Combined use of geopolymer and recycled aggregate (RA) significantly reduces carbon emissions over the entire life cycle of concrete. In this study, the effects of modified materials (nano-SiO2 and steel fibers) and RA on workability, compressive strength, and fracture performance of geopolymer recycled concrete (GRC) were evaluated. The fracture behavior of GRC was analyzed based on DIC technology. Results showed that RA with associated compensating water improved workability but reduced compressive strength and fracture properties of GRC. The incorporation of modified materials shifted the fracture mode of GRC toward plastic behavior, and significantly enhanced the initial/unstable toughness, and fracture energy. Strain field analysis results revealed that GRC exhibited a tensile fracture pattern, and modified materials constrained crack propagation, reduced the fracture process zone length, and narrowed the maximum crack width. Based on DIC results, a damage evolution equation and fracture damage model for GRC were developed by introducing a damage evolution factor. Microstructural analysis revealed that RA increased pore size parameters by introducing internal defects, and formed secondary phases such as calcite. In contrast, the modified materials had a positive influence on the matrix morphology and pore structure, promoting the formation of additional geopolymerization products. This study provides essential theoretical support and a technical framework for developing low-carbon, high-performance recycled concrete.

Understanding the dynamic behavior of fractured rock masses is crucial for ensuring safety and stability in mining, tunneling, and underground construction, particularly where structures are subjected to seismic events or blast-induced vibrations. While previous studies have examined either rate effects or fracture-related influences separately, the coupled impact of loading rate and fracture network characteristics remains poorly understood, especially given the stochastic nature of geological discontinuities. This study introduces a novel hybrid framework that combines the bonded particle model (BPM), the discrete fracture network (DFN) and physics-inspired machine learning (PIML) to investigate these complex interactions. The framework uniquely integrates stochastic fracture generation, dynamic numerical simulation, and machine learning to capture both deterministic and probabilistic aspects of rock mass behavior. Results reveal distinct competing mechanisms between rate-strengthening and fracture-weakening effects. Dynamic strength exhibits a positive correlation with loading rate while weakening as fracture intensity increases, with a critical fracture intensity range (5-10 m/m2) where strength variability peaks. A significant finding is the transition in failure modes from predominantly shear failure along pre-existing fractures to mixed tensile-shear failure as fracture intensity and loading rate increase. The developed PIML-based model achieves 97.43% accuracy in predicting dynamic uniaxial compressive strength, while uncertainty quantification demonstrates that loading rate and fracture intensity independently contribute 31.17% and 34.71% to strength variation, respectively. These findings provide quantitative guidance for engineering design, enabling more accurate assessment of rock mass stability under dynamic loading conditions and the optimal design of support system based on fracture characteristics.

In tunnel engineering, construction activities usually traverse natural rock masses containing joints. The positional relationship between joints and holes is a key factor controlling the mechanical properties and damage evolution of surrounding rock. To investigate the effects of the joint-hole positional relationship on strain field evolution, crack propagation, and coalescence behavior, uniaxial compression tests were conducted on rock-like specimens containing a single circular hole and a 45° inclined joint. A multi-field analysis framework integrating acoustic emission (AE), digital image correlation (DIC), the strain quantitative calculation model (SQCM), and COMSOL Multiphysics simulation was established. The results indicate that the peak strength of specimens is governed by the coupling of the boundary constraint effect and the stress superposition effect. When joints and holes are arranged at the central position, the mechanical properties and stress distribution are optimized, whereas proximity to the specimen boundary weakens the boundary constraint and intensifies stress concentration, thereby promoting premature failure. The relative spacing between joints and holes dominates the damage evolution by adjusting the superposition of compressive stress fields: a small spacing aggravates early damage and accelerates strain localization, while an increase in spacing weakens the stress superposition and gradually improves the peak strength. Mechanistically, the top and bottom of circular holes are high-tensile-stress zones, the horizontal sides are high-compressive-stress zones, and significant shear stress concentration occurs at joint tips. These spatially distinct stress characteristics lead to four representative crack coalescence modes, including tensile, compression–shear composite, shear-dominated, and multi-mechanism composite, each corresponding to a unique stress-driven failure path. Among them, the compression–shear composite mode exhibits the highest structural stability and residual load-bearing capacity. Furthermore, the damage variable derived from cumulative AE counts is spatiotemporally synchronized with the evolution of localized strain bands, and the sharp exponential rise in the proportion of high-strain pixels quantified via the SQCM serves as a reliable precursor to macro-instability. In summary, this study provides a comprehensive mechanistic understanding from mesoscopic damage accumulation to macroscopic instability, and lays a solid foundation for the stability assessment of jointed rock masses in tunnel engineering.

