【作者】 张宁；

【导师】 赵阳升；

【作者基本信息】 太原理工大学 ， 采矿工程， 2013， 博士

【摘要】 能源问题是世界各国十分关注的热点问题,是关系到国家安全的重大战略问题。高温岩体地热是19世纪70年代才提出并开始试验开发的,在美、日、英、法等国得到了较好的发展,被认为是几乎用之不竭的绿色的能源。高温岩体地热能主要蕴藏在花岗岩类岩体中,围绕着高温岩体地热开采一系列工程与技术难题,急需揭示高温三维应力条件下花岗岩体的蠕变、渗流、热破裂等一系列基本规律,为设计与制订高温岩体地热开采的技术方案提供指导,综合已有的各类成果,以中国西藏羊八井地热深部高温岩体地热开采为例,研究经济高效的开采方案,对中国和世界高温岩体地热开采无疑具有重要意义。采用中国矿业大学的“20MN高温高压岩体三轴试验机”,对ΦD200mm×400mm大尺寸花岗岩试件在高温下的蠕变特征进行了试验研究,温度高达600℃,轴向应力最高达175MPa。围压最高达175MPa。本文详细介绍了三维应力作用下,花岗岩在高温条件下的蠕变试验方法和结果,结合理论与试验结果分析,发现了花岗岩在300℃时轴压94MPa围压75MPa时花岗岩经历蠕变的第一阶段和第二阶段,蠕变变形逐渐停滞,呈现明显的稳态蠕变的特征；在400℃,轴压125MPa围压100MPa时,呈现明显的非稳态蠕变特征。试验还揭示了花岗岩的蠕变性随温度和应力的升高而增强,蠕变性态转变的温度门槛值在300℃到400℃之间。通过对实验数据的分析,发现高温三维应力条件下平均主应力引发鲁灰花岗岩发生蠕变变形,提出了考虑平均主应力应力作用时稳态蠕变率的本构方程,得到了鲁灰花岗岩蠕变本构方程的参数A.、A2、△Q、m、n。研究还发现静水应力下的蠕变和差应力下的蠕变曲线特征相同,同样可以划分为初始蠕变阶段,稳态蠕变阶段和加速蠕变阶段三个阶段,在300-400℃之间存在一个门槛值,当温度达到这个门槛值后,在静水应力作用下,鲁灰花岗岩蠕变曲线的初始蠕变阶段消失。鲁灰花岗岩的蠕变变形是温度,差应力和平均主应力应力的函数,温度、差应力和平均主应力应力的升高都会加速鲁灰花岗岩的蠕变变形。研究发现：(1)三维应力条件下鲁灰花岗岩300℃,500℃的轴向蠕变和300℃,500℃,600℃的体积蠕变变形均可划分为：瞬态蠕变阶段、稳态蠕变阶段和加速蠕变阶段。(2)高温三维应力条件下,鲁灰花岗岩试样的体积、长度和半径随蠕变时间的增加出现增长,这是因为热破裂引起岩石的内部产生了大量的微裂纹,同时还发现试样的侧向比轴向变形增长的速度快。(3)以试验结果为依据将平均主应力应力引发体积蠕变,差应力引发轴向蠕变作为三维应力状态下黏弹塑性问题的假设,导出三维应力条件下Burgers体模型体积蠕变的本构方程。(4)通过对蠕变曲线的分析发现,可以用Burgers体模型来模拟鲁灰花岗岩300℃,500℃的轴向蠕变和300℃,500℃,600℃的体积蠕变,并且求出模型的参数。在花岗岩蠕变——渗流实验的同时,还实时测试花岗岩样在热破裂作用下的渗流规律,实验揭示了：(1)在三维应力的条件下,花岗岩发生了热破裂。在热破裂升温过程中,花岗岩样的渗透率随温度的升高而表现为正指数增大的规律。(2)在热破裂作用的初期,花岗岩样渗透率随温度的增加而缓慢增加。在热破裂作用的后期,花岗岩样渗透率随温度的升高而急剧升高直至达到渗透率峰值。(3)在整个热破裂升温的过程中,各花岗岩样的渗透率随温度的升高而不断增加,渗透率变化率随温度的升高而不断加速。(4)在静水应力和热破裂作用下,花岗岩样渗透率峰值和初始值的比值最高可达93倍,渗透率的变化率最高达3.5×10-07d/℃,热破裂作用极大地增强了花岗岩的渗透特性。上述实验同时,还采用美国物理声学公司24通道声发射仪对蠕变实验期间的声发射数据进行了采集。实验得到了高温三维应力条件下,岩样在蠕变变形期间的声发射规律如下：在瞬态蠕变变形阶段此时声发射信号较强,随时间的延长声发射信号强度稍稍减弱。在岩样的稳态蠕变变形阶段,岩样的变形以粘塑性变形为主,声发射信号进入平静期。在稳态蠕变变形阶段的后期,岩样内部重新开始产生裂纹,声发射信号各参数越来越强。在岩样的加速蠕变变形阶段,声发射各参数的强度越来越大并最终达到峰值。在高温三维应力条件下,岩样声发射的能量事件比、事件计数率、振铃计数率、振幅计数率和能量计数率各参数之间具有较好的相似性。详细研究了中国西藏羊八井地区的高温岩体地热田形成的大陆动力学环境,念青唐古拉山南坡、当雄羊八井盆地的构造特征、地应力大小与方向,5-15km深部的高温熔融岩体结构、高温岩体热盆的温度场分布和热能资源量。羊八井高温岩体地热田可开发的高温岩体地热资源量达5.4×108万千瓦／年,是中国巨大的潜在的绿色能源。研究提出了利用高温熔融区附近的断层剪切滑移带作为人工储留层,沿断层倾斜方向的低处布置垂直注水井与高出布置倾斜生产井的羊八井高温岩体地热开采方案。深入分析了考虑地层应力作用的热流交换区：的渗流场特征、人工储留层特征,进行了工程实施与投资概算分析,该人工储留层的围岩体积量3×1011m3,是英国Cornwall高温岩体地热开采试验工程采用水压致裂建造的人工储留层体积量的360倍。由一口注水井和两口生产井组成的一套高温岩体地热开采系统,可建造一座1000万千瓦的电站,发电100年以上,具有极好的经济与社会效益。更多还原

【Abstract】 Energy is the world’s hot issues related to national security, is the important strategic problem. Geothemal of Hot Dry rock is put forward in the1970s to the development and testing, in America, Japan, Britain, France and other countries has been a good development, considered almost inexhaustible green energy. geothermal of HDR appear. the granitoids are in rock mass, around a series of engineering and technology exploiting geothermal heat, need reveals3D granite rock stress condition of creep, seepage, and thermal cracking and so on, a series of basic rule for design and make geothermal mining technique scheme provides guidance, integrated with the existing results of China’s Tibet occurred in the deep geothermal heat rock geothermal mining, for example, the study of economic efficiency mining scheme of China and the world, high rock geothermal mining of great significance.By making use of the20MN servo-controlled