Shitan Gu

Bio: Shitan Gu is an academic researcher from Shandong University of Science and Technology. The author has contributed to research in topics: Coal mining & Coal. The author has an hindex of 4, co-authored 7 publications receiving 101 citations.

Strainburst process of marble in tunnel-excavation-induced stress path considering intermediate principal stress

Abstract: Strainburst is one type of rockburst that generally occurs in deep tunnel. In this study, the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition, and two stress paths were designed, a commonly used stress path in true triaxial unloading rockburst tests and a new test path in which the intermediate principal stress was varied. During the tests, a high-speed camera was used to record the strainburst process, and an acoustic emission (AE) monitoring system was used to monitor the AE characteristics of failure. In these two stress paths, all the marble specimens exhibited strainbursts; however, when the intermediate principal stress was varied, the rockburst became more violent. The obtained results indicate that the intermediate principal stress has a significant effect on rockburst behavior of marble. Under a higher intermediate principal stress before the unloading, more elastic strain energy was accumulated in the specimen, and the cumulative AE energy was higher in the rockburst-induced failure, i.e., more elastic strain energy was released during the failure. Therefore, more violent failure was observed: more rock fragments with a higher mass and larger size were ejected outward.

Failure Mechanism Analysis and Support Design for Deep Composite Soft Rock Roadway: A Case Study of the Yangcheng Coal Mine in China

Abstract: This paper presented a case study of the failure mechanisms and support design for deep composite soft rock roadway in the Yangcheng Coal Mine of China Many experiments and field tests were performed to reveal the failure mechanisms of the roadway It was found that the surrounding rock of the roadway was HJS complex soft rock that was characterized by poor rock quality, widespread development of joint fissures, and an unstable creep property The major horizontal stress, which was almost perpendicular to the roadway, was 159 times larger than the vertical stress The weak surrounding rock and high tectonic stress were the main internal causes of roadway instabilities, and the inadequate support was the external cause Based on the failure mechanism, a new support design was proposed that consisted of bolting, cable, metal mesh, shotcrete, and grouting A field experiment using the new design was performed in a roadway section approximately 100 m long Detailed deformation monitoring was conducted in the experimental roadway sections and sections of the previous roadway The monitoring results showed that deformations of the roadway with the new support design were reduced by 85–90% compared with those of the old design This successful case provides an important reference for similar soft rock roadway projects

A Control Method of Rock Burst for Dynamic Roadway Floor in Deep Mining Mine

Abstract: Roadway floor rock burst is an important manifestation of rock bursts in deeply buried mines. With the increase of mining depth and mining intensity, rock burst disasters in the roadway floor such as floor heaves are becoming more serious. The article investigated the roadway floor severe heave caused by floor rock burst during excavation of the No. 3401 working face, which was controlled by an anticlinal structure and deep mining in Shandong Mine, China. Firstly, by analyzing geological conditions of the working face, roadway support parameters, and characteristics of coal and rock, it was revealed that high tectonic stress and high crustal stress were main causes of the floor rock burst. Secondly, based on the Theory of Mechanics and Theory of Energy, the energy conversion process in the roadway floor was discussed, and the rock burst condition caused by elastic energy in the roadway floor was analyzed. The failure characteristics of roadway-surrounding rock were also inspected, using a borehole recorder. The roof and sidewalls of roadway mainly contained fissures and cracks, whereas cracks and broken areas are distributed in the roadway floor. Finally, based on the deformation and failure characteristics of roadway-surrounding rock, a method termed “overbreaking-bolting and grouting-backfill” was proposed to control roadway floor rock burst. The method was tested in the field, and the results showed that it could effectively control the deformation of roadway floor and rock burst, guaranteeing the stability of roadway floor. This impact control method for the roadway floor can provide a reference for the prevention and control of roadway rock burst in mines with similar geological conditions.

Bending Moment Characteristics of Hard Roof before First Breaking of Roof Beam Considering Coal Seam Hardening