The occurrence of fracture failure in deep tunnels is closely related to impact disturbances, and the tunnel cross-section shape and structure plane further affect the process and characteristics of fracture failure. To explore the influence of cross-section shape and impact load on tunnel failure mechanism, based on the improved split Hopkinson pressure bar (SHPB) and Digital Image Correlation (DIC), a series of dynamic impact tests were carried out on rock specimens with structure plane and different cross-section shapes. The results indicate that the crack types and initiation positions in the specimens with different cross-section shapes are quite different due to the structure plane and impact load. With the increase of impact load, the failure mode of the rock changes from obvious shear failure to mixed tension-shear failure. For the specimens with circular and D-shaped cross-section shapes, the strain change mainly tends to transform from the rock bridge to the hole and the end of the specimen, which finally results in the shear fracture failure. While the strain changes of the specimens with elliptical and rectangular cross-section shapes are more complicated, they eventually undergo shear and tensile mixed failure. A damage mechanics model is proposed to characterize the deformation characteristics of rock with different hole and structure plane under impact loads. Our proposed model comprehensively considered the dynamic load and coupled damage induced by different hole and structure plane on the dynamic mechanical response of rock specimens. Based on the energy dissipation and release theory, the stress and strain are divided into four stages. For the combined fractured rock, the ratio of dissipated energy to elastic energy can also be used to characterize the stable state of the rock system, which can be used as an energy index for rock fracture failure. Based on the test results, the dynamic failure energy release rate ∆D-RERR of rock considering the post-peak residual strength is proposed as the basis for judging the impact failure tendency. Combined with the evaluation results of traditional indexes (elastic energy index WET, impact energy index KE, dynamic failure time DT) and the final fracture failure of the sample, the rationality and effectiveness of the ∆D-RERR index are verified. The dynamic failure energy release rate of the rock with rectangular and D-shaped holes is greater than that of the rock with circular and elliptical holes. The findings can provide robust support for tunnel stability analysis and optimized design of support structures.

Repeated excavation and fluctuations in water levels subject mortar to varying stress rates and moisture conditions; however, the coupling effects of these factors remain insufficiently studied. This research examines the combined influence of unloading rate and water content on the mechanical behavior of water-bearing mortar (WM) under multi-level differential cyclic loading (MDCL). Experiments were conducted on specimens with three representative water contents (0.00%, 6.99%, and 13.98%) under multiple unloading rates. The results indicate that both factors affect mechanical properties and interact synergistically. Critical thresholds were identified at a water content of 6.99% and an unloading rate of 2.0 kN/s, marking distinct transitions in energy response. A strong linear relationship was observed between cumulative strain increment and the number of MDCL cycles, which may facilitate failure prediction. Both loading and unloading moduli were highly sensitive to moisture content and unloading rate, with MDCL enhancing the overall stiffness of the material. These findings contribute to a deeper understanding of the coupled effects of water content and unloading rates on mortar under MDCL, offering valuable insights for assessing the stability and deformation of WM structures in engineering applications.

