Rock Mass Deformation Research Articles

New method to identify optimal discontinuity set number of rock tunnel excavation face orientation based on Fisher mixed evaluation

Discontinuity is critical for strength, deformability, and permeability of rock mass. Set information is one of the essential discontinuity characteristics and is usually accessed by orientation grouping. Traditional methods of identifying optimal discontinuity set numbers are usually achieved by clustering validity indexes, which mainly relies on the aggregation and dispersion of clusters and leads to the inaccuracy and instability of evaluation. This paper proposes a new method of Fisher mixed evaluation (FME) to identify optimal group numbers of rock mass discontinuity orientation. In FME, orientation distribution is regarded as the superposition of Fisher mixed distributions. Optimal grouping results are identified by considering the fitting accuracy of Fisher mixed distributions, the probability monopoly and central location significance of independent Fisher centers. A Halley-Expectation-Maximization (EM) algorithm is derived to achieve an automatic fitting of Fisher mixed distribution. Three real rock discontinuity models combined with three orientation clustering algorithms are adopted for discontinuity grouping. Four clustering validity indexes are used to automatically identify optimal group numbers for comparison. The results show that FME is more accurate and robust than the other clustering validity indexes in optimal discontinuity group number identification for different rock models and orientation clustering algorithms.

Probabilistic characterisation of rock mass deformation modulus from P-wave velocity based on information criteria

ABSTRACT Determination of rock mass deformation modulus (Erm ) is an important but very challenging task in rock mechanics and rock engineering. Direct measurements of Erm by in-situ tests are expensive, time-consuming, and sometimes even impossible. Since the nondestructive and easy geophysical method is commonly used to measure the P-wave velocity (Vp ) in the field, the study has developed an empirical correlation between Erm and Vp based on 834 collected datasets by considering both inherent and transformation uncertainties. The information criteria are employed to select the best model for deriving a general empirical correlation. The maximum likelihood estimation (MLE) method and computational intelligence techniques like particle swarm optimisation (PSO), artificial bee colony (ABC), and differential evolution (DE) algorithms are used to specify the incorporated parameters of each candidate model. Based on the derived general empirical equation, a Bayesian equivalent sample approach using Markov Chain Monte Carlo (MCMC) simulation is applied to conduct probabilistic characterisation of Erm by combining prior knowledge and project-specific observed Vp data. Comparative studies of the results from theory and in-situ measured Erm values suggest that the proposed method is effective and validate the applicability of the derived general empirical correlation.

Rock-mass heterogeneous rheological properties caused the formation of deep tension fractures

Tension failure is a unique phenomenon in solid Earth that occurs on scales ranging from large plate rift valleys to small laboratory rocks. On a slope scale, deep unloading tension fractures are distinct from conventional unloading fractures and are a unique geological phenomenon in valleys with high in-situ stress. To accurately reproduce the development and evolution of deep unloading tension fractures and to support major excavation projects, a series of works including geological investigation, laboratory tests, intrinsic model establishment, and numerical simulation were carried out in this study. The unloading rheological tests, accounting for time-dependent effects, uncover the heterogeneity in the rheological attributes of rock-mass strength parameters during valley downcutting. This heterogeneity manifests as a transition in rock-mass strength parameters that cohesion weakening-friction strengthening (CWFS). Drawing on the results of laboratory tests, a novel viscoelastic-plastic model, termed the WSR model, was proposed. This model takes into account both CWFS and rheological considerations. It has been applied to simulate deep unloading tension fractures in the Jinping I hydropower station (JP-I) and compared with conventional models. The results show that WSR model accurately reproduced the development and evolution of deep unloading tension fractures and the heterogeneity of rock-mass deformation during age evolution leads to the formation of deep unloading tension fractures. In this study, the rock-mass heterogeneous rheological properties were summarized as the heterogeneity of the rock-mass strength parameters during age deterioration and the heterogeneity of rock-mass deformation during age evolution; the WSR model was proposed to characterize the heterogeneous rheological property of rock-mass strength parameters and to reproduce the development and evolution of deep unloading tension fractures in the JP-I. This novel contribution to deep unloading tension fractures emphasizes that the rock-mass heterogeneous rheological properties lead to the formation of deep unloading tension fractures.

