Rock Mass Deformation Research Articles

Deformation damage mechanism and strength criterion of columnar jointed rock mass under true triaxial condition

To accurately understand the anisotropic mechanical properties of columnar jointed basalt distributed in the Baihetan Hydropower Station, indoor true triaxial loading physical model tests were conducted with different joint angles (β = 0°–90°) to study the strength deformation and failure mode of columnar jointed rock mass (CJRM). The results indicate that the strength anisotropy characteristics of CJRM under different stress environments are significant. The peak strength shows a U-shaped (σ2 = 2 MPa, σ2 = 4.5 MPa), W-shaped (σ2 = 3 MPa), and linearly increasing (σ2 = 5 MPa) rule of change. The increments in peak strength of CJRM varied significantly with the intermediate principal stresses, with average increments of 29.0% (σ2/σ3 = 1.5), 48.8% (σ2/σ3 = 2.25), and 45.4% (σ2/σ3 = 2.5); ε3 increases and then decreases with the change of inclination angle β, and the shear expansion phenomenon increases, ε2 decreases and then increases with the β, and the deformation characteristics of CJRM are that the expansion deformation transforms into compression deformation. The increase in σ2 shifts the rock features from moderate anisotropy to low anisotropy. According to the damage characteristics, the CJRM are classified according to three damage modes: (a) structurally controlled, (b) stress-controlled, and (c) stress-structurally controlled. Finally, Mogi–Coulomb strength criterion and Drucker–Prager strength criterion, which are applicable to true triaxial stress conditions, were used to verify the experimental results. The Mogi–Coulomb strength criterion fitted the strength parameters c and φ values, which showed a high degree of agreement with the in situ test results on site, indicating good applicability. The research results can scientifically and accurately predict and evaluate the stability of the Baihetan project.

Study on Construction Optimization Method of Tunnel Crossing Fault Fracture Zone

When a highway tunnel intersects a fault fracture zone, the excavation process disrupts the surrounding weak and fragmented rock mass, compromising the stability of the fault zone. This study compares the deformation and stress distribution of the surrounding rock using the reserved core soil method, central diaphragm (CD) method, and cross diaphragm (CRD) method during tunnel excavation through fault fracture zones. Among these, the CRD method is identified as the safest construction technique. Additionally, to address the significant deformation of the surrounding rock when tunneling through fault zones, the impact of various pre-support and advance reinforcement techniques on rock mass deformation is analyzed. By comparing the full-ring grouting method with the optimized reinforcement zone approach, the findings demonstrate that optimized grouting significantly reduces disturbance to the fault fracture zone during excavation, thereby enhancing the overall stability of the surrounding rock mass.

Investigation of rock mass deformation through nap-of-the-object photogrammetry: a case study of Hongyun Golden Peak in Fanjing Mountain, China

Investigation of rock mass deformation through nap-of-the-object photogrammetry: a case study of Hongyun Golden Peak in Fanjing Mountain, China

Distinct Element Simulation of Rock Mass Deformation Near Tunnels in Complex Geological Conditions, Guided by Statistical Experimental Design

Distinct Element Simulation of Rock Mass Deformation Near Tunnels in Complex Geological Conditions, Guided by Statistical Experimental Design

Risk classification assessment and early warning of large deformation of soft rock in tunnels based on CNN-LSTM model

Tunnels in the Western Plateau region of China often face numerous problems of high ground stress, as well as highly fractured and weak rock masses in deep sections of the tunnel, which results in an increased risk of large soft rock deformation in tunnels, posing substantial challenges to safe and efficient construction. Hence, risk assessment and establishment of an early safety warning system are essential. By examining factors affecting the large soft rock deformation in tunnels, a set of index system consisting of three primary indicators (i.e., hydrogeological conditions, design factors, and construction factors) and eight secondary indicators (i.e., strength-to-stress ratio, rock mass index, groundwater influence, groundwater influence, etc.) for assessing these risks is constructed, while the risk classification and identification criteria are also established. As an example, a tunnel on the Xicheng Railway is adopted for regression prediction of rock mass deformation and risk warning classification based on CNN-LSTM model. The results indicate that the model is effective in predicting rock mass deformation with minimal fluctuations in settlement data, a MAPE of 0.29525, and a RMSE of 6.1311. The model demonstrates a high accuracy rate of 91.67% for early risk warning prediction of soft rock deformation in the tunnel, moreover, when applied to 10 cross-sections of the Xicheng Railway Tunnel for deformation risk early warning, the model demonstrated a high prediction accuracy of 90%. which serves as a reference for the assessment and prediction of large deformation risks in similarly complex and challenging tunnels in the western region of China.