Horizontal spacing between twin parallel tunnels and surrounding rock joint dip angle are critical to tunnel stability. To clarify the underlying mechanisms, uniaxial compression tests were conducted on rock-like specimens with parallel holes (spacing: 0, 20, 40, and 60 mm) and prefabricated joints (dip angle: 0 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees), with acoustic emission (AE) and digital image correlation (DIC) employed to monitor crack propagation and full-field strain evolution. Results show horizontal spacing affects specimen strength by regulating inter-hole stress superposition, with peak stress showing a nonmonotonic trend of first rising then falling and 20 to 40 mm spacing optimizing stress distribution to enhance load-bearing stability; joint dip angle dominates failure modes via crack propagation paths, as a 45 degrees dip induces the strongest compression-shear coupling to maximize bearing capacity and increase mixed-mode cracks while shear cracks prevail at other angles. A boundary line with a slope of 100 enables quantitative distinction between different crack types, thus confirming the dynamic influence of these two parameters (horizontal spacing and joint dip angle) on crack modes. Additionally, numerical simulations conducted via COMSOL Multiphysics confirmed the existence of a "low-stress bridge" effect between the two parallel holes and elucidated the compression-shear coupling mechanism along the joint surface.

Conventional one-part engineered geopolymer composite (EGC) facilitates the mixing process of EGC. However, this "one-part" only refers to the matrix of EGC, the reinforcing fiber as the second step should be separately added during mixing. In this study, through a careful multi-component design to regulate matrix rheology and fiber dispersion, we pioneer the development of a single-step metakaolin-based EGC, which requires only a single mixing step of adding water to achieve exceptional tensile performance, without dry pre-mixing process. This one-part EGC exhibits a density of approximately 1100 kg/m3 and a compressive strength of up to 40 MPa, outperforming conventional "one-part" geopolymers with similar densities. Remarkably, with only 0.5 % fiber volume fraction, about 1/4 of that in conventional EGC, the proposed single-step EGC achieves a high tensile strain capacity of 6 %. Further, the 28-day dry shrinkage remains below 300 mu epsilon, setting a new benchmark for the lowest dry shrinkage in geopolymers (400-1000 mu epsilon) and even rivaling ordinary concrete with similar strength grades. The current findings can address the production process shortcoming of conventional fiber-reinforced composite compared to ordinary concrete and facilitate the practical application of EGC.

The phenomenon of rock strain concentration serves as a significant precursor to damage initiation. This article conducts uniaxial compression tests on defective red sandstone under real-time monitoring using digital image correlation (DIC). Based on strain concentration identification program (SCIP), the strain concentration damage model (SCDM) is first proposed, and the strain concentration damage contribution factor was introduced into the model to characterize the influence of different strain levels on the degree of rock surface damage. Based on this model, the evolution curve of damage rate in defective specimens was obtained, thereby supplementing traditional damage assessment methods. Meantime, the discrete element software PFC was used to establish a two-dimensional model of defective specimens, enabling analysis of the damage evolution process of the specimen. The results indicate that the damage curve derived from SCDM are consistent with the numerical simulation results, confirming the capability of SCDM for two-dimensional damage evaluation. Importantly, SCDM effectively captures the evolution of the surface damage ratio during the pre-peak loading process. Damage evolution roughly follows non-damage stage, micro-damage stage, and accelerated damage stage. During the accelerated stage, an increase in defect inclination and width leads to a higher growth rate of the damage ratio. These findings provide valuable references for damage quantification and evolutionary analysis in rock engineering applications.

Tunnel water surge of fault fracture zone poses a threat to tunnel engineering safety. To understand the water surge mechanism during excavation, a tunnel similar physical model is constructed by similarity theory. And water surge tests during excavation are conducted to analyze disaster precursors response characteristics. It is studied that the tunnel remained stable in the early excavation time. Small-scale water surge occurs during the 27th excavation, while three large-scale water surge events happen during the 33rd-35th. Under combined disturbance from excavation and groundwater, surrounding rock stress and displacement first stabilizes, then fluctuates significantly-features that can serve as precursor criteria for water surge disasters. Based on Janssen silo theory, the critical anti-outburst thickness S calculation model for tunnel water surge is developed. It reveals that groundwater pressure and rock fragmentation exert the greatest influence on S. The model-calculated S = 6.56m shows an error of only 5.30 % against tunnel field data, verifying the reliability of anti-outburst measure parameter optimization. The water surge evolution in fault tunnels is divided into three stages: stable, accumulation, and water-surge, with the accumulation stage being critical for implementing anti-outburst measures. In this study, anti-outburst thickness S calculation and water surge evolution analysis can provide support for water surge protection in fault fracture zone tunnels.

