Characteristics Of Rock Fracture Research Articles

Quantification of artificially induced microcracks and their effects on hard rock fragmentation performance and mechanical response characteristics

Microcracks have a significant effect on the physical and mechanical properties of rocks. Inducing artificial microcracks in rocks can reduce rock strength and decrease the energy required for rock fragmentation. Nevertheless, few attempts have been made to investigate the effect of microcracks on rock fragmentation performance and mechanical behavior, especially from the perspective of microcrack quantification. For this end, we heated granite samples to induce different degrees of microcracks. However, the parameters of microcracks are difficult to control. For the purpose of accurately characterizing the distribution of microcracks, we measured the microcrack parameters in detail. We visualized microcracks using the fluorescent epoxy method and quantified the microcrack parameters by image processing. Such a method suffered at the expense of losing some of the extremely small microcracks. But, on the other hand, a much larger field of view area is assured, allowing the data to be more representative. After the quantification of microcracks, we performed indentation tests on samples containing microcracks to analyze the mechanical response of tool-rock interaction and crater parameters. The results show that the lengths of individual thermally induced microcracks are distributed between 0.2 and 1.1 mm. At higher temperatures, thermal microcracks are dominated by intragranular microcracks leading to a more uniform distribution. The presence of microcracks can affect the fracture characteristics of rocks and a threshold exists. Compared with the unheated sample, a fivefold increase in the density and total length of microcracks reduces the peak force by 88% and 54%, and the absorbed energy by about 90% and 68%, respectively. Additionally, the comprehensive parameter (i.e., fractal dimension) is not an effective parameter in analyzing microcracks, and a single absolute metric (e.g., crack density, length, number, etc.) is recommended. This study is expected to provide a new perspective to understanding the relationship between microcrack parameters and rock fragmentation, and to provide a reference for applied research on new drilling techniques.Our study enhances the efficiency of drilling in hard rocks for geothermal resources by elucidating the role of microcracks in rock fragmentation. This research aligns with the goals of sustainable and cost-effective subsurface engineering, contributing to a net-zero energy future.Our research elucidates microcracks in improving hard rock geothermal drilling efficiency, and aiding a net-zero energy future.Our research aims to improve drilling efficiency in deep geoenergy for a net-zero.

Evolution Characteristics of Strain and Displacement Fields in Double-Hole Short-Delay Blasting Based on DIC

In the process of porous blasting excavation in engineering projects such as mining, hydropower stations, and tunnels, the delay time between adjacent blast holes significantly influences the characteristics of rock fracture and fragmentation. In order to visually explore the changing characteristics of strain and displacement between adjacent blast holes under different delay times, polymethyl methacrylate (PMMA) plates were used to simulate rock materials, and 2D digital image correlation (2D-DIC) testing methods were employed to measure the explosive strain field with different delay times (0 µs, 5 µs, 15 µs, 40 µs, 70 µs) for dual holes. Full-field principal strain cloud maps and displacement fields of PMMA boards in two-dimensional spatial coordinates were obtained, and the representative monitoring points were analyzed. The experimental results show that the maximum values of the first compressive principal strain peak and the first tensile principal strain peak at the connecting center of the two holes exist at a delay time of 0~40 µs under blasting conditions with the same hole distance and single hole charge. At the center point of the connection between the two holes, the interval time between the two principal strain peaks decreases with the increase in delay time. The maximum principal strain on the central vertical line of the connection line decreases exponentially with the increase in hole distance, and the attenuation trend increases first and then decreases with the delay time between 0 and 40 µs. At the peak of strain, the maximum average displacement of the connecting center of the two holes exists in the delay time between 0 and 40 µs. With the increase in delay time, the displacement trend between the two explosion holes gradually changes from shear to tension, and the vulnerable damage area increases, which makes the communication between the two explosion holes easier. This study can provide a basis for the precise selection of delay times between blasting holes in engineering.

