Fracture Stage Research Articles

Application of the block factor analysis in the implementation of hydraulic fracturing during oil fields development

The relevance of this study is due to the need to optimize the oil production process in the fields of the West Siberian province. At the moment, the actual oil recovery factor often deviates from the design values, which leads to inefficient production and loss of resources. Therefore, the purpose of the study is to develop a meth-odology for optimizing the process of monitoring and regulating an oil field development facility using block factor analysis and de-signing hydraulic fracturing cracks. The work uses methods such as block factor analysis, 3D modeling, hydrodynamic modeling, and mathematical modeling. The result of the study is a developed methodology for optimizing the process of monitoring and regulat-ing an oil field development facility. The article also discusses the main reasons for the deviation of actual oil production from calcu-lated values, including hydraulic fracturing technology. Unsuccess-ful cases of this procedure and their causes were identified. The features of the block factor analysis tool and the proactive analysis method are described, as well as how to use it at the design and modeling stage of hydraulic fracturing to improve the efficiency of the well-stimulation operation. Successful implementation of hy-draulic fracturing allows one to approximate the actual oil recovery factor to design values, which is important for increasing the effi-ciency of production at the field and optimizing the use of re-sources.

Numerical modeling of fracture propagation of supercritical CO2 compound fracturing

The exploitation of shale gas is promising due to depletion of the conventional energy and intensification of the greenhouse effect. In this paper, we proposed a heat-fluid-solid coupling damage model of supercritical CO2 (SC-CO2) compound fracturing which is expected to be an efficient and environmentally friendly way to develop shale gas. The coupling model is solved by the finite element method, and the results are in good agreement with the analytical solutions and fracturing experiments. Based on this model, the fracture propagation characteristics at the two stages of compound fracturing are studied and the influence of pressurization rate, in situ stress, bedding angle, and other factors are considered. The results show that at the SC-CO2 fracturing stage, a lower pressurization rate is conducive to formation of the branches around main fractures, while a higher pressurization rate inhibits formation of the branches around main fractures and promotes formation of the main fractures. Both bedding and in situ stress play a dominant role in the fracture propagation. When the in situ stress ratio (σx/σy) is 1, the presence of bedding can reduce the initiation pressure and failure pressure. Nevertheless, it will cause the fracture to propagate along the bedding direction, reducing the fracture complexity. In rocks without bedding, hydraulic fracturing has the lengthening and widening effects for SC-CO2 induced fracture. In shale, fractures induced at the hydraulic fracturing stage are more likely to be dominated by in situ stresses and have a shorter reorientation radius. Therefore, fracture branches propagating along the maximum principal stress direction may be generated around the main fractures induced by SC-CO2 at the hydraulic fracturing stage. When the branches converge with the main fractures, fracture zones are easily formed, and thus the fracture complexity and damage area can be significantly increased. The results are instructive for the design and application of SC-CO2 compound fracturing.

Characteristics of Weathering Reservoirs and Differences in Fracture Formation in the Weathering Crust of the Pre-Cenozoic Basement of Lishui Sag, East China Sea Basin, China

Characteristics of Weathering Reservoirs and Differences in Fracture Formation in the Weathering Crust of the Pre-Cenozoic Basement of Lishui Sag, East China Sea Basin, China

Application of micro-substance tracer test in fractured horizontal wells

This paper delves into a novel micro-substance tracer test in fractured horizontal well C-15. The experimental results are highly encouraging as they demonstrate that the trace material tracer is capable of satisfying the testing demands, even when there are large numbers of fracturing stages involved. Data interpretation process involved dividing the test duration into two stages-fluid flowback period and stable production period. The tracer test data were employed to analyze the production profile of the well. The findings made it evident that the primary production stage underwent alterations in different production stages. Moreover, the degree of heterogeneity pertaining to each fracturing stage was characterized by employing the residence time distribution method. It was observed that the Lorentz coefficient lying between the primary production stage and the remaining fracturing stages ranged from 0.46 to 0.68. This study expands the application of the residence time distribution method for evaluating tracer testing. Through a comprehensive analysis of heterogeneity data within the fracturing stages and the production dynamics of the well, the effectiveness of the fracturing process can be assessed. This research enables reservoir operators to gain deeper insights into the dynamics of test wells, ultimately leading to increased production efficiency.