Research on the compressive deformation and re-bearing capacity characteristics of broken rock mass in deep roadway

Research on the compressive deformation and re-bearing capacity characteristics of broken rock mass in deep roadway

Study on mechanical properties and acoustic emission characteristics of composite rock mass with different thicknesses of weak interlayer

To study the influence of the thickness of a weak interlayer on the deformation and failure characteristics of composite rock mass. Based on the measured data of sand-mudstone interbedded floor rock mass in the Yima mining area, Henan Province, China. Using quartz sand, gypsum, and cement as similar materials make composite rock-like specimens with weak interlayers. The mechanical properties, deformation evolution process, failure characteristics, and acoustic emission laws of rock samples with different interlayer thicknesses under uniaxial compression were studied using the digital image correlation method and acoustic emission monitoring technology. The results show that: (1) With an increase in the thickness of the weak interlayer, there is a corresponding decrease in the compressive strength of the specimen. When the thickness of the weak interlayer exceeds 5 cm, the compressive strength of the composite rock specimen is even less than that of the single weak rock-like. (2) Under uniaxial compression conditions, the strain concentration zone first appears in the weak interlayer part of the composite rock-like specimen. As the pressure continues to increase, the specimen is the first to fail at the position of the maximum strain concentration zone. (3) The thickness of the weak interlayer is an important factor affecting the failure mode of composite rock-like specimens. With the increase of the thickness of the weak interlayer, the composite rock-like specimens change from overall failure to local failure. (4) With the increase of the thickness of the weak interlayer in the middle of the composite rock specimen, the maximum value of the energy released by the single acoustic emission event and the maximum value of the cumulative acoustic emission energy decrease during the compression failure process. The research results can provide a reference for the manufacture of composite rock mass with a weak interlayer and the deformation and failure analysis of composite rock mass.

Deformation and permeability of fractured rocks using fluid-solid coupling under loading-unloading conditions

Deformation and permeability of fractured rocks using fluid-solid coupling under loading-unloading conditions

Spatial deformation prediction method of fractured rock tunnel based on quantified GSI and its application

Determining rock mass mechanical parameters and accurately predicting tunnel deformation during tunnel construction remain challenging tasks. This study introduces a novel approach to calculate the Geological Strength Index by integrating indoor rock mechanics tests with geometric data from three-dimensional dense reconstruction. We utilized the Hoek-Brown strength criterion to develop a theoretical model for predicting tunnel deformation in fractured rock masses. Case studies reveal that the average value of Geological Strength Index for the Xiamen highway tunnel’s surrounding rock is 44. With support from the lining structure equivalent to 0.002–0.02 times the initial in-situ stress, the plastic zone thickness decreased by approximately 50%, and radial displacement was reduced by about 40%. Enhancing the lining structure’s support pressure significantly reduces the plastic zone radius and radial displacement. As the Geological Strength Index decreases, the nonlinearity between support pressure and plastic zone radius becomes more pronounced, with a similar trend observed for the relationship between support pressure and tunnel radial displacement. The relative deviation between predicted and measured values did not exceed 1.69%. The method accurately captures the effects of rock fragmentation and tunnel construction on plastic zone formation and displacement, offering an effective approach for the rapid and secure assessment of rock tunnel excavation stability using digital technology.