Characteristics of Micro-Seismic Events Induced by Ground Collapse-A Case Study in the Rongxing Gypsum Mine in Hubei Province, China.

Mining activities can damage rock masses and easily induce ground collapse, which seriously threatens safe production in mining areas. Micro-seismic systems can monitor rock mass deformation signals in real time and provide more accurate data for rock mass deformation analysis. Therefore, in this study, the waveform characteristics of micro-seismic events induced by ground collapse in the Rongxing gypsum mine were analyzed; the occurrence of these events was introduced on the basis of Fast Fourier Transform, an established Frequency-Time-Amplitude model, in order to put forward the index of energy proportion of the main band. The results showed the following. (1) The seismic sequence type of ground collapse was foreshock-mainshock-aftershocks. The interval between the foreshock and mainshock was longer than that between the mainshock and aftershocks. (2) The deformation corresponding to the foreshock micro-seismic events was mainly that of a small-scale crack. The deformation corresponding to the micro-seismic events during the mainshock was characterized by the gradual development of small-scale cracks, and the development of large-scale cracks accelerated, accompanied by slight rock collapse. The deformation corresponding to the micro-seismic events during the aftershocks showed that almost no small-scale cracks developed, and the large-scale crack development was intense, and accompanied by numerous rock and soil mass collapses. (3) The observed decreasing frequency distribution and energy dispersion can be used as possible precursors of ground collapse.

Study on multi-scale damage and failure mechanism of rock fracture penetration: experimental and numerical analysis

In natural rock masses, joints or fractures usually occur at different penetrations. To study the deformation and failure behavior of rock mass with different fracture penetrations, a series of triaxial compression experiments were conducted on rock specimens containing prefabricated fracture at penetrations of 0%, 25%, 50%, 75% and 100%. The results show that the greater the fracture penetration and the smaller the strength of the rock sample, the more obvious the plastic deformation section of the stress–strain curve. Confining pressure can greatly improve the compressive strength of rock samples. For intact rock samples, confining pressure will change the failure mode from tensile failure to shear failure. For fractured rock samples, the confining pressure will aggravate the degree of damage to the rock sample. PFC 3D simulation shows that the failure process of rock samples is accompanied by the transformation of strain energy to damping energy and particle sliding energy, which can quantitatively characterise the damage process of rock. The increasing trend of crack number is slow-steep-slow, which is the ‘S’ type. It began to grow rapidly after reaching peak strength and gradually stabilised after reaching residual strength. It is consistent with the trend of energy change.

Anomalous transport and upscaling in critically-connected fracture networks under stress conditions

Anomalous transport in fractured rocks is of high importance for numerous research fields and applications in hydrogeology and has been widely studied in the last decades. This phenomenon is due to the structural heterogeneities of fractured rocks and the high contrast between the fractures and matrix properties. At the same time, the fracture properties in terms of fracture density and geometrical characteristics are related to in-situ stress conditions that impact the connectivity of the system and the distributions of fracture aperture and length, including the creation of new cracks when the differential stress conditions are strong enough. In order to understand how all these features impact the observed anomalous transport, we study the role of in-situ stress in mass transport through a two-dimensional fractured rock. The fracture network is based on a real outcrop with a connectivity state around the percolation threshold, over which we simulate stress-dependent fracture deformation and propagation, and perform hydrodynamic transport through the deformed rock mass. The impact of the changes in aperture and the creation of new cracks on transport behavior is evaluated for various stress scenarios and reproduced with upscaled representations of transport processes. We also consider matrix diffusion as a source of anomalous transport and demonstrate that this process can be incorporated into the proposed upscaled models. Results showed that traditional upscaling methods with space-Lagrangian velocities description capture well the Gaussian-like breakthrough curves (BTCs) under low-stress ratio conditions, but fail under high-stress ratio conditions with multiple-peak early-times BTCs. To characterize the emergence of strong anomalous transport, we extend the Random Walk model Directed by a Markov Process with space-Lagrangian velocity sampling by incorporating multiple transition matrices conditioned by different initial velocity states. This new transport upscaling model shows high accuracy in predicting complex transport behaviors in critically connected fracture networks.