Toughness modification of SBS/CRMA on epoxy asphalt: curing behaviour and low-temperature cracking characteristic analysis

ABSTRACT The limited utilisation of epoxy asphalt primarily stems from its inherent brittle cracking behaviour. This investigation aims to mitigate this issue by introducing styrene–butadiene-styrene/crumb rubber modified asphalt (SBS/CRMA). Furthermore, this research assesses the influence of SBS/CRMA on the curing behaviour of epoxy asphalt (EA) and the low-temperature fracture characteristics of epoxy asphalt concrete (EAC). The curing behaviour of EA was systematically examined using diverse analytical techniques, including attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), rotational viscosity, and non-isothermal curing kinetics analysis. Notably, SBS/CRMA expedites the curing process of epoxy asphalt, possibly attributed to the amine constituents in the crumb rubber, which acts as catalyst. Subsequently, the study scrutinised the fracture characteristics of EAC through the application of the semicircle bending (SCB) test and acoustic emission (AE) methodology. The results substantiate that SBS/CRMEAC imparts a proficient toughening effect, underpinned by an augmented stress relaxation capacity due to the reinforcing influence of elastomers such as crumb rubber and SBS. The fracture process was delineated into three distinct stage and the AE signal in matrix epoxy asphalt (MEA) exhibited concentration during the macroscopic crack extension and final fracture stages. In stark contrast, SBS/CRMEAC exhibited a uniform distribution and showcased ductile fracture characteristics.

Cyclic plasticity behavior and deformation mechanism of 1Cr18Ni10Ti pressure pipe subjected to in-service loadings

Fatigue performance and durability application have always been the key issues impeding the understanding of aero-engine pressure pipe due to its non-standardized shape, making tests more challenging. This paper constructs an optimized testing system to elucidate the plastic shakedown and ratcheting behavior of 1Cr18Ni10Ti pressure pipe subjected to in-service loadings. Moreover, microstructural evolution's role in regulating the cyclic plasticity behavior is qualitatively established. Experimental results indicate that the pipe deformation exhibits compressive ratcheting behavior in plastic shakedown state, and the initial cyclic hardening followed by cyclic saturation occurs during the whole cyclic response. This corresponds to a decreasing ratcheting displacement rate followed by a steady state appears. Except for the first two similar deformation stages mentioned above, the abrupt cyclic softening and the resultant increasing ratcheting displacement rate are obtained at the final fracture stage of the pipe deformation in ratcheting state. A series of detailed microstructural characterizations, including optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), transmission electron microscopy (TEM), and acoustic emission (AE) are combined to reveal the underlying microstructural mechanisms during cyclic deformation. The volume fraction of austenite and ferrite and the average grain size change during different stages of plastic shakedown and ratcheting deformation. The synergistic effects of dislocation structure multiplication, destruction, and dissolution at different stages of plastic shakedown and ratcheting deformation dominate the cyclic plasticity behavior.

Interpretation of low-frequency distributed acoustic sensing data based on geomechanical models

