Explore the vast range of titles available.

We study the effect of strain localization on the strength and deformation of aeolian sand in a true triaxial apparatus. Drained and undrained tests are conducted on sand specimens with three initial densities. For the deformation characteristics, the inhomogeneity of volumetric change in drained tests and the excess pore water pressure in undrained tests increases with the confining pressure and relative density, which is closely related to the development of shear bands. The inclination angle and width of shear bands are measured and the influences of confining pressure and relative density are analysed. The shear band inclination agrees better with Arthur's than Coulomb's formula.

Against the backdrop of China’s Western Development Strategy, numerous infrastructure projects are being constructed in desert regions. Utilizing local aeolian sand (AS) as a raw material for concrete production offers significant cost-saving potential but is hindered by challenges such as limited applicability and inadequate mechanical strength of the resulting concrete. To address these limitations, aeolian sand was ground into aeolian sand powder (ASP) and subjected to treatment with single alkali activators (NaOH, Na2SiO3) and a composite alkali activator (NaOH + Na2SiO3). The treated and untreated ASP was then used to replace 50% of cement by mass for the preparation of aeolian sand powder–aeolian sand concrete (ASPC). Mechanical performance tests and advanced characterization techniques (SEM, TG-DSC, XRD, FTIR, nanoindentation, and NMR) were employed to investigate the effects of different activators on the mechanical properties of ASPC and elucidate the underlying enhancement mechanisms. The results demonstrated that the composite activator outperformed its single-activator counterparts: ASPC-4-6 (incorporating 4% NaOH and 6% Na2SiO3) exhibited 16.3–23.1% higher compressive strength and 12.1–17.6% higher splitting tensile strength across all curing ages compared to plain ASPC. Under the influence of OH− from the composite activator, ASP showed more pronounced reductions in potassium feldspar, montmorillonite, and SiO2 content, accompanied by the formation of C-S-H gel—replacing the amorphous, water-absorbent N-A-S-H generated by single activators. The presence of highly polymerized hydration products and more stable potassium A-type zeolites in ASPC-4-6 led to a reduction in macropore volume, optimization of pore structure, and refinement of the aggregate–mortar inter-facial transition zone. These micro-structural improvements collectively contributed to the significant enhancement of mechanical properties. This study provides novel insights into the large-scale and multi-dimensional utilization of aeolian sand in concrete.

Ultra-high-performance concrete (UHPC) has received increasing attention in recent years due to its remarkable ductility, durability, and mechanical properties. However, the manufacture of UHPC can cause serious environmental issues. This work addresses the feasibility of using aeolian sand to produce UHPC, and the mix design, environmental impact, and mechanical characterization of UHPC are investigated. We designed the mix proportions of the UHPC according to the modified Andreasen and Andersen particle packing model. We studied the workability, microstructure, porosity, mechanical performance, and environmental impact of UHPC with three different water/binder ratios. The following findings were noted: (1) the compressive strength, flexural strength, and Young’s modulus of the designed UHPC samples were in the ranges of 163.9–207.0 MPa, 18.0–32.2 MPa, and 49.3–58.9 GPa, respectively; (2) the compressive strength, flexural strength, and Young’s modulus of the UHPC increased with a decrease in water/binder ratio and an increase in the steel fibre content; (3) the compressive strength–Young’s modulus correlation of the UHPC could be described by an exponential formula; (4) the environmental impact of UHPC can be improved by decreasing its water/binder ratio. These findings suggest that it is possible to use aeolian sand to manufacture UHPC, and this study promotes the application of aeolian sand for this purpose.

