【作者】 王建良；

【导师】 徐则民；

【作者基本信息】 昆明理工大学 ， 工程力学， 2013， 博士

【摘要】 21世纪是地下工程向深部发展的世纪,深埋隧洞、核废料储存、深部地热开发都涉及到深埋岩体力学问题。20世纪80年代开始,加拿大、瑞典、日本、瑞士、美国等国都建立了地下实验室,对硬岩高应力破坏的监测技术、理论研究和相关数值分析方面取得了辉煌的成绩,其中以加拿大URL对Lac du Bonnet花岗岩的研究最为卓著。目前对于深埋大理岩力学特性的研究可参照加拿大URL花岗岩的研究思路,主要集中于4个方面：(1)强度特征除了传统的峰值强度和残余强度外,人们还提出了描述裂纹状态的启裂强度和损伤强度。对于小尺度岩块的各种强度阈值可采用试验手段获得；大体积岩体的强度阈值只有通过数值方法获得,近年来基于PFC的SRM(综合岩体模型)对此问题富有成效。(2)开挖损伤区域(EDZ)深埋隧洞开挖后由于应力调整、爆破扰动、温度湿度变化等因素会导致开挖面附近形成开挖损伤区域,了解开挖损伤区域的范围、损伤程度和演化特征对评价围岩稳定、渗透扩散规律和支护措施具有重要意义。(3)革新的试验技术研究目前真三轴试验机越来越普及,但硬岩的试验还要求真三轴加压时能同时监测压缩过程中的声发射、波速变化、渗透率变化,或对不同温度环境的模拟,还应能实现对海量试验数据的高速连续采集。(4)大型原位试验设计和实施室内试验针对小尺度的岩块力学特性开展研究,如果要将相关认识拓展至大尺度岩体还需要设计并开展针对性原位试验。本文主要工作致力于深埋大理岩力学特性的室内试验研究和描述方法研究。前者包括大理岩试样各损伤阈值的测定和峰后力学特性的试验研究,通过与花岗岩试验成果的对比,丰富了目前硬岩的研究成果；后者探讨大理岩力学特性的PFC方法描述,即用PFC描述了隧洞的开挖损伤特征、岩体强度特征和大理岩峰后特征,拓展了PFC方法在硬岩强度特征与开挖损伤区域描述方面的应用。在前述研究成果基础上,利用PFC标定特定岩体质量的开挖损伤深度和形态获得了岩体级别的颗粒细观参数,预测了埋深更大洞段的围岩损伤深度,与常用的连续方法相比,基于PFC的围岩损伤深度预测具有较高的精度,对支护设计具有重要价值。由于锦屏大理岩随围压变化所具有的脆-延-塑性转换特征,决定了它不会出现软岩里常见的大变形破坏,也不全是纯脆性的破坏,因而破损深度不会太深。在围岩破损的预测过程中包含了隧洞掘进方法的影响和围岩应力调整的影响,因此所预测的破损深度基本趋于围岩所处应力环境下的最大破损程度,本文应用PFC2D预测的Ⅲ类围岩破损深度,对支护深度的确定具有较好的指导意义。本文主要工作及创新点：(1)完成10组深埋大理岩试验的单轴压缩室内试验,通过应力-应变曲线确定大理岩的启裂强度、损伤强度和峰值强度；(2)完成12组深埋大理岩的常规三轴压缩试验,确定大理岩的峰值强度、残余强度。并通过试验揭示出大理岩的随围压增高所展示出来的脆-延转换特征,在较高的围压水平下,大理岩展现出理想塑性的力学响应；(3)采用基于Hoek-Brown强度的本构模型对锦屏Ⅱ类围岩进行了损伤深度预测,该模型能够统一描述大理岩在不同围压水平下的脆-延-塑性转换特征：(4)采用PFC方法从细观层面对大理岩的脆-延转换特征进行了描述,研究了基于Bond Particle Model模型的细观参数取值规律；(5)在合理描述大理岩脆-延转换的基础上,发展了基于PFC数值方法的模拟手段对深埋大理岩隧洞的围岩开挖损伤区域进行了直接的描述；(6)根据研究得到的PFC模拟围岩开挖损伤区域的数值方法,对锦屏引水隧洞不同埋深洞段的围岩开挖损伤深度进行预测,并将预测结果与现场实测结果进行了对比；(7)结合目前深埋地下工程在室内实验、现场试验、理论研究、数值分析方法等方面的进展,展望了后续研究工作。(8)发展了运用PFC方法模拟室内直剪试验来反演模型细观参数的方法。更多还原