Distributed acoustic sensing (DAS) is a technology that enables continuous, real-time measurements along the entire length of a fiber-optic cable. The low-frequency band of DAS can be used to analyze hydraulic fracture geometry and growth. In this study, the low-frequency strain waterfall plots with their corresponding pumping curves were analyzed to obtain information on fracture azimuth, propagation speed, number of fractures created in each stage, and restimulation of preexisting fractures. We also use a simple geomechanical model to predict fracture growth rates while accounting for changes in treatment parameters. As expected, the hydraulic fractures principally propagate perpendicular to the treated well, that is, parallel to the direction of maximum horizontal stress. During many stages, multiple frac hits are visible, indicating that multiple parallel fractures are created and/or reopened. Secondary fractures deviate toward the heel of the well, likely due to the cumulative stress shadow caused by previous and current stages. The presence of heart-shaped tips reveals that some stress and/or material barrier is overcome by the hydraulic fracture. The lobes of the heart are best explained by the shear stresses at 45° angles from the fracture tip instead of the tensile stresses directly ahead of the tip. Antennas ahead of the fracture hits indicate the reopening of preexisting fractures. Tails in the waterfall plots provide information on the continued opening, closing, and interaction of the hydraulic fractures within the fracture domain and stage domain corridors. The analysis of the low-frequency DAS plots thus provides in-depth insights into the rock deformation and rock-fluid interaction processes occurring close to the observation well.

Optimizing extreme limited entry design for lateral heterogeneous reservoirs

Extreme limited entry (XLE) method can enhance hydraulic fracture uniformity by elevating wellbore pressure to overcome reservoir heterogeneity. However, it increases surface pressure and decreases hydraulic fracturing efficiency. In this paper, the effects of stress shadow and heterogeneity of the lateral breakdown pressure on fracture propagation are numerically studied, from which an optimization method is proposed for the XLE design with the minimal requirement of fracturing pressure. Initially, the unconventional fracture model is applied to analyze fracture propagation in formations with homogeneous geomechanical parameters and various perforation designs. Fracture length distribution is correlated with perforation friction, revealing insights into the influence of geomechanical parameters and fracture spacing. Then, the uniformity of fracture propagation is assessed for different XLE designs by varying lateral breakdown pressures. Simulation results are utilized to develop a cross-plot of fracture length distributions vs normalized perforation frictions for optimizing an XLE design. In homogeneous reservoirs, decreasing perforation spacing and increasing perforation hole erosion rate slow down the reduction in the fracture length distribution span with perforation friction, necessitating a higher perforation friction for uniform fractures. In all simulated cases, a similar trend is observed when the distribution of fracture lengths is plotted vs the normalized perforation friction to the difference of breakdown pressure within one fracturing stage. It is recommended that this normalized value be maintained above 2 in an XLE design. This new plot makes the conventional horn-shaped plot more applicable to reservoirs with heterogeneous lateral breakdown pressures.

Crack Propagation Phenomenon in Gangue Concrete Using the Digital Image Correlation (DIC) Method

In order to study the mode I crack propagation mechanism of coal gangue concrete with different contents, the digital image correlation (DIC) method was used to carry out the three-point bending fracture tests on coal gangue concrete with different contents. The results show that the process of the mode I crack propagation of coal gangue concrete with different contents can be divided into three stages as follows: the elastic stage before crack initiation, extended viscoelastic stage, and extended fracture stage. The amount of coal gangue has a significant impact on the crack propagation path. The more the amount of coal gangue, the more the crack penetrates through the coal gangue coarse aggregate, the smaller the bending degree of the failure path, and the faster the crack propagation to the penetration speed. The crack initiation load, ultimate load, external force work, gravity work, and fracture energy all decrease with the increase of the coal gangue content. The data obtained by the DIC method and displacement extensometer are in good agreement, which proves that the DIC method is feasible. Based on the DIC method, before reaching the horizontal displacement on both sides of the crack tip, the horizontal displacement of the horizontal pixel is very small and there is a jump increase after the ultimate load. There are obvious inflection points on the left and right, and the horizontal displacement remains unchanged after the inflection point. After the horizontal displacement field of crack propagation reaches the limit load, there is an obvious limit; the limit gradually extends upward, and the corresponding crack tip strain field is also gradually enhanced. The more the coal gangue is added, the smaller the corresponding horizontal displacement and strain field is at the same limit load moment. The shape of the crack generation area of coal gangue concrete takes the crack tip as the axis of symmetry and is “gourd shaped.” The more the content of the crack, the larger the crack generation area.