Effect of high temperature on the mixed mode I-II fracture characteristics of hot-dry rock

To investigate the variation law of rock fracture characteristics with temperature in hot-dry reservoirs, the pure mode I, pure mode II and mixed mode I-II loading experiments were carried out on sandstone and granite at room temperature and after high-temperature (100 °C, 300 °C, 500 °C and 700 °C) treatment by using the central cracked Brazilian disk (CCBD) specimen. The changes of parameters such as failure load, fracture toughness and fracture envelope with temperature were discussed, and the changes of rock mineral composition and fracture surface morphology were analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The results showed that the influence of temperature on the fracture characteristics of sandstone and granite presents different evolution laws.With the increase of temperature, the failure modes of sandstone and granite all change from brittle failure to ductile failure, but the critical temperature of the transition is different. Granite shows obvious ductile failure characteristics at 500 °C, while sandstone shows slight ductile failure characteristics at 500 °C.The failure load and fracture toughness of sandstone increase first and then decrease with the increase of temperature, which indicates that within a certain range, the temperature has a toughening effect on sandstone, and can improve its failure resistance. However, the failure load and fracture toughness of granite always decrease with the increase of temperature, which indicates that the temperature only has a deteriorating effect on granite. In the range of 100 °C to 500 °C, the temperature enhances (sandstone) or weakens (granite) the mode I fracture toughness of rocks more than it enhances or weakens the mode II fracture toughness. However, when the temperature is 700 °C, the temperature weakens the mode II fracture toughness more than the mode I fracture toughness. The area enclosed by the fracture envelope of sandstone first increases and then decreases with the increase of temperature, while the area enclosed by the fracture envelope of granite decreases with the increase of temperature. As the temperature increases, the tortuosity of the crack paths in sandstone and granite increases, the cross-section morphology becomes rougher, and the internal fissures and fragmentation increase.

Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

Influence of tunnel axis stress on mechanical response and fracture characteristics of rock surrounding tunnel subjected to gradient stress

Influence of tunnel axis stress on mechanical response and fracture characteristics of rock surrounding tunnel subjected to gradient stress

Experimental study of fracture behaviors of granite at ultra-low temperatures

A good understanding of fracture characteristics of rocks at ultra-low temperatures is essential in selecting and designing cavernous liquefied natural gas (LNG) storage facilities. In this study, three-point bending tests on Notched Semi-Circular Bend (NSCB) granite specimens with various grain sizes and saturation levels were conducted at temperatures of 25°C, −90°C, −120°C, and −165°C, respectively. The test results show that the fracture characteristics of granite are significantly weakened at −165°C under saturated conditions. As the temperature goes low, granite’s peak strength, fracture toughness, and fracture energy increase under dry conditions. A robust linear relationship between the mode-I fracture toughness (KIC) and the fracture energy of granite at ultra-low temperatures is established in this study. This relationship demonstrates that specimens with higher fracture toughness require more energy to reach their fractures. In addition, the relationship, along with its test constraints, forms a theoretical basis that can be used to explain the fracture damage modes and the characteristics of granite at different temperatures. Furthermore, granite at ultra-low temperatures was also investigated from the view of pores with frozen water and the change of particle sizes. The data obtained from our experiments can serve as valuable parameters for simulating underground LNG storage. The research findings from this study provide a valuable foundation that can be used for designing and installing cavernous LNG storage tank facilities.

Study on rock fracturing in smooth blasting under initial stress

In practical smooth blasting, rock fracturing is influenced by in-situ stress, which frequently leads to underbreak/overbreak and excavation damaged zone and consequently poses a serious threat to the safety of the excavated structure. This study systematically investigates the behaviour and mechanism of rock cracking under coupled initial stress and smooth blast utilizing experimental, theoretical, and numerical methods. Model experiments involving three-hole smooth blasting on 200 × 200 × 50 mm granite specimens are conducted under various static stresses. The resulting fracturing patterns are identified using the digital image correlation technique. The model testing examines rock cracking behaviours, fractal characteristics of rock fractures, and underbreak/overbreak. Experimental results indicate that the extents of rock fracturing and the fractal dimension in both the excavation and reserved zones show an overall decreasing trend as the static stress increases. Meanwhile, the area and depth of underbreak/overbreak also present a decreasing trend, suggesting that static stress is beneficial to the performance of smooth blasting. Then, the variations of crack patterns in model tests are theoretically analysed based on the transmission and superimposition of detonation stress waves combined with the static stress distribution near perimeter holes. Theoretical results emphasize the crucial role of the second hole and indicate no evidence of the third hole influencing the generation of connection fractures. The initial stress induces hoop tensile stress concentration on borehole-wall and generates the smallest hoop compression stress distributed vertically to the excavation line, which controls the initiation and extension of fractures in smooth blasting along the connection line of boreholes. Subsequently, the fracture evolution under coupled initial stress and smooth blast is numerically modelled using LS-DYNA. The numerical results vividly illustrate the necessity of a small burden to efficiently fragment the rock within the excavation zone when smooth blasting is applied to rock excavation under high in-situ stress.

