【作者】 李丹；

【导师】 白世伟；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2008， 博士

【摘要】 模型试验可定性或定量地反映与地下工程有关的天然岩体受力特性,和与其相联系的地下工程结构的相互影响,特别是物理模拟可以比较全面地、真实地模拟复杂地下工程结构、复杂地质构造、复杂地下岩层组合关系,从而在机理研究尚不明朗的情况下避开“描述机理”的尴尬而直接利用物理实体的“内置的”机理“自觉地”生成试验过程和结果,为建立新的理论和数学模型提供依据,并在科学技术的现状下给出工程问题的解决方法或可靠的建议。因此,岩石力学模型试验在科学研究和解决工程实际问题方面具有独特的优势。本文通过对国家自然科学基金重点项目“隧道与地下空间工程结构物的稳定性与可靠性”所依托的示范工程――渝湘高速公路彭武段共和隧道的多个埋深断面的不同地质特征岩体的变形及支护破坏的监测,在遵循相似理论的基础上,最终运用模型试验对均质岩体的二次应力状态及锚杆加固机理、层状岩体的变形及失稳机理、层状岩体锚杆加固机理及其优化原理进行系统的深入研究,并采用开发程序进行相关问题的数值计算对比分析。本文取得了以下研究成果:1.根据共和隧道不同部位的围岩所具有的弹塑性及弹脆性力学特征,排选出环(氧)硅(橡胶)系列、环氧系列、松香系列等三个系列的模拟材料粘结剂,采用重晶石、粉细沙为骨料,对每种粘结剂均形成级差连续的配比,研制出具有弹塑性、线弹脆性、强弹脆性的模型相似材料,并以弹性模量E、抗压强度σc为主要追求的相似参量,确定出符合岩体力学特性的物理模型相似材料。2.在系列模型试验技术的准备方面,针对模型试验的研究目的,系统设计模型试验方案,确定完成物理模型的基本工艺和技术,如应变片槽的基面处理、锚杆的应变量测、平面应变加载条件的保证等。3.针对共和隧道部分泥岩条件下的围岩,采用弹塑性模型相似材料,通过毛洞与锚杆加固工况、短锚杆与长锚杆支护工况的模型试验对比,得到均质围岩下锚杆加固围岩的机理:锚杆区的径向与切向应力均高于毛洞,说明隧道围岩在二次应力的形成过程中,由于锚杆的抵抗作用而产生了局部的应力集中,从而使围岩的应力状态转变为更为稳定的三向压应力状态。4.通过弹脆性模型材料成层布置,并用聚乙烯薄膜部分隔断层间粘结,形成概化的横观各向同性围岩模型.采用相似于反演地应力场的边界应力关系对模型进行加载,从而研究得出缓倾角层状岩体二次应变的分布特征及破坏机理:拱切顶破坏是由于层理内的挤压应力使层理压屈破裂并随后产生离层所致,而边墙围岩则是由于垂直层理的切向挤压而形成的挤出破坏。同时形成了非对称的松动圈。5.在前述项4研究的基础上,针对全长粘结锚杆的设计情况研制出系统锚杆加固下的层状岩体物理模型,特别是解决了锚杆变形状态的应变量测技术,通过相同部位围岩与锚杆的应变对比,形成了层状岩体中锚杆加固围岩的变形特征与机理:在顺层偏压的切顶区域,锚杆径向主要抵抗围岩的径向松弛,发挥径向锚杆的作用;而在边墙围岩中,锚杆切向抵抗围岩的破裂与松动,径向抗拉作用较小,主要发挥剪切锚杆的作用,因而边墙锚杆不可随意减小甚至取消。6.在前述项4、项5研究的基础上,针对项5的破坏特征,将锚杆系统布置改进为薄弱局部的优化加长布置,制作出相应的物理模型,同样通过同部位围岩与锚杆的应变对比,分析出锚杆优化后的应变重分布及破坏特征,并进一步探讨了锚杆优化布置的设计原则:拱切顶区域围岩及锚杆拉应变均有所降低,提高了围岩的承载能力,但也形成了拱脚部位相对薄弱的态势。另外,锚杆的长度优化应与布置区域的幅度优化相结合。7.对模型加载级,以实际地应力的相似荷载为超载系数1.0,则各模型工况的初始破坏超载系数、大破坏超载系数分别为:均质围岩1.38、1.72;层状围岩1.30、1.70;系统锚杆加固的层状围岩1.8、2.6;优化锚杆加固的层状围岩2.4、3.0以上(3.0时未进入大破坏)。层状围岩略低于均质围岩。层状围岩加锚后,一方面提高了同一破坏状态时的超载系数,另一方面也拉大了初始破坏与大破坏状态之间的超载系数差,从而利于工程的安全。更多还原