Improving Mining Sustainability and Safety by Monitoring Precursors of Catastrophic Failures in Loaded Granite: An Experimental Study of Acoustic Emission and Electromagnetic Radiation

Effective monitoring and early warning methods are crucial for enhancing safety and sustainability in deep coal resource extraction, particularly in mitigating rock burst disasters triggered by abrupt rock failure under high–ground–stress conditions. This paper presents the results of experimental investigations that involved conventional uniaxial direct and graded mechanical tests on granite that concurrently collected acoustic emission (AE) and electromagnetic radiation (EMR) signals. This study focused on the temporal evolution patterns of characteristic parameters in AE and EMR signals during granite deformation and fracture processes. To deconstruct and understand these temporal evolution characteristics, multifractal and critical slowing–down theories are introduced. The research findings reveal significant correlations between the evolution of AE and EMR characteristic parameters and the stages of rock deformation and fracture. Notably, dynamic changes in multifractal parameters (Δα and Δf) quantitatively reflected the deformation and fracture processes, with abrupt increases in Δα and sudden decreases in Δf closely associated with large–scale rock fractures. The temporal continuity of critical slowing–down parameters (variance and autocorrelation coefficient) demonstrated increased sensitivity as rock destruction approaches, with the variance emerging as a crucial indicator for large–scale fractures. This study observed a sudden increase in the variance of AE and EMR signals when the stress level reached 80–90% of the peak stress. Joint monitoring through diverse methods and multiple indicators enhanced the effectiveness of rock burst disaster warnings, contributing to the safety and sustainability of coal resource extraction. Further refinement and exploration of these indicators offer promising avenues for advancing rock failure monitoring and early warning capabilities in coal mines.

Simulation and solution of a proppant migration and sedimentation model for hydraulically fractured inhomogeneously wide fractures

The distribution of proppant during hydraulic fracturing may directly contribute to the flow conductivity of the proppant fracture, so research on the migration and sedimentation of proppant in the fracture and the final distribution pattern is of great relevance. The mass conservation equations of proppant solids and fracturing fluid were adopted to describe the distribution of proppant migration and sedimentation in the fracture, improving the additional gravity coefficient by utilizing the density difference between proppant and fracturing fluid and the concentration of proppant, together with the proppant sedimentation velocity at different Reynolds numbers in this study. The flow coefficients were obtained by discretizing the system of equations through the finite volume method combined with the harmonic mean method and the upstream weight method. The concentration additional pressure gradient term was computed by using the Superbee format innovatively to improve the solution convergence of the model. Numerical simulations with identical parameters were compared with indoor test results, which fully verified the correctness of the model and the accuracy of the discrete solution based on the finite volume method. The effects of flow rate of fracturing fluid, ratio of injected sand, viscosity of fracturing fluid, grain size of proppant and density of proppant on proppant migration and sedimentation based on three elliptical fracture morphologies: even-wide, top-wide and bottom-narrow as well as top-narrow and bottom-wide were investigated and analyzed through comparing the rate of proppant front movement, the level of sweeping range and the degree of inhomogeneity in the range under different conditions. Findings of this study suggest that: (1) top-wide and bottom-narrow fractures are more preferable for homogenous sanding in the early stage of proppant injection, and top-narrow and bottom-wide fractures are best for sanding in the later stage; (2) the viscosity of fracturing fluid is the most influential factor on proppant migration and sedimentation, which increases in the range of 100 mPa.s to enhance the sweeping range and homogeneity of proppant sanding and therefore achieve a better fracturing effect.