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.

Thermal stimulation mechanical response and shear dilatation predictive model improvement of granite fractures in an enhanced geothermal system

The exploitation of shear dilatation behavior exhibited by natural rock fractures can serve as an effective strategy for stimulating reservoirs in the enhanced geothermal systems (EGS). However, few studies have considered the shear dilatation characteristics of rock fractures treated by real-time high temperature. Firstly, the self-developed Mechanical(M)-Thermal(T) coupling shear test cell and the MTS816.01 rock shear test system were used to carry out the direct shear tests of granite fractures. The M-T coupling effect on granite's physical properties such as cohesion, the mechanical properties such as shear strength, and strain energy characteristics such as dissipated strain energies were analyzed. On these Base, the shear dilatation mechanism of granite fractures treated by real-time high temperature is further revealed. Subsequently, based on the dynamic changes in the area degradation degree of granite fractures, the shear dilatation model of rock fractures treated by real-time high temperature were improved and verified. The results reveal that the M-T coupling effect can considerably impair the shear dilatation behavior of granite fractures. The temperature undermines the shear dilatation behavior of granite fractures by negatively affecting their physical and mechanical properties, while the normal stress deteriorates their shear dilatation behavior by constraining the normal displacement of the rock fractures. The modified shear dilatation model of rock fractures exhibits high accuracy and can accurately represent the shear dilatation behavior of rock fractures under M-T coupling effects. The novel insights provided in this paper contribute to a more comprehensive understanding of the wellbore stability and permeability improvement mechanism of EGS.

Study of hydro-mechanical behaviours of rough rock fracture with shear dilatancy and asperities using shear-flow model

The geometric properties of fracture surfaces significantly influence shear-seepage in rock fractures, introducing complexities to fracture modelling. The present study focuses on the hydro-mechanical behaviours of rough rock fractures during shear-seepage processes to reveal how dilatancy and fracture asperities affect these phenomena. To achieve this, an improved shear-flow model (SFM) is proposed with the incorporation of dilatancy effect and asperities. In particular, shear dilatancy is accounted for in both the elastic and plastic stages, in contrast to some existing models that only consider it in the elastic stage. Depending on the computation approaches for the peak dilatancy angle, three different versions of the SFM are derived based on Mohr-Coulomb, joint roughness coefficient-joint compressive strength (JRC-JCS), and Grasselli's theories. Notably, this is a new attempt that utilizes Grasselli's model in shear-seepage analysis. An advanced parameter optimization method is introduced to accurately determine model parameters, addressing the issue of local optima inherent in some conventional methods. Then, model performance is evaluated against existing experimental results. The findings demonstrate that the SFM effectively reproduces the shear-seepage characteristics of rock fracture across a wide range of stress levels. Further sensitivity analysis reveals how dilatancy and asperity affect hydraulic properties. The relation between hydro-mechanical properties (dilatancy displacement and hydraulic conductivity) and asperity parameters is analysed. Several profound understandings of the shear-seepage process are obtained by exploring the phenomenon under various conditions.