【Abstract】 Physical model test can qualitatively or quantitatively reflect the mechanics trait of crude rock-mass and interaction among complex engineering structures in underground engineering. Furthermore, it can simulate complex engineering structure, geologic conformation, stratum combination in the underground engineering because the test course and result can come into being automatically due to intrinsic mechanism indwelling in the physical entity by avoiding the embarrassment of expounding mechanism when the research on mechanism is not clear .The test course and result can provide foundation for new theories and mathematics models , gives solutions or reliable suggestions in the case of nowadays scientific and technology standard . So the rock mechanics model test has exclusive advantage for scientific research and settlement of practical engineering.This paper makes a systemic and deep research upon secondary stress state and bolt reinforcement mechanics in isotropic rock mass , upon deformation and failure mechanics of layered rock mass , upon optimizing design for bolt in layered rock mass, according to the simulation theory. All the research origion from the survey and measurement to deformation and support invalidation of GongHe Tunnel’s rock mass with different geological characters and various buried depth . GongHe Tunnel lies in PengWu section of YuXiang Highway ,which is relied as typical sample engineer by the key article of the national natural scientific fund“stability and reliability of engineering construction in tunnel and underground space .The achievement is listed below:1. According to the elastoplastic and elastobrittle mechanical behaviors of the surround rock in different part of GongHe tunnel , 3 series of agglomerants are choosen .They are epoxy series , epory-silicone rubber series , rosin series. Adopting barite and silver sand as skeleton material ,successive various composition of every aggloment is made to form the mechanics character as elastoplastic behavior ,linear elastobrittle behavior and strong elastobrittle behavior of the model material .Finally pick out the composition of model simulation material whose mechanics resembles that of rock mass. Choose the modular E and compressive strengthσc as the main simulating parameters. 2. As prepairation for model test technology ,aiming at the research target we make sure of basic technics and technology about physical model when systemically design the project of test .Such as how to deal with the surface on the bottom of the strain gauge groove , how to get the bolt strain ,how to guarantee the loading mode of planar strain .3. Aiming at shale in part of tunnel ,the reinforcement mechanics of bolt in isotropic rock mass is gained by comparison of model test between excavation and bolt reinforcement case ,short and long bolt reinforcement case with elastoplastic model simulation material .That is that radial and tangent stress in bolt reinforcement case is higher than that in excavation .It illuminates that partial stress concentration appears because the resistance from bolt during the course of secondary stress forms so that the stress state of surround rock alters more stable with three dimentional compressive stress.4. Asynoptic transversely isotropic physical model is formed by layering model material whose interface is partially separated by mylar in order to decrease the friction olong it. Loading the model with simulating practical goestress the research can deduce the contribution trait of secondary stress and failure mechanics of low inclination angel layered rock mass. That is that the failure on the tunnel’s tangent top happens for the sake of that the bedding is pressed to yield duo to the compressive stress within the bedding and then the interface seperates, while the surround rock of sidewall is extruded to failure due to the tangent compressive to the bedding . At the same time asymmetrical fractural rock ring forms.5. Based on the former research (article 4), system bolt reinforcement model with layered rock mass is made according to the practical design of whole-length cohesive bolt. Especially after the bolt measurement technology is solved, we can compare the strain of bolt and surrounding rock at the same position. The deformation trait and bolt reinforcement mechanics in layered rock mass presents that the bolt in tunnel’s top area resists radial relaxation of surrounding rock and takes affect of radial bolt while the bolt resist tangential the fracture and relaxation and mainly takes affect of shear-bolt among the surrounding rock of tunnel’s sidewall .The bolt beyond sidewall cannot be shorten or even be deleted.6. Based on the former research (article 4 and 5), system bolt design is altered to lengthen the bolt in feeble region and corresponding physical model is made. By comparison the strain of bolt and surrounding rock mass in the same point, redistribution of strain and failure trait after bolt optimized is analyzed and the bolt optimized design principle is discussed further. After optimized design in tangent top region the tension stain decrease in some degree so that the capacity of surrounding rock rises while relative feeble position presents in the foot of tunnel. In addition length optimization of bolt should be connected with the range optimization of bolt.7. Now take the load rank which simulates the practical geostress as O. C (overload coefficient) 1.0, then the O. C of initial cracking and the O. C of fracture in various cases correspondingly are: 1.38, 1.72 with isotropic surrounding rock, 1.30, 1.70 with layered surrounding rock, 1.8, 2.6 with system bolt reinforced surrounding rock, 2.4, more than 3.0 (fracture doesn’t present in case of 3.0) with bolt optimized design case. The O. C with layered surrounding rock is less than that with isotropic one. After bolt reinforced to layered surrounding rock the O. C with the same deformation rises as well as the span of O. C between initial cracking and fracture becomes large which benefits for the safety of engineering.更多还原