【摘要】：原生裂隙的起裂、擴(kuò)展和貫通演化特征和破壞規(guī)律是研究巖體工程破壞和失穩(wěn)的基礎(chǔ),滲流對巖體強(qiáng)度的影響也受工程界所重視。由于三維裂隙巖體研究的復(fù)雜性,前人研究往往將三維問題簡化為二維問題,而在這一簡化往往不能全面反映三維裂隙的擴(kuò)展破壞規(guī)律。近年來,研究裂隙的三維擴(kuò)展形態(tài)和破壞機(jī)制成為裂隙巖體領(lǐng)域的重要課題,對裂隙巖體三維應(yīng)力條件下的破裂過程和機(jī)理研究仍需深入。此外,很多巖體工程的失穩(wěn)往往和地下水的作用密切相關(guān)。因此,開展裂隙巖體在內(nèi)含有壓水的條件下其破裂規(guī)律的變化和新的特征也是十分重要的。本文通過實(shí)驗(yàn)研究、理論分析和數(shù)值模擬等方法,研究類巖石材料含裂隙試件的裂紋擴(kuò)展規(guī)律和機(jī)理,采用細(xì)觀理論方法,揭示裂紋的擴(kuò)展過程和破壞形態(tài),對有水壓條件的裂隙試件破裂過程和強(qiáng)度規(guī)律進(jìn)行了分析,并將分析方法用于工程實(shí)際中,主要完成和開展了以下幾方面工作： (1)研制了低溫下拉壓比為1/6.6的樹脂材料用于制作模型試件,該材料脆性高,符合巖石的基本特征,其力學(xué)參數(shù)大理巖等巖石力學(xué)參數(shù)接近,可以在很大程度上模擬這些巖石的力學(xué)特性；而且其透明度高,能夠清晰的用肉眼觀察試件內(nèi)部裂紋的擴(kuò)展破壞狀態(tài),便于人們直觀上理解裂紋的擴(kuò)展規(guī)律。同時(shí),作者用該材料研制了含中空裂隙試件,進(jìn)行了內(nèi)置裂隙在有水壓的條件下的壓縮試驗(yàn)。采用該中空裂隙試件及作者設(shè)計(jì)的試驗(yàn)方法,可以對內(nèi)置裂隙試件施加不同的水壓和側(cè)壓,開展多種工況下含預(yù)置裂隙試件的壓縮試驗(yàn)和水壓致裂試驗(yàn)。 (2)通過透明預(yù)置裂隙試件單軸壓縮試驗(yàn),研究了三維內(nèi)置裂隙試件的新生裂紋的起裂、擴(kuò)展和貫通破壞規(guī)律。研究表明,三維試件受壓破裂過程大致經(jīng)歷四個(gè)階段。其四個(gè)變形階段與巖石試件完全相對應(yīng),并發(fā)現(xiàn)材料有非常明顯的與巖石類似的擴(kuò)容特性。試驗(yàn)過程中除了觀測到常見的包裹狀翼型裂紋,還出現(xiàn)了前人理論推測出的花瓣形裂紋。 不飽和樹脂材料制作的試件為均質(zhì)材料試件,除預(yù)置裂隙外,不存在其他缺陷,因此可認(rèn)為該均質(zhì)材料試件壓縮試驗(yàn)為無其他缺陷干擾的情況下此單一缺陷(預(yù)置裂隙)產(chǎn)生破壞的過程。同非均質(zhì)材料試驗(yàn)比較,在裂隙新生裂紋萌生和擴(kuò)展初期兩種材料擴(kuò)展方式相同,但由于受非均質(zhì)缺陷的影響,最終破壞形式有所不同。 (3)進(jìn)行了有水壓條件下裂隙試件的壓縮試驗(yàn)。根據(jù)試驗(yàn)結(jié)果,有水壓作用下與無水壓條件下裂隙試塊的破壞過程和現(xiàn)象有相同和不同之處為：試驗(yàn)過程中均在橢圓狀裂隙長軸端部產(chǎn)生包裹狀翼型裂紋,但有水壓作用下未出現(xiàn)花瓣?duì)盍鸭y；有水壓條件下,新生裂紋的萌生和試塊達(dá)到完全劈裂狀態(tài)時(shí)所需的壓力更小,即在水壓作用下,試塊的承壓能力降低,而且水壓越大,新生裂紋的萌生和和試件破壞所需的軸向壓力越小。 (4)使用FLAC3D計(jì)算程序,通過二次開發(fā),采用彈脆性損傷模型模擬了單裂隙和雙裂隙試塊在單軸加載條件下裂紋擴(kuò)展過程和破壞情況,計(jì)算結(jié)果與試驗(yàn)過程基本吻合。通過計(jì)算不同側(cè)壓工況下裂隙試件的破壞過程,隨著圍壓的增加,新生裂紋的萌生應(yīng)力、擴(kuò)容點(diǎn)和峰值強(qiáng)度都隨之增加,而且裂紋的擴(kuò)展形態(tài)有所不同。 (5)采用流固耦合方法研究了不同水壓作用下裂紋的起裂和擴(kuò)展規(guī)律。水壓的增加使得新生裂紋萌生的壓力和峰值強(qiáng)度均有所降低,而且二者隨著水壓的增加而下降。水壓致裂試驗(yàn)?zāi)M計(jì)算表明,水壓致裂的最終破壞裂紋始終垂直于最小主應(yīng)力；如果垂直主應(yīng)力小于水平主應(yīng)力,則破壞方式為水平方向,如果垂直主應(yīng)力大于水平主應(yīng)力,則破壞方式為垂直方向。 (6)以大型地下洞室開挖為例,進(jìn)行了準(zhǔn)三維模型的洞室開挖數(shù)值模擬,計(jì)算結(jié)果基本能夠反應(yīng)洞室開挖圍巖應(yīng)力場、位移場的變化規(guī)律,特別是由于采用了模型細(xì)觀計(jì)算方法,基本能夠反應(yīng)洞周原生裂隙的擴(kuò)展規(guī)律和滲流對洞室開挖的影響。
[Abstract]:The characteristics of initiation, propagation and penetration evolution and failure law of primary fractures are the basis for studying the failure and instability of rock mass engineering, and the influence of seepage on rock mass strength is also paid attention by engineering circles. In recent years, it has become an important subject in the field of fractured rock mass to study the three-dimensional propagation form and failure mechanism of cracks. The research on the fracture process and mechanism of fractured rock mass under three-dimensional stress condition still needs to be further carried out. In addition, the instability of many rock mass engineering is often closely related to the action of groundwater. It is also very important to study the change of fracture law and new characteristics of fractured rock mass with pressurized water. In this paper, by means of experimental research, theoretical analysis and numerical simulation, the law and mechanism of crack propagation of rock-like materials with cracks are studied, and the crack propagation process and failure are revealed by means of microscopic theory. In this paper, the fracture process and strength law of fractured specimens with hydraulic pressure are analyzed, and the analysis method is applied to engineering practice. The following work is mainly completed and carried out:
(1) A resin material with a tensile-compressive ratio of 1/6.6 at low temperature was developed for making model specimens. The material has high brittleness and accords with the basic characteristics of rock. Its mechanical parameters, such as marble, are close to each other, which can simulate the mechanical properties of these rocks to a great extent; moreover, it has high transparency and can be clearly observed by naked eyes. At the same time, a specimen with a hollow crack is developed by the author, and the compression test of a built-in crack is carried out under the condition of water pressure. Water pressure and lateral pressure are used to carry out compression tests and hydraulic fracturing tests of preset fractured specimens under various conditions.
(2) Through uniaxial compression test of transparent pre-cracked specimens, the law of initiation, propagation and penetration failure of new cracks in three-dimensional specimens with internal cracks is studied. In addition to the common wrapped airfoil cracks, petal-shaped cracks were also observed during the test.
The specimen made of unsaturated resin material is homogeneous material, and there are no other defects except pre-cracks. Therefore, it can be considered that the compression test of the homogeneous material specimen is the failure process of the single defect (pre-crack) without interference of other defects. In the early stage of development, the two materials have the same propagation mode, but due to the influence of heterogeneous defects, the ultimate failure mode is different.
(3) Compression tests of fractured specimens under hydrostatic pressure are carried out. According to the test results, the failure process and phenomena of fractured specimens under hydrostatic pressure are the same and different as those under non-hydrostatic pressure: wrapped airfoil cracks occur at the end of the long axis of elliptical cracks, but no petal cracks appear under hydrostatic pressure. Under the condition of water pressure, the pressure required for the initiation of new cracks and the complete splitting of the specimen is smaller, that is, the bearing capacity of the specimen decreases under the action of water pressure, and the larger the water pressure, the smaller the axial pressure required for the initiation of new cracks and the failure of the specimen.
(4) By using FLAC3D program and secondary development, the crack propagation and failure of single crack and double crack specimens under uniaxial loading are simulated by using the elastic-brittle damage model. The calculated results are in good agreement with the experimental results. The initiation stress, dilatancy point and peak strength of the crack increase, and the crack propagation morphology is different.
(5) The initiation and propagation of cracks under different hydraulic pressures are studied by fluid-solid coupling method. The pressure and peak strength of the initiation of new cracks decrease with the increase of hydraulic pressure. The simulation results of hydraulic fracturing test show that the ultimate failure crack is perpendicular to the maximum. If the vertical principal stress is less than the horizontal principal stress, the failure mode is horizontal, and if the vertical principal stress is greater than the horizontal principal stress, the failure mode is vertical.
(6) Taking the excavation of a large underground cavern as an example, the quasi-three-dimensional numerical simulation of the excavation of the cavern is carried out. The calculated results can basically reflect the stress field and the displacement field of the surrounding rock of the cavern excavation. Especially, the micro-calculation method of the model can basically reflect the propagation law of the primary cracks around the cavern and the excavation of the cavern by seepage. Influence.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TU452

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