本文選題：巖土體災(zāi)變 + 多尺度方法　； 參考：《浙江大學(xué)》2014年博士論文

【摘要】：土體由大量土顆粒構(gòu)成,其災(zāi)變過程是由微觀顆粒、細觀材料到宏觀場地多尺度級聯(lián)耦合漸進演化的結(jié)果。傳統(tǒng)土力學(xué)基于連續(xù)介質(zhì)假定,不能反映巖土體災(zāi)變破壞過程中顆粒間接觸脫開、顆粒劇烈轉(zhuǎn)動和顆粒破碎等微觀尺度行為,多尺度數(shù)值模擬是再現(xiàn)巖土體災(zāi)變過程的有效手段。論文針對兩種典型災(zāi)變破壞現(xiàn)象,即應(yīng)變局部化災(zāi)變破壞和非應(yīng)變局部化災(zāi)變破壞,開展多尺度數(shù)值模擬方法研究,取得如下研究成果： (1)針對應(yīng)變局部化巖土體災(zāi)變問題,將剪切帶等局部化帶的弱非連續(xù)變形等效為無厚度的強非連續(xù)變形帶,采用黏聚區(qū)域模型刻畫剪切帶的變形特性和能量耗散機制,基于增強有限單元法構(gòu)造出無厚度剪切帶單元,提出了基于黏聚區(qū)域模型的增強有限元分析方法。邊坡漸進失穩(wěn)破壞過程的分析表明,基于黏聚區(qū)域模型的增強有限元分析方法能夠很好地再現(xiàn)剪切帶的擴展過程,不存在網(wǎng)格敏感性等問題；剪切帶的應(yīng)變軟化特性對滑裂面形狀的影響不大,但極大地降低了邊坡的極限承載能力。 (2)針對非應(yīng)變局部化災(zāi)變問題,采用基于位移／速度協(xié)調(diào)和基于力協(xié)調(diào)的兩種界面耦合方法實現(xiàn)有限元與離散元的多尺度耦合。算例表明,基于位移／速度協(xié)調(diào)的界面耦合方法不可避免地引起耦合系統(tǒng)的模糊反射；基于力協(xié)調(diào)的界面耦合方法允許離散元顆粒與有限元單元邊界的接觸分離,能夠有效地再現(xiàn)離散元模型和有限元模型的接觸作用及動量和能量交換過程。 (3)基于給定不同的加權(quán)函數(shù)分別引入不同尺度模型的截斷邊界和耦合區(qū)域,通過耦合區(qū)域內(nèi)位移／速度、力協(xié)調(diào)條件,提出有限元與離散元耦合的廣義橋域法。根據(jù)加權(quán)函數(shù)的不同取法,廣義橋域法可以退化得到傳統(tǒng)的橋域法和邊-邊界面耦合方法：適當(dāng)選取加權(quán)函數(shù)可實現(xiàn)有限元-離散元耦合和離散元-有限元耦合區(qū)域分離,得到協(xié)調(diào)條件相互獨立的分離區(qū)域耦合方法和分離界面耦合方法。本文還構(gòu)造了有限元單時步對離散元多時步的時間積分算法。數(shù)值算例表明,分離區(qū)域耦合方法和分離界面耦合方法能夠有效地避免模糊反射。橋域法和邊-邊耦合方法通過將高頻波轉(zhuǎn)化為低頻波實現(xiàn)能量守恒；而分離區(qū)域耦合方法和分離界面耦合方法則將有限元模型不能描述的高頻部分截斷,耦合系統(tǒng)存在能量損失,隨有限單元的細劃和高頻響應(yīng)分量的減少而降低。有限元單時步對離散元多時步時間積分算法極大地提高了計算效率。 (4)在離散元開源軟件Yade中實現(xiàn)了有限元與離散元的廣義橋域耦合,編制了巖土體災(zāi)變過程的多尺度數(shù)值分析平臺。多尺度模型的模擬結(jié)果與離散元模型的模擬結(jié)果相當(dāng),但計算效率有了很大的提高。 (5)采用廣義橋域法模擬靜力觸探過程,再現(xiàn)了探頭附近土顆粒流動現(xiàn)象,揭示了不同錐尖角度、不同深度時錐尖土體的破壞機理。分析結(jié)果表明,比貫入阻力和錐尖阻力大小隨錐尖角度、重力場及刺入速度增大而增加,而側(cè)壁摩阻力主要受重力場和刺入速度影響,與錐尖角度幾乎無關(guān)。
[Abstract]:Based on the assumption of continuum media , the multi - scale numerical simulation is an effective means to reconstruct the catastrophe process of rock and soil .

( 1 ) According to the problem of strain localization , the weak non - continuous deformation equivalent of shear band is equivalent to the non - continuous deformation zone with no thickness , and the deformation characteristic and energy dissipation mechanism of shear band are characterized by using the finite element method . The reinforcement finite element analysis method based on the reinforcement finite element method is presented . The analysis of the failure process of the slope progressive instability analysis shows that the enhanced finite element analysis method based on the viscoelastic region model can better reproduce the expansion process of the shear band without the problems of grid sensitivity and the like .
The strain softening characteristics of the shear band have little influence on the shape of the sliding surface , but the ultimate bearing capacity of the slope is greatly reduced .

( 2 ) The multi - scale coupling of finite element and discrete element is realized by using two kinds of interface coupling methods based on displacement / velocity coordination and force coordination for non - strain localized catastrophic problems . The example shows that the interface coupling method based on displacement / velocity coordination inevitably causes the fuzzy reflection of the coupling system ;
The interface coupling method based on force coordination allows the contact separation between the discrete element particles and the finite element unit boundary to effectively reproduce the contact effect and the momentum and energy exchange process of the discrete element model and the finite element model .

( 3 ) The generalized bridge domain method of finite element and discrete element coupling is proposed based on a given different weighting function . The generalized bridge domain method of finite element and discrete element coupling is proposed based on the displacement / velocity and force coordination conditions in the coupling region .
The separation area coupling method and the separation interface coupling method can cut off the high frequency part which cannot be described by the finite element model , and the coupling system has energy loss , and decreases with the reduction of the fine and high frequency response components of the finite element .

( 4 ) The generalized bridge domain coupling of finite element and discrete element is realized in the discrete element open source software Yade , and the multi - scale numerical analysis platform of rock - soil body catastrophe process is compiled . The simulation results of the multi - scale model are equivalent to the simulation results of the discrete element model , but the calculation efficiency is greatly improved .

( 5 ) Using the generalized bridge domain method to simulate the static sounding process , the phenomenon of soil particle flow near the probe is reproduced , and the damage mechanism of the cone - tip soil at different cone - tip angles and different depths is revealed . The results show that the resistance of the cone - tip increases with increasing the angle of the cone , the gravity field and the penetration velocity , and the friction resistance of the side wall is mainly influenced by the gravity field and the penetration velocity , which is almost independent of the cone - tip angle .
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TU43

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