發(fā)布時(shí)間：2018-04-20 17:23

  本文選題：巖土體 + 孔隙水壓力�。� 參考：《武漢大學(xué)》2016年博士論文

【摘要】：目前,大規(guī)模資源開采、水利工程施工、二氧化碳的地下封存及高放射物的地質(zhì)處置,都涉及到地下水和深部巖體的相互作用。深部地層中的巖土體在地下水變化時(shí),孔隙水和裂隙水的滲透過(guò)程直接影響地層中的應(yīng)力分布。在外部擾動(dòng)荷載作用下,飽和巖土體易產(chǎn)生超孔隙水壓力,將對(duì)巖土工程的安全與穩(wěn)定造成極大的隱患。水力耦合問題一直是巖土工程中的重要課題,然而,僅從單一的宏觀尺度來(lái)認(rèn)識(shí)這一問題已經(jīng)不能滿足我國(guó)工程實(shí)踐和基礎(chǔ)科學(xué)研究的需求。本文從細(xì)觀孔隙尺度上研究了顆粒形狀的表征方法,定義了形狀參數(shù)并詳細(xì)闡述了形狀參數(shù)-球度,及其與巖石的宏觀力學(xué)特性的關(guān)系。針對(duì)顆粒離散元中的粘結(jié)接觸模型,提出了考慮膠結(jié)厚度的孔隙度算法。改進(jìn)了顆粒流程序中的流體耦合算法并進(jìn)行了流體注入誘導(dǎo)的裂紋擴(kuò)展研究。然后提出了顆粒-流體耦合的計(jì)算模型,解決了顆粒流程序中現(xiàn)有流體算法所面臨的問。并采用該算法模擬了飽和土的三軸排水和不排水剪切試驗(yàn)。本文的主要研究成果如下：(1)定義了描述顆粒形狀的形狀參數(shù)-球度,球度定義為與顆粒等體積的球體表面積和顆粒表面積之間的比值。球度描述了一個(gè)顆粒和球體的接近程度,能夠反映顆粒之間的咬合作用的強(qiáng)弱。通過(guò)生成四種代表顆粒研究了顆粒形狀和巖石宏觀力學(xué)特性的關(guān)系。結(jié)果表明礦物顆粒的形狀影響巖石的啟裂強(qiáng)度、損傷強(qiáng)度和峰值強(qiáng)度。具體來(lái)說(shuō),隨著球度增大,特征強(qiáng)度指標(biāo)均降低。隨著顆粒球度的增大,試樣的彈模降低,泊松比會(huì)增大。顆粒球度降低時(shí),顆粒之間的咬合作用增強(qiáng),試樣的內(nèi)摩擦角和粘聚力都呈增大趨勢(shì)。(2)在顆粒流程序中的流體算法-固定網(wǎng)格法的基礎(chǔ)上加入力學(xué)伺服模塊,模擬了三軸滲流耦合試驗(yàn),研究了全應(yīng)力應(yīng)變過(guò)程中滲透特性的變化規(guī)律。考慮到離散元模擬中孔隙度和真實(shí)試樣的巨大差異,提出了考慮膠結(jié)厚度的孔隙度計(jì)算方法。計(jì)算結(jié)果表明所提算法能夠反映真實(shí)孔隙度。同時(shí),所提算法考慮裂紋擴(kuò)展過(guò)程中接觸粘結(jié)失效的問題,建立了孔隙度和裂紋數(shù)目之間的關(guān)系,并利用Kozeny-Carman方程推推導(dǎo)了滲透率的變化規(guī)律。結(jié)果表明采用新的孔隙度算法得出的全應(yīng)力應(yīng)變過(guò)程中滲透率變化曲線與其他學(xué)者在試驗(yàn)中得出的滲透率曲線一致。(3)對(duì)顆粒流程序中的流體耦合算法進(jìn)行了改進(jìn),加入了流體流動(dòng)對(duì)于顆粒的剪切力,并在計(jì)算中考慮了流體網(wǎng)絡(luò)由于顆粒位移造成的網(wǎng)格體積的變化。采用雙注水孔試樣研究了流體注入誘導(dǎo)的裂紋擴(kuò)展過(guò)程,闡述了注水孔間距對(duì)于裂紋生長(zhǎng)模式、定向以及裂隙拓?fù)浣Y(jié)構(gòu)的影響。通過(guò)Dijkstra算法預(yù)測(cè)了兩個(gè)注水孔之間的流體最短路徑。計(jì)算結(jié)果表明,當(dāng)注水孔間距較近時(shí),微裂紋相互作用較強(qiáng),微裂紋數(shù)目較多,裂隙網(wǎng)絡(luò)連通性較差,從兩個(gè)注水孔啟裂的裂紋趨向于直接聚合；當(dāng)注水孔間距較大時(shí),裂隙網(wǎng)絡(luò)連通性較好,微裂紋數(shù)目較少。裂紋方向基本上與壓力力鏈垂直,在裂紋擴(kuò)展尖端區(qū)域,張力力鏈較為集中。(4)基于前人的研究,提出了一種新的顆粒-流體耦合離散元計(jì)算模型,詳細(xì)推導(dǎo)了超孔隙水壓力的計(jì)算方法,闡述了水壓力的作用機(jī)制。在模型中考慮了應(yīng)變誘導(dǎo)的孔隙水壓力及孔隙體積的變化,并對(duì)測(cè)量球的大小進(jìn)行了優(yōu)化,提高了計(jì)算效率。(5)在顆粒流平臺(tái)下分三個(gè)模塊實(shí)現(xiàn)了所提出的顆粒-流體耦合模型。通過(guò)北京黏質(zhì)粉土的三軸不排水試驗(yàn)數(shù)據(jù)校準(zhǔn)了顆粒的細(xì)觀參數(shù)。將耦合模型計(jì)算得到偏應(yīng)力曲線和孔隙水壓力曲線與試驗(yàn)和常體積法的計(jì)算結(jié)果進(jìn)行比較,發(fā)現(xiàn)耦合方法得到結(jié)果與試驗(yàn)及常體積法均一致。采用校準(zhǔn)之后的細(xì)觀參數(shù),模擬了不同圍壓下飽和土的排水和不排水三軸壓縮試驗(yàn)。結(jié)果表明,隨著圍壓的升高,偏應(yīng)力升高。在不排水條件下,應(yīng)力比隨著圍壓升高而降低,孔隙水壓力隨著圍壓升高而增大。
[Abstract]:At present, large-scale resource exploitation, water conservancy project construction, underground sealing of carbon dioxide and geological disposal of high radioactive materials all involve the interaction of groundwater and deep rock mass. In deep stratum, the infiltration process of pore water and fissure water directly affects the stress distribution in the stratum when the groundwater changes. Under the load, the saturated rock and soil can easily produce super pore water pressure, which will cause great hidden danger to the safety and stability of geotechnical engineering. The hydraulic coupling problem has always been an important subject in geotechnical engineering. However, it is impossible to meet the needs of the engineering practice and basic scientific research in our country only from a single macro scale. This paper studies the characterization of the shape of the particle from the meso pore size, defines the shape parameters and expounds the shape parameter sphericity, and its relation to the macroscopic mechanical properties of the rock. In view of the bond contact model in the particle discrete element, the aperture degree algorithm considering the cementation thickness is proposed. The fluid in the particle flow program is improved. The coupling algorithm is used to study the crack propagation induced by fluid injection. Then the calculation model of the particle fluid coupling is proposed to solve the problem of the existing fluid algorithm in the particle flow program. The three axis drainage and undrained shear test of the saturated soil is simulated with this algorithm. The main research results of this paper are as follows: (1) definition The degree of sphericity describing the shape parameter of the particle shape is defined as the ratio between the surface area of the sphere and the surface area of the particles. The sphericity describes the proximity of a particle and the sphere, which can reflect the strength of the occlusion between the particles. By generating