Oct 2026· International Journal of Geomechanics· Vol 26· 0 citations· 29 references
Abstract
Understanding the mechanical behavior of cemented granular materials under multiaxial stress conditions is essential for the safe and efficient design of filtered tailings disposal systems, yet their anisotropic response remains insufficiently characterized. This study examines the strength anisotropy of iron ore tailings and natural sand blends stabilized with ordinary portland cement through low- and high-pressure true triaxial testing. Mixtures were designed using the porosity-to-volumetric cement content index
(
η
/
C
i
v
0.16
)
to achieve equivalent initial conditions across varying dry unit weights and cement contents. The experimental program comprised unconfined compressive strength tests and true triaxial tests covering stress paths (
b
= 0, 0.5, and 1), mean effective stresses (100, 2,000, and 4,000 kPa), and loading orientations (
θ
= 0°–180°). The results show that cementation can suppress compaction-induced anisotropy under stresses below the yield threshold, promoting near-isotropic behavior in all directions; however, anisotropy reappears when cement bonds degrade beyond yielding. While both strength and stiffness improved with increasing cement content and dry density, stiffness was controlled primarily by cement dosage and strength by confining stress. Iron ore tailings displayed a larger normalized yield surface (
q
/
p
′ = 1.2) compared with natural sand (
q
/
p
′ = 0.8 at 2 MPa). These findings validate the
η
/
C
i
v
0.16
index as a practical design parameter, enabling engineers to balance compaction effort and cement content to meet performance targets under complex field stress paths.
In this study, we explore the static and dynamic mechanical responses of layered cemented backfill subjected to blasting loads. Variable-rate uniaxial compression tests and Split Hopkinson Pressure Bar (SHPB) numerical simulations were performed on specimens with three different interlayer cement-to-tailings ratios. All samples were cured for 28 days before testing. The test results reveal that uniaxial compressive strength rises and then falls with increasing loading rates, and mixed tensile-shear failure dominates quasi-static loading conditions. The interlayer cement-to-tailings ratio dominates the bearing capacity of backfill. At the test loading rate of 0.02 mm/s, lowering the interlayer ratio from 1:4 to 1:8 sharply reduces peak strength from 5.595 MPa to 1.285 MPa, with a total drop of 77.0%. SHPB simulation results show obvious strain-rate hardening under dynamic impact. For samples with an interlayer ratio of 1:4, dynamic compressive strength increases from 5.38 MPa to 6.16 MPa as impact velocity rises from 4 m/s to 13 m/s, a 14.5% improvement caused by rapid compaction of internal micropores. Combining damage mechanics and energy conservation principles, we establish a dynamic damage constitutive model that couples inherent layered interfacial damage with blasting-induced dynamic disturbance. Model predictions match experimental measurements well. The peak strength error is only 1.3% at a loading rate of 0.005 mm/s, and peak deviations for all test cases are controlled within 5.0%. This work quantitatively clarifies the static and dynamic mechanical evolution of layered cemented backfill, and provides solid theoretical support for mixture proportion design and blasting stability assessment in high-stage sequential backfilling mining.
This study examines the small-strain shear modulus (
G
max
) and water retention behavior of unsaturated sand–silt mixtures with a focus on the effects of fines content (FC), mean net stress (
p
n
), and hydraulic hysteresis. A comprehensive experimental program was conducted, incorporating saturated and unsaturated bender element tests, soil water retention curve measurements, and scanning electron microscope imaging. The tests were performed on compacted specimens of Firuzkooh No. 161 silica sand mixed with varying silt contents (0-100%) as fines under
p
n
of 50, 100, and 200 kPa along both drying and wetting paths. Two unsaturated triaxial systems equipped with bender elements and a hanging water column controlled matric suction (
ψ
) via axis translation and water head control techniques. The results revealed significant changes in soil structure and hydromechanical behavior with increasing FC. In contrast to other soil mixtures, clean sand exhibited distinct hydraulic and mechanical behaviors, with
G
max
demonstrating a nonmonotonic variation with
ψ
. As FC increased, a pronounced reduction in
G
max
emerged at FC of 20%, at which point the soil structure began to transform from a fines-in-sand to a sand-in-fines structure. Notably, the impact of hydraulic hysteresis became increasingly prominent with FC: for mixtures with 10%–100% FC,
G
max
during wetting was higher than during drying at the same
ψ
levels, whereas an opposite trend was observed for clean sand. Additionally, for sand specimens, the suction stress concept effectively described the variation of
G
max
with
ψ
, while for sand–silt mixtures (10%–100% FC), an extended framework incorporating the equivalent void ratio into a double hardening mechanism concept was adopted. The consistency between experimental observations and theoretical interpretations suggested that these concepts could provide a robust basis for predicting
G
max
behavior in unsaturated sand–silt mixtures.
