To study the failure mechanism of high ductile coagulation (HDC) under sulfate attack in cold saline soil area, cement-based cementing material (cement: fly ash: sand: water reducing agent: water = 1:1:0.72:0.03:0.58) and 2 % polyvinyl alcohol fiber (PVA) were used to prepare HDC sample, to increase the density and ductility of concrete. a 540-day sulfate-long-term immersion test was performed on HDC specimens under two low-temperature curing environments and different sulfate solution concentrations (5 %, 10 %). Using a combination of macro and microscopic methods, according to the principle of energy dissipation, To study the relationship between the evolution of energy (total damage energy U, dissipated energy Uds, elastic strain energy Ues) and the deterioration of strength and the change of pore structure during the compression process of HDC. According to the characteristics of stress-strain curves during HDC compression, the damage evolution characteristics of characteristic stress points during HDC compression are summarized, establish energy storage indicators Kel to evaluate the degree of internal damage of HDC. The results show that during the compression damage process of HDC after long-term soaking in sulfate solution under low temperature environment, Uds and Ues of HDC at characteristic stress points both increase first and then decrease, Kel are reduced first and then increased. The development trend of elastic strain energy and dissipative energy of HDC in 10 % sulfate solution is more drastic than that in 5 % sulfate solution. Compared with the other three groups, the D group energy storage level rises and falls more violently, and the HDC has a smaller ability to resist damage under this condition. Through the study of the correlation between macro and micro changes of HDC in cold saline soil areas and energy evolution, to provide a reference for the stable operation of highly ductile concrete in cold saline soil areas.

The deterioration of rock mass in the Three Gorges reservoir area results from the coupled damage effects of macro-micro cracks and dry-wet cycles, and the coupled damage progression can be characterized by energy release rate. In this study, a series of dry-wet cycle uniaxial compression tests was conducted on fractured sandstone, and a method was developed for calculating macro-micro damage (DR) and energy release rates (YR) of fractured sandstone subjected to dry-wet cycles by considering energy release rate, dry-wet damage and macro-micro damage. Therewith, the damage mechanisms and complex microcrack propagation patterns of rocks were investigated. Research indicates that sandstone degradation after a limited cycle count primarily exhibits exsolution of internal fillers, progressing to grain skeleton alteration and erosion with increased cycles. Compared with conventional methods, the DR and YR methodologies exhibit heightened sensitivity to microcrack closure during compaction and abrupt energy release at the point of failure. Based on DR and YR, the failure process of fractured sandstone can be classified into six stages: stress adjustment (I), microcracks equal closure (II), nonlinear slow closure (III), low-speed extension (IV), rapid extension (V), and macroscopic main fracture emergence (VI). The abrupt change in damage energy release rate during stage V may serve as a reliable precursor for inducing failure. The stage-based classification may enhance traditional methods by tracking damage progression and accurately identifying rock failure precursors. The findings are expected to provide a scientific basis for understanding damage mechanisms and enabling early warning of reservoir-bank slope failure. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

To obtain the precise calculation method for the peak energy density and energy evolution properties of rocks subjected to uniaxial compression (UC) before the post-peak stage, particularly at sigma >= 0.9 sigma(c) (sigma denotes stress and sigma(c) is the peak strength), extensive UC and uniaxial graded cyclical loading-unloading (GCLU) tests were performed on four rock types. In the GCLU tests, four unloading stress levels were designated when sigma = 0.9 sigma(c). The variations in the elastic energy density (u(e)), dissipative energy density (u(d)), and energy storage efficiency (C) for the four rock types under GCLU tests were analyzed. Based on the variation of u(e) when sigma >= 0.9 sigma(c), a method for calculating the peak energy density was proposed. The energy evolution in rock under UC condition before the post-peak stage was examined. The relationship between C-0.9 (C at sigma >= 0.9 sigma(c)) and mechanical behavior of rocks was explored, and the damage evolution of rock was analyzed in view of energy. Compared with that of the three existing methods, the accuracy of the calculation method of peak energy density proposed in this study is higher. These findings could provide a theoretical foundation for more accurately revealing the failure behavior of rock from an energy perspective. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