four kinds of representative particles, the particle shape and macroscopic mechanics of the rocks are studied. The result shows that the shape of mineral particles affects the opening strength, the strength and the peak strength of the rock. In particular, with the increase of the sphericity, the index of the characteristic strength decreases. With the increase of the sphericity, the modulus of the specimen is reduced and the Poisson's ratio will increase. When the particle sphericity is reduced, the bite effect between particles is enhanced and the sample is enhanced. The internal friction angle and cohesive force are all increasing. (2) on the basis of the fluid algorithm fixed grid method in the particle flow program, the mechanical servo module is added, the three axis seepage coupling test is simulated, and the change law of the permeability characteristic in the full stress and strain process is studied. The great difference between the porosity and the true specimen in the discrete element simulation is taken into account. The porosity calculation method considering the thickness of cementation is proposed. The calculation results show that the proposed algorithm can reflect the true porosity. At the same time, the proposed algorithm takes into account the problem of contact failure in the process of crack propagation, establishes the relationship between the number of porosity and the number of cracks, and deduces the change law of permeability by using the Kozeny-Carman equation. The results show that the permeability change curve obtained by the new porosity algorithm is in accordance with the permeability curve obtained by other scholars in the experiment. (3) the fluid coupling algorithm in the particle flow program is improved, the fluid flow is added to the shear force of the particles, and the fluid network is considered in the calculation. The change of the mesh volume caused by the displacement of the particle is studied. The process of crack propagation induced by fluid injection is studied by the double injection hole specimen. The effect of the distance between the water injection hole on the mode of crack growth, the orientation and the topological structure of the crack is expounded. The shortest path between two water injection holes is predicted by the method of Dijkstra. The calculation results show that When the spacing of water injection holes is near, the interaction of micro cracks is stronger, the number of micro cracks is more, the connectivity of fracture network is poor, the crack initiation from two water injection holes tends to direct polymerization. When the spacing of water injection holes is large, the connectivity of the fracture network is better and the number of micro cracks is less. The crack direction is basically perpendicular to the pressure chain, and the crack propagation is extended. In the tip area, the tension chain is more concentrated. (4) based on the previous research, a new calculation model of particle fluid coupling discrete element is put forward. The calculation method of super pore water pressure is derived in detail, and the mechanism of water pressure is expounded. In the model, the changes of pore water pressure and pore volume induced by strain are taken into account, and the measurement ball is also measured. The size is optimized and the calculation efficiency is improved. (5) the proposed particle fluid coupling model is realized by three modules under the particle flow platform. The fine parameters of the particles are calibrated through the three axis undrained test data of the Beijing clay silt. The coupling model is calculated to get the partial stress curve and the pore water pressure curve and the test and constant. The results of the volume method are compared. It is found that the results of the coupling method are in agreement with the test and the normal volume method. The three axial compression tests of the drainage and undrained soil under different confining pressure are simulated with the calibrated parameters. The results show that the stress ratio increases with the rise of the confining pressure. Under the condition of undrained, the stress ratio is with the surrounding. The pore water pressure increases with the increase of confining pressure.

【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TU43

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