Analysis of the Influence of Surrounding Rock State on Working Performance of Cutting Head in Metal Mining

Continuous mining is one of the development goals for metal mines, and the application of coal mining equipment represented by shearers provides a reference for continuous mining. However, rock in metal mines is generally harder than coal, making cutting difficult. Improving the surrounding rock conditions is an important way to improve the applicability of the drum for hard rock cutting. Therefore, this article explores the correlation between drum-cutting performance and surrounding rock boundary conditions, aiming to obtain surrounding rock boundary conditions that can help improve drum-cutting performance. To achieve the goal, a model of a shearer drum and hard rock is established using finite element software. With the model, hard rock cutting was simulated and the stress distribution on rock mass, deformation of rock mass, and drum cutting force during the cutting process under different confining pressures were analyzed. Relations between drum cutting force and confining pressure on rock mass were obtained. Then, drum cutting force under different free surfaces of rock mass are studied and the positions of free surface on rock mass that help to reduce the drum cutting force were summarized. According to the research, when the rock mass is under uniaxial compression, drum cutting force increases with the confining pressure on the rock mass; In addition, the free surfaces on the rock mass are proved to be helpful to reduce the drum cutting force. The research content lays the foundation for the boundary conditions required to reduce drum-cutting force in metal mining.

A Novel Deformation Analytical Solution and Constitutive Model for Fractured Rock Masses

In order to study the deformation and stability of a fractured rock mass, existing research suggests that fracture deformation, which is usually obtained by evaluating the equivalent deformation modulus, dominates the deformation of a fractured rock mass. However, this parameter is difficult to obtain in theory and practice, which limits the application of rock mass deformation analysis methods. In order to calculate the deformation of fractured rock masses, the mass of the rock is regarded as a sponge-like material, and it is assumed that the deformation of a water-saturated fractured rock mass under external force load is approximately equal to the net flow of fracture water. Based on this assumption, firstly, the relationship between rock mass deformation and fracture flow is studied through a single-fracture rock mass model. The hydraulic properties of the fracture are characterized by the permeability coefficient, and the fracture deformation in the rock mass is equivalent to the fracture flow. The fracture deformation calculation formula is derived from the fracture hydraulics calculation formula, and this is compared with the measured data. The rationality of the calculation formula was verified. On this basis, the calculation formula for rock mass deformation, including multiple groups of fracture surfaces, is proposed, and the stress-strain constitutive relationship of a complex rock mass is established. The correctness of the calculation method was verified by comparing it with other theoretical calculation results.

A discontinuous smooth particle hydrodynamics method for modeling deformation and failure processes of fractured rocks

A discontinuous smoothed particle hydrodynamics (DSPH) method considering block contacts is originally developed to model the cracking, frictional slip and large deformation in rock masses, and is verified by theoretical, numerical and/or experimental results. In the DSPH method, cracking is realized by breaking the virtual bonds via a pseudo-spring method based on Mohr–Coulomb failure criteria. The damaged particles are instantaneously replaced by discontinuous particles and the contact bond between the original and discontinuous particles is formed to simulate the frictional slip and separation/contraction between fracture surfaces based on the block contact algorithm. The motion of rock blocks and the contact force of discontinuous particles are determined following Newton's second law. The results indicate that the DSPH method precisely captures the cracking, contact formation and complete failure across six numerical benchmark tests. This single smoothed particle hydrodynamics (SPH) framework could significantly improve computational efficiency and is potentially applicable to broad multi-physical rock engineering problems of different scales.

Characteristics of Methane Explosion and Dynamic Response of Rock Mass in an H-Type Roadway with Different Ignition Sources.

Methane explosion is an undesired incident in the coal mining industry. Its high pressure wave can cause damage to the rock mass. This study numerically investigated the flame and wave transport characteristics of methane explosion with ignition sources at three different locations, and the corresponding dynamic response of the rock masses was discussed. The results showed that the flame propagation time is shortest when the ignition position is located at the center of the H-type roadway structure and the maximum overpressure decreases as the ignition position deviates from the center of the H-type roadway structure. When the ignition point is located at the center of the H-type roadway structure, the smallest total deformation of rock mass shows up with the highest maximum overpressure. In contrast, the largest total deformation appears when the ignition point is most away from the center due to the asymmetric distribution of the gas pressure exerted on both sidewalls of the rock masses. This work may provide insights into the understanding of deflagration propagation and the dynamic evolution of stresses under complex conditions.

