基于峰后特征的深部隧道圍巖分層斷裂數(shù)值分析

蘇永華　毛克明　梁斌　付雄　賀煒

摘要：為了揭示深部隧道工程圍巖的分層斷裂機(jī)理而展開數(shù)值實(shí)驗(yàn)研究.分析了深部地層巖體歷史及賦存環(huán)境，認(rèn)為深部巖體在力學(xué)上處于峰后階段，根據(jù)巖石峰后應(yīng)力應(yīng)變特征選定了圍巖的峰后特征指標(biāo)及其開挖響應(yīng)方程.建立了數(shù)值實(shí)驗(yàn)?zāi)Ｐ?，設(shè)計(jì)了開挖數(shù)值模擬的圍巖響應(yīng)監(jiān)控方案.完成了大量的開挖數(shù)值模擬，實(shí)現(xiàn)了深部圍巖分層斷裂現(xiàn)象在數(shù)值模擬中的重現(xiàn).基于實(shí)驗(yàn)中圍巖應(yīng)力、變形分布的全程監(jiān)測結(jié)果，在確定圍巖分層斷裂產(chǎn)生條件的基礎(chǔ)上，進(jìn)一步研究得到了圍巖分層斷裂層數(shù)、分層斷裂圈半徑、最大峰值應(yīng)力等參數(shù)與峰后特征指標(biāo)的關(guān)系.根據(jù)地下結(jié)構(gòu)開挖圍巖應(yīng)力重分布及巖石力學(xué)破裂機(jī)理，分析了分層斷裂中次生自由面、多重似開挖面形成的力學(xué)機(jī)制.所得數(shù)值模擬結(jié)果，為深部工程圍巖的分層斷裂提供了驗(yàn)證依據(jù)，消解了長期以來數(shù)值模擬中沒有觀察到分層斷裂現(xiàn)象的困惑.

關(guān)鍵詞：深部隧道；分層斷裂；應(yīng)變軟化；峰后脆性；力學(xué)機(jī)制

中圖分類號(hào)：TU458 文獻(xiàn)標(biāo)識(shí)碼：A

Abstract：Numerical simulation research has been conducted in order to reveal the mechanism of the layered fracture within surrounding rock in deepburied tunnel. Analysis of the history of the rock mass and its environment suggests that the mechanism of the deep rock mass was located in the postpeak stage， the postpeak characteristic indexes and the excavation response equations were selected based on the postpeak stressstrain characters of rock mass. A numerical model was established， a monitoring scheme of surrounding rock response was designed which was caused by excavation， and a fair amount of excavation was completed by numerical simulation method， and the phenomenon of layered fracture within surrounding rock was reproduced in the numerical simulation. According to the monitoring results about the rock stress and deformation distribution from the experiment， and based on the critical conditions under which the layered fracture in surrounding rock was emerged， the relationship of the fracture layer number of surrounding rock， the radius of layered fracture zone and the maximum peak stress with the postpeak characteristic indexes were studied. Based on the surrounding rock stress redistribution related to the excavation of underground structure and the fracture mechanism of rock mechanics， this paper analyzed the mechanical mechanism of the formation of secondary freesurface and multiple excavation surface. The numerical results provide the basis for the layered fracture in deep surrounding rock， and the confusion about the unobserved phenomena of layered fracture in numerical simulation is also eliminated.

Key words：deepburied tunnel； layered fracture； strainsoftening； peakbrittleness of rock； mechanicalmechanism

由于煤炭、石油、國防以及核廢料處理等領(lǐng)域向地層深部或超深部挺進(jìn)，深部巖體的開挖變形問題已引起了巖土工程界的廣泛重視.傳統(tǒng)的觀測和理論公認(rèn)，地下工程開挖后僅在靠近臨空面圍巖形成單一破裂帶.但在深部工程開挖及相關(guān)試驗(yàn)中，發(fā)現(xiàn)圍巖表現(xiàn)出不同于淺部工程的破裂區(qū)域分布，即非經(jīng)典破裂現(xiàn)象.

俄羅斯學(xué)者E.I.shemyakin等＼[1＼]通過模型試驗(yàn)獲得了分區(qū)破裂化現(xiàn)象，并在深部開采中得到電阻率法測試結(jié)果的證實(shí).李術(shù)才等＼[2＼]通過臨界值定義，在淮南礦區(qū)丁集煤礦深部巷道圍巖中通過鉆孔電視成像儀觀察到了分區(qū)破裂化.周小平等＼[3＼]運(yùn)用彈性力學(xué)和斷裂力學(xué)理論，研究了破裂區(qū)和非破裂區(qū)的寬度和數(shù)量問題.李英杰等＼[4＼]探討了圍巖分區(qū)破裂機(jī)理，認(rèn)為它是劈裂破壞現(xiàn)象.李樹忱等＼[5＼]通過對(duì)圍巖或數(shù)值單元的破壞進(jìn)行重新定義或改造后，利用FLAC3D的模擬獲得圍巖的分區(qū)破裂圖像，并簡要討論了不同因素的影響程度.蘇永華＼[6＼]等研究了原巖應(yīng)力場對(duì)分層斷裂的影響.