【Abstract】 With the development of the deep underground engineering in21th century, almost all deeply buried tunnels, nuclear wastes as well as exploitation of deep geoheat involve the deep rock mass mechanics. Since1980s, many underground research laboratories have been established in America, Canada, Sweden, Japan, Switzerland, and achieved much significant results in monitoring techniques, theoretical research and correlatable numerical analyses on hard rocks under high crustal stress. Among them, it was very impressive for the study of lac du bonnet granite in Canada by URL.The methods of research on deeply buried marble can refer to the previous route of the granit byURL, which could include four aspects as follows:1) Strength feature. Besides traditional peak strength and residual strength, researchers have proposed a crack initiation strength and a damage strength in order to characterize the state of cracks. In general, the threshold value of majority strength of microscale intact rocks can be acquired by tests, while the threshold values for macroscale rock mass can only be obtained using numerical simulation. Recently, it is very efficient to solve the macroscale rock mass in terms of the PFC-based SRM.2) Excavation damage zone (EDZ). Due to the stress redistribution, disturbance of blasting and changes of temperature and humidity, a EDZ will form after excavation in the deeply buried tunnel face. It is very important to evaluate stability, percolation and diffusion mechanics and support measures of surrounding rocks by understanding the region, degree and evolution of EDZ.3) Reformed experimental technique. Although the true triaxial testing machine is now popular in many laboratories, the test of hard rocks has more requirements including simultaneously monitoring the acoustic emission in compression, changes of wave velocity, and permeability, or simulating at varied temperature and quickly recording seadata from tests.4) Large-scale in-situ test design and implement.The room experiments only solve the mechanic investigation of small-scale block rocks,instead for macroscale rock mass, it is necessary to design and carry out the in-situ test.In this work, room testing and description methods of mechanics to deeply buried marble are studied. The former covers the test of varied damage thresholds and post failure behaviors of marble samples. The results are compared to that in the case of granite, which enrich the research achievement of the hard rocks. The latter explores the description of PFC methods in mechanic behaviors of marble, namely describing the features of excavation damage, rock mass strength and post failures by means of PFC. This study broadens the application of PFC in strength and damage fields of hard rocks. Compared with traditional continuum methods, PFC has higher accuracy in prediction of damage thickness to hard rocks, showing a vast importance to support design.Due to a specific shift characteristics of brittleness-ductility plasticity with the confining pressure for marble in Jinping, it determines that large-scale deformation behaviors can not occur in the same way in common soft rocks, also it is not the pure brittle failures. Thus the thickness of breakage might not be deep. The breakage thickness of surrounding rock predicted by PFC includes the influence of excavation and stress redistribution and is close to the maximum extent. The resultant may provide a guiding significance for support design.Main work and points of innovation:(1)10groups of room single-axial compression tests of deeply buried marble are accomplished, and the crack initiation strength, damage strength and peak strength of marble are determined according to stress-strain curves.(2)12groups of normal tri-axial tests of deeply buried marble are completed, and the peak strength and residual strength are detected. These reveal a brittleness-ductility shift characteristic for marble with increasing confining pressure, and a idea plasticity response under higher confining pressures.(3) Cundall’s BDP (Brittle-Ductile-Plastic model) can be used to describe the shift of brittleness-ductile-plastic under varied confining pressures, and the breakage depth of Jinpin III level marble mass is predicted.(4) Features of the shift between brittleness-ductile-plastic of Marble are described by PFC method, and the micro-parameters is studied based on the Bond Particle Mode.(5) On the base of reasonable description of the shift between brittleness and ductile for marble, a numerical simulation based on PFC is developed to directly analyze the excavation breakage zone of surrounding marble mass.(6) According to the obtained method of predicting breakage zone, seven groups of surrounding marble samples from water tunnel with various depth in Jinping are calculated. The results indicate that the calculated value is in agreement with the measured value.(7) A perspective to the future work is made through analyzing the current progress in room tests, field tests, theoretical investingation and numerical simulation.更多还原