Numerical Analysis of the Effect of Heterogeneity on Underground Roadway Stability under Dynamic Loads

With the increasing depth of coal mining and expanding mining scale, the rocks surrounding deep roadways are in a complex mechanical condition of frequent dynamic disturbance. The heterogeneity has an important influence on rock mass failure under dynamic loads. Therefore, it is necessary to study the deformation and failure of heterogeneous roadway under dynamic load. In this paper, the effect of heterogeneity on stability of roadway under static and different dynamic loads is studied. According to the results, the effect of rock mass heterogeneity on the deformation and failure of surrounding rock varies with different degrees of heterogeneity. Under static loading conditions, the stability of roadway is negatively correlated with the degree of heterogeneity of the rock mass. Under dynamic loading conditions, the change of heterogeneity degree has significant influence on the stability of surrounding rock. With the increase in dynamic load strength, the change in variation difference in the average value of roof sag, stress distribution, and plastic zone caused by variations in heterogeneity will increase. This study contributes to understanding the deformation and failure characteristics of heterogeneous roadways under dynamic loads and can be used to analyze heterogeneous roadways under dynamic loads.

Influence of the Undercut Anchor Head Angle on the Propagation of the Failure Zone of the Rock Medium

The paper presents the results of a numerical analysis (FEM) describing the effect of the undercutting head angle on the formation of the rock mass failure zone during the initial stages of failure propagation. The research was carried out in the context of developing a technology for rock extraction by controlled pull-out of undercut anchors installed in the rock mass. The focus was on the initial stage of crack propagation and its trajectory for anchors embedded at an assumed constant depth and a value of the friction coefficient of the rock against the anchor head. It is shown that smaller angles favor smaller stripping angles and an increased radial impact of the head on the rock material (in the plane perpendicular to the head axis), while the impact of heads with larger angles is found to favor larger fracture penetration angles and faster penetration towards the free rock surface.

Study on Deep Seated Gravitational Slope Deformation in the Slate Belt of the Backbone Range, Central Taiwan

<p>In the mountain area, Deep seated gravitational slope deformation (DSGSD) is a phenomenon that causes rock mass deformation under long-term gravity. In the Slate Belt of the Backbone Range where mainly slate distributed, it is more susceptible to develop DSGSD. After Typhoon Morakot, the high-resolution LiDAR digital terrain data of the entire island of Taiwan could be applied to visual interpretation with the potential landslide area. In this study, we used existing high-resolution LiDAR data and the latest computerized 3D environments to conduct and explore preliminary geological information at the regional scale and potential large-scale landslide distribution with detailed topographical characteristics. Through field investigations and UAV application in Lusan area of central Taiwan, the features caused by regional tectonic effects or DSGSD could be clarified and discussed possible mechanism of rock mass failure caused by these DSGSD. The results help to understand the deformation mechanism of the slate area in the Central Range of Taiwan. In the future, we could further explore the possible causes of why DSGSD transform into catastrophic landslides.</p>

INVESTIGATION OF THE GEOMECHANICAL STATE OF SOFT ADJOINING ROCKS UNDER PROTECTIVE CONSTRUCTIONS

The conditions of coal seam mining in the mines of Ukraine have been considered. The problem of conducting coal mining by longwalls in the conditions of soft adjoining rocks, which concerns the protection of mine roadways located near the face, has been revealed. In such conditions, the existing protective constructions are ineffective due to the fact that they yield and get pressed into the soft rocks of the footwall. This indicated the need for research into the geomechanical state of soft rocks of the footwall. According to the results of known studies on the mechanism of rock mass failure around roadways and the data of physical and mechanical properties of the coal mass, which is represented by soft rocks, the correlation dependence has been obtained, the use of which allowed for the determination of the parameters of the rock deformation diagram and the establishment of the stability criterion of footwall rocks under the protection means and stability conditions of the geotechnical system “protective construction – adjoining rocks.” They are the basis of a new approach to ensure the stability of the roadways, which are supported behind the faces, by controlling the stress state in the system “protective construction – adjoining rocks.” This may be the basis for the development of new methods of protecting roadways in conditions of soft adjoining rocks.

Quantifying Discrete Seismic Responses to Mining

Applying analysis techniques developed for naturally occurring earthquakes to mine seismicity is common practice, however, these methodologies rarely consider the influence of blasting on the dynamic rock mass failure processes observed in mines. Due to the complex nature of bulk orebody extraction at depth, quantifying discrete seismic responses to mining can be challenging. This paper identifies seismic responses to mining by pairing single-link clustering with finite temporal windows bound by mine blasting practices. A methodology is presented to quantify the space-time characteristics of these responses using four Seismic Response Parameters (SRP’s): Distance to Blast, Distance to Centroid, Time After Blast and Time Between Events. Using SRP’s, seismic responses to mining can be quantitatively classified as induced, complex or triggered (with respect to discrete mine blasting). Because these response parameters do not require an extensive and/or triaxial dense sensor array, they are applicable to a variety of underground mining operations. In this work, SRP’s are applied to 189 discrete seismic responses occurring over two months of active mining, and a two week shutdown period, at Agnico Eagle’s LaRonde Mine.