Estimation of Fracture Size and Probability Density Function by Setting Scanlines in Rectangular Sampling Window

Abstract Rock masses are very important materials in geotechnical engineering. In engineering rock mass, fracture is the relatively weak part of mechanical strength in rock mass and is the most important factor controlling the deformation, damage, and permeability of rock mass. Therefore, investigating fractures is very important for characterizing rock mass. This paper proposed a new approach by using uniformly equidistant orthogonal scanlines. Within the study context, the solution formula of fracture size is derived by establishing the space intersection model of arbitrary fracture and scanline, rectangular window, and a rectangular box with a rectangular window. Then, fractures were randomly generated in a certain size cube and compared with the traditional Kulatilake trace length integral evaluation method. The study results have shown that the proposed method is more reasonable and accurate. Then, this method was applied to an adit of Songta Hydropower Station. Finally, a new fracture diameter probability density estimation method was proposed, the fracture diameter of the normal distribution was verified, and the parameters of the probability density function obtained by the scanlines method were in agreement with the initial set parameters. In summary, the proposed scanlines method can well estimate the mean value of the fracture diameter and the probability density function of the fracture size.

A Pen206 Borehole Jack Suitability Assessment for Rock Mass Deformability Determination

A Pen206 Borehole Jack Suitability Assessment for Rock Mass Deformability Determination

Geotechnical and Geophysical Investigations of Estimating Rock Mass Properties

Accurate assessments of the deformation and strength properties of rock masses are essential for analysing the foundations, subsurface excavation, and construction of slopes, however, identifying geotechnical properties, particularly weak rock masses, is challenging for geoscientists, geologists, and geotechnical investigators. To determine the rock mass properties, geophysical techniques, and rock mass classification methods are widely used. Although rock classification methodologies exist, they are rarely employed in foundation construction analysis due to being predominantly established for tunnelling purposes. This study aims to employ classification methods, and geophysical and geotechnical investigation approaches to provide realistic rock mass properties for a building foundation, compare results, and assess techniques' effectiveness; it also reviews current state-of-the-art methods for classification techniques and investigations. Results show that compressional and shear wave velocities increase with depth indicating a change from poor to satisfactory mechanical behaviour, and empirical equations provide highly valuable and satisfactory deformation modulus values when compared to field seismic values. Almost all classification methods provided reasonable results compared with the seismic results, however highly overestimated and underestimated outcomes were obtained from some empirical equations applying the Rock Quality Designation index and Rock Mass Rating system. Empirical equations that gave the practical deformation modulus outcomes are the Rock Mass Rating based equations and Q-based equations and Geological Strength Index-based equations. Overall, the Rock Quality Designation index underestimated the seismic result, whereas the Rock Mass Rating, Q, and Geological Strength Index systems produced good agreement and realistic results. To conclude, classification methods were effectively applied to a building foundation. Since the Rock Quality Designation is a key value and feature for other systems including Q, and Rock Mass Rating systems, it is an essential factor. Although the Q systems provided practical consequences, this system mainly relied on the Rock Quality Designation value not the compressive strength of the intact rock. The Rock Mass Rating and being the most feasible and essential systems due to detailed geotechnical observations as inputs more significantly the uniaxial compressive strength of the intact rock, and various factors including deformation modulus, strength, Poisson’s ratio, equivalent cohesion, and friction angle of rock mass as outcomes.

Heat Production Capacity Simulation and Parameter Sensitivity Analysis in the Process of Thermal Reservoir Development