triaxial rock testing machine with high temperature and high pressure of china university of mining and technology, we have carried out experimental study on creep property of large size granite specimens of Φ200mm×400mm under high temperature with temperature up to600℃and axial and lateral stress up to175MPa.. This article describes creep test methods and results of granite under a three-dimensional stress and high temperature. Combining theory with analysis of test results, we discover granite experiences the first and second phases of creep at300℃, axial stress of94MPa and lateral stress of75MPa.At the same time the creep deformation of granite shows clearly the characteristics of the steady-state creep and gradually stops. But at400℃, axial stress of94MPa and lateral stress of75MPa the deformation shows obvious characteristics of the non-steady-state creep. The research reveals Creep property of granite increased with the increasing of temperature and stress. There is an threshold of temperature about transition from steady-state creep at300℃to the non-steady-state creep at400℃Through analysis of experimental data,the paper discovered that hydrostatic stress can cause creep formulation of lu gray granite and we proposed constitutive equation of stable-state creep rate taking into consideration for hydrostatic stress and acquiered creep constitutive equation parameters of lu gray granite A1、 A2、△Q、m、n. We also discoverer that the creep property caused by hydrostatic strss is the same as those cased by differential stress in lu gray granite. It also can be divided into three stages transient creep, stable-state creep and accelerating creep. There is a temperature threshold value between300℃and400℃. The primary creep deformation disappeared under hydrostatic stress and temperature threshold value in lu gray granite. The creep formulation of lu gray granite is a function of temperature, differential stress and hydrostatic stress. All the higher temperature, differential stress and hydrostatic strss can accerlerate creep formulation of lu gray granite.(1) under three dimensional stress, axial creep deformation at300℃and500℃and volumetric creep deformation at300℃,500℃and600℃of lu gray granite shows three stages:primary creep stage, stable-state creep stage and accelerating creep stage.(2) Under high temperature and3-d stress, volume、length and radius of lu gray granite increased with the creep time because of fissure caused by thermal cracking in rock. We also discovered lateral deformation is more rapid than axial deformation at the same time.(3) It’s the basical hypothesis of viscosity-elastic-plastic problem under three dimensional stress that differential stress causes axial creep, hydrostatic stress causes volumetric creep deformation at the basis of experimental data and we proposed volumetric creep constitutive equation of Burgers model under three dimensional stress.(4) Through the analysis of creep curve, it’s proper to simulate axial creep at300℃and500℃and volumetric creep at300℃,500℃and600℃with Burgers model and calculate model parameters.This research reveals:(1) under three dimensional stress, there is thermal cracking phenomenon about all granites. We discover the seepage law of intact granite rock sample that permeability is exponential growth function of temperature through the process of thermal cracking.