【作者】 阎岩；

【导师】 王思敬；

【作者基本信息】 清华大学 ， 水利工程， 2009， 博士

【摘要】 许多大型水利工程的服务年限一般长达几十年甚至上百年,因此在工程设计与施工中必须确保其长期运营过程中的安全。许多工程实例表明,岩石蠕变往往是地下洞室、基础、边坡等产生大变形乃至失稳的重要原因。近年来,在国内的一些水利工程中发现,岩石在渗流作用下的蠕变特性更加明显,为工程的长期稳定带来了诸多不利影响。然而,目前在岩石蠕变研究领域尚未对渗流作用下岩石的蠕变展开系统研究,在试验设备的研制、试验方法的改进与理论的发展等方面都存在进一步完善的必要性与紧迫性。因此,本文针对渗流作用下岩石的蠕变特性展开试验研究与理论分析,为岩石工程的长期稳定性问题提供新的研究思路与研究方法。本文以试验作为主线,试验研究、理论分析和数值模拟相结合。首先通过对现有试验设备的改进与完善,建立了岩石渗流与蠕变耦合的试验系统与试验方法。以多孔隙石灰岩为对象,按照两种试验方案进行了5组岩石渗流-蠕变耦合试验,并基于试验结果探讨了岩石在渗流作用下的蠕变特性,主要包括应力及渗流对岩样蠕变的影响、岩样的体积蠕变与渗透系数及其二者之间的关系、岩样的蠕变速率与蠕变泊松比等。现有的三维蠕变方程在推导过程中采用了与试验现象相矛盾的假设,因此不能真实反映岩石蠕变的非线性特征。文中提出了变参数方法对其进行改进,通过蠕变参数的非线性变化来反映蠕变全过程的非线性特征。由耦合试验结果,用非线性最小二乘法求出了不同应力、不同渗透水压作用下不同时刻的蠕变参数,并根据参数的分布规律得到了蠕变参数与应力、时间、渗透水压的关系,最后得到变参数的三维非线性蠕变方程。通过对不同种类岩石已有试验成果的分析,初步验证了本文所得到的蠕变参数变化规律具有一定的适用性。利用渗流计算程序GeoSeepage和商业软件FLAC3D实现了考虑渗流作用及参数变化的蠕变数值化计算,对溪洛渡左岸地下厂房洞室的蠕变进行了数值模拟,探讨了渗流作用下洞室围岩的长期稳定性。更多还原

【Abstract】 Many hydraulic projects would serve decades or hundred years, therefore the design and construction of such project must insure its safety during a long service time. Some engineer practice has proved that the creep of rock often plays an important role in the deformation or failure of underground cavern, basement and slope. Recently, rock mass in some domestic hydraulic projects were found to show its creep properties more obviously under seepage flow, which bring some disadvantage influence to the long term stability of project. However, the issue of rock creep under seepage flow has not been studied thoroughly, it’s necessary and urgent to improve on test equipment, method and creep theory. So, several rock seepage-creep coupling tests and theory research work have been accomplished in this paper to provide new research idea and method to long term stability problem of rock engineering.Experiments are taken as foundation of whole research work in this paper, the theory and numeric simulation of rock creep are developed base on test results. Firstly, an effectual experiment system and method of rock seepage-creep coupling test are developed by the improvement of existing equipments. 5 coupling tests have been done by 2 test schemes using porous limestone as specimen. Main rock creep properties under seepage flow are investigated by test results, including the influence of stress and seepage on rock creep, volume creep and permeability coefficient of rock and their relation, creep rate and creep Poisson’s ratio etc.The existing three-dimensional creep equation can not truly reflect the nonlinear character of rock creep due to the adoption of some hypothesis in deduction which conflict with rock creep phenomenon. The variable parameters method is proposed in this paper to improve creep theory, the nonlinear character of entire creep process could be reflected by the nonlinear change of creep parameters. Based on rock seepage-creep coupling test results, each creep parameter at different time under different stress and seepage pressure is figured out by nonlinear least square method, then the expressions of creep parameters vary with stress, time and seepage pressure are put forward by nonlinear curve fitting of creep parameters’distribution, finally form three-dimensional creep equation with variable parameters. The variation rule of creep parameters has been proved to be certain applicable by the analysis of existing creep test results of different rock.The numerical simulation of creep with variable parameters under seepage flow could be achieved through seepage calculation program GeoSeepage and FLAC3D. As an elucidation, the creep of left bank underground cavern of Xiluodu hydropower station is simulated to discuss the long term stability of cavern surrounding rock under seepage flow.更多还原