Investigation on rock breakage by high-velocity water jet impact under different stress loading conditions: Fracture characteristic, stress and damage evolution laws

Numerical simulations were conducted based on SPH-FEM coupling method to investigate the damage evolutions and failure mechanism of rock impacted by a high-velocity water jet under different stress loading conditions. The influences of stress loading magnitudes and stress differences on the rock fracture characteristics, including parameters of broken pit morphology and crack propagation, were obtained. The development of damage and crack inner rock will be inhibited due to stress loadings. The rock failure mechanism in different breakage zones were revealed by exploring the damage and stress evolutions inner rock. The results show that the rock surface elements near jet impact center suffers from the instantaneous brittle failure, which is scarcely affected by stress loadings. The elements inner rock below jet impact and sidewall elements surrounding broken pit are destroyed due to the cumulative plastic damage, and the stress loadings delay the initial damage time and prolong the cumulative damage time.

Critical slowing down precursor information for the acoustic emission response characteristics of defective tuffs

Fracture characteristics of rock and rational structural design are necessary to ensure the stability of underground rock engineering. Early warning of rock damage is a hot and challenging issue for research in geotechnical engineering. In this paper, uniaxial compression tests and acoustic emission (AE) tests were conducted on different defective specimens. The AE characteristics during rock damage were statistically analyzed based on the critical slowing theory. The results showed that the stress fluctuation in the stress–strain curve appeared earlier with the increase of initial damage. The failure pattern shifted overall from tensile to shear cracks. With the load increased, the AE amplitude changed from low amplitude and low density to high amplitude and high-density characteristics. The AE RA/AF was more sensitive to tiny cracks and had better immunity to attenuated AE signals. Both cumulative AE energy and RA/AF showed a precursor characteristic of a sudden increase in slope before rock damage. The AE b-value experienced a period of rising, fluctuation, and decline, with a sudden drop before the large-scale crack extension, showing a decreasing trend overall. The magnitude of fluctuations and density of distribution of the critical slowing down parameters (variance and autocorrelation coefficients) reflected the severity of specimen failure. The early warning characteristic of the variance was more significant, while the autocorrelation coefficient had an apparent disorder, which interfered with the judgment of the system phase transition. The average warning time of different AE parameters' “critical precursor point” was greater than 42 s, and the stress level was lower than 91.50%. The warning time sequence of different parameters in descending order was as follows: variance of AE parameters > autocorrelation coefficient of AE parameters > traditional AE parameters. The overall warning effect of the critical slowing down phenomena was better than that of classic AE parameters.

Experimental Investigation on the Influence of Wave Impedance on Dynamic Mechanical Response of Granites undergone High Temperature.

Wave impedance is an important physical quantity to characterize the dynamic properties of materials. To explore the influence of wave impedance on the dynamic mechanical response of rock, the granite samples with a wave impedance gradient change are obtained by changing the heating temperature, and the impact compression test is carried out by using a split Hopkinson pressure bar (SHPB) device. The stress wave propagation law, dynamic stress-strain relationship, and fracture characteristics of rocks with different wave impedances are studied comparatively, and the influence mechanism of wave impedance on the dynamic mechanical response of rocks is comprehensively analyzed from two aspects of material properties and dynamics. The results show the following: (1) Under the action of the same incident wave, the reflected wave amplitude, transmission wave takeoff time, peak stress, peak strain, and equivalent average size of fragments of granite samples with different wave impedances are significantly different. (2) As the heating temperature increases, the wave impedance of granite continuously decreases and the degree of damage intensifies. Within the high-temperature treatment range of 400 to 600 °C, there is a damage wave impedance threshold between 7854 and 3081 g·cm-3·m·s-1. Below this wave impedance, granite will appear to have significant damage deterioration. (3) Under the same incident wave, the strain rate and loading rate of granite samples show negative correlation and positive correlation with wave impedance, respectively. There is a progressive relationship between rock wave impedance, stress wave propagation, strain rate history/stress history, and dynamic mechanical response.

