaviour of a single T-shaped column in soft ground. Pressure cells were set in a T-shaped column in the field to measure the vertical column stress above and below the column cap during the loading test. After the loading test, several columns were excavated to investigate their failure modes. The results indicated that, since the section area of the column cap was remarkably higher than that of the deep-depth column, the stress concentration occurred in the deep-depth column just under the cap, leading to column failure. Based on this failure mode, a simplified method was proposed to estimate the ultimate bearing capacity of a single T-shaped column; the comparison of estimated and measured results indicated the applicability of the proposed method.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0555-z
Issue No: Vol. 12, No. 5 (2017)

• Failure modes and bearing capacity of strip footings on soft ground
reinforced by floating stone columns
• Authors: Haizuo Zhou; Yu Diao; Gang Zheng; Jie Han; Rui Jia
Pages: 1089 - 1103
Abstract: This study evaluates the failure modes and the bearing capacity of soft ground reinforced by a group of floating stone columns. A finite difference method was adopted to analyze the performance of reinforced ground under strip footings subjected to a vertical load. The investigation was carried out by varying the aspect ratio of the reinforced zone, the area replacement ratio, and the surface surcharge. General shear failure of the reinforced ground was investigated numerically without the surcharge. The results show the existence of an effective length of the columns for the bearing capacity factors N c and N γ. When certain surcharge was applied, the failure mode of the reinforced ground changed from the general shear failure to the block failure. The aspect ratio of the reinforced zone and the area replacement ratio also contributed to this failure mode transition. A counterintuitive trend of the bearing capacity factor N q can be justified with a shift in the critical failure mode. An upper-bound limit method based on the general shear failure mode was presented, and the results agree well with those of the previous studies of reinforced ground. Equivalent properties based on the area-weighted average of the stone columns and clay parameters were used to convert the individual column model to an equivalent area model. The numerical model produced reasonable equivalent properties. Finally, a theoretical method based on the comparison of the analytical equations for different failure modes was developed for engineering design. Good agreement was found between the theoretical and numerical results for the critical failure mode and its corresponding bearing capacity factors.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0535-3
Issue No: Vol. 12, No. 5 (2017)

• Pressuremeter test parameters of a compacted illitic soil under thermal
cycling
• Authors: H. Eslami; S. Rosin-Paumier; A. Abdallah; F. Masrouri
Pages: 1105 - 1118
Abstract: The incorporation of heat exchangers in geostructures changes the temperature of the adjacent soil, raising important issues concerning the effect of temperature variations on hydro-mechanical soil behaviour. The objective of this paper is to improve the understanding and quantification of the impact of temperature variation on the bearing capacity of thermo-active piles. Currently, the design of deep foundations is based on the results of in situ penetrometer or pressuremeter tests. However, there are no published data on the effect of temperature on in situ soil parameters, preventing the specific assessment of the behaviour of thermo-active piles. In this study, an experimental device is developed to perform mini-pressuremeter tests under controlled laboratory conditions. Mini-pressuremeter tests are performed on an illitic soil in a thermo-regulated metre-scale container subjected to temperatures from 1 to 40 °C. The results reveal a slight decrease in the pressuremeter modulus (E p) and a significant decrease in the creep pressure (p f) and limit pressure (p l) with increasing temperature. The results also reveal the reversibility of this effect during a heating–cooling cycle throughout the investigated temperature range, whereas the effect of a cooling–heating cycle was only partially reversible. In the case of several thermal cycles, the effect of the first cycle on the soil parameters is decisive.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0552-2
Issue No: Vol. 12, No. 5 (2017)