The enhanced geothermal system (EGS) is the primary technology for extracting hot dry rock (HDR) resources, and numerical modeling is extensively utilized to simulate EGS. However, the complex pore-fracture structure of HDR presents challenges in establishing accurate numerical models. In this study, we present a fractal dual-porosity coupled thermo-hydro-mechanical model that reveals the structural evolution of natural fractures and pores under the influence of multi-physical fields. This model simultaneously accounts for the effects of fracture-pore interactions and energy conduction mechanisms. The primary focuses of the model’s operation are heat performance and surface settlement. Additionally, we analyze and compare the impacts of fractal parameters, working fluid, and geothermal reservoirs. The results indicate that the change in fractal parameters primarily affect the net energy production of the geothermal reservoir. Furthermore, low-temperature water with a faster flow rate represents the ideal working condition. The reservoir with a higher initial temperature, the more heat can be extracted and variations in initial porosity of the fracture system and the matrix system have no significant effect on thermal performance and deformation.

The microstructure and mechanical properties of a new 2 200 MPa grade ultra-high strength steel after different austenitizing temperature treatments were investigated through mechanical tests， optical microscopy （OM）， scanning electron microscopy （SEM）， and other methods.The results showed that the strength and toughness and plasticity first increased and then decreased with the increase of austenitizing temperature. At 940°C austenitizing temperature， the optimal strength-toughness balance was achieved， with a tensile strength of 2 222.5 MPa， a yield strength of 1 725.5 MPa， an elongation after fracture of 11%， a reduction of area of 42.5%， and an impact energy of 51.05 J.At lower austenitizing temperatures， the impact fracture morphology was primarily characterized by hole-aggregating toughness dimples with fine grain size.Fine secondary phases （with a diameter of only 0.75 µm） were observed on the fracture surface. Based on phase diagram calculations and EDS（energy spectrum analysis）， the secondary phase was identified as M23C6.With increasing austenitizing temperature ， the morphology of the impact fracture surface transitioned to a combination of dimples and quasi-cleavage， accompanied by the disappearance of secondary phases and gradual coarsening of grains.

As a widely used building material, normal concrete (NC) often undergoes performance degradation, making ultra-high performance concrete (UHPC) a promising option for reinforcement and repair. The interfacial transition zone (ITZ) critically governs the behavior of UHPC-NC composite structures, especially under dynamic loads. This study examines the static and dynamic tensile and shear properties of the UHPC-NC interface using four specimen types tested with a universal testing machine and a Hopkinson bar, supplemented by DIC monitoring. The results show that under dynamic loads, the tensile and shear strengths of UHPC-NC specimens exhibit a significant strain rate enhancement effect. The strength increases exponentially with the strain rate, and the Dynamic increase factor (DIF) shows a high linear correlation with the logarithm of the strain rate, following the log-linear strengthening law. Interface roughness positively regulates the mechanical properties. Rough interfaces have higher dynamic tensile and shear strengths than smooth interfaces, but the effect weakens with increasing loading rate. Steel fibers effectively enhance the mechanical properties and change the failure mode. The strength growth of specimens with steel fibers shows a two-stage process of "matrix-dominated to fibersaturated". The dynamic tensile and shear strengths increase linearly with the loading rate, but the enhancement effect saturates when the loading rate reaches a certain value (e.g., 6 m/s). The failure modes of specimens differ under different loading conditions. Dynamic loading leads to severe compression damage and non-linear crack propagation, while static loading results in linear cracks.