Experimental flintknapping with sandstones and prospection of lithic raw material sources from Cabra Corral area, Salta, Argentina

Within the framework of the project named Technological Variability and Social Interaction Networks in Northwest Argentina through the study of lithic technology strategies throughout the Formative period (Mercuri 2012) we collected samples of lithic raw materials in different portions of Las Conchas- Guachipas river area (Salta, Argentina) in order to create a reference collection. With part of this material we performed experimental lithic flintknapping with the aim to observe fractures and other characteristics that allow determining flintknapping quality so that we can understand and give a first reading to the selection of raw materials for making artifacts using local rocks.We present the results of these experiments conducted on sandstone, as it was the predominant raw material in the archaeological record. First results allow us to affirm that sandstone, given the availability and quality for flintknapping tasks constitutes an optimal raw material for the production of artifacts. We also note that the obtained edges are suitable for cutting work and the notches recorded in the artifacts are due probably to the characteristics of rock fracture.

Retracted: Mining Stress Distribution in Stope and Overlying Rock Fracture Characteristics and Its Disaster-Pregnant Mechanism of Coal Mine Earthquake

Retracted: Mining Stress Distribution in Stope and Overlying Rock Fracture Characteristics and Its Disaster-Pregnant Mechanism of Coal Mine Earthquake

Study on Mechanical Behavior and Mechanism of Sandstone under the Coupling Effect of Water Content and Dynamic Load

In the process of underground engineering construction, rock mass often faces the dual influence of dynamic load disturbance and groundwater, it is therefore essential to investigate the mechanical response of the rock mass under the coupling effect of dynamic load disturbance and water content. In this paper, dynamic load impact tests were carried out on sandstone with bullet velocities of 5 m/s, 10 m/s, and 15 m/s and water content of 0, 0.3, 0.6, and 0.9, and the mechanical behavior and mechanism response of water content to sandstone were investigated. The research findings indicate that this study has made significant contributions in quantifying the along grain and trans-grain fractures of microcracks. It has explored the influence of water content and dynamic loading on the strength mechanism of sandstone. It was discovered that the dynamic loading and water content significantly affect the ratio of along grain and trans-grain fractures, thereby influencing the dynamic behavior of sandstone. The findings suggest a negative association between rock strength and water content and that its peak strength rises as the bullet velocity rises. The fracture characteristics of rock are influenced by water content and bullet velocity. The sample’s fracture degree increases with an increase in water content, its particle size distribution map is evident, and there is a positive relation between bullet velocity and fractal dimension. The energy conversion mechanism of the rock is influenced by the water content, as the bullet velocity increases, the absorbed energy density of the rock becomes higher. Furthermore, the correlation between the absorbed energy intensity and density and its fractal dimension is quantified. It is found that energy density and strength are positively correlated. The greater the fractal dimension, the higher the energy density absorbed.

Damage characteristics and fracture behaviour of marble after cycle impact loading

Rock masses in underground engineering projects, such as roadways or pillars, are inevitably subjected to cyclic dynamic loading, and the damage behaviour of jointed rock masses is often influenced by the different characteristics of the preexisting rock damage. To investigate the effect of cyclic impact on the fracture characteristics of rocks, fracture tests were conducted using SCC (short core in compression) specimens with dissimilar impact damage. The experimental results showed that cyclic impact led to mesoscale fracture and strength deterioration in rock specimens. As the number of impacts increased, the dynamic peak stress of marble decreased, and the maximum strain and the energy absorbed by marble increased. At the same time, cyclic impacts generated continuous damage to the interior of the specimen, and the white spot inside the specimen with higher impact times was more obvious. Based on the fracture test results, the mode II fracture toughness was calculated, and it decreased by 6.9, 20.9, 43.3, 66.8, and 87.0% for specimens that underwent 1–5 cyclic impacts, respectively. After fracture, the three-dimensional topography characteristics of the fracture surface were obtained by a 3D optical scanner. Overall, the fracture surface became increasingly tortuous with increasing impact number. For the fractal factor D, the variation in the mean squared deviation of the asperity height and slope angle exhibited an increasing tendency with an increasing number of impacts.

