本文選題：應(yīng)變局部化　切入點(diǎn)：側(cè)向變形　出處：《中國(guó)礦業(yè)大學(xué)》2015年碩士論文

【摘要】：本文通過(guò)室內(nèi)單軸壓縮試驗(yàn)和電阻應(yīng)變監(jiān)測(cè)的方法,以側(cè)向變形作為主要的觀測(cè)值,探究巖石應(yīng)變局部化現(xiàn)象的啟動(dòng)、特征與巖石變形破壞特征的關(guān)系;運(yùn)用數(shù)值模擬方法,基于應(yīng)變軟化本構(gòu)關(guān)系,考慮巖石峰后強(qiáng)度參數(shù)變化、圍壓和初始缺陷因素,結(jié)合巖石破壞特征和剪切帶形態(tài),探究巖石全應(yīng)力應(yīng)變過(guò)程中應(yīng)變局部化現(xiàn)象,得到如下結(jié)論:1)本文試驗(yàn)所得應(yīng)變局部化啟動(dòng)時(shí)的應(yīng)力σB與峰值應(yīng)力σd的比值σB/σd分別為0.42、0.44、0.58,試驗(yàn)得出的巖石應(yīng)變局部化啟動(dòng)大致在巖石裂紋穩(wěn)定擴(kuò)展階段的中后期即開(kāi)始發(fā)生,在裂紋加速擴(kuò)展階段已經(jīng)表現(xiàn)的比較明顯;單軸壓縮試驗(yàn)得到的三種巖石破壞形態(tài)對(duì)應(yīng)特定的應(yīng)變局部化過(guò)程。2)峰后抗剪強(qiáng)度參數(shù)的不同變化模式對(duì)巖樣的應(yīng)力應(yīng)變關(guān)系有較明顯影響,對(duì)平均側(cè)向應(yīng)變特征影響較小。而考慮峰后抗剪強(qiáng)度參數(shù)的不同變化模式時(shí),得出的巖樣不同位置的側(cè)向應(yīng)變有明顯的差異,巖樣最終變形形態(tài)各異,應(yīng)變局部化現(xiàn)象也有不同的表現(xiàn)。當(dāng)巖樣內(nèi)為“X型”的剪切帶和近垂直剪切帶時(shí),應(yīng)變局部化現(xiàn)象相比剪切帶集中局部區(qū)域表現(xiàn)的不明顯,應(yīng)變局部化現(xiàn)象表現(xiàn)的顯著與否和剪切帶形態(tài)密切相關(guān)。3)圍壓不同時(shí),應(yīng)變局部化現(xiàn)象差異較大。巖性條件一致時(shí),中低圍壓下,巖樣應(yīng)變局部化現(xiàn)象比較明顯,隨著圍壓的增大,巖樣不同位置側(cè)向應(yīng)變的差異逐漸減小,應(yīng)變局部化現(xiàn)象逐漸表現(xiàn)的不顯著,巖樣的變形逐漸趨于各部分整體協(xié)同變形。4)巖樣存在初始缺陷時(shí),對(duì)變形、強(qiáng)度和剪切帶形態(tài)有比較大的影響。試驗(yàn)的5個(gè)缺陷位置得到的剪切帶分為單斜剪切面和“V型”楔體剪切帶,剪切帶均發(fā)育于缺陷位置。巖樣剪切帶傾角和長(zhǎng)度最大時(shí),其峰值強(qiáng)度最大,而殘余強(qiáng)度則最小,應(yīng)變會(huì)集中于剪切帶附近,應(yīng)變局部化現(xiàn)象比較明顯。5)運(yùn)用FLAC3D軟件分別以Mohr-Coulomb模型和考慮峰后強(qiáng)度衰減的應(yīng)變軟化模型為本構(gòu)模型進(jìn)行數(shù)值模擬分析,使用應(yīng)變軟化模型巖體在峰值后表現(xiàn)出更加明顯的變形現(xiàn)象,卸壓區(qū)范圍更大,支承壓力區(qū)壓力減小,覆巖剪應(yīng)力集中區(qū)范圍更大,從而使得開(kāi)挖造成的破壞范圍變大,可見(jiàn)忽略巖石峰后強(qiáng)度衰減即應(yīng)變軟化現(xiàn)象而進(jìn)行的數(shù)值分析對(duì)工程來(lái)說(shuō)是偏于危險(xiǎn)的。
[Abstract]:In this paper, by means of laboratory uniaxial compression test and resistance strain monitoring, lateral deformation is taken as the main observed value to explore the relationship between the start-up of rock strain localization phenomenon and the characteristics of rock deformation and failure, and the numerical simulation method is used. Based on the constitutive relation of strain softening, considering the change of strength parameters, confining pressure and initial defect factors of rock after peak, combined with the characteristics of rock failure and the shape of shear zone, this paper explores the strain localization phenomenon in the process of full stress and strain of rock. The results are as follows: (1) the ratio of stress 蟽 B to peak stress 蟽 d at the start of strain localization in this paper is 0.422 / 0.44 0. 58, respectively. The rock strain localization starts at the middle and late stage of the stable growth stage of rock crack. At the stage of accelerated crack propagation, it is obvious. The three rock failure patterns obtained by uniaxial compression test correspond to the specific strain localization process. 2) different variation models of shear strength parameters after peak have obvious influence on the stress-strain relationship of rock samples. However, considering different variation models of shear strength parameters after peak, the lateral strain of rock samples at different locations is obviously different, and the final deformation of rock samples is different. The phenomenon of strain localization is also different. When the shear zone is "X-type" and near vertical shear zone, the strain localization phenomenon is not obvious compared with the concentrated local area of shear zone. Whether the strain localization is significant or not is closely related to the shear zone shape. 3) the strain localization is different from that of the shear zone. When the lithology condition is the same, the strain localization of rock sample is obvious under the middle and low confining pressure. With the increase of confining pressure, the difference of lateral strain in different position of rock sample decreases gradually, the strain localization phenomenon is not obvious gradually, the deformation of rock sample gradually tends to the total synergistic deformation of each part. 4) when there are initial defects in rock sample, the deformation of rock sample, The shear bands obtained from the five defect locations are divided into monocline shear plane and V-shaped wedge shear zone. The shear bands are all developed in the defect position. When the slope and length of the rock sample shear zone are the largest, The peak strength is the largest, while the residual strength is the smallest, and the strain is concentrated near the shear band. The strain localization phenomenon is obvious. 5) using FLAC3D software, the Mohr-Coulomb model and the strain softening model considering the post-peak strength attenuation are respectively used as the constitutive model to carry out the numerical simulation and analysis. The strain softening model shows a more obvious deformation phenomenon after the peak value. The range of the relief zone is larger, the pressure of the supporting pressure area is reduced, and the range of the shear stress concentration zone of the overburden rock is larger, which makes the damage range of the excavation become larger. It can be seen that the numerical analysis is dangerous to engineering by neglecting the strength attenuation of rock after peak, that is, strain softening.
【學(xué)位授予單位】：中國(guó)礦業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TU45

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