B. Sadollahzadeh, S. Haeri, Ali Khosravi· Journal of Geotechnical and...· 0 citations
Light pozzolanic soft clay has high compressibility and relatively poor structural stability, which limits its direct application in subgrade and foundation engineering. This study develops a sustainable combined stabilization–reinforcement system for lightweight volcanic ash soil using a steel slag–fly ash-based composite cementitious binder (GS) and recycled polyester fiber (RPF). Unconfined compressive strength tests, unconsolidated undrained triaxial tests, and microstructural characterization were conducted to evaluate the mechanical behavior and microstructural features of the treated soil. The results show that the GS binder markedly increased the soil strength, whereas RPF mainly improved specimen integrity and the post-peak response. Based on the single-additive and orthogonal test results, 24% GS, 0.6% RPF, and 9 mm fibers were identified as an appropriate mixture within the investigated factor levels for further mechanical evaluation. With the increase in confining pressure, the stress–strain response changes from strain softening to strain hardening. Scanning electron microscopy (SEM) observations showed fine particulate material at local particle-contact and fiber–matrix regions, while energy-dispersive X-ray spectroscopy (EDS) analysis identified a representative Ca-rich microregion containing Si and Al. The combined use of GS binder and RPF effectively improved the strength and deformation resistance of lightweight volcanic ash soft clay.
Dan Zhou, Yongchang Yang, Jun Hu et al.· Buildings· 0 citations
Substituting aluminosilicate pozzolans for cement offers a stable and environmentally sustainable mixture. The primary innovation lies in incorporating polypropylene and steel fibers into self-compacting mixtures to enhance mechanical properties and durability, coupled with artificial intelligence modeling (artificial neural networks and decision trees) for compressive strength prediction. This integrated experimental and computational methodology enables more precise optimization of mix designs.The methodology involved producing 16 mix designs with alkaline concentrations of 8 and 12 M, variations in pozzolan quantities, and fiber volumes (0.5 to 1% by volume). Samples underwent ambient and heat curing, with evaluations of fresh properties (slump flow, L-box, V-funnel), mechanical properties (compressive and tensile strength), water absorption, shrinkage, and microstructure (SEM and XRD). Modeling was performed using experimental data to predict compressive strength. Results indicated that increasing molarity from 8 to 12 densifies the concrete microstructure, boosting compressive strength by up to 25% (from 40 to 96.83 MPa at 28 days), although alkaline solution costs may rise. Steel fibers, by forming resilient internal networks, improved tensile and flexural strength by up to 30% and reduced drying shrinkage by 11% . Hybrid fiber combinations enhanced high-temperature durability, retaining 80% strength at 600°C. The AI models achieved accuracies exceeding 88% , positioning this concrete as a sustainable and efficient alternative to Portland cement concrete.
Meysam Rostami, Vahid Rostami, A. Lork· Journal of Resource Manageme...· 0 citations
Abstract This study investigates the replacement of natural sand with manufactured sand in PVA fibre-reinforced strain-hardening cementitious composites (SHCC), with emphasis on the influence of maximum particle size on mechanical behaviour. Five mixtures were produced using natural sand and manufactured sand with maximum particle sizes ranging from 0.30 to 2.36 mm. The mixtures were experimentally evaluated through compressive, uniaxial tensile, and bending tests, together with fracture characterization of the corresponding plain matrices. The results show that replacing natural sand with fine manufactured sand (0.30 mm) does not significantly affect compressive strength, Young’s modulus, or tensile and flexural performance. Increasing particle size had negligible influence on compressive properties but significantly affected post-cracking behaviour. Although first-cracking stress increased, tensile strain capacity, flexural deflection capacity and crack number decreased for the largest particle size investigated (2.36 mm), indicating reduced strain-hardening stability and earlier crack localization. A strong exponential correlation was identified between tensile strain capacity and flexural deflection capacity. Manufactured sand is therefore a viable alternative, provided that particle size is carefully controlled to maintain a balance between strength and ductility.
Vivianne Machado da Costa, Margareth da Silva Magalhães· Ambiente Construído· 0 citations
This study presents an experimental investigation of the mechanical behaviour of an earthen masonry system composed of cement-free stabilised compressed earth blocks (CEBs) and earthen mortar. The test program included compressive strength tests on individual masonry components, shear bond tests under varying pre-compression levels, and compressive strength tests on wall elements with horizontal and inclined bed joints.
The results show that strength of a CEB does not allow for a prediction of the masonry strength. The strength test of a single CEB leads to an overestimation and interactions between units and mortar influence structural response. The initial shear strength value deducted from shear bond tests shows considerable variation depending on the precompression levels considered for evaluation, limiting the suitability for deriving design parameters. In contrast, wall tests with inclined bed joints provide a more consistent representation of the combined normal–shear stress state and allowed reliable assessment of strength and failure mechanisms.
A pronounced reduction in compressive strength was observed with increasing bed joint inclination, followed by a plateau up to the internal friction angle and a subsequent drop to very low strength levels corresponding to sliding failure. This behaviour is comparable to that observed in conventional masonry with fired bricks. The findings indicate that established design approaches, such as SIA 266, may be applicable to earthen masonry, provided material-specific aspects are considered. Further investigations on additional diverse earthen raw materials are required to generalise the results.