Experimental research on deformation response of hot dry rock (HDR) geothermal reservoir during hydraulic modification at 300 °C and depth 2500 m

Experimental research on deformation response of hot dry rock (HDR) geothermal reservoir during hydraulic modification at 300 °C and depth 2500 m

Deformation behaviour of strain-softening rock mass in tunnels considering deterioration model of elastic modulus

By analyzing the composite effects of the plastic shear strain and confining stress according to the laboratory test results, a model adopting a deteriorating elastic modulus for the intact rock is proposed. Soft rock such as coal and the strong rock such as granite with different quality are investigated. Geological Strength Index (GSI) is adopted to represent the integrity of rock, to be specific, from intact rock to the rock mass. Specifically, for the strain-softening rock mass, the elastic modulus is gained by introducing GSI into the deterioration model. The strength parameters are obtained by fitting GSI into Hoek-Brown failure criterion. Then, the elastic modulus and strength parameters of the rock mass are employed in the numerical procedure for solving out the rock deformation, the radii of the plastic softening and residual zones of the tunnels. The rationality of the numerical procedure is verified with the existing semi-analytical and analytical procedures. In the discussion, the influences of the critical plastic parameters and GSI, on the elastic modulus, rock deformation, radii of the plastic softening and residual zones are investigated. Five models for the variation of the modulus including the proposed deterioration model are defined. The rock mass deformation behaviours of the five models are compared. The results indicate that, in the plastic softening zone that is far away from the tunnel periphery, the elastic modulus is more sensitive to the plastic shear strain, whereas near the tunnel periphery, the elastic modulus is primarily affected by the confining stress. Regarding a linear decrease of the elastic modulus versus the plastic shear strain overestimates the elastic modulus to some extent, especially for the soft rock mass.

The impact of effective fractured rock mass properties on development of flow channeling in enhanced geothermal systems

The impact of effective fractured rock mass properties on development of flow channeling in enhanced geothermal systems

System Reliability Analysis of Concrete Arch Dams Considering Foundation Rock Wedges Movement: A Discussion on the Limit Equilibrium Method

In this paper, a discussion on the applicability and limitations of the limit equilibrium method is presented. In this manner, the reliability of a concrete arch dam-foundation system under static loading is evaluated by considering a set of potentially moveable rock wedges in the foundation. The safety of the system is assessed utilizing a quasi-analytical method, which employs the limit equilibrium method and numerical analysis to calculate the sliding safety factors and the dam trust forces, respectively. The reliability is evaluated using the Latin Hypercube Sampling method. Random variables in the system are the friction angle, cohesion, and the Grout Curtain Efficiency Coefficient. In the end, the influence of two parametric variables of discontinuities, elastic slip and rock mass deformability modulus, on the rock wedges’ sliding safety factor is evaluated by comparing the results of the quasi-analytical method with the purely numerical method. The results show that in the case of complicated geotechnical conditions, the limit equilibrium method may not reflect real-world failure scenarios.

Deformation and Stress of Rock Masses Surrounding a Tunnel Shaft Considering Seepage and Hard Brittleness Damage

The mechanical and deformation behaviors of the surrounding rock play a crucial role in the structural safety and stability of tunnel shafts. During drilling and blasting construction, seepage failure and hard brittleness damage of the surrounding rock occur frequently. However, previous discussions on stress deformation in the surrounding rock did not consider these two factors. This paper adopts the theory of elastoplastic to analyze the effects of seepage and hard brittleness damage on the stress and deformation of the surrounding rock of a tunnel shaft. The seepage effect is equivalent to the volumetric force, and a mechanical model of the surrounding rock considering seepage and hard brittleness damage was established. An elastoplastic analytical formula for surrounding rock was derived, and its rationality was verified through numerical examples. Based on these findings, this study revealed the plastic zone as well as stress and deformation laws governing the behavior of surrounding rock. The results showed that the radius of a plastic zone had a significant increase under high geostress conditions, considering the hard brittleness damage characteristics of the surrounding rock. The radius of the plastic zone increased with an increase in the initial water pressure and pore pressure coefficient, and the radius of the plastic zone increased by 5.5% and 3.8% for each 0.2 MPa increase in initial water pressure and 0.2 increase in pore pressure coefficient, respectively. Comparing the significant effects of various factors on the radius of the plastic zone, the effect of support resistance inhibition was the most significant, the effect of the seepage parameter promotion was the second, and the effect of the hard brittleness index promotion was relatively poor. The hard brittleness index and water pressure parameters were positively correlated with the tangential and radial stresses in the surrounding rock, and the radial stresses were overall smaller than the tangential stresses. The deformation of the surrounding rock was twice as large as the initial one when hard brittleness damage and seepage acted together. These findings can provide a reference for the stability evaluation of the surrounding rock in tunnel shafts.