The development of a geothermal system involves changes in the temperature field (T), seepage field (H), stress field (M), and chemical field (C) and the influence among them and injecting the heat extraction working fluid into the injection well that flows (migrating) through natural fractures and exchanges heat with the geothermal high-temperature rock. At the same time, the injection of low-temperature working fluid will induce thermal stress, resulting in changes in the reservoir temperature field and stress field. To study the influence factors and influence degree of heat production performance and mining life under multi-field coupling in the process of thermal reservoir development, based on THMC multi-field coupling numerical simulation software, this paper deeply studies the control differential equations and boundary coupling conditions of rock mass (fracture) deformation, seepage, heat exchange, the chemical reaction, and other processes based on the numerical solution method of the discrete fracture network model, simulating heat production capacity during the deep geothermal resource extraction process. The reservoir geological model analysis and generalization, parameter setting, boundary conditions, initial condition settings, mesh generation, and other steps were carried out in turn. Two different heat extraction working fluids, water, and CO2 were selected for numerical simulation in the mining process. The changes in the thermal reservoir temperature, net heat extraction rate, and SiO2 concentration during the thirty years of systematic mining were compared. The results show that CO2 has a better heat extraction effect. Finally, the reservoir thermal conductivity, heat capacity, well spacing, injection temperature, fracture spacing, fracture permeability, fracture number, fracture length, and other parameters were set, respectively. The parameter variation range was set, and the parameter sensitivity analysis was carried out. The numerical simulation results show that the engineering production conditions (injection temperature, well spacing) have little effect on the thermal efficiency and mining life, and the properties of fractures (fracture permeability, fracture number, fracture length) have a great influence.

The time-dependent deformation and damage constitutive model of rock based on dynamic disturbance tests

Abstract In the deep rock excavation process, the rock will produce deformation and damage under multiple dynamic disturbances, while there is also unrecoverable time-dependent deformation. In order to research this deformation characteristic, a sine wave disturbance triaxial loading test was carried out on red sandstone to simulate the failure process of deep underground rock mass under dynamic disturbance loads with low confining pressure. Based on the results that the deformation of the rock increases suddenly during dynamic disturbances and varies with the number of disturbances, a novel disturbance damage model relating the number of disturbances to the deformation of the disturbances is created to describe the deformation and damage accumulation of the rock under multiple disturbances and an operator is developed to ensure that the model works. In order to describe the time-dependent deformation of rocks, the elasticity model in the traditional Bingham model was improved to a nonlinear elasticity model that varies with time, and its viscous and plasticity models were retained. The time-dependent deformation and damage constitutive model is obtained by combining the improved Bingham model with the disturbance damage model. The model parameters were identified according to the test data, and the finite-element calculation of the model was realized with the secondary development program. The results show the strain of rock increases suddenly under multiple disturbances, and the main reason for rock damage is the action of dynamic disturbances. The fitted curves and finite-element results are consistent with the experimental results. The time-dependent deformation and damage constitutive model of rock not only reflects the decaying rheological and steady-state rheological properties of rock under static loading but describes the characteristics of strain surge and disturbance damage accumulation caused by dynamic disturbances. This article contributes to the characteristics of the deformation of deep rock mass.

Estimation Criteria for Static Rock Mass Deformability Modulus for Rock-Socket Design in Metamorphic Rock Masses

This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.

Review on the Estimation of Static Deformability Modulus of Rocks and their adoptability in Different Rock Masses

The aim of this study is to review the different mechanisms employed in the estimation of static rock mass deformability modulus (𝐸𝑚) in rock engineering applications and to investigate the adoptability of the identified mechanisms in different rock masses. The paper discusses different evaluation criteria through experimental, empirical and other means, with their merits and demerits, including influential factors. It is known that deformability modulus of intact rock depends on the imposed stress, strain rate and the confining stress on the rock sample as well as the rock texture and structure. The results generated for 𝐸𝑚 by different in-situ tests are different and an appropriate in-situ test based on the rock mass conditions should be employed to obtain reasonable results. Empirical criteria are found to produce results of reasonable precision if appropriately adopted for specific rock mass conditions, while the back analysis method is widely adopted as an insitu estimation measure for the design of rock-sockets and tunnel support. It has also been reported that substantial reduction in 𝐸𝑚 occurs due to schistosity and larger test volumes, while it is sensitive to stress and discontinuity conditions. In this work, specific recommendations are made on the estimation of 𝐸𝑚 for different types of rock masses based on the findings and reviews reported in the literature.