Natural rock masses often have dense fracture networks and structural defects, compromising their stability. High-Strength Mortar (HSM) is widely used for grouting reinforcement, but the HSM-rock interface is a potential weak link, especially under dynamic disturbances. This study investigates the fracture behavior of the HSMgranite interface using Bi-material Notched Semi-Circular Bend (BNSCB) specimens. Three-point bending tests under static (0.1 mm/min) and dynamic (2.5 m/s, 3.5 m/s) loading with pre-crack lengths (5, 10, 15 mm) were conducted. Crack propagation velocity was measured via Crack Propagation Gauge (CPG), and interface characteristics were analyzed using SEM-EDS. A cohesive zone model (CZM) was developed in ABAQUS to simulate crack propagation, and complex stress intensity factors (CSIF) were calculated. Results show Interfacial cracks consistently propagated along the HSM-granite boundary, confirming the interface as the weak link due to a porous, calcium-rich Interfacial Transition Zone (ITZ) about 151 mu m wide, identified by EDS. Dynamic loading significantly accelerated crack propagation, with velocities increasing by 417 % to 1579 % compared to static conditions, due to inertial effects and rapid energy accumulation. The fracture was predominantly Mode I, with the effective fracture toughness (Keff) under dynamic loading being 30-40 times greater than under static loading. The Dynamic Increase Factor (DIF) was primarily controlled by the loading rate. Furthermore, a longer pre-crack length (from 5 mm to 15 mm) led to a reduction in Keff by 21 % (dynamic) and 13 % (static), as longer cracks require a lower external load to reach the critical condition. Simulations using a Cohesive Zone Model (CZM) with a bilinear traction-separation law accurately replicated the experimental crack paths and stress distributions, validating the model's capability for simulating high-strain-rate interfacial fracture.

Engineered cementitious composite (ECC), recognized for its exceptional deformability and crack-control capacity, represents a promising material for resilient infrastructure. However, the low melting point (typically below 200 degrees C) of traditional synthetic fibers limits ECC's application in the scenarios prone to fire or elevated temperatures. Enhancing the high-temperature resistance of ECC has long been a persistent challenge. This study pioneered the integration of high-melting-point liquid crystal polymer (LCP) fibers and low-fracture-toughness geopolymer matrix, developing a novel class of low content fiber-reinforced engineered geopolymer composites (LCP-EGC) that pushed the high-temperature-resistance of ECC to a new level. With only 1 vol% fiber content, LCP-EGC retained pronounced strain-hardening characteristics and excellent crack-control ability even after exposure to 300 degrees C, achieving a tensile strain of 4% and a crack width of 60 mu m. The underlying mechanisms governing the high-temperature strain-hardening response of LCP-EGC were revealed through multiscale analysis covering fiber, matrix, and fiber-matrix interface properties. Furthermore, LCP-EGC exhibited excellent thermal insulation ability, with a thermal conductivity as low as 0.2 W/(m & sdot;K). A case analysis revealed that the post-fire concrete material cost loss of LCP-EGC composite slabs can be reduced by approximately 27% compared to polyethylene fiber-reinforced ECC with similar thermal conductivity. These findings can offer both theoretical insight and practical strategies for advancing high-temperature-resistant and resilient structural designs.