This study investigates the evolution of the dynamic characteristics of a solidified dredge sludge, including the resilient modulus (MR), accumulative plastic strain (epsilon p) and damping ratio (lambda) during long-term traffic loadings considering influences of environmental actions (dry-wet, DW, and freeze-thaw, FT cycles), stress states (confining stress sigma cand deviator stress sigma d) and loading frequency (f). The experimental results indicate that the dynamic characteristics continuously change with increasing loading cycles and the influences of environmental actions, external stress state, and loading frequency are coupled. The resistance of the solidified sludge against traffic loading decreases after both DW and FT cycles, which is manifested by the decrease in the MR and the increase in the lambda and epsilon p. DW cycles induce greater reductions in the dynamic characteristics than the FT cycles. The increasing sigma c improves the resistance of the soil against cyclic loadings, resulting in higher MR and lower epsilon p and lambda. Besides, their rates of change with loading cycles (i.e., delta MR, delta epsilon p and delta lambda) reduce. The MR, epsilon p, lambda, and delta ap increase while the delta MR and delta lambda decrease with the sigma d, indicating that the increase in the cyclic loading level contributes to the accumulation of plastic strain and energy assumption while the resultant densification effect leads to the increase in the MR and decrease in the delta MR and delta lambda. The soil dissipates less energy when loaded under higher f, resulting in higher MR and lower epsilon p and lambda. Results reported in this paper are helpful for better understanding the dynamic responses of solidified sludge under complex loading and environmental conditions.

Research investigating the complex mechanical properties and energy evolution mechanisms of frozen calcareous clay under the influence of multiple factors is crucial for optimizing the artificial ground freezing method in shaft sinking, thereby enhancing construction quality and safety. In this study, a four-factor, four-level orthogonal test was devised, taking into account temperature, confining pressure, dry density, and water content. The complex nonlinear curvilinear relationship between deviatoric stress, volume strain, and axial strain of frozen calcareous clay under different interaction levels was analyzed. The sensitivity of each factor to the peak volume strain was explored, and the energy evolution mechanism of frozen calcareous clay during the triaxial compression process was analyzed. The findings are summarized as follows: (1) The deviatoric stress-axial strain curves demonstrate the strain-hardening characteristics of frozen calcareous clay specimens. Furthermore, as temperature decreases, the hardening degree increases. (2) Sensitivity analysis indicates that the factors' influence on peak volumetric strain ranks as follows: dry density > confining pressure > temperature > water content. Under the various interactions, specimens exhibit significant volumetric shrinkage. When the temperature remains constant, peak volumetric strain is negatively correlated with dry density but positively correlated with confining pressure. (3) Input energy density, elastic strain energy density, and dissipated energy density of frozen calcareous clay all increase with axial strain. (4) When temperature is held constant, both peak input energy density and peak dissipated energy density rise with increasing confining pressure. Meanwhile, peak elastic strain energy density shows a linear increase with higher confining pressure and lower temperatures.

The shear strength and resistance of granular materials are critical indicators in geotechnical engineering and infrastructure construction. Both sliding and rotation influence the energy evolution of soil granular motion during shear. To examine the effects of particle rotation on shear damage and energy evolution in granular systems, we first describe the transformation of irregularly shaped particles into regular shapes via geometrical parameters, ensuring the invariance of energy density and density. We then analyze the impact of particle rotation on shear-stress variation and energy dissipation through a shear energy evolution equation. Additionally, we establish the relationship between the shear-stress ratio and normal stress, considering particle rotation. Finally, we verify the influence of particle rotation on energy evolution and shear damage through shear tests on irregular calcareous sand and regular silica-bead particles. The results indicate that granular materials do not fully comply with the Coulomb strength criterion. In the initial shear stage, most of the external work is converted into granular rotational-shear energy, whereas in the later stage, it primarily shifts to granular sliding-shear energy. Notably, the sensitivity of the granular rotational energy to a vertical load is significantly greater than that of the granular sliding energy.

