Study on the Influence of Structural Plane Dip Angle on Mechanical Properties of Surrounding Rock

Study on Rock Mechanics Response Characteristics of Through-Going Structures with Different Dip Angles

Through-going structures are widely distributed in rock masses of underground engineering, and their dip angles act as the core factor affecting the stress field and mechanical response of surrounding rock. To reveal the mechanical mechanism of rock masses containing through-going structures with different dip angles, this study adopts a combined method of theoretical derivation, indoor model testing and numerical simulation. Firstly, a plane strain mechanical model is established to classify Tectonically-induced Stress, Residual Gravitational Stress and engineering-induced stress, and the theoretical formulas for stress components, stress residual coefficient and stress deflection angle are derived. Secondly, rock-like specimens with through-going structures of various dip angles are prepared and biaxial compression tests are carried out to monitor mechanical parameters such as surrounding rock strain and peak strength. Finally, a large-scale numerical model is built by FLAC2D (version 7.0) software to simulate the whole process of stress equilibrium and excavation unloading of rock mass under a normal stress of 20 MPa. Then the data of principal stress, stress components, stress residual coefficient and deflection angle under different dip angles are extracted. The results show that the dip angle of through-going structure exerts a prominent regulatory effect on the rock mass stress field. With the increase of the dip angle, the Tectonically-induced Stress decreases continuously while the Residual Gravitational Stress rises gradually. The variation trend of stress deflection angle is highly consistent with structural dip angle, and the influence of Residual Gravitational Stress on deflection angle is limited. Due to the differences in loading modes and model sizes between indoor tests and numerical simulations, the evolution laws of stress residual coefficient show opposite trends, but both results verify the dominant effect of structural dip angle. Combined with theoretical, experimental and numerical results, the proposed theoretical system can effectively describe the stress evolution law of rock masses with through-going structures, which provides theoretical reference and technical support for the stability analysis of surrounding rock in similar underground engineering.

Research Progress on the Impact of Structural Planes on Tunnel Rockburst Based on Engineering Cases and Laboratory Tests

Rockbursts occur frequently in deep hard-rock tunnels, posing a major challenge to the safe and efficient construction of underground engineering. Engineering practice shows that in addition to high in-situ stress and hard brittle lithology, widely distributed structural planes in surrounding rock also significantly modify rockburst failure modes and intensity. This review systematically investigates structural-plane-controlled rockburst phenomena in deep hard-rock tunnels, based on 16 published field cases and more than 40 laboratory studies. First, we summarize the influence mechanisms of structural planes on tunnel rockbursts at the engineering scale through statistical analysis of case data. We then integrate existing experimental findings to analyze how the geometric and physical properties of structural planes alter rockburst behavior, from four perspectives: location (concealed/exposed), attitude (dip angle, strike, length), filling state, and multi-plane combination. We further synthesize multi-physical field response characteristics (acoustic emission, infrared thermal radiation, and surface strain field) from laboratory tests, and compare crack propagation and energy evolution patterns dominated by structural planes. The scale dependence of structural plane effects is discussed, highlighting consistencies and discrepancies between laboratory-scale mechanisms and field-scale engineering phenomena. Finally, we analyze rockburst mechanisms under the coupled action of structural planes and dynamic disturbances, and propose targeted engineering control strategies for different structural plane conditions. The purpose of this review is to integrate a set of analysis frameworks to establish the relationship between structural plane characteristics (location, attitude, filling state, and multi-plane combination) and multi-physical field responses, fracture evolution and energy evolution laws, as well as engineering-scale rockburst behavior. It is noteworthy that the engineering cases compiled in this review predominantly originate from deep hard-rock tunnels in China. The universality of the impact of structural planes on rockbursts still needs to be further verified by combining cases from different structural settings and engineering backgrounds.

Experimental Study on Rockburst Failure Characteristics of Deeply Buried Jointed Roadway Surrounding Rock Under True Triaxial Dynamic Disturbance

To investigate the rockburst failure characteristics and underlying mechanisms of deep straight-wall arch roadways containing structural planes, deep-mined limestone was selected as the rock material. True triaxial rockburst experiments were conducted on cubic limestone specimens containing a straight-wall arch roadway. A high-speed camera and an acoustic emission system were employed to monitor, in real-time, the initiation and evolution of the rockburst process. In addition, numerical simulations of straight-wall arch roadways containing structural planes with different spacings were carried out using the PFC software, and the failure patterns and rockburst evolution characteristics of surrounding rock with different structural-plane spacings were systematically analyzed. The results indicate that the presence of structural planes significantly alters the stress and energy transmission paths within the rock mass, leading to local stress concentration, enhanced rockburst impact intensity, and more complex microscopic morphologies of the ejected rock fragments. Compared with specimens without structural planes, specimens containing structural planes exhibited higher cumulative acoustic emission ring-down counts and cumulative absolute energy, accompanied by pronounced transient high-amplitude acoustic emission activity. Moreover, the proportion of shear failure in specimens containing structural planes was higher than that in intact specimens without structural planes. With increasing structural-plane spacing, the failure mode of the surrounding rock gradually changed, while the mutual constraint between the rock mass and the structural planes weakened. As the structural-plane spacing increased, the failure pattern of the surrounding rock changed, and the constraining effect of the rock mass on the structural planes gradually weakened. Consequently, crack propagation paths became increasingly oriented toward the free surface, resulting in a progressive decrease in the propagation angle of wing cracks. Based on the experimental data, a theoretical relationship was established between structural-plane spacing and the stress characteristic parameter of the straight-wall arch roadway, σi/σmax. These findings can provide a useful reference for disaster prevention and mitigation, as well as rockburst prediction, in underground openings containing structural planes under impact disturbance.

Mechanical response and failure mechanisms of sandstone under water–rock interaction: a multi-scale study and constitutive modeling

Numerical Study of Failure Mechanism and Effectiveness of Control Measure of Soft Rock Roadways Affected by Humidity Diffusion

Understanding the failure mechanism of soft rock roadways in high-humidity environments, as well as designing appropriate control measures, are critical for ensuring their stability. In this study, swelling and triaxial compression tests on argillaceous sandstone were first performed. Results show that the triaxial compressive strength (TCS), elastic modulus, cohesion, and internal friction angle of argillaceous sandstone are all decreased due to the water weakening effect. Then, a self-developed finite-element-based numerical code was employed to elucidate the role of humidity diffusion in the deformation and failure of soft rock roadways. Simulation results indicate that under the influence of humidity, high stress concentration zones develop, initiating microcracks within these regions. As humidity continues to diffuse, the high stress concentration zones expand and migrate deeper into the surrounding rock, causing microcracks to propagate and accelerating humidity diffusion. This cyclical process repeats, ultimately resulting in macroscopic fracturing. The failure of roadway exhibits a tensile–shear mixed mode during humidity diffusion. A comparative analysis of four control measures reveals that conventional non-waterproof shotcrete primary support is of limited effectiveness in ensuring the stability of high-humidity soft rock roadways. It is essential to promptly establish a closed waterproof support structure. Furthermore, localized support defects significantly impact control effectiveness.

Stability evaluation of rock slope considering the strength failure of weak structural planes induced by blasting vibration