The high-temperature plastic deformation behavior of 2 200 MPa grade ultra-high strength steel was investigated using a Gleeble 3 800 thermal simulation test machine. The stress-strain curves of high-temperature tensile deformation at strain rates of 0.1 s-1 and 0.001 s-1 within the temperature range of 750 ℃-1 100 ℃ were obtained. Metallographic observation and EBSD analysis were conducted on the microstructure of the longitudinal section near the fracture surface， and scanning electron microscopy （SEM） was used to observe the fracture morphology. The high-temperature plasticity and dynamic recrystallization behaviors of 2 200 MPa grade ultra-high strength steel were investigated. The research results showed： 1） At both strain rates， the tensile strength of the test steel continuously decreased with increasing deformation temperature； 2） at the strain rate of 0.1 s-1， the reduction of area increased with increasing temperature during tensile deformation at 750 ℃-1 000 ℃， and decreased with increasing temperature when T> 1 000 ℃； at the strain rate of 0.001 s-1， the reduction of area showed two troughs， near 800 ℃ and 925 ℃， respectively； the reduction of area peaked at T=1 050 ℃， after which it decreased with increasing temperature； 3） based on the strength and reduction of area， the forgeability of the test steel can be calculated. At the strain rate of 0.1 s-1， the forging temperature range of the test steel was 880 ℃-1 100 ℃， and at the strain rate of 0.001 s-1， the forging temperature range was 850 ℃-1 100 ℃； 4） when the deformation temperature was ≥1 050 ℃， high-temperature molten dendrites appeared on the tensile fracture， and the initial forging temperature should be below 1 050 ℃； 5） when the strain rate was 0.001 s-1， the onset temperature of dynamic recrystallization was 750 ℃. When the strain rate was 0.1 s-1， the onset temperature of dynamic recrystallization was 880 ℃. When the deformation temperature was ≥ 900 ℃， the grain size at the strain rate of 0.1 s-1 was finer than that at a strain rate of 0.001 s-1， so the rapid forging process should be adopted in the early stage of forging； when the deformation temperature is less than 900 ℃， the dynamic recrystallization fraction is higher at a strain rate of 0.001 s-1. Therefore， a slow forging process should be adopted in the later stages of forging to obtain a uniform and fine forged microstructure. The optimal forging temperature range for 2 200 MPa grade ultra-high strength steel is between 880 ℃ and 1 050 ℃.

Transient dynamics of non-pneumatic tires are particularly critical for evaluating their performance in medium-speed vehicles. To study transient dynamic characteristics of the non-pneumatic tire with honeycomb spokes, a finite element (FE) model was initially established using the ABAQUS software. The validity of the FE model was demonstrated through comparing predicted and measured results. Transient simulations were subsequently performed to investigate the effects of obstacle size, rolling speed, and normal load on longitudinal and vertical dynamic responses of the tire in both time and frequency domains, apart from its local deformation characteristics. The results showed significant growth in peak longitudinal and vertical forces with an increase in obstacle radius and normal load. The resonance frequencies in axle forces, however, were slightly affected by these parameters. Besides, the speed revealed notable effects on both time and frequency domain response characteristics, particularly the variation in resonance frequencies of the longitudinal forces when the velocity was increased from 20 to 50 km/h. In addition, the honeycomb tire exhibited qualitatively inferior enveloping performance than its pneumatic counterpart. These results could help deepen the understanding of the transient dynamic behavior of honeycomb tires under real-world driving conditions and offer essential guidance for optimizing tire designs for practical applications.

Fiber-reinforced concretes (FRCs) possess improved tensile performance compared with normal concrete, yet only very few exhibit the high tensile strain capacity exceeding 6%. Based on the proposed strength and energy criteria, the authors supplement two potential reasons why high tensile strain capacity is hard to achieve in most FRCs at the level of mathematics. (1) Different fibers exhibit two distinct bond-slip failure modes, which demonstrate entirely different sensitivities to statistical dispersion, resulting in significant variations in single-crack bridging capacity. (2) At similar dosages, the fiber diameter directly influences the distribution density of fibers, which in turn affects the statistical dispersion among multi-crack bridging capacities and ultimately impacts the stability of the tensile strain capacity. At the level of physics, two unique characteristics of Ultra-High Molecular Weight Polyethylene (UHMWPE) fibers are assumed to be critical to achieve high tensile strain capacity. First, ultra-long molecular chains and highly oriented molecular structure of UHMWPE fibers unexpectedly produce bamboo-like surface protrusions during the mixing procedure, thereby significantly improving their interfacial property and consequently the fiber bridging strength. Second, pores that occur at fiber ends during whole-fiber pullout weaken the matrix fracture toughness adjacent to a bridged crack, lowering its cracking strength level to generate further a band of cracks as often observed. Logical deduction, stochastic modeling, and a series of macro- and micro-experiments were conducted to verify the above hypotheses. This work helps to further understand the mechanisms of strong tensile strain-hardening and strain capacity in cementitious composites.