Abstract: The mechanical properties of a coal seam affect the distribution of support pressure. Considering the strain hardening effect of coal seam, the support pressure relationship of three zones—softened, hardened, and elastic—of a coal seam with regard to a hard roof is proposed, and methods to determine an approximate expression for the support pressure of hardened zone of coal seam, the range of hardened zone, and the corresponding peak values of support pressure are provided. The deflection equations of a hard roof under three different support pressure relationships of coal seam before the first breaking were theoretically derived, and all the relevant integration constants were determined. Numerical examples of two cases are provided for calculating the bending moment of a hard roof and the support pressure of a coal seam. The analysis shows that as the working face advances, the maximum support pressure increases, the residual strength of coal seam at coal wall decreases, the overall deflection of roof gradually increases, the maximum bending moment of roof in the front of coal wall increases, and the advanced distance of roof bending moment peak gradually increases. As the depth of softened zone of coal seam increases, the similar conclusion is obtained, and the advanced distance of the roof bending moment peak increases at a relatively fast speed. Because the bending moment peak of hard roof is located near the support pressure peak in the softened zone of coal seam, the depth of softened zone of coal seam significantly affects the advanced distance of the bending moment peak of a roof. The actual advanced fracture distances of hard roof are distributed in a relatively broad range. The results indicate that there is a “large and long” type advanced fracture distance occurring in the actual stope. With the same overlying load and stope parameter conditions, the maximum support pressures of support roof in softened, hardened, and elastic zones considering a hardened coal seam are smaller than those in softened and elastic zones without hardening. However, the plumpness in front of the peak of the former support pressure curve is superior to that of the latter, and both the bending moment peak value and the advanced distance of bending moment peak of the former are higher than those of the latter.

Strength of materials ..

Abstract: (Vol. 1, part of 2 vols set) Size: 22x14cm., Contents: Chapter I. Tension and Compression within the Elastic Limit II. Analysis of Stress and Strain III. Bending Moment and Shearing Force IV. Stresses in Laterally Loaded Symmetrical beams V. Deflection of Laterally Loaded Symmetrical Beams VI. Statically Indeterminate Problems in Bending VII. Symmetrical Beams of Variable Cross Section-Beams of Two Materials VIII. Bending of Beams in a plane which is not a Plane of Symmetry IX. Combined Bending and Axial Load Theory of Columns X. Torsion and Combined Bending and Torsion XI. Strain Energy and Impact XII. Curved Bars Appendix A: Moments of Inertia of Plane Areas Appendix B. Tables of Structural Shapes Author Index Subject Index. ISBN:8123910304 xiv+442 Yr. of Pub.reprint 2004Paper Back

Ground Response of a Gob-side Entry in a Longwall Panel Extracting 17 m-Thick Coal Seam: A Case Study

Abstract: This study presents a comprehensive field investigation of the ground response of a gateroad subjected to high stress induced by extracting a 17 m-thick coal seam. The test site is located at Datong City, Shanxi Province, China. The measurement results of the entry convergence and fracture development indicated that the gateroad with a 30 m-wide coal pillar maintained a good performance during the development period but suffered a strong response, including roof sag, floor heave, support unit failure and internal fractures sharply developed during the current panel-retreating period. During panel retreating, the impact range of the mining disturbance was about 110 m ahead of the active panel, and the mining disturbance accelerated dramatically at 50–60 m ahead of the mining panel. The results of the borehole stress measurement showed that the maximum stress induced in the virgin coal pillar and the coal pillar reached 15.3 MPa and 23.9 MPa, which are about 1.5 and 2.3 times the initial ground stress, respectively. This high stress contributed significantly to the instability of the gateroad. The average stress within the coal pillar was greater than that in the virgin coal pillar, and a high-stress zone was found at the coal pillar depth of 11–20 m. This stress distribution characteristics implies that the 30 m-wide coal pillar has a relatively sufficient bearing capacity to withstand the majority of mining-induced loads and that the coal pillar size could be reduced from 30 to 15–20 m wide to decrease the range of high stress in the coal pillar. Furthermore, taking into consideration of intense mining disturbance and abundant time interval for gateroad development as well as a high-strength support scheme, a small-width coal pillar of 8 m was recommended and tentatively applied in the field. The field application demonstrated that the newly designed pillar size and support pattern could ensure gateroad stability at some level. The study finding can help to better understand the stability control of entry driven along gob-side and its correlation with coal pillar size as well as the mining disturbance in specially thick coal seam (ETCS). In addition, the design principle and support strategy for the coal pillar in ETCS presented in this study can potentially be applied to other similar projects.

Strainburst process of marble in tunnel-excavation-induced stress path considering intermediate principal stress

Abstract: Strainburst is one type of rockburst that generally occurs in deep tunnel. In this study, the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition, and two stress paths were designed, a commonly used stress path in true triaxial unloading rockburst tests and a new test path in which the intermediate principal stress was varied. During the tests, a high-speed camera was used to record the strainburst process, and an acoustic emission (AE) monitoring system was used to monitor the AE characteristics of failure. In these two stress paths, all the marble specimens exhibited strainbursts; however, when the intermediate principal stress was varied, the rockburst became more violent. The obtained results indicate that the intermediate principal stress has a significant effect on rockburst behavior of marble. Under a higher intermediate principal stress before the unloading, more elastic strain energy was accumulated in the specimen, and the cumulative AE energy was higher in the rockburst-induced failure, i.e., more elastic strain energy was released during the failure. Therefore, more violent failure was observed: more rock fragments with a higher mass and larger size were ejected outward.