Experimental study on instability mechanism and critical intensity of rainfall of high-steep rock slopes under unsaturated conditions

Two critical factors, namely intense precipitation and intricate excavation, can trigger rock mass disasters in mining operations. In this study, an indoor rainfall system was developed to precisely regulate the flow and intensity of precipitation. A large-scale model experiment was conducted on a self-designed physical simulation experiment platform to investigate the failure and instability of high-steep rock slopes under unsaturated conditions. The real-time reproduction of the progressive failure process in high-steep rock slopes enabled the determination of the critical rainfall intensity and revealed the mechanism underlying slope instability. Experiment results indicated that rainfall may be the primary factor contributing to rock mass instability, while continuous pillar mining exacerbates the extent of rock mass failure. The critical failure stage of high-steep rock slopes occurs at a rainfall intensity of 40 mm/h, whereas a rainfall exceeding 50 mm can induce critical instability and precipitation reaching up to 60 mm will result in slope failure. The improved region growing segmentation method (IRGSM) was subsequently employed for image recognition of rock mass deformation in underground mines. Herein an error comparison with the simple linear iterative cluster (SLIC) superpixel method and the original region growing segmentation method (ORGSM) showed that the average identification error in the X and Y directions by the method was reduced significantly (1.82% and 1.80% in IRGSM; 4.70% and 6.26% in SLIC; 9.45% and 12.40% in ORGSM). Ultimately, the relationship between rainfall intensity and failure probability was analyzed using the Monte Carlo method. Moreover, the stability assessment criteria of rock slope under unsaturated condition were quantitatively and accurately evaluated.

Multi-method joint monitoring study on strata behavior in shallow seam mining under bedrock gully

The Baijigou Coal Mine in Helan mountain mining area is alpine gully landform, and the double key stratums are cut by the gully. A two-dimensional physical similarity model under this condition was established in the laboratory. The strain field, deformation field and pressure field of the model are jointly and accurately monitored by BOTDA, DIC and pressure sensors. The rock behavior in shallow coal seam mining under bedrock gullies are studied. In the mining stage under the gully, the deformation of overburden is intense because overburden is thin, and the surface is easy to form a depression basin. In the mining stage far away from the gully, the deformed rock mass lacks horizontal support in the process of deflecting to the lower goaf, and the movement rock is in a multilateral block. The multilateral block rock periodically deflects and rotates, resulting in the periodic deformation and break of the inferior key stratum. At the mining stage of away from the gully, nine times of roof weighting occurred. And there are large and small periodic weighting phenomenon with the average roof pressure concentration coefficient is 1.37. The distance between the peak point of advance abutment pressure and the coal wall is 6–18 cm, and the influence distance decreases with the advancing of the working face. The inferior key stratum has a significant impact on the weighting process and the weighting strength. In the mining stage under the mountaintop, large downward inclined tension crack is prone to produce in the slope on the side of the stope line, and the roof weighting is the most severe. In the mining stage close to the gully, the overburden falls in layers from bottom to top, and the overburden at the slope toe is prone to slip. At the mining stage under the mountaintop and close to the gully, five times of roof weighting occurred. And the roof weighting concentration coefficient is 1.46 on average. The distance between the peak point of advance abutment pressure and the coal wall is always kept at 6–16 cm, and the influence distance is 33–41 cm. The study can provide a reference for mining design and ensures safe and efficient mining in this condition.

In-situ high-speed 3D-DIC experiment on blast-induced second free surface characteristics at initial stage of cut blasting in a tunnel

To obtain the law that blasting damage the rock mass and the evolution features of the second free surface, this study designed an in-situ tunnel blasting experiment and then got high-speed images using a three-dimensional digital image correlation (3D-DIC) method. The study clarified the movement law of rock mass in the inclined cut zone by analyzing the change of displacement fields under delayed blasting. After analyzing the off-plane displacement data collected from the cross-section, the study found the critical displacement criterion for rock failure, then analyzed the dynamic process and characteristics of the second free surface formation. The study shows that the cut blasting leads to the rapid extension of rock mass deformation in the cut zone and higher off-plane displacement. The focus of the study coincides with the cut-hole charging section, which is less affected by the smoke. The off-plane displacement value reached 204 mm at 26 ms. It is sufficient to analyze the complete rock breaking induced by cut blasting. Statistical analysis in the area not affected by smoke reveals that the rock mass will be damaged and thrown out if it is beyond a critical displacement value. This value is 100 mm here. The study inferred that under double-hole delayed blasting, the second free surface formed at 310 mm from the first initiated hole 11 ms after detonation. According to the extension velocity, it has three stages. The smoke diffusion rate is much lower than the free surface extension rate. The research content is crucial to reveal the quantitative relationship between cut parameters and rock-breaking effectiveness.