To promote the high-value reuse of construction waste, recycled brick-concrete aggregates (RBCA) are employed in reinforced concrete columns to investigate their seismic performance through low-cycle loading tests. The experimental parameters included the replacement ratio of recycled brick aggregate (RBA), axial load, and stirrup ratio. The experimental results indicated that all specimens exhibited flexural failure characteristics and plump hysteresis curves. The influence of RBA on the load-bearing capacity of control specimens was within 0.85%, and the displacement was delayed. Compared with traditional reinforced column, the RBCA specimens exhibited slower stiffness degradation rate and reduced ductility performance. However, the ductility coefficients of all tested specimens exceeded 3. When the RBA replacement ratio did not exceed 50%, RBCA reinforced columns with the consistent compressive concrete strength can exhibit similar seismic performance to traditional columns. With the axial load ratio increased from 0.07 to 0.15, the failure process and stiffness degradation accelerated, and the bearing capacity increased by 20.1%. A higher stirrup ratio enhanced the confinement effect and delayed the failure process of the specimen. The previously proposed stirrup-confined RBCA concrete constitution was employed for characteristic points calculation, yielding satisfactory fitting results. A restoring force model calculation method was developed, and the model can conservatively trace the trajectory of the experimental hysteresis curves. RBCA concrete can be considered for practical engineering applications, and when the RBA replacement ratio did not exceed 50%, it can be applied to low-rise buildings.

High-strength and High modulus Engineered Cementitious Composites (HSHM-ECC) features excellent tensile ductility, high tensile/compressive strength and elastic modulus. Prestressing technology can effectively improve the crack resistance performance, durability and load-bearing capacity of concrete structures. It is expected that the application of HSHM-ECC in the prestressed systems will further enhance the structural durability and ductility. In this research, a HSHM-ECC with elastic modulus exceeding 45 GPa, 28-day drying shrinkage less than 400 mu epsilon, 120-day creep coefficient less than 0.5 and chloride diffusion coefficient of 0.04 & times; 10-12 m2/s was developed. The local compression characteristics of HSHM-ECC were investigated and a novel prestressed HSHM-ECC composite beam system was then proposed. The flexural and shear performance of prestressed HSHM-ECC beams were preliminarily evaluated, which revealed superior structural performances over the prestressed mortar and UHPC beams at serviceability and/or ultimate limit states. The cracking load and bearing capacity of prestressed HSHM-ECC beams under the serviceability limit state have increased by 107.1 % and 23.1 % respectively compared with those of ordinary HSHM-ECC beams. The energy absorption of prestressed HSHM-ECC beams was increased by 284.4 %, 384.1 % and 101.0 % respectively compared with that of prestressed mortar beam, prestressed UHPC beam and ordinary HSHM-ECC beams. This paper demonstrates the feasibility of prestressed HSHM-ECC components based on the tests at both material and structural component levels. The proposed prestressed HSHM-ECC composite components have application potential for bridges, industrial buildings, railway sleepers and marine structures (e.g., exploration platforms and floating structures) with enhanced structural resilience.

Areas of serpentine in ophiolitic melange zones often trigger large rock avalanches and exhibit strong movement. However, how the mechanism under which they post-failure hypermobility and long runout are unclear. Here, we identify and analyze a representative prehistoric rock avalanche, the Basu rock avalanche, with a large volume and a high mobility, which developed in the Nu River ophiolitic melange zone of the Tibetan Plateau. Based on field investigations, experimental, and Numerical simulation analyses we determined its development background and thus explained why it was hypermobile. This rock avalanche, with a volume of approximately 3.15 x 10(9) m(3), occurred around similar to 187 ka before present (B.P.). It developed on a marble nappe, with serpentine soft rock exposed locally at its base. It may have ultimately been triggered under seismic action, resulting in intense movement. The lubrication effect of fine-grained serpentine particles within the slip zone facilitated the hypermobility of the rock avalanche, resulting in both a large volume and an extended runout distance. This demonstrates that serpentine soft fine particles widely distributed in the suture zone are a typical lubricating material. The hypermobility of this large rock avalanche are striking and emphasizes the need to determine where, how and when these rare but high-magnitude rock avalanche events may occur. We proposed a new perspective on the triggering mechanisms of the rock avalanches and further verified the hypothesis of powder lubrication control effects.