(2) The permeability of granite has a slow growth through initial stage of TCA, a rapid growth through late stage of TCA and up to permeability climax in the final with the temperature rising up.(3) The permeability and its rate of granite have a continuous growth through whole stage of TCA with increasing temperature.(4)The ratio of permeability climax value to initial value is up to93and permeability rate is up to3.5x10-07d/℃.TCA has a important role in enhancing permeability of granite.We adopted acoustic emission apparatus made by American Physical Acoustics Corporation to collect data during creep experimental period. We acquired acoustic emission law of rock sample creep deformation experiment under high temperature and3D stress. Among transient creep stage, acoustic emission signal is very strong and decreases with time. Among stable creep stage, rock sample is mainly dominated viscoplastic deformation and acoustic emission signal goes into quiet period. Because of heterogeneity of granite, stress concentrated on force skeleton formed by hard mineral with stress adjustment and redistribution. At the late stable creep stage, the inner of rock sample resumed fracturing. All parameters of acoustic emission signal become increasing. Among accelerating creep stage, All parameters of acoustic emission signal also become increasing and finally reached peak value. Because rock mass is general composed of various minerals and contains joints and fracture discontinuous structure surface, it is inevitable heterogeneous. It is heterogeneity that causes above acoustic emission phenomenon. Under high temperature and3D stress, it still needs more experiment to research whether there are the same acoustic emission phenomenon about homogeneous or close to homogeneous rock sample. Under high temperature and3-d stress, there are good similarity among all acoustic emission parameters event counts rate, ringdown counts rate, energy counts rate, amplitude counts rate and energy-event’s ratio.This paper analyzed that HDR geothermal field of Tibet formed continental dynamics environment, South slope of Tanggula Mountain, DangXiong Yangbajing basin the tectonic characteristics, in-site stress size and orientation,8-18km deep rock mass structure of melt rock mass, temperature field distribution and heat resources. the research and put forward to mining scheme of HDR geothermal, seepage analysis of the heat exchange area, artificial reservoir features, project implementation and investment analysis.Proposed sliding zone as artificial reservoir, decorate a injection Wells and production Wells with technical solutions,so get a artificial reservoir volume3x1011m3, it is360times than artificial reservoir of Cornwall British for HDR Geothemal mining. This plan, a set of geothermal extraction, can build a system of10million kilowatts, power station for100 years. HDR geothermal resources of5.4×108MKW.a of Yangbajing region is China’s huge HDR geothermal resources temperature.更多还原