Study on the Mechanism Effect of Bending Loads on the Decay-like Degradation of Composite Insulator GFRP Core Rod

This paper investigates the deterioration of, and the abnormal temperature rise in, the GFRP core rod material of compact V-string composite insulators subjected to prolonged alternating flexural loading under wind-induced stresses. The axial stress on the GFRP (Glass Fiber Reinforced Plastic) core rod, resulting from transverse wind loads, is a focal point of examination. By establishing a stress model and damage model, the paper simulates and computes the evolution of damage in the outer arc material of composite insulator core rods subjected to alternating flexural loads. Additionally, a multi-factor coupled aging platform is set up, integrating humidity, heat, and mechanical stress, to simulate the crazing deterioration process of composite insulators under alternating flexural loads. Experimental results reveal that during 400,000 alternating load cycles, the core rod underwent stages of surface damage, damage increasing, fatigue embrittlement, matrix hydrolysis, and fiber fracture. Simultaneously, the silicone rubber sheath on the outer side of the composite insulator’s bending arc develops cracks over aging time, creating pathways for moisture ingress into the interface and core rod. The dielectric constant and dielectric loss factor of the aging region of the core rod increase to varying degrees compared to the non-aging part. Moreover, the degree of abnormal heating of the samples intensifies with the duration of aging experiments. These findings underscore the significance of understanding the aging and decay-like fracture process of compact line V-string composite insulators. They provide crucial insights for future research aimed at enhancing the material properties of composite insulator core rods.

Plastic and damage energy dissipation characteristics and damage evolution of Beishan granite under triaxial cyclic loading

The damage and failure of rock under triaxial stress is an irreversible process of energy dissipation, which mainly includes plastic energy dissipation and damage energy dissipation. However, it is difficult and rare to separate plastic energy dissipation and damage energy dissipation and to conduct relevant research on this basis. In this work, a loading control method with a combination of load (0.5 kN/s) and circumferential deformation (0.01 mm/min) was used, and triaxial cyclic loading and unloading tests under five different confining pressures were performed on granite from the Beishan site area of China's high-level radioactive waste repository. The results indicate that the angle between the main fracture surface and the longitudinal axis increases with the increase of confining pressure. According to the characteristics of the stress–strain curve and energy dissipation, the test process can be divided into five stages: the initial compaction and elastic stage, the stable crack growth stage, the unstable crack growth stage, the postpeak unstable fracture stage and the residual stress stage. Importantly, a separate determination method of plastic energy dissipation and damage energy dissipation was proposed, and the evolution characteristics of plastic energy dissipation and damage energy dissipation were revealed. The ratio of plastic energy dissipation to input energy decreases slightly in the initial compaction and elastic stage, stabilizes at a low level in the stable and unstable crack growth stages, increases significantly in the postpeak unstable fracture stage and remains at a high level in the residual stress stage. Meanwhile, the ratio of damage energy dissipation to input energy increases slightly before the unstable crack growth stage, increases abruptly at the end of the unstable crack growth stage and the initial part of the postpeak unstable fracture stage, then declines rapidly, and finally remains at a low level. Furthermore, the qualitative and quantitative research results of damage evolution show that the plastic shear strain and damage variable established by damage energy dissipation can qualitatively and quantitatively describe the damage evolution of Beishan granite respectively. Finally, the verification results of Beishan granite and two other rock types show that the separation method for calculating plastic energy dissipation and damage energy dissipation proposed in this work has good adaptability, and the qualitative damage development analysis based on plastic shear strain can be verified and supplemented with the quantitative damage development analysis based on energy theory.

From macro-morphology to micro-mechanics: a deep dive into hydraulic fracturing of compacted bentonite

A series of injection tests with compacted Gaomiaozi bentonite of varying dry density were performed using an innovative testing apparatus for hydraulic fracturing visualization, with emphases placed on fracturing macro-morphological dynamics and micro-mechanical mechanisms. Results showed that fracturing dynamics mainly consisted of three stages, namely the hydrating stage, the cracking stage, and the fracturing stage. As dry density increased, the circular hydration zone expanded, the cracking network became more intricate, and the fracturing pattern transitioned from long and clear to short and fuzzy. Breakthrough time and breakthrough pressure increased exponentially with increasing dry density, while injection rate decreased exponentially and breakthrough water volume increased linearly. The fracturing mechanism in compacted bentonite was turning from tensile to shear mode with increasing dry density. By comparing the shear strength with the sum of swelling pressure and tensile strength, a simple criterion for determining the limit state between tensile and shear modes was established, which can be popularized in other soils without swelling potential but under different confining pressures. Finally, a novel calculation method for breakthrough pressure was proposed based on cavity expansion theory, taking into account swelling effects and fracturing failure modes.