The utilization of lunar in-situ resources is an important way to realize the construction and operation of Moon scientific research base. The effect of alumina-alkali activator on the mechanical properties of solidified lunar soil simulant was studied by using basaltic lunar soil simulant as raw material, adding alumina and alkali activator for solidification treatment. Characterisation of hydration products in the simulated lunar soil using X-ray diffraction (XRD), scanning electron microscopy with energy spectroscopy (SEM-EDS), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG) and X-ray photoelectron spectroscopy (XPS). The solidified mechanism of lunar soil simulant under the synergistic effect of aluminaalkali activator was discussed. The results showed that the compressive strength and splitting tensile strength of the solidified lunar soil simulant show an increasing trend, and the highest compressive strength was 17.29 MPa, which was 57% greater than that of the control group. The energy evolution process inside the specimen can be divided into four stages: damage initiation, damage increase, damage mutation and damage acceleration. The incorporation of alumina can promote the geopolymerization reaction between the alkali activator and the lunar soil's mineral composition to generate plenty of (N,C)-A-S-H gels that can fill the pores in the particles, thereby improving the mechanical strength of the solidified lunar soil simulant. Finally, the microscopic reaction mechanism model of alumina-alkali activator synergistic solidified lunar soil simulant was established.

To study the sulfate resistance of ultra-high performance concrete (UHPC) in saline soil area of western China, four kinds of sulfate solution concentrations (0 %, 5 %, 10 %, 15 %) and 18 drywet cycle tests for 540 days were carried out on UHPC specimens. The effects of sulfate dry-wet cycles on the evolution of UHPC strength and energy were studied, the characteristic stress points during uniaxial compression of UHPC under sulfate dry-wet cycle were determined, based on the evolution law of each energy (total energy U , dissipated energy U d , elastic stress U e ) at the characteristic stress points, the energy storage index was established to measure the damage degree of UHPC. The results show that the energy evolution process and damage mechanism of UHPC samples under sulfate-wet and dry cycle erosion are closely related to macro and micro changes. With the development of sulfate dry-wet cycle, the dissipative energy U d and elastic strain energy U e of UHPC at the characteristic stress points increased first and then decreased. The development trend of elastic strain energy U e and dissipative energy U d is more severe with the increase of sulfate solution concentration. The ratio of elastic strain energy at damage stress to elastic strain energy at peak stress ( U e ib /U i e ) is taken as the energy storage index K ib to measure the damage degree of UHPC, under 10%Na 2 SO 4 erosion, K ib can be increased by 21.41 % at the highest and decreased by 29.67 % at the lowest compared with the initial value. It shows that the damage process of UHPC is difficult and then easy, and this index can accurately reflect the external force required for the damage of UHPC under sulfate dry-wet cyclic erosion, and provide a reference for the safe and stable operation of UHPC in saline soil area.

In this study, the axial swelling strain of red-bed mudstone under different vertical stresses are measured by swell-under-load method, and the microstructure of mudstone after hygroscopic swelling is studied by mercury intrusion porosimetry (MIP). The weakening coefficient and Weibull distribution function are introduced into the coupling model of mudstone moisture diffusion-swelling deformation-fracture based on finite-discrete element method (FDEM). The weakening effect of moisture on mudstone's mechanical parameters, as well as the heterogeneity of swelling deformation and stress distribution, is considered. The microcrack behavior and energy evolution of mudstone during hygroscopic swelling deformation under different vertical stresses are studied. The results show that the axial swelling strain of mudstone decreases with increase of the vertical stress. At low vertical stresses, moisture absorption in mudstone leads to formation of cracks caused by hydration-induced expansion. Under high vertical stresses, a muddy sealing zone forms on the mudstone surface, preventing further water infiltration. The simulation results of mudstone swelling deformation also demonstrate that it involves both swelling of the mudstone matrix and swelling caused by crack expansion. Notably, crack expansion plays a dominant role in mudstone swelling. With increasing vertical stress, the cracks in mudstone change from tensile cracks to shear cracks, resulting in a significant reduction in the total number of cracks. While the evolution of mudstone kinetic energy shows similarities under different vertical stresses, the evolution of strain energy varies significantly due to the presence of different types of cracks in the mudstone. The findings provide a theoretical basis for understanding the hygroscopic swelling deformation mechanism of red-bed mudstone at various depths. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).