【作者】 李建宇；

【导师】 李宏；

【作者基本信息】 大连理工大学 ， 建筑与土木工程（专业学位）， 2021， 硕士

【摘要】 干热岩(HDR)地热能的开发利用,正引起人们的广泛关注。由于其赋存于致密、少裂隙的高温岩体中,以井工法开发深部地热能,是近年来人们探索突破增强型地热系统商业化瓶颈的出路之一。本文针对基于开挖技术的增强型地热系统(EGS-E),通过文献调研、数值模拟(FLAC3D)和理论分析的方法,初步地定量研究了作为EGS-E基元构件的巷道,在开挖和通风降温过程中围岩破裂区的分布特征,模拟分析了巷道致裂区力学、传热行为。主要研究内容与结论如下:(1)通过文献综述,探讨了造成高温岩石物理力学性质变化的微观机制与演化规律,为小于300℃的高温岩体数值模拟提供了一套来自试验基础的高温特性参数。经过文献调研发现该温度范围内的深地高温岩石,仍属于典型的脆硬岩石,需要通过依赖温度修正的力学参数来模拟高温花岗岩的力学行为。(2)基于粘聚力弱化-摩擦增强(CWFS)模型,揭示了在卸荷作用下代表围岩开挖扰动区(EDZs)的塑性屈服应变的分布与变化规律,探讨了深地初始地应力接近静水压力条件下围岩的破裂区形貌,为量化高温条件下开挖扰动引起的破裂损伤区尺度做出了基本尝试。巷道开挖的力学、渗透和传热行为研究为后续在高温岩体中人工建造热储打下基础,为深地工程施工安全探讨基础依据。通过热-力耦合模拟,分析了随着巷道通风降温进程围岩应力与开挖扰动损伤破裂区的演化规律。模拟结果表明:高温高地应力巷道通风降温,对围岩损伤破裂区尺度产生显著影响;围岩近场产生额外拉应力,压应力集中向远场转移;随着降温时间的增加,EDZs的扩展经历了缓慢、快速、减速三个阶段;安装隔热衬垫层,将明显延长缓慢增长阶段的时间。(3)考虑到利用沸腾传热和工质流体自然对流两种传热方式,对开挖扰动裂隙岩体的传输热机制研究具有重要意义,本文通过塑性体积应变关联公式,结合数值模拟分析成果,初步地定量表征开挖导致围岩损伤破裂区的渗透率非线性分布,基于自然对流和沸腾蒸发的思路简化其传热过程,探讨了巷道开挖扰动致裂区传热行为的简便计算方法。结果表明,相较于岩体裂隙中填充流体发生自然对流,利用沸腾传热开发干热岩可获得更高的采热效率。更多还原

【Abstract】 The development and utilization of hot dry rock(HDR)geothermal energy is attracting widespread attention.Because it stores in dense,high-temperature deep rock masses lacking fractures,mining deep thermal ore energy by the well construction method is one of the ways people have explored to break through the bottleneck of the commercialization of enhanced geothermal systems in recent years.Aiming at the innovative Enhanced Geothermal System based on Excavation Technology(EGS-E),this thesis has conducted a preliminary quantitative study of the tunnel as a basic element of EGS-E,including the distribution characteristics of the surrounding rock fracture zone during excavation,ventilation and cooling,also the simulation analysis of the mechanics and heat transfer behavior of the tunnel fracture zone through literature research,numerical simulation(FLAC3D)and theoretical analysis methods.The main research contents and conclusions are as follows:(1)Through literature review,the micro-mechanism and evolution law of the changes in the physical and mechanical properties of high-temperature rocks are discussed,and a set of high-temperature characteristic parameters derived from the experimental foundation are provided for the numerical simulation of high temperature rock mass less than 300℃.Through literature research,it is found that the deep-ground high-temperature rocks within this temperature range are still typical brittle and hard rocks,and the behavior of deep-ground granites needs to be simulated by mechanical parameters modified by temperature.(2)Based on CWFS model,the distribution and change of plastic yield strain representing the surrounding rock excavation disturbance zone(EDZs)under unloading are revealed,the failure patterns of surrounding rock under the condition that the initial deep ground stress is close to hydrostatic pressure are discussed.A basic attempt was made to quantify the scale of the fracture damage zone caused by excavation disturbance under high temperature conditions.The study on the mechanics,permeability and heat transfer behavior of tunnel excavation provides the foundation for the subsequent artificial construction of heat storage in hightemperature rock masses and is the basis for the safety discussion of deep engineering construction.Through thermal-mechanical coupling simulation,analyzed the surrounding rock stress and the evolution law of excavation disturbance damage rupture zone as the process of tunnel ventilation and cooling is analyzed.The results show that the ventilation cooling of high temperature and high in-situ stress tunnel have a significant effect on the EDZS scale.Additional tensile stress is generated in the shallow of tunnel surrounding rock,and the compressive stress concentration transfers to the far field.EDZs experiences three stages of slow,rapid and deceleration with cooling time,and the installation of a thermal insulation liner will significantly extend the time of the slow growth phase.(3)Considering the use of boiling heat transfer and natural convection of the working fluid,two heat transfer mechanisms are of great significance to the regulation of heat recovery in rock mass fractures caused by excavation,drilling and blasting.Though the use of plastic volume strain correlation formula,combined with the results of numerical simulation analysis,this paper preliminarily characterizes the non-linear distribution of permeability in the damage and fracture zone of surrounding rock caused by excavation.Based on the ideas of natural convection and boiling evaporation,the heat transfer process is simplified,and a simple calculation method for the heat transfer behavior in the fracture zone caused by the excavation disturbance of the primitive tunnel is discussed.The results show that compared with the natural convection of the fluid filled in the cracks of the rock mass,the use of boiling heat transfer to develop the dry hot rock can obtain higher heat recovery efficiency.更多还原