Crack propagation process in double-flawed granite under compression using digital image correlation method and numerical simulation

The existence of flaws seriously weakens the rock strength, directly affects the crack expansion morphology, and indirectly affects the slope stability. In this study, uniaxial compression tests were carried out on double-flawed granite to investigate the effects of flaw angle on its compressive strength and crack coalescence based on DIC technology and PFC2D numerical simulation. The result indicates that the UCS values of flawed specimens at angles of 15°, 30°, 45°, and 60° are approximately 25.5–51.7% lower than that of the intact specimen. The failure strength of the double-flawed sample increases with the increase of flaw inclination angle, and the fracture morphology shifts from no expansion to split expansion. When the flaw tip strain of each flaw sample exceeded 0.6%, the stress concentration was generated at the flaw tip, and the sample began to appear macroscopic large cracks. DIC technique can well observe the crack initiation and propagation process, recording inclined shear strain bands at flaw tips, tensile strain bands in the middle of flaws, and tensile shear O-shaped strain ring in rock bridge areas. Numerical simulations using PFC2D software were carried out and showed a good agreement with the physical results. In addition, the effect of structural inclination on specimen failure strength is clearly explained by the theory of compressive damage based on the projected size of flaws. The deformation of rock mass is not a simple material deformation but is composed of material deformation and structural deformation. These experimental and numerical results enhance our understanding of crack initiation and coalescence characteristics, aiding in the analysis of rock structure stability in scenarios such as excavated underground openings, slopes, and tunneling construction, where pre-existing cracks or step-path fractures are pivotal to structural integrity.

Dynamic Simulation of Rock‐Avalanche Fragmentation

AbstractFragmentation is a common phenomenon in complex rock‐avalanches. The fragmentation intensity and process determines exceptional spreading of such mass movements. However, studies focusing on the simulation of fragmentation are still limited and no operational dynamic simulation model of fragmentation has been proposed yet. By enhancing the mechanically controlled landslide deformation model (Pudasaini & Mergili, 2024, https://doi.org/10.1029/2023jf007466), we propose a novel, unified dynamic simulation method for rock‐avalanche fragmentation. The model includes three important aspects: mechanically controlled rock mass deformation, momentum loss while the rock mass fiercely impacts the ground, and the energy transfer during fragmentation resulting in the generation of dispersive lateral pressure. We reveal that the dynamic fragmentation, resulting from the overcoming of the tensile strength by the impact on the ground, leads to enhanced spreading, thinning, run‐out and hypermobility of rock‐avalanches. Thereby, the elastic strain energy release caused by fragmentation becomes an important process. Energy conversion between the front and rear parts caused by the fragmentation results in the enhanced forward movement of the front and hindered motion of the rear of the rock‐avalanche. The new model describes this by amplifying the lateral pressure gradient in the opposite direction: enhanced for the frontal particles and reduced for the rear particles after the fragmentation. The main principle is the switching between the compressional stress and the tensile stress, and therefore from the controlled deformation to substantial spreading of the frontal part in the flow direction while backward stretching of the rear part of the rock mass. Laboratory experiments and field events support our simulation results.