• Advance in the penetrometer test formulation to estimate allowable
pressure in granular soils
• Authors: Jesús Díaz-Curiel; Sandra Rueda-Quintero; Bárbara Biosca; Georgina Doñate-Matilla
Pages: 1119 - 1127
Abstract: In this paper, we present a modification of the existing mathematical formulation used to obtain the allowable bearing pressure from dynamic penetration tests in order to extend its applicability to the design of shallow foundations. The conventional relationships adopted to obtain the allowable bearing pressure from penetrometer tests have a discontinuous gradient, and they are limited to a depth less than the footing width. The aim of this work was to find a relationship that permits the estimation of this pressure in cohesionless soils, from the results of dynamic probing super heavy tests, through a single non-piecewise and continuous relationship that remains valid up to depths several times the footing width. This equation was applied as part of the geomechanical characterization survey undertaken for the construction of an elevated helipad in the centre of the Iberian Peninsula. The survey results were considered satisfactory, and the construction was completed without structural problems.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0565-x
Issue No: Vol. 12, No. 5 (2017)

• Seasonal effects on geophysical–geotechnical relationships and their
implications for electrical resistivity tomography monitoring of slopes
• Authors: R. M. Hen-Jones; P. N. Hughes; R. A. Stirling; S. Glendinning; J. E. Chambers; D. A. Gunn; Y. J. Cui
Pages: 1159 - 1173
Abstract: Current assessments of slope stability rely on point sensors, the results of which are often difficult to interpret, have relatively high costs and do not provide large-area coverage. A new system is under development, based on integrated geophysical–geotechnical sensors to monitor groundwater conditions via electrical resistivity tomography. So that this system can provide end users with reliable information, it is essential that the relationships between resistivity, shear strength, suction and water content are fully resolved, particularly where soils undergo significant cycles of drying and wetting, with associated soil fabric changes. This paper presents a study to establish these relationships for a remoulded clay taken from a test site in Northumberland, UK. A rigorous testing programme has been undertaken, integrating the results of multi-scalar laboratory and field experiments, comparing two-point and four-point resistivity testing methods. Shear strength and water content were investigated using standard methods, whilst a soil water retention curve was derived using a WP4 dewpoint potentiometer. To simulate seasonal effects, drying and wetting cycles were imposed on prepared soil specimens. Results indicated an inverse power relationship between resistivity and water content with limited hysteresis between drying and wetting cycles. Soil resistivity at lower water contents was, however, observed to increase with ongoing seasonal cycling. Linear hysteretic relationships were established between undrained shear strength and water content, principally affected by two mechanisms: soil fabric deterioration and soil suction loss between drying and wetting events. These trends were supported by images obtained from scanning electron microscopy.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0523-7
Issue No: Vol. 12, No. 5 (2017)

• Particle breakage and deformation of carbonate sands with wide range of
• Authors: Yang Xiao; Hanlong Liu; Qingsheng Chen; Qifeng Ma; Yuzhou Xiang; Yingren Zheng
Pages: 1177 - 1184
Abstract: In this technical note, evolutions of the particle size distribution, particle breakage, volume deformation and input work of carbonate sands with varying relative densities were investigated through performing a series of one-dimensional compression tests. Loading stress levels ranged from 0.1 to 3.2 MPa. It was found that the initial relative density could greatly affect the magnitude of particle size distribution, particle breakage, volume deformation and input work. Particularly, it was observed that the specimen at a lower relative density underwent much more particle breakage than that at a higher relative density. This could be attributed to the change of the coordination number with the initial density. However, a unique linear relationship between the particle breakage and input work per volume could be obtained, which is independent of the initial relative density.
PubDate: 2017-10-01
DOI: 10.1007/s11440-017-0580-y
Issue No: Vol. 12, No. 5 (2017)

