【摘要】：不同圍壓下巖石應變軟化與剪脹特性不同,若在隧洞開挖中考慮圍巖塑性區(qū)域內(nèi)變化圍壓影響,其應力 應變場求解方式將區(qū)別于既有文獻中的傳統(tǒng)方法。根據(jù)圍壓影響下應變軟化圍巖的臨界塑性剪切應變變化特征,給出改進的判斷圍巖是否進入塑性殘余區(qū)域的規(guī)則;引入考慮圍壓與臨界塑性剪切應變的非線性剪脹模型�；贖oek-Brown屈服準則,根據(jù)一定徑向應力增量將圍巖塑性軟化與殘余區(qū)域分層,采用有限差分法對圍巖應力 應變場進行求解;為分析圍壓對圍巖穩(wěn)定性的影響,根據(jù)臨界塑性剪切應變與剪脹系數(shù)變化與否,設定4種非線性力學模型,深入分析并比較4種力學模型下臨界塑性剪切應變、剪脹系數(shù)與圍巖變形等在塑性軟化與殘余區(qū)域的分布規(guī)律。研究結果表明:地質強度指標GSI較小時,考慮圍壓影響下的圍巖應力 應變場與未考慮時差異明顯;此時臨界塑性剪切應變的減小對開挖邊界的圍巖剪脹性具一定抑制作用。
[Abstract]:The characteristics of strain softening and shear expansion of rock under different confining pressures are different. If the influence of variation of confining pressure in the plastic region of surrounding rock is taken into account in tunnel excavation, the stress and strain field solution will be different from the traditional method in the existing literature. According to the variation characteristics of critical plastic shear strain of strain-softening surrounding rock under the influence of confining pressure, an improved rule to judge whether the surrounding rock enters into plastic residual region is given, and a nonlinear shear-expansion model considering confining pressure and critical plastic shear strain is introduced. Based on the Hoek-Brown yield criterion, the plastic softening and residual zone of surrounding rock are stratified by a certain radial stress increment, and the stress and strain field of surrounding rock is solved by finite difference method, in order to analyze the influence of confining pressure on the stability of surrounding rock. According to the change of critical plastic shear strain and shear expansion coefficient, four kinds of nonlinear mechanical models are set up, and the critical plastic shear strain under four kinds of mechanical models is analyzed and compared. Distribution of shear expansion coefficient and surrounding rock deformation in plastic softening and residual region. The results show that the stress and strain field of surrounding rock under the influence of confining pressure is obviously different from that without considering the geological strength index GSI, and the decrease of critical plastic shear strain can restrain the shear dilatancy of surrounding rock at the excavation boundary to some extent.
【作者單位】： 華中科技大學巖土與地下工程研究所;
【基金】：新世紀優(yōu)秀人才支持計劃資助項目(NCET 06 619)
【分類號】：U451.2

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