Experimental Investigation on Failure Characteristics of Pre-Holed Jointed Rock Mass Assisted with AE and DIC

For jointed rock mass with anisotropy and discontinuity, the structure of the surrounding rock is constantly developing and changing during tunnel excavation. It is difficult to reasonably predict localized deformation of jointed rock mass by using the existing rock mechanics theory. In this paper, the failure characteristic of pre-holed jointed rock mass with three joint angles is experimentally investigated by adopting the digital image correlation and acoustic emission methods. To avoid the influence of measurement error on Digital Image Correlation (DIC) from discontinuous deformation, parametric studies and an optimized algorithm are also included in DIC tests. Results indicate that the perpendicular-jointed condition (0° joints) is the most dangerous situation because of its comparatively lower strength and brittle failure mode with a shift energy release. For rocks with different jointed angles, localized deformation emerges after the material enters the plasticity. Significant localization occurs after the failure with cracks surrounding the center hole and pre-existing joints.

Assessment of the influence of natural thermal cycles on dolomitic limestone rock columns: A 10-year monitoring study

Assessment of the influence of natural thermal cycles on dolomitic limestone rock columns: A 10-year monitoring study

The Influence of Grain Size Gradation on Deformation and the Void Structure Evolution Mechanism of Broken Rock Mass in the Goaf

The high porosity and high specific surface area of the broken rock mass in abandoned mine goaf make it an excellent thermal storage space. The void structure is an important factor that affects the permeability characteristics of broken rock mass, which determines the efficiency of extracting geothermal water from abandoned mine shafts. To accurately describe the void structure of broken rock mass, the effect of particle erosion on the fracture of rock blocks is considered in this study, based on which an impact-induced strength corrosion calculation model was proposed. Then, this calculation model was embedded into the three-dimensional numerical simulation of broken rock mass for secondary development. A discrete element numerical calculation model was established for broken rock masses with different size grading distributions under water immersion and lateral compression conditions. On this basis, considering the strength erosion effect of impacts, this study investigated the deformation and fracture characteristics of broken rock masses with different size grading distributions and analyzed the evolution laws of porosity in the broken rock masses. The main findings are as follows: The impact effect has a significant influence on the growth of microcracks and the breakage rate of broken rock mass. When the particle size of the broken rock mass differs significantly (size grading as G3), impact-induced strength erosion exerts the greatest impact on the growth of microcracks and the breakage rate. When the particle size of the broken rock mass is uniform (size grading as G1), impact-induced strength erosion minimally impacts the secondary fracturing of the broken rock mass. When the strain of the broken rock sample is less than 0.175, the distribution of microcracks is scattered; when the strain reaches 0.275, microcrack propagation accelerates and exhibits a clustered distribution; and when the strain reaches 0.375, microcracks exhibit a reticular distribution and their connectivity is enhanced. With the increase in deformation, the broken rock mass porosity decreases, and the porosity curve fluctuates along the z-axis with a decreasing trend and gradually becomes more uniform. This study provides a theoretical foundation for assessing the efficiency of extracting and storing mine water with heat in abandoned mine geothermal mining projects.

A hybrid finite-discrete element method for modelling cracking processes in sandy mudstone containing a single edge-flaw under cyclic dynamic loading

Rock mass deformation and failure are macroscopic manifestations of crack initiation, propagation, and coalescence. However, simulating the transition of rocks from continuous to discontinuous media under cyclic dynamic loading remains challenging. This study proposes a hybrid finite-discrete element method (HFDEM) to model crack propagation, incorporating a frequency-dependent cohesive-zone model. The mechanical properties of standard sandy mudstone under quasi-static and cyclic dynamic loading were simulated using HFDEM, and the method's reliability was verified through experimental comparison. The comparative analysis demonstrates that HFDEM successfully captures crack interaction mechanisms and accurately simulates the overall failure behavior of specimens. Additionally, the effects of pre-existing flaw inclination angle and dynamic loading frequency on rock failure mechanisms were investigated. The numerical results reveal that rock samples exhibit significantly higher compressive strength under dynamic loading compared to quasi-static loading, with compressive strength increasing with higher cyclic dynamic load frequencies. Furthermore, by analyzing the strength characteristics, crack propagation, and failure modes of the samples, insights into the failure mechanisms of rocks under different frequency loads were obtained. This study provides valuable insights into crack development and failure of rocks under seismic loads, offering guidance for engineering practices.