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THE EFFECTS OF THREE-DIMENSIONAL PENNY-SHAPED CRACKS ON ZONAL DISINTEGRATION OF THE SURROUNDING ROCK MASSES AROUND A deep circular tunnel

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Acta Mechanica Solida Sinica 2015年第6期28卷 722-734页

作者： Xiaoping Zhou Qihu Qian Hanfei Song School of Civil Engineering Chongqing University State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing University Engineering Institute of National Defense Engineering PLA University of Science and Technology State Key Laboratory of Disaster Prevention & Mitigation of Explosion & Impact PLA University of Science and Technology

In this study, it was assumed that three-dimensional penny-shaped cracks existed in deep rock masses. A new non-Euclidean model was established, in which the effects of penny- shaped cracks and axial in-situ stress on zonal disintegration of deep rock masses were taken into account. Based on the non-Euclidean model, the stress intensity factors at tips of the penny- shaped cracks were determined. The strain energy density factor was applied to investigate the occurrence of fractured zones. It was observed from the numerical results that the magnitude and location of fractured zones were sensitive to micro- and macro-mechanical parameters, as well as the value of in-situ stress. The numerical results were in good agreement with the experimental data.

关键词： deep rock masses containing penny-shaped cracks the non-Euclidean model axial in-situ stress fractured zones zonal disintegration phenomenon deep circular tunnel

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Experimental investigation on influence of loading rate on rockburst in deep circular tunnel under true-triaxial stress condition

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Journal of Central South University 2020年第10期27卷 2914-2929页

作者： SI Xue-feng HUANG Lin-qi GONG Feng-qiang LIU Xi-ling LI Xi-bing School of Resources and Safety Engineering Central South UniversityChangsha 410083China School of Civil Engineering Southeast UniversityNanjing 211189China

To investigate the influence of loading rate on rockburst in a circular tunnel under three-dimensional stress conditions,the true-triaxial tests were conducted on 100 mm×100 mm×100 mm cubic sandstone specimens with d50 mm circular perforated holes,and the failure process of hole sidewall was monitored and recorded in real-time by the *** loading rates were 0.02,0.10,and 0.50 MPa/*** test results show that the rockburst process of hole sidewall experienced calm period,pellet ejection period,rock fragment exfoliation period and finally formed the V-shaped *** rockburst has a time lag and vertical stress is high when the rockburst *** vertical stress at the initial failure of the hole sidewall increases with loading *** the same period after initial failure,the rockburst severity of hole sidewalls increased significantly with increasing loading *** the vertical stress is constant and maintains a high stress level,the rockburst of hole sidewall under low loading rate is more serious than that under high loading *** increasing loading rate,the quality of rock fragments produced by the rockburst decreases,and the fractal dimension of rock fragments increases.

关键词： rockburst loading rate deep circular tunnel true-triaxial test V-shaped notch

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Effect of frequency and flexibility ratio on the seismic response of deep tunnels

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Underground Space 2017年第2期2卷 125-133页

作者： Eimar Sandoval Antonio Bobet Lyles School of Civil Engineering Purdue UniversityWest Lafayette 47906United States School of Civil Engineering and GeomaticsUniversidad del ValleCaliColombia

Two-dimensional dynamic numerical analyses have been conducted,using FLAC 7.0,to evaluate the seismic response of underground structures located far from the seismic source,placed in either linear-elastic or nonlinear elastoplastic *** interaction between the ground and deep circular tunnels with a tied interface is *** the simulations,it is assumed that the liner remains in its elastic regime,and plane strain conditions apply to any cross section perpendicular to the tunnel *** elastoplastic constitutive model is implemented in FLAC to simulate the nonlinear *** effect of input frequency and relative stiffness between the liner and the ground,on the seismic response of tunnels,is *** response is studied in terms of distortions normalized with respect to those of the free field,and load demand(axial forces and bending moments)in the *** all cases,*** linear-elastic and nonlinear ground models,the results show negligible effect of the input frequency on the distortions of the cross section,for input frequencies smaller than 5 Hz;that is for ratios between the wave length and the tunnel opening(k=D)larger than ten for linear-elastic and nine for nonlinear *** normalized distortions are obtained for the nonlinear than for the linear-elastic ground,for the same relative stiffness,with differences increasing as the tunnel becomes more flexible,or when the amplitude of the dynamic input shear stress *** has been found that normalized distortions for the nonlinear ground do not follow a unique relationship,as it happens for the linear-elastic ground,but increase as the amplitude of the dynamic input *** loading in the liner decreases as the structure becomes more flexible with respect to the ground,and is smaller for a tunnel placed in a stiffer nonlinear ground than in a softer nonlinear ground,for the same flexibility ratio.

关键词： deep circular tunnel Dynamic numerical analysis Flexibility ratio Distortion Seismic response

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