Investigating the binding and mechanical properties of carbon nanotube-encapsulated Si nanowires: A perspective from atomic simulations

Atomic simulations using classical mechanics formalism are used to investigate the interfacial binding between CNTs and silicon nanowires as well as mechanical properties of the CNTs encapsulated silicon nanowires systems. The simulations provide the effect of temperature, systems' cross-sectional radius, interfacial distance, applied tension on their binding degree and deformation behaviors. The simulation results reveal that the spacing and interfaces between CNT and nanowire significantly affect thermal stability and the degree of interfacial binding in the systems. The Lode-Nadai values' distributions in the systems provide insight into the loading states on the atoms both in CNTs and silicon nanowires during tension. The atomic hydrostatic pressures can be used to identify stress-transfer paths in the systems during the elasticity, plasticity, and fracture stages.

Thermal infrared spectrum variation and waveband features of loaded rocks with different mineral components during the fracture evolution process

Previous studies focused mainly on temporal-spatial analyses of thermal infrared radiant temperature variations based on statistical parameters for rocks. These spectral analyses indicated that the thermal infrared radiance variation during the rock loading and fracturing process was a combined effect of the changes in both temperature and emissivity variation. The spectral features and mechanisms responsible for the thermal infrared spectral radiance changes in the fracturing stage and the relationship to the lithology remain poorly understood. In this paper, three types of typical rocks on the earth ground surface with different mineral components, i.e., sandstone, granite, and marble, were selected to investigate the thermal infrared spectrum (8.0–13.0 µm) waveband regulation during the loading process in the outdoor condition. The experiment yielded the following results: (1) The advantageous waveband corresponded to the reststrahlen feature (RF) waveband of the static emissivity spectrum, which was in the 8.2–9.4 μm, 8.4–10.3 μm and 11.1–11.4 μm range for sandstone, granite, and marble, respectively. There is a significant influence on the thermal infrared radiance variation caused by the waveband range. (2) The emissivity changes during the fracturing stage were the main factors causing the spectral radiance change, with opposite waveband features of the temperature change leading to an overall increase in amplitude. (3) The combination of spectral features in the advantageous waveband was more conducive to the analysis of the temporal-spatial-strength evolution of the thermal infrared radiation (TIR) temperature field on the loading rock surface. These results provide a scientific basis for thermal infrared remote sensing satellite loading design and waveband optimization and combination configuration.

Optimization design of oil well fracturing scheme in X block of Daqing Oilfield

With the continuous development of oil fields, the remaining oil in conventional old oil fields is gradually reduced after long-term water drive development. Fracturing can change the original water drive flow channel and increase the oil production of oil Wells. After long-term water flooding development, the oil production of oil Wells in Block X of Daqing oilfield has gradually decreased, and fracturing is needed to increase production. However, Block X has three target reservoirs, and the two formations are close to each other, so stratified fracturing cannot be realized by conventional stage fracturing technology. Therefore, flow limiting method is needed to control the fracture initiation of oil formations. And each layer can be better used. The overall fracturing effect is poor, and it is necessary to carry out a separate optimization design for the control technology of fracture height. The overall fracturing sequence is: first press the third stage, then press the first stage and the second fracturing stage. There is no interference between the 19th layer and the 20th layer, and the fracturing effect is good. For the 19th small layer, the fracture half-length is about 48m, and the 20th small layer half-length is about 55m, which achieves the expected fracturing effect.

Effect of electrode attachment location for transcutaneous electrical nerve stimulation for pain relief in lumbar vertebral body fractures.

