Development Of Failure Zone Research Articles

Analytical method for elastic-brittle-plastic analysis of a circular tunnel in a non-hydrostatic in-situ stress field considering the unified strength criterion

Based on the unified strength criterion, an analytical solution is proposed to explore the variation law of the impact of tunnel axial stress on the development of failure zone around a circular tunnel. The proposed method aims to deal with the non-axisymmetric problem under a high and complex three-dimensional stress condition. The mechanical behavior of the rock mass is considered to follow an elastic-brittle-plastic model. The conformal transformation is used to deal with the mathematical difficulties caused by the non-circular nature of the boundary. The procedure enables the quantitative representation of the unknown elastoplastic boundary through an undetermined mapping function. The differential-evolution algorithm is used to determine the boundary from the perspective of positive analysis. The presented solution is compared with published analytical solutions. The results show that the solution in this paper covers the first two solutions and is more reasonable than the last one, reflecting the reliability and generality of the new extended method. The parametric study is implemented to discuss the development of failure zone affected by various parameters.

Studies on rock failure of layered rock in underground mining-face and control techniques

The failure of layered rock in underground mining face may be influenced by the slipping among the layers. The shear failure around the excavation circular roadway is the main failure type in layered rock. To Study the rock failure in layered rock, the condition of bedding slipping in rock is analyzed, and the stresses distribution around circular roadway is calculated. Based on the analysis results, the Flac 3D software is used to analyze the failure of layered rock in roadway floor. Discontinuous interfaces are created to study the effect of bedding planes. The failure of floor is described at two phases: roadway stability phase and mining-face recovery influencing phase. The results indicate that a shear failure surface occurs at the side of coal pillar during the first phase; a shear arched plane occurs at the side of mining-face during the second phase. The results of numerical model are in good agreement with monitoring data. Finally, bolts reinforcement design is proposed to eliminate the development of failure zone in layered rock.

Numerical simulation on rockburst of underground opening triggered by dynamic disturbance

The dynamic disturbance, which is termed as the time-dependent loading such as explosion, vibration, stress impact from neighboring rockbursts, earthquakes, may trigger the rockbursts around the underground opening at depth. A numerical model capable of studying the dynamic failure process of rock under coupled static geo-stress and dynamic disturbance is proposed, and it is implemented into the Rock Failure Process Analysis (RFPA), a general finite element package to analyze the damage and failure process of engineering materials such as rock and concrete. Based on the consideration of the static geo-stress, the RFPA-Dynamics is used to simulate the rockburst that is deemed to be triggered by dynamic disturbance around the deep underground opening. The effect of lateral pressure coefficient and dynamic disturbance waveform on the development of failure zone around the underground opening is numerically simulated. The numerical results indicate that the dynamic disturbance is one of the most important mechanisms that trigger the rockbursts around underground opening. Therefore, it is of theoretical and practical significance to investigate the effect of dynamic disturbance on the rockbursts of underground opening, especially for the underground excavation at depth where the surrounding rockmass is highly stressed. The numerical results also reveal that the contribution of the dynamic disturbances is closely pertinent to both the static geo-stress condition and the waveforms of the dynamic disturbance. In general, dynamic disturbance brings about the greater influences on the stability of underground opening with its increasing magnitude and prolonged duration. However, with regard to the specific static geo-stress condition and characteristics of dynamic disturbance, the contribution of dynamic disturbance to trigger the rockbursts must be examined based on numerical analysis according to the specific geo-stress conditions and characteristics of the dynamic disturbance.

Effect of Surface Roughness on the Shear Characteristics of Granular Materials

SYNOPSIS In this paper the effect of surface texture on the shear characteristics of granular materials is studied from the results of drained triaxial compression tests. The materials tested are uniform spheres of steel having different surface roughnesses. Test results indicate that for the granular materials the development of failure zone in the triaxial specimen is affected by surface roughness in the same manner as in Mogami’s test results on one-layer assembly of uniform spheres, and that shearing strength and dilatancy increase correspondingly with an increase in surface roughness. The expression for the physical components of shear strength in granular materials is proposed, and the relationship between surface roughness and “k value” in Mogami’s theory of mechanics of granular materials is also described concerning the test results.