Aeolian sand widespread in the arid and semi-arid regions has been taken use as the cost-optimal subgrade filling materials. Under the drought climate, the performance of the compacted aeolian sand subgrade is largely dependent on its unsaturated strength. In this work, the shear strength with respect to the matric suction of unsaturated aeolian sand was investigated. A series of triaxial tests were conducted on the compacted specimens with different matric suctions. Results showed that the shear strength of specimen firstly increased with matric suction and then dropped off to a certain value. The maximum shear strength was reached at the matric suction of 40 kPa, which locates in the residual zone on the soil-water characteristic curve (SWCC) of the tested soil. Such phenomena were analysed from the perspective of capillary pore distribution, as well as the internal tri-phase (air-water-solid) structure that identified by microfocus X-ray computed tomography (µCT) technique. According to the capillary pore size distribution of the specimen, pores with radius smaller than 21 μm are theoretically saturated with water at suction of 10 kPa. The identified delimiting pore radius was found to be comparable to that of 25 μm as identified by µCT. On this basis, the role of water bridges in unsaturated aeolian sand and the pore size-level that govern the mechanical properties were discussed.

Aeolian sand is widely distributed in the Takramagan Desert, Xinjiang, China, which cannot be directly used as railway subgrade filling. It is beneficial for environmental protection to use fiber and cement-reinforced aeolian sand as railway subgrade filling. The present work is to explore the enhancement of tensile strength in cemented aeolian sand via the incorporation of polypropylene fibers under conditions of elevated temperature and drying curing. The purpose Is to delve into the examination of the temperature’s impact on not only the mechanical attributes but also the microstructure of cemented aeolian sand reinforced with polypropylene fiber (CSRPF). For this, a comprehensive set of tests encompassing splitting tensile strength (STS) assessments and nuclear magnetic resonance (NMR) examinations is conducted. A total of 252 CSRPF specimens with varying fiber content (0, 6‰, 8‰, and 10‰) are tested at different curing temperatures (30 °C, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C). The outcomes of the NMR examinations indicate that elevating the curing temperature induces the expansion of pores within CSRPF, both in size and volume, consequently contributing to heightened internal structural deterioration. STS tests demonstrate that the STS of CSRPF decreases as the curing temperature increases. Meanwhile, the STS of CSRPF increases with fiber content, with optimal fiber content being 8‰. Regression models accurately predict the STS, with the curing temperature exhibiting the greatest influence, followed by the fiber content according to sensitivity analysis. The research results provide a valuable reference for the use of CSRPF as railway subgrade filling under high temperature and drying conditions.

Experimental studies on reinforcing aeolian sand with cement and fiber are lacking, and the interface mechanism and splitting characteristics thus remain unclear. Herein, the interface mechanism and splitting characteristics of fiber-reinforced, cement-solidified, aeolian sand were experimentally assessed to investigate whether glass fiber exhibits better properties as a reinforcing agent than traditional fiber-free cement-solidified aeolian sand, and whether aeolian sand is applicable as a base material in geotechnical engineering. The splitting experiments involved the use of fiber-reinforced, cement-solidified aeolian sand samples that were differentiated based on the mixing schemes used to formulate them. Based on the strengthening control technology effects on the structural performance of the fiber-reinforced, cement aeolian, sand-mixed matrix material, the internal physical and chemical mechanisms of structural performance evolution were revealed and analyzed using scanning electron microscopy images. The experimental results show that the splitting strength of the sample reaches its maximum value at a combination of 6 mm glass fiber, 3‰ fiber, and 10% cement contents. In fiber-reinforced cement-solidified aeolian sand, cement hydrate forms more needle-shaped crystal products. The crystals adhere to the fiber surfaces that interweave with each other to form a porous and dense network. Although this improves the bonding force between the fiber and aeolian sand particles, the fibers are prone to fracture and slippage during the splitting process. The three-dimensional network structure formed by overlapping fibers is critical for the improvement of the splitting strength. The study’s findings will serve as benchmarks to achieve additional improvements in glass fiber-reinforced cement-solidified aeolian sand.

In order to satisfy the energy demand of China, it is an effective way to exploit coal resources efficiently in western China. When a coal seam with a shallow burial depth is mined on a large working face with width of 300 m in a semi-desert aeolian sand area of western China, the induced subsidence and damage of ground surface are remarkably different from those induced by a traditional mining condition. By taking Working Face 12,406 of Bulianta Coalmine in Shendong Mining Area as an example, this paper, based on actual measurement data, analysed the developmental features and causes of ground surface racks. Research results showed that the shape of the static crack in the peripheral area on the working face was very similar to that contained in the actual measurement results of other areas; specifically, such static crack was arc-shaped and the actually measured static crack angle was 84.5°. However, the dynamic crack above the working face took on uniqueness in two developmental cycles (expansion to restoration). This phenomenon is not available in other research areas. Starting from the structure of rock strata, this paper analysed the two developmental cycles of dynamic cracks according to the periodic fracture theory of key stratum and verified the results of theoretical analysis by employing the similar material model.