[Purpose] This study aimed to investigate the effect of the location of electrode attachment in transcutaneous electrical nerve stimulation on pain relief in patients with lumbar vertebral body fractures. [Participants and Methods] This study included 59 patients with lumbar vertebral body fractures, who were randomly assigned to receive transcutaneous electrical nerve stimulation to the lumbar region, lower limbs, or upper limbs, or no treatment, over a 4-week period. Pain, activities of daily living, and pain catastrophizing were assessed. [Results] Compared with the control group, transcutaneous electrical nerve stimulation to the lumbar region or lower limbs significantly reduced pain levels in the first 2 weeks. Although, activities of daily living and pain catastrophizing improved over time, no significant differences were observed between the groups. [Conclusion] Transcutaneous electrical nerve stimulation provides pain relief to patients during the early stages of lumbar vertebral body fractures. However, it had no effect on the activities of daily living, pain catastrophizing, or long-term pain-relief. For lumbar vertebral body fracture pain relief, transcutaneous electrical nerve stimulation electrodes should be attached to the lumbar region or lower limbs.

Research on the evaluation method of rock brittleness characteristics based on stress-strain curve

Abstract In this study, not only the variability of the internal texture of rocks is considered in the in-depth investigation of the brittle fracture properties of rocks, but also the effects of different stress states and temperature factors on the fragility of rocks are focused on. Through experimental studies and data analysis of various types of rocks under different stress conditions and temperature environments, this study found that the plasticity of marble is positively related to stress. Under other stress states of 5, 15, 25, and 35 MPa, the stress-strain curves become flatter with increasing stress. Under uniaxial stress condition, the fragile strengths of different rocks are sandstone, red sandstone, granite, marble, chert, and cement mortar in that order. Whereas, under triaxial stress condition, the fragility of the rock samples was in the order of fine-grained granite, coarse-grained granite, sandstone, tuff, and marble. It was further found that the rock specimens after different high-temperature water-cooling treatments exhibited four different stages of brittle fracture, and the peak of the first stage of the rock was higher as the temperature decreased. The inclination of the peak was inversely proportional to the temperature. This study provides an essential scientific basis for the in-depth understanding of the brittle fracture characteristics of rocks and their engineering applications.

Nicotinamide mononucleotide enhances fracture healing by promoting skeletal stem cell proliferation.

The process of skeletal regeneration initiated by stem cells following injury, especially in fractures, is significantly impaired by aging and adverse factors. Nicotinamide mononucleotide (NMN), a critical endogenous precursor of nicotinamide adenine dinucleotide (NAD), has garnered extensive attention for its multifaceted regulatory functions in living organisms and its wide-ranging therapeutic potential. However, whether NMN contributes to trauma-induced skeletal regeneration remains unclear. Methods: The transverse femoral shaft fracture model was employed to evaluate the potential advantages of NMN administration for overall repair during the initial fracture stages in male mice through micro-CT analysis, histochemistry, and biomechanical testing. The pro-proliferative function of NMN on skeletal stem cells (SSCs) was investigated through flow cytometry, qRT-PCR, NAD content measurement, and cell proliferation assay. Results: In this study, we observed that the administration of NMN during the initial phase of fracture in mice led to a larger callus and corresponding improvement in micro-CT parameters. NMN enhances the cartilaginous component of the callus by elevating the NAD content, consequently accelerating subsequent endochondral ossification and the fracture healing process. Subsequent analyses elucidated that NMN was beneficial in promoting the expansion of diverse stem cells in vivo and in vitro potentially via modulation of the Notch signaling pathway. Moreover, the depletion of macrophages profoundly obstructs the proliferation of SSCs. Conclusion: Our discoveries provide a potential strategy for enhancing fracture healing through stimulation of callus SSC proliferation at an early stage, shedding light on the translational value of NMN as an enhancer for skeletal regeneration and highlighting the pivotal role of macrophage-stem cell interactions in governing the regenerative influence of NMN on stem cells.