Effect of heating–water cooling cycle treatment on the pore structure and shear fracture characteristics of granite

In hot dry rock (HDR) geothermal energy extraction systems, jointed rock masses are often subjected to heating–water cooling (H-WC) cycles. In this process, HDR is at risk of failure and instability due to the change in pore structure and fracture characteristics. To identify the shear fracture characteristics of rocks after H-WC cycle treatment. First, shear fracture mechanical tests were carried out on granite specimens treated with H-WC cycles by using the short core compression (SCC) test method. The experimental results show that cyclic H-WC treatment leads to a decrease in fracture toughness values. It is especially noteworthy that the weakening effect of fracture toughness decreases with increasing cycles. Second, the NMR analysis results show that the porosity of granite samples increases with the number of H-WC cycles. At 400℃ and 600℃, the pore size distribution changes under H-WC. The slope of the fitting curve between fracture toughness and porosity indicates that the higher the temperature is, the lower the sensitivity of fracture toughness to porosity. Then, acoustic emission characteristics in the mechanical experimental process were analysed by using the b-value analysis method. The results indicated that the b-value of acoustic emission decreased with increasing cycles at 200 °C, so the crack size and energy release increased; however, at T = 400 °C and 600 °C, the b-value increased with an increasing number of cycles, so the crack size and energy release decreased. Finally, the fracture plane morphology of the failure specimens was obtained by a 3D optical scanner. The calculation results of the fractal dimension DF indicate that the cyclic H-WC treatment enhanced the fracture plane roughness, and the average increase in fractal dimension DF increases with increasing temperature, also indicating that the increasing effect of fracture plane roughness with increasing temperature becomes increasingly significant. At the same time, the fracture toughness under cyclic H-WC action was negatively correlated with the fracture plane roughness of granite.

Implications for identification of principal stress directions from acoustic emission characteristics of granite under biaxial compression experiments

The rock fracture characteristics and principal stress directions are crucial for prevention of geological disasters. In this study, we carried out biaxial compression tests on cubic granite samples of 100 mm in side length with different intermediate principal stress gradients in combination with acoustic emission (AE) technique. Results show that the fracture characteristics of granite samples change from ‘sudden and aggregated’ to ‘continuous and dispersed’ with the increase of the intermediate principal stress. The effect of increasing intermediate principal stress on AE amplitude is not significant, but it increases the proportions of high-frequency AE signals and shear cracks, which in turn increases the possibility of unstable rock failure. The difference of stress in different directions causes the anisotropy of rock fracture and thus leads to the obvious anisotropic characteristics of wave velocity variations. The anisotropy of wave velocity variations with stress difference is probable to identify the principal stress directions. The AE characteristics and the anisotropy of wave velocity variations of granite under two-dimensional stress are not only beneficial complements for rock fracture characteristic and principal stress direction identification, but also can provide a new analysis method for stability monitoring in practical rock engineering.

Coevolution mechanism and branch of pillar‐overburden fissures in shallow coal seam mining

AbstractThe large‐scale mining of coal resources promotes the formation of section coal pillar groups between working faces. The overlying strata are supported by coal pillars, which leads to the formation of a unique fracture‐bearing structure in the key stratum, resulting in the evolution of fissures (cracks) and a generally high load on the supports. Studying the fracture‐bearing structure formed by coal pillars and overlying strata (fissures) is the basis for realizing rational mining of working faces. Here, the evolution characteristics of coal pillar‐overburden rock (fissures) in shallow coal seam mining and the working resistance of the support with stable fracture bearing structure of section coal pillar and overburden rock were studied in the No. 1‐2 coal mining of Longhua Coal Mine in Shenmu City, Northern Shaanxi. The fissure evolution characteristics on both sides of the coal pillar and the fracture‐bearing structure of the rock stratum were obtained by physical similarity simulation experiment. The mechanical calculation model of the coal pillar‐overburden rock (fissure) structure was established by theoretical derivation and calculation, and the working resistance of advanced support with a stable mechanical structure was studied. The research shows that the fracture evolution and rock fracture characteristics of a shallow coal seam mining face can be divided into three zones. Through the reanalysis of the mechanical structure of coal pillar‐overburden rock (fissure), the combined mechanical structure of the subkey stratum consisting of a lagging broken step rock beam structure and the main key stratum consisting of a hinged rock beam structure was obtained. Combined with the failure characteristics of the section coal pillar, a mechanical structure calculation method suitable for the bearing characteristics of section coal pillar support in shallow coal buried layers was obtained, and the field measurement results were verified.