To clarify the stress–strain behaviour, strength on the deviatoric plane, shear band formation, and dilatancy characteristics of aeolian sand under three-dimensional loading conditions, a series of true-triaxial tests with various intermediate principal stress coefficients b  ∈ [0.0, 1.0] at constant effective mean principal stress p ' were conducted under drained and undrained conditions. The results presented that the variations of the stress–strain, strength, and effective internal friction angle show its significant dependence on the relative magnitude of the intermediate principal stress expressed in terms of the b value. Because a clear penetrating shear band was produced in the prismatic specimen at b  = 0.2 and b  = 0.4, the stress–strain response exhibits softening, and its peak shear stress and effective internal friction angle are reduced. Besides, shear bands often appear in the hardening regime. Moreover, the dilatancy was the weakest at b  = 0.0 and the strongest at b  = 0.4, which depended on the stress path in terms of the b value. The peak shear stress on the deviatoric plane decreased in a transverse “S” shape with the b value varying from 0.0 to 1.0, correspondingly, the effective internal friction angle increased first and then decreased. But in the case of increasing p ' value, aeolian sand has a unified critical state line and phase transformation line at constant b value.

Aeolian sand (AS) is locally available in desert area that can be used as road construction material. However, AS is a loose granular material with low bearing capacity which needs to be stabilized. This paper presents a novel study of using geopolymer (GP) and fines to stabilize AS. A series of cyclic triaxial tests was conducted to study the effect of GP and fines contents on cyclic response of stabilized AS. The experimental results show that adding fines into AS can effectively increase the cyclic loading capacity but increase the accumulated axial strain of the mixture; inclusion of GP into the AS-fines mixture greatly enhances the cyclic loading capacity and reduces the accumulated axial strain of the mixture. The shakedown response of the untreated AS changes from plastic shakedown to incremental collapse with increase in cyclic stress ratio (CSR); however, the GP-fines-AS mixture with higher fines and GP contents mainly experiences plastic shakedown. The modulus index of untreated AS or fines-containing AS shows an increase-stable trend with loading cycles, indicating strengthening in the soil matrix, but that of the GP-fines-AS mixture shows increase-stable, stable or decrease-stable trend with loading cycles, depending on the CSR and fines and GP contents. Microcharacterization using scanning electron microscope (SEM) shows that the added fines greatly alter the microstructure of AS by filling the voids and acting as lubricant, which facilitates the movement of AS particles and thus induces larger axial strain. The added GP increases the cyclic loading capacity of the treated soil by inducing a chemical fabric in the treated soils. Increase in fines and GP content results in larger contact area and stronger fabric leading to enhanced stabilizing effect.

Being regarded as an elementary contact unit in the foundation and embankment of levees, trenches and other engineering constructions, the soil–structure interface is highly susceptible to erosion by unpredictable seeping water. This phenomenon can be increasingly complex when cohesionless aeolian sand, widely distributed in arid and semiarid regions with a narrow gradation and a poor compression behavior, is involved at the interface erosion. In an effort to enhance the understanding of such erosion seldomly in the spotlight, an interfacial seepage apparatus is developed and employed in this paper to investigate the influence of three impact factors, namely layer order, interface roughness characteristics and near-interface concentration path. It is found that a specified layer order (aeolian sand on top) evinces an apparent irrelevance of interface characteristics and the high critical hydraulic gradient (HCHG) is the lowest. Test analysis based on post-erosion surface status reveals an ambiguous effect of interface roughness characteristics, depending on the form of roughness patterns. Near-interface concentration path holds a potential to alter the erosion progression from interface erosion to vertical internal erosion within sands, suggesting in the meantime that the erosion scale is significantly magnified despite limited variance of HCHG between comparative cases.