• Fracture evolution and energy mechanism of deep-buried carbonaceous slate
• Authors: Ziquan Chen; Chuan He; Di Wu; Guowen Xu; Wenbo Yang
Abstract: In order to study the influence of confining pressure and water content on the mechanical properties, fracture evolution and energy damage mechanism of deep-buried carbonaceous slate, uniaxial and triaxial compression tests were carried out under natural and saturated states and acoustic emission monitored. The deep-buried carbonaceous slate samples were obtained at a depth of 1020 m from the Lanjiayan tunnel in Sichuan province, China, where the maximum in situ stress has been measured at 44.2 MPa. The results suggest that water has a significant softening effect on the strength and deformation characteristics of carbonaceous slate, but the effect decreases with an increase in the confining pressure. When both the confining pressure and water content are increased, the acoustic emission events and dissipated energy gradually increase at the pre-peak and post-peak stages. Thus, the AE evolution type seen in the natural state under low confining pressure usually presents as a main shock-type event, and it changes to a foreshock–main shock–after shock event when saturated and at high confining pressures. Based on the S-shaped energy evolution law, the damage evolution process of carbonaceous slate was analyzed. The damage stress thresholds σ ea and σ eb were obtained, which can be considered as the thresholds of the rock entering the energy-hardening and energy-softening stages. Finally, a new brittleness energy index BDE is proposed to describe the influence of confining pressure and water content on the damage mechanism of deep-buried carbonaceous slate.
PubDate: 2017-11-10
DOI: 10.1007/s11440-017-0606-5

• Capillary collapse of loose pyroclastic unsaturated sands characterized at
grain scale
• Authors: Mariagiovanna Moscariello; Sabatino Cuomo; Simon Salager
Abstract: The reduction in volume for unsaturated soils wetted at constant total stress is indicated as capillary collapse. Several studies conducted on standard laboratory specimens (macro-scale) outlined the role of initial void ratio, confining pressure and matric suction on collapse onset. Conversely, few observations were made at grain scale, although an important influence of soil structure has been supposed since years. This paper investigated the collapse of coarse and fine sands derived from a pyroclastic soil of Southern Italy. The X-ray computed tomography was used to identify the mechanisms acting at grain scale and to measure the local variations of soil structure. The experimental procedure consisted in preparing remoulded unsaturated specimens and reducing the matric suction until the collapse occurred under self-weight. At different stages of the process, the sample was imaged by X-ray tomography. The experimental results provided original insight into: (1) transformation of soil structure during the wetting tests; (2) variation of porosity, water content and degree of saturation for the whole specimen; and (3) local variations of those variables in several representative sub-volumes. It is worth noting that collapse of coarse sand specimen occurred before saturation. This was also emphasized by the presence of macro-voids at collapse.
PubDate: 2017-10-31
DOI: 10.1007/s11440-017-0603-8

• Correction to: A basic hypoplastic constitutive model for sand
• Authors: Wei Wu; Jia Lin; Xuetao Wang
Abstract: In the original publication of the article, the placement of the symbol sigma in the last term of Eq. (6) is incorrect. The correct equation should read as given below.
PubDate: 2017-10-30
DOI: 10.1007/s11440-017-0605-6

• Effect of particle size distribution on the bio-cementation of coarse
aggregates
• Authors: Aamir Mahawish; Abdelmalek Bouazza; Will P. Gates
Abstract: The effect of grain size distribution on the unconfined compressive strength (UCS) of bio-cemented granular columns is examined. Fine and coarse aggregates were mixed in various percentages to obtain five different grain size distributions. A four-phase percolation strategy was adopted where a bacterial suspension and a cementation solution (urea and calcium chloride) were percolated sequentially. The results show that a gap-graded particle size distribution can improve the UCS of bio-cemented coarser granular materials. A maximum UCS of approximately 575 kPa was achieved with a particle size distribution containing 75% coarse aggregate and 25% fine aggregate. Furthermore, the minimum UCS obtained has applications where mitigation of excessive bulging of stone/sand columns, and possible slumping that might occur during their installation, is needed. The finding also implies that the amount of biochemical treatments can be reduced by adding fine aggregate to coarse aggregate resulting in effective bio-cementation within the pore matrix of the coarse aggregate column as it could substantially reduce the cost associated with bio-cementation process. Scanning electron microscopy results confirm that adding fine aggregate to coarse aggregate provides more bridging contacts (connected by calcium carbonate precipitation) between coarse aggregate particles, and hence, the maximum UCS achieved was not necessarily associated with the maximum calcium carbonate precipitation.
PubDate: 2017-10-28
DOI: 10.1007/s11440-017-0604-7

• Deformation and stresses upon drainage of an idealized granular material
• Authors: Chao Yuan; Bruno Chareyre; Félix Darve
Abstract: A pore-scale numerical model is employed to simulate the primary drainage of a deformable assembly of spherical grains. The model combines the discrete element method and a pore-scale method, respectively, for the solid phase and the fluid phases. The evolution of strain along the simulated drainage in oedometer conditions is reported. The combined actions of phase pressures and surface tension lead the solid skeleton to first shrink and then to swell at the approach of residual saturation. The effective stress is examined through the Bishop’s coefficient $$\chi$$ , obtained by a back analysis of the simulated strain. It is found that $$\chi$$ is relatively close to the degree of saturation, with an exception at very low saturation. Further, a contact stress obtained by averaging micromechanical quantities is found nearly exactly equal to the effective stress deduced directly from the strain, in contrast to previous findings. A detailed analysis of the heterogeneous fields of effective stress, saturation and pressure is offered, suggesting a unique relationship between $$\chi$$ and saturation at a mesoscale.
PubDate: 2017-10-23
DOI: 10.1007/s11440-017-0601-x

• Numerical investigation of rainfall-induced fines migration and its
influences on slope stability
• Authors: Xiaoqin Lei; Zongji Yang; Siming He; Enlong Liu; Henry Wong; Xinpo Li
Abstract: Rainfall-infiltration-induced fines migration within soil slopes may alter the local porosity and hydraulic properties of soils, and is known to be a possible cause of the failure of slopes. To investigate the intrinsic mechanisms, a mathematical formulation capable of capturing the main features of the coupled unsaturated seepage and fines migration process has been presented. Within the formulation, an unsaturated erodible soil is treated as a three-phase multi-species porous medium based on mixture theory; mass conservation equations with mass exchange terms together with the rate equations controlling fines erosion and deposition processes are formulated as the governing equations and are solved by the FEM method. The influences of both the fines detachment and deposition on the stability of slopes under rainfall infiltration have been investigated numerically. The results show that depending on whether the fines move out or get captured at pore constrictions, both desired and undesired consequences may arise out of the fines migration phenomenon. It is suggested that more attention should be paid to those slopes susceptible to internal erosion whose safety analysis cannot be predicted by traditional methods.
PubDate: 2017-10-17
DOI: 10.1007/s11440-017-0600-y

• A compression model for sand–silt mixtures based on the concept of
active and inactive voids
• Authors: Ching S. Chang; Mehrashk Meidani; Yibing Deng
Abstract: A compression model for sand–silt mixtures is needed in geotechnical engineering, for example in the analysis and prediction of deformation of levees and embankments due to internal erosion. In this paper, we introduce a novel concept of dividing the voids of a granular material into two hypothetical fractions: active and inactive voids. The active voids are kinematically available to the compression process. The inactive voids are kinematically unavailable to the compression process. The volume of active voids is dependent on the initial density and effective stress level. The volume of inactive voids is dependent on the amount of fines in the mixture. The current paper considers 1-D and isotropic compression behavior of sand–silt mixtures at stress levels lower than 2 MPa, so no substantial particle breakage is expected to occur. To successfully predict the void ratio for a sand–silt mixture during compression loading, we need (1) a mathematical expression for the evolution of the active void ratio during compression and (2) a relationship between the inactive void ratio and fines content of the mixture. For sand–silt mixtures with any amount of fines, the proposed model requires five material parameters, which are determined from two compression tests, and four minimum void ratio tests on sand–silt mixtures with different fines content. The performance of the proposed model is verified for six different types of sand–silt mixture with various fines contents, by comparing the predicted void ratios with the measured data from the experiments. The comparisons show a good agreement between the predictions and the measured data and prove the suitability of the proposed model for the prediction of compressibility of sand–silt mixtures with any amount of fines.
PubDate: 2017-10-16
DOI: 10.1007/s11440-017-0598-1

• Influence of cementation level on the strength behaviour of bio-cemented
sand
• Abstract: Microbially induced calcite precipitation (MICP) is used increasingly to improve the engineering properties of granular soils that are unsuitable for construction. This shows MICP technique significant advantages such as low energy consumption and environmentally friendly feature. The objective of the present study is to assess the strength behaviour of bio-cemented sand with varying cementation levels, and to provide an insight into the mechanism of MICP treatment. A series of isotropic consolidated undrained compression tests, calcite mass measurement and scanning electron microscopy tests were conducted. The experimental results show that the strength of bio-cemented sand depends heavily on the cementation level (or calcite content). The variations of strength parameters, i.e. effective friction angle φ′ and effective cohesion c′, with the increase in calcite content can be well evaluated by a linear function and an exponential function, respectively. Based on the precipitation mechanism of calcite crystals, bio-clogging and bio-cementation of calcite crystals are correlated to the amount of total calcite crystals and effective calcite crystals, respectively, and contributed to the improvement in the effective friction angle and effective cohesion of bio-cemented sand, separately.
PubDate: 2017-09-08
DOI: 10.1007/s11440-017-0574-9

• Experimental characterization and 3D DEM simulation of bond breakages in
artificially cemented sands with different bond strengths when subjected
to triaxial shearing
• Authors: Z. Li; Y. H. Wang; C. H. Ma; C. M. B. Mok
Abstract: This paper describes the mechanical behavior of artificially cemented sands with strong, intermediate, and weak bond strengths, using experimentation and 3D discrete element method (DEM) simulation. The focus is on the features of bond breakage and the associated influences on the stress–strain responses. Under triaxial shearing, the acoustic emission rate captured in the experiment and the bond breakage rate recorded in the simulations show resemblance to the stress–strain response, especially for strongly and intermediately cemented samples, where a strain softening response is observed. The simulations further reveal the shear band formation coincides with the development of bond breakage locations due to the local weakness caused by the bond breakages. Strain softening and volumetric dilation are observed inside the shear band, while the region outside the shear band undergoes elastic unloading. The weakly cemented sample exhibits a strain hardening response instead; bond breakages and the associated local weaknesses are always randomly formed such that no persistent shear band is observed. Note that in the DEM simulation, the flexible membrane boundary is established by a network of bonded membrane particles; the membrane particle network is further partitioned into finite triangular elements. The associated algorithm can accurately distribute the applied confining pressure onto the membrane particles and determine the sample volume.
PubDate: 2017-08-18
DOI: 10.1007/s11440-017-0593-6

• Lulu Zhang, Jinhui Li, Xu Li, Jie Zhang, Hong Zhu: Rainfall-induced soil
slope failure: stability analysis and probabilistic assessment
• Authors: Wei Wu
PubDate: 2017-08-17
DOI: 10.1007/s11440-017-0591-8

• Reply to “Discussion of ‘Numerical limit analysis of three-dimensional
slope stability problems in catchment areas’ by Camargo et al.
(DOI:10.1007/s11440-016-0459-3)” by Ukritchon et al.
(DOI:10.1007/s11440-017-0589-2)
• Authors: Júlia Camargo; Raquel Quadros Velloso; Euripedes A. Vargas
PubDate: 2017-08-17
DOI: 10.1007/s11440-017-0590-9

• Discussion of “numerical limit analysis of three-dimensional slope
stability problems in catchment areas” by Camargo et al.
(doi:10.1007/s11440-016-0459-3)
• Authors: Boonchai Ukritchon; Suraparb Keawsawasvong
Abstract: A paper recently published by Camargo et al. (Acta Geotech 11(6):1369–1383, 2016) (hereafter identified as “the authors”) presented the numerical limit analysis method (NLA) to compute the safety factor and collapse mechanism of three-dimensional (3D) slopes. For NLA, the authors employed the discrete three-dimensional lower bound formulation with pore water pressure consideration and Drucker–Prager yield criterion, and cast a slope problem as a second-order conic programming problem. The developed program was implemented in MATLAB and validated through three examples of slope problems, and was applied to solve a large-scale 3D slope problem of a failure case study. The discussion of this article focuses on the formulation of the developed 3D NLA and static admissibility of stress field solutions obtained from NLA.
PubDate: 2017-08-16
DOI: 